Dynamical Stability and Evolution of Kepler’s compact inner multi-planet systems

NASA Astrophysics Data System (ADS)

Pu, Bonan

2017-06-01

NASA’s Kepler mission has revealed a population of highly compact inner multi-planet systems. These systems, typically consisting of 4-6 super-Earths, feature tight orbital spacing between planets as well as low orbital inclinations (~2 deg. ) and eccentricities (~2%). This stands in contrast to Kepler’s singles population, which appears to feature higher orbital obliquities and eccentricities, as well as a lower transit timing variation fraction indicative of lower true planet multiplicities.In this talk, I will present some previous and ongoing research aimed at understanding the dynamical evolution of these Kepler systems. First, I will present numerical N-body investigations on the long-term stability of multi-planet systems, the results of which suggest that Kepler’s systems are near the edge of stability. Next, I will discuss some current research on the dynamics of planetary close encounters and collisions, and their implications for the ultimate fate of dynamically unstable multi-planet systems. Finally, I will highlight some recent results on the dynamical stability and evolution of inner multi-planet systems when they are accompanied by external giant planet and/or stellar companions.

Dynamics of exoplanetary systems, links to their habitability

NASA Astrophysics Data System (ADS)

Bolmont, E.; Raymond, S. N.; Selsis, F.

2014-12-01

Our knowledge of planets' orbital dynamics, which was based on Solar System studies, has been challenged by the diversity of exoplanetary systems. Around cool and ultra cool dwarfs, the influence of tides on the orbital and spin evolution of planets can strongly affect their climate and their capacity to host surface liquid water. We illustrate the role of tides and dynamics with the extreme case of planets orbiting around brown dwarfs. In multiple planet systems, the eccentricity is excited by planet-planet interactions. Planets are therefore heated up from the inside by the tidally-induced friction. This process can heat a habitable zone planet to such a level that surface liquid water cannot exist. We also talk about the newly discovered potentially habitable Earth-sized planet Kepler-186f. Given the poorly estimated age of the system, the planet could still be evolving towards synchronization and have a high obliquity or be pseudo-synchronized with a zero obliquity. These two configurations would have a different effect on the climate of this planet.

ScienceCast 136: A Sudden Multiplication of Planets

NASA Image and Video Library

2014-02-26

Today, NASA announced a breakthrough addition to the catalog of new planets. Researchers using Kepler have confirmed 715 new worlds, almost quadrupling the number of planets previously confirmed by the planet-hunting spacecraft.

An estimate of the prevalence of biocompatible and habitable planets.

PubMed

Fogg, M J

1992-01-01

A Monte Carlo computer model of extra-solar planetary formation and evolution, which includes the planetary geochemical carbon cycle, is presented. The results of a run of one million galactic disc stars are shown where the aim was to assess the possible abundance of both biocompatible and habitable planets. (Biocompatible planets are defined as worlds where the long-term presence of surface liquid water provides environmental conditions suitable for the origin and evolution of life. Habitable planets are those worlds with more specifically Earthlike conditions). The model gives an estimate of 1 biocompatible planet per 39 stars, with the subset of habitable planets being much rarer at 1 such planet per 413 stars. The nearest biocompatible planet may thus lie approximately 14 LY distant and the nearest habitable planet approximately 31 LY away. If planets form in multiple star systems then the above planet/star ratios may be more than doubled. By applying the results to stars in the solar neighbourhood, it is possible to identify 28 stars at distances of < 22 LY with a non-zero probability of possessing a biocompatible planet.

Habitability in the Solar System and on Extrasolar Planets and Moons

NASA Technical Reports Server (NTRS)

McKay, Christopher P.

2015-01-01

The criteria for a habitable world initially was based on Earth and centered around liquid water on the surface, warmed by a Sun-like star. The moons of the outer Solar System, principally Europa and Enceladus, have demonstrated that liquid water can exist below the surface warmed by tidal forces from a giant planet. Titan demonstrates that surface liquids other than water - liquid methane/ethane - may be common on other worlds. Considering the numerous extrasolar planets so far discovered and the prospect of discovering extrasolar moons it is timely to reconsider the possibilities for habitability in the Solar System and on extrasolar planets and moons and enumerate the attributes and search methods for detecting habitable worlds and evidence of life.

Habitability in The Solar System and on Extrasolar Planets and Moons

NASA Astrophysics Data System (ADS)

McKay, C. P.

2015-12-01

The criteria for a habitable world initially was based on Earth and centered around liquid water on the surface, warmed by a Sun-like star. The moons of the outer Solar System, principally Europa and Enceladus, have demonstrated that liquid water can exist below the surface warmed by tidal forces from a giant planet. Titan demonstrates that surface liquids other than water - liquid methane/ethane - may be common on other worlds. Considering the numerous extrasolar planets so far discovered and the prospect of discovering extrasolar moons it is timely to reconsider the possibilities for habitable environments in the Solar System and on extrasolar planets and moons and enumerate the attributes and search methods for detecting habitable worlds and evidence of life.

Habitable worlds with no signs of life

PubMed Central

Cockell, Charles S.

2014-01-01

‘Most habitable worlds in the cosmos will have no remotely detectable signs of life’ is proposed as a biological hypothesis to be tested in the study of exoplanets. Habitable planets could be discovered elsewhere in the Universe, yet there are many hypothetical scenarios whereby the search for life on them could yield negative results. Scenarios for habitable worlds with no remotely detectable signatures of life include: planets that are habitable, but have no biosphere (Uninhabited Habitable Worlds); planets with life, but lacking any detectable surface signatures of that life (laboratory examples are provided); and planets with life, where the concentrations of atmospheric gases produced or removed by biota are impossible to disentangle from abiotic processes because of the lack of detailed knowledge of planetary conditions (the ‘problem of exoplanet thermodynamic uncertainty’). A rejection of the hypothesis would require that the origin of life usually occurs on habitable planets, that spectrally detectable pigments and/or metabolisms that produce unequivocal biosignature gases (e.g. oxygenic photosynthesis) usually evolve and that the organisms that harbour them usually achieve a sufficient biomass to produce biosignatures detectable to alien astronomers. PMID:24664917

Habitable worlds with no signs of life.

PubMed

Cockell, Charles S

2014-04-28

'Most habitable worlds in the cosmos will have no remotely detectable signs of life' is proposed as a biological hypothesis to be tested in the study of exoplanets. Habitable planets could be discovered elsewhere in the Universe, yet there are many hypothetical scenarios whereby the search for life on them could yield negative results. Scenarios for habitable worlds with no remotely detectable signatures of life include: planets that are habitable, but have no biosphere (Uninhabited Habitable Worlds); planets with life, but lacking any detectable surface signatures of that life (laboratory examples are provided); and planets with life, where the concentrations of atmospheric gases produced or removed by biota are impossible to disentangle from abiotic processes because of the lack of detailed knowledge of planetary conditions (the 'problem of exoplanet thermodynamic uncertainty'). A rejection of the hypothesis would require that the origin of life usually occurs on habitable planets, that spectrally detectable pigments and/or metabolisms that produce unequivocal biosignature gases (e.g. oxygenic photosynthesis) usually evolve and that the organisms that harbour them usually achieve a sufficient biomass to produce biosignatures detectable to alien astronomers.

Celestial Exoplanet Survey Occulter: A Concept for Direct Imaging of Extrasolar Earth-like Planets from the Ground

NASA Astrophysics Data System (ADS)

Janson, M.

2007-02-01

We present a new concept for detecting and characterizing extrasolar planets down to Earth size or smaller through direct imaging. The New Worlds Observer (NWO) occulter developed by Cash and coworkers is placed in a particular geometrical setup in which fuel requirements are small and the occulter is used in combination with ground-based telescopes, presumably leading to an extreme cost efficiency compared to other concepts with similar science goals. We investigate the various aspects of the given geometry, such as the dynamics and radiation environment of the occulter, and construct a detailed example target list to ensure that an excellent science case can be maintained despite the limited sky coverage. It is found that more than 200 systems can be observed with two to three visits per system, using only a few tons of fuel. For each system, an Earth-sized planet with an Earth-like albedo can be found in the habitable zone in less than 2 hr.

On habitable Trojan worlds in exoplanetary systems

NASA Astrophysics Data System (ADS)

Schwarz, Richard; Eggl, Siegfried; Akos, Bazso; Funk, Barbara

2016-09-01

When astronomers look for life on planets in exoplanetary systems (EPS), they use the concept of the habitable zone (HZ) for the search of life in the universe. In many EPS a giant planet moves in the HZ and makes the existence of another habitable planet impossible, because of the gravitational interaction with a gas giant (GG). Therefore the investigation of the Trojan configuration provides another opportunity for an additional habitable planet. The configuration is the following, when a GG (like Jupiter or larger) moves in the HZ, a terrestrial Trojan planet may move in a stable orbit around the Lagrangian equilibrium points L4 or L5. Trojans are moving either close to 60° ahead or 60° behind the GG with nearly the same semi-major axis as the planet (as shown in the figure for the circular case). Former studies (Schwarz et al. 2009 and Schwarz et al 2014) could show that this configuration is not only stable for small bodies like asteroids (e.g. Jupiter Trojans), but also for larger ones (Earth-mass). We investigate the stability of possible Trojan planets in several known extra-solar planetary systems, by using the planar 3 and N-body problem as dynamical model considering the eccentricity of the planets. For our numerical simulations we use the Lie-integration method with an automatic step-size control to solve the equations of motion (Eggl and Dvorak 2010). In our study, we have concentrated on the extension of the stability region around the Lagrangian points and the influence of additional outer or inner GG. Finally we present a list of candidates of EPS where a massive GG (3-10 Jupiter masses) moves almost or fully in the HZ and an additional possible Trojan planet can have stable motion.

Resonance capture and dynamics of three-planet systems

NASA Astrophysics Data System (ADS)

Charalambous, C.; Martí, J. G.; Beaugé, C.; Ramos, X. S.

2018-06-01

We present a series of dynamical maps for fictitious three-planet systems in initially circular coplanar orbits. These maps have unveiled a rich resonant structure involving two or three planets, as well as indicating possible migration routes from secular to double resonances or pure three-planet commensurabilities. These structures are then compared to the present-day orbital architecture of observed resonant chains. In a second part of the paper, we describe N-body simulations of type-I migration. Depending on the orbital decay time-scale, we show that three-planet systems may be trapped in different combinations of independent commensurabilities: (i) double resonances, (ii) intersection between a two-planet and a first-order three-planet resonances, and (iii) simultaneous libration in two first-order three-planet resonances. These latter outcomes are found for slow migrations, while double resonances are almost always the final outcome in high-density discs. Finally, we discuss an application to the TRAPPIST-1 system. We find that, for low migration rates and planetary masses of the order of the estimated values, most three-planet sub-systems are able to reach the observed double resonances after following evolutionary routes defined by pure three-planet resonances. The final orbital configuration shows resonance offsets comparable with present-day values without the need of tidal dissipation. For the 8/5 resonance proposed to dominate the dynamics of the two inner planets, we find little evidence of its dynamical significance; instead, we propose that this relation between mean motions could be a consequence of the interaction between a pure three-planet resonance and a two-planet commensurability between planets c and d.

The effects of external planets on inner systems: multiplicities, inclinations and pathways to eccentric warm Jupiters

NASA Astrophysics Data System (ADS)

Mustill, Alexander J.; Davies, Melvyn B.; Johansen, Anders

2017-07-01

We study how close-in systems such as those detected by Kepler are affected by the dynamics of bodies in the outer system. We consider two scenarios: outer systems of giant planets potentially unstable to planet-planet scattering and wide binaries that may be capable of driving Kozai or other secular variations of outer planets' eccentricities. Dynamical excitation of planets in the outer system reduces the multiplicity of Kepler-detectable planets in the inner system in ˜20-25 per cent of our systems. Accounting for the occurrence rates of wide-orbit planets and binary stars, ≈18 per cent of close-in systems could be destabilized by their outer companions in this way. This provides some contribution to the apparent excess of systems with a single transiting planet compared to multiple; however, it only contributes at most 25 per cent of the excess. The effects of the outer dynamics can generate systems similar to Kepler-56 (two coplanar planets significantly misaligned with the host star) and Kepler-108 (two significantly non-coplanar planets in a binary). We also identify three pathways to the formation of eccentric warm Jupiters resulting from the interaction between outer and inner systems: direct inelastic collision between an eccentric outer and an inner planet; secular eccentricity oscillations that may 'freeze out' when scattering resolves in the outer system; and scattering in the inner system followed by 'uplift', where inner planets are removed by interaction with the outer planets. In these scenarios, the formation of eccentric warm Jupiters is a signature of a past history of violent dynamics among massive planets beyond ˜1 au.

The evolutionary nature of narratives about expansion and sustenance

NASA Astrophysics Data System (ADS)

Raupach, M. R.

2014-12-01

The 200 years since the start of the industrial era has been a period of rapid and almost unbroken economic growth in much of the world, based upon exponentially increasing use of energy and water resources and the atmospheric commons. It is axiomatic that exponential growth cannot continue forever on a finite planet, leading to an emerging collision between the presently irresistible force of economic growth and the immovable reality of the finitude of Planet Earth. This has led to the a contest between two broad narratives about humans and their planet in the 21st century, an "expansion" narrative framed around the paramount need for economic growth, and a "sustenance" narrative framed around the paramount need to protect an increasingly fragile natural world. Many features of recent public discourse, including the acceleration of the news cycle and the echo-chamber effect of interactive social media, have driven these narratives to become progressively more mutually antagonistic and incompatible. Here I explore the idea that narratives (in the sense of stories that empower actions) are meme sequences that evolve through diversification, selection and adaptation. This memetic evolution can be understood and, to some extent, influenced. An analogy might be with the influence exerted by human selection over centuries on the gene pool of domesticated animals and plants. In shaping our shared future, the evolutionary contest between "expansion" and "sustenance" narratives is just as important as the dynamics of the natural world. The future therefore depends upon the evolution of more subtle and resilient narratives about human-earth interactions. A selection test for these narratives is their ability to empower a transition to a society that lives within the means of a finite planet and improves global wellbeing at the same time. My own recent experience is that scientists alone are not very good at shaping narratives to pass this fitness test, and the participation of other disciplines and approaches is urgently needed.

Extrasolar binary planets. I. Formation by tidal capture during planet-planet scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ochiai, H.; Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp

2014-08-01

We have investigated (1) the formation of gravitationally bounded pairs of gas-giant planets (which we call 'binary planets') from capturing each other through planet-planet dynamical tide during their close encounters and (2) the subsequent long-term orbital evolution due to planet-planet and planet-star quasi-static tides. For the initial evolution in phase 1, we carried out N-body simulations of the systems consisting of three Jupiter-mass planets taking into account the dynamical tide. The formation rate of the binary planets is as much as 10% of the systems that undergo orbital crossing, and this fraction is almost independent of the initial stellarcentric semimajormore » axes of the planets, while ejection and merging rates sensitively depend on the semimajor axes. As a result of circularization by the planet-planet dynamical tide, typical binary separations are a few times the sum of the physical radii of the planets. After the orbital circularization, the evolution of the binary system is governed by long-term quasi-static tide. We analytically calculated the quasi-static tidal evolution in phase 2. The binary planets first enter the spin-orbit synchronous state by the planet-planet tide. The planet-star tide removes angular momentum of the binary motion, eventually resulting in a collision between the planets. However, we found that the binary planets survive the tidal decay for the main-sequence lifetime of solar-type stars (∼10 Gyr), if the binary planets are beyond ∼0.3 AU from the central stars. These results suggest that the binary planets can be detected by transit observations at ≳ 0.3 AU.« less

The Possibility of Multiple Habitable Worlds Orbiting Binary Stars

NASA Astrophysics Data System (ADS)

Mason, P. A.

2014-03-01

Are there planetary systems for which there is life on multiple worlds? Where are these fruitful planetary systems and how do we detect them? In order to address these questions; conditions which enable life and those that prevent or destroy it must be considered. Many constraints are specific to planetary systems, independent of the number of worlds in habitable zones. For instance, life on rocky planets or moons likely requires the right abundance of volatiles and radiogenic elements for prolonged geologic activity. Catastrophic sterilization events such as nearby supernovae and gamma-ray bursts affect entire planetary systems not just specific worlds. Giant planets may either enhance or disrupt the development of complex life within a given system. It might be rare for planetary systems to possess qualities that promote life and lucky enough to avoid cataclysm. However, multiple habitable planets may provide enhanced chances for advanced life to develop. The best predictor of life on one habitable zone planet might be the presence of life on its neighbor as panspermia may occur in planetary systems with several habitable worlds. Circumbinary habitability may go hand in hand with habitability of multiple worlds. The circumstances in which the Binary Habitability Mechanism (BHM) operates are reviewed. In some cases, the early synchronization of the primary's rotation with the binary period results in a reduction of XUV flux and stellar winds. Main sequence binaries with periods in the 10-50 days provide excellent habitable environments, within which multiple worlds may thrive. Planets and moons in these habitable zones need less magnetic protection than their single star counterparts. Exomoons orbiting a Neptune-like planet, within a BHM protected habitable zone, are expected to be habitable over a wide range of semimajor axes due to a larger planetary Hill radius. A result confirmed by numerical orbital calculations. Binaries containing a solar type star with a lower mass companion provide enhanced habitable zones as well as improved photosynthetic flux for habitable zone worlds.

Loners, Groupies, and Long-term Eccentricity (and Inclination) Behavior: Insights from Secular Theory

NASA Astrophysics Data System (ADS)

Van Laerhoven, Christa L.

2015-05-01

Considering the secular dynamics of multi-planet systems provides substantial insight into the interactions between planets in those systems. Secular interactions are those that don't involve knowing where a planet is along its orbit, and they dominate when planets are not involved in mean motion resonances. These interactions exchange angular momentum among the planets, evolving their eccentricities and inclinations. To second order in the planets' eccentricities and inclinations, the eccentricity and inclination perturbations are decoupled. Given the right variable choice, the relevant differential equations are linear and thus the eccentricity and inclination behaviors can be described as a sum of eigenmodes. Since the underlying structure of the secular eigenmodes can be calculated using only the planets' masses and semi-major axes, one can elucidate the eccentricity and inclination behavior of planets in exoplanet systems even without knowing the planets' current eccentricities and inclinations. I have calculated both the eccentricity and inclination secular eigenmodes for the population of known multi-planet systems whose planets have well determined masses and periods. Using this catalog of secular character, I will discuss the prevalence of dynamically grouped planets ('groupies') versus dynamically uncoupled planets ('loners') and how this relates to the exoplanets' long-term eccentricity and inclination behavior. I will also touch on the distribution of the secular eigenfreqiencies.

Exoplanet habitability.

PubMed

Seager, Sara

2013-05-03

The search for exoplanets includes the promise to eventually find and identify habitable worlds. The thousands of known exoplanets and planet candidates are extremely diverse in terms of their masses or sizes, orbits, and host star type. The diversity extends to new kinds of planets, which are very common yet have no solar system counterparts. Even with the requirement that a planet's surface temperature must be compatible with liquid water (because all life on Earth requires liquid water), a new emerging view is that planets very different from Earth may have the right conditions for life. The broadened possibilities will increase the future chances of discovering an inhabited world.

A Study of Planet Three: A World Geography/Social Studies Course.

ERIC Educational Resources Information Center

Graham, Duncan

This 12th grade course in world geography is based on the philosophical assumption that human beings on earth make up a global village of interdependent people. It is world geography with a planetary perspective--an inquiry into the nature of the planet and its dominant species, Homo Sapiens. Seven units cover the following topics on physical and…

Laboratory Simulations of Ammonia-Rich Oceans in Icy Worlds

NASA Technical Reports Server (NTRS)

Vance, S. D.; Brown, J. M.

2011-01-01

Improved equations of state for ammonia-water solutions are important for properly understanding the interiors of large icy satellites hosting deep interior oceans. Titan is the primary example of such a world, but water-rich dwarf planets Measurements of solution density are now possible at relevant pressures (above approx. 250 megapascals) using the Simulator for Icy World Interiors. Analysis of sound velocity measurements in aqueous magnesium sulfate obtained in our laboratory, shows a correction on the order of 5% to 700 megapascals (7 kilobar) from -20 to 100 C and to 3 m (approx. 30 percentage by weight) concentration. Accurate prediction of density as a function of pressure, temperature, and ammonia concentration are needed for interpretation of remote observations to address questions of interior liquid layer depth, composition, and fluid dynamics.

Title: Characterizing a Frozen Extrasolar World

NASA Technical Reports Server (NTRS)

Skemer, Andrew J.; Morley, Caroline V.; Allers, Katelyn N.; Geballe, Thomas R.; Marley, Mark S.; Fortney, Jonathan J.; Faherty, Jacqueline K.; Bjoraker, Gordon L.

2016-01-01

The recently discovered brown dwarf WISE 0855 presents our first opportunity to study an object outside the Solar System that is nearly as cold as our own gas giant planets. However the traditional methodology for characterizing brown dwarfs-near infrared spectroscopy-is not currently feasible as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5-5.2 micrometers spectrum, the same bandpass long used to study Jupiter's deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter. The spectrum is high enough quality to allow the investigation of dynamical and chemical processes that have long been studied in Jupiter's atmosphere, but this time on an extrasolar world.

Glimpses of far away places: Intensive atmosphere characterization of extrasolar planets

NASA Astrophysics Data System (ADS)

Kreidberg, Laura

Exoplanet atmosphere characterization has the potential to reveal the origins, nature, and even habitability of distant worlds. This thesis represents a step towards realizing that potential for a diverse group of four extrasolar planets. Here, I present the results of intensive observational campaigns with the Hubble and Spitzer Space Telescopes to study the atmospheres of the super-Earth GJ 1214b and the hot Jupiters WASP-43b, WASP-12b, and WASP-103b. I measured an unprecedentedly precise near-infrared transmission spectrum for GJ 1214b that definitively reveals the presence of clouds in the planet's atmosphere. For WASP-43b and WASP-12b, I also measured very precise spectra that exhibit water features at high confidence (>7 sigma). The retrieved water abundance for WASP-43b extends the well-known Solar System trend of decreasing atmospheric metallicity with increasing planet mass. The detection of water for WASP-12b marks the first spectroscopic identification of a molecule in the planet's atmosphere and implies that it has solar composition, ruling out carbon-to-oxygen ratios greater than unity. For WASP-103b, I present preliminary results from the new technique of phase-resolved spectroscopy to determine the planet's temperature structure, dynamics, and energy budget. In addition to these observations, I also describe the BATMAN code, an open-source Python package for fast and flexible modeling of transit light curves. Taken together, these results provide a foundation for comparative planetology beyond the Solar System and the investigation of Earth-like, potentially habitable planets with future observing facilities.

Directly Imaged Giant Planets: What Do We Hope to Learn?

NASA Technical Reports Server (NTRS)

Marley, Mark

2015-01-01

As we move into an era when GPI and SPHERE are (hopefully) discovering and characterizing new young giant planets, it is worthwhile to step back and review our science goals for young giant planets. Of course for individual planets we ideally would hope to measure mass, radius, atmospheric composition, temperature, and cloud properties, but how do these characteristics fit into our broader understanding of planetary system origin and evolution theories? In my presentation I will review both the specifics of what we hope to learn from newly discovered young worlds as well as how these characteristics inform our broader understanding of giant planets and planetary systems. Finally I will consider the limitations realistic datasets will place on our ability to understand newly discovered planets, illustrating with data from any new such worlds that are available by the conference date.

Early 2017 observations of TRAPPIST-1 with Spitzer

NASA Astrophysics Data System (ADS)

Delrez, L.; Gillon, M.; Triaud, A. H. M. J.; Demory, B.-O.; de Wit, J.; Ingalls, J. G.; Agol, E.; Bolmont, E.; Burdanov, A.; Burgasser, A. J.; Carey, S. J.; Jehin, E.; Leconte, J.; Lederer, S.; Queloz, D.; Selsis, F.; Van Grootel, V.

2018-04-01

The recently detected TRAPPIST-1 planetary system, with its seven planets transiting a nearby ultracool dwarf star, offers the first opportunity to perform comparative exoplanetology of temperate Earth-sized worlds. To further advance our understanding of these planets' compositions, energy budgets, and dynamics, we are carrying out an intensive photometric monitoring campaign of their transits with the Spitzer Space Telescope. In this context, we present 60 new transits of the TRAPPIST-1 planets observed with Spitzer/Infrared Array Camera (IRAC) in 2017 February and March. We combine these observations with previously published Spitzer transit photometry and perform a global analysis of the resulting extensive data set. This analysis refines the transit parameters and provides revised values for the planets' physical parameters, notably their radii, using updated properties for the star. As part of our study, we also measure precise transit timings that will be used in a companion paper to refine the planets' masses and compositions using the transit timing variations method. TRAPPIST-1 shows a very low level of low-frequency variability in the IRAC 4.5-μm band, with a photometric RMS of only 0.11 per cent at a 123-s cadence. We do not detect any evidence of a (quasi-)periodic signal related to stellar rotation. We also analyse the transit light curves individually, to search for possible variations in the transit parameters of each planet due to stellar variability, and find that the Spitzer transits of the planets are mostly immune to the effects of stellar variations. These results are encouraging for forthcoming transmission spectroscopy observations of the TRAPPIST-1 planets with the James Webb Space Telescope.

The Late-Time Formation and Dynamical Signatures of Small Planets

NASA Astrophysics Data System (ADS)

Lee, Eve Jihyun

The riddle posed by super-Earths is that they are not Jupiters: their core masses are large enough to trigger runaway gas accretion, yet somehow super-Earths accreted atmospheres that weigh only a few percent of their total mass. In this thesis, I demonstrate that this puzzle is solved if super-Earths formed late, in the inner cavities of transitional disks. Super-puffs present the inverse problem of being too voluminous for their small masses. I show that super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside 1 AU, and then migrate in just after super-Earths appear. Super-Earths and Earth-sized planets around FGKM dwarfs are evenly distributed in log orbital period down to 10 days, but dwindle in number at shorter periods. I demonstrate that both the break at 10 days and the slope of the occurrence rate down to 1 day can be reproduced if planets form in disks that are truncated by their host star magnetospheres at co-rotation. Planets can be brought from disk edges to ultra-short (<1 day) periods by asynchronous equilibrium tides raised on their stars. Small planets may remain ubiquitous out to large orbital distances. I demonstrate that the variety of debris disk morphologies revealed by scattered light images can be explained by viewing an eccentric disk, secularly forced by a planet of just a few Earth masses, from different observing angles. The farthest reaches of planetary systems may be perturbed by eccentric super-Earths.

Habitable Planets with Dynamic System of Global Air-Liquid-Solid Planet and Life

NASA Astrophysics Data System (ADS)

Miura, Y.; Kato, T.

2017-11-01

Habitable zone is dynamic three phase states (air-liquid-solid), which will be obtained in water-planet with volatile exchanges. Water and carbon-bearing grains at older extraterrestrial stones suggest that there are no global ocean water system.

Effects of Variable Eccentricity on the Climate of an Earth-Like World

NASA Technical Reports Server (NTRS)

Way, M. J.; Georgakarakos, Nikolaos

2017-01-01

The Kepler era of exoplanetary discovery has presented the Astronomical community with a cornucopia of planetary systems very different from the one which we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and its climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for its large moon. Using a three dimensional general circulation model (3-D GCM) with a fully-coupled ocean we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earths orbit. We investigate two scenarios that involve evolution of the Earth-like planets orbital eccentricity from 0 to 0.066 on a time scale of 4500 years, and from 0 to 0.283 over 6500 years. We discover that during most of the 6500 year scenario the planet would experience a moist greenhouse effect when near periastron. This could have implications for the ability of such a world to retain an ocean on time scales of 109 years. More Earth-like planets in multi-planet systems will be discovered as we continue to survey the skies and the results herein show that the proximity of large gas giant planets may play an important role in the habitabilty of these worlds. These are the first such 3-D GCM simulations using a fully-coupled ocean with a planetary orbit that evolves over time due to the presence of a giant planet.

The Solar Connections Observatory for Planetary Environments

NASA Technical Reports Server (NTRS)

Oliversen, Ronald J.; Harris, Walter M.; Oegerle, William R. (Technical Monitor)

2002-01-01

The NASA Sun-Earth Connection theme roadmap calls for comparative study of how the planets, comets, and local interstellar medium (LISM) interact with the Sun and respond to solar variability. Through such a study we advance our understanding of basic physical plasma and gas dynamic processes, thus increasing our predictive capabilities for the terrestrial, planetary, and interplanetary environments where future remote and human exploration will occur. Because the other planets have lacked study initiatives comparable to the terrestrial ITM, LWS, and EOS programs, our understanding of the upper atmospheres and near space environments on these worlds is far less detailed than our knowledge of the Earth. To close this gap we propose a mission to study {\\it all) of the solar interacting bodies in our planetary system out to the heliopause with a single remote sensing space observatory, the Solar Connections Observatory for Planetary Environments (SCOPE). SCOPE consists of a binocular EUV/FUV telescope operating from a remote, driftaway orbit that provides sub-arcsecond imaging and broadband medium resolution spectro-imaging over the 55-290 nm bandpass, and high (R>10$^{5}$ resolution H Ly-$\\alpha$ emission line profile measurements of small scale planetary and wide field diffuse solar system structures. A key to the SCOPE approach is to include Earth as a primary science target. From its remote vantage point SCOPE will be able to observe auroral emission to and beyond the rotational pole. The other planets and comets will be monitored in long duration campaigns centered when possible on solar opposition when interleaved terrestrial-planet observations can be used to directly compare the response of both worlds to the same solar wind stream and UV radiation field. Using a combination of observations and MHD models, SCOPE will isolate the different controlling parameters in each planet system and gain insight into the underlying physical processes that define the solar connection.

Exotic Earths: forming habitable worlds with giant planet migration.

PubMed

Raymond, Sean N; Mandell, Avi M; Sigurdsson, Steinn

2006-09-08

Close-in giant planets (e.g., "hot Jupiters") are thought to form far from their host stars and migrate inward, through the terrestrial planet zone, via torques with a massive gaseous disk. Here we simulate terrestrial planet growth during and after giant planet migration. Several-Earth-mass planets also form interior to the migrating jovian planet, analogous to recently discovered "hot Earths." Very-water-rich, Earth-mass planets form from surviving material outside the giant planet's orbit, often in the habitable zone and with low orbital eccentricities. More than a third of the known systems of giant planets may harbor Earth-like planets.

The Solar Connections Observatory for Planetary Environments

NASA Astrophysics Data System (ADS)

Oliversen, R. J.; Harris, W. M.

2002-05-01

The NASA Sun-Earth Connection theme roadmap calls for comparative studies of planetary, cometary, and local interstellar medium (LISM) interaction with the Sun and solar variability. Through such studies, we advance our understanding of basic physical plasma and gas dynamic processes, thus increasing our predictive capabilities for the terrestrial, planetary, and interplanetary environments where future remote and human exploration will occur. Because the other planets have lacked study initiatives comparable to the STP, LWS, and EOS programs, our understanding of the upper atmospheres and near space environments on these worlds is far less detailed than our knowledge of the Earth. To close this gap, we propose a mission to study the solar interaction with bodies throughout our solar system and the heliopause with a single remote sensing space observatory, the Solar Connections Observatory for Planetary Environments (SCOPE). SCOPE consists of a binocular EUV/UV telescope operating from a heliocentric, Earth-trailing orbit that provides high observing efficiency, sub-arcsecond imaging and broadband medium resolution spectro-imaging over the 55-290 nm bandpass, and high resolution (R>105) H Ly-α emission line profile measurements of small scale planetary and wide field diffuse solar system structures. A key to the SCOPE approach is to include Earth as a primary science target. The other planets and comets will be monitored in long duration campaigns centered, when possible, on solar opposition when interleaved terrestrial-planet observations can be used to directly compare the response of both worlds to the same solar wind stream and UV radiation field. Using the combination of SCOPE observations and models including MHD, general circulation, and radiative transfer, we will isolate the different controlling parameters in each planet system and gain insight into the underlying physical processes that define the solar connection.

TRAPPIST-1 Planets - Flyaround Animation

NASA Image and Video Library

2017-02-22

This frame from a video depicts artist concepts of each of the seven planets orbiting TRAPPIST-1, an ultra-cool dwarf stars. Over 21 days, NASA's Spitzer Space Telescope measured the drop in light as each planet passed in front of the star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where life is possible. The study established the planets' size, distance from their sun and, for some of them, their approximate mass and density. It also established that some, if not all, these planets are tidally locked, meaning one face of the planet permanently faces their sun. The planets appear in the order of innermost to outermost planets. These artist's concepts were designed as follows: TRAPPIST-1b, closest to the star, was modeled on Jupiter's moon Io, which has volcanic features due to strong gravitational tugs. TRAPPIST-1c is shown as a rocky, warm world with a small ice cap on the side that never faces the star. TRAPPSIT-1d is rocky and has water only in a thin band along the terminator, dividing the day side and night side. TRAPPIST-1e and TRAPPIST-1f are both shown covered in water, but with progressively larger ice caps on the night side. TRAPPIST-1g is portrayed with an atmosphere like Neptune's, although it is still a rocky world. The farthest planet, TRAPPIST-1h, is shown as covered in ice, similar to Jupiter's icy moon Europa. The background stars are what you would see if you were in the TRAPPIST-1 system. Orion passes behind the planets, recognizable but distorted from what we're familiar with, in addition to Taurus and Pleiades. A video is available at http://photojournal.jpl.nasa.gov/catalog/PIA21468

Groupies and Loners: The Population of Multi-planet Systems

NASA Astrophysics Data System (ADS)

Van Laerhoven, Christa L.; Greenberg, Richard

2014-11-01

Observational surveys with Kepler and other telescopes have shown that multi-planet systems are very numerous. Considering the secular dynamcis of multi-planet systems provides substantial insight into the interactions between planets in those systems. Since the underlying secular structure of a multi-planet system (the secular eigenmodes) can be calculated using only the planets' masses and semi-major axes, one can elucidate the eccentricity and inclination behavior of planets in those systems even without knowing the planets' current eccentricities and inclinations. We have calculated both the eccentricity and inclination secular eigenmodes for the population of known multi-planet systems whose planets have well determined masses and periods. We will discuss the commonality of dynamically grouped planets ('groupies') vs dynamically uncoupled planets ('loners'), and compare to what would be expected from randomly generated systems with the same overall distribution of masses and semi-major axes. We will also discuss the occurrence of planets that strongly influence the behavior of other planets without being influenced by those others ('overlords'). Examples will be given and general trends will be discussed.

Real-Time 3D Visualization

NASA Technical Reports Server (NTRS)

1997-01-01

Butler Hine, former director of the Intelligent Mechanism Group (IMG) at Ames Research Center, and five others partnered to start Fourth Planet, Inc., a visualization company that specializes in the intuitive visual representation of dynamic, real-time data over the Internet and Intranet. Over a five-year period, the then NASA researchers performed ten robotic field missions in harsh climes to mimic the end- to-end operations of automated vehicles trekking across another world under control from Earth. The core software technology for these missions was the Virtual Environment Vehicle Interface (VEVI). Fourth Planet has released VEVI4, the fourth generation of the VEVI software, and NetVision. VEVI4 is a cutting-edge computer graphics simulation and remote control applications tool. The NetVision package allows large companies to view and analyze in virtual 3D space such things as the health or performance of their computer network or locate a trouble spot on an electric power grid. Other products are forthcoming. Fourth Planet is currently part of the NASA/Ames Technology Commercialization Center, a business incubator for start-up companies.

Constraining the primordial orbits of the terrestrial planets

NASA Astrophysics Data System (ADS)

Brasser, R.; Walsh, K. J.; Nesvorný, D.

2013-08-01

Evidence in the Solar system suggests that the giant planets underwent an epoch of radial migration that was very rapid, with an e-folding time-scale shorter than 1 Myr. It is probable that the cause of this migration was that the giant planets experienced an orbital instability that caused them to encounter each other, resulting in radial migration. A promising and heavily studied way to accomplish such a fast migration is for Jupiter to have scattered one of the ice giants outwards; this event has been called the `jumping Jupiter' scenario. Several works suggest that this dynamical instability occurred `late', long after all the planets had formed and the solar nebula had dissipated. Assuming that the terrestrial planets had already formed, then their orbits would have been affected by the migration of the giant planets as many powerful resonances would sweep through the terrestrial planet region. This raises two questions. First, what is the expected increase in dynamical excitement of the terrestrial planet orbits caused by late and very fast giant planet migration? And secondly, assuming that the migration occurred late, can we use this migration of the giant planets to obtain information on the primordial orbits of the terrestrial planets? In this work, we attempt to answer both of these questions using numerical simulations. We directly model a large number of terrestrial planet systems and their response to the smooth migration of Jupiter and Saturn, and also two jumping Jupiter simulations. We study the total dynamical excitement of the terrestrial planet system with the angular momentum deficit (AMD) value, including the way it is shared among the planets. We conclude that to reproduce the current AMD with a reasonable probability (˜20 per cent) after late rapid giant planet migration and a favourable jumping Jupiter evolution, the primordial AMD should have been lower than ˜70 per cent of the current value, but higher than 10 per cent. We find that a late giant planet migration scenario that initially had five giant planets rather than four had a higher probability of satisfying the orbital constraints of the terrestrial planets. Assuming late migration, we predict that Mars was initially on an eccentric and inclined orbit while the orbits of Mercury, Venus and Earth were more circular and coplanar. The lower primordial dynamical excitement and the peculiar partitioning between planets impose new constraints for terrestrial planet formation simulations.

Leveraging Ensemble Dynamical Properties to Prioritize Exoplanet Follow-Up Observations

NASA Astrophysics Data System (ADS)

Ballard, Sarah

2017-01-01

The number of transiting exoplanets now exceeds several thousand, enabling ensemble studies of the dynamical properties of exoplanetary systems. We require a mixture model of dynamical conditions (whether frozen in from formation or sculpted by planet-planet interactions) to recover Kepler's yield of transiting planets. Around M dwarfs, which will be predominate sites of exoplanet follow-up atmospheric study in the next decade, even a modest orbital eccentricity can sterilize a planet. I will describe efforts to link cheap observables, such as number of transiting planets and presence of transit timing variations, to eccentricity and mutual inclination in exoplanet systems. The addition of a second transiting planet, for example, halves the expected orbital eccentricity. For the vast majority of TESS targets, the light curve alone will furnish the sum total of data about the exoplanet. Extracting information about orbital properties from these light curves will help prioritize precious follow-up resources.

Superhabitable worlds.

PubMed

Heller, René; Armstrong, John

2014-01-01

To be habitable, a world (planet or moon) does not need to be located in the stellar habitable zone (HZ), and worlds in the HZ are not necessarily habitable. Here, we illustrate how tidal heating can render terrestrial or icy worlds habitable beyond the stellar HZ. Scientists have developed a language that neglects the possible existence of worlds that offer more benign environments to life than Earth does. We call these objects "superhabitable" and discuss in which contexts this term could be used, that is to say, which worlds tend to be more habitable than Earth. In an appendix, we show why the principle of mediocracy cannot be used to logically explain why Earth should be a particularly habitable planet or why other inhabited worlds should be Earth-like. Superhabitable worlds must be considered for future follow-up observations of signs of extraterrestrial life. Considering a range of physical effects, we conclude that they will tend to be slightly older and more massive than Earth and that their host stars will likely be K dwarfs. This makes Alpha Centauri B, which is a member of the closest stellar system to the Sun and is supposed to host an Earth-mass planet, an ideal target for searches for a superhabitable world.

Eyes on Planet Earth! Exploring Your Local Watershed

ERIC Educational Resources Information Center

Smith, Michael J.; Southard, John B.

2003-01-01

The American Geological Institute is helping teachers and geoscientists to emphasize the importance of inquiry and active investigation of the world around by selecting "Eyes on Planet Earth: Monitoring Our Changing World" as the theme of this year's Earth Science Week. The activity on the back of this month's poster insert, "Monitoring the…

The Potential for Volcanism and Tectonics on Extrasolar Terrestrial Planets

NASA Astrophysics Data System (ADS)

Quick, Lynnae C.; Roberge, Aki

2018-01-01

JWST and other next-generation space telescopes (e.g., LUVOIR, HabEx, & OST) will usher in a new era of exoplanet characterization that may lead to the identification of habitable, Earth-like worlds. Like the planets and moons in our solar system, the surfaces and interiors of terrestrial exoplanets may be shaped by volcanism and tectonics (Fu et al., 2010; van Summeren et al., 2011; Henning and Hurford, 2014). The magnitude and rate of occurrence of these dynamic processes can either facilitate or preclude the existence of habitable environments. Likewise, it has been suggested that detections of cryovolcanism on icy exoplanets, in the form of geyser-like plumes, could indicate the presence of subsurface oceans (Quick et al., 2017).The presence of volcanic and tectonic activity on solid exoplanets will be intimately linked to planet size and heat output in the form of radiogenic and/or tidal heating. In order to place bounds on the potential for such activity, we estimated the heat output of a variety of exoplanets observed by Kepler. We considered planets whose masses and radii range from 0.067 ME (super-Ganymede) to 8 ME (super-Earth), and 0.5 to 1.8 RE, respectively. These heat output estimates were then compared to those of planets, moons, and dwarf planets in our solar system for which we have direct evidence for the presence/absence of volcanic and tectonic activity. After exoplanet heating rates were estimated, depths to putative molten layers in their interiors were also calculated. For planets such as TRAPPIST-1h, whose densities, orbital parameters, and effective temperatures are consistent with the presence of significant amounts of H2O (Luger et al., 2017), these calculations reveal the depths to internal oceans which may serve as habitable niches beneath surface ice layers.

The Human Orrery

NASA Astrophysics Data System (ADS)

Bailey, M. E.; Christou, A. A.; Asher, D. J.

2005-08-01

The Human Orrery is a dynamic model of the solar system, where people play the role of the moving planets. The users' interactions with the model lead to greater awareness of their place in space and understanding of our planet's changing position with time. It is an innovative concept, the first example in the world to show with precision the elliptical orbits and changing positions of the main bodies in the solar system. It engages the general public in science and mathematics, and introduces key concepts in astronomy and space science in a fun and entertaining way. The model shows the orbits of the six classical planets, a main-belt asteroid (Ceres) and two comets (Halley and Encke) at a scale of 1 metre to 1 AU. It contains more than 200 individually inscribed discs showing the positions of objects at intervals of 16 days or multiples thereof. The region beyond Saturn shows the thirteen ecliptic constellations and directions to more distant objects in the Universe. Activities include `walking the orrery' (moving around the orbits in lockstep from one disc to the next to illustrate Kepler's third law of planetary motion); identifying which planets are visible tonight (or at any other time); and discovering phenomena such as planetary alignments, conjunctions and transits. Younger users can run the orrery; measure the distance between planets or a planet's speed in different parts of its orbit; or use the open space for to create a `dance of the planets'. Advanced users can investigate Kepler's laws by direct measurement; modular arithmetic; properties of ellipses; and calendrical concepts such as leap years and the need for the Gregorian reform. For more information, see http://star.arm.ac.uk/orrery/. The Human Orrery's construction was funded by the Northern Ireland Department of Culture, Arts and Leisure.

Constraints on the Compositions of Small Planets from the HARPS-N Consortium

NASA Astrophysics Data System (ADS)

Charbonneau, David

2015-12-01

HARPS-N is an ultra-stable fiber-fed high-resolution spectrograph optimized for the measurement of very precise radial velocities. The NASA Kepler Mission has demonstrated that planets with radii between 1 - 2.5 that of the Earth are common around Sun-like stars. A chief objective of the HARPS-N Consortium is to measure accurately the masses and infer compositions for a sample of these small worlds. Here I report on our conclusions from the first three years. After analyzing the Kepler light curves to vet potential targets, favoring those with asteroseismic estimates of the stellar properties and excluding those likely to show high RV jitter, we lavished attention on our sample: We typically gathered 100 observations per target, which permitted a mass accuracy of better than 20%. We find that all planets smaller than 1.5 Earth radii are rocky, while we have yet to find a rocky planet larger than this size. I report on the resulting constraints on the planetary compositions, including previously unpublished estimates for several worlds. Comparison of the inferred iron-to-rock ratios to the spectroscopically determined abundances of Fe, Mg, and Si in the stellar atmospheres should provide insight into the formation of terrestrial worlds. I address the transition from rocky planets to Neptune-like worlds, noting that our targets are highly irradiated and hence have likely experienced atmospheric mass loss. The K2 and TESS Missions will provide a list of similarly sized planets around much brighter stars, for which the greater apparent brightness will permit us to measure densities of planets at longer orbital periods, where atmospheric escape will be less important.

The Stability of Orbital Configurations and the Ultimate Configurations of Planetary and Satellite Systems

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Duncan, Martin J.

2004-01-01

The contents include the following: 1) Dynamical Evolution of the Earth-Moon Progenitors. 2) Dynamical Connections between Giant and Terrestrial Planets. 3) Dynamics of the Upsilon Andromedae Planetary System. 4) Dynamics of the Planets Orbiting GJ 876. and 5) Integrators for Planetary Accretion in Binaries.

Mapping the Nearest Stars for Exotic Habitable Worlds

NASA Astrophysics Data System (ADS)

Seager, Sara

2014-06-01

Exoplanets are planets orbiting stars other than the sun. Thousands of exoplanets are known and thousands of more planet candidates have been found. Until now, the dominant focus on habitable worlds has been on Earth-like planets, because Earth is the only known planet with life. Yet exoplanets are astonishingly diverse—in terms of their masses, densities, orbits, and host star types—and this diversity motivates a radical extension of what conventionally constitutes a habitable planet. The race to find habitable exoplanets has accelerated with the realization that “big Earths” transiting small stars can be both discovered and characterized with current technology. Moreover, technology for space-based direct imaging of Earth analogs has been rapidly maturing. The ambitious goal of inferring signs of life via biosignature gases in an exoplanet atmosphere, once only a futuristic thought, is now within reach.

Scenarios of giant planet formation and evolution and their impact on the formation of habitable terrestrial planets.

PubMed

Morbidelli, Alessandro

2014-04-28

In our Solar System, there is a clear divide between the terrestrial and giant planets. These two categories of planets formed and evolved separately, almost in isolation from each other. This was possible because Jupiter avoided migrating into the inner Solar System, most probably due to the presence of Saturn, and never acquired a large-eccentricity orbit, even during the phase of orbital instability that the giant planets most likely experienced. Thus, the Earth formed on a time scale of several tens of millions of years, by collision of Moon- to Mars-mass planetary embryos, in a gas-free and volatile-depleted environment. We do not expect, however, that this clear cleavage between the giant and terrestrial planets is generic. In many extrasolar planetary systems discovered to date, the giant planets migrated into the vicinity of the parent star and/or acquired eccentric orbits. In this way, the evolution and destiny of the giant and terrestrial planets become intimately linked. This paper discusses several evolutionary patterns for the giant planets, with an emphasis on the consequences for the formation and survival of habitable terrestrial planets. The conclusion is that we should not expect Earth-like planets to be typical in terms of physical and orbital properties and accretion history. Most habitable worlds are probably different, exotic worlds.

THESIS: terrestrial and habitable zone infrared spectroscopy spacecraft

NASA Astrophysics Data System (ADS)

Vasisht, G.; Swain, M. R.; Akeson, R. L.; Burrows, A.; Deming, D.; Grillmair, C. J.; Greene, T. P.

2008-07-01

THESIS is a concept for a medium class mission designed for spectroscopic characterization of extrasolar planets between 2-14 microns. The concept leverages off the recent first-steps made by Spitzer and Hubble in characterizing the atmospheres of alien gas giants. Under favourable circumstances, THESIS is capable of identifying biogenic molecules in habitable-zone planets, thereby determining conditions on worlds where life might exist. By systematically characterizing many worlds, from rocky planets to gas-giants, THESIS would deliver transformational science of profound interest to astronomers and the general public.

Spacing of Kepler Planets: Sculpting by Dynamical Instability

NASA Astrophysics Data System (ADS)

Pu, Bonan; Wu, Yanqin

2015-07-01

We study the orbital architecture of multi-planet systems detected by the Kepler transit mission using N-body simulations, focusing on the orbital spacing between adjacent planets in systems showing four or more transiting planets. We find that the observed spacings are tightly clustered around 12 mutual Hill radii, when transit geometry and sensitivity limits are accounted for. In comparison, dynamical integrations reveal that the minimum spacing required for systems of similar masses to survive dynamical instability for as long as 1 billion yr is ∼10 if all orbits are circular and coplanar and ∼12 if planetary orbits have eccentricities of ∼0.02 (a value suggested by studies of planet transit-time variations). This apparent coincidence, between the observed spacing and the theoretical stability threshold, leads us to propose that typical planetary systems were formed with even tighter spacing, but most, except for the widest ones, have undergone dynamical instability, and are pared down to a more anemic version of their former selves, with fewer planets and larger spacings. So while the high-multiple systems (five or more transiting planets) are primordial systems that remain stable, the single or double planetary systems, abundantly discovered by the Kepler mission, may be the descendants of more closely packed high-multiple systems. If this hypothesis is correct, we infer that the formation environment of Kepler systems should be more dissipative than that of the terrestrial planets.

Development of a Planet Tool for an interactive School Atlas as eBook

NASA Astrophysics Data System (ADS)

Wondrak, Stephan

2018-05-01

The present thesis describes the development of a planet tool for an interactive school atlas using an eBook format. Especially the technical and cartographical capabilities of the open standard ePUB 3 are evaluated. An eBook application with interactive and dynamic 2-dimensional visualizations is developed especially to show whether the re-al-world dimensions and distances in the solar system can be mapped in a cartographical correct and for students easy understandable manner. In the first part of the work, the requirements of the planet tool are evaluated in co-operation with experts. The open standards PDF and ePUB 3 are investigated with regard to the requirements for the development of the planet tool. Another chapter describes in detail all significant steps of the development process for a prototype of the planet tool. A graphic file originally created for print production is prepared and enhanced with interactive features to generate one of the eBook pages. This serves to show a potential workflow for the generation of eBook pages in a cross-media atlas production. All sample pages of the prototype show different layouts and contain the entire spectrum of interactive features and multimedia content of modern eBooks. The sample pages are presented and discussed in an own chapter. The results of the present work aim at answering the question concerning the suitability of the open standard ePUB 3 for the development of a multimedia eBook for high school education.

From polar wander to dynamic planet: A tribute to Keith Runcorn

USGS Publications Warehouse

Girdler, R.W.

1998-01-01

The evolution of Keith Runcorn's ideas from the static, elastic Earth of Jeffreys to a dynamic, convecting planet are presented based on discussions as his colleague over 25 years from 1963 to his retirement in 1988. Keith reached the concept of a dynamic planet by way of polar wander and continental drift using palaeomagnetism with great zeal. It took some time for Keith to convince himself of the reality of continental drift. Once convinced, he became an evangelist converting others and enthusiastically pursuing possible mechanisms for explaining it, homing in on mantle convection. To establish the nature and history of mantle convection his interests ranged from the world rift system and satellite gravity anomalies to the radiometric age peaks. A great step forward occurred when we realised that a region of uprising convection was not necessary under all the rifts as had been commonly advocated in the 1960s and that the mid-Atlantic, African and Indian Ocean rifts could be equally well explained by one large region of upwelling mantle convection. It was also realised that the plate convergence zones (island arcs, trenches and deep focus earthquakes) were much better correlated with the satellite gravity anomalies and it was much easier to locate the possible regions of downwelling mantle convection. Now, seismic tomography helps to establish the nature of mantle convection and it appears that relations among the Earth's surface features, the geoid anomalies and peturbations of mantle seismic velocities are near to being established. In the next few years a far better and accurate picture of the geometry of mantle convection so enthusiastically advocated by Keith Runcorn is likely to be seen.

Dynamical Constraints on Non-Transiting Planets at Trappist-1

NASA Astrophysics Data System (ADS)

Jontof-Hutter, Daniel; Truong, Vinh; Ford, Eric; Robertson, Paul; Terrien, Ryan

2018-04-01

The outermost of the seven known planets of Trappist-1 orbits six times closer to its host star than Mercury orbits the sun. The architecture of this system beyond 0.07 AU remains unknown. While the presence of additional planets will ultimately be determined by observations, in the meantime, some constraints can be derived from dynamical models.We will firstly look at the expected signature of additional planets at Trappist-1 on the transit times of the known planets to determine at what distances putatuve planets can be ruled out.Secondly, the remarkably compact configuration of Trappist-1 ensures that the known planets are secularly coupled, keeping their mutual inclinations very small and making their cotransiting geometry likely if Trappist-1h transits. We determine the range of masses and orbital inclinations of a putatuve outer planet that would make the observed configuration unlikely, and compare these to these constraints to those expected from radial velocity observations.

Spin dynamics of close-in planets exhibiting large transit timing variations

NASA Astrophysics Data System (ADS)

Delisle, J.-B.; Correia, A. C. M.; Leleu, A.; Robutel, P.

2017-09-01

We study the spin evolution of close-in planets in compact multi-planetary systems. The rotation period of these planets is often assumed to be synchronous with the orbital period due to tidal dissipation. Here we show that planet-planet perturbations can drive the spin of these planets into non-synchronous or even chaotic states. In particular, we show that the transit timing variation (TTV) is a very good probe to study the spin dynamics, since both are dominated by the perturbations of the mean longitude of the planet. We apply our model to KOI-227 b and Kepler-88 b, which are both observed undergoing strong TTVs. We also perform numerical simulations of the spin evolution of these two planets. We show that for KOI-227 b non-synchronous rotation is possible, while for Kepler-88 b the rotation can be chaotic.

Dynamical effects of stellar companions

NASA Astrophysics Data System (ADS)

Naoz, Smadar

2015-08-01

The fraction of stellar binaries in the field is extremely high (about 40% - 70% for > 1 Msun stars), and thus, given this frequency, a large fraction of all exoplanetary systems may reside in binaries. While close-in giant planets tend to be found preferentially in binary stellar systems it seems that the frequency of giant planets in close binaries (<100 AU) is significantly lower than in the overall population. Stellar companions’ gravitational perturbations may significantly alter the planetary orbits around their partner on secular timescales. They can drive planets to large eccentric orbits which can either result in plunging these planets into the star or shrinking their orbits and forming short period planets. I will review the dynamical effects stellar binaries have on a planetary systems. I will also present new results on the influence that stellar evolution has on the dynamical processes in these systems.

Probing the Impact of Stellar Duplicity on Planet Occurrence with Spectroscopic and Imaging Observations

NASA Astrophysics Data System (ADS)

Eggenberger, Anne; Udry, Stéphane

Over the past 14 years, Doppler spectroscopy has been very successful in detecting and characterizing extrasolar planets, providing us with a wealth of information on these distant worlds (e.g., Marcy et al. 2005a; Udry and Santos 2007b; Udry et al. 2007a). One important and considerably unexpected fact these new data have taught us is that diversity is the rule in the planetary world. Diversity is found not only in the characteristics and orbital properties of the ˜ 340 planets detected thus far,1 but also in the types of environments in which they reside and are able to form. This observation has prompted a serious revision of the theories of planet formation (e.g., Lissauer and Stevenson 2007; Durisen et al. 2007; Nagasawa et al. 2007), leading to the idea that planet formation may be a richer and more robust process than originally thought.

Statistical Study of the Early Solar System's Instability with 4, 5 and 6 Giant Planets

NASA Astrophysics Data System (ADS)

Nesvorny, David; Morbidelli, A.

2012-10-01

Several properties of the Solar System, including the wide radial spacing and orbital eccentricities of giant planets, can be explained if the early Solar System evolved through a dynamical instability followed by migration of planets in the planetesimal disk. Here we report the results of a statistical study, in which we performed nearly ten thousand numerical simulations of planetary instability starting from hundreds of different initial conditions. We found that the dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, leading to ejection of least one ice giant from the Solar System. Planet ejection can be avoided if the mass of the transplanetary disk of planetesimals was large, but we found that a massive disk would lead to excessive dynamical damping, and to smooth migration that violates constraints from the survival of the terrestrial planets. Better results were obtained when the Solar System was assumed to have five giant planets initially and one ice giant, with the mass comparable to that of Uranus and Neptune, was ejected into interstellar space by Jupiter. The best results were obtained when the ejected planet was placed into the external 3:2 or 4:3 resonance with Saturn. The range of possible outcomes is rather broad in this case, indicating that the present Solar System is neither a typical nor expected result for a given initial state, and occurs, in best cases, with only a few percent probability. The case with six giant planets shows interesting dynamics but does offer significant advantages relative to the five planet case.

iGlobe Interactive Visualization and Analysis of Spatial Data

NASA Technical Reports Server (NTRS)

Hogan, Patrick

2012-01-01

iGlobe is open-source software built on NASA World Wind virtual globe technology. iGlobe provides a growing set of tools for weather science, climate research, and agricultural analysis. Up until now, these types of sophisticated tools have been developed in isolation by national agencies, academic institutions, and research organizations. By providing an open-source solution to analyze and visualize weather, climate, and agricultural data, the scientific and research communities can more readily advance solutions needed to understand better the dynamics of our home planet, Earth

Richest Planetary System Discovered - Up to seven planets orbiting a Sun-like star

NASA Astrophysics Data System (ADS)

2010-08-01

Astronomers using ESO's world-leading HARPS instrument have discovered a planetary system containing at least five planets, orbiting the Sun-like star HD 10180. The researchers also have tantalising evidence that two other planets may be present, one of which would have the lowest mass ever found. This would make the system similar to our Solar System in terms of the number of planets (seven as compared to the Solar System's eight planets). Furthermore, the team also found evidence that the distances of the planets from their star follow a regular pattern, as also seen in our Solar System. "We have found what is most likely the system with the most planets yet discovered," says Christophe Lovis, lead author of the paper reporting the result. "This remarkable discovery also highlights the fact that we are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets. Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system." The team of astronomers used the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla, Chile, for a six-year-long study of the Sun-like star HD 10180, located 127 light-years away in the southern constellation of Hydrus (the Male Water Snake). HARPS is an instrument with unrivalled measurement stability and great precision and is the world's most successful exoplanet hunter. Thanks to the 190 individual HARPS measurements, the astronomers detected the tiny back and forth motions of the star caused by the complex gravitational attractions from five or more planets. The five strongest signals correspond to planets with Neptune-like masses - between 13 and 25 Earth masses [1] - which orbit the star with periods ranging from about 6 to 600 days. These planets are located between 0.06 and 1.4 times the Earth-Sun distance from their central star. "We also have good reasons to believe that two other planets are present," says Lovis. One would be a Saturn-like planet (with a minimum mass of 65 Earth masses) orbiting in 2200 days. The other would be the least massive exoplanet ever discovered [2], with a mass of about 1.4 times that of the Earth. It is very close to its host star, at just 2 percent of the Earth-Sun distance. One "year" on this planet would last only 1.18 Earth-days. "This object causes a wobble of its star of only about 3 km/hour - slower than walking speed - and this motion is very hard to measure," says team member Damien Ségransan. If confirmed, this object would be another example of a hot rocky planet, similar to Corot-7b (eso0933). The newly discovered system of planets around HD 10180 is unique in several respects. First of all, with at least five Neptune-like planets lying within a distance equivalent to the orbit of Mars, this system is more populated than our Solar System in its inner region, and has many more massive planets there [3]. Furthermore, the system probably has no Jupiter-like gas giant. In addition, all the planets seem to have almost circular orbits. So far, astronomers know of fifteen systems with at least three planets. The last record-holder was 55 Cancri, which contains five planets, two of them being giant planets. "Systems of low-mass planets like the one around HD 10180 appear to be quite common, but their formation history remains a puzzle," says Lovis. Using the new discovery as well as data for other planetary systems, the astronomers found an equivalent of the Titius-Bode law that exists in our Solar System: the distances of the planets from their star seem to follow a regular pattern [4]. "This could be a signature of the formation process of these planetary systems," says team member Michel Mayor. Another important result found by the astronomers while studying these systems is that there is a relationship between the mass of a planetary system and the mass and chemical content of its host star. All very massive planetary systems are found around massive and metal-rich stars, while the four lowest-mass systems are found around lower-mass and metal-poor stars [5]. Such properties confirm current theoretical models. The discovery is announced today at the international colloquium "Detection and dynamics of transiting exoplanets", at the Observatoire de Haute-Provence, France. Notes [1] Using the radial velocity method, astronomers can only estimate a minimum mass for a planet as the mass estimate also depends on the tilt of the orbital plane relative to the line of sight, which is unknown. From a statistical point of view, this minimum mass is however often close to the real mass of the planet. [2] (added 30 August 2010) HD 10180b would be the lowest mass exoplanet discovered orbiting a "normal" star like our Sun. However, lower mass exoplanets have been previously discovered orbiting the pulsar PSR B1257+12 (a highly magnetised rotating neutron star). [3] On average the planets in the inner region of the HD 10180 system have 20 times the mass of the Earth, whereas the inner planets in our own Solar System (Mercury, Venus, Earth and Mars) have an average mass of half that of the Earth. [4] The Titius-Bode law states that the distances of the planets from the Sun follow a simple pattern. For the outer planets, each planet is predicted to be roughly twice as far away from the Sun as the previous object. The hypothesis correctly predicted the orbits of Ceres and Uranus, but failed as a predictor of Neptune's orbit. [5] According to the definition used in astronomy, "metals" are all the elements other than hydrogen and helium. Such metals, except for a very few minor light chemical elements, have all been created by the various generations of stars. Rocky planets are made of "metals". More information This research was presented in a paper submitted to Astronomy and Astrophysics ("The HARPS search for southern extra-solar planets. XXVII. Up to seven planets orbiting HD 10180: probing the architecture of low-mass planetary systems" by C. Lovis et al.). The team is composed of C. Lovis, D. Ségransan, M. Mayor, S. Udry, F. Pepe, and D. Queloz (Observatoire de Genève, Université de Genève, Switzerland), W. Benz (Universität Bern, Switzerland), F. Bouchy (Institut d'Astrophysique de Paris, France), C. Mordasini (Max-Planck-Institut für Astronomie, Heidelberg, Germany), N. C. Santos (Universidade do Porto, Portugal), J. Laskar (Observatoire de Paris, France), A. Correia (Universidade de Aveiro, Portugal), and J.-L. Bertaux (Université Versailles Saint-Quentin, France) and G. Lo Curto (ESO). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth

NASA Technical Reports Server (NTRS)

Batalha, Natalie M.

2018-01-01

A Planet for Goldilocks: The Search for Evidence of Life Beyond Earth "Not too hot, not too cold" begins the prescription for a world that's just right for life as we know it. Finding evidence of life beyond Earth is one of the primary goals of science agencies around the world thanks in large part to NASA's Kepler Mission which launched in 2009 with the objective of finding Goldilocks planets orbiting other stars like our Sun. Indeed, the space telescope opened our eyes to the terrestrial-sized planets that populate the galaxy as well as exotic worlds unlike anything that exists in the solar system. The mission ignited the search for life beyond earth via remote detection of atmospheric biosignatures on exoplanets. Most recently, our collective imagination was awakened by the discovery of Goldilocks worlds orbiting some of the nearest neighbors to the Sun, turning abstractions into destinations. Dr. Batalha will give an overview of the science legacy of the Kepler Mission and other key discoveries. She'll give a preview of what's to come by highlighting the missions soon to launch and those that are concepts taking shape on the drawing board.

Dynamical Constraints on Nontransiting Planets Orbiting TRAPPIST-1

NASA Astrophysics Data System (ADS)

Jontof-Hutter, Daniel; Truong, Vinh H.; Ford, Eric B.; Robertson, Paul; Terrien, Ryan C.

2018-06-01

We derive lower bounds on the orbital distance and inclination of a putative planet beyond the transiting seven planets of TRAPPIST-1, for a range of masses ranging from 0.08 M Jup to 3.5 M Jup. While the outer architecture of this system will ultimately be constrained by radial velocity measurements over time, we present dynamical constraints from the remarkably coplanar configuration of the seven transiting planets, which is sensitive to modestly inclined perturbers. We find that the observed configuration is unlikely if a Jovian-mass planet inclined by ≥3° to the transiting planet exists within 0.53 au, exceeding any constraints from transit timing variations (TTV) induced in the known planets from an undetected perturber. Our results will inform RV programs targeting TRAPPIST-1, and for near coplanar outer planets, tighter constraints are anticipated for radial velocity (RV) precisions of ≲140 m s‑1. At higher inclinations, putative planets are ruled out to greater orbital distances with orbital periods up to a few years.

Forever Alone? Testing Single Eccentric Planetary Systems for Multiple Companions

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Wang, Songhu; Horner, Jonathan; Tinney, C. G.; Butler, R. P.; Jones, H. R. A.; O'Toole, S. J.; Bailey, J.; Carter, B. D.; Salter, G. S.; Wright, D.; Zhou, Ji-Lin

2013-09-01

Determining the orbital eccentricity of an extrasolar planet is critically important for understanding the system's dynamical environment and history. However, eccentricity is often poorly determined or entirely mischaracterized due to poor observational sampling, low signal-to-noise, and/or degeneracies with other planetary signals. Some systems previously thought to contain a single, moderate-eccentricity planet have been shown, after further monitoring, to host two planets on nearly circular orbits. We investigate published apparent single-planet systems to see if the available data can be better fit by two lower-eccentricity planets. We identify nine promising candidate systems and perform detailed dynamical tests to confirm the stability of the potential new multiple-planet systems. Finally, we compare the expected orbits of the single- and double-planet scenarios to better inform future observations of these interesting systems.

Chaotic Dynamics of Trans-Neptunian Objects Perturbed by Planet Nine

NASA Astrophysics Data System (ADS)

Hadden, Sam; Li, Gongjie; Payne, Matthew J.; Holman, Matthew J.

2018-06-01

Observations of clustering among the orbits of the most distant trans-Neptunian objects (TNOs) has inspired interest in the possibility of an undiscovered ninth planet lurking in the outskirts of the solar system. Numerical simulations by a number of authors have demonstrated that, with appropriate choices of planet mass and orbit, such a planet can maintain clustering in the orbital elements of the population of distant TNOs, similar to the observed sample. However, many aspects of the rich underlying dynamical processes induced by such a distant eccentric perturber have not been fully explored. We report the results of our investigation of the dynamics of coplanar test-particles that interact with a massive body on an circular orbit (Neptune) and a massive body on a more distant, highly eccentric orbit (the putative Planet Nine). We find that a detailed examination of our idealized simulations affords tremendous insight into the rich test-particle dynamics that are possible. In particular, we find that chaos and resonance overlap plays an important role in particles’ dynamical evolution. We develop a simple mapping model that allows us to understand, in detail, the web of overlapped mean-motion resonances explored by chaotically evolving particles. We also demonstrate that gravitational interactions with Neptune can have profound effects on the orbital evolution of particles. Our results serve as a starting point for a better understanding of the dynamical behavior observed in more complicated simulations that can be used to constrain the mass and orbit of Planet Nine.

This Dynamic Planet: World map of volcanoes, earthquakes, impact craters and plate tectonics

USGS Publications Warehouse

Simkin, Tom; Tilling, Robert I.; Vogt, Peter R.; Kirby, Stephen H.; Kimberly, Paul; Stewart, David B.

2006-01-01

Our Earth is a dynamic planet, as clearly illustrated on the main map by its topography, over 1500 volcanoes, 44,000 earthquakes, and 170 impact craters. These features largely reflect the movements of Earth's major tectonic plates and many smaller plates or fragments of plates (including microplates). Volcanic eruptions and earthquakes are awe-inspiring displays of the powerful forces of nature and can be extraordinarily destructive. On average, about 60 of Earth's 550 historically active volcanoes are in eruption each year. In 2004 alone, over 160 earthquakes were magnitude 6.0 or above, some of which caused casualties and substantial damage. This map shows many of the features that have shaped--and continue to change--our dynamic planet. Most new crust forms at ocean ridge crests, is carried slowly away by plate movement, and is ultimately recycled deep into the earth--causing earthquakes and volcanism along the boundaries between moving tectonic plates. Oceans are continually opening (e.g., Red Sea, Atlantic) or closing (e.g., Mediterranean). Because continental crust is thicker and less dense than thinner, younger oceanic crust, most does not sink deep enough to be recycled, and remains largely preserved on land. Consequently, most continental bedrock is far older than the oldest oceanic bedrock. (see back of map) The earthquakes and volcanoes that mark plate boundaries are clearly shown on this map, as are craters made by impacts of extraterrestrial objects that punctuate Earth's history, some causing catastrophic ecological changes. Over geologic time, continuing plate movements, together with relentless erosion and redeposition of material, mask or obliterate traces of earlier plate-tectonic or impact processes, making the older chapters of Earth's 4,500-million-year history increasingly difficult to read. The recent activity shown on this map provides only a present-day snapshot of Earth's long history, helping to illustrate how its present surface came to be. The map is designed to show the most prominent features when viewed from a distance, and more detailed features upon closer inspection. The back of the map zooms in further, highlighting examples of fundamental features, while providing text, timelines, references, and other resources to enhance understanding of this dynamic planet. Both the front and back of this map illustrate the enormous recent growth in our knowledge of planet Earth. Yet, much remains unknown, particularly about the processes operating below the ever-shifting plates and the detailed geological history during all but the most recent stage of Earth's development.

NEWLY DISCOVERED PLANETS ORBITING HD 5319, HD 11506, HD 75784 AND HD 10442 FROM THE N2K CONSORTIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giguere, Matthew J.; Fischer, Debra A.; Brewer, John M.

2015-01-20

Initially designed to discover short-period planets, the N2K campaign has since evolved to discover new worlds at large separations from their host stars. Detecting such worlds will help determine the giant planet occurrence at semi-major axes beyond the ice line, where gas giants are thought to mostly form. Here we report four newly discovered gas giant planets (with minimum masses ranging from 0.4 to 2.1 M {sub Jup}) orbiting stars monitored as part of the Next 2000 target stars (N2K) Doppler Survey program. Two of these planets orbit stars already known to host planets: HD 5319 and HD 11506. Themore » remaining discoveries reside in previously unknown planetary systems: HD 10442 and HD 75784. The refined orbital period of the inner planet orbiting HD 5319 is 641 days. The newly discovered outer planet orbits in 886 days. The large masses combined with the proximity to a 4:3 mean motion resonance make this system a challenge to explain with current formation and migration theories. HD 11506 has one confirmed planet, and here we confirm a second. The outer planet has an orbital period of 1627.5 days, and the newly discovered inner planet orbits in 223.6 days. A planet has also been discovered orbiting HD 75784 with an orbital period of 341.7 days. There is evidence for a longer period signal; however, several more years of observations are needed to put tight constraints on the Keplerian parameters for the outer planet. Lastly, an additional planet has been detected orbiting HD 10442 with a period of 1043 days.« less

Orbital Dynamics and Habitability of Exoplanets

NASA Astrophysics Data System (ADS)

Deitrick, Russell J.

With the discoveries of thousands of extra-solar planets, a handful of which are terrestrial in size and located within the "habitable zone" of their host stars, the discovery of another instance of life in the universe seems increasingly within our grasp. Yet, a number of difficulties remain--with current and developing technologies, the full characterization of a terrestrial atmosphere and, hence, the detection of biosignatures will be extraordinarily difficult and expensive. Furthermore, observations will be ambiguous, as recent developments have shown that there is no "smoking gun" for the presence of life. Ultimately, the interpretation of observations will depend heavily upon our understanding of life's fundamental properties and the physical context of a planet's observed properties. This thesis is devoted to a development of the latter quantity, physical context, focusing on a topic oft-neglected in theoretical works of habitability: orbital dynamics. I show a number of ways in which orbital dynamics can affect the habitability of exoplanets. This work highlights the crucial role of stability, mutual inclinations, and resonances, demonstrating how these properties influence atmospheric states. Studies of exoplanetary systems tend to assume that the planets are coplanar, however, the large mutual inclination of the planets orbiting upsilon Andromedae suggests that coplanarity is not always a valid assumption. In my study of this system, I show that the large inclination between planets c and d and their large eccentricities lead to dramatic orbital variations. Though there is almost certainly no habitable planet orbiting upsilon And, the existence of this system demonstrates that we should expect other such dynamically "hot" planetary systems, some of which may contain potentially habitable planets. Minute variations in a planet's orbit can lead to changes in the global temperature, and indeed, these variations seem to be intimately connected to Earth's Pleistocene ice ages. Mutual inclinations lead not only to larger variations in a planet's obliquity, but also uncover secular spin-orbit resonances, which lead to yet more dramatic behavior. I modeled the obliquity evolution of planets in this highly non-linear dynamical regime. Connecting the dynamical models to an simple climate model with ice sheets, I modeled the effects of such dynamical evolution on an Earth-like planet's climate. As expected, such "exo-Milankovitch cycles" can be rapid and dramatic, often leading to complete collapse into a snowball state. By demonstrating a handful of the many ways dynamics can influence habitability, this research provides context to observations of exoplanets and connects to one of the key goals of astrobiology, to "Determine the potential for habitable planets beyond the Solar System, and characterize those that are observable" (Des Marais et al., 2008). It provides tools and techniques that may be used to help prioritize exoplanet targets for characterization missions when very little information is known other than orbital properties. It also demonstrates how orbital evolution affects observable quantities like albedo, and will assist in the interpretation of spectra.

Exoplanets, Exo-Solar Life, and Human Significance

NASA Technical Reports Server (NTRS)

Wiseman, Jennifer

2011-01-01

With the recent detection of over 500 extrasolar planets, the existence of "other worlds", perhaps even other Earths, is no longer in the realm of science fiction. The study of exoplanets rapidly moved from an activity on the fringe of astronomy to one of the highest priorities of the world's astronomical programs. Actual images of extrasolar planets were revealed over the past two years for the first time. NASA's Hubble Space Telescope is already characterizing the atmospheres of Jupiter-like planets, in other systems. And the recent launch of the NASA Kepler space telescope is enabling the first statistical assessment of how common solar systems like our own really are. As we begin to characterize these "other worlds" and assess their habitability, the question of the significance and uniqueness of life on Earth will impact our society as never before. I will provide a comprehensive overview of the techniques and status of exoplanet detection, followed by reflections as to the societal impact of finding out that Earths are common, or rare. Will finding other potentially habitable planets create another "Copernican Revolution"? Will perceptions of the significance of life on Earth change when we find other Earth-like planets? I will discuss the plans of the scientific community for future telescopes that will be abe to survey our solar neighborhood for Earth-like planets, study their atmospheres, and search for biological signs of life.

Survival of habitable planets in unstable planetary systems

NASA Astrophysics Data System (ADS)

Carrera, Daniel; Davies, Melvyn B.; Johansen, Anders

2016-12-01

Many observed giant planets lie on eccentric orbits. Such orbits could be the result of strong scatterings with other giant planets. The same dynamical instability that produces these scatterings may also cause habitable planets in interior orbits to become ejected, destroyed, or be transported out of the habitable zone. We say that a habitable planet has resilient habitability if it is able to avoid ejections and collisions and its orbit remains inside the habitable zone. Here we model the orbital evolution of rocky planets in planetary systems where giant planets become dynamically unstable. We measure the resilience of habitable planets as a function of the observed, present-day masses and orbits of the giant planets. We find that the survival rate of habitable planets depends strongly on the giant planet architecture. Equal-mass planetary systems are far more destructive than systems with giant planets of unequal masses. We also establish a link with observation; we find that giant planets with present-day eccentricities higher than 0.4 almost never have a habitable interior planet. For a giant planet with a present-day eccentricity of 0.2 and semimajor axis of 5 au orbiting a Sun-like star, 50 per cent of the orbits in the habitable zone are resilient to the instability. As semimajor axis increases and eccentricity decreases, a higher fraction of habitable planets survive and remain habitable. However, if the habitable planet has rocky siblings, there is a significant risk of rocky planet collisions that would sterilize the planet.

Integrated software package STAMP for minor planets

NASA Technical Reports Server (NTRS)

Kochetova, O. M.; Shor, Viktor A.

1992-01-01

The integrated software package STAMP allowed for rapid and exact reproduction of the tables of the year-book 'Ephemerides of Minor Planets.' Additionally, STAMP solved the typical problems connected with the use of the year-book. STAMP is described. The year-book 'Ephemerides of Minor Planets' (EMP) is a publication used in many astronomical institutions around the world. It contains all the necessary information on the orbits of the numbered minor planets. Also, the astronomical coordinates are provided for each planet during its suitable observation period.

2014 Summer Series - Jon Jenkins - Chasing Shadow Worlds: Exoplanets from Kepler and Beyond

NASA Image and Video Library

2014-08-14

Twenty years ago, there were no planets known outside our own solar system. Since then, the discoveries of about 1500 planets orbiting other stars have radically altered our views of planets and planetary systems. This revolution in knowledge is due in no small part to the Kepler Mission, which has discovered over 950 of these planets and over 3000 planet candidates. This talk will review the greatest hits of Kepler and peek into the future of exoplanets.

Circularizing Planet Nine through dynamical friction with an extended, cold planetesimal belt

NASA Astrophysics Data System (ADS)

Eriksson, Linn E. J.; Mustill, Alexander J.; Johansen, Anders

2018-04-01

Unexpected clustering in the orbital elements of minor bodies beyond the Kuiper belt has led to speculations that our Solar system actually hosts nine planets, the eight established plus a hypothetical `Planet Nine'. Several recent studies have shown that a planet with a mass of about 10 Earth masses on a distant eccentric orbit with perihelion far beyond the Kuiper belt could create and maintain this clustering. The evolutionary path resulting in an orbit such as the one suggested for Planet Nine is nevertheless not easily explained. Here, we investigate whether a planet scattered away from the giant-planet region could be lifted to an orbit similar to the one suggested for Planet Nine through dynamical friction with a cold, distant planetesimal belt. Recent simulations of planetesimal formation via the streaming instability suggest that planetesimals can readily form beyond 100 au. We explore this circularisation by dynamical friction with a set of numerical simulations. We find that a planet that is scattered from the region close to Neptune on to an eccentric orbit has a 20-30 per cent chance of obtaining an orbit similar to that of Planet Nine after 4.6 Gyr. Our simulations also result in strong or partial clustering of the planetesimals; however, whether or not this clustering is observable depends on the location of the inner edge of the planetesimal belt. If the inner edge is located at 200 au, the degree of clustering amongst observable objects is significant.

Mars, the funny history of canals.1-the enigmatic planet. the plurality of worlds; Mars, la folle histoire des canaux. 1-l'énigmatique planète. la pluralité des mondes

NASA Astrophysics Data System (ADS)

Raffaitin, Gérard; Durand, Pierre

2016-03-01

Since the 17th century, the study of the planet Mars interested astronomers. The changes observed on Mars were enigmatic. Several philosophers thought that this planet does have inhabitants. Giovanni Schiaparelli observed canals and their changes. Was it the sign of a life on this planet?

A machine learns to predict the stability of circumbinary planets

NASA Astrophysics Data System (ADS)

Lam, Christopher; Kipping, David

2018-06-01

Long-period circumbinary planets appear to be as common as those orbiting single stars and have been found to frequently have orbital radii just beyond the critical distance for dynamical stability. Assessing the stability is typically done either through N-body simulations or using the classic stability criterion first considered by Dvorak and later developed by Holman and Wiegert: a second-order polynomial calibrated to broadly match numerical simulations. However, the polynomial is unable to capture islands of instability introduced by mean motion resonances, causing the accuracy of the criterion to approach that of a random coin-toss when close to the boundary. We show how a deep neural network (DNN) trained on N-body simulations generated with REBOUND is able to significantly improve stability predictions for circumbinary planets on initially coplanar, circular orbits. Specifically, we find that the accuracy of our DNN never drops below 86 per cent, even when tightly surrounding the boundary of instability, and is fast enough to be practical for on-the-fly calls during likelihood evaluations typical of modern Bayesian inference. Our binary classifier DNN is made publicly available at https://github.com/CoolWorlds/orbital-stability.

A Venus Flagship Mission: Exploring a World of Contrasts

NASA Astrophysics Data System (ADS)

Senske, D.; Bullock, M.; Balint, T.; Benz, A.; Campbell, B.; Chassefiere, E.; Colaprete, A.; Cutts, J.; Glaze, L.; Gorevan, S.; Grinspoon, D.; Hall, J.; Hasimoto, G.; Head, J.; Hunter, G.; Johnson, N.; Kiefer, W.; Kolawa, E.; Kremic, T.; Kwok, J.; Limaye, S.; Mackwell, S.; Marov, M.; Peterson, C.; Schubert, G.; Spilker, T.; Stofan, E.; Svedhem, H.; Titov, D.; Treiman, A.

2008-12-01

Results from past missions and the current Venus Express Mission show that Venus is a world of contrasts, providing clear science drivers for renewed exploration of this planet. In early 2008, NASA's Science Mission Directorate formed a Science and Technology Definition Team (STDT) to formulate science goals and objectives, mission architecture and a technology roadmap for a flagship class mission to Venus. This 3- to 4 billon mission, to launch in the post 2020 timeframe, should revolutionize our understanding of how climate works on terrestrial planets, including the close relationship between volcanism, tectonism, the interior, and the atmosphere. It would also more clearly elucidate the geologic history of Venus, including the existence and persistence of an ancient ocean. Achieving these objectives will provide a basis to understand the habitability of extra solar terrestrial planets. To address a broad range of science questions this mission will be composed of flight elements that include an orbiter that is highlighted by an interferometric SAR to provide surface topographic and image information at scales one to two orders of magnitude greater than that achieved by any previous spacecraft to Venus. Two balloons with a projected lifetime of weeks will probe the structure and dynamics of the atmosphere at an altitude of 50 to 70-km. In addition, two descent probes will collect data synergistic to that from the balloon and analyze the geochemistry of surface rocks over a period of hours. The technology road map focuses on key areas of science instruments and enabling engineering to provide greater in situ longevity in the hostile Venus environment.

Observations of Uranus and Neptune in Spanish Telescopes: Calar Alto/PlanetCam, WHT/Ingrid y GTC/Osiris

NASA Astrophysics Data System (ADS)

Hueso, R.; Sánchez-Lavega, A.; Ordonez-Etxeberria, I.; Rojas, J. F.; Pérez-Hoyos, S.; Mendikoa, I.

2017-03-01

The astronomical observation of the atmospheres of Uranus and Neptune poses unique challenges. Both planets are relatively dimm objects (visual magnitude of +5.3 and +7.7) and have small angular sizes (3.7” and 2.4” at opposition). Both worlds have atmospheres that are very dynamic, specially Neptune. These atmospheres are dominated by intense zonal winds that reach 450 m/s and where seasonal evolution changes the band patterns present in these planets. Thanks to the atmospheric methane gas, when observing Uranus and Neptune in near infrared wavelengths their upper clouds become well contrasted and bright and observations at different methane absorption bands allow to sample the atmosphere at different vertical layers. Both worlds are subject to the development of bright cloud patterns, some times of convective origin and whose activity can extend over weeks to several months or years. In the last few years we have surveyed the atmospheric activity of Uranus and Neptune with instruments able to improve the spatial resolution of the images beyond the limits impose by the atmospheric seeing. We use the Lucky Imaging technique (fast observation of several short-exposure frames combined with automatic selection of best frames and coregistration for stacking). We present image observations of Uranus and Neptune obtained with the instruments: OSIRIS at Grantecan as well as the AstraLux and PlanetCam UPV/EHU cameras on the 2.2m telescope at Calar Alto observatory. These observations are compared with other observations acquired by amateur astronomers able to obtain resolve cloud features in Uranus and Neptune. We compare these observations with images acquired with Adaptive Optics instruments at the William Herschel with the NAOMI+Ingrid instruments and Keck II and with Hubble Space Telescope images. We show the importance of surveying the atmospheric activity of these planets with a variety of telescopes. Two science cases are presented: The study of convective storms in Uranus in 2014 and the study of bright non convective features in Neptune in 2015.

Energy Balance Models and Planetary Dynamics

NASA Technical Reports Server (NTRS)

Domagal-Goldman, Shawn

2012-01-01

We know that planetary dynamics can have a significant affect on the climate of planets. Planetary dynamics dominate the glacial-interglacial periods on Earth, leaving a significant imprint on the geological record. They have also been demonstrated to have a driving influence on the climates of other planets in our solar system. We should therefore expect th.ere to be similar relationships on extrasolar planets. Here we describe a simple energy balance model that can predict the growth and thickness of glaciers, and their feedbacks on climate. We will also describe model changes that we have made to include planetary dynamics effects. This is the model we will use at the start of our collaboration to handle the influence of dynamics on climate.

Comparative Habitable Planet Signatures in Polarized Light

NASA Astrophysics Data System (ADS)

Bott, K.; Bailey, J.; Meadows, V.; Kedziora-Chudczer, L.; Cotton, D.; Crisp, D.

2017-11-01

VSTAR polarized light models of terrestrial worlds are compared for varying cloud, atmospheric, and surface conditions. Archetypal "Earth-like" planets are compared and the observability of their combined polarimetric effects assessed.

Dynamical Evolution Induced by Planet Nine

NASA Astrophysics Data System (ADS)

Batygin, Konstantin; Morbidelli, Alessandro

2017-12-01

The observational census of trans-Neptunian objects with semimajor axes greater than ˜ 250 {au} exhibits unexpected orbital structure that is most readily attributed to gravitational perturbations induced by a yet-undetected, massive planet. Although the capacity of this planet to (I) reproduce the observed clustering of distant orbits in physical space, (II) facilitate the dynamical detachment of their perihelia from Neptune, and (III) excite a population of long-period centaurs to extreme inclinations is well-established through numerical experiments, a coherent theoretical description of the dynamical mechanisms responsible for these effects remains elusive. In this work, we characterize the dynamical processes at play from semi-analytic grounds. We begin by considering a purely secular model of orbital evolution induced by Planet Nine and show that it is at odds with the ensuing stability of distant objects. Instead, the long-term survival of the clustered population of long-period Kuiper Belt objects (KBOs) is enabled by a web of mean-motion resonances driven by Planet Nine. Then, by taking a compact-form approach to perturbation theory, we show that it is the secular dynamics embedded within these resonances that regulate the orbital confinement and perihelion detachment of distant KBOs. Finally, we demonstrate that the onset of large-amplitude oscillations of the orbital inclinations is accomplished through the capture of low-inclination objects into a high-order secular resonance, and we identify the specific harmonic that drives the evolution. In light of the developed qualitative understanding of the governing dynamics, we offer an updated interpretation of the current observational data set within the broader theoretical framework of the Planet Nine hypothesis.

Planet-Planet Scattering in Planetesimal Disks. II. Predictions for Outer Extrasolar Planetary Systems

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Armitage, Philip J.; Gorelick, Noel

2010-03-01

We develop an idealized dynamical model to predict the typical properties of outer extrasolar planetary systems, at radii comparable to the Jupiter-to-Neptune region of the solar system. The model is based upon the hypothesis that dynamical evolution in outer planetary systems is controlled by a combination of planet-planet scattering and planetary interactions with an exterior disk of small bodies ("planetesimals"). Our results are based on 5000 long duration N-body simulations that follow the evolution of three planets from a few to 10 AU, together with a planetesimal disk containing 50 M ⊕ from 10 to 20 AU. For large planet masses (M >~ M Sat), the model recovers the observed eccentricity distribution of extrasolar planets. For lower-mass planets, the range of outcomes in models with disks is far greater than that which is seen in isolated planet-planet scattering. Common outcomes include strong scattering among massive planets, sudden jumps in eccentricity due to resonance crossings driven by divergent migration, and re-circularization of scattered low-mass planets in the outer disk. We present the distributions of the eccentricity and inclination that result, and discuss how they vary with planet mass and initial system architecture. In agreement with other studies, we find that the currently observed eccentricity distribution (derived primarily from planets at a <~ 3 AU) is consistent with isolated planet-planet scattering. We explain the observed mass dependence—which is in the opposite sense from that predicted by the simplest scattering models—as a consequence of strong correlations between planet masses in the same system. At somewhat larger radii, initial planetary mass correlations and disk effects can yield similar modest changes to the eccentricity distribution. Nonetheless, strong damping of eccentricity for low-mass planets at large radii appears to be a secure signature of the dynamical influence of disks. Radial velocity measurements capable of detecting planets with K ≈ 5 m s-1 and periods in excess of 10 years will provide constraints on this regime. Finally, we present an analysis of the predicted separation of planets in two-planet systems, and of the population of planets in mean-motion resonances (MMRs). We show that, if there are systems with ~ Jupiter-mass planets that avoid close encounters, the planetesimal disk acts as a damping mechanism and populates MMRs at a very high rate (50%-80%). In many cases, resonant chains (in particular the 4:2:1 Laplace resonance) are set up among all three planets. We expect such resonant chains to be common among massive planets in outer planetary systems.

Super-Earths, Warm Neptunes, and Hot Jupiters: Transmission Spectroscopy for Comparative Planetology

NASA Astrophysics Data System (ADS)

Fraine, Jonathan D.; Deming, Drake; Jordan, Andres; Knutson, Heather

2015-01-01

The detections and non-detections of molecular species in transiting planets-- such as water, methane, and carbon monoxide-- lead to greater understanding of planet formation and evolution. Recent significant advances in both theoretical and observational discoveries from planets like HD189733b, HD209458b, GJ436b, as well as our own work with HAT-P-11b and GJ1214b, have shown that the range of measurable atmospheric properties spans from clear, molecular absorption dominated worlds to opaque worlds, with cloudy, hazy, or high mean molecular weight atmospheres. Characterization of significant non-detections allowed us to infer the existence of opaque cloud layers at very high altitudes or mean molecular weights upwards of ~1000x solar. The prevalence of these atmospheres was unexpected from extrapolations of solar system analogs. I will present our published results from GJ1214b and HAT-P-11b, as well as our recent work using both Spitzer and Magellan. Our results, combined with transmission spectra obtained for other similar planets, connect to develop a better understanding about the nature of these distant and alien worlds

New worlds on the horizon: Earth-sized planets close to other stars.

PubMed

Gaidos, Eric; Haghighipour, Nader; Agol, Eric; Latham, David; Raymond, Sean; Rayner, John

2007-10-12

The search for habitable planets like Earth around other stars fulfills an ancient imperative to understand our origins and place in the cosmos. The past decade has seen the discovery of hundreds of planets, but nearly all are gas giants like Jupiter and Saturn. Recent advances in instrumentation and new missions are extending searches to planets the size of Earth but closer to their host stars. There are several possible ways such planets could form, and future observations will soon test those theories. Many of these planets we discover may be quite unlike Earth in their surface temperature and composition, but their study will nonetheless inform us about the process of planet formation and the frequency of Earth-like planets around other stars.

The Backyard Worlds: Planet 9 Citizen Science Project

NASA Astrophysics Data System (ADS)

Faherty, Jacqueline K.; Kuchner, Marc; Schneider, Adam; Meisner, Aaron; Gagné, Jonathan; Filippazzo, Joeseph; Trouille, Laura; Backyard Worlds: Planet 9 Collaboration; Jacqueline Faherty

2018-01-01

In February of 2017 our team launched a new citizen science project entitled Backyard Worlds: Planet 9 to scan the cosmos for fast moving stars, brown dwarfs, and even planets. This Zooniverse website, BackyardWorlds.org, invites anyone with a computer or smartphone to flip through WISE images taken over a several year baseline and mark any point source that appears to move. This “blinking technique” is the same that Clyde Tombaugh discovered Pluto with over 80 years ago. In the first few days of our program we recruited over 30,000 volunteers. After 3/4 of a year with the program we have completed 30% of the sky and our participants have identified several hundred candidate movers. These include (1) over 20 candidate Y-type brown dwarfs, (2) a handful of new co-moving systems containing a previously unidentified low mass object and a known nearby star, (3) over 100 previously missed M dwarfs, (4) and more than 200 candidate L and T brown dwarfs, many of which occupy outlier positions on reduced proper motion diagrams. Our first publication credited four citizen scientists as co-authors. The Backyard Worlds: Planet 9 project is both scientifically fruitful and empowering for any mind across the globe that has ever wanted to participate in a discovery-driven astronomy research project.

Early Earth(s) Across Time and Space

NASA Astrophysics Data System (ADS)

Mojzsis, S.

2014-04-01

The geochemical and cosmochemical record of our solar system is the baseline for exploring the question: "when could life appear on a world similar to our own?" Data arising from direct analysis of the oldest terrestrial rocks and minerals from the first 500 Myr of Earth history - termed the Hadean Eon - inform us about the timing for the establishment of a habitable silicate world. Liquid water is the key medium for life. The origin of water, and its interaction with the crust as revealed in the geologic record, guides our exploration for a cosmochemically Earth-like planets. From the time of primary planetary accretion to the start of the continuous rock record on Earth at ca. 3850 million years ago, our planet experienced a waning bolide flux that partially or entirely wiped out surface rocks, vaporized oceans, and created transient serpentinizing atmospheres. Arguably, "Early Earths" across the galaxy may start off as ice planets due to feeble insolation from their young stars, occasionally punctuated by steam atmospheres generated by cataclysmic impacts. Alternatively, early global environments conducive to life spanned from a benign surface zone to deep into crustal rocks and sediments. In some scenarios, nascent biospheres benefit from the exogenous delivery of essential bio-elements via leftovers of accretion, and the subsequent establishment of planetary-scale hydrothermal systems. If what is now known about the early dynamical regime of the Earth serves as any measure of the potential habitability of worlds across space and time, several key boundary conditions emerge. These are: (i) availability and long-term stability of liquid water; (ii) presence of energy resources; (iii) accessibility of organic raw materials; (iv) adequate inventory of radioisotopes to drive internal heating; (v) gross compositional parameters such as mantle/core mass ratio, and (vi) P-T conditions at or near the surface suitable for sustaining biological activity. Life could emerge in or on a suitable planet with Earth characteristics, within ca. 150 Myr after its formation. Our understanding of the thermal histories and chemical transformations of the crusts of early Earth, Moon, Mars and asteroids have accumulated to the point where it is now feasible to deduce the habitable potential of the early solar system and to place some upward constraints on the timing of life's appearance. The natural lifetime of a biosphere is strongly dependent not simply on its proximity to its star, but on the age and composition of the host planet.

Eccentricities and Inclinations of Multi-Planet Systems with External Perturbers

NASA Astrophysics Data System (ADS)

Pu, Bonan; Lai, Dong

2018-05-01

Compact multi-planet systems containing super-Earths or sub-Neptunes, commonly found around solar-type stars, may be surrounded by external giant planet or stellar companions, which can shape the architechture and observability of the inner systems. We present a comprehensive study on the evolution of the inner planetary system subject to the gravitational influence of an eccentric, misaligned outer perturber. Analytic results are derived for the inner planet eccentricities (ei) and mutual inclination (θ12) of the "2-planet + perturber" system, calibrated with numerical secular and N-body integrations, as a function of the perturber mass mp, semi-major axis ap and inclination angle θp. We find that the dynamics of the inner system is determined by the dimensionless parameter ɛ12, given by the ratio between the differential precession rate driven by the perturber and the mutual precession rate of the inner planets. Loosely packed systems (corresponding to ɛ12 ≫ 1) are more susceptible to eccentricity/inclination excitations by the perturber than tightly packed inner systems (with ɛ12 ≪ 1) (or singletons), although resonance may occur around ɛ12 ˜ 1, leading to large ei and θ12. Dynamical instability may set in for inner planet systems with large excited eccentricities and mutual inclinations. We present a formalism to extend our analytical results to general inner systems with N > 2 planets and apply our results to constrain possible external companions to the Kepler-11 system. Eccentricity and inclination excitation by external companions may help explain the observational trend that systems with fewer transiting planets are dynamically hotter than those with more transiting planets.

Statistical and dynamical remastering of classic exoplanet systems

NASA Astrophysics Data System (ADS)

Nelson, Benjamin Earl

The most powerful constraints on planet formation will come from characterizing the dynamical state of complex multi-planet systems. Unfortunately, with that complexity comes a number of factors that make analyzing these systems a computationally challenging endeavor: the sheer number of model parameters, a wonky shaped posterior distribution, and hundreds to thousands of time series measurements. In this dissertation, I will review our efforts to improve the statistical analyses of radial velocity (RV) data and their applications to some renown, dynamically complex exoplanet system. In the first project (Chapters 2 and 4), we develop a differential evolution Markov chain Monte Carlo (RUN DMC) algorithm to tackle the aforementioned difficult aspects of data analysis. We test the robustness of the algorithm in regards to the number of modeled planets (model dimensionality) and increasing dynamical strength. We apply RUN DMC to a couple classic multi-planet systems and one highly debated system from radial velocity surveys. In the second project (Chapter 5), we analyze RV data of 55 Cancri, a wide binary system known to harbor five planetary orbiting the primary. We find the inner-most planet "e" must be coplanar to within 40 degrees of the outer planets, otherwise Kozai-like perturbations will cause the planet to enter the stellar photosphere through its periastron passage. We find the orbits of planets "b" and "c" are apsidally aligned and librating with low to median amplitude (50+/-6 10 degrees), but they are not orbiting in a mean-motion resonance. In the third project (Chapters 3, 4, 6), we analyze RV data of Gliese 876, a four planet system with three participating in a multi-body resonance, i.e. a Laplace resonance. From a combined observational and statistical analysis computing Bayes factors, we find a four-planet model is favored over one with three-planets. Conditioned on this preferred model, we meaningfully constrain the three-dimensional orbital architecture of all the planets orbiting Gliese 876 based on the radial velocity data alone. By demanding orbital stability, we find the resonant planets have low mutual inclinations phi so they must be roughly coplanar (phicb = 1.41(+/-0.62/0.57) degrees and phibe = 3.87(+/-1.99/1.86 degrees). The three-dimensional Laplace argument librates chaotically with an amplitude of 50.5(+/-7.9/10.0) degrees, indicating significant past disk migration and ensuring long-term stability. In the final project (Chapter 7), we analyze the RV data for nu Octantis, a closely separated binary with an alleged planet orbiting interior and retrograde to the binary. Preliminary results place very tight constraints on the planet-binary mutual inclination but no model is dynamically stable beyond 105 years. These empirically derived models motivate the need for more sophisticated algorithms to analyze exoplanet data and will provide new challenges for planet formation models.

Modelling the dynamics of a hypothetical Planet X by way of gravitational N-body simulator

NASA Astrophysics Data System (ADS)

Cowley, Michael; Hughes, Stephen

2017-03-01

This paper describes a novel activity to model the dynamics of a Jupiter-mass, trans-Neptunian planet of a highly eccentric orbit. Despite a history rooted in modern astronomy, ‘Planet X’, a hypothesised hidden planet lurking in our outer Solar System, has often been touted by conspiracy theorists as the cause of past mass extinction events on Earth, as well as other modern-day doomsday scenarios. Frequently dismissed as pseudoscience by astronomers, these stories continue to draw the attention of the public by provoking mass media coverage. Targeted at junior undergraduate levels, this activity allows students to debunk some of the myths surrounding Planet X by using simulation software to demonstrate that such a large-mass planet with extreme eccentricity would be unable to enter our Solar System unnoticed, let alone maintain a stable orbit.

Dynamical Evolution and Spin-Orbit Resonances of Potentially Habitable Exoplanets: The Case of GJ 581d

NASA Astrophysics Data System (ADS)

Makarov, Valeri V.; Berghea, Ciprian; Efroimsky, Michael

2012-12-01

GJ 581d is a potentially habitable super-Earth in the multiple system of exoplanets orbiting a nearby M dwarf. We investigate this planet's long-term dynamics with an emphasis on its probable final rotation states acquired via tidal interaction with the host. The published radial velocities for the star are re-analyzed with a benchmark planet detection algorithm to confirm that there is no evidence for the recently proposed two additional planets (f and g). Limiting the scope to the four originally detected planets, we assess the dynamical stability of the system and find bounded chaos in the orbital motion. For the planet d, the characteristic Lyapunov time is 38 yr. Long-term numerical integration reveals that the system of four planets is stable, with the eccentricity of the planet d changing quasi-periodically in a tight range around 0.27, and with its semimajor axis varying only a little. The spin-orbit interaction of GJ 581d with its host star is dominated by the tides exerted by the star on the planet. We model this interaction, assuming a terrestrial composition of the mantle. Besides the triaxiality-caused torque and the secular part of the tidal torque, which are conventionally included in the equation of motion, we also include the tidal torques' oscillating components. It turns out that, depending on the mantle temperature, the planet gets trapped into the 2:1 or an even higher spin-orbit resonance. It is very improbable that the planet could have reached the 1:1 resonance. This improves the possibility of the planet being suitable for sustained life.

The Dynamics and Implications of Gap Clearing via Planets in Planetesimal (Debris) Disks

NASA Astrophysics Data System (ADS)

Morrison, Sarah Jane

Exoplanets and debris disks are examples of solar systems other than our own. As the dusty reservoirs of colliding planetesimals, debris disks provide indicators of planetary system evolution on orbital distance scales beyond those probed by the most prolific exoplanet detection methods, and on timescales 10 r to 10 Gyr. The Solar System possesses both planets and small bodies, and through studying the gravitational interactions between both, we gain insight into the Solar System's past. As we enter the era of resolved observations of debris disks residing around other stars, I add to our theoretical understanding of the dynamical interactions between debris, planets, and combinations thereof. I quantify how single planets clear material in their vicinity and how long this process takes for the entire planetary mass regime. I use these relationships to assess the lowest mass planet that could clear a gap in observed debris disks over the system's lifetime. In the distant outer reaches of gaps in young debris systems, this minimum planet mass can exceed Neptune's. To complement the discoveries of wide-orbit, massive, exoplanets by direct imaging surveys, I assess the dynamical stability of high mass multi-planet systems to estimate how many high mass planets could be packed into young, gapped debris disks. I compare these expectations to the planet detection rates of direct imaging surveys and find that high mass planets are not the primary culprits for forming gaps in young debris disk systems. As an alternative model for forming gaps in planetesimal disks with planets, I assess the efficacy of creating gaps with divergently migrating pairs of planets. I find that migrating planets could produce observed gaps and elude detection. Moreover, the inferred planet masses when neglecting migration for such gaps could be expected to be observable by direct imaging surveys for young, nearby systems. Wide gaps in young systems would likely still require more than two planets even with plantesimal-driven migration. These efforts begin to probe the types of potential planets carving gaps in disks of different evolutionary stages and at wide orbit separations on scales similar to our outer Solar System.

Remote Thermal IR Spectroscopy of our Solar System

NASA Technical Reports Server (NTRS)

Kostiuk, Theodor; Hewagama, Tilak; Goldstein, Jeffrey; Livengood, Timothy; Fast, Kelly

1999-01-01

Indirect methods to detect extrasolar planets have been successful in identifying a number of stars with companion planets. No direct detection of an extrasolar planet has yet been reported. Spectroscopy in the thermal infrared region provides a potentially powerful approach to detection and characterization of planets and planetary systems. We can use knowledge of our own solar system, its planets and their atmospheres to model spectral characteristics of planets around other stars. Spectra derived from modeling our own solar system seen from an extrasolar perspective can be used to constrain detection strategies, identification of planetary class (terrestrial vs. gaseous) and retrieval of chemical, thermal and dynamical information. Emission from planets in our solar system peaks in the thermal infrared region, approximately 10 - 30 microns, substantially displaced from the maximum of the much brighter solar emission in the visible near 0.5 microns. This fact provides a relatively good contrast ratio to discriminate between stellar (solar) and planetary emission and optimize the delectability of planetary spectra. Important molecular constituents in planetary atmospheres have rotational-vibrational spectra in the thermal infrared region. Spectra from these molecules have been well characterized in the laboratory and studied in the atmospheres of solar system planets from ground-based and space platforms. The best example of such measurements are the studies with Fourier transform spectrometers, the Infrared Interferometer Spectrometers (IRIS), from spacecraft: Earth observed from NIMBUS 8, Mars observed from Mariner 9, and the outer planets observed from Voyager spacecraft. An Earth-like planet is characterized by atmospheric spectra of ozone, carbon dioxide, and water. Terrestrial planets have oxidizing atmospheres which are easily distinguished from reducing atmospheres of gaseous giant planets which lack oxygen-bearing species and are characterized by spectra containing hydrocarbons such as methane and ethane. Spectroscopic information on extrasolar planets thus can permit their classification. Spectra and spectral lines contain information on the temperature structure of the atmosphere. Line and band spectra can be used to identify the molecular constituents and retrieve species abundances, thereby classifying and characterizing the planet. At high enough spectral resolution characteristic planetary atmospheric dynamics and unique phenomena such as failure of local thermodynamic equilibrium can be identified. Dynamically induced effects such as planetary rotation and orbital velocity shift and change the shape of spectral features and must be modeled in detailed spectral studies. We will use our knowledge of the compositional, thermal and dynamical characteristics of planetary atmospheres in our own solar system to model spectra observed remotely on similar planets in extrasolar planetary systems. We will use a detailed radiative transfer and beam integration program developed for the modeling and interpretation of thermal infrared spectra measured from nearby planet planets to generate models of an extra-solar "Earth" and "Jupiter". From these models we will show how key spectral features distinguish between terrestrial and gaseous planets, what information can be obtained with different spectral resolution, what spectral features can be used to search for conditions for biogenic activity, and how dynamics and distance modify the observed spectra. We also will look at unique planetary phenomena such as atmospheric lasing and discuss their utility as probes for detection and identification of planets. Results of such studies will provide information to constrain design for instrumentation needed to directly detect extrasolar planets.

TRANSIT TIMING OBSERVATIONS FROM KEPLER. I. STATISTICAL ANALYSIS OF THE FIRST FOUR MONTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ford, Eric B.; Rowe, Jason F.; Caldwell, Douglas A.

The architectures of multiple planet systems can provide valuable constraints on models of planet formation, including orbital migration, and excitation of orbital eccentricities and inclinations. NASA's Kepler mission has identified 1235 transiting planet candidates. The method of transit timing variations (TTVs) has already confirmed seven planets in two planetary systems. We perform a transit timing analysis of the Kepler planet candidates. We find that at least {approx}11% of planet candidates currently suitable for TTV analysis show evidence suggestive of TTVs, representing at least {approx}65 TTV candidates. In all cases, the time span of observations must increase for TTVs to providemore » strong constraints on planet masses and/or orbits, as expected based on N-body integrations of multiple transiting planet candidate systems (assuming circular and coplanar orbits). We find the fraction of planet candidates showing TTVs in this data set does not vary significantly with the number of transiting planet candidates per star, suggesting significant mutual inclinations and that many stars with a single transiting planet should host additional non-transiting planets. We anticipate that Kepler could confirm (or reject) at least {approx}12 systems with multiple transiting planet candidates via TTVs. Thus, TTVs will provide a powerful tool for confirming transiting planets and characterizing the orbital dynamics of low-mass planets. If Kepler observations were extended to at least seven years, then TTVs would provide much more precise constraints on the dynamics of systems with multiple transiting planets and would become sensitive to planets with orbital periods extending into the habitable zone of solar-type stars.« less

Predicting Precession Rates from Secular Dynamics for Extra-solar Multi-planet Systems

NASA Astrophysics Data System (ADS)

Van Laerhoven, Christa

2015-12-01

Considering the secular dynamics of multi-planet systems provides substantial insight into the interactions between planets in those systems. Secular interactions are those that don't involve knowing where a planet is along its orbit, and they dominate when planets are not involved in mean motion resonances. These interactions exchange angular momentum among the planets, evolving their eccentricities and inclinations. To second order in the planets' eccentricities and inclinations, the eccentricity and inclination perturbations are decoupled. Given the right variable choice, the relevant differential equations are linear and thus the eccentricity and inclination behaviors can be described as a sum of eigenmodes. Since the underlying structure of the secular eigenmodes can be calculated using only the planets' masses and semi-major axes, one can elucidate the eccentricity and inclination behavior of planets in exoplanet systems even without knowing the planets' current eccentricities and inclinations. I have calculated both the eccentricity and inclination secular eigenmodes for the population of known multi-planet systems whose planets have well determined masses and periods and have used this to predict what range of pericenter precession (and nodal regression) rates the planets may have. One might have assumed that in any given system the planets with shorter periods would have faster precession rates, but I show that this is not necessarily the case. Planets that are 'loners' have narrow ranges of possible precession rates, while planets that are 'groupies' can have a wider range of possible precession rates. Several planets are expected to undergo significant precession on few-year timescales and many planets (though not the majority of planets) will undergo significant precession on decade timescales.

Long-Period Planets in Open Clusters and the Evolution of Planetary Systems

NASA Astrophysics Data System (ADS)

Quinn, Samuel N.; White, Russel; Latham, David W.; Stefanik, Robert

2018-01-01

Recent discoveries of giant planets in open clusters confirm that they do form and migrate in relatively dense stellar groups, though overall occurrence rates are not yet well constrained because the small sample of giant planets discovered thus far predominantly have short periods. Moreover, planet formation rates and the architectures of planetary systems in clusters may vary significantly -- e.g., due to intercluster differences in the chemical properties that regulate the growth of planetary embryos or in the stellar space density and binary populations, which can influence the dynamical evolution of planetary systems. Constraints on the population of long-period Jovian planets -- those representing the reservoir from which many hot Jupiters likely form, and which are most vulnerable to intracluster dynamical interactions -- can help quantify how the birth environment affects formation and evolution, particularly through comparison of populations possessing a range of ages and chemical and dynamical properties. From our ongoing RV survey of open clusters, we present the discovery of several long-period planets and candidate substellar companions in the Praesepe, Coma Berenices, and Hyades open clusters. From these discoveries, we improve estimates of giant planet occurrence rates in clusters, and we note that high eccentricities in several of these systems support the prediction that the birth environment helps shape planetary system architectures.

10 years with Planet Earth essence in the primary school children drawings

NASA Astrophysics Data System (ADS)

D'Addezio, Giuliana

2016-04-01

"10 years with Planet Earth" is the title of the 2016 INGV calendar for primary schools representing the review of a project conceived as support and complement of 15 years long INGV dissemination activities with schools. We realized 10 calendars together with and for primary schools, every year with a subject related to a World in constant evolution. Earthquakes, volcanic eruptions, tsunami waves, magnetic storms and other phenomena are manifestations of the complexity and dynamicity, which began more than four billion years ago and never halted. Since the Earth originated to the first presence of water, life and oxygen, the Cambrian explosion of species, the domain of dinosaurs, the great extinctions and glaciations, the surface of our planet experiences continents collisions, mountains and oceans formation and life forms emerging and disappearing. Every year we have launched a competition asking children to send drawings on themes chosen to stimulate learning about Earth Sciences and Planet Earth dynamics. We intended to raise awareness on issues as water resources availability, protection against natural disasters and control of environmental degradation. For each competition, we chose the most significant drawings to be included in the yearly calendar about the Earth. The authors of drawings were awarded by scientists, journalists, artists and science communicators and even by a minister. Besides the competitions, these drawings depict their own impressions and reflections, providing an opportunity to illustrate the children's point of view. From drawings and texts arise a great consideration and respect for the Planet, raising hopes that similar initiatives can contribute to increase the knowledge of the Earth and of the fragile human ecosystem in the hearts and minds of future active citizens. The project was made possible thanks to the teachers and to the wonderful students of more than 200 schools that sent about 10,000 drawings that have intrigued, touched, enchanted, and surprised us. In the 2016 calendar we have collected the drawings chosen as the cover for each of the past years calendar dedicated to the Earth.

Rocky Worlds Limited to ∼1.8 Earth Radii by Atmospheric Escape during a Star’s Extreme UV Saturation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehmer, Owen R.; Catling, David C., E-mail: info@lehmer.us

Recent observations and analysis of low-mass (<10 M {sub ⊕}) exoplanets have found that rocky planets only have radii up to 1.5–2 R {sub ⊕}. Two general hypotheses exist for the cause of the dichotomy between rocky and gas-enveloped planets (or possible water worlds): either low-mass planets do not necessarily form thick atmospheres of a few wt.%, or the thick atmospheres on these planets easily escape, driven by X-ray and extreme ultraviolet (XUV) emissions from young parent stars. Here, we show that a cutoff between rocky and gas-enveloped planets due to hydrodynamic escape is most likely to occur at amore » mean radius of 1.76 ± 0.38 (2 σ ) R {sub ⊕} around Sun-like stars. We examine the limit in rocky planet radii predicted by hydrodynamic escape across a wide range of possible model inputs, using 10,000 parameter combinations drawn randomly from plausible parameter ranges. We find a cutoff between rocky and gas-enveloped planets that agrees with the observed cutoff. The large cross-section available for XUV absorption in the extremely distended primitive atmospheres of low-mass planets results in complete loss of atmospheres during the ∼100 Myr phase of stellar XUV saturation. In contrast, more-massive planets have less-distended atmospheres and less escape, and so retain thick atmospheres through XUV saturation—and then indefinitely as the XUV and escape fluxes drop over time. The agreement between our model and exoplanet data leads us to conclude that hydrodynamic escape plausibly explains the observed upper limit on rocky planet size and few planets (a “valley”, or “radius gap”) in the 1.5–2 R {sub ⊕} range.« less

The formation of co-orbital planets and their resulting transit signatures

NASA Astrophysics Data System (ADS)

Granados Contreras, Agueda Paula; Boley, Aaron

2018-04-01

Systems with Tightly-packed Inner Planets (STIPs) are metastable, exhibiting sudden transitions to an unstable state that can potentially lead to planet consolidation. When these systems are embedded in a gaseous disc, planet-disc interactions can significantly reduce the frequency of instabilities, and if they do occur, disc torques alter the dynamical outcomes. We ran a suite of N-body simulations of synthetic 6-planet STIPs using an independent implementation of IAS15 that includes a prescription for gaseous tidal damping. The algorithm is based on the results of disc simulations that self-consistently evolve gas and planets. Even for very compact configurations, the STIPS are resistant to instability when gas is present. However, instability can still occur, and in some cases, the combination of system instability and gaseous damping leads to the formation of co-orbiting planets that are stable even when gas damping is removed. While rare, such systems should be detectable in transit surveys, although the dynamics of the system can make the transit signature difficult to identify.

RESONANCES REQUIRED: DYNAMICAL ANALYSIS OF THE 24 Sex AND HD 200964 PLANETARY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G., E-mail: rob@phys.unsw.edu.au

We perform several suites of highly detailed dynamical simulations to investigate the architectures of the 24 Sextantis and HD 200964 planetary systems. The best-fit orbital solution for the two planets in the 24 Sex system places them on orbits with periods that lie very close to 2:1 commensurability, while that for the HD 200964 system places the two planets therein in orbits whose periods lie close to a 4:3 commensurability. In both cases, the proposed best-fit orbits are mutually crossing-a scenario that is only dynamically feasible if the planets are protected from close encounters by the effects of mutual mean-motionmore » resonance (MMR). Our simulations reveal that the best-fit orbits for both systems lie within narrow islands of dynamical stability, and are surrounded by much larger regions of extreme instability. As such, we show that the planets are only feasible if they are currently trapped in mutual MMR-the 2:1 resonance in the case of 24 Sex b and c, and the 4:3 resonance in the case of HD 200964 b and c. In both cases, the region of stability is strongest and most pronounced when the planetary orbits are mutually coplanar. As the inclination of planet c with respect to planet b is increased, the stability of both systems rapidly collapses.« less

Dynamical habitability of planetary systems.

PubMed

Dvorak, Rudolf; Pilat-Lohinger, Elke; Bois, Eric; Schwarz, Richard; Funk, Barbara; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Lammer, Helmut; Léger, Alain; Liseau, René; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

2010-01-01

The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries).

The New Worlds Observer: A New Approach to Observing Extrasolar Planets

NASA Astrophysics Data System (ADS)

Cash, W.; Wilkinson, E.; Green, J.; Kasdin, J.; Spergel, D.; Turner, E.; Vanderbei, R.; Seager, S.; Stern, A.; Kilston, S.; Leiber, J.

2003-12-01

Direct observation of planets around other stars has been hindered primarily by the spatial proximity of their parent stars. Diffraction and scattering swamp the signal from the planet, which is typically billions of times fainter. We present an approach which has the potential to sidestep these problems. The New Worlds Observer was proposed to NASA last summer for a concept study as a Life Finder Mission to perform spectroscopy of terrestrial planets at 10pc. It consists of two spacecraft separated by 180,00km. The first craft, the starshade, features a deployable dark sheet hundreds of meters across and an aperture approximately 10m in diameter, specially shaped to suppress diffraction. At the focal plane of this pinhole camera flies a 10m diameter, one arcsecond quality Cassegrain telescope. If the telescope is placed where the pinhole image of a planet falls, the diffracted light from the star is suppressed, so only planet light enters the telescope. This system will allow sensitive observations anywhere from the far ultraviolet to the near infrared. Accompanying posters at this meeting will present science simulations and more details on the starshade design.

Worlds on the Edge Artist Concept

NASA Image and Video Library

2010-08-26

This artist concept illustrates the two Saturn-sized planets discovered by NASA Kepler mission. The star system is oriented edge-on, as seen by Kepler, such that both planets cross in front, or transit, their star, named Kepler-9.

A SEARCH FOR MULTI-PLANET SYSTEMS USING THE HOBBY-EBERLY TELESCOPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittenmyer, Robert A.; Endl, Michael; Cochran, William D.

Extrasolar multiple-planet systems provide valuable opportunities for testing theories of planet formation and evolution. The architectures of the known multiple-planet systems demonstrate a fascinating level of diversity, which motivates the search for additional examples of such systems in order to better constrain their formation and dynamical histories. Here we describe a comprehensive investigation of 22 planetary systems in an effort to answer three questions: (1) are there additional planets? (2) where could additional planets reside in stable orbits? and (3) what limits can these observations place on such objects? We find no evidence for additional bodies in any of thesemore » systems; indeed, these new data do not support three previously announced planets (HD 20367 b: Udry et al.; HD 74156 d: Bean et al.; and 47 UMa c: Fischer et al.). The dynamical simulations show that nearly all of the 22 systems have large regions in which additional planets could exist in stable orbits. The detection-limit computations indicate that this study is sensitive to close-in Neptune-mass planets for most of the systems targeted. We conclude with a discussion on the implications of these nondetections.« less

Compositional Constraints on the Best Characterized Rocky Exoplanet, Kepler-36 b

NASA Astrophysics Data System (ADS)

Rogers, Leslie; Deck, Katherine; Lissauer, Jack J.; Carter, Joshua A.

2015-01-01

Kepler-36 is an extreme planetary system, consisting of two transiting sub-Neptune-size planets that revolve around a sub-giant star with orbital periods of 13.84 and 16.24 days. Mutual gravitational interactions between the two planets perturb the planets' transit times, allowing the planets' masses to be measured. Despite the similarity of their masses and orbital radii, the planets show a stark contrast in their mean densities; the inner planet (Kepler-36 b) is more than eight times as dense as its outer companion planet (Kepler-36 c). We perform a photo-dynamical analysis of the Kepler-36 system based on more than three years of Kepler photometry. With N-body integrations of initial conditions sampled from the photo-dynamical fits, we further refine the properties of the system by ruling out solutions that show large-scale instability within 5 Giga-days. Ultimately, we measure the planets' masses within 4.2% precision, and the planets' radii with 1.8% precision. Kepler-36 b is currently the rocky exoplanet with the most precisely measured mass and radius. Kepler-36 b's mass and radius are consistent with an Earth-like composition, and an iron-enhanced Mercury-like composition is ruled out.

Compositional Constraints on the Best Characterized Rocky Exoplanet, Kepler-36 b

NASA Astrophysics Data System (ADS)

Rogers, Leslie Anne; Deck, Katherine; Lissauer, Jack; Carter, Joshua

2015-08-01

Kepler-36 is an extreme planetary system, consisting of two transiting sub-Neptune-size planets that revolve around a sub-giant star with orbital periods of 13.84 and 16.24 days. Mutual gravitational interactions between the two planets perturb the planets' transit times, allowing the planets' masses to be measured. Despite the similarity of their masses and orbital radii, the planets show a stark contrast in their mean densities; the inner planet (Kepler-36 b) is more than eight times as dense as its outer companion planet (Kepler-36 c). We perform a photo-dynamical analysis of the Kepler-36 system based on more than three years of Kepler photometry. With N-body integrations of initial conditions sampled from the photo-dynamical fits, we further refine the properties of the system by ruling out solutions that show large scale instability within 5 Giga-days. Ultimately, we measure the planets' masses within 4.2% precision, and the planets' radii with 1.8% precision. Kepler-36 b is currently the rocky exoplanet with the most precisely measured mass and radius. Kepler-36 b’s mass and radius are consistent with a Earth-like composition, and an iron-enhanced Mercury-like composition is ruled out.

Compositional Constraints on the Best Characterized Rocky Exoplanet, Kepler-36 b

NASA Astrophysics Data System (ADS)

Rogers, L.; Deck, K.; Lissauer, J. J.; Carter, J.

2014-12-01

Kepler-36 is an extreme planetary system, consisting of two transiting sub-Neptune-size planets that revolve around a sub-giant star with orbital periods of 13.84 and 16.24 days. Mutual gravitational interactions between the two planets perturb the planets' transit times, allowing the planets' masses to be measured. Despite the similarity of their masses and orbital radii, the planets show a stark contrast in their mean densities; the inner planet (Kepler-36 b) is more than eight times as dense as its outer companion planet (Kepler-36 c). We perform a photo-dynamical analysis of the Kepler-36 system based on more than three years of Kepler photometry. With N-body integrations of initial conditions sampled from the photo-dynamical fits, we further refine the properties of the system by ruling out solutions that show large scale instability within 5 Giga-days. Ultimately, we measure the planets' masses within 4.2% precision, and the planets' radii with 1.8% precision. Kepler-36 b is currently the rocky exoplanet with the most precisely measured mass and radius. Kepler-36 b's mass and radius are consistent with a Earth-like composition, and an iron-enhanced Mercury-like composition is ruled out.

The fate of scattered planets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

2014-12-01

As gas giant planets evolve, they may scatter other planets far from their original orbits to produce hot Jupiters or rogue planets that are not gravitationally bound to any star. Here, we consider planets cast out to large orbital distances on eccentric, bound orbits through a gaseous disk. With simple numerical models, we show that super-Earths can interact with the gas through dynamical friction to settle in the remote outer regions of a planetary system. Outcomes depend on planet mass, the initial scattered orbit, and the evolution of the time-dependent disk. Efficient orbital damping by dynamical friction requires planets atmore » least as massive as the Earth. More massive, longer-lived disks damp eccentricities more efficiently than less massive, short-lived ones. Transition disks with an expanding inner cavity can circularize orbits at larger distances than disks that experience a global (homologous) decay in surface density. Thus, orbits of remote planets may reveal the evolutionary history of their primordial gas disks. A remote planet with an orbital distance ∼100 AU from the Sun is plausible and might explain correlations in the orbital parameters of several distant trans-Neptunian objects.« less

About the Linguistic Impossibility of Claiming that Small Planets are not Planets

NASA Astrophysics Data System (ADS)

Nedeljkovic, A. B.

2012-12-01

Philology, which is, the science of language and literature, must now offer assistance to the science of astronomy, about one question of terminology and logic. Namely, if something belongs to one category, then it is, regardless of its size (large, or medium, or small) a member of that category. Therefore, it was linguistically wrong to claim that Pluto is one of the dwarf planets and therefore not a planet. This mistake, much noticed by the world's public opinion, ought to be corrected immediately.

NASA's Kepler Mission Discovers Its Smallest Habitable Zone Planets (Reporter Pkg)

NASA Image and Video Library

2013-04-18

NASA's Kepler mission has discovered two new planetary systems that include three super-Earth-size planets in the 'habitable zone,' the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Scientists do not know whether life could exist on the newfound planets, but their discovery signals we are another step closer to finding a world similar to Earth around a star like our sun. Kepler-62 and -69 systems

Statistical Study of the Early Solar System's Instability with Four, Five, and Six Giant Planets

NASA Astrophysics Data System (ADS)

Nesvorný, David; Morbidelli, Alessandro

2012-10-01

Several properties of the solar system, including the wide radial spacing and orbital eccentricities of giant planets, can be explained if the early solar system evolved through a dynamical instability followed by migration of planets in the planetesimal disk. Here we report the results of a statistical study, in which we performed nearly 104 numerical simulations of planetary instability starting from hundreds of different initial conditions. We found that the dynamical evolution is typically too violent, if Jupiter and Saturn start in the 3:2 resonance, leading to ejection of at least one ice giant from the solar system. Planet ejection can be avoided if the mass of the transplanetary disk of planetesimals was large (M disk >~ 50 M Earth), but we found that a massive disk would lead to excessive dynamical damping (e.g., final e 55 <~ 0.01 compared to present e 55 = 0.044, where e 55 is the amplitude of the fifth eccentric mode in the Jupiter's orbit), and to smooth migration that violates constraints from the survival of the terrestrial planets. Better results were obtained when the solar system was assumed to have five giant planets initially, and one ice giant, with mass comparable to that of Uranus and Neptune, was ejected into interstellar space by Jupiter. The best results were obtained when the ejected planet was placed into the external 3:2 or 4:3 resonance with Saturn and M disk ~= 20 M Earth. The range of possible outcomes is rather broad in this case, indicating that the present solar system is neither a typical nor expected result for a given initial state, and occurs, in best cases, with only a sime5% probability (as defined by the success criteria described in the main text). The case with six giant planets shows interesting dynamics but does offer significant advantages relative to the five-planet case.

Astronomers Find World with Thick, Inhospitable Atmosphere and an Icy Heart

NASA Astrophysics Data System (ADS)

2009-12-01

Astronomers have discovered the second super-Earth exoplanet [1] for which they have determined the mass and radius, giving vital clues about its structure. It is also the first super-Earth where an atmosphere has been found. The exoplanet, orbiting a small star only 40 light-years away from us, opens up dramatic new perspectives in the quest for habitable worlds. The planet, GJ1214b, has a mass about six times that of Earth and its interior is likely to be mostly made of water ice. Its surface appears to be fairly hot and the planet is surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth. In this week's issue of Nature, astronomers announce the discovery of a planet around the nearby, low-mass star GJ1214 [2]. It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b [3]. A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star. The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune. Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron. GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres - 70 times closer to its star than the Earth is to the Sun. "Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid," says David Charbonneau, lead author of the paper reporting the discovery. When the astronomers compared the measured radius of GJ1214b with theoretical models of planets, they found that the observed radius exceeds the models' predictions: there is something more than the planet's solid surface blocking the star's light - a surrounding atmosphere, 200 km thick. "This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it," says Charbonneau, "but these conditions are still very interesting, as they could allow for some complex chemistry to take place." "Because the planet is too hot to have kept an atmosphere for long, GJ1214b represents the first opportunity to study a newly formed atmosphere enshrouding a world orbiting another star," adds team member Xavier Bonfils. "Because the planet is so close to us, it will be possible to study its atmosphere even with current facilities." The planet was first discovered as a transiting object within the MEarth project, which follows about 2000 low-mass stars to look for transits by exoplanets [4]. To confirm the planetary nature of GJ1214b and to obtain its mass (using the so-called Doppler method), the astronomers needed the full precision of the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla. An instrument with unrivalled stability and great precision, HARPS is the world's most successful hunter for small exoplanets. "This is the second super-Earth exoplanet for which the mass and radius could be obtained, allowing us to determine the density and to infer the inner structure," adds co-author Stephane Udry. "In both cases, data from HARPS was essential to characterise the planet." "The differences in composition between these two planets are relevant to the quest for habitable worlds," concludes Charbonneau. If super-Earth planets in general are surrounded by an atmosphere similar to that of GJ1214b, they may well be inhospitable to the development of life as we know it on our own planet. Notes [1] A super-Earth is defined as a planet between one and ten times the mass of the Earth. An exoplanet is a planet orbiting a star other than the Sun. [2] The star GJ1214 is five times smaller than our Sun and intrinsically three hundred times less bright. [3] Corot-7b is the smallest and fastest-orbiting exoplanet known and has a density quite similar to the Earth's, suggesting a solid, rocky world. Discovered by the CoRoT satellite as a transiting object, its true nature was revealed by HARPS (eso0933). [4] The MEarth project uses an armada of eight small telescopes each with a diameter of 40 cm, located on top of Mount Hopkins, Arizona, USA. MEarth looks for stars that change brightness. The goal is to find a planet that crosses in front of, or transits, its star. During such a mini-eclipse, the planet blocks a small portion of the star's light, making it dimmer. NASA's Kepler mission also uses transits to look for Earth-sized planets orbiting Sun-like stars. However, such systems dim by only one part in ten thousand. The higher precision required to detect the drop means that such worlds can only be found from space. In contrast, a super-Earth transiting a small, red dwarf star yields a greater proportional decrease in brightness and a stronger signal that is detectable from the ground. More information This research was presented in a paper appearing this week in Nature ("A Super-Earth Transiting a Nearby Low-Mass Star", by David Charbonneau et al.). The team is composed of David Charbonneau, Zachory K. Berta, Jonathan Irwin, Christopher J. Burke, Philip Nutzman, Lars Buchhave, David W. Latham, Ruth A. Murray-Clay, Matthew J. Holman, and Emilio E. Falco (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), Christophe Lovis, Stephane Udry, Didier Queloz, Francesco Pepe, and Michel Mayor (Observatoire de l'Université de Genève, Switzerland), Xavier Bonfils, Xavier Delfosse, and Thierry Forveille (University Joseph Fourier - Grenoble 1/CNRS, LOAG, Grenoble, France), and Joshua N. Winn (Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, USA). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory, and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

A New Framework For The Evolution of Terrestrial Planets: Bi-stability, Stochastic Effects, and the Non-Uniqueness of Tectonic States

NASA Astrophysics Data System (ADS)

Weller, M. B.; Lenardic, A.

2017-12-01

Of all the Solar System bodies, the Earth is the only one for which significant observation and constraints are accessible such that they can be used to discriminate between competing models of Earth's tectonic evolution. Therefore, it is a natural tendency to use these observations to inform more general models of planetary evolution. Yet, our understating of Earth's evolution is far from complete. Geodynamic and geochemical evidence suggests that plate tectonics may not have operated on the early Earth, with both the timing of its onset and the length of its activity far from certain. In recent years, the potential of tectonic bi-stability (multiple stable, energetically allowed solutions) has been shown to be dynamically viable, both from analytical analysis and through numeric experiments in two and three dimensions. The indication is that multiple tectonic modes may operate on a single planetary body at different times within its temporal evolution. Further, there exists the potential that feedback mechanisms between the internal dynamics and surface processes (e.g., surface temperature changes driven by long term climate evolution), acting at different thermal evolution times, can cause terrestrial worlds to alternate between multiple tectonic states over giga-year timescales. Implied here is that terrestrial planets have the potential to migrate through tectonic regimes at similar `thermal evolutionary times' - points were planets have a similar bulk mantle temperature and energies -, but at very different `temporal times' - time since planetary formation. It can then be shown that identical planets at similar stages of their evolution may exhibit different tectonic regimes due to random fluctuations. A new framework of planetary evolution that moves toward probabilistic arguments based on general physical principals, as opposed to particular rheologies, and incorporates the potential of tectonic regime transitions and multiple tectonics states being viable at equivalent physical and chemical conditions, will be discussed.

Predicting Precession Rates from Secular Dynamics for Extra-solar Multi-planet Systems

NASA Astrophysics Data System (ADS)

Van Laerhoven, Christa L.

2015-11-01

Considering the secular dynamics of multi-planet systems provides substantial insight into the interactions between planets in those systems. Secular interactions are those that don't involve knowing where a planet is along its orbit, and they dominate when planets are not involved in mean motion resonances. These interactions exchange angular momentum among the planets, evolving their eccentricities and inclinations. To second order in the planets' eccentricities and inclinations, the eccentricity and inclination perturbations are decoupled. Given the right variable choice, the relevant differential equations are linear and thus the eccentricity and inclination behaviors can be described as a sum of eigenmodes. Since the underlying structure of the secular eigenmodes can be calculated using only the planets' masses and semi-major axes, one can elucidate the eccentricity and inclination behavior of planets in exoplanet systems even without knowing the planets' current eccentricities and inclinations. I have calculated both the eccentricity and inclination secular eigenmodes for the population of known multi-planet systems whose planets have well determined masses and periods. Using this catalog, and assuming a Gausian distribution for the eigenmode amplitudes and a uniform distribution for the eigenmode phases, I have predicted what range of precession rates the planets may have. Generally, planets that have more than one eigenmode significantly contribute to their eccentricity ('groupies') can have a wide range of possible precession rates, while planets that are 'loners' have a narrow range of possible precession rates. One might have assumed that in any given system, the planets with shorter periods would have faster precession rates. However, I show that in systems where the planets suffer strong secular interactions this is not necessarily the case.

Systems of Multiple Planets

NASA Astrophysics Data System (ADS)

Marcy, G. W.; Fischer, D. A.; Butler, R. P.; Vogt, S. S.

To date, 10 stars are known which harbor two or three planets. These systems reveal secular and mean motion resonances in some systems and consist of widely separated, eccentric orbits in others. Both of the triple planet systems, namely Upsilon And and 55 Cancri, exhibit evidence of resonances. The two planets orbiting GJ 876 exhibit both mean-motion and secular resonances and they perturb each other so strongly that the evolution of the orbits is revealed in the Doppler measurements. The common occurrence of resonances suggests that delicate dynamical processes often shape the architecture of planetary systems. Likely processes include planet migration in a viscous disk, eccentricity pumping by the planet-disk interaction, and resonance capture of two planets. We find a class of "hierarchical" double-planet systems characterized by two planets in widely separated orbits, defined to have orbital period ratios greater than 5 to 1. In such systems, resonant interactions are weak, leaving high-order interactions and Kozai resonances plausibly important. We compare the planets that are single with those in multiple systems. We find that neither the two mass distributions nor the two eccentricity distributions are significantly different. This similarity in single and multiple systems suggests that similar dynamical processes may operate in both. The origin of eccentricities may stem from a multi-planet past or from interactions between planets and disk. Multiple planets in resonances can pump their eccentricities pumping resulting in one planet being ejected from the system or sent into the star, leaving a (more massive) single planet in an eccentric orbit. The distribution of semimajor axes of all known extrasolar planets shows a rise toward larger orbits, portending a population of gas-giant planets that reside beyond 3 AU, arguably in less perturbed, more circular orbits.

New Worlds Observer Formation Control Design Based on the Dynamics of Relative Motion

NASA Technical Reports Server (NTRS)

Luquette, Richard J.

2008-01-01

The New Worlds Observer (NWO) mission is designed for the direct detection and characterization of extrasolar planets. The NWO mission concept employs a two spacecraft leader-follower formation on a trajectory around the Earth/Moon-Sun L(sub 2) Libration Point. The leader spacecraft is baselined as a 4 meter optical telescope. The follower, Starshade spacecraft, is designed to suppress light from a central body star permitting direct detection of a surrounding exoplanetary system. The current design requires a nominal leader-follower separation range of 72 Megameters. NWO poses many challenges including formation control. NWO cycles between three principal control modes during the nominal mission timeline: science (fine pointing), realignment and transition. This paper examines formation control strategies in the context of dynamics of relative motion for two spacecraft operating in the vicinity of the Earth/Moon-Sun L(sub 2)libration point. The paper presents an overview of the equations of relative motion followed by a discussion of each of the control modes. Discussion and analysis characterize control strategies for each of the mission control modes, including requirements, implementation challenges and project fuel budgets.

THE STATISTICAL MECHANICS OF PLANET ORBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tremaine, Scott, E-mail: tremaine@ias.edu

2015-07-10

The final “giant-impact” phase of terrestrial planet formation is believed to begin with a large number of planetary “embryos” on nearly circular, coplanar orbits. Mutual gravitational interactions gradually excite their eccentricities until their orbits cross and they collide and merge; through this process the number of surviving bodies declines until the system contains a small number of planets on well-separated, stable orbits. In this paper we explore a simple statistical model for the orbit distribution of planets formed by this process, based on the sheared-sheet approximation and the ansatz that the planets explore uniformly all of the stable region ofmore » phase space. The model provides analytic predictions for the distribution of eccentricities and semimajor axis differences, correlations between orbital elements of nearby planets, and the complete N-planet distribution function, in terms of a single parameter, the “dynamical temperature,” that is determined by the planetary masses. The predicted properties are generally consistent with N-body simulations of the giant-impact phase and with the distribution of semimajor axis differences in the Kepler catalog of extrasolar planets. A similar model may apply to the orbits of giant planets if these orbits are determined mainly by dynamical evolution after the planets have formed and the gas disk has disappeared.« less

Precise Masses in the WASP-47 System

NASA Astrophysics Data System (ADS)

Vanderburg, Andrew; Becker, Juliette C.; Buchhave, Lars A.; Mortier, Annelies; Lopez, Eric; Malavolta, Luca; Haywood, Raphaëlle D.; Latham, David W.; Charbonneau, David; López-Morales, Mercedes; Adams, Fred C.; Bonomo, Aldo Stefano; Bouchy, François; Collier Cameron, Andrew; Cosentino, Rosario; Di Fabrizio, Luca; Dumusque, Xavier; Fiorenzano, Aldo; Harutyunyan, Avet; Johnson, John Asher; Lorenzi, Vania; Lovis, Christophe; Mayor, Michel; Micela, Giusi; Molinari, Emilio; Pedani, Marco; Pepe, Francesco; Piotto, Giampaolo; Phillips, David; Rice, Ken; Sasselov, Dimitar; Ségransan, Damien; Sozzetti, Alessandro; Udry, Stéphane; Watson, Chris

2017-12-01

We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ≈19 hr orbit, and a Neptune in a ≈9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find that, unlike most other ultra-short-period planets, the inner planet, WASP-47 e, has a mass (6.83 ± 0.66 {M}\\oplus ) and a radius (1.810 ± 0.027 {R}\\oplus ) that are inconsistent with an Earth-like composition. Instead, WASP-47 e likely has a volatile-rich envelope surrounding an Earth-like core and mantle. We also perform a dynamical analysis to constrain the orbital inclination of WASP-47 c, the outer Jovian planet. This planet likely orbits close to the plane of the inner three planets, suggesting a quiet dynamical history for the system. Our dynamical constraints also imply that WASP-47 c is much more likely to transit than a geometric calculation would suggest. We calculate a transit probability for WASP-47 c of about 10%, more than an order of magnitude larger than the geometric transit probability of 0.6%.

THE FIRST SPECTRUM OF THE COLDEST BROWN DWARF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Skemer, Andrew J.; Morley, Caroline V.; Fortney, Jonathan J.

2016-08-01

The recently discovered brown dwarf WISE 0855 presents the first opportunity to directly study an object outside the solar system that is nearly as cold as our own gas giant planets. However, the traditional methodology for characterizing brown dwarfs—near-infrared spectroscopy—is not currently feasible, as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5–5.2 μ m spectrum, the same bandpass long used to study Jupiter’s deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter’s. The spectrum quality ismore » high enough to allow for the investigation of dynamical and chemical processes that have long been studied in Jupiter’s atmosphere, but now on an extrasolar world.« less

Collisional and dynamical processes in moon and planet formation

NASA Technical Reports Server (NTRS)

1979-01-01

The collisional and dynamical processes in moon and planet formation are discussed. A hydrodynamic code of collision calculations, the orbital element changes due to gravitational scattering, a validation of the mass shifting algorithm, a theory of rotations, and the origin of asteroids are studied. A numerical model of planet growth is discussed and a methodology to evaluate the rate at which megaregolith increases its depth as a function of total accumulate number of impacts on an initially smooth, coherent surface is described.

In-situ exploration of Venus on a global scale : direct measurements of origins and evolution, meterology, dynamics, and chemistry by a long-duration aerial science station

NASA Technical Reports Server (NTRS)

Baines, Kevin H.; Atreya, Sushi; Carlson, Robert W.; Chutjian, Ara; Crisp, David; Hall, Jeffrey L.; Jones, Dayton L.; Kerzhanovich, Victor V.; Limaye, Sanjay S.

2005-01-01

Drifting in the strong winds of Venus under benign Earth-like temperature and pressure conditions, an instrumented balloon-borne science station presents a viable means to explore, in-situ, the Venusian atmosphere on a global scale. Flying over the ground at speeds exceeding 240 km/hour while floating in the Venusian skies near 55 km altitude for several weeks, such an aerostat can conduct a 'world tour' of our neighboring planet, as it circumnavigates the globe multiple times during its flight from equatorial to polar latitudes. Onboard science sensors can repeatedly and directly sample gas compositions, atmospheric pressures and temperatures and cloud particle properties, giving unprecedented insight into the chemical processes occurring within the sulfuric clouds. Additionally, interferometric tracking via Earth-based radio observatories can yield positions and windspeeds to better than 10 cm/sec over one-hour periods, providing important information for understanding the planet's meridional circulation and enigmatic zonal super-rotation, as well as local dynamics associated with meteorological processes. As well, hundreds of GCMS spectra collected during the flight can provide measurements of noble gas compositions and their isotopes with unprecedented accuracy, thereby enabling fundamental new insights into Venus's origin and evolution.

Investigating circular patterns in linear polarization observations of Venus

NASA Astrophysics Data System (ADS)

Mahapatra, Gourav; Stam, Daphne; Rossi, Loic; Rodenhuis, Michiel; Snik, Frans

2017-04-01

ESA's Venus Express mission has revealed our neighbouring planet to be a highly dynamic world, with ever-changing cloud properties and structures, wind speeds that increase in time, and variable concentrations of atmospheric trace gases such as SO2. The SPICAV-IR instrument on Venus Express has provided us with close-up linear polarization data of sunlight reflected by Venus's clouds and hazes, that allows a characterisation of their composition and particle sizes. Here, we analyse linear polarization data of the planet at a distance, obtained with the Extreme Polarimeter (ExPo) on the William Herschel Telescope on La Palma. These spatially resolved, high-accuracy polarization observations of Venus show faint circular patterns centered on the sub-solar point that are absent in the flux observations. So far, careful analyses have ruled out instrumental effects which leaves us to wonder about atmospheric properties as the cause of the circular patterns. Using numerical simulations of the flux and polarization of sunlight that is reflected by Venus, we have investigated the relation between the observed patterns and several atmospheric properties, such as variations in particle sizes, composition, density and altitude. We discuss the plausibility of the possible causes in the view of the current knowledge of the composition and dynamical processes in Venus's atmosphere.

Secular dynamics of multiplanetary circumbinary systems: stationary solutions and binary-planet secular resonance

NASA Astrophysics Data System (ADS)

Andrade-Ines, Eduardo; Robutel, Philippe

2018-01-01

We present an analytical formalism to study the secular dynamics of a system consisting of N-2 planets orbiting a binary star in outer orbits. We introduce a canonical coordinate system and expand the disturbing function in terms of canonical elliptic elements, combining both Legendre polynomials and Laplace coefficients, to obtain a general formalism for the secular description of this type of configuration. With a quadratic approximation of the development, we present a simplified analytical solution for the planetary orbits for both the single planet and the two-planet cases. From the two-planet model, we show that the inner planet accelerates the precession rate of the binary pericenter, which, in turn, may enter in resonance with the secular frequency of the outer planet, characterizing a secular resonance. We calculate an analytical expression for the approximate location of this resonance and apply it to known circumbinary systems, where we show that it can occur at relatively close orbits, for example at 2.4 au for the Kepler-38 system. With a more refined model, we analyse the dynamics of this secular resonance and we show that a bifurcation of the corresponding fixed points can affect the long- term evolution and stability of planetary systems. By comparing our results with complete integrations of the exact equations of motion, we verified the accuracy of our analytical model.

Possible climates on terrestrial exoplanets.

PubMed

Forget, F; Leconte, J

2014-04-28

What kind of environment may exist on terrestrial planets around other stars? In spite of the lack of direct observations, it may not be premature to speculate on exoplanetary climates, for instance, to optimize future telescopic observations or to assess the probability of habitable worlds. To begin with, climate primarily depends on (i) the atmospheric composition and the volatile inventory; (ii) the incident stellar flux; and (iii) the tidal evolution of the planetary spin, which can notably lock a planet with a permanent night side. The atmospheric composition and mass depends on complex processes, which are difficult to model: origins of volatiles, atmospheric escape, geochemistry, photochemistry, etc. We discuss physical constraints, which can help us to speculate on the possible type of atmosphere, depending on the planet size, its final distance for its star and the star type. Assuming that the atmosphere is known, the possible climates can be explored using global climate models analogous to the ones developed to simulate the Earth as well as the other telluric atmospheres in the solar system. Our experience with Mars, Titan and Venus suggests that realistic climate simulators can be developed by combining components, such as a 'dynamical core', a radiative transfer solver, a parametrization of subgrid-scale turbulence and convection, a thermal ground model and a volatile phase change code. On this basis, we can aspire to build reliable climate predictors for exoplanets. However, whatever the accuracy of the models, predicting the actual climate regime on a specific planet will remain challenging because climate systems are affected by strong positive feedbacks. They can drive planets with very similar forcing and volatile inventory to completely different states. For instance, the coupling among temperature, volatile phase changes and radiative properties results in instabilities, such as runaway glaciations and runaway greenhouse effect.

Water in HD209458b's atmosphere from 3.6 -8 microns IRAC photometric observations in primary transit

NASA Astrophysics Data System (ADS)

Campanella, Giammarco; Beaulieu, J. P.; Kipping, D. M.; Batista, V.; Tinetti, G.; Ribas, I.; Carey, S.; Noriega-Crespo, J. A.; Griffith, C. A.; Dong, S.; Tennyson, J.; Barber, R. J.; Deroo, P.; Fossey, S. J.; Liang, D.; Swain, M. R.; Yung, Y.; Allard, N.

Since planets were first discovered outside our own Solar System in 1992 (around a pulsar) and in 1995 (around a main sequence star), extrasolar planet studies have become one of the most dynamic research fields in astronomy. Now that more than 400 exoplanets have been discovered, focus has moved from finding planets to characterise these alien worlds. Part of the characterisation process undoubtedly involves the detection of the atmospheres of these exoplanets. We describe the primary transit observations of the hot Jupiter HD 209458b we obtained at 3.6, 4.5, 5.8 and 8.0 µm using the Infrared Array Camera on the Spitzer Space Telescope. We detail the procedures we adopted to correct for the systematic trends present in IRAC data. The lightcurves were fitted, taking into account limb darkening effects, using Markov Chain Monte Carlo and prayer-bead Monte Carlo techniques. We obtained the following depth measurements: at 3.6 µm, 1.469±0.013 % and 1.448±0.013 %; at 4.5 µm, 1.478±0.017 %; at 5.8 µm, 1.549±0.015 % and at 8.0 µm 1.535±0.011 %. Our results indicate the presence of water in the planetary atmosphere.

A novel orbiter mission concept for venus with the EnVision proposal

NASA Astrophysics Data System (ADS)

de Oliveira, Marta R. R.; Gil, Paulo J. S.; Ghail, Richard

2018-07-01

In space exploration, planetary orbiter missions are essential to gain insight into planets as a whole, and to help uncover unanswered scientific questions. In particular, the planets closest to the Earth have been a privileged target of the world's leading space agencies. EnVision is a mission proposal designed for Venus and competing for ESA's next launch opportunity with the objective of studying Earth's closest neighbor. The main goal is to study geological and atmospheric processes, namely surface processes, interior dynamics and atmosphere, to determine the reasons behind Venus and Earth's radically different evolution despite the planets' similarities. To achieve these goals, the operational orbit selection is a fundamental element of the mission design process. The design of an orbit around Venus faces specific challenges, such as the impossibility of choosing Sun-synchronous orbits. In this paper, an innovative genetic algorithm optimization was applied to select the optimal orbit based on the parameters with more influence in the mission planning, in particular the mission duration and the coverage of sites of interest on the Venusian surface. The solution obtained is a near-polar circular orbit with an altitude of 259 km that enables the coverage of all priority targets almost two times faster than with the parameters considered before this study.

Climate at high obliquity

NASA Astrophysics Data System (ADS)

Marshall, J.; Ferreira, D.; O'Gorman, P. A.; Seager, S.

2011-12-01

One method of studying earth-like exoplanets is to view earth as an exoplanet and consider how its climate might change if, for example, its obliquity were ranged from 0 to 90 degrees. High values of obliquity challenge our understanding of climate dynamics because if obliquity exceeds 54 degrees, then polar latitudes receive more energy per unit area than do equatorial latitudes. Thus the pole will become warmer than the equator and we are led to consider a world in which the meridional temperature gradients, and associated prevailing zonal wind, have the opposite sign to the present earth. The problem becomes even richer when one considers the dynamics of an ocean, should one exist below. A central question for the ocean circulation is: what is the pattern of surface winds at high obliquities?, for it is the winds that drive the ocean currents and thermohaline circulation. How do atmospheric weather systems growing in the easterly sheared middle latitude jets determine the surface wind pattern? Should one expect middle latitude easterly winds? Finally, a key aspect with regard to habitability is to understand how the atmosphere and ocean of this high obliquity planet work cooperatively together to transport energy meridionally, mediating the warmth of the poles and the coldness of the equator. How extreme are seasonal temperature fluctuations? Should one expect to find ice around the equator? Possible answers to some of these questions have been sought by experimentation with a coupled atmosphere, ocean and sea-ice General Circulation Model of an earth-like aquaplanet: i.e. a planet like our own but on which there is only an ocean but no land. The coupled climate is studied across a range of obliquities (23.5, 54 and 90). We present some of the descriptive climatology of our solutions and how they shed light on the deeper questions of coupled climate dynamics that motivate them. We also review what they tell us about habitability on such planets.

ScienceCast 54: Getting to Know the Goldilocks Planet

NASA Image and Video Library

2012-03-29

NASA's Kepler spacecraft is discovering a veritable avalanche of alien worlds. It seems to be just a matter of time before Kepler finds what astronomers are really looking for: an Earth-like planet orbiting its star in the "Goldilocks zone".

Migration of accreting planets in radiative discs from dynamical torques

NASA Astrophysics Data System (ADS)

Pierens, A.; Raymond, S. N.

2016-11-01

We present the results of hydrodynamical simulations of the orbital evolution of planets undergoing runaway gas accretion in radiative discs. We consider accreting disc models with constant mass flux through the disc, and where radiative cooling balances the effect of viscous heating and stellar irradiation. We assume that 20-30 M⊕ giant planet cores are formed in the region where viscous heating dominates and migrate outward under the action of a strong entropy-related corotation torque. In the case where gas accretion is neglected and for an α viscous stress parameter α = 2 × 10-3, we find evidence for strong dynamical torques in accreting discs with accretion rates {dot{M}}≳ 7× 10^{-8} M_{⊙} yr{}^{-1}. Their main effect is to increase outward migration rates by a factor of ˜2 typically. In the presence of gas accretion, however, runaway outward migration is observed with the planet passing through the zero-torque radius and the transition between the viscous heating and stellar heating dominated regimes. The ability for an accreting planet to enter a fast migration regime is found to depend strongly on the planet growth rate, but can occur for values of the mass flux through the disc of {dot{M}}≳ 5× 10^{-8} M_{⊙} yr{}^{-1}. We find that an episode of runaway outward migration can cause an accreting planet formed in the 5-10 au region to temporarily orbit at star-planet separations as large as ˜60-70 au. However, increase in the amplitude of the Lindblad torque associated with planet growth plus change in the streamline topology near the planet systematically cause the direction of migration to be reversed. Subsequent evolution corresponds to the planet migrating inward rapidly until it becomes massive enough to open a gap in the disc and migrate in the type II regime. Our results indicate that a planet can reach large orbital distances under the combined effect of dynamical torques and gas accretion, but an alternative mechanism is required to explain the presence of massive planets on wide orbits.

Full-lifetime simulations of multiple planets across all phases of stellar evolution

NASA Astrophysics Data System (ADS)

Veras, D.; Mustill, A. J.; Gänsicke, B. T.; Redfield, S.; Georgakarakos, N.; Bowler, A. B.; Lloyd, M. J. S.

2017-09-01

We know that planetary systems are just as common around white dwarfs as around main-sequence stars. However, self-consistently linking a planetary system across these two phases of stellar evolution through the violent giant branch poses computational challenges, and previous studies restricted architectures to equal-mass planets. Here, we remove this constraint and perform over 450 numerical integrations over a Hubble time (14 Gyr) of packed planetary systems with unequal-mass planets. We characterize the resulting trends as a function of planet order and mass. We find that intrusive radial incursions in the vicinity of the white dwarf become less likely as the dispersion amongst planet masses increases. The orbital meandering which may sustain a sufficiently dynamic environment around a white dwarf to explain observations is more dependent on the presence of terrestrial-mass planets than any variation in planetary mass. Triggering unpacking or instability during the white dwarf phase is comparably easy for systems of unequal-mass planets and systems of equal-mass planets; instabilities during the giant branch phase remain rare and require fine-tuning of initial conditions. We list the key dynamical features of each simulation individually as a potential guide for upcoming discoveries.

Atmospheric circulation of extrasolar giant planets

NASA Astrophysics Data System (ADS)

Showman, A. P.

2012-12-01

Of the many known extrasolar planets, over 100 have orbital semi-major axes less than 0.1 AU, and a significant fraction of these hot Jupiters and Neptunes are known to transit their stars, allowing them to be characterized with the Spitzer, Hubble, and groundbased telescopes. The stellar flux incident on these planets is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared light curves, spectra, albedo, and atmospheric composition, and recent Spitzer infrared light curves show evidence for dynamical meteorology in these planets' atmospheres. Here, I will survey basic dynamical ideas and detailed 3D numerical models that illuminate the atmospheric circulation of these exotic, tidally locked planets. These models suggest that, generally, the circulation will be characterized by broad, fast zonal jets, with day-night temperature contrasts at the photosphere that may vary from small in some cases to large in others. I will discuss the dynamical mechanisms for maintaining the fast zonal jets that develop in these models, as well as the mechanisms for controlling the temperature patterns, including the day-night temperature contrasts. These mechanisms help to explain current observations, and they predict regime transitions for how the wind and temperature patterns should vary with the incident stellar flux, strength of atmospheric drag, and other parameters. These transitions are observable and in some cases are already becoming evident in the data. I will also compare the circulation of the hot Jupiters to that of young, massive giant planets being directly imaged around other stars, which will be the subject of a new observational vanguard over the next decade. To emphasize the similarities as well as differences, I will ground this discussion in our understanding of the more familiar atmospheric dynamical regime of Earth, as well as our "local" giant planets Jupiter, Saturn, Uranus, and Neptune.

Atmospheric circulation of extrasolar giant planets

NASA Astrophysics Data System (ADS)

Showman, A. P.

2011-12-01

Of the many known extrasolar planets, nearly 200 have orbital semi-major axes less than 0.1 AU, and a significant fraction of these hot Jupiters and Neptunes are known to transit their stars, allowing them to be characterized with the Spitzer, Hubble, and groundbased telescopes. The stellar flux incident on these planets is expected to drive an atmospheric circulation that shapes the day-night temperature difference, infrared light curves, spectra, albedo, and atmospheric composition, and recent Spitzer infrared light curves show evidence for dynamical meteorology in these planets' atmospheres. Here, I will survey basic dynamical ideas and detailed 3D numerical models that illuminate the atmospheric circulation of these exotic, tidally locked planets. These models suggest that, generally, the circulation will be characterized by broad, fast zonal jets, with day-night temperature contrasts at the photosphere that may vary from small in some cases to large in others. I will discuss the dynamical mechanisms for maintaining the fast zonal jets that develop in these models, as well as the mechanisms for controlling the temperature patterns, including the day-night temperature contrasts. These mechanisms help to explain current observations, and they predict regime transitions for how the wind and temperature patterns should vary with the incident stellar flux, strength of atmospheric drag, and other parameters. These transitions are observable and in some cases are already becoming evident in the data. I will also compare the circulation of the hot Jupiters to that of young, massive giant planets being directly imaged around other stars, which will be the subject of a new observational vanguard over the next decade. To emphasize the similarities as well as differences, I will ground this discussion in our understanding of the more familiar atmospheric dynamical regime of Earth, as well as our "local" giant planets Jupiter, Saturn, Uranus, and Neptune.

Towards an initial mass function for giant planets

NASA Astrophysics Data System (ADS)

Carrera, Daniel; Davies, Melvyn B.; Johansen, Anders

2018-07-01

The distribution of exoplanet masses is not primordial. After the initial stage of planet formation, gravitational interactions between planets can lead to the physical collision of two planets, or the ejection of one or more planets from the system. When this occurs, the remaining planets are typically left in more eccentric orbits. In this report we demonstrate how the present-day eccentricities of the observed exoplanet population can be used to reconstruct the initial mass function of exoplanets before the onset of dynamical instability. We developed a Bayesian framework that combines data from N-body simulations with present-day observations to compute a probability distribution for the mass of the planets that were ejected or collided in the past. Integrating across the exoplanet population, one can estimate the initial mass function of exoplanets. We find that the ejected planets are primarily sub-Saturn-type planets. While the present-day distribution appears to be bimodal, with peaks around ˜1MJ and ˜20M⊕, this bimodality does not seem to be primordial. Instead, planets around ˜60M⊕ appear to be preferentially removed by dynamical instabilities. Attempts to reproduce exoplanet populations using population synthesis codes should be mindful of the fact that the present population may have been depleted of sub-Saturn-mass planets. Future observations may reveal that young giant planets have a more continuous size distribution with lower eccentricities and more sub-Saturn-type planets. Lastly, there is a need for additional data and for more research on how the system architecture and multiplicity might alter our results.

Toward an initial mass function for giant planets

NASA Astrophysics Data System (ADS)

Carrera, Daniel; Davies, Melvyn B.; Johansen, Anders

2018-05-01

The distribution of exoplanet masses is not primordial. After the initial stage of planet formation, gravitational interactions between planets can lead to the physical collision of two planets, or the ejection of one or more planets from the system. When this occurs, the remaining planets are typically left in more eccentric orbits. In this report we demonstrate how the present-day eccentricities of the observed exoplanet population can be used to reconstruct the initial mass function of exoplanets before the onset of dynamical instability. We developed a Bayesian framework that combines data from N-body simulations with present-day observations to compute a probability distribution for the mass of the planets that were ejected or collided in the past. Integrating across the exoplanet population, one can estimate the initial mass function of exoplanets. We find that the ejected planets are primarily sub-Saturn type planets. While the present-day distribution appears to be bimodal, with peaks around ˜1MJ and ˜20M⊕, this bimodality does not seem to be primordial. Instead, planets around ˜60M⊕ appear to be preferentially removed by dynamical instabilities. Attempts to reproduce exoplanet populations using population synthesis codes should be mindful of the fact that the present population may have been been depleted of sub-Saturn-mass planets. Future observations may reveal that young giant planets have a more continuous size distribution with lower eccentricities and more sub-Saturn type planets. Lastly, there is a need for additional data and for more research on how the system architecture and multiplicity might alter our results.

In Situ Probe Science at Saturn

NASA Technical Reports Server (NTRS)

Atkinson, D.H.; Lunine, J.I.; Simon-Miller, A. A.; Atreya, S. K.; Brinckerhoff, W.; Colaprete, A.; Coustenis, A.; Fletcher, L. N.; Guillot, T.; Lebreton, J.-P.;

Eccentricities and inclinations of multiplanet systems with external perturbers

NASA Astrophysics Data System (ADS)

Pu, Bonan; Lai, Dong

2018-07-01

Compact multiplanet systems containing super-Earths or sub-Neptunes, commonly found around solar-type stars, may be surrounded by external giant planet or stellar companions, which can shape the architecture and observability of the inner systems. We present a comprehensive study on the evolution of the inner planetary system subject to the gravitational influence of an eccentric, misaligned outer perturber. Analytic results are derived for the inner planet eccentricities (ei) and mutual inclination (θ12) of the `two-planet + perturber' system, calibrated with numerical secular and N-body integrations, as a function of the perturber mass mp, semimajor axis ap, and inclination angle θp. We find that the dynamics of the inner system is determined by the dimensionless parameter ɛ12, given by the ratio between the differential precession rate driven by the perturber and the mutual precession rate of the inner planets. Loosely packed systems (corresponding to ɛ12 ≫ 1) are more susceptible to eccentricity/inclination excitations by the perturber than tightly packed inner systems (with ɛ12 ≪ 1) (or singletons), although resonance may occur around ɛ12 ˜ 1, leading to large ei and θ12. Dynamical instability may set in for inner planet systems with large excited eccentricities and mutual inclinations. We present a formalism to extend our analytical results to general inner systems with N > 2 planets and apply our results to constrain possible external companions to the Kepler-11 system. Eccentricity and inclination excitation by external companions may help explain the observational trend that systems with fewer transiting planets are dynamically hotter than those with more transiting planets.

Orbital Eccentricity and the Stability of Planets in the Alpha Centauri System

NASA Technical Reports Server (NTRS)

Lissauer, Jack

2016-01-01

Planets on initially circular orbits are typically more dynamically stable than planets initially having nonzero eccentricities. However, the presence of a major perturber that forces periodic oscillations of planetary eccentricity can alter this situation. We investigate the dependance of system lifetime on initial eccentricity for planets orbiting one star within the alpha Centauri system. Our results show that initial conditions chosen to minimize free eccentricity can substantially increase stability compared to planets on circular orbits.

Where the Sun Sets Twice Artist Concept

NASA Image and Video Library

2011-09-15

NASA Kepler mission has discovered a world where two suns set over the horizon instead of just one. The planet, called Kepler-16b, is the most Tatooine-like planet yet found in our galaxy and is depicted here in this artist concept.

14th Annual P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet

EPA Pesticide Factsheets

EPA as part of its People, Prosperity and the Planet (P3) Award Program – is seeking applications proposing to research, develop, and design solutions to real world challenges involving sustainability.

75 FR 8065 - Notice of Public Information Collection Being Reviewed by the Federal Communications Commission...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-23

... AmericanLife TV Animal Planet BBC America BBC World News BET BET Gospel BET Hip-Hop BET J Big Ten Bio... Nickelodeon Noggin Outdoor Channel Ovation TV Oxygen Palladia PBS Kids Sprout Planet Green ReelzChannel...

Collisional and dynamical processes in moon and planet formation

NASA Technical Reports Server (NTRS)

Chapman, C. R.; Davis, D. R.; Weidenschilling, S. J.; Hartmann, W. K.; Spaute, D.

1987-01-01

Research on a variety of dynamical processes relevant to the formation of planets, satellites and ring systems is discussed. The main focus is on studies of accretionary formation of early protoplanets using a numerical model, structures and evolution of ring systems and individual bodies within planetary rings, and theories of lunar origin.

NASA’s Spitzer Reveals Largest Batch of Earth-Size, Habitable-Zone Planets Around a Single Star

NASA Image and Video Library

2017-02-22

NASA held a news conference Feb. 22 at the agency’s headquarters to discuss the finding by the Spitzer Space Telescope of seven Earth-sized planets around a tiny, nearby, ultra-cool dwarf star. Three of these planets are in the habitable zone, the region around the star in which liquid water is most likely to thrive on a rocky planet. This is the first time so many planets have been found in a single star's habitable zone, and the first time so many Earth-sized planets have been found around the same star. The finding of this planetary system, called TRAPPIST-1, is the best target yet for studying the atmospheres of potentially habitable, Earth-sized worlds

Dynamics of the Triple-Star System Alpha Centauri and its Impact on Habitable Planets

NASA Astrophysics Data System (ADS)

Jayla Jones, Ayanna; Fabrycky, Daniel

2018-01-01

The Alpha Centauri system, our solar system's closest neighbor, has become a target in the search for habitable planets. The system is composed of three stars: Alpha Centauri A and Alpha Centauri B, stars forming an inner binary, and Proxima Centauri, an outer star that orbits around the inner binary. We computed 3-body models to follow the dynamics for the main-sequence lifetimes of the stars that are based on 100 realizations of the observed orbits. In the majority of cases, Proxima only modestly torques the A-B binary orbit, and so previous studies of planet formation and dynamics, which find the habitable zones to be stable, are somewhat justified in ignoring this effect. On the other hand, in ~16% of the observationally allowed orbits, fluctuations in the orbital eccentricity of the A-B orbit destabilize the middle of the habitable zone of both stars. This result calls for further theoretical work to quantify the effect of galactic tides, passing stars, and massive planets in the triple-system dynamics.

Using the Bombardment History of the Moon to Understand Planet Formation

NASA Astrophysics Data System (ADS)

Bottke, W. F.; NASA/NLSI CenterLunar Origin; Evolution (CLOE)

2011-12-01

The Moon is unique. It is the only object that is both relatively accessible and still bears scars from practically every epoch of solar system formation. This is both a challenge and a blessing. It is a challenge because to understand the Moon's complex bombardment history, we need to understand the formation and evolution of the solar system as a whole. It is a blessing because the Moon is an irreplaceable resource for the study of events that have shaped the Earth and other planets. For example, we can now show the Moon's bombardment history can be broken into several episodes defined by planet formation processes. The earliest phase lasts for several hundreds of My after the first solids form. Here many planets grow via a new process called "planetesimal-driven migration", with embryos moving outward in the disk by gravitationally-scattering planetesimals. This mobility assists accretion and may explain the interesting properties of certain worlds (e.g., Mars). In the outer solar system, the giant planets form on different orbits than their observed ones via a variety of processes that we are still struggling to understand. The evidence they had a different configuration, however, can be found in (i) the orbital distribution of the asteroid belt, with particular unusual asteroids residing where Jupiter used to have its mean motion resonances, and (ii) in the lunar crater record, with the oldest craters formed at half the impact velocity than more recent ones. The lunar impact flux over this interval constrains how these worlds evolved. The second episode occurred near 4.1 Ga and is often called the "Nice model". It was triggered by a dynamical instability taking place among the giant planets, who quickly moved to their current orbits via interactions with both themselves and comet-like planetesimals scattered out of a disk residing beyond 12 AU. A by-product of this planetary reconfiguration was the ejection of comets and asteroids from stable reservoirs across this solar system. Some hit the Moon and produced the so-called lunar "cataclysm", with impact velocities nearly the same as current values. This velocity change allows us to use craters to predict that this episode started near the formation time of lunar basin Nectaris. The episode's end is often thought to be marked across the solar system by the formation of the last lunar basin Orientale near 3.7 Ga. However, basin-forming projectiles liberated by this event continued to hit Earth throughout the Archean and likely persisted until ~2.5 Ga. The implications of this for the history of our biosphere are likely to be profound. The final episode, which lasted billions of years, is defined by collision events in the asteroid belt, which deliver impactors to the inner solar system via dynamical processes. This period likely contains both "lulls" and intervals of steeply higher impact rates via asteroid showers. While the history of this period is still poorly understood, correlations between the lunar crater record and family-forming events in the main belt suggest impacts have influenced, perhaps significantly, the evolution of life on Earth.

Debris disks as signposts of terrestrial planet formation. II. Dependence of exoplanet architectures on giant planet and disk properties

NASA Astrophysics Data System (ADS)

Raymond, S. N.; Armitage, P. J.; Moro-Martín, A.; Booth, M.; Wyatt, M. C.; Armstrong, J. C.; Mandell, A. M.; Selsis, F.; West, A. A.

2012-05-01

We present models for the formation of terrestrial planets, and the collisional evolution of debris disks, in planetary systems that contain multiple marginally unstable gas giants. We previously showed that in such systems, the dynamics of the giant planets introduces a correlation between the presence of terrestrial planets and cold dust, i.e., debris disks, which is particularly pronounced at λ ~ 70 μm. Here we present new simulations that show that this connection is qualitatively robust to a range of parameters: the mass distribution of the giant planets, the width and mass distribution of the outer planetesimal disk, and the presence of gas in the disk when the giant planets become unstable. We discuss how variations in these parameters affect the evolution. We find that systems with equal-mass giant planets undergo the most violent instabilities, and that these destroy both terrestrial planets and the outer planetesimal disks that produce debris disks. In contrast, systems with low-mass giant planets efficiently produce both terrestrial planets and debris disks. A large fraction of systems with low-mass (M ≲ 30 M⊕) outermost giant planets have final planetary separations that, scaled to the planets' masses, are as large or larger than the Saturn-Uranus and Uranus-Neptune separations in the solar system. We find that the gaps between these planets are not only dynamically stable to test particles, but are frequently populated by planetesimals. The possibility of planetesimal belts between outer giant planets should be taken into account when interpreting debris disk SEDs. In addition, the presence of ~ Earth-mass "seeds" in outer planetesimal disks causes the disks to radially spread to colder temperatures, and leads to a slow depletion of the outer planetesimal disk from the inside out. We argue that this may explain the very low frequency of >1 Gyr-old solar-type stars with observed 24 μm excesses. Our simulations do not sample the full range of plausible initial conditions for planetary systems. However, among the configurations explored, the best candidates for hosting terrestrial planets at ~1 AU are stars older than 0.1-1 Gyr with bright debris disks at 70 μm but with no currently-known giant planets. These systems combine evidence for the presence of ample rocky building blocks, with giant planet properties that are least likely to undergo destructive dynamical evolution. Thus, we predict two correlations that should be detected by upcoming surveys: an anti-correlation between debris disks and eccentric giant planets and a positive correlation between debris disks and terrestrial planets. Three movies associated to Figs. 1, 3, and 7 are available in electronic form at http://www.aanda.org

A radiogenic heating evolution model for cosmochemically Earth-like exoplanets

NASA Astrophysics Data System (ADS)

Frank, Elizabeth A.; Meyer, Bradley S.; Mojzsis, Stephen J.

2014-11-01

Discoveries of rocky worlds around other stars have inspired diverse geophysical models of their plausible structures and tectonic regimes. Severe limitations of observable properties require many inexact assumptions about key geophysical characteristics of these planets. We present the output of an analytical galactic chemical evolution (GCE) model that quantitatively constrains one of those key properties: radiogenic heating. Earth's radiogenic heat generation has evolved since its formation, and the same will apply to exoplanets. We have fit simulations of the chemical evolution of the interstellar medium in the solar annulus to the chemistry of our Solar System at the time of its formation and then applied the carbonaceous chondrite/Earth's mantle ratio to determine the chemical composition of what we term ;cosmochemically Earth-like; exoplanets. Through this approach, predictions of exoplanet radiogenic heat productions as a function of age have been derived. The results show that the later a planet forms in galactic history, the less radiogenic heat it begins with; however, due to radioactive decay, today, old planets have lower heat outputs per unit mass than newly formed worlds. The long half-life of 232Th allows it to continue providing a small amount of heat in even the most ancient planets, while 40K dominates heating in young worlds. Through constraining the age-dependent heat production in exoplanets, we can infer that younger, hotter rocky planets are more likely to be geologically active and therefore able to sustain the crustal recycling (e.g. plate tectonics) that may be a requirement for long-term biosphere habitability. In the search for Earth-like planets, the focus should be made on stars within a billion years or so of the Sun's age.

Effects of Variable Eccentricity on the Climate of an Earth-like World

NASA Astrophysics Data System (ADS)

Way, M. J.; Georgakarakos, Nikolaos

2017-01-01

The Kepler era of exoplanetary discovery has presented the astronomical community with a cornucopia of planetary systems that are very different from the one that we inhabit. It has long been known that Jupiter plays a major role in the orbital parameters of Mars and its climate, but there is also a long-standing belief that Jupiter would play a similar role for Earth if not for the Moon. Using a three-dimensional general circulation model (3D GCM) with a fully coupled ocean, we simulate what would happen to the climate of an Earth-like world if Mars did not exist, but a Jupiter-like planet was much closer to Earth’s orbit. We investigate two scenarios that involve the evolution of the Earth-like planet’s orbital eccentricity from 0 to 0.283 over 6500 years, and from 0 to 0.066 on a timescale of 4500 years. In both cases we discover that they would maintain relatively temperate climates over the timescales simulated. More Earth-like planets in multi-planet systems will be discovered as we continue to survey the skies and the results herein show that the proximity of large gas giant planets may play an important role in the habitability of these worlds. These are the first such 3D GCM simulations using a fully coupled ocean with a planetary orbit that evolves over time due to the presence of a giant planet.

Influence of Stellar Multiplicity On Planet Formation. III. Adaptive Optics Imaging of Kepler Stars With Gas Giant Planets

NASA Astrophysics Data System (ADS)

Wang, Ji; Fischer, Debra A.; Horch, Elliott P.; Xie, Ji-Wei

2015-06-01

As hundreds of gas giant planets have been discovered, we study how these planets form and evolve in different stellar environments, specifically in multiple stellar systems. In such systems, stellar companions may have a profound influence on gas giant planet formation and evolution via several dynamical effects such as truncation and perturbation. We select 84 Kepler Objects of Interest (KOIs) with gas giant planet candidates. We obtain high-angular resolution images using telescopes with adaptive optics (AO) systems. Together with the AO data, we use archival radial velocity data and dynamical analysis to constrain the presence of stellar companions. We detect 59 stellar companions around 40 KOIs for which we develop methods of testing their physical association. These methods are based on color information and galactic stellar population statistics. We find evidence of suppressive planet formation within 20 AU by comparing stellar multiplicity. The stellar multiplicity rate (MR) for planet host stars is {0}-0+5% within 20 AU. In comparison, the stellar MR is 18% ± 2% for the control sample, i.e., field stars in the solar neighborhood. The stellar MR for planet host stars is 34% ± 8% for separations between 20 and 200 AU, which is higher than the control sample at 12% ± 2%. Beyond 200 AU, stellar MRs are comparable between planet host stars and the control sample. We discuss the implications of the results on gas giant planet formation and evolution.

Planet Hunters: Kepler by Eye

NASA Astrophysics Data System (ADS)

Schwamb, Megan E.; Lintott, C.; Fischer, D.; Smith, A. M.; Boyajian, T. S.; Brewer, J. M.; Giguere, M. J.; Lynn, S.; Parrish, M.; Schawinski, K.; Schmitt, J.; Simpson, R.; Wang, J.

2014-01-01

Planet Hunters (http://www.planethunters.org), part of the Zooniverse's (http://www.zooniverse.org) collection of online citizen science projects, uses the World Wide Web to enlist the general public to identify transits in the pubic Kepler light curves. Planet Hunters utilizes human pattern recognition to identify planet transits that may be missed by automated detection algorithms looking for periodic events. Referred to as ‘crowdsourcing’ or ‘citizen science’, the combined assessment of many non-expert human classifiers with minimal training can often equal or best that of a trained expert and in many cases outperform the best machine-learning algorithm. Visitors to the Planet Hunters' website are presented with a randomly selected ~30-day light curve segment from one of Kepler’s ~160,000 target stars and are asked to draw boxes to mark the locations of visible transits in the web interface. 5-10 classifiers review each 30-day light curve segment. Since December 2010, more than 260,000 volunteers world wide have participated, contributing over 20 million classifications. We have demonstrated the success of a citizen science approach with the project’s more than 20 planet candidates, the discovery of PH1b, a transiting circumbinary planet in a quadruple star system, and the discovery of PH2-b, a confirmed Jupiter-sized planet in the habitable zone of a Sun-like star. I will provide an overview of Planet Hunters, highlighting several of project's most recent exoplanet and astrophysical discoveries. Acknowledgements: MES was supported in part by a NSF AAPF under award AST-1003258 and a American Philosophical Society Franklin Grant. We acknowledge support from NASA ADAP12-0172 grant to PI Fischer.

Planets Around Neutron Stars

NASA Technical Reports Server (NTRS)

Wolszczan, Alexander; Kulkarni, Shrinivas R; Anderson, Stuart B.

2003-01-01

The objective of this proposal was to continue investigations of neutron star planetary systems in an effort to describe and understand their origin, orbital dynamics, basic physical properties and their relationship to planets around normal stars. This research represents an important element of the process of constraining the physics of planet formation around various types of stars. The research goals of this project included long-term timing measurements of the planets pulsar, PSR B1257+12, to search for more planets around it and to study the dynamics of the whole system, and sensitive searches for millisecond pulsars to detect further examples of old, rapidly spinning neutron stars with planetary systems. The instrumentation used in our project included the 305-m Arecibo antenna with the Penn State Pulsar Machine (PSPM), the 100-m Green Bank Telescope with the Berkeley- Caltech Pulsar Machine (BCPM), and the 100-m Effelsberg and 64-m Parkes telescopes equipped with the observatory supplied backend hardware.

Stability and self-organization of planetary systems.

PubMed

Pakter, Renato; Levin, Yan

2018-04-01

We show that stability of planetary systems is intimately connected with their internal order. An arbitrary initial distribution of planets is susceptible to catastrophic events in which planets either collide or are ejected from the planetary system. These instabilities are a fundamental consequence of chaotic dynamics and of Arnold diffusion characteristic of many body gravitational interactions. To ensure stability over astronomical time scale of a realistic planetary system-in which planets have masses comparable to those of planets in the solar system-the motion must be quasiperiodic. A dynamical mechanism is proposed which naturally evolves a planetary system to a quasiperiodic state from an arbitrary initial condition. A planetary self-organization predicted by the theory is similar to the one found in our solar system.

Stability and self-organization of planetary systems

NASA Astrophysics Data System (ADS)

Pakter, Renato; Levin, Yan

2018-04-01

We show that stability of planetary systems is intimately connected with their internal order. An arbitrary initial distribution of planets is susceptible to catastrophic events in which planets either collide or are ejected from the planetary system. These instabilities are a fundamental consequence of chaotic dynamics and of Arnold diffusion characteristic of many body gravitational interactions. To ensure stability over astronomical time scale of a realistic planetary system—in which planets have masses comparable to those of planets in the solar system—the motion must be quasiperiodic. A dynamical mechanism is proposed which naturally evolves a planetary system to a quasiperiodic state from an arbitrary initial condition. A planetary self-organization predicted by the theory is similar to the one found in our solar system.

The Geometry of Resonant Signatures in Debris Disks with Planets

NASA Astrophysics Data System (ADS)

Kuchner, M. J.; Holman, M. J.

2002-09-01

Using simple geometrical arguments, we paint an overview of the variety of resonant structures a single planet with moderate eccentricity (e < 0.6) can create in a dynamically cold, optically thin dust disk. This overview may serve as a key for interpreting images of perturbed debris disks and inferring the dynamical properties of the planets responsible for the perturbations. We compare the resonant structures found in the solar system with observations of planetary systems around Vega and other stars and we offer a new model for the asymmetries in the Epsilon Eridani disk. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) through the Michelson Fellowship program funded by NASA as an element of the Planet Finder Program.

Paint by Particle

NASA Image and Video Library

2017-12-08

NASA models and supercomputing have created a colorful new view of aerosol movement. Satellites, balloon-borne instruments and ground-based devices make 30 million observations of the atmosphere each day. Yet these measurements still give an incomplete picture of the complex interactions within the membrane surrounding Earth. Enter climate models. Through mathematical experiments, modelers can move Earth forward or backward in time to create a dynamic portrait of the planet. Researchers from NASA Goddard’s Global Modeling and Assimilation Office recently ran a simulation of the atmosphere that captured how winds whip aerosols around the world. Such simulations allow scientists to better understand how these tiny particulates travel in the atmosphere and influence weather and climate. In the visualization below, covering August 2006 to April 2007, watch as dust and sea salt swirl inside cyclones, carbon bursts from fires, sulfate streams from volcanoes—and see how these aerosols paint the modeled world. Credit: NASA/Goddard Space Flight Center

The Terrestrial Planet Finder coronagraph dynamics error budget

NASA Technical Reports Server (NTRS)

Shaklan, Stuart B.; Marchen, Luis; Green, Joseph J.; Lay, Oliver P.

2005-01-01

The Terrestrial Planet Finder Coronagraph (TPF-C) demands extreme wave front control and stability to achieve its goal of detecting earth-like planets around nearby stars. We describe the performance models and error budget used to evaluate image plane contrast and derive engineering requirements for this challenging optical system.

Pathways to Earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres.

PubMed

Lammer, Helmut; Kislyakova, K G; Odert, P; Leitzinger, M; Schwarz, R; Pilat-Lohinger, E; Kulikov, Yu N; Khodachenko, M L; Güdel, M; Hanslmeier, M

2011-12-01

We discuss the evolution of the atmosphere of early Earth and of terrestrial exoplanets which may be capable of sustaining liquid water oceans and continents where life may originate. The formation age of a terrestrial planet, its mass and size, as well as the lifetime in the EUV-saturated early phase of its host star play a significant role in its atmosphere evolution. We show that planets even in orbits within the habitable zone of their host stars might not lose nebular- or catastrophically outgassed initial protoatmospheres completely and could end up as water worlds with CO2 and hydrogen- or oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet evolves to an N2-rich atmosphere too early in its lifetime, the atmosphere may be lost. We show that the initial conditions set up by the formation of a terrestrial planet and by the evolution of the host star's EUV and plasma environment are very important factors owing to which a planet may evolve to a habitable world. Finally we present a method for studying the discussed atmosphere evolution hypotheses by future UV transit observations of terrestrial exoplanets.

THE HUNT FOR EXOMOONS WITH KEPLER (HEK). I. DESCRIPTION OF A NEW OBSERVATIONAL PROJECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kipping, D. M.; Bakos, G. A.; Buchhave, L.

2012-05-10

Two decades ago, empirical evidence concerning the existence and frequency of planets around stars, other than our own, was absent. Since that time, the detection of extrasolar planets from Jupiter-sized to, most recently, Earth-sized worlds has blossomed and we are finally able to shed light on the plurality of Earth-like, habitable planets in the cosmos. Extrasolar moons may also be frequently habitable worlds, but their detection or even systematic pursuit remains lacking in the current literature. Here, we present a description of the first systematic search for extrasolar moons as part of a new observational project called 'The Hunt formore » Exomoons with Kepler' (HEK). The HEK project distills the entire list of known transiting planet candidates found by Kepler (2326 at the time of writing) down to the most promising candidates for hosting a moon. Selected targets are fitted using a multimodal nested sampling algorithm coupled with a planet-with-moon light curve modeling routine. By comparing the Bayesian evidence of a planet-only model to that of a planet-with-moon, the detection process is handled in a Bayesian framework. In the case of null detections, upper limits derived from posteriors marginalized over the entire prior volume will be provided to inform the frequency of large moons around viable planetary hosts, {eta} leftmoon. After discussing our methodologies for target selection, modeling, fitting, and vetting, we provide two example analyses.« less

Prospecting for Habitable Worlds

NASA Technical Reports Server (NTRS)

Jenkins, Jon M.

2017-01-01

NASAs Kepler Mission was launched in March 2009 as NASAs first mission capable of finding Earth-size planets orbiting in the habitable zone of Sun-like stars, that range of distances for which liquid water would pool on the surface of a rocky planet. Kepler has discovered over 2200 planets and over 2200 candidate planets, many of them as small as the Earth. Forty nine of these are less than twice the size of Earth and orbit in the habitable zone of their stars, all of which are cooler and significantly smaller than the Sun.Today, Keplers amazing success seems to be a fait accompli to those unfamiliar with her history. But twenty years ago, there were no planets known outside our solar system, and few people believed it was possible to detect tiny Earth-size planets orbiting other stars. Indeed, demonstrating that the science was feasible took four proposals to NASAs Discovery Program and extensive research and laboratory demonstrations. Motivating NASA to select Kepler for launch required a confluence of the right detector technology, advances in signal processing and algorithms, and the power of supercomputing. On August 23 2015 we reported the discovery of Kepler-452b, the first small, possibly rocky planet in the habitable zone of a G2 star very similar to our own. Kepler-452b orbits its star once every 385 days in an orbit just 5 larger than that of Earth. This discovery represents an important step towards finding and characterizing small habitable worlds orbiting Sun-like stars.

Forecasting Weather on Distant Worlds

NASA Technical Reports Server (NTRS)

2007-01-01

An artist's conception shows a gas-giant planet orbiting very close to its parent star, creating searingly hot conditions on the planet's surface. New research suggests that for three such planets lying from 50 to 150 light-years from Earth, strong winds thousands of miles per hour mix the atmosphere so that the temperature is relatively uniform from the permanently light side to the permanently dark side.

This illustration represents an infrared view of a planetary system, in which brightness indicates warmer temperatures. For example, the bright band around the equator of the planet denotes warmer temperatures on both the dark and sunlit sides. The planet's poles, shown in darker colors, would be cooler.

15th Annual P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet

EPA Pesticide Factsheets

The U.S. Environmental Protection Agency (EPA) – as part of its People, Prosperity and the Planet (P3) Award Program – is seeking applications proposing to research, develop, design, and demonstrate solutions to real world challenges

NEXT GENERATION OF TELESCOPES OR DYNAMICS REQUIRED TO DETERMINE IF EXO-MOONS HAVE PROGRADE OR RETROGRADE ORBITS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Karen M.; Fujii, Yuka

2014-08-20

We survey the methods proposed in the literature for detecting moons of extrasolar planets in terms of their ability to distinguish between prograde and retrograde moon orbits, an important tracer of the moon formation channel. We find that most moon detection methods, in particular, sensitive methods for detecting moons of transiting planets, cannot observationally distinguishing prograde and retrograde moon orbits. The prograde and retrograde cases can only be distinguished where the dynamical evolution of the orbit due to, e.g., three body effects is detectable, where one of the two cases is dynamically unstable, or where new observational facilities, which canmore » implement a technique capable of differentiating the two cases, come online. In particular, directly imaged planets are promising targets because repeated spectral and photometric measurements, which are required to determine moon orbit direction, could also be conducted with the primary interest of characterizing the planet itself.« less

Stability and Evolution of Multiple Planet and Satellite Systems

NASA Astrophysics Data System (ADS)

Quillen, Alice

Numerous multiple planet systems have recently been discovered with the Kepler Mission, suggesting that multiple planet systems are common. Multiple- body nearly coplanar satellite systems are also found in the Solar system. Multiple planet and satellite systems exhibit rich dynamics as they are affected by three-body and secular resonances affecting short timescale behavior and long timescale stability. Interactions with debris disks and planetesimal belts and tidal interactions can both reduce and induce instability. Using both numerical and analytical studies, we propose to develop a broadly applicable framework to estimate diffusion rates and stability regimes both in resonant and non- resonant configurations. Understanding of resonant dynamics is needed to understand each of these systems and a broader general theory would cover scenarios and mechanisms that are relevant for all of them. Architectures and dynamical mechanisms will be used to test scenarios for formation and evolution of multiple body systems and constrain poorly known quantities such as masses, eccentricities, inclinations, radii, and the existence of undetected bodies.

The dynamics of the multi-planet system orbiting Kepler-56

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Gongjie; Naoz, Smadar; Johnson, John Asher

2014-10-20

Kepler-56 is a multi-planet system containing two coplanar inner planets that are in orbits misaligned with respect to the spin axis of the host star, and an outer planet. Various mechanisms have been proposed to explain the broad distribution of spin-orbit angles among exoplanets, and these theories fall under two broad categories. The first is based on dynamical interactions in a multi-body system, while the other assumes that disk migration is the driving mechanism in planetary configuration and that the star (or disk) is titled with respect to the planetary plane. Here we show that the large observed obliquity ofmore » Kepler 56 system is consistent with a dynamical origin. In addition, we use observations by Huber et al. to derive the obliquity's probability distribution function, thus improving the constrained lower limit. The outer planet may be the cause of the inner planets' large obliquities, and we give the probability distribution function of its inclination, which depends on the initial orbital configuration of the planetary system. We show that even in the presence of precise measurement of the true obliquity, one cannot distinguish the initial configurations. Finally we consider the fate of the system as the star continues to evolve beyond the main sequence, and we find that the obliquity of the system will not undergo major variations as the star climbs the red giant branch. We follow the evolution of the system and find that the innermost planet will be engulfed in ∼129 Myr. Furthermore we put an upper limit of ∼155 Myr for the engulfment of the second planet. This corresponds to ∼3% of the current age of the star.« less

Atmospheres of the Giant Planets

NASA Technical Reports Server (NTRS)

Ingersoll, Andrew P.

2002-01-01

The giant planets, Jupiter, Saturn, Uranus, and Neptune, are fluid objects. They have no solid surfaces because the light elements constituting them do not condense at solar-system temperatures. Instead, their deep atmospheres grade downward until the distinction between gas and liquid becomes meaningless. The preceding chapter delved into the hot, dark interiors of the Jovian planets. This one focuses on their atmospheres, especially the observable layers from the base of the clouds to the edge of space. These veneers arc only a few hundred kilometers thick, less than one percent of each planet's radius, but they exhibit an incredible variety of dynamic phenomena. The mixtures of elements in these outer layers resemble a cooled-down piece of the Sun. Clouds precipitate out of this gaseous soup in a variety of colors. The cloud patterns are organized by winds, which are powered by heat derived from sunlight (as on Earth) and by internal heat left over from planetary formation. Thus the atmospheres of the Jovian planets are distinctly different both compositionally and dynamically from those of the terrestrial planets. Such differences make them fascinating objects for study, providing clues about the origin and evolution of the planets and the formation of the solar system.

The Impact of Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Dupuy, Trent; Mann, Andrew; Huber, Daniel

2018-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion. We now update these results with multi-epoch imaging to reject non-comoving background stars and securely identify even the least massive stellar companions, as well as tracing out the orbital motion of stellar companions. These results are beginning to reveal not just the fraction of binaries that do not host planets, but also potential explanations for planet survival even in some very close, dynamically active binary systems.

Views from EPOXI. Colors in Our Solar System as an Analog for Extrasolar Planets

NASA Technical Reports Server (NTRS)

Crow, Carolyn A.; McFadden, L. A.; Robinson, T.; Livengood, T. A.; Hewagama, T.; Barry, R. K.; Deming, L. D.; Meadows, V.; Lisse, C. M.

2010-01-01

With extrasolar planet detection becoming more common place, the frontiers of extrasolar planet science have moved beyond detection to the observations required to determine planetary properties. Once the existing observational challenges have been overcome, the first visible-light studies of extrasolar Earth-sized planets will likely employ filter photometry or low-resolution. spectroscopy to observe disk-integrated radiation from the unresolved planet. While spectroscopy of these targets is highly desirable, and provides the most robust form of characterization. S/N considerations presently limit spectroscopic measurements of extrasolar worlds. Broadband filter photometry will thus serve as a first line of characterization. In this paper we use Extrasolar Observation and Characterization (EPOCh) filter photometry of the Earth. Moon and Mars model spectra. and previous photometric and spectroscopic observations of a range the solar system planets. Titan, and Moon to explore the limitations of using color as a baseline for understanding extrasolar planets

The Gemini Planet Imager Exoplanet Survey

NASA Astrophysics Data System (ADS)

Macintosh, Bruce

The Gemini Planet Imager (GPI) is a next-generation coronagraph constructed for the Gemini Observatory. GPI will see first light this fall. It will be the most advanced planet-imaging system in operation - an order of magnitude more sensitive than any current instrument, capable of detecting and spectroscopically characterizing young Jovian planets 107 times fainter than their parent star at separations of 0.2 arcseconds. GPI was built from the beginning as a facility-class survey instrument, and the observatory will employ it that way. Our team has been selected by Gemini Observatory to carry out an 890-hour program - the GPI Exoplanet Survey (GPIES) campaign from 2014-2017. We will observe 600 stars spanning spectral types A-M. We will use published young association catalogs and a proprietary list in preparation that adds several hundred new young (<100 Myr, <75 pc) and adolescent (<300 Myr, <35 pc) stars. The range of separations studied by GPI is completely inaccessible to Doppler and transit techniques (even with Kepler or TESS)— GPI offers a new window into planet formation. We will use GPI to produce the first-ever robust census of giant planet populations in the 5-50 AU range, allowing us to: 1) illuminate the formation pathways of Jovian planets; 2) reconstruct the early dynamical evolution of systems, including migration mechanisms and the interaction with disks and belts of debris; and 3) bridge the gap between Jupiter and the brown dwarfs with the first examples of cool low- gravity planetary atmospheres. Simulations predict this survey will discover approximately 50 exoplanets, increasing the number of exoplanet images by an order of magnitude, enough for statistical investigation. This Origins of Solar Systems proposal will support the execution of the GPI Exoplanet Survey campaign. We will develop tools needed to execute the survey efficiently. We will refine the existing GPI data pipeline to a final version that robustly removes residual speckle artifacts and provides accurate and calibrated recovery of exoplanet spectra. We will produce a complete archive of all reduced GPI data products (supplementing the existing Gemini archive of raw data) for use by our collaboration, and release that archive to the public on an 18-month cycle. Most importantly, we will execute the GPI observations, initially through classical telescope visits, transitioning to remote and queue modes as our techniques are refined. As the first direct-imaging planet search with statistical depth comparable to Doppler planet detection and the first to probe into the snow line, the GPI Exoplanet Survey will provide strong constraints on paradigms for planet formation, completing the picture of the giant planet distribution throughout other solar systems, and also illuminating its evolution with stellar age and mass. We will deliver a catalog of detected exoplanets— the principal legacy of this campaign—released for follow-up by the astronomical community within 18 months of observation, as well as searchable archive of fully reduced images and detection limits for all stars surveyed. For each detected planet, we will produce estimated effective temperatures, luminosities, and semi-major axes: for a subset, high-SNR fiducial spectra, orbital eccentricities, and dynamical characterization through polarimetric imaging of attendant debris disks. GPI will complete final acceptance testing this month (May 2013) and is now ready to ship to Chile for first light in September 2013. The GPI survey will provide the best-yet view of the nature of wide-orbit planetary companions, informing our knowledge of solar system formation to guide future NASA planet hunting missions, while simultaneously offering a real- world program using the techniques - from integral field spectroscopy to advanced coronagraphy - that will someday be used to directly image Earthlike planets from space.

Ring World

NASA Image and Video Library

2007-03-01

Our robotic emissary, flying high above Saturn, captured this view of an alien copper-colored ring world. The overexposed planet has deliberately been removed to show the unlit rings alone, seen from an elevation of 60 degrees

Outcomes of Grazing Impacts between Sub-Neptunes in Kepler  Multis

NASA Astrophysics Data System (ADS)

Hwang, Jason; Chatterjee, Sourav; Lombardi, James, Jr.; Steffen, Jason H.; Rasio, Frederic

2018-01-01

Studies of high-multiplicity, tightly packed planetary systems suggest that dynamical instabilities are common and affect both the orbits and planet structures, where the compact orbits and typically low densities make physical collisions likely outcomes. Since the structure of many of these planets is such that the mass is dominated by a rocky core, but the volume is dominated by a tenuous gas envelope, the sticky-sphere approximation, used in dynamical integrators, may be a poor model for these collisions. We perform five sets of collision calculations, including detailed hydrodynamics, sampling mass ratios, and core mass fractions typical in Kepler Multis. In our primary set of calculations, we use Kepler-36 as a nominal remnant system, as the two planets have a small dynamical separation and an extreme density ratio. We use an N-body code, Mercury 6.2, to integrate initially unstable systems and study the resultant collisions in detail. We use these collisions, focusing on grazing collisions, in combination with realistic planet models created using gas profiles from Modules for Experiments in Stellar Astrophysics and core profiles using equations of state from Seager et al. to perform hydrodynamic calculations, finding scatterings, mergers, and even a potential planet–planet binary. We dynamically integrate the remnant systems, examine the stability, and estimate the final densities, finding that the remnant densities are sensitive to the core masses, and collisions result in generally more stable systems. We provide prescriptions for predicting the outcomes and modeling the changes in mass and orbits following collisions for general use in dynamical integrators.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shang-Fei; Lin, Douglas N. C.; Guillochon, James

A large population of planetary candidates in short-period orbits have been found recently through transit searches, mostly with the Kepler mission. Radial velocity surveys have also revealed several Jupiter-mass planets with highly eccentric orbits. Measurements of the Rossiter-McLaughlin effect indicate that the orbital angular momentum vector of some planets is inclined relative to the spin axis of their host stars. This diversity could be induced by post-formation dynamical processes such as planet-planet scattering, the Kozai effect, or secular chaos which brings planets to the vicinity of their host stars. In this work, we propose a novel mechanism to form close-inmore » super-Earths and Neptune-like planets through the tidal disruption of gas giant planets as a consequence of these dynamical processes. We model the core-envelope structure of gas giant planets with composite polytropes which characterize the distinct chemical composition of the core and envelope. Using three-dimensional hydrodynamical simulations of close encounters between Jupiter-like planets and their host stars, we find that the presence of a core with a mass more than 10 times that of the Earth can significantly increase the fraction of envelope which remains bound to it. After the encounter, planets with cores are more likely to be retained by their host stars in contrast with previous studies which suggested that coreless planets are often ejected. As a substantial fraction of their gaseous envelopes is preferentially lost while the dense incompressible cores retain most of their original mass, the resulting metallicity of the surviving planets is increased. Our results suggest that some gas giant planets can be effectively transformed into either super-Earths or Neptune-like planets after multiple close stellar passages. Finally, we analyze the orbits and structure of known planets and Kepler candidates and find that our model is capable of producing some of the shortest-period objects.« less

13th Annual P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet

EPA Pesticide Factsheets

The EPA, as part of the P3-People, Prosperity and the Planet Award Program, is seeking applications proposing to research, develop, and design solutions to real world challenges involving the overall sustainability of human society.

TRAPPIST-1 Planet Lineup

NASA Image and Video Library

2017-02-22

This artist's concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets' diameters, masses and distances from the host star. The system has been revealed through observations from NASA's Spitzer Space Telescope and the ground-based TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) telescope, as well as other ground-based observatories. The system was named for the TRAPPIST telescope. The seven planets of TRAPPIST-1 are all Earth-sized and terrestrial, according to research published in 2017 in the journal Nature. TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its planets orbit very close to it. They are likely all tidally locked, meaning the same face of the planet is always pointed at the star, as the same side of our moon is always pointed at Earth. This creates a perpetual night side and perpetual day side on each planet. TRAPPIST-1b and c receive the most light from the star and would be the warmest. TRAPPIST-1e, f and g all orbit in the habitable zone, the area where liquid water is most likely to be detected. But any of the planets could potentially harbor liquid water, depending on their compositions. In the imagined planets shown here, TRAPPIST-1b is shown as a larger analogue to Jupiter's moon Io. TRAPPIST-1d is depicted with a narrow band of water near the terminator, the divide between a hot, dry day and an ice-covered night side. TRAPPIST-1e and TRAPPIST-1f are both shown covered in water, but with progressively larger ice caps on the night side. TRAPPIST-1g is portrayed with an atmosphere like Neptune's, although it is still a rocky world. TRAPPIST-1h, the farthest from the star, would be the coldest. It is portrayed here as an icy world, similar to Jupiter's moon Europa, but the least is known about it. http://photojournal.jpl.nasa.gov/catalog/PIA21422

Artist concept of SIM PlanetQuest Artist Concept

NASA Image and Video Library

2002-12-21

Artist's concept of the current mission configuration. SIM PlanetQuest (formerly called Space Interferometry Mission), currently under development, will determine the positions and distances of stars several hundred times more accurately than any previous program. This accuracy will allow SIM to determine the distances to stars throughout the galaxy and to probe nearby stars for Earth-sized planets. SIM will open a window to a new world of discoveries. http://photojournal.jpl.nasa.gov/catalog/PIA04248

Taking the Temperature of a Lava Planet

NASA Astrophysics Data System (ADS)

Kreidberg, Laura; Lopez, Eric; Cowan, Nick; Lupu, Roxana; Stevenson, Kevin; Louden, Tom; Malavolta, Luca

2018-05-01

Ultra-short period rocky planets (USPs) are an exotic class of planet found around less than 1% of stars. With orbital periods shorter than 24 hours, these worlds are blasted with stellar radiation that is expected to obliterate any traces of a primordial atmosphere and melt the dayside surface into a magma ocean. Observations of USPs have yielded several surprising results, including the measurement of an offset hotspot in the thermal phase curve of 55 Cancri e (which may indicate a thick atmosphere has survived), and a high Bond albedo for Kepler-10b, which suggests the presence of unusually reflective lava on its surface. To further explore the properties of USPs and put these results in context, we propose to observe a thermal phase curve of the newly discovered USP K2- 141b. This planet is a rocky world in a 6.7 hour orbit around a bright, nearby star. When combined with optical phase curve measured by K2, our observations will uniquely determine the planet's Bond albedo, precisely measure the offset of the thermal curve, and determine the temperature of the dayside surface. These results will cement Spitzer's role as a pioneer in the study of terrestrial planets beyond the Solar System, and provide a critical foundation for pursuing the optimal follow-up strategy for K2-141b with JWST.

Detectability of molecular signatures in the atmospheres of Giant and Terrestrial Exoplanets

NASA Astrophysics Data System (ADS)

Tinetti, G. T.; Vidal-Madjar, A.; Lecavelier Des Etangs, A.; Ehrenreich, D.; Liang, M. C.; Yung, Y.

In the past decade over 160 planets orbiting other stars extrasolar planets were discovered using indirect detection techniques The known sample is constrained by the currently achievable detection techniques which are more sensitive to larger worlds To extend the detection ability down to Earth-sized planets both the European Space Agency ESA and National Aeronautics and Space Administration NASA are developing large and technologically challenging space-borne observatories The first of these missions is due for launch as early as 2015 and will provide our first opportunity to spectroscopically study the global characteristics of Earth-like planets beyond our solar system to search for signs of habitability and life Almost a decade in advance to the launch of ESA-Darwin or NASA-Terrestrial Planet Finders most recent observations of primary and secondary eclipses with Hubble Space Telescope and Spitzer of transiting extrasolar giant planets EGPs Charbonneau et al 2002 2005 Vidal-Madjar et al 2003 2004 Deming et al 2005 suggest that emitted and transmission spectra of EGPs can be used to infer many properties of their atmospheres and internal structure including chemical element abundances hydrodynamic escape cloud heights temperature-pressure profiles density composition and evolution The next generation of space telescopes James Webb Space Telescope JWST will have the capability of acquiring more precise spectra in the visible and infrared of these extrasolar worlds The ultimate extension of such searches will be to

A Dynamical Analysis of the Kepler-80 System of Five Transiting Planets

NASA Astrophysics Data System (ADS)

MacDonald, Mariah G.; Ragozzine, Darin; Fabrycky, Daniel C.; Ford, Eric B.; Holman, Matthew J.; Isaacson, Howard T.; Lissauer, Jack J.; Lopez, Eric D.; Mazeh, Tsevi; Rogers, Leslie; Rowe, Jason F.; Steffen, Jason H.; Torres, Guillermo

2016-10-01

Kepler has discovered hundreds of systems with multiple transiting exoplanets which hold tremendous potential both individually and collectively for understanding the formation and evolution of planetary systems. Many of these systems consist of multiple small planets with periods less than ∼50 days known as Systems with Tightly spaced Inner Planets, or STIPs. One especially intriguing STIP, Kepler-80 (KOI-500), contains five transiting planets: f, d, e, b, and c with periods of 1.0, 3.1, 4.6, 7.1, and 9.5 days, respectively. We provide measurements of transit times and a transit timing variation (TTV) dynamical analysis. We find that TTVs cannot reliably detect eccentricities for this system, though mass estimates are not affected. Restricting the eccentricity to a reasonable range, we infer masses for the outer four planets (d, e, b, and c) to be {6.75}-0.51+0.69, {4.13}-0.95+0.81, {6.93}-0.70+1.05, and {6.74}-0.86+1.23 Earth masses, respectively. The similar masses but different radii are consistent with terrestrial compositions for d and e and ∼2% H/He envelopes for b and c. We confirm that the outer four planets are in a rare dynamical configuration with four interconnected three-body resonances that are librating with few degree amplitudes. We present a formation model that can reproduce the observed configuration by starting with a multi-resonant chain and introducing dissipation. Overall, the information-rich Kepler-80 planets provide an important perspective into exoplanetary systems.

Characterizing Pale Blue Dots Around FGKM Stars

NASA Astrophysics Data System (ADS)

Rugheimer, S.; Kaltenegger, L.; Sasselov, D. D.; Segura, A.

2015-12-01

Exoplanet characterization of small rocky worlds will be a main focus in the coming decades. For future telescopes like JWST and UVOIR/HDST, an exoplanet's host star will influence our ability to detect and interpret spectral features, including biosignatures. We present a complete suit of stellar models and a grid of model atmospheres for Earth-like planets at equivalent stages of geological evolution in their HZ for stellar effective temperature from Teff = 2300K to 7000K, sampling the entire FGKM stellar type range. Since M dwarfs are simultaneously the most numerous in the universe, the most active, and the most likely stars to host terrestrial exoplanets, we focus in particular on the range of UV emission possible in each sub M spectral class. The UV emission from a planet's host star dominates the photochemistry and thus the resultant observable spectral features of the planet. Using the latest UV spectra obtained by HST and IUE we model the effect of stellar activity on Earth-like planets. We also model the amount of UV flux reaching the surface for Earth-like planets at various geological epochs ranging from a pre-biotic world through the rise of oxygen and for Earth-like planets orbiting FGKM stars at equivalent stages of evolution. When modeling the remotely detectable spectra of these planets we focus on the primary detectable atmospheric features that indicate habitability on Earth, namely: H2O, CO2, O3, CH4, N2O and CH3Cl. We model the emergent as well as transit spectra of Earth-like planets orbiting our grid of FGKM stars in the VIS/NIR (0.4 - 4 μm) and the IR (5 - 20 μm) range as input for future missions like JWST and concepts like UVOIR/HDST.

Climate Dynamics and Hysteresis at Low and High Obliquity

NASA Astrophysics Data System (ADS)

Colose, C.; Del Genio, A. D.; Way, M.

2017-12-01

We explore the large-scale climate dynamics at low and high obliquity for an Earth-like planet using the ROCKE-3D (Resolving Orbital and Climate Keys of Earth and Extraterrestrial Environments with Dynamics) 3-D General Circulation model being developed at NASA GISS as part of the Nexus for Exoplanet System Science (NExSS) initiative. We highlight the role of ocean heat storage and transport in determining the seasonal cycle at high obliquity, and describe the large-scale circulation and resulting regional climate patterns using both aquaplanet and Earth topographical boundary conditions. Finally, we contrast the hysteresis structure to varying CO2 concentration for a low and high obliquity planet near the outer edge of the habitable zone. We discuss the prospects for habitability for a high obliquity planet susceptible to global glaciation.

Constraints on planetary formation from the discovery & study of transiting Extrasolar Planets

NASA Astrophysics Data System (ADS)

Triaud, A. H. M. J.

2011-08-01

After centuries of wondering about the presence of other worlds outside our Solar System, the first extrasolar planets were discovered about fifteen years ago. Since the quest continued. The greatest discovery of our new line of research, exoplanetology, has probably been the large diversity that those new worlds have brought forward; a diversity in mass, in size, in orbital periods, as well as in the architecture of the systems we discover. Planets very different from those composing our system have been detected. As such, we found hot Jupiters, gas giants which orbital period is only of a few days, mini-Neptunes, bodies five to ten time the mass of the Earth but covered by a thick gas layer, super-Earths of similar masses but rocky, lava worlds, and more recently, maybe the first ocean planet. Many more surprises probably await us. This thesis has for subject this very particular planet class: the hot Jupiters. Those astonishing worlds are still badly understood. Yet, thanks to the evolution of observational techniques and of the treatment of their signals, we probably have gathered as much knowledge from these worlds, than what was known of our own gas giants prior to their visit by probes. They are laboratories for a series of intense physical phenomena caused by their proximity to their star. Notably, these planets are found in average much larger than expected. In addition to these curiosities, their presence so close to their star is abnormal, the necessary conditions for the formation of such massive bodies, this close, not being plausible. Thus it is more reasonable to explain their current orbits by a formation far from their star, followed by an orbital migration. It is on this last subject that this thesis is on: the origin of hot Jupiters. The laws of physics are universal. Therefore, using the same physical phenomena, we need to explain the existence of hot Jupiters, while explaining why the Jupiter within our Solar System is found five times the Earth-Sun distance. In Astronomy, we cannot do experiments; we are a part of it. Instead, we search and characterise several similar objects in order to extract information out of them statistically. To answer our question, we needed to find several objects and detect the clues from their past history bringing us back to the processes that led to their formation. There are several manners with which one can find planets. For this thesis, the so-called transit method was used. It consists in detecting a periodic loss of light from a star in front of which a planet passes: a transit. This method is particularly sensitive to the presence of hot Jupiters. During this thesis, about fifty planets of such type have been discovered, about a third of the known hot Jupiters. Those planets are confirmed thanks to radial velocity measurements, the same technique that led to the discovery of the first extrasolar planet, around the star 51 Pegasi. The analysis of the stellar light affected by the presence of a planet around it, notably the light received during transit, allows us to know about the mass, the size of the planet, its orbital period, the shape of its orbit, its temperature, even the chemical composition of its atmosphere. Furthermore, these observations give us the occasion to study the star around which is found the planet, such as its mass, its size, its rotation speed, as well as give estimates on its age. One type of observations was employed in particular: the Rossiter-McLaughlin effect. During transit, this effect creates an anomaly compared to the expected radial velocities. Through a modelisation of this anomaly, it is possible to measure the projection of the angle between the orbital plane of the planet and the equatorial plane of the star, on the sky. In our System, all planets are located more or less in a same plane : the ecliptic. The equatorial plane of the Sun is also almost aligned with the ecliptic. This observation led Kant and Laplace to postulate on the formation of planets from matter spread in the form of a primordial disc around the Sun; such discs are nowadays observed around young stars. This angle was measured for the newly discovered planets, and, surprisingly, instead of observing planets in orbit above the equator of their star, a wide variety was found. Some planets are even in orbit in the direction counter to that which was expected. Those observations, combined with others of similar type, as well as with those already known parameters from that astonishing planet population, allow us to explore the phenomena that occurred probably soon after their formation. Those hot Jupiters have had an eventful history. When the disc in which they formed dissipated, gravitational interactions with other planets in the same system, or caused by the presence of another star in the system, have led those gas giants on inclined, some retrograde, and very elliptic orbits. During their regular passage at the closest point with their star, the dissipation of tidal forces within the planet and the star induced a circularisation and a reduction of their orbital periods, on which we observe them nowadays.

Virtually-Enhanced Fluid Laboratories for Teaching Meteorology

NASA Astrophysics Data System (ADS)

Marshall, J.; Illari, L.

2015-12-01

The Weather in a Tank (WIAT) project aims to offer instructors a repertoire of rotating tank experiments, and a curriculum in fluid dynamics, to better assist students in learning how to move between phenomena in the real world and basic principles of rotating fluid dynamics which play a central role in determining the climate of the planet. Despite the increasing use of laboratory experiments in teaching meteorology, however, we are aware that many teachers and students do not have access to suitable apparatus and so cannot benefit from them. Here we describe a 'virtually-enhanced' laboratory that we hope could be very effective in getting across a flavor of the experiments and bring them to a wider audience. In the pedagogical spirit of WIAT we focus on how simple underlying principles, illustrated through laboratory experiments, shape the observed structure of the large-scale atmospheric circulation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrovich, Cristobal; Rafikov, Roman; Tremaine, Scott, E-mail: cpetrovi@princeton.edu

Many exoplanets in close-in orbits are observed to have relatively high eccentricities and large stellar obliquities. We explore the possibility that these result from planet-planet scattering by studying the dynamical outcomes from a large number of orbit integrations in systems with two and three gas-giant planets in close-in orbits (0.05 AU < a < 0.15 AU). We find that at these orbital separations, unstable systems starting with low eccentricities and mutual inclinations (e ≲ 0.1, i ≲ 0.1) generally lead to planet-planet collisions in which the collision product is a planet on a low-eccentricity, low-inclination orbit. This result is inconsistentmore » with the observations. We conclude that eccentricity and inclination excitation from planet-planet scattering must precede migration of planets into short-period orbits. This result constrains theories of planet migration: the semi-major axis must shrink by 1-2 orders of magnitude without damping the eccentricity and inclination.« less

TRAPPIST-1 Planetary Orbits and Transits

NASA Image and Video Library

2017-02-22

This frame from a video details a system of seven planets orbiting TRAPPIST-1, an ultra-cool dwarf star. Spitzer was able to identify a total of seven rocky worlds, including three in the habitable zone where liquid water might be found. A study established the planets' size, distance from their sun and, for some of them, their approximate mass and density. It also established that some, if not all, of these planets are tidally locked, meaning one face of the planet permanently faces their sun. The system has been revealed through observations from NASA's Spitzer Space Telescope and the ground-based TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) telescope, as well as other ground-based observatories. The system was named for the TRAPPIST telescope. A video is available at http://photojournal.jpl.nasa.gov/catalog/PIA21427

Giant Impacts on Earth-Like Worlds

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-05-01

Earth has experienced a large number of impacts, from the cratering events that may have caused mass extinctions to the enormous impact believed to have formed the Moon. A new study examines whether our planets impact history is typical for Earth-like worlds.N-Body ChallengesTimeline placing the authors simulations in context of the history of our solar system (click for a closer look). [Quintana et al. 2016]The final stages of terrestrial planet formation are thought to be dominated by giant impacts of bodies in the protoplanetary disk. During this stage, protoplanets smash into one another and accrete, greatly influencing the growth, composition, and habitability of the final planets.There are two major challenges when simulating this N-body planet formation. The first is fragmentation: since computational time scales as N^2, simulating lots of bodies that split into many more bodies is very computationally intensive. For this reason, fragmentation is usually ignored; simulations instead assume perfect accretion during collisions.Total number of bodies remaining within the authors simulations over time, with fragmentation included (grey) and ignored (red). Both simulations result in the same final number of bodies, but the ones that include fragmentation take more time to reach that final number. [Quintana et al. 2016]The second challengeis that many-body systems are chaotic, which means its necessary to do a large number of simulations to make statistical statements about outcomes.Adding FragmentationA team of scientists led by Elisa Quintana (NASA NPP Senior Fellow at the Ames Research Center) has recently pushed at these challenges by modeling inner-planet formation using a code that does include fragmentation. The team ran 140 simulations with and 140 without the effects of fragmentation using similar initial conditions to understand how including fragmentation affects the outcome.Quintana and collaborators then used the fragmentation-inclusive simulations to examine the collisional histories of Earth-like planets that form. Their goal is to understand if our solar systems formation and evolution is typical or unique.How Common Are Giant Impacts?Histogram of the total number of giant impacts received by the 164 Earth-like worlds produced in the authors fragmentation-inclusive simulations. [Quintana et al. 2016]The authors find that including fragmentation does not affect the final number of planets that are formed in the simulation (an average of 34 in each system, consistent with our solar systems terrestrial planet count). But when fragmentation is included, fewer collisions end in merger which results in typical accretion timescales roughly doubling. So the effects of fragmentation influence the collisional history of the system and the length of time needed for the final system to form.Examining the 164 Earth-analogs produced in the fragmentation-inclusive simulations, Quintana and collaborators find that impacts large enough to completely strip a planets atmosphere are rare; fewer than 1% of the Earth-like worlds experienced this.But giant impacts that are able to strip ~50% of an Earth-analogs atmosphere roughly the energy of the giant impact thought to have formed our Moon are more common. Almost all of the authors Earth-analogs experienced at least 1 giant impact of this size in the 2-Gyr simulation, and the average Earth-like world experienced ~3 such impacts.These results suggest that our planets impact history with the Moon-forming impact likely being the last giant impact Earth experienced is fairly typical for Earth-like worlds. The outcomes also indicate that smaller impacts that are still potentially life-threatening are much more common than bulk atmospheric removal. Higher-resolution simulations could be used to examine such smaller impacts.CitationElisa V. Quintana et al 2016 ApJ 821 126. doi:10.3847/0004-637X/821/2/126

Dynamical models to explain observations with SPHERE in planetary systems with double debris belts

NASA Astrophysics Data System (ADS)

Lazzoni, C.; Desidera, S.; Marzari, F.; Boccaletti, A.; Langlois, M.; Mesa, D.; Gratton, R.; Kral, Q.; Pawellek, N.; Olofsson, J.; Bonnefoy, M.; Chauvin, G.; Lagrange, A. M.; Vigan, A.; Sissa, E.; Antichi, J.; Avenhaus, H.; Baruffolo, A.; Baudino, J. L.; Bazzon, A.; Beuzit, J. L.; Biller, B.; Bonavita, M.; Brandner, W.; Bruno, P.; Buenzli, E.; Cantalloube, F.; Cascone, E.; Cheetham, A.; Claudi, R. U.; Cudel, M.; Daemgen, S.; De Caprio, V.; Delorme, P.; Fantinel, D.; Farisato, G.; Feldt, M.; Galicher, R.; Ginski, C.; Girard, J.; Giro, E.; Janson, M.; Hagelberg, J.; Henning, T.; Incorvaia, S.; Kasper, M.; Kopytova, T.; LeCoroller, H.; Lessio, L.; Ligi, R.; Maire, A. L.; Ménard, F.; Meyer, M.; Milli, J.; Mouillet, D.; Peretti, S.; Perrot, C.; Rouan, D.; Samland, M.; Salasnich, B.; Salter, G.; Schmidt, T.; Scuderi, S.; Sezestre, E.; Turatto, M.; Udry, S.; Wildi, F.; Zurlo, A.

2018-03-01

Context. A large number of systems harboring a debris disk show evidence for a double belt architecture. One hypothesis for explaining the gap between the debris belts in these disks is the presence of one or more planets dynamically carving it. For this reason these disks represent prime targets for searching planets using direct imaging instruments, like the Spectro-Polarimetric High-constrast Exoplanet Research (SPHERE) at the Very Large Telescope. Aim. The goal of this work is to investigate this scenario in systems harboring debris disks divided into two components, placed, respectively, in the inner and outer parts of the system. All the targets in the sample were observed with the SPHERE instrument, which performs high-contrast direct imaging, during the SHINE guaranteed time observations. Positions of the inner and outer belts were estimated by spectral energy distribution fitting of the infrared excesses or, when available, from resolved images of the disk. Very few planets have been observed so far in debris disks gaps and we intended to test if such non-detections depend on the observational limits of the present instruments. This aim is achieved by deriving theoretical predictions of masses, eccentricities, and semi-major axes of planets able to open the observed gaps and comparing such parameters with detection limits obtained with SPHERE. Methods: The relation between the gap and the planet is due to the chaotic zone neighboring the orbit of the planet. The radial extent of this zone depends on the mass ratio between the planet and the star, on the semi-major axis, and on the eccentricity of the planet, and it can be estimated analytically. We first tested the different analytical predictions using a numerical tool for the detection of chaotic behavior and then selected the best formula for estimating a planet's physical and dynamical properties required to open the observed gap. We then apply the formalism to the case of one single planet on a circular or eccentric orbit. We then consider multi-planetary systems: two and three equal-mass planets on circular orbits and two equal-mass planets on eccentric orbits in a packed configuration. As a final step, we compare each couple of values (Mp, ap), derived from the dynamical analysis of single and multiple planetary models, with the detection limits obtained with SPHERE. Results: For one single planet on a circular orbit we obtain conclusive results that allow us to exclude such a hypothesis since in most cases this configuration requires massive planets which should have been detected by our observations. Unsatisfactory is also the case of one single planet on an eccentric orbit for which we obtained high masses and/or eccentricities which are still at odds with observations. Introducing multi planetary architectures is encouraging because for the case of three packed equal-mass planets on circular orbits we obtain quite low masses for the perturbing planets which would remain undetected by our SPHERE observations. The case of two equal-mass planets on eccentric orbits is also of interest since it suggests the possible presence of planets with masses lower than the detection limits and with moderate eccentricity. Our results show that the apparent lack of planets in gaps between double belts could be explained by the presence of a system of two or more planets possibly of low mass and on eccentric orbits whose sizes are below the present detection limits. Based on observations collected at Paranal Observatory, ESO (Chile) Program ID: 095.C-0298, 096.C-0241, 097.C-0865, and 198.C-0209.

Dynamical history of the asteroid belt and implications for terrestrial pla net bombardment

NASA Astrophysics Data System (ADS)

Minton, David Andrew

The main asteroid belt spans ~ 2-4 AU in heliocentric distance and is sparsely populated by rocky debris. The dynamical structure of the main belt records clues to past events in solar system history. Evidence from the structure of the Kuiper belt, an icy debris belt beyond Neptune, suggests that the giant planets were born in a more compact configuration and later experienced planetesimal-driven planet migration. Giant planet migration caused both mean motion and secular resonances to sweep across the main asteroid belt, raising the eccentricity of asteroids into planet-crossing orbits and depleting the belt. I show that the present-day semimajor axis and eccentricity distributions of large main belt asteroids are consistent with excitation and depletion due to resonance sweeping during the epoch of giant planet migration. I also use an analytical model of the sweeping of the n 6 secular resonance, to set limits on the migration speed of Saturn. After planet migration, dynamical chaos became the dominant loss mechanism for asteroids with diameters D [Special characters omitted.] 10 km in the current asteroid belt. I find that the dynamical loss history of test particles from this region is well described with a logarithmic decay law. My model suggests that the rate of impacts from large asteroids may have declined by a factor of three over the last ~ 3 Gy, and that the present-day impact flux of D > 10 km objects on the terrestrial planets is roughly an order of magnitude less than estimates used in crater chronologies and impact hazard risk assessments. Finally, I have quantified the change in the solar wind 6 Li/ 7 Li ratio due to the estimated in-fall of chondritic material and enhanced dust production during the epoch of planetesimal-driven giant planet migration. The solar photosphere is currently highly depleted in lithium relative to chondrites, and 6 Li is expected to be far less abundant in the sun than 7 Li due to the different nuclear reaction rates of the two isotopes. Evidence for a short- lived impact cataclysm that affected the entire inner solar system may be found in the composition of implanted solar wind particles in lunar regolith.

The New Solar System: China’s Evolving Solar Industry and Its Implications for Competitive Solar Power in the United States and the World

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ball, Jeffrey; Reicher, Dan; Sun, Xiaojing

Solar power is undergoing a revolution. Over the past decade, an energy source as old as the planet and theoretically all but limitless has plummeted in cost and begun in some places to be harnessed in large volume. This dynamic is disrupting the modern energy system and, as energy disruptions always do, rattling the geopolitical order. In the process, the industry that produces the equipment to convert sunlight into electricity is simultaneously reeling, consolidating, and surging. These twin transformations—one of the global energy system, one of the global solar industry—carry profound implications for national economies and for the planet. Atmore » the center of both transformations sits China. The New Solar System illuminates key and little- understood changes that are remaking the solar enterprise—in China and thus in the world. Based on this analysis, it recommends changes in U.S. solar policy—particularly timely with a new U.S. administration and Congress—that would put solar power on a more economically sensible path toward environmentally significant growth. The New Solar System does not seek to enable any country to beat another in the global solar industry. It seeks instead to help all countries find their most effective places. By better understanding and playing to their comparative strengths in the solar business, countries would achieve two key objectives. They would reduce the cost for the world of scaling up solar power. And they would be better positioned to fashion policies that maximized the long-term benefit to their own economies from solar’s global growth.« less

A World Worth Living in ICAE 8th World Assembly Declaration (June 2011)

ERIC Educational Resources Information Center

Adult Learning, 2012

2012-01-01

This article presents the International Council of Adult Education (ICAE) 8th World Assembly Declaration (June 2011). This declaration focuses on adult educators' conviction in the possibility of a "world worth living in," and their declaration of their collective determination to work towards making it a reality all around the planet.

Optical performance of the New Worlds Occulter

NASA Astrophysics Data System (ADS)

Arenberg, Jonathan W.; Lo, Amy S.; Glassman, Tiffany M.; Cash, Webster

2007-04-01

The New Worlds Observer (NWO) is a multiple spacecraft mission that is capable of detecting and characterizing extra-solar planets and planetary systems. NWO consists of an external occulter and a generic space telescope, flying in tandem. The external occulter has specific requirements on its shape and size, while the telescope needs no special modification beyond that required to do high-quality astrophysical observations. The occulter is a petal-shaped, opaque screen that creates a high-suppression shadow large enough to accommodate the telescope. This article reports on the optical performance of the novel New Worlds occulter design. It also introduces two new aspects of its optical performance which enhance the detectability of extra-solar planets. We also include a brief discussion of the buildability and the tolerances of the occulter. It is also shown that an occulter design can be found for any set of science requirements. We show that NWO is a viable mission concept for the study of extra-solar planets. To cite this article: J.W. Arenberg et al., C. R. Physique 8 (2007).

Hot, Rocky World Artist Concept

NASA Image and Video Library

2015-07-30

This artist's rendition shows one possible appearance for the planet HD 219134b, the nearest confirmed rocky exoplanet found to date outside our solar system. The planet is 1.6 times the size of Earth, and whips around its star in just three days. Scientists predict that the scorching-hot planet -- known to be rocky through measurements of its mass and size -- would have a rocky, partially molten surface with geological activity, including possibly volcanoes. http://photojournal.jpl.nasa.gov/catalog/PIA19833

Masses of Kepler-46b, c from Transit Timing Variations

NASA Astrophysics Data System (ADS)

Saad-Olivera, Ximena; Nesvorný, David; Kipping, David M.; Roig, Fernando

2017-04-01

We use 16 quarters of the Kepler mission data to analyze the transit timing variations (TTVs) of the extrasolar planet Kepler-46b (KOI-872). Our dynamical fits confirm that the TTVs of this planet (period P={33.648}-0.005+0.004 days) are produced by a non-transiting planet Kepler-46c (P={57.325}-0.098+0.116 days). The Bayesian inference tool MultiNest is used to infer the dynamical parameters of Kepler-46b and Kepler-46c. We find that the two planets have nearly coplanar and circular orbits, with eccentricities ≃ 0.03 somewhat higher than previously estimated. The masses of the two planets are found to be {M}b={0.885}-0.343+0.374 and {M}c={0.362}-0.016+0.016 Jupiter masses, with M b being determined here from TTVs for the first time. Due to the precession of its orbital plane, Kepler-46c should start transiting its host star a few decades from now.

The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ranjan, Sukrit; Sasselov, Dimitar D.; Wordsworth, Robin, E-mail: sranjan@cfa.harvard.edu

Potentially habitable planets orbiting M dwarfs are of intense astrobiological interest because they are the only rocky worlds accessible to biosignature search over the next 10+ years because of a confluence of observational effects. Simultaneously, recent experimental and theoretical work suggests that UV light may have played a key role in the origin of life on Earth, especially the origin of RNA. Characterizing the UV environment on M-dwarf planets is important for understanding whether life as we know it could emerge on such worlds. In this work, we couple radiative transfer models to observed M-dwarf spectra to determine the UVmore » environment on prebiotic Earth-analog planets orbiting M dwarfs. We calculate dose rates to quantify the impact of different host stars on prebiotically important photoprocesses. We find that M-dwarf planets have access to 100–1000 times less bioactive UV fluence than the young Earth. It is unclear whether UV-sensitive prebiotic chemistry that may have been important to abiogenesis, such as the only known prebiotically plausible pathways for pyrimidine ribonucleotide synthesis, could function on M-dwarf planets. This uncertainty affects objects like the recently discovered habitable-zone planets orbiting Proxima Centauri, TRAPPIST-1, and LHS 1140. Laboratory studies of the sensitivity of putative prebiotic pathways to irradiation level are required to resolve this uncertainty. If steady-state M-dwarf UV output is insufficient to power these pathways, transient elevated UV irradiation due to flares may suffice; laboratory studies can constrain this possibility as well.« less

The Surface UV Environment on Planets Orbiting M Dwarfs: Implications for Prebiotic Chemistry and the Need for Experimental Follow-up

NASA Astrophysics Data System (ADS)

Ranjan, Sukrit; Wordsworth, Robin; Sasselov, Dimitar D.

2017-07-01

Potentially habitable planets orbiting M dwarfs are of intense astrobiological interest because they are the only rocky worlds accessible to biosignature search over the next 10+ years because of a confluence of observational effects. Simultaneously, recent experimental and theoretical work suggests that UV light may have played a key role in the origin of life on Earth, especially the origin of RNA. Characterizing the UV environment on M-dwarf planets is important for understanding whether life as we know it could emerge on such worlds. In this work, we couple radiative transfer models to observed M-dwarf spectra to determine the UV environment on prebiotic Earth-analog planets orbiting M dwarfs. We calculate dose rates to quantify the impact of different host stars on prebiotically important photoprocesses. We find that M-dwarf planets have access to 100–1000 times less bioactive UV fluence than the young Earth. It is unclear whether UV-sensitive prebiotic chemistry that may have been important to abiogenesis, such as the only known prebiotically plausible pathways for pyrimidine ribonucleotide synthesis, could function on M-dwarf planets. This uncertainty affects objects like the recently discovered habitable-zone planets orbiting Proxima Centauri, TRAPPIST-1, and LHS 1140. Laboratory studies of the sensitivity of putative prebiotic pathways to irradiation level are required to resolve this uncertainty. If steady-state M-dwarf UV output is insufficient to power these pathways, transient elevated UV irradiation due to flares may suffice; laboratory studies can constrain this possibility as well.

Dynamics of a Probable Earth-mass Planet in the GJ 832 System

NASA Astrophysics Data System (ADS)

Satyal, S.; Griffith, J.; Musielak, Z. E.

2017-08-01

The stability of planetary orbits around the GJ 832 star system, which contains inner (GJ 832c) and outer (GJ 832b) planets, is investigated numerically and a detailed phase-space analysis is performed. Special attention is given to the existence of stable orbits for a planet less than 15 M ⊕ that is injected between the inner and outer planets. Thus, numerical simulations are performed for three and four bodies in elliptical orbits (or circular for special cases) by using a large number of initial conditions that cover the selected phase-spaces of the planet’s orbital parameters. The results presented in the phase-space maps for GJ 832c indicate the least deviation of eccentricity from its nominal value, which is then used to determine its inclination regime relative to the star-outer planet plane. Also, the injected planet is found to display stable orbital configurations for at least one billion years. Then, the radial velocity curves based on the signature from the Keplerian motion are generated for the injected planets with masses 1 M ⊕ to 15 M ⊕ in order to estimate their semimajor axes and mass limits. The synthetic RV signal suggests that an additional planet of mass ≤15 M ⊕ with a dynamically stable configuration may be residing between 0.25 and 2.0 au from the star. We have provided an estimated number of RV observations for the additional planet that is required for further observational verification.

Spin-orbit coupling and tidal dissipation in hot Jupiter systems

NASA Astrophysics Data System (ADS)

Shabaltas, Natalia Igorevna

Hot Jupiters are giant planets located extremely close to their host stars, with orbital periods less than 5 days. Many aspects of hot Jupiter (HJ) formation remain unclear, but several clues, such as the observed misalignment between their orbital axes and their hosts' spin axes, point to a dynamical origin. In the first portion of this work we explore the stellar spin-orbit dynamics of one such dynamical formation channel, the Lidov-Kozai mechanism. We show that the coupling between the stellar spin and the planet orbit can lead to complex, and sometimes chaotic, behavior of the stellar spin vector. Many features of this behavior arise due to a set of resonances between the stellar spin axis precession timescale and the Lidov-Kozai timescale. Under the assumption that the stellar quadrupole does not induce precession in the planet's orbit, given a system with a set of initial parameters, we show that it is possible to predict whether the system can attain high spin-orbit misalignments. In the second portion of this work, we discuss tidal dissipation in giant planets, another aspect that is crucial to dynamical HJ formation theories. We show that tidal dissipation in the cores of giant planets can be significant, and can help reconcile inconsistencies in the tidal dissipation efficiencies inferred from observations of Jupiter's moons and from high-eccentricity HJ migration theories. Finally, we improve upon existing core tidal dissipation theories by presenting semi-analytical formulae for dissipation in a core surrounded by a polytropic n = 1 envelope.

Addressing the statistical mechanics of planet orbits in the solar system

NASA Astrophysics Data System (ADS)

Mogavero, Federico

2017-10-01

The chaotic nature of planet dynamics in the solar system suggests the relevance of a statistical approach to planetary orbits. In such a statistical description, the time-dependent position and velocity of the planets are replaced by the probability density function (PDF) of their orbital elements. It is natural to set up this kind of approach in the framework of statistical mechanics. In the present paper, I focus on the collisionless excitation of eccentricities and inclinations via gravitational interactions in a planetary system. The future planet trajectories in the solar system constitute the prototype of this kind of dynamics. I thus address the statistical mechanics of the solar system planet orbits and try to reproduce the PDFs numerically constructed by Laskar (2008, Icarus, 196, 1). I show that the microcanonical ensemble of the Laplace-Lagrange theory accurately reproduces the statistics of the giant planet orbits. To model the inner planets I then investigate the ansatz of equiprobability in the phase space constrained by the secular integrals of motion. The eccentricity and inclination PDFs of Earth and Venus are reproduced with no free parameters. Within the limitations of a stationary model, the predictions also show a reasonable agreement with Mars PDFs and that of Mercury inclination. The eccentricity of Mercury demands in contrast a deeper analysis. I finally revisit the random walk approach of Laskar to the time dependence of the inner planet PDFs. Such a statistical theory could be combined with direct numerical simulations of planet trajectories in the context of planet formation, which is likely to be a chaotic process.

Possible Habitability of Ocean Worlds

NASA Astrophysics Data System (ADS)

Noack, Lena; Höning, Dennis; Bredehöft, Jan H.; Lammer, Helmut

2014-05-01

In the last decade, the number of detected exoplanets has increased to over thousand confirmed planets and more as yet unconfirmed planet candidates. The scientific community mainly concentrates on terrestrial planets (up to 10 Earth masses) in the habitable zone, which describes the distance from the host star where liquid water can exist at the surface (Kasting et al., 1993). Another target group of interest are ocean worlds, where a terrestrial-like body (i.e. with an iron core and a silicate mantle) is covered by a thick water-ice layer - similar to the icy moons of our solar system but with several Earth masses (e.g. Grasset et al., 2009). When an exoplanet is detected and confirmed as a planet, typically the radius and the mass of it are known, leading to the mean density of the planet that gives hints to possible interior structures. A planet with a large relative iron core and a thick ocean on top of the silicate mantle for example would have the same average planet density as a planet with a more Earth-like appearance (where the main contributor to the mass is the silicate mantle). In this study we investigate how the radius and mass of a planet depend on the amount of water, silicates and iron present (after Wagner et al., 2011) the occurence of high-pressure-ice in the water-ice layer (note: we only consider surface temperatures at which liquid water exists at the surface) if the ocean layer influences the initiation of plate tectonics We assume that ocean worlds with a liquid ocean layer (and without the occurence of high-pressure ice anywhere in the water layer) and plate tectonics (especially the occurence of subduction zones, hydrothermal vents and continental formation) may be called habitable (Class III/IV habitats after Lammer et al., 2009). References: Kasting, J.F., Whitmire, D.P., and Reynolds, R.T. (1993). Habitable Zones around Main Sequence Stars. Icarus 101, 108-128. Grasset, O., Schneider, J., and Sotin, C. (2009). A study of the accuracy of mass-radius relationships for silicate-rich and ice-rich planets up to 100 Earth masses. The Astrophysical Journal 693, 722-733. Wagner, F.W., Sohl, F., Hussmann, H., Grott, M., and Rauer, H. (2011). Interior structure models of solid exoplanets using material laws in the infinite pressure limit. Icarus 214, 366-376. Lammer, H., Bredehöft, J.H., Coustenis, A., Khodachenko, M.L., Kaltenegger, L., Grasset, O., Prieur, D., Raulin, F., Ehrenfreund, P., Yamauchi, M., Wahlund, J.-E., Grießmeier, J.-M., Stangl, G., Cockell, C.S., Kulikov, Yu.N., Grenfell, J.L., and Rauer, H. (2009). What makes a planet habitable? Astron Astrophys Rev 17, 181-249.

Planet Formation by Coagulation: A Focus on Uranus and Neptune

NASA Astrophysics Data System (ADS)

Goldreich, Peter; Lithwick, Yoram; Sari, Re'em

2004-09-01

Planets form in the circumstellar disks of young stars. We review the basic physical processes by which solid bodies accrete each other and alter each others' random velocities, and we provide order-of-magnitude derivations for the rates of these processes. We discuss and exercise the two-groups approximation, a simple yet powerful technique for solving the evolution equations for protoplanet growth. We describe orderly, runaway, neutral, and oligarchic growth. We also delineate the conditions under which each occurs. We refute a popular misconception by showing that the outer planets formed quickly by accreting small bodies. Then we address the final stages of planet formation. Oligarchy ends when the surface density of the oligarchs becomes comparable to that of the small bodies. Dynamical friction is no longer able to balance viscous stirring and the oligarchs' random velocities increase. In the inner-planet system, oligarchs collide and coalesce. In the outer-planet system, some of the oligarchs are ejected. In both the inner- and outer-planet systems, this stage ends once the number of big bodies has been reduced to the point that their mutual interactions no longer produce large-scale chaos. Subsequently, dynamical friction by the residual small bodies circularizes and flattens their orbits. The final stage of planet formation involves the clean up of the residual small bodies. Clean up has been poorly explored.

Solar System Evolution through Planetesmial Collisions

NASA Astrophysics Data System (ADS)

Trierweiler, Isabella; Laughlin, Greg

2018-01-01

Understanding planet formation is crucial to unraveling the history of our Solar System. Refining our theory of planet formation has become particularly important as the discovery of exoplanet systems through missions like Kepler have indicated that our system is incredibly unique. Compared to other systems around Sun-like stars, we are missing a significant amount of mass in the inner region of our solar system.A leading explanation for the low mass of the terrestrial planets is Jupiter’s Grand Tack. In this theory, the existence of the rocky planets is thought to be the result of the migration of Jupiter through the inner solar system. This migration could spark a collisional cascade of planetesimals, allowing planetesimals to drift inwards and shepherd an original set of massive planets into the Sun, thus explaining the absence of massive planets in our current system. The remnants of the planetesimals would them become the building blocks for a new generation of smaller, rocky planets.Using the N-body simulator REBOUND, we investigate the dynamics of the Grand Tack. We focus in particular on collisional cascades, which are thought to cause the inward planetesimal drift. We first modify the simulator to account for fragmentation outcomes in planetesimal collisions. Modeling disks of varying initial conditions, we then characterize the disk conditions needed to begin a cascade and shed light on the solar system’s dynamics just prior to the formation of the terrestrial planets.

Coastal hazards: hurricanes, tsunamis, coastal erosion

USGS Publications Warehouse

Vandas, Stephen; Mersfelder, Lynne; Farrar, Frank; France, Rigoberto Guardado; Yajimovich, Oscar Efraín González; Muñoz, Aurora R.; Rivera, María del C.

1996-01-01

Oceans are the largest geographic feature on the surface of the Earth, covering approximately 70% of the planet's surface. As a result, oceans have a tremendous impact on the Earth, its climate, and its inhabitants. The coast or shoreline is the boundary between ocean environments and land habitats. By the year 2025, it is estimated that approximately two-thirds of the world's population will be living within 200 kilometers of a coast. In many ways, we treat the coast just like any other type of land area, as a safe and stable place to live and play. However, coastal environments are dynamic, and they constantly change in response to natural processes and to human activities.

Water World Artist Concept

NASA Image and Video Library

2017-04-12

This artist's concept shows a hypothetical planet covered in water around the binary star system of Kepler-35A and B. In a 2017 study in the journal Nature Communications, researchers investigating the climates of exoplanets determined that this hypothetical planet could be habitable, depending on its distance from the two stars. On the far edge of the habitable zone, the hypothetical water-covered planet would have a lot of variation in its surface temperatures. But closer to the stars, near the inner edge of the habitable zone, the global average surface temperatures on the same planet would stay almost constant. https://photojournal.jpl.nasa.gov/catalog/PIA21470

Dynamical simulations of the HR8799 planetary system

NASA Astrophysics Data System (ADS)

Marshall, J.; Horner, J.; Carter, A.

2010-10-01

HR8799 is a young (20-160 Myr) A-dwarf main sequence star with a debris disc detected by IRAS (InfraRed Astronomical Satellite). In 2008, it was one of two stars around which exoplanets were directly imaged for the first time. The presence of three Jupiter-mass planets around HR8799 provoked much interest in modelling the dynamical stability of the system. Initial simulations indicated that the observed planetary architecture was unstable on timescales much shorter than the lifetime of the star (~105 yr). Subsequent models suggested that the system could be stable if the planets were locked in a 1:2:4 mutual mean motion resonance (MMR). In this work, we have examined the influence of varying orbital eccentricity and the semi-major axis on the stability of the three-planet system, through dynamical simulations using the MERCURY n-body integrator. We find that, in agreement with previous work on this system, the 1:2:4 MMR is the most stable planetary configuration, and that the system stability is dominated by the interaction between the inner pair of planets. In contrast to previous results, we find that with small eccentricities, the three-planet system can be stable for timescales comparable to the system lifetime and, potentially, much longer.

Dynamics as a 'Red Flag' in Exoplanetary Science

NASA Astrophysics Data System (ADS)

Horner, Jonathan; Wittenmyer, Robert

2018-01-01

The great majority of exoplanets are discovered indirectly - by observing a star doing something unusual, and inferring the presence of planets from that behaviour. The nature of those planets - their mass and their orbital parameters - is typically somewhat unclear, with a variety of different scenarios offering equally good fits to the observational data.Typically, authors publish the solution that offers the best fit to the data, without considering the degree to which the planets propsed would interact with one another. This has led to the 'discovery' of planetary systems that are clearly unfeasible - and it is likely that a number of such systems are buried in the catalogue of 'confirmed' exoplanets.Fortunately, there is a solution to this problem. By carrying out suites of n-body integrations of proposed planetary systems, we can find solutions that both offer a good fit to the observational data and the long-term dynamical stability required to give confidence that the planets proposed are truly all they seem.Here, we present the results from a number of such dynamical studies, showing the importance of such simulations to the process of exoplanet discovery and characterisation.

Dynamics of the Final Stages of Terrestrial Planet Growth and the Formation of the Earth-Moon System

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Rivera, Eugenio J.; DeVincenzi, Donald (Technical Monitor)

2000-01-01

An overview of current theories of star and planet formation, with emphasis on terrestrial planet accretion and the formation of the Earth-Moon system is presented. These models predict that rocky planets should form around most single stars, although it is possible that in some cases such planets are lost to orbital decay within the protoplanetary disk. The frequency of formation of gas giant planets is more difficult to predict theoretically. Terrestrial planets are believed to grow via pairwise accretion until the spacing of planetary orbits becomes large enough that the configuration is stable for the age of the system. Giant impacts during the final stages of growth can produce large planetary satellites, such as Earth's Moon. Giant planets begin their growth like terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates.

Hydrodynamic Simulations of Unevenly Irradiated Jovian Planets

NASA Astrophysics Data System (ADS)

Langton, Jonathan; Laughlin, Gregory

2008-02-01

We employ a two-dimensional, grid-based hydrodynamic model to simulate upper atmospheric dynamics on extrasolar giant planets. The hydrodynamic equations of motion are integrated on a rotating, irradiated sphere using a pseudospectral algorithm. We use a two-frequency, two-stream approximation of radiative transfer to model the temperature forcing. This model is well suited to simulate the dynamics of the atmospheres of planets with high orbital eccentricity, which are subject to widely varying irradiation conditions. We identify six such planets, with eccentricities between e = 0.28 and e = 0.93 and semimajor axes from a = 0.0508 AU to a = 0.432 AU, as particularly interesting. For each, we determine the temperature profile and resulting infrared light curves in the 8 μm Spitzer band. Especially notable are the results for HD 80606b, which has the largest eccentricity (e = 0.9321) of any known planet, and HAT-P-2b, which transits its parent star, so that its physical properties are well constrained. Despite the varied orbital parameters, the atmospheric dynamics of these planets display a number of interesting common properties. In all cases, the atmospheric response is primarily driven by the intense irradiation at periastron. The resulting expansion of heated air produces high-velocity turbulent flow, including long-lived circumpolar vortices. In addition, a superrotating acoustic front develops on some planets; the strength of this disturbance depends on both the eccentricity and the temperature gradient from uneven heating. The specifics of the resulting infrared light curves depend strongly on the orbital geometry. We show, however, that the variations on HD 80606b and HAT-P-2b should be readily detectable at 4.5 and 8 μm using Spitzer. These two objects present the most attractive observational targets of all known high-e exoplanets.

The TRAPPIST-1 Habitable Zone

NASA Image and Video Library

2017-02-22

The TRAPPIST-1 system contains a total of seven planets, all around the size of Earth. Three of them -- TRAPPIST-1e, f and g -- dwell in their star's so-called "habitable zone." The habitable zone, or Goldilocks zone, is a band around every star (shown here in green) where astronomers have calculated that temperatures are just right -- not too hot, not too cold -- for liquid water to pool on the surface of an Earth-like world. While TRAPPIST-1b, c and d are too close to be in the system's likely habitable zone, and TRAPPIST-1h is too far away, the planets' discoverers say more optimistic scenarios could allow any or all of the planets to harbor liquid water. In particular, the strikingly small orbits of these worlds make it likely that most, if not all of them, perpetually show the same face to their star, the way our moon always shows the same face to the Earth. This would result in an extreme range of temperatures from the day to night sides, allowing for situations not factored into the traditional habitable zone definition. The illustrations shown for the various planets depict a range of possible scenarios of what they could look like. The system has been revealed through observations from NASA's Spitzer Space Telescope and the ground-based TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) telescope, as well as other ground-based observatories. The system was named for the TRAPPIST telescope. http://photojournal.jpl.nasa.gov/catalog/PIA21424

TRAPPIST-1 Planet Animations

NASA Image and Video Library

2018-02-05

This still from a video shows illustrations of the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 40 light-years away, based on data current as of February 2018. Each planet is shown in sequence, starting with the innermost TRAPPIST-1b and ending with the outermost TRAPPIST-1h. The video presents the planets' relative sizes as well as the relative scale of the central star as seen from each planet. The art highlights possibilities for how the surfaces of these intriguing worlds might look based on their newly calculated properties. The seven planets of TRAPPIST-1 are all Earth-sized and terrestrial. TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its planets orbit very close to it. In the background, slightly distorted versions our familiar constellations, including Orion and Taurus, are shown as they would appear from the location of TRAPPIST-1 (backdrop image courtesy California Academy of Sciences/Dan Tell). An animation is available at https://photojournal.jpl.nasa.gov/catalog/PIA22098

Do We Only Die Once?

ERIC Educational Resources Information Center

Cangemi, Joseph P.

2014-01-01

Some individuals believe physical death is the only form of death we experience on this planet. Is such a belief valid? In the Western world, essentially, physical death is seen as the end of life on this planet. It's all over "here." But is physical death really the only form of death experienced while on earth? Physical death is the…

Orbital Architectures of Dynamically Complex Exoplanet Systems

NASA Astrophysics Data System (ADS)

Nelson, Benjamin E.

2015-01-01

The most powerful constraints on planet formation will come from characterizing the dynamical state of complex multi-planet systems. Unfortunately, with that complexity comes a number of factors that make analyzing these systems a computationally challenging endeavor: the sheer number of model parameters, a wonky shaped posterior distribution, and hundreds to thousands of time series measurements. We develop a differential evolution Markov chain Monte Carlo (RUN DMC) to tackle these difficult aspects of data analysis. We apply RUN DMC to two classic multi-planet systems from radial velocity surveys, 55 Cancri and GJ 876. For 55 Cancri, we find the inner-most planet "e" must be coplanar to within 40 degrees of the outer planets, otherwise Kozai-like perturbations will cause the planet's orbit to cross the stellar surface. We find the orbits of planets "b" and "c" are apsidally aligned and librating with low to median amplitude (50±610 degrees), but they are not orbiting in a mean-motion resonance. For GJ 876, we can meaningfully constrain the three-dimensional orbital architecture of all the planets based on the radial velocity data alone. By demanding orbital stability, we find the resonant planets have low mutual inclinations (Φ) so they must be roughly coplanar (Φcb = 1.41±0.620.57 degrees and Φbe = 3.87±1.991.86 degrees). The three-dimensional Laplace argument librates with an amplitude of 50.5±7.910.0 degrees, indicating significant past disk migration and ensuring long-term stability. These empirically derived models will provide new challenges for planet formation models and motivate the need for more sophisticated algorithms to analyze exoplanet data.

The sustainability of habitability on terrestrial planets: Insights, questions, and needed measurements from Mars for understanding the evolution of Earth-like worlds

NASA Astrophysics Data System (ADS)

Ehlmann, B. L.; Anderson, F. S.; Andrews-Hanna, J.; Catling, D. C.; Christensen, P. R.; Cohen, B. A.; Dressing, C. D.; Edwards, C. S.; Elkins-Tanton, L. T.; Farley, K. A.; Fassett, C. I.; Fischer, W. W.; Fraeman, A. A.; Golombek, M. P.; Hamilton, V. E.; Hayes, A. G.; Herd, C. D. K.; Horgan, B.; Hu, R.; Jakosky, B. M.; Johnson, J. R.; Kasting, J. F.; Kerber, L.; Kinch, K. M.; Kite, E. S.; Knutson, H. A.; Lunine, J. I.; Mahaffy, P. R.; Mangold, N.; McCubbin, F. M.; Mustard, J. F.; Niles, P. B.; Quantin-Nataf, C.; Rice, M. S.; Stack, K. M.; Stevenson, D. J.; Stewart, S. T.; Toplis, M. J.; Usui, T.; Weiss, B. P.; Werner, S. C.; Wordsworth, R. D.; Wray, J. J.; Yingst, R. A.; Yung, Y. L.; Zahnle, K. J.

2016-10-01

What allows a planet to be both within a potentially habitable zone and sustain habitability over long geologic time? With the advent of exoplanetary astronomy and the ongoing discovery of terrestrial-type planets around other stars, our own solar system becomes a key testing ground for ideas about what factors control planetary evolution. Mars provides the solar system's longest record of the interplay of the physical and chemical processes relevant to habitability on an accessible rocky planet with an atmosphere and hydrosphere. Here we review current understanding and update the timeline of key processes in early Mars history. We then draw on knowledge of exoplanets and the other solar system terrestrial planets to identify six broad questions of high importance to the development and sustaining of habitability (unprioritized): (1) Is small planetary size fatal? (2) How do magnetic fields influence atmospheric evolution? (3) To what extent does starting composition dictate subsequent evolution, including redox processes and the availability of water and organics? (4) Does early impact bombardment have a net deleterious or beneficial influence? (5) How do planetary climates respond to stellar evolution, e.g., sustaining early liquid water in spite of a faint young Sun? (6) How important are the timescales of climate forcing and their dynamical drivers? Finally, we suggest crucial types of Mars measurements (unprioritized) to address these questions: (1) in situ petrology at multiple units/sites; (2) continued quantification of volatile reservoirs and new isotopic measurements of H, C, N, O, S, Cl, and noble gases in rocks that sample multiple stratigraphic sections; (3) radiometric age dating of units in stratigraphic sections and from key volcanic and impact units; (4) higher-resolution measurements of heat flux, subsurface structure, and magnetic field anomalies coupled with absolute age dating. Understanding the evolution of early Mars will feed forward to understanding the factors driving the divergent evolutionary paths of the Earth, Venus, and thousands of small rocky extrasolar planets yet to be discovered.

The Sustainability of Habitability on Terrestrial Planets: Insights, Questions, and Needed Measurements from Mars for Understanding the Evolution of Earth-Like Worlds

NASA Technical Reports Server (NTRS)

Ehlmann, B. L.; Anderson, F. S.; Andrews-Hanna, J.; Catling, D. C.; Christensen, P. R.; Cohen, B. A.; Dressing, C. D.; Edwards, C. S.; Elkins-Tanton, L. T.; Farley, K. A.;

The size distribution of inhabited planets

NASA Astrophysics Data System (ADS)

Simpson, Fergus

2016-02-01

Earth-like planets are expected to provide the greatest opportunity for the detection of life beyond the Solar system. However, our planet cannot be considered a fair sample, especially if intelligent life exists elsewhere. Just as a person's country of origin is a biased sample among countries, so too their planet of origin may be a biased sample among planets. The magnitude of this effect can be substantial: over 98 per cent of the world's population live in a country larger than the median. In the context of a simple model where the mean population density is invariant to planet size, we infer that a given inhabited planet (such as our nearest neighbour) has a radius r < 1.2r⊕ (95 per cent confidence bound). We show that this result is likely to hold not only for planets hosting advanced life, but also for those which harbour primitive life forms. Further, inferences may be drawn for any variable which influences population size. For example, since population density is widely observed to decline with increasing body mass, we conclude that most intelligent species are expected to exceed 300 kg.

THE EFFECT OF PLANET-PLANET SCATTERING ON THE SURVIVAL OF EXOMOONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong Yanxiang; Zhou Jilin; Xie Jiwei

2013-05-20

Compared to the giant planets in the solar system, exoplanets have many remarkable properties, such as the prevalence of giant planets on eccentric orbits and the presence of hot Jupiters. Planet-planet scattering (PPS) between giant planets is a possible mechanism to interpret the above and other observed properties. If the observed giant planet architectures are indeed outcomes of PPS, such a drastic dynamical process must affect their primordial moon systems. In this Letter, we discuss the effect of PPS on the survival of exoplanets' regular moons. From an observational viewpoint, some preliminary conclusions are drawn from the simulations. (1) PPSmore » is a destructive process to the moon systems; single planets on eccentric orbits are not ideal moon-search targets. (2) If hot Jupiters formed through PPS, their original moons have little chance of survival. (3) Planets in multiple systems with small eccentricities are more likely to hold their primordial moons. (4) Compared with lower-mass planets, massive planets in multiple systems may not be the preferred moon-search targets if the system underwent a PPS history.« less

World Ships - Architectures & Feasibility Revisited

NASA Astrophysics Data System (ADS)

Hein, A. M.; Pak, M.; Putz, D.; Buhler, C.; Reiss, P.

A world ship is a concept for manned interstellar flight. It is a huge, self-contained and self-sustained interstellar vehicle. It travels at a fraction of a per cent of the speed of light and needs several centuries to reach its target star system. The well- known world ship concept by Alan Bond and Anthony Martin was intended to show its principal feasibility. However, several important issues haven't been addressed so far: the relationship between crew size and robustness of knowledge transfer, reliability, and alternative mission architectures. This paper addresses these gaps. Furthermore, it gives an update on target star system choice, and develops possible mission architectures. The derived conclusions are: a large population size leads to robust knowledge transfer and cultural adaptation. These processes can be improved by new technologies. World ship reliability depends on the availability of an automatic repair system, as in the case of the Daedalus probe. Star systems with habitable planets are probably farther away than systems with enough resources to construct space colonies. Therefore, missions to habitable planets have longer trip times and have a higher risk of mission failure. On the other hand, the risk of constructing colonies is higher than to establish an initial settlement on a habitable planet. Mission architectures with precursor probes have the potential to significantly reduce trip and colonization risk without being significantly more costly than architectures without. In summary world ships remain an interesting concept, although they require a space colony-based civilization within our own solar system before becoming feasible.

Outer planet probe engineering model structural tests

NASA Technical Reports Server (NTRS)

Smittkamp, J. A.; Gustin, W. H.; Griffin, M. W.

1977-01-01

A series of proof of concept structural tests was performed on an engineering model of the Outer Planets Atmospheric Entry Probe. The tests consisted of pyrotechnic shock, dynamic and static loadings. The tests partially verified the structural concept.

Hydrodynamic outcomes of planet scattering in transitional discs

NASA Astrophysics Data System (ADS)

Moeckel, Nickolas; Armitage, Philip J.

2012-01-01

A significant fraction of unstable multiple planet systems are likely to scatter during the transitional disc phase as gas damping becomes ineffectual. Using a large ensemble of FARGO hydrodynamic simulations and MERCURY N-body integrations, we directly follow the dynamics of planet-disc and planet-planet interactions through the clearing phase and through 50 Myr of planetary system evolution. Disc clearing is assumed to occur as a result of X-ray-driven photoevaporation. We find that the hydrodynamic evolution of individual scattering systems is complex, and can involve phases in which massive planets orbit within eccentric gaps, or accrete directly from the disc without a gap. Comparing the results to a reference gas-free model, we find that the N-body dynamics and hydrodynamics of scattering into one- and two-planet final states are almost identical. The eccentricity distributions in these channels are almost unaltered by the presence of gas. The hydrodynamic simulations, however, also form a population of low-eccentricity three-planet systems in long-term stable configurations, which are not found in N-body runs. The admixture of these systems results in modestly lower eccentricities in hydrodynamic as opposed to gas-free simulations. The precise incidence of these three-planet systems is likely a function of the initial conditions; different planet set-ups (number or spacing) may change the quantitative character of this result. We analyse the properties of surviving multiple planet systems, and show that only a small fraction (a few per cent) enter mean motion resonances after scattering, while a larger fraction form stable resonant chains and avoid scattering entirely. Our results remain consistent with the hypothesis that exoplanet eccentricity results from scattering, though the detailed agreement between observations and gas-free simulation results is likely coincidental. We discuss the prospects for further tests of scattering models by observing planets or non-axisymmetric gas structure in transitional discs.

Dynamical Stability of Imaged Planetary Systems in Formation: Application to HL Tau

NASA Astrophysics Data System (ADS)

Tamayo, D.; Triaud, A. H. M. J.; Menou, K.; Rein, H.

2015-06-01

A recent Atacama Large Millimeter/Submillimeter Array image revealed several concentric gaps in the protoplanetary disk surrounding the young star HL Tau. We consider the hypothesis that these gaps are carved by planets, and present a general framework for understanding the dynamical stability of such systems over typical disk lifetimes, providing estimates for the maximum planetary masses. We collect these easily evaluated constraints into a workflow that can help guide the design and interpretation of new observational campaigns and numerical simulations of gap opening in such systems. We argue that the locations of resonances should be significantly shifted in massive disks like HL Tau, and that theoretical uncertainties in the exact offset, together with observational errors, imply a large uncertainty in the dynamical state and stability in such disks. This presents an important barrier to using systems like HL Tau as a proxy for the initial conditions following planet formation. An important observational avenue to breaking this degeneracy is to search for eccentric gaps, which could implicate resonantly interacting planets. Unfortunately, massive disks like HL Tau should induce swift pericenter precession that would smear out any such eccentric features of planetary origin. This motivates pushing toward more typical, less massive disks. For a nominal non-resonant model of the HL Tau system with five planets, we find a maximum mass for the outer three bodies of approximately 2 Neptune masses. In a resonant configuration, these planets can reach at least the mass of Saturn. The inner two planets’ masses are unconstrained by dynamical stability arguments.

Habitable zone limits for dry planets.

PubMed

Abe, Yutaka; Abe-Ouchi, Ayako; Sleep, Norman H; Zahnle, Kevin J

2011-06-01

Most discussion of habitable planets has focused on Earth-like planets with globally abundant liquid water. For an "aqua planet" like Earth, the surface freezes if far from its sun, and the water vapor greenhouse effect runs away if too close. Here we show that "land planets" (desert worlds with limited surface water) have wider habitable zones than aqua planets. For planets at the inner edge of the habitable zone, a land planet has two advantages over an aqua planet: (i) the tropics can emit longwave radiation at rates above the traditional runaway limit because the air is unsaturated and (ii) the dry air creates a dry stratosphere that limits hydrogen escape. At the outer limits of the habitable zone, the land planet better resists global freezing because there is less water for clouds, snow, and ice. Here we describe a series of numerical experiments using a simple three-dimensional global climate model for Earth-sized planets. Other things (CO(2), rotation rate, surface pressure) unchanged, we found that liquid water remains stable at the poles of a low-obliquity land planet until net insolation exceeds 415 W/m(2) (170% that of modern Earth), compared to 330 W/m(2) (135%) for the aqua planet. At the outer limits, we found that a low-obliquity land planet freezes at 77%, while the aqua planet freezes at 90%. High-obliquity land and aqua planets freeze at 58% and 72%, respectively, with the poles offering the last refuge. We show that it is possible that, as the Sun brightens, an aqua planet like Earth can lose most of its hydrogen and become a land planet without first passing through a sterilizing runaway greenhouse. It is possible that Venus was a habitable land planet as recently as 1 billion years ago.

A septet of Earth-sized planets

NASA Astrophysics Data System (ADS)

Triaud, Amaury; SPECULOOS Team; TRAPPIST-1 Team

2017-10-01

Understanding the astronomical requirements for life to emerge, and to persist, on a planet is one of the most important and exciting scientific endeavours, yet without empirical answers. To resolve this, multiple planets whose sizes and surface temperatures are similar to the Earth, need to be discovered. Those planets also need to possess properties enabling detailed atmospheric characterisation with forthcoming facilities, from which chemical traces produced by biological activity can in principle be identified.I will describe a dedicated search for such planets called SPECULOOS. Our first detection is the TRAPPIST-1 system. Intensive ground-based and space-based observations have revealed that at least seven planets populate this system. We measured their radii and obtained first estimates of their masses thanks to transit-timing variations. I will describe our on-going observational efforts aiming to reduce our uncertainties on the planet properties. The incident flux on the planets ranges from Mercury to Ceres, comprising the Earth, and permitting climatic comparisons between each of those worlds such as is not possible within our Solar system. All seven planets have the potential to harbour liquid water on at least a fraction of their surfaces, given some atmospheric and geological conditions.

WASP-47 and the Origin of Hot Jupiters

NASA Astrophysics Data System (ADS)

Vanderburg, Andrew; Becker, Juliette; Latham, David W.; Adams, Fred; Bryan, Marta; Buchhave, Lars; Haywood, Raphaelle; Khain, Tali; Lopez, Eric; Malavolta, Luca; Mortier, Annelies; HARPS-N Consortium

2018-01-01

WASP-47 b is a transiting hot Jupiter in a system with two additional short-period transiting planets and a long-period outer Jovian companion. WASP-47 b is the only known hot Jupiter with such close-in companions and therefore may hold clues to the origins of hot Jupiter systems. We report on precise radial velocity observations of WASP-47 to measure planet masses and determine their orbits to high precision. Using these improved masses and orbital elements, we perform a dynamical analysis to constrain the inclination of the outer planet, which we find likely orbits near the same plane as the inner transiting system. A similar dynamical analysis for five other hot Jupiter systems with long-period companions around cool host stars (Teff < 6200 K) shows that these outer companions likely also orbit close to the plane of the hot Jupiters. These constraints disfavor hot Jupiter models involving strong dynamical interactions like Kozai-Lidov migration.

Pre-mare cratering and early solar system history

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wetherill, G.W.

1974-01-01

An evaluation of the application of the high extra-lunar flux in pre- mare times to more general problems of early solar system history is attempted by combining the results of dynamic studies with lunar chronological data. Dynamical studies permit separate evaluation of the possible sources for both the normal flux during the first 600 m.y. years of lunar history as well as the peak which apparently occurred 4.0 b.y. ago. Dynamical studies have been carried out in order to determine the extent to which a heliocentric flux could be confined to the Moon (and Earth). A Monte Carlo method hasmore » been used to calculate the relative impact rates of planet-crossing bodies with the moon and the terrestrial planets. It is concluded that the time-variation of the flux on these planets is closely related to that on the moon. (STAR)« less

Connection Between the ICRF and the Dynamical Reference Frame for the Outer Planets

NASA Astrophysics Data System (ADS)

da Silva Neto, D. N.; Assafin, M.; Andrei, A. H.; Vieira Martins, R.

2005-01-01

This work brings an approach intending to improve the connection between the Dynamical Reference Frame and the Extragalactic Reference Frame. For that, close encounters of outer Solar System objects and quasars are used. With this goal, Uranus, Neptune and two quasars were observed at Laborat´orio Nacional de Astrof´ısica (LNA), Brazil. The optical reference frame is the HCRF, as given by the UCAC2 catalogue. The first results show an accuracy of 45 mas - 50 mas in the optical positions. The optical minus radio offsets give the local orientation between the catalogue and radio frame. From this, it is possible to place the optical planet coordinates on the extragalactic frame. A comparison between the new corrected optical coordinates and the respective DE ephemeris to these planets can give the instant orientations of the Dynamical Reference Frame with regard to the ICRS, for this zone of outer Solar System.

Demarcating Circulation Regimes of Synchronously Rotating Terrestrial Planets within the Habitable Zone

NASA Astrophysics Data System (ADS)

Haqq-Misra, Jacob; Wolf, Eric. T.; Joshi, Manoj; Zhang, Xi; Kopparapu, Ravi Kumar

2018-01-01

We investigate the atmospheric dynamics of terrestrial planets in synchronous rotation within the habitable zone of low-mass stars using the Community Atmosphere Model. The surface temperature contrast between the day and night hemispheres decreases with an increase in incident stellar flux, which is opposite the trend seen in gas giants. We define three dynamical regimes in terms of the equatorial Rossby deformation radius and the Rhines length. The slow rotation regime has a mean zonal circulation that spans from the day to the night sides, which occurs for planets around stars with effective temperatures of 3300–4500 K (rotation period > 20 days), with both the Rossby deformation radius and the Rhines length exceeding the planetary radius. Rapid rotators have a mean zonal circulation that partially spans a hemisphere and with banded cloud formation beneath the substellar point, which occurs for planets orbiting stars with effective temperatures of less than 3000 K (rotation period < 5 days), with the Rossby deformation radius less than the planetary radius. In between is the Rhines rotation regime, which retains a thermally direct circulation from the day side to the night side but also features midlatitude turbulence-driven zonal jets. Rhines rotators occur for planets around stars in the range of 3000–3300 K (rotation period ∼5–20 days), where the Rhines length is greater than the planetary radius but the Rossby deformation radius is less than the planetary radius. The dynamical state can be observationally inferred from a comparison of the morphologies of the thermal emission phase curves of synchronously rotating planets.

PlanetPack: A radial-velocity time-series analysis tool facilitating exoplanets detection, characterization, and dynamical simulations

NASA Astrophysics Data System (ADS)

Baluev, Roman V.

2013-08-01

We present PlanetPack, a new software tool that we developed to facilitate and standardize the advanced analysis of radial velocity (RV) data for the goal of exoplanets detection, characterization, and basic dynamical N-body simulations. PlanetPack is a command-line interpreter, that can run either in an interactive mode or in a batch mode of automatic script interpretation. Its major abilities include: (i) advanced RV curve fitting with the proper maximum-likelihood treatment of unknown RV jitter; (ii) user-friendly multi-Keplerian as well as Newtonian N-body RV fits; (iii) use of more efficient maximum-likelihood periodograms that involve the full multi-planet fitting (sometimes called as “residual” or “recursive” periodograms); (iv) easily calculatable parametric 2D likelihood function level contours, reflecting the asymptotic confidence regions; (v) fitting under some useful functional constraints is user-friendly; (vi) basic tasks of short- and long-term planetary dynamical simulation using a fast Everhart-type integrator based on Gauss-Legendre spacings; (vii) fitting the data with red noise (auto-correlated errors); (viii) various analytical and numerical methods for the tasks of determining the statistical significance. It is planned that further functionality may be added to PlanetPack in the future. During the development of this software, a lot of effort was made to improve the calculational speed, especially for CPU-demanding tasks. PlanetPack was written in pure C++ (standard of 1998/2003), and is expected to be compilable and useable on a wide range of platforms.

Reading the Signatures of Extrasolar Planets in Debris Disks

NASA Technical Reports Server (NTRS)

Kuchner, Marc J.

2009-01-01

An extrasolar planet sculpts the famous debris dish around Fomalhaut; probably ma ny other debris disks contain planets that we could locate if only we could better recognize their signatures in the dust that surrounds them. But the interaction between planets and debris disks involves both orbital resonances and collisions among grains and rocks in the disks --- difficult processes to model simultanemus]y. I will describe new 3-D models of debris disk dynamics that incorporate both collisions and resonant trapping of dust for the first time, allowing us to decode debris disk images and read the signatures of the planets they contain.

TOWARD A DETERMINISTIC MODEL OF PLANETARY FORMATION. VII. ECCENTRICITY DISTRIBUTION OF GAS GIANTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ida, S.; Lin, D. N. C.; Nagasawa, M., E-mail: ida@geo.titech.ac.jp, E-mail: lin@ucolick.org, E-mail: nagasawa.m.ad@m.titech.ac.jp

2013-09-20

The ubiquity of planets and diversity of planetary systems reveal that planet formation encompasses many complex and competing processes. In this series of papers, we develop and upgrade a population synthesis model as a tool to identify the dominant physical effects and to calibrate the range of physical conditions. Recent planet searches have led to the discovery of many multiple-planet systems. Any theoretical models of their origins must take into account dynamical interactions between emerging protoplanets. Here, we introduce a prescription to approximate the close encounters between multiple planets. We apply this method to simulate the growth, migration, and dynamicalmore » interaction of planetary systems. Our models show that in relatively massive disks, several gas giants and rocky/icy planets emerge, migrate, and undergo dynamical instability. Secular perturbation between planets leads to orbital crossings, eccentricity excitation, and planetary ejection. In disks with modest masses, two or less gas giants form with multiple super-Earths. Orbital stability in these systems is generally maintained and they retain the kinematic structure after gas in their natal disks is depleted. These results reproduce the observed planetary mass-eccentricity and semimajor axis-eccentricity correlations. They also suggest that emerging gas giants can scatter residual cores to the outer disk regions. Subsequent in situ gas accretion onto these cores can lead to the formation of distant (∼> 30 AU) gas giants with nearly circular orbits.« less

Innermost Planets of the Solar System

NASA Technical Reports Server (NTRS)

1974-01-01

The appearance and characteristics of Mercury and Venus as evening and morning stars are discussed. Inferior and superior conjunction are defined. The motions, phases, and planetary dynamics of the two planets are compared with those of the earth and moon.

Status of the Planet Formation Imager (PFI) concept

NASA Astrophysics Data System (ADS)

Ireland, Michael J.; Monnier, John D.; Kraus, Stefan; Isella, Andrea; Minardi, Stefano; Petrov, Romain; ten Brummelaar, Theo; Young, John; Vasisht, Gautam; Mozurkewich, David; Rinehart, Stephen; Michael, Ernest A.; van Belle, Gerard; Woillez, Julien

2016-08-01

The Planet Formation Imager (PFI) project aims to image the period of planet assembly directly, resolving structures as small as a giant planet's Hill sphere. These images will be required in order to determine the key mechanisms for planet formation at the time when processes of grain growth, protoplanet assembly, magnetic fields, disk/planet dynamical interactions and complex radiative transfer all interact - making some planetary systems habitable and others inhospitable. We will present the overall vision for the PFI concept, focusing on the key technologies and requirements that are needed to achieve the science goals. Based on these key requirements, we will define a cost envelope range for the design and highlight where the largest uncertainties lie at this conceptual stage.

Dynamical Effects of Stellar Companions

NASA Astrophysics Data System (ADS)

Naoz, Smadar

2016-10-01

The fraction of stellar binaries in the field is extremely high (about 40% - 70% forM > 1M⊙ stars), and thus, given this frequency, a high fraction of all exoplanetary systems may reside in binaries. While close-in giant planets tend to be found preferentially in binary stellar systems it seems that the frequency of giant planets in close binaries (>100-1000 AU) is significantly lower than in the overall population. Stellar companions gravitational perturbations may significantly alter the planetary orbits around their partner on secular timescales. They can drive planets to large eccentric orbits which can either result in plunging these planets into the star or shrinking their orbits and forming short period planets. These planets typically are misaligned with the parent star.

Hera - an ESA M-class Saturn Entry Probe Mission Proposal

NASA Astrophysics Data System (ADS)

Atkinson, D. H.; Mousis, O.; Spilker, T. R.; Venkatapathy, E.; Poncy, J.; Coustenis, A.; Reh, K. R.

2015-12-01

A fundamental goal of solar system exploration is to understand the origin of the solar system, the initial stages, conditions, and processes by which the solar system formed, how the formation process was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Additionally, the atmospheres of the giant planets serve as laboratories to better understand the atmospheric chemistries, dynamics, processes, and climates on all planets in the solar system including Earth, offer a context and provide a ground truth for exoplanets and exoplanetary systems, and have long been thought to play a critical role in the development of potentially habitable planetary systems. Remote sensing observations are limited when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the value of in situ measurements is provided by measurements of Jupiter's noble gas abundances and helium mixing ratio by the Galileo probe. In situ measurements provide direct access to atmospheric regions that are beyond the reach of remote sensing, enabling the dynamical, chemical and aerosol-forming processes at work from the thermosphere to the troposphere below the cloud decks to be studied. Studies for a newly proposed Saturn atmospheric entry probe mission named Hera is being prepared for the upcoming European Space Agency Medium Class (M5) mission announcement of opportunity. A solar powered mission, Hera will take approximately 8 years to reach Saturn and will carry instruments to measure the composition, structure, and dynamics of Saturn's atmosphere. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Saturn, the Hera Saturn probe will provide critical measurements of composition, structure, and processes that are not accessible by remote sensing. The results of Hera will help test competing theories of solar system and giant planet origin, chemical, and dynamical evolution.

Illustration of TRAPPIST-1 Planets as of Feb. 2018

NASA Image and Video Library

2018-02-05

This illustration shows the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 40 light-years away, based on data current as of February 2018. The image shows the planets' relative sizes but does not represent their orbits to scale. The art highlights possibilities for how the surfaces of these intriguing worlds might look based on their newly calculated properties. The seven planets of TRAPPIST-1 are all Earth-sized and terrestrial. TRAPPIST-1 is an ultra-cool dwarf star in the constellation Aquarius, and its planets orbit very close to it. In the background, slightly distorted versions the familiar constellations of Orion and Taurus are shown as they would appear from the location of TRAPPIST-1 (courtesy of California Academy of Sciences/Dan Tell). https://photojournal.jpl.nasa.gov/catalog/PIA22097

ARTIST'S CONCEPT -- 'HOT JUPITER' AROUND THE STAR HD 209458

NASA Technical Reports Server (NTRS)

2002-01-01

This is an artist's impression of the gas-giant planet orbiting the yellow, Sun-like star HD 209458, 150 light-years from Earth. Astronomers used NASA's Hubble Space Telescope to look at this world and make the first direct detection of an atmosphere around an extrasolar planet. The planet was not directly seen by Hubble. Instead, the presence of sodium was detected in light filtered through the planet's atmosphere when it passed in front of its star as seen from Earth (an event called a transit). The planet was discovered in 1999 by its subtle gravitational pull on the star. The planet is 70 percent the mass of Jupiter, the largest planet in our solar system. Its orbit is tilted nearly edge-on to Earth, which allows repeated transit observations. The planet is merely 4 million miles from the star. The distance between the pair is so close that the yellow star looms in the sky, with an angular diameter 23 times larger than the full Moon's diameter as seen from Earth, and glows 500 times brighter than our Sun. At this precarious distance the planet's atmosphere is heated to 2000 degrees Fahrenheit (1100 degrees Celsius). But the planet is big enough to hold onto its seething atmosphere. Illustration Credit: NASA and Greg Bacon (STScI/AVL)

Planetary Origin Evolution and Structure

NASA Technical Reports Server (NTRS)

Stevenson, David J.

2005-01-01

This wide-ranging grant supported theoretical modeling on many aspects of the formation, evolution and structure of planets and satellites. Many topics were studied during this grant period, including the evolution of icy bodies; the origin of magnetic fields in Ganymede; the thermal histories of terrestrial planets; the nature of flow inside giant planets (especially the coupling to the magnetic field) and the dynamics of silicate/iron mixing during giant impacts and terrestrial planet core formation. Many of these activities are ongoing and have not reached completion. This is the nature of this kind of research.

Habitable Planetary Systems (un)like our own: Which of the Known Extra-Solar Systems Could Harbor Earth-like Planets?

NASA Astrophysics Data System (ADS)

Raymond, Sean; Mandell, A.; Sigurdsson, S.

2006-12-01

Gas giant planets are far easier than terrestrial planets to detect around other stars, and are thought to form much more quickly than terrestrial planets. Thus, in systems with giant planets, the final stages of terrestrial planet formation are strongly affected by the giant planets' dynamical presence. Observations of giant planet orbits may therefore constrain the systems that can harbor potentially habitable, Earth-like planets. We combine two recent studies (1,2) and establish rough inner and outer limits for the giant planet orbits that allow terrestrial planets of at least 0.3 Earth masses to form in the habitable zone (HZ). For a star like the Sun, potentially habitable planets can form in systems with relatively low-eccentricity giant planets inside 0.5 Astronomical Units (AU) or outside 2.5 AU. More than one third of the currently known giant planet systems could have formed and now harbor a habitable planet. We thank NASA Astrobiology Institute for funding, through the Penn State, NASA Goddard, Virtual Planetary Laboratory, and University of Colorado lead teams. (1. Raymond, S.N., 2006, ApJ, 643, L131.; 2. Raymond, S.N., Mandell, A.M., Sigurdsson, S. 2006, Science, 313, 1413).

A Bewildering and Dynamic Picture of Exoplanetary Systems Identified by the Kepler Mission (Invited)

NASA Astrophysics Data System (ADS)

Jenkins, J. M.

2013-12-01

Kepler vaulted into the heavens on March 7, 2009, initiating NASA's search for Earth-size planets orbiting Sun-like stars in the habitable zone, where liquid water could exist on a rocky planetary surface. In the 4 years since, a flood of photometric data of unprecedented precision and continuity on more than 190,000 stars has provoked a watershed of 134+ confirmed or validated planets, 3200+ planetary candidates (most sub-Neptune in size and many comparable to or smaller than Earth), and a revolution in asteroseismology and astrophysics. Recent discoveries include Kepler-62 with 5 planets total, of which 2 are in the habitable zone with radii of 1.4 and 1.7 Re. Approximately 500 of the stars in the Kepler survey with planets host multiple transiting planets: 43% of planet candidates have transiting siblings. Many of these multiple transiting planet systems are dynamically packed and are unlikely, therefore, to have formed in situ. These systems experienced strong migration and evolution to arrive at the configurations we observe today, with important implications for the time-variable habitability of these planets over their histories. The half dozen circumbinary transiting planet systems discovered by Kepler to date highlight the dynamic nature of the habitable zone in systems with multiple host stars where the habitable zone may change significantly on timescales commensurate with the orbital period of the binary. While the catalog of circumbinary planets is small at this point, it already possesses at least one example of an exoplanet in the habitable zone. This implies that the majority of habitable zone planets may be circumbinary planets given the high frequency of multiple star systems and the early detection of Kepler-47b. KIC-12557548 is most likely a disintegrating sub-Mercury-sized planet. While it was probably never habitable, it represents a unique example of the dynamic nature of planetary systems. These amazing discoveries challenge our conventional notion of the habitable zone for single stars and static planetary system configurations. This talk will provide an overview of the science results from the Kepler Mission and the work ahead to derive the frequency of Earth-size planets in the habitable zone of solar-like stars from the treasure trove of Kepler data. NASA's quest for exoplanets continues with the Transiting Exoplanet Survey Satellite (TESS) mission, slated for launch in May 2017 by NASA's Explorer Program. TESS will conduct an all- sky transit survey to identify the 1000 best small exoplanets in the solar neighborhood for follow up observations and characterization. TESS's targets will include all F, G, K dwarfs from +4 to +12 magnitude and all M dwarfs known within ~200 light-years. 500,000 target stars will be observed over two years with ~500 square degrees observed continuously for a year in each hemisphere in the James Webb Space Telescopes continuously viewable zones. Since the typical TESS target star is 5 magnitudes brighter than that of Kepler and 10 times closer, TESS discoveries will afford significant opportunities to measure the masses of the exoplanets and to characterize their atmospheres with JWST, ELTs and other exoplanet explorers. TESS' discoveries will raise new questions regarding habitability that will be open to investigation through active efforts to characterize their atmospheres and search for biomarkers. Funding for this mission is provided by NASA's Science Mission Directorate.

Planet Earth, 1984-2034: A Demographic Vision.

ERIC Educational Resources Information Center

Bouvier, Leon F.

1984-01-01

In recognition of the 1984 World Population Conference, this booklet examines the current state of world population and presents speculations on what it might be 50 years from now. World population, now close to 4.8 billion and growing at 1.8 percent a year, is being shaped by three demographic phenomena: prolonged below-replacement fertility in…

Raising Children Who Care for Our World

ERIC Educational Resources Information Center

O'Brien, Leigh M.

2007-01-01

If global warming has an upside, it may be the development of an enhanced awareness of the environment and the dangers faced due to profligate and destructive habits. The ways in which most people live in the industrialized world separate those from the natural world and hence make it difficult for them to understand and care about the planet that…

The effects of circumstellar gas on terrestrial planet formation: Theory and observation

NASA Astrophysics Data System (ADS)

Mandell, Avram M.

Our understanding of the evolution of circumstellar material from dust and gas to fully-formed planets has taken dramatic steps forward in the last decade, driven by rapid improvements in our ability to study gas- and dust-rich disks around young stars and the discovery of more than 200 extra-solar planetary systems around other stars. In addition, our ability to model the formation of both terrestrial and giant planets has improved significantly due to new computing techniques and the continued exponential increase in computing power. In this dissertation I expand on existing theories of terrestrial planet formation to include systems similar to those currently being detected around nearby stars, and I develop new observational techniques to probe the chemistry of gas-rich circumstellar disks where such planetary systems may be forming. One of the most significant characteristics of observed extrasolar planetary systems is the presence of giant planets located much closer to their parent star than was thought to be possible. The presence of "Hot Jupiters", Jovian-mass planets with very short orbital periods detected around nearby main sequence stars, has been proposed to be primarily due to the inward migration of planets formed in orbits initially much further from the parent star. Close-in giant planets are thought to have formed in the cold outer regions of planetary systems and migrated inward, passing through the orbital parameter space occupied by the terrestrial planets in our own Solar System; the migration of these planets would have profound effects on the evolution of inner terrestrial planets in these systems. I first explore this scenario with numerical simulations showing that a significant fraction of terrestrial planets could survive the migration process; damping forces could then eventually re-circularize the orbits at distances relatively close to their original positions. Calculations suggest that the final orbits of a significant fraction of the remaining planets would be located in the Habitable Zone, suggesting that planetary systems with close-in giant planets are viable targets for searches for Earth-like habitable planets around other stars. I then present more realistic dynamical simulations of the effects of a migrating giant planet on a disk of protoplanetary material embedded in a gaseous disk, and the subsequent post-scattering evolution of the planetary system. I numerically investigate the dynamics of several types of post-migration planetary systems over 200 million years: a model with a single migrating giant planet, a model with one migrating and one nonmigrating giant planet, and a model excluding the effects of the gas disk. Material that is shepherded in front of the migrating giant planet by moving mean motion resonances accretes into "hot Earths", but survival of these bodies is strongly dependent on dynamical damping. Furthermore, a significant amount of material scattered outward by the giant planet survives in highly excited orbits; the orbits of these scattered bodies are then damped by gas drag and dynamical friction over the remaining accretion time. In all simulations Earth-mass planets accrete on approximately 100 Myr timescales, often with orbits in the Habitable Zone. These planets range in mass and water content, with both quantities increasing with the presence of a gas disk and decreasing with the presence of an outer giant planet. I use scaling arguments and previous results to derive a simple recipe that constrains which giant planet systems are able to form and harbor Earth-like planets in the Habitable Zone, demonstrating that roughly one third of the known planetary systems are potentially habitable. Finally, I present results from a search for new molecular tracers of warm gas in circumstellar disks using the NIRSPEC instrument on the Keck II telescope. I have detected emission from multiple ro-vibrational transitions in the v = 1--0 band of hydroxyl (OH) located in the inner circumstellar regions of two Herbig Ae stars, AB Aurigae and MWC 758. I analyze the temperature of the emitting gas by constructing rotational diagrams, showing that the temperature of the gas in both systems is approximately 700K. I calculate a secure abundance of emitting OH molecules in the upper vibrational state, and discuss the ramifications of various excitation processes on the extrapolation to the total number of OH molecules. I also calculate an inner radius for the emitting gas, showing that the derived Rin is equivalent to that found by near-IR imaging. I compare these results to models of circumstellar disk chemistry as well as observations of other chemical diagnostics, and discuss further improvements to excitation models that are necessary to fully understand the formation and thermal conditions of the detected OH gas.

Origins and Destinations: Tracking Planet Composition through Planet Formation Simulations

NASA Astrophysics Data System (ADS)

Chance, Quadry; Ballard, Sarah

2018-01-01

There are now several thousand confirmed exoplanets, a number which far exceeds our resources to study them all in detail. In particular, planets around M dwarfs provide the best opportunity for in-depth study of their atmospheres by telescopes in the near future. The question of which M dwarf planets most merit follow-up resources is a pressing one, given that NASA’s TESS mission will soon find hundreds of such planets orbiting stars bright enough for both ground and spaced-based follow-up.Our work aims to predict the approximate composition of planets around these stars through n-body simulations of the last stage of planet formation. With a variety of initial disk conditions, we investigate how the relative abundances of both refractory and volatile compounds in the primordial planetesimals are mapped to the final planet outcomes. These predictions can serve to provide a basis for making an educated guess about (a) which planets to observe with precious resources like JWST and (b) how to identify them based on dynamical clues.

The Search for Young Planetary Systems And the Evolution of Young Stars

NASA Technical Reports Server (NTRS)

Beichman, Charles A.; Boden, Andrew; Ghez, Andrea; Hartman, Lee W.; Hillenbrand, Lynn; Lunine, Jonathan I.; Simon, Michael J.; Stauffer, John R.; Velusamy, Thangasamy

2004-01-01

The Space Interferometer Mission (SIM) will provide a census of planetary systems by con- ducting a broad survey of 2,000 stars that will be sensitive to the presence of planets with masses as small as approx. 15 Earth masses (1 Uranus mass) and a deep survey of approx. 250 of the nearest, stars with a mass limit of approx.3 Earth masses. The broad survey will include stars spanning a wide range of ages, spectral types, metallicity, and other important parameters. Within this larger context, the Young Stars and Planets Key Project will study approx. 200 stars with ages from 1 Myr to 100 Myr to understand the formation and dynamical evolution of gas giant planets. The SIM Young Stars and Planets Project will investigate both the frequency of giant planet formation and the early dynamical history of planetary systems. We will gain insight into how common the basic architecture of our solar system is compared with recently discovered systems with close-in giant planets by examining 200 of the nearest (less than 150 pc) and youngest (1-100 Myr) solar-type stars for planets. The sensitivity of the survey for stars located 140 pc away is shown in the planet mass-separation plane. We expect to find anywhere from 10 (assuming that only the presently known fraction of stars. 5-7%, has planets) to 200 (all young stars have planets) planetary systems. W-e have set our sensitivity threshold to ensure the detection of Jupiter-mass planets in the critical orbital range of 1 to 5 AU. These observations, when combined with the results of planetary searches of mature stars, will allow us to test theories of planetary formation and early solar system evolution. By searching for planets around pre-main sequence stars carefully selected to span an age range from 1 to 100 Myr, we will learn a t what epoch and with what frequency giant planets are found at the water-ice snowline where they are expected to form. This will provide insight into the physical mechanisms by which planets form and migrate from their place of birth, and about their survival rate. With these data in hand, we will provide data, for the first time, on such important questions as: What processes affect the formation and dynamical evolution of planets? When and where do planets form? What is initial mass distribution of planetary systems around young stars? How might planets be destroyed? What is the origin of the eccentricity of planetary orbits? What is the origin of the apparent dearth of companion objects between planets and brown dwarfs seen in mature stars? The observational strategy is a compromise between the desire to extend the planetary mass function as low as possible and the essential need to build up sufficient statistics on planetary occurrence. About half of the sample will be used to address the "where" and "when" of planet formation. We will study classical T Tauri stars (cTTs) which have massive accretion disks and post- accretion, weak-lined T Tauri stars (wTTs). Preliminary estimates suggest the sample will consist of approx. 30% cTTs and approx. 70% wTTs, driven in part by the difficulty of making accurate astrometric measurements toward objects with strong variability or prominent disks.

The dynamical structure of the HR8799 inner debris disk

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Contro de Godoy, Bruna; Horner, Jonathan; Marshall, Jonathan P.

2014-11-01

The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar System where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanet dynamics and debris disc-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disc remains unknown, leaving a question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using University of New South Wales's Katana supercomputing facility to follow the dynamical evolution of a model inner disc comprising 250,000 particles for a period of 100 million years. These simulations will (1) characterise the extent and structure of the inner disk in detail and (2) provide the first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet(s) in the inner system.

Vibration characteristics of two-stage planetary transmission system with thin-walled ring gear on elastic supports

NASA Astrophysics Data System (ADS)

Li, JianYing; Hu, QingChun; Zong, ChangFu; Zhu, TianJun; Zhang, ZeXing

2018-03-01

A dual-clutch and dual-speed planetary gears mechanism of a hybrid car coupled-system is taken as research subject, in which the ring gear of planet set II is a thin-walled structure and the clutch friction plates of planet set II are used as its elastic supports. Based on the lumped parameter-rigid elastic coupled dynamic model of two-stage planetary transmission system with thin-walled ring gear on elastic supports, the motion differential equations are established and the dynamic responses are solved by the Runge-Kutta method considering each stage internal and external time-varying mesh stiffness. The vibration displacements of each stage ring gear have been affected differently in time-domain, the translational vibration displacement of the ring gear of planet set I are obviously more than the torsional vibration displacement, but it is opposite for the ring gear of planet set II; The translational and torsional vibration responses of each stage ring gear arrive the peak in low-frequency. The analysis results of this paper can enrich the theoretical research of multistage planetary transmission and provide guidance for dynamic design.

Saving the Inner Solar System with an Early Instability

NASA Astrophysics Data System (ADS)

Clement, Matthew; Kaib, Nathan A.; Raymond, Sean N.; Walsh, Kevin J.

2018-04-01

An orbital instability between the solar system’s giant planets (the so-called Nice Model) has been shown to greatly disturb the orbits of the young terrestrial planets. Undesirable outcomes such as over-excitated orbits, ejections and collisions can be avoided if the instability occurs before the inner planets are fully formed. Such a scenario also has the advantage of limiting the mass and formation time of Mars when it occurs within several million years (Myr) of gas disk dissipation. The dynamical effects of the instability cause many small embryos and planetesimals to scatter away from the forming Mars, and lead to heavy mass depletion in the Asteroid Belt. We present new simulations of this scenario that demonstrate its ability to accurately reproduce the eccentricity, inclination and resonant structures of the Asteroid Belt. Furthermore, we perform simulations using an integration scheme which accounts for the fragmentation of colliding bodies. The final terrestrial systems formed in these simulations provide a better match to the actual planets' compact mass distribution and dynamically cold orbits. An early instability scenario is thus very successful at simultaneously replicating the dynamical state of both the inner and outer solar system.

Comets as Messengers from the Early Solar System - Emerging Insights on Delivery of Water, Nitriles, and Organics to Earth

NASA Technical Reports Server (NTRS)

Mumma, Michael J.; Charnley, Steven B.

2012-01-01

The question of exogenous delivery of water and organics to Earth and other young planets is of critical importance for understanding the origin of Earth's volatiles, and for assessing the possible existence of exo-planets similar to Earth. Viewed from a cosmic perspective, Earth is a dry planet, yet its oceans are enriched in deuterium by a large factor relative to nebular hydrogen and analogous isotopic enrichments in atmospheric nitrogen and noble gases are also seen. Why is this so? What are the implications for Mars? For icy Worlds in our Planetary System? For the existence of Earth-like exoplanets? An exogenous (vs. outgassed) origin for Earth's atmosphere is implied, and intense debate on the relative contributions of comets and asteroids continues - renewed by fresh models for dynamical transport in the protoplanetary disk, by revelations on the nature and diversity of volatile and rocky material within comets, and by the discovery of ocean-like water in a comet from the Kuiper Belt (cf., Mumma & Charnley 2011). Assessing the creation of conditions favorable to the emergence and sustenance of life depends critically on knowledge of the nature of the impacting bodies. Active comets have long been grouped according to their orbital properties, and this has proven useful for identifying the reservoir from which a given comet emerged (OC, KB) (Levison 1996). However, it is now clear that icy bodies were scattered into each reservoir from a range of nebular distances, and the comet populations in today's reservoirs thus share origins that are (in part) common. Comets from the Oort Cloud and Kuiper Disk reservoirs should have diverse composition, resulting from strong gradients in temperature and chemistry in the proto-planetary disk, coupled with dynamical models of early radial transport and mixing with later dispersion of the final cometary nuclei into the long-term storage reservoirs. The inclusion of material from the natal interstellar cloud is probable, for comets formed in the outer solar system.

Towards investigation of evolution of dynamical systems with independence of time accuracy: more classes of systems

NASA Astrophysics Data System (ADS)

Gurzadyan, V. G.; Kocharyan, A. A.

2015-07-01

The recently developed method (Paper 1) enabling one to investigate the evolution of dynamical systems with an accuracy not dependent on time is developed further. The classes of dynamical systems which can be studied by that method are much extended, now including systems that are: (1) non-Hamiltonian, conservative; (2) Hamiltonian with time-dependent perturbation; (3) non-conservative (with dissipation). These systems cover various types of N-body gravitating systems of astrophysical and cosmological interest, such as the orbital evolution of planets, minor planets, artificial satellites due to tidal, non-tidal perturbations and thermal thrust, evolving close binary stellar systems, and the dynamics of accretion disks.

The Dynamical History of Chariklo and Its Rings

NASA Astrophysics Data System (ADS)

Wood, Jeremy; Horner, Jonti; Hinse, Tobias C.; Marsden, Stephen C.

2017-06-01

Chariklo is the only small solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backward in time for 1 Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo’s rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo’s orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (>99%) of those encounters within 1 Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.

The Dynamical History of Chariklo and Its Rings

NASA Astrophysics Data System (ADS)

Wood, Jeremy R.; Horner, Jonti; Hinse, Tobias; Marsden, Stephen

2017-10-01

Chariklo is the only small Solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backwards in time for one Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo's rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo's orbit occupies a region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (> 99%) of those encounters within one Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.

The Dynamical History of Chariklo and Its Rings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, Jeremy; Horner, Jonti; Marsden, Stephen C.

Chariklo is the only small solar system body confirmed to have rings. Given the instability of its orbit, the presence of rings is surprising, and their origin remains poorly understood. In this work, we study the dynamical history of the Chariklo system by integrating almost 36,000 Chariklo clones backward in time for 1 Gyr under the influence of the Sun and the four giant planets. By recording all close encounters between the clones and planets, we investigate the likelihood that Chariklo’s rings could have survived since its capture to the Centaur population. Our results reveal that Chariklo’s orbit occupies amore » region of stable chaos, resulting in its orbit being marginally more stable than those of the other Centaurs. Despite this, we find that it was most likely captured to the Centaur population within the last 20 Myr, and that its orbital evolution has been continually punctuated by regular close encounters with the giant planets. The great majority (>99%) of those encounters within 1 Hill radius of the planet have only a small effect on the rings. We conclude that close encounters with giant planets have not had a significant effect on the ring structure. Encounters within the Roche limit of the giant planets are rare, making ring creation through tidal disruption unlikely.« less

Detection of the Magnetospheric Emissions from Extrasolar Planets

NASA Astrophysics Data System (ADS)

Lazio, J.

2014-12-01

Planetary-scale magnetic fields are a window to a planet's interior and provide shielding of the planet's atmosphere. The Earth, Mercury, Ganymede, and the giant planets of the solar system all contain internal dynamo currents that generate planetary-scale magnetic fields. These internal dynamo currents arise from differential rotation, convection, compositional dynamics, or a combination of these. If coupled to an energy source, such as the incident kinetic or magnetic energy from the solar wind, a planet's magnetic field can produce electron cyclotron masers in its magnetic polar regions. The most well known example of this process is the Jovian decametric emission, but all of the giant planets and the Earth contain similar electron cyclotron masers within their magnetospheres. Extrapolated to extrasolar planets, the remote detection of the magnetic field of an extrasolar planet would provide a means of obtaining constraints on the thermal state, composition, and dynamics of its interior as well as improved understanding of the basic planetary dynamo process. The magnetospheric emissions from solar system planets and the discovery of extrasolar planets have motivated both theoretical and observational work on magnetospheric emissions from extrasolar planets. Stimulated by these advances, the W.M. Keck Institute for Space Studies hosted a workshop entitled "Planetary Magnetic Fields: Planetary Interiors and Habitability." I summarize the current observational status of searches for magnetospheric emissions from extrasolar planets, based on observations from a number of ground-based radio telescopes, and future prospects for ground-based studies. Using the solar system planetary magnetic fields as a guide, future space-based missions will be required to study planets with magnetic field strengths lower than that of Jupiter. I summarize mission concepts identified in the KISS workshop, with a focus on the detection of planetary electron cyclotron maser emission. The authors acknowledge ideas and advice from the participants in the "Planetary Magnetic Fields: Planetary Interiors and Habitability" workshop organized by the Keck Institute for Space Studies. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA.

Fragmentation and Thermochemical Exchanges during Planetary Core Formation - an Experimental Approach

NASA Astrophysics Data System (ADS)

Le Bars, M.; Wacheul, J. B.

2015-12-01

Telluric planet formation involved the settling of large amounts of liquid iron coming from impacting planetesimals into an ambient viscous magma ocean. The initial state of planets was mostly determined by exchanges of heat and elements during this iron rain. Up to now, most models of planet formation simply assume that the metal rapidly equilibrated with the whole mantle. Other models account for simplified dynamics of the iron rain, involving the settling of single size drops at the Stokes velocity. But the fluid dynamics of iron sedimentation is much more complex, and influenced by the large viscosity ratio between the metal and the ambient fluid, as shown in studies of rising gas bubbles (e.g. Bonometti and Magnaudet 2006). We aim at developing a global understanding of the iron rain dynamics. Our study relies on a model experiment, consisting in popping a balloon of heated metal liquid at the top of a tank filled with viscous liquid. The experiments reach the relevant turbulent planetary regime, and tackle the whole range of expected viscosity ratios. High-speed videos allow determining the dynamics of drop clouds, as well as the statistics of drop sizes, shapes, and velocities. We also develop an analytical model of turbulent diffusion during settling, validated by measuring the temperature decrease of the metal blob. We finally present consequences for models of planet formation.

Better Than Earth

NASA Astrophysics Data System (ADS)

Heller, René

2015-01-01

Do we inhabit the best of all possible worlds? German mathematician Gottfried Leibniz thought so, writing in 1710 that our planet, warts and all, must be the most optimal one imaginable. Leibniz's idea was roundly scorned as unscientific wishful thinking, most notably by French author Voltaire in his magnum opus, Candide. Yet Leibniz might find sympathy from at least one group of scientists - the astronomers who have for decades treated Earth as a golden standard as they search for worlds beyond our own solar system. Because earthlings still know of just one living world - our own - it makes some sense to use Earth as a template in the search for life elsewhere, such as in the most Earth-like regions of Mars or Jupiter's watery moon Europa. Now, however, discoveries of potentially habitable planets orbiting stars other than our sun - exoplanets, that is - are challenging that geocentric approach.

Beyond the principle of plentitude: a review of terrestrial planet habitability.

PubMed

Gaidos, E; Deschenes, B; Dundon, L; Fagan, K; Menviel-Hessler, L; Moskovitz, N; Workman, M

2005-04-01

We review recent work that directly or indirectly addresses the habitability of terrestrial (rocky) planets like the Earth. Habitability has been traditionally defined in terms of an orbital semimajor axis within a range known as the habitable zone, but it is also well known that the habitability of Earth is due to many other astrophysical, geological, and geochemical factors. We focus this review on (1) recent refinements to habitable zone calculations; (2) the formation and orbital stability of terrestrial planets; (3) the tempo and mode of geologic activity (e.g., plate tectonics) on terrestrial planets; (4) the delivery of water to terrestrial planets in the habitable zone; and (5) the acquisition and loss of terrestrial planet carbon and nitrogen, elements that constitute important atmospheric gases responsible for habitable conditions on Earth's surface as well as being the building blocks of the biosphere itself. Finally, we consider recent work on evidence for the earliest habitable environments and the appearance of life itself on our planet. Such evidence provides us with an important, if nominal, calibration point for our search for other habitable worlds.

Visible and infrared investigations of planet-crossing asteroids and outer solar system objects

NASA Technical Reports Server (NTRS)

Tholen, David J.

1991-01-01

The project is supporting lightcurve photometry, colorimetry, thermal radiometry, and astrometry of selected asteroids. Targets include the planet-crossing population, particularly Earth approachers, which are believed to be the immediate source of terrestrial meteorites, future spacecraft targets, and those objects in the outer belt, primarily the Hilda and Trojan populations, that are dynamically isolated from the main asteroid belt. Goals include the determination of population statistics for the planet-crossing objects, the characterization of spacecraft targets to assist in encounter planning and subsequent interpretation of the data, a comparison of the collisional evolution of dynamically isolated Hilda and Trojan populations with the main belt, and the determination of the mechanism driving the activity of the distant object 2060 Chiron.

Tc Trends and Terrestrial Planet Formation: The Case of Zeta Reticuli

NASA Astrophysics Data System (ADS)

Adibekyan, Vardan; Delgado-Mena, Elisa; Figueira, Pedro; Sousa, Sergio; Santos, Nuno; Faria, Joao; González Hernández, Jonay; Israelian, Garik; Harutyunyan, Gohar; Suárez-Andrés, Lucia; Hakobyan, Artur

2016-11-01

During the last decade astronomers have been trying to search for chemical signatures of terrestrial planet formation in the atmospheres of the hosting stars. Several studies suggested that the chemical abundance trend with the condensation temperature, Tc, is a signature of rocky planet formation. In particular, it was suggested that the Sun shows 'peculiar' chemical abundances due to the presence of the terrestrial planets in our solar-system. However, the rocky material accretion or the trap of rocky materials in terrestrial planets is not the only explanation for the chemical 'peculiarity' of the Sun, or other Sun-like stars with planets. In this talk I madea very brief review of this topic, and presented our last results for the particular case of Zeta Reticuli binary system: A very interesting and well-known system (known in science fiction and ufology as the world of Grey Aliens, or Reticulans) where one of the components hosts an exo-Kuiper belt, and the other component is a 'single', 'lonely' star.

How Alien Can Alien Worlds Be?

NASA Astrophysics Data System (ADS)

Adibekyan, V.; Figueira, P.; Santos, N. C.

2017-10-01

In an attempt to select stars that can host planets with characteristics similar to our own, we selected seven solar-type stars known to host planets in the habitable zone and for which spectroscopic stellar parameters are available. For these stars we estimated ’empirical’ abundances of O, C, Mg and Si, which in turn we used to derive the iron and water mass fraction of the planet building blocks with the use of the model presented in Santos et al. (2015). Our results show that if rocky planets orbit these stars they might have significantly different compositions between themselves and different from that of our Earth. However, for a meaningful comparison between the compositional properties of exoplanets in the habitable zone and our own planet, a far more sophisticated analysis (e.g. Dorn et al., 2017) of a large number of systems with precise mass and radius of planets, and accurate chemical abundances of the host stars. The work presented here is merely the first humble step in this direction.

Orbital Dynamics of Exomoons During Planet–Planet Scattering

NASA Astrophysics Data System (ADS)

Hong, Yu-Cian; Lunine, Jonathan I.; Nicholson, Philip; Raymond, Sean N.

2018-04-01

Planet–planet scattering is the leading mechanism to explain the broad eccentricity distribution of observed giant exoplanets. Here we study the orbital stability of primordial giant planet moons in this scenario. We use N-body simulations including realistic oblateness and evolving spin evolution for the giant planets. We find that the vast majority (~80%–90% across all our simulations) of orbital parameter space for moons is destabilized. There is a strong radial dependence, as moons past are systematically removed. Closer-in moons on Galilean-moon-like orbits (<0.04 R Hill) have a good (~20%–40%) chance of survival. Destabilized moons may undergo a collision with the star or a planet, be ejected from the system, be captured by another planet, be ejected but still orbiting its free-floating host planet, or survive on heliocentric orbits as "planets." The survival rate of moons increases with the host planet mass but is independent of the planet's final (post-scattering) orbits. Based on our simulations, we predict the existence of an abundant galactic population of free-floating (former) moons.

ORBITAL MOTION OF HR 8799 b, c, d USING HUBBLE SPACE TELESCOPE DATA FROM 1998: CONSTRAINTS ON INCLINATION, ECCENTRICITY, AND STABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soummer, Remi; Hagan, J. Brendan; Pueyo, Laurent

2011-11-01

HR 8799 is currently the only multiple-planet system that has been detected with direct imaging, with four giant planets of masses 7-10 M{sub Jup} orbiting at large separations (15-68 AU) from this young late A star. Orbital motion provides insight into the stability and possible formation mechanisms of this planetary system. Dynamical studies can also provide constraints on the planets' masses, which help calibrate evolutionary models, yet measuring the orbital motion is a very difficult task because the long-period orbits (50-500 yr) require long time baselines and high-precision astrometry. This paper studies the three planets HR 8799b, c, and dmore » in the archival data set of HR 8799 obtained with the Hubble Space Telescope (HST) NICMOS coronagraph in 1998. The detection of all three planets is made possible by a careful optimization of the Locally Optimized Combination of Images algorithm, and we used a statistical analysis of a large number of reduced images. This work confirms previous astrometry for planet b and presents new detections and astrometry for planets c and d. These HST images provide a ten-year baseline with the discovery images from 2008, and therefore offer a unique opportunity to constrain their orbital motion now. Recent dynamical studies of this system show the existence of a few possible stable solutions involving mean motion resonances (MMRs), where the interaction between c and d plays a major role. We study the compatibility of a few of these stable scenarios (1d:1c, 1d:2c, or 1d:2c:4d) with the new astrometric data from HST. In the hypothesis of a 1d:2c:4b MMR our best orbit fit is close to the stable solution previously identified for a three-planet system and involves low eccentricity for planet d (e{sub d} = 0.10) and moderate inclination of the system (i = 28.0 deg), assuming a coplanar system, circular orbits for b and c, and exact resonance with integer period ratios. Under these assumptions, we can place strong constraints on the inclination of the system (27.3-31.4 deg) and on the eccentricity for d e{sub d} < 0.46. Our results are robust to small departures from exact integer period ratios and consistent with previously published results based on dynamical studies for a three-planet system prior to the discovery of the fourth planet.« less

THE LAST STAGES OF TERRESTRIAL PLANET FORMATION: DYNAMICAL FRICTION AND THE LATE VENEER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schlichting, Hilke E.; Warren, Paul H.; Yin Qingzhu, E-mail: hilke@ucla.edu

2012-06-10

The final stage of terrestrial planet formation consists of the clean-up of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the high eccentricities and inclinations of the terrestrial planets to circular and coplanar orbits after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred for the terrestrial planets and the Moon suggest that a total of about 0.01 M{sub Circled-Plus} of chondritic material was delivered as 'late veneer' by planetesimals to the terrestrial planets after the end of giant impacts. Here, we combine these two independent lines of evidencemore » for a leftover population of planetesimals and show that: (1) a residual population of small planetesimals containing 0.01 M{sub Circled-Plus} is able to damp the high eccentricities and inclinations of the terrestrial planets after giant impacts to their observed values. (2) At the same time, this planetesimal population can account for the observed relative amounts of late veneer added to the Earth, Moon, and Mars provided that the majority of the accreted late veneer was delivered by small planetesimals with radii {approx}< 10 m. These small planetesimal sizes are required to ensure efficient damping of the planetesimal's velocity dispersion by mutual collisions, which in turn ensures sufficiently low relative velocities between the terrestrial planets and the planetesimals such that the planets' accretion cross sections are significantly enhanced by gravitational focusing above their geometric values. Specifically, we find that, in the limit that the relative velocity between the terrestrial planets and the planetesimals is significantly less than the terrestrial planets' escape velocities, gravitational focusing yields a mass accretion ratio of Earth/Mars {approx}({rho}{sub Circled-Plus }/{rho}{sub mars})(R{sub Circled-Plus }/R{sub mars}){sup 4} {approx} 17, which agrees well with the mass accretion ratio inferred from HSEs of 12-23. For the Earth-Moon system, we find a mass accretion ratio of {approx}200, which, as we show, is consistent with estimates of 150-700 derived from HSE abundances that include the lunar crust as well as the mantle component. We conclude that small residual planetesimals containing about {approx}1% of the mass of the Earth could provide the dynamical friction needed to relax the terrestrial planet's eccentricities and inclinations after giant impacts, and also may have been the dominant source for the late veneer added to Earth, Moon, and Mars.« less

The occurrence of Jovian planets and the habitability of planetary systems

PubMed Central

Lunine, Jonathan I.

2001-01-01

Planets of mass comparable to or larger than Jupiter's have been detected around over 50 stars, and for one such object a definitive test of its nature as a gas giant has been accomplished with data from an observed planetary transit. By virtue of their strong gravitational pull, giant planets define the dynamical and collisional environment within which terrestrial planets form. In our solar system, the position and timing of the formation of Jupiter determined the amount and source of the volatiles from which Earth's oceans and the source elements for life were derived. This paper reviews and brings together diverse observational and modeling results to infer the frequency and distribution of giant planets around solar-type stars and to assess implications for the habitability of terrestrial planets. PMID:11158551

The occurrence of Jovian planets and the habitability of planetary systems.

PubMed

Lunine, J

2001-01-30

Planets of mass comparable to or larger than Jupiter's have been detected around over 50 stars, and for one such object a definitive test of its nature as a gas giant has been accomplished with data from an observed planetary transit. By virtue of their strong gravitational pull, giant planets define the dynamical and collisional environment within which terrestrial planets form. In our solar system, the position and timing of the formation of Jupiter determined the amount and source of the volatiles from which Earth's oceans and the source elements for life were derived. This paper reviews and brings together diverse observational and modeling results to infer the frequency and distribution of giant planets around solar-type stars and to assess implications for the habitability of terrestrial planets.

Orbital stability analysis and chaotic dynamics of exoplanets in multi-stellar systems

NASA Astrophysics Data System (ADS)

Satyal, Suman

The advancement in detection technology has substantially increased the discovery rate of exoplanets in the last two decades. The confirmation of thousands of exoplanets orbiting the solar type stars has raised new astrophysical challenges, including the studies of orbital dynamics and long-term stability of such planets. Continuous orbital stability of the planet in stellar habitable zone is considered vital for life to develop. Hence, these studies furthers one self-evident aim of mankind to find an answer to the century old question: Are we alone?. This dissertation investigates the planetary orbits in single and binary star systems. Within binaries, a planet could orbit either one or both stars as S-type or P-type, respectively. I have considered S-type planets in two binaries, gamma Cephei and HD 196885, and compute their orbits by using various numerical techniques to assess their periodic, quasi-periodic or chaotic nature. The Hill stability (HS) function, which measures the orbital perturbation induced by the nearby companion, is calculated for each system and then its efficacy as a new chaos indicator is tested against Maximum Lyapunov Exponents (MLE) and Mean Exponential Growth factor of Nearby Orbits (MEGNO). The dynamics of HD 196885 AB is further explored with an emphasis on the planet's higher orbital inclination relative to the binary plane. I have quantitatively mapped out the chaotic and quasi-periodic regions of the system's phase space, which indicates a likely regime of the planet's inclination. In, addition, the resonant angle is inspected to determine whether alternation between libration and circulation occurs as a consequence of Kozai oscillations, a probable mechanism that can drive the planetary orbit to a large inclination. The studies of planetary system in GJ 832 shows potential of hosting multiple planets in close orbits. The phase space of GJ 832c (inner planet) and the Earth-mass test planet(s) are analyzed for periodic-aperiodic orbits. The stability of the system is defined in terms of its lifetime and maximum eccentricity during the integration period then a regime is established for the known and injected planet's orbital parameters. The de-stabilizing resonances due to the outer planet extend by 1.36 AU towards the star, nonetheless, existence of two Earth-mass planets seems plausible. The radial velocity (RV) curves generated for the test planets reveals a weak RV signal that cannot be measured by currently available instruments. A theory has been developed by extrapolating the radio emission processes in the Jupiter-Io system, which could reveal the presence of exomoons around the giant exoplanets. Based on this theory, maximum distance, radius and masses of exoplanets and exomoons are calculated that could be detected by the available radio telescopes. Observation time at the Low Frequency Array (LOFAR) radio telescope has been proposed to detect exomoon in five different stellar systems. Subjects of my future studies include analysis of the data from LOFAR, search for the additional transiting planets in Kepler 47 circumbinary system and observation at the Subaru telescope to verify the predicted planets in GJ 832 system by the method of direct imaging.

Forming Super-Puffs Beyond 1 AU

NASA Astrophysics Data System (ADS)

Lee, Eve J.; Chiang, Eugene

2017-06-01

Super-puffs are an uncommon class of short-period planets seemingly too voluminous for their small masses (4-10 Rearth, 2-6 Mearth). Super-puffs most easily acquire their thick atmospheres as dust-free, rapidly cooling worlds outside ˜1AU where nebular gas is colder, less dense, and therefore less opaque. These puffy planets probably migrated in to their current orbits; they are expected to form the outer links of mean-motion resonant chains, and to exhibit atmospheric characteristics consistent with formation at large distances. I will also discuss, in general, how densities of planets can be used to infer their formation locations.

Impact of planet-planet scattering on the formation and survival of debris discs

NASA Astrophysics Data System (ADS)

Marzari, F.

2014-10-01

Planet-planet scattering is a major dynamical mechanism able to significantly alter the architecture of a planetary system. In addition to that, it may also affect the formation and retention of a debris disc by the system. A violent chaotic evolution of the planets can easily clear leftover planetesimal belts preventing the ignition of a substantial collisional cascade that can give origin to a debris disc. On the other end, a mild evolution with limited steps in eccentricity and semimajor axis can trigger the formation of a debris disc by stirring an initially quiet planetesimal belt. The variety of possible effects that planet-planet scattering can have on the formation of debris discs is analysed and the statistical probability of the different outcomes is evaluated. This leads to the prediction that systems which underwent an episode of chaotic evolution might have a lower probability of harbouring a debris disc.

Dynamics of Circumbinary Planets Near the Stability Limit

NASA Astrophysics Data System (ADS)

Quarles, Billy; Satyal, Suman; Kostov, Veselin; Kaib, Nathan; Haghighipour, Nader

2018-04-01

The stability limit for circumbinary planets (CBPs) is not well defined and carries uncertainty that depends on the orbital parameters of the stellar binary and possible planets. Previous work by Holman & Wiegert (1999, AJ 117, 621) developed a two parameter fitting formula for CBPs. We update the coefficients for this formula and introduce a grid interpolation method that is based on ∼150 million full N-body simulations of systems with Jupiter-mass planets on initially circular, coplanar orbits. We find an improvement in the accuracy in estimating the inner boundary of stability and use planet packing to identify the relative proximity of the Kepler CBPs to their respective stability limits. As a result, 55% of the Kepler CBPs could host a planet at the stability limit in addition to the innermost observed planet. The results of our simulations and python tools to determine the stability limit are available to the CBP community on Zenodo and GitHub, respectively.

An extrasolar planetary system with three Neptune-mass planets.

PubMed

Lovis, Christophe; Mayor, Michel; Pepe, Francesco; Alibert, Yann; Benz, Willy; Bouchy, François; Correia, Alexandre C M; Laskar, Jacques; Mordasini, Christoph; Queloz, Didier; Santos, Nuno C; Udry, Stéphane; Bertaux, Jean-Loup; Sivan, Jean-Pierre

2006-05-18

Over the past two years, the search for low-mass extrasolar planets has led to the detection of seven so-called 'hot Neptunes' or 'super-Earths' around Sun-like stars. These planets have masses 5-20 times larger than the Earth and are mainly found on close-in orbits with periods of 2-15 days. Here we report a system of three Neptune-mass planets with periods of 8.67, 31.6 and 197 days, orbiting the nearby star HD 69830. This star was already known to show an infrared excess possibly caused by an asteroid belt within 1 au (the Sun-Earth distance). Simulations show that the system is in a dynamically stable configuration. Theoretical calculations favour a mainly rocky composition for both inner planets, while the outer planet probably has a significant gaseous envelope surrounding its rocky/icy core; the outer planet orbits within the habitable zone of this star.

The Exoplanet Migration Timescale from K2 Young Clusters

NASA Astrophysics Data System (ADS)

Rizzuto, Aaron

A significant fraction of exoplanets orbit within 0.1 AU of their host star, with periods of <20 days. The discovery of these close-in planets has defied conventional models of planet formation and evolution based on our own solar system. It is widely accepted that these close-in planets did not form in such close proximity to their host stars (both rocky planets and hot Jupiters), but rather that dynamical or interactive processes caused them to migrate inwards from larger orbital semimajor axes and periods. There are multiple planet migration scenarios proposed in the literature, though it is unclear how much of the known planet population is attributable to each mechanism. Planetary migration models can be loosely divided into two categories: disk-driven migration and dynamical migration. Disk migration occurs over the lifetime of the protoplanetary disk (<5 Myr), while migration involving dynamical multi-body interactions operates on timescales of 100 Myr to 1Gyr, a lengthier process than disk migration. The K2 mission has measured planet formation timescales and migration pathways by sampling groups of stars at key ages. Over the past 10 campaigns, multiple groups of young stars have been observed by K2, ranging from the 10 Myr Upper Scorpius OB association, through the <120 Myr Pleiades cluster, to the ,600-800 Myr Hyades and Praesepe clusters. Upcoming data from more recent campaigns include the 2Myr Taurus region and significantly more Upper Scorpius members in C13 and 15. The frequency, orbital properties, and compositions of the exoplanet population in these samples of different age, with careful treatment of detection completeness, distinguish these scenarios of exoplanet migration as their host stars are settling onto the main sequence. We have pioneered efforts to identify transiting exoplanets in the K2 data for young clusters and moving groups, and have developed a new, highly complete, detrending algorithm for rotational induced variability that is commonly seen in the light curves of young, active stars (Rizzuto et al. in prep). We have identified 11 candidate planets in Praesepe, Hyades, Upper Sco, and the Pleiades using these methods, the first of which has now been published with follow-up (Mann et al. 2016abc; Gaidos et al. 2016). This sample of detected planet candidates gives a promising first indication of the timescale over which planet migration occurs, favoring dynamical multi-body processes. However, because rotational activity in young stars makes detection of exoplanet transits more difficult for the younger clusters (e.g, Upper Sco, Pleiades), to robustly prove that these frequencies are true representations of the short-period planet occurrence rate at different PMS ages will require robust determination of detection limits in these highly variable young-star lightcurves. We propose to address the question of planet migration with a uniform injection-recovery test of young cluster members, to robustly measure the detectability of planets of differing size and orbit. This will involve detrending the light curve data of instrumental and rotational systematics, injecting a synthetic transit signature from a grid of planetary and orbital parameters, reversing the detrending, and then executing our transit search pipeline (which is tuned for highly active young stars) and mapping the recovery rate as a function of planet parameters for every individual light curve. With this map of detectability as a function of planet properties for each light curve and a full program of detected exoplanet follow-up, we can then directly confirm any change in the occurrence rates of close-in (P<20 day) planets with cluster age and identify the most significant migration mechanism.

The Most Earth Size, Habitable Zone Planets around a Single Star on This Week @NASA – 02/24/2017

NASA Image and Video Library

2017-02-24

NASA held a news conference Feb. 22 at the agency’s headquarters to discuss the finding by the agency’s Spitzer Space Telescope of seven Earth-sized planets around a tiny, relatively nearby, ultra-cool dwarf star. Three of the planets in this system, known as TRAPPIST-1, are in the habitable zone – the region around the star in which liquid water is most likely to thrive on a rocky planet. This is the first time so many planets have been found in a single star's habitable zone outside our solar system, and is the best target yet for studying the atmospheres of potentially habitable, Earth-sized worlds. Also, Kennedy’s Pad 39A, Back in Business, Russian Cargo Ship Arrives at Space Station, RS-25 Engine Tests Resume at Stennis, Structural Testing Begins on SLS Hardware, and 55th Anniversary of Friendship 7 Flight!

Planet Formation in Stellar Binaries: How Disk Gravity Can Lower theFragmentation Barrier

NASA Astrophysics Data System (ADS)

Silsbee, Kedron; Rafikov, Roman R.

2014-11-01

Binary star systems present a challenge to current theories of planet formation. Perturbations from the companion star dynamically excite the protoplanetary disk, which can lead to destructive collisions between planetesimals, and prevent growth from 1 km to 100 km sized planetesimals. Despite this apparent barrier to coagulation, planets have been discovered within several small-separation (<20 AU), eccentric (eb 0.4) binaries, such as alpha Cen and gamma Cep. We address this problem by analytically exploring planetesimal dynamics under the simultaneous action of (1) binary perturbation, (2) gas drag (which tends to align planetesimal orbits), and (3), the gravity of an eccentric protoplanetary disk. We then use our dynamical solutions to assess the outcomes of planetesimal collisions (growth, destruction, erosion) for a variety of disk models. We find that planets in small-separation binaries can form at their present locations if the primordial protoplanetary disks were massive (>0.01M⊙) and not very eccentric (eccentricity of order several per cent at the location of planet). This constraint on the disk mass is compatible with the high masses of the giant planets in known gamma Cep-like binaries, which require a large mass reservoir for their formation. We show that for these massive disks, disk gravity is dominant over the gravity of the binary companion at the location of the observed planets. Therefore, planetesimal growth is highly sensitive to disk properties. The requirement of low disk eccentricity is in line with the recent hydrodynamic simulations that tend to show gaseous disks in eccentric binaries developing very low eccentricity, at the level of a few percent. A massive purely axisymmetric disk makes for a friendlier environment for planetesimal growth by driving rapid apsidal precession of planetesimals, and averaging out the eccentricity excitation from the binary companion. When the protoplanetary disk is eccentric we find that the most favorable conditions for planetesimal growth emerge when the disk is non-precessing and is apsidally aligned with the orbit of the binary.

HabEx and the Search for Biosignatures Around Nearby Stars

NASA Astrophysics Data System (ADS)

Domagal-Goldman, Shawn David; Habitable Exoplanet Science and Technology Definition Team

2018-01-01

The Habitable Exoplanet Imaging mission (HabEx) is one of four flagship mission concepts currently under study for the upcoming 2020 Decadal Survey of Astronomy and Astrophysics. One of HabEx’s main goals will be a thorough study of planetary systems in our stellar neighborhood. This will include the characterization of any rocky planets in the habitable zones of these systems. Rocky habitable zone planets are, by definition, worlds with the potential to host global liquid water surface oceans, and therefore the potential to harbor global biospheres. HabEx’s characterization of these worlds will include a search for signs of life on these planets. These signatures will be primarily spectroscopic in nature, and result from the suite of gases emitted by biota at the planet’s surface. In this poster, we will discuss HabEx’s abilities to detect potential biosiagnature gases, and the extent to which it can discrimninate biological sources of these gases from non-biological “false positives.”

Connected Worlds: Connecting the public with complex environmental systems

NASA Astrophysics Data System (ADS)

Uzzo, S. M.; Chen, R. S.; Downs, R. R.

2016-12-01

Among the most important concepts in environmental science learning is the structure and dynamics of coupled human and natural systems (CHANS). But the fundamental epistemology for understanding CHANS requires systems thinking, interdisciplinarity, and complexity. Although the Next Generation Science Standards mandate connecting ideas across disciplines and systems, traditional approaches to education do not provide more than superficial understanding of this concept. Informal science learning institutions have a key role in bridging gaps between the reductive nature of classroom learning and contemporary data-driven science. The New York Hall of Science, in partnership with Design I/O and Columbia University's Center for International Earth Science Information Network, has developed an approach to immerse visitors in complex human nature interactions and provide opportunities for those of all ages to elicit and notice environmental consequences of their actions. Connected Worlds is a nearly 1,000 m2 immersive, playful environment in which students learn about complexity and interconnectedness in ecosystems and how ecosystems might respond to human intervention. It engages students through direct interactions with fanciful flora and fauna within and among six biomes: desert, rainforest, grassland, mountain valley, reservoir, and wetlands, which are interconnected through stocks and flows of water. Through gestures and the manipulation of a dynamic water system, Connected Worlds enables students, teachers, and parents to experience how the ecosystems of planet Earth are connected and to observe relationships between the behavior of Earth's inhabitants and our shared world. It is also a cyberlearning platform to study how visitors notice and scaffold their understanding of complex environmental processes and the responses of these processes to human intervention, to help inform the improvement of education practices in complex environmental science.

On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

NASA Astrophysics Data System (ADS)

Fleming, David P.; Barnes, Rory; Graham, David E.; Luger, Rodrigo; Quinn, Thomas R.

2018-05-01

We outline a mechanism that explains the observed lack of circumbinary planets (CBPs) via coupled stellar–tidal evolution of isolated binary stars. Tidal forces between low-mass, short-period binary stars on the pre-main sequence slow the stellar rotations transferring rotational angular momentum to the orbit as the stars approach the tidally locked state. This transfer increases the binary orbital period, expanding the region of dynamical instability around the binary, and destabilizing CBPs that tend to preferentially orbit just beyond the initial dynamical stability limit. After the stars tidally lock, we find that angular momentum loss due to magnetic braking can significantly shrink the binary orbit, and hence the region of dynamical stability, over time, impacting where surviving CBPs are observed relative to the boundary. We perform simulations over a wide range of parameter space and find that the expansion of the instability region occurs for most plausible initial conditions and that, in some cases, the stability semimajor axis doubles from its initial value. We examine the dynamical and observable consequences of a CBP falling within the dynamical instability limit by running N-body simulations of circumbinary planetary systems and find that, typically, at least one planet is ejected from the system. We apply our theory to the shortest-period Kepler binary that possesses a CBP, Kepler-47, and find that its existence is consistent with our model. Under conservative assumptions, we find that coupled stellar–tidal evolution of pre-main sequence binary stars removes at least one close-in CBP in 87% of multi-planet circumbinary systems.

World Wind 3D Earth Viewing

NASA Technical Reports Server (NTRS)

Hogan, Patrick; Maxwell, Christopher; Kim, Randolph; Gaskins, Tom

2007-01-01

World Wind allows users to zoom from satellite altitude down to any place on Earth, leveraging high-resolution LandSat imagery and SRTM (Shuttle Radar Topography Mission) elevation data to experience Earth in visually rich 3D. In addition to Earth, World Wind can also visualize other planets, and there are already comprehensive data sets for Mars and the Earth's moon, which are as easily accessible as those of Earth. There have been more than 20 million downloads to date, and the software is being used heavily by the Department of Defense due to the code s ability to be extended and the evolution of the code courtesy of NASA and the user community. Primary features include the dynamic access to public domain imagery and its ease of use. All one needs to control World Wind is a two-button mouse. Additional guides and features can be accessed through a simplified menu. A JAVA version will be available soon. Navigation is automated with single clicks of a mouse, or by typing in any location to automatically zoom in to see it. The World Wind install package contains the necessary requirements such as the .NET runtime and managed DirectX library. World Wind can display combinations of data from a variety of sources, including Blue Marble, LandSat 7, SRTM, NASA Scientific Visualization Studio, GLOBE, and much more. A thorough list of features, the user manual, a key chart, and screen shots are available at http://worldwind.arc.nasa.gov.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodigas, Timothy J.; Hinz, Philip M.; Malhotra, Renu, E-mail: rodigas@as.arizona.edu

Planets can affect debris disk structure by creating gaps, sharp edges, warps, and other potentially observable signatures. However, there is currently no simple way for observers to deduce a disk-shepherding planet's properties from the observed features of the disk. Here we present a single equation that relates a shepherding planet's maximum mass to the debris ring's observed width in scattered light, along with a procedure to estimate the planet's eccentricity and minimum semimajor axis. We accomplish this by performing dynamical N-body simulations of model systems containing a star, a single planet, and an exterior disk of parent bodies and dustmore » grains to determine the resulting debris disk properties over a wide range of input parameters. We find that the relationship between planet mass and debris disk width is linear, with increasing planet mass producing broader debris rings. We apply our methods to five imaged debris rings to constrain the putative planet masses and orbits in each system. Observers can use our empirically derived equation as a guide for future direct imaging searches for planets in debris disk systems. In the fortuitous case of an imaged planet orbiting interior to an imaged disk, the planet's maximum mass can be estimated independent of atmospheric models.« less

Scientific Value of a Saturn Atmospheric Probe Mission

NASA Technical Reports Server (NTRS)

Simon-Miller, A. A.; Lunine, J. I.; Atreya, S. K.; Spilker, T. R.; Coustenis, A.; Atkinson, D. H.

2012-01-01

Atmospheric entry probe mISSions to the giant planets can uniquely discriminate between competing theories of solar system formation and the origin and evolution of the giant planets and their atmospheres. This provides for important comparative studies of the gas and ice giants, and to provide a laboratory for studying the atmospheric chemistries, dynamics, and interiors of all the planets including Earth. The giant planets also represent a valuable link to extrasolar planetary systems. As outlined in the recent Planetary Decadal Survey, a Saturn Probe mission - with a shallow probe - ranks as a high priority for a New Frontiers class mission [1].

The Anglo-Australian Planet Search. XXV. A Candidate Massive Saturn Analog Orbiting HD 30177

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Horner, Jonathan; Mengel, M. W.; Butler, R. P.; Wright, D. J.; Tinney, C. G.; Carter, B. D.; Jones, H. R. A.; Anglada-Escudé, G.; Bailey, J.; O'Toole, Simon J.

2017-04-01

We report the discovery of a second long-period giant planet orbiting HD 30177, a star previously known to host a massive Jupiter analog (HD 30177b: a = 3.8 ± 0.1 au, m sin I = 9.7 ± 0.5 M Jup). HD 30177c can be regarded as a massive Saturn analog in this system, with a = 9.9 ± 1.0 au and m sin I = 7.6 ± 3.1 M Jup. The formal best-fit solution slightly favors a closer-in planet at a ˜ 7 au, but detailed n-body dynamical simulations show that configuration to be unstable. A shallow local minimum of longer period, lower eccentricity solutions was found to be dynamically stable, and hence we adopt the longer period in this work. The proposed ˜32 year orbit remains incomplete; further monitoring of this and other stars is necessary to reveal the population of distant gas giant planets with orbital separations a ˜ 10 au, analogous to that of Saturn.

SOLAR SYSTEM MOONS AS ANALOGS FOR COMPACT EXOPLANETARY SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kane, Stephen R.; Hinkel, Natalie R.; Raymond, Sean N., E-mail: skane@ipac.caltech.edu

2013-11-01

The field of exoplanetary science has experienced a recent surge of new systems that is largely due to the precision photometry provided by the Kepler mission. The latest discoveries have included compact planetary systems in which the orbits of the planets all lie relatively close to the host star, which presents interesting challenges in terms of formation and dynamical evolution. The compact exoplanetary systems are analogous to the moons orbiting the giant planets in our solar system, in terms of their relative sizes and semimajor axes. We present a study that quantifies the scaled sizes and separations of the solarmore » system moons with respect to their hosts. We perform a similar study for a large sample of confirmed Kepler planets in multi-planet systems. We show that a comparison between the two samples leads to a similar correlation between their scaled sizes and separation distributions. The different gradients of the correlations may be indicative of differences in the formation and/or long-term dynamics of moon and planetary systems.« less

Before Biology: Geologic Habitability and Setting the Chemical and Physical Foundations for Life

NASA Astrophysics Data System (ADS)

Unterborn, Cayman Thomas

The Earth is a habitable, dynamic planet, with plate tectonics creating a deep water and carbon cycle. These cycles regulate surface and atmospheric C and water abundances, and therefore long-term climate, which is vital to Earths habitability. The driving force behind plate tectonics is the convection of the mantle. The fact that the Earth transports its interior heat via convection instead of conduction is a result of a confluence of factors that include the internal energy budget as well as mantle size and composition. Relative to the Sun stars that host extrasolar planets vary in their refractory rock-building element proportions relative to Si by an order of magnitude. This variation will create terrestrial planets with unique mineralogies and dynamical behavior. How similar these planets are to Earth, chemically and physically, is the focus of this proposal with the end goal being to answer: "What variation in planetary chemical composition is capable of supporting the geochemical cycles necessary for life?".

Orbits and Interiors of Planets

NASA Astrophysics Data System (ADS)

Batygin, Konstantin

2012-05-01

The focus of this thesis is a collection of problems of timely interest in orbital dynamics and interior structure of planetary bodies. The first three chapters are dedicated to understanding the interior structure of close-in, gaseous extrasolar planets (hot Jupiters). In order to resolve a long-standing problem of anomalously large hot Jupiter radii, we proposed a novel magnetohydrodynamic mechanism responsible for inflation. The mechanism relies on the electro-magnetic interactions between fast atmospheric flows and the planetary magnetic field in a thermally ionized atmosphere, to induce electrical currents that flow throughout the planet. The resulting Ohmic dissipation acts to maintain the interior entropies, and by extension the radii of hot Jupiters at an enhanced level. Using self-consistent calculations of thermal evolution of hot Jupiters under Ohmic dissipation, we demonstrated a clear tendency towards inflated radii for effective temperatures that give rise to significant ionization of K and Na in the atmosphere, a trend fully consistent with the observational data. Furthermore, we found that in absence of massive cores, low-mass hot Jupiters can over-flow their Roche-lobes and evaporate on Gyr time-scales, possibly leaving behind small rocky cores. Chapters four through six focus on the improvement and implications of a model for orbital evolution of the solar system, driven by dynamical instability (termed the "Nice" model). Hydrodynamical studies of the orbital evolution of planets embedded in protoplanetary disks suggest that giant planets have a tendency to assemble into multi-resonant configurations. Following this argument, we used analytical methods as well as self-consistent numerical N-body simulations to identify fully-resonant primordial states of the outer solar system, whose dynamical evolutions give rise to orbital architectures that resemble the current solar system. We found a total of only eight such initial conditions, providing independent constraints for the solar system's birth environment. Next, we addressed a significant drawback of the original Nice model, namely its inability to create the physically unique, cold classical population of the Kuiper Belt. Specifically, we showed that a locally-formed cold belt can survive the transient instability, and its relatively calm dynamical structure can be reproduced. The last four chapters of this thesis address various aspects and consequences of dynamical relaxation of planetary orbits through dissipative effects as well as the formation of planets in binary stellar systems. Using octopole-order secular perturbation theory, we demonstrated that in multi-planet systems, tidal dissipation often drives orbits onto dynamical "fixed points," characterized by apsidal alignment and lack of periodic variations in eccentricities. We applied this formalism towards investigating the possibility that the large orbital eccentricity of the transiting Neptune-mass planet Gliese 436b is maintained in the face of tidal dissipation by a second planet in the system and computed a locus of possible orbits for the putative perturber. Following up along similar lines, we used various permutations of secular theory to show that when applied specifically to close-in low-mass planetary systems, various terms in the perturbation equations become separable, and the true masses of the planets can be solved for algebraically. In practice, this means that precise knowledge of the system's orbital state can resolve the sin( i) degeneracy inherent to non-transiting planets. Subsequently, we investigated the onset of chaotic motion in dissipative planetary systems. We worked in the context of classical secular perturbation theory, and showed that planetary systems approach chaos via the so-called period-doubling route. Furthermore, we demonstrated that chaotic strange attractors can exist in mildly damped systems, such as photo-evaporating nebulae that host multiple planets. Finally, we considered planetary formation in highly inclined binary systems, where orbital excitation due to the Kozai resonance apparently implies destructive collisions among planetesimals. Through a proper account of gravitational interactions within the protoplanetary disk, we showed that fast apsidal recession induced by disk self-gravity tends to erase the Kozai effect, and ensure that the disk's unwarped, rigid structure is maintained, resolving the difficulty in planet-formation. (Abstract shortened by UMI.)

Migration & Extra-solar Terrestrial Planets: Watering the Planets

NASA Astrophysics Data System (ADS)

Carter-Bond, Jade C.; O'Brien, David P.; Raymond, Sean N.

2014-04-01

A diverse range of terrestrial planet compositions is believed to exist within known extrasolar planetary systems, ranging from those that are relatively Earth-like to those that are highly unusual, dominated by species such as refractory elements (Al and Ca) or C (as pure C, TiC and SiC)(Bond et al. 2010b). However, all prior simulations have ignored the impact that giant planet migration during planetary accretion may have on the final terrestrial planetary composition. Here, we combined chemical equilibrium models of the disk around five known planetary host stars (Solar, HD4203, HD19994, HD213240 and Gl777) with dynamical models of terrestrial planet formation incorporating various degrees of giant planet migration. Giant planet migration is found to drastically impact terrestrial planet composition by 1) increasing the amount of Mg-silicate species present in the final body; and 2) dramatically increasing the efficiency and amount of water delivered to the terrestrial bodies during their formation process.

DETECTION AND CHARACTERIZATION OF EXTRASOLAR PLANETS THROUGH MEAN-MOTION RESONANCES. I. SIMULATIONS OF HYPOTHETICAL DEBRIS DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tabeshian, Maryam; Wiegert, Paul A., E-mail: mtabeshi@uwo.ca

2016-02-20

The gravitational influence of a planet on a nearby disk provides a powerful tool for detecting and studying extrasolar planetary systems. Here we demonstrate that gaps can be opened in dynamically cold debris disks at the mean-motion resonances of an orbiting planet. The gaps are opened away from the orbit of the planet itself, revealing that not all disk gaps need contain a planetary body. These gaps are large and deep enough to be detectable in resolved disk images for a wide range of reasonable disk-planet parameters, though we are not aware of any such gaps detected to date. Themore » gap shape and size are diagnostic of the planet location, eccentricity and mass, and allow one to infer the existence of unseen planets, as well as many important parameters of both seen and unseen planets in these systems. We present expressions to allow the planetary mass and semimajor axis to be calculated from observed gap width and location.« less

Jupiter's Water Worlds

NASA Technical Reports Server (NTRS)

Pappalardo, R. T.

2004-01-01

When the twin Voyager spacecraft cruised past Jupiter in 1979, they did more than rewrite the textbooks on the giant planet. Their cameras also unveiled the astounding diversity of the four planet-size moons of ice and stone known as the Galilean satellites. The Voyagers revealed the cratered countenance of Callisto, the valleys and ridges of Ganymede, the cracked face of Europa, and the spewing volcanoes of Io. But it would take a spacecraft named for Italian scientist Galileo, who discovered the moons in 1610, to reveal the true complexity of these worlds and to begin to divulge their interior secrets. Incredibly, the Galileo data strongly suggest that Jupiter's three large icy moons (all but rocky Io) hide interior oceans.

Trio of Neptunes and their Belt

NASA Astrophysics Data System (ADS)

2006-05-01

Using the ultra-precise HARPS spectrograph on ESO's 3.6-m telescope at La Silla (Chile), a team of European astronomers have discovered that a nearby star is host to three Neptune-mass planets. The innermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in the habitable zone. This unique system is likely further enriched by an asteroid belt. ESO PR Photo 18a/06 ESO PR Photo 18a/06 Planetary System Around HD 69830 (Artist's Impression) "For the first time, we have discovered a planetary system composed of several Neptune-mass planets", said Christophe Lovis, from the Geneva Observatory and lead-author of the paper presenting the results [1]. During more than two years, the astronomers carefully studied HD 69830, a rather inconspicuous nearby star slightly less massive than the Sun. Located 41 light-years away towards the constellation of Puppis (the Stern), it is, with a visual magnitude of 5.95, just visible with the unaided eye. The astronomers' precise radial-velocity measurements [2] allowed them to discover the presence of three tiny companions orbiting their parent star in 8.67, 31.6 and 197 days. "Only ESO's HARPS instrument installed at the La Silla Observatory, Chile, made it possible to uncover these planets", said Michel Mayor, also from Geneva Observatory, and HARPS Principal Investigator. "Without any doubt, it is presently the world's most precise planet-hunting machine" [3]. ESO PR Photo 18d/06 ESO PR Photo 18d/06 Phase Folded Measurements of HD 69830 The detected velocity variations are between 2 and 3 metres per second, corresponding to about 9 km/h! That's the speed of a person walking briskly. Such tiny signals could not have been distinguished from 'simple noise' by most of today's available spectrographs. The newly found planets have minimum masses between 10 and 18 times the mass of the Earth. Extensive theoretical simulations favour an essentially rocky composition for the inner planet, and a rocky/gas structure for the middle one. The outer planet has probably accreted some ice during its formation, and is likely to be made of a rocky/icy core surrounded by a quite massive envelope. Further calculations have also shown that the system is in a dynamically stable configuration. ESO PR Photo 18e/06 ESO PR Photo 18e/06 Formation Process of the Planetary System The outer planet also appears to be located near the inner edge of the habitable zone, where liquid water can exist at the surface of rocky/icy bodies. Although this planet is probably not Earth-like due to its heavy mass, its discovery opens the way to exciting perspectives. "This alone makes this system already exceptional", said Willy Benz, from Bern University, and co-author. "But the recent discovery by the Spitzer Space Telescope that the star most likely hosts an asteroid belt is adding the cherry to the cake." With three roughly equal-mass planets, one being in the habitable zone, and an asteroid belt, this planetary system shares many properties with our own solar system. "The planetary system around HD 69830 clearly represents a Rosetta stone in our understanding of how planets form", said Michel Mayor. "No doubt it will help us better understand the huge diversity we have observed since the first extra-solar planet was found 11 years ago." High resolution images and their captions are available on this page. Video footage and animations are also available on this page.

From Disks to Planets: The Making of Planets and Their Early Atmospheres. An Introduction

NASA Astrophysics Data System (ADS)

Lammer, Helmut; Blanc, Michel

2018-03-01

This paper is an introduction to volume 56 of the Space Science Series of ISSI, "From disks to planets—the making of planets and their proto-atmospheres", a key subject in our quest for the origins and evolutionary paths of planets, and for the causes of their diversity. Indeed, as exoplanet discoveries progressively accumulated and their characterization made spectacular progress, it became evident that the diversity of observed exoplanets can in no way be reduced to the two classes of planets that we are used to identify in the solar system, namely terrestrial planets and gas or ice giants: the exoplanet reality is just much broader. This fact is no doubt the result of the exceptional diversity of the evolutionary paths linking planetary systems as a whole as well as individual exoplanets and their proto-atmospheres to their parent circumstellar disks: this diversity and its causes are exactly what this paper explores. For each of the main phases of the formation and evolution of planetary systems and of individual planets, we summarize what we believe we understand and what are the important open questions needing further in-depth examination, and offer some suggestions on ways towards solutions. We start with the formation mechanisms of circumstellar disks, with their gas and disk components in which chemical composition plays a very important role in planet formation. We summarize how dust accretion within the disk generates planet cores, while gas accretion on these cores can lead to the diversity of their fluid envelopes. The temporal evolution of the parent disk itself, and its final dissipation, put strong constraints on how and how far planetary formation can proceed. The radiation output of the central star also plays an important role in this whole story. This early phase of planet evolution, from disk formation to dissipation, is characterized by a co-evolution of the disk and its daughter planets. During this co-evolution, planets and their protoatmospheres not only grow, but they also migrate radially as a result of their interaction with the disk, thus moving progressively from their distance of formation to their final location. The formation of planetary fluid envelopes (proto-atmospheres and oceans), is an essential product of this planet formation scenario which strongly constrains their possible evolution towards habitability. We discuss the effects of the initial conditions in the disk, of the location, size and mass of the planetary core, of the disk lifetime and of the radiation output and activity of the central star, on the formation of these envelopes and on their relative extensions with respect to the planet core. Overall, a fraction of the planets retain the primary proto-atmosphere they initially accreted from the gas disk. For those which lose it in this early evolution, outgassing of volatiles from the planetary core and mantle, together with some contributions of volatiles from colliding bodies, give them a chance to form a "secondary" atmosphere, like that of our own Earth. When the disk finally dissipates, usually before 10 Million years of age, it leaves us with the combination of a planetary system and a debris disk, each with a specific radial distribution with respect to their parent star(s). Whereas the dynamics of protoplanetary disks is dominated by gas-solid dynamical coupling, debris disks are dominated by gravitational dynamics acting on diverse families of planetesimals. Solid-body collisions between them and giant impacts on young planetary surfaces generate a new population of gas and dust in those disks. Synergies between solar system and exoplanet studies are particularly fruitful and need to be stimulated even more, because they give access to different and complementary components of debris disks: whereas the different families of planetesimals can be extensively studied in the solar system, they remain unobserved in exoplanet systems. But, in those systems, long-wavelength telescopic observations of dust provide a wealth of indirect information about the unobserved population of planetesimals. Promising progress is being currently made to observe the gas component as well, using millimetre and sub-millimetre giant radio interferometers. Within planetary systems themselves, individual planets are the assembly of a solid body and a fluid envelope, including their planetary atmosphere when there is one. Their characteristics range from terrestrial planets through sub-Neptunes and Neptunes and to gas giants, each type covering most of the orbital distances probed by present-day techniques. With the continuous progress in detection and characterization techniques and the advent of major providers of new data like the Kepler mission, the architecture of these planetary systems can be studied more and more accurately in a statistically meaningful sense and compared to the one of our own solar system, which does not appear to be an exceptional case. Finally, our understanding of exoplanets atmospheres has made spectacular advances recently using the occultation spectroscopy techniques implemented on the currently operating space and ground-based observing facilities. The powerful new observing facilities planned for the near and more distant future will make it possible to address many of the most challenging current questions of the science of exoplanets and their systems. There is little doubt that, using this new generation of facilities, we will be able to reconstruct more and more accurately the complex evolutionary paths which link stellar genesis to the possible emergence of habitable worlds.

Probing LSST's Ability to Detect Planets Around White Dwarfs

NASA Astrophysics Data System (ADS)

Cortes, Jorge; Kipping, David

2018-01-01

Over the last four years more than 2,000 planets outside our solar system have been discovered, motivating us to search for and characterize potentially habitable worlds. Most planets orbit Sun-like stars, but more exotic stars can also host planets. Debris disks and disintegrating planetary bodies have been detected around white dwarf stars, the inert, Earth-sized cores of once-thriving stars like our Sun. These detections are clues that planets may exist around white dwarfs. Due to the faintness of white dwarfs and the potential rarity of planets around them, a vast survey is required to have a chance at detecting these planetary systems. The Large Synoptic Survey Telescope (LSST), scheduled to commence operations in 2023, will image the entire southern sky every few nights for 10 years, providing our first real opportunity to detect planets around white dwarfs. We characterized LSST’s ability to detect planets around white dwarfs through simulations that incorporate realistic models for LSST’s observing strategy and the white dwarf distribution within the Milky Way galaxy. This was done through the use of LSST's Operations Simulator (OpSim) and Catalog Simulator (CatSim). Our preliminary results indicate that, if all white dwarfs were to possess a planet, LSST would yield a detection for every 100 observed white dwarfs. In the future, a larger set of ongoing simulations will help us quantify the number of planets LSST could potentially find.

Thinking Globally when Teaching Locally

ERIC Educational Resources Information Center

Van Reken, Ruth E.; Rushmore, Sally

2009-01-01

Advances in science and technology, globalization of trade, international competition for markets, ethnic conflicts, and the limits of the planet's ecosystem have brought global issues and the people of the world to doorsteps and classrooms. With the increasing interaction among peoples of the world, skills in cross-cultural communication,…

CONSTRUCTION OF AN EARTH MODEL: ANALYSIS OF EXOPLANET LIGHT CURVES AND MAPPING THE NEXT EARTH WITH THE NEW WORLDS OBSERVER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oakley, P. H. H.; Cash, W.

2009-08-01

The orbital light curve of a terrestrial exoplanet will likely contain valuable information about the surface and atmospheric features of the planet, both in its overall shape and hourly variations. We have constructed an empirically based code capable of simulating observations of the Earth from any orientation, at any time of year with continuously updated cloud and snow coverage with a New Worlds Observatory. By simulating these observations over a full orbital revolution at a distance of 10 pc we determine that the detection of an obliquity or seasonal terrain change is possible at low inclinations. In agreement with othermore » studies, a 4 m New Worlds Observer can accurately determine the rotation rate of the planet at a success rate from {approx}30% to 80% with only 5 days of observations depending on the signal to noise of the observations. We also attempt simple inversions of these diurnal light curves to sketch a map of the reflecting planet's surface features. This mapping technique is only successful with highly favorable systems and in particular requires that the cloud coverage must be lower than the Earth's average. Our test case of a 2 M {sub +} planet at 7 pc distance with low exo-zodiacal light and 25% cloud coverage produced crude, but successful results. Additionally, with these highly favorable systems NWO may be able to discern the presence of liquid surface water (or other smooth surfaces) though it requires a complex detection available only at crescent phases in high inclination systems.« less

The Dynamics of Planet Formation

NASA Astrophysics Data System (ADS)

Chambers, J. E.

2005-05-01

The transformation of a protoplanetary disk of gas and dust into a system of planets is a mysterious business that is frustratingly difficult to observe in detail. For this reason, studies of planet formation are largely based on theoretical models with only a few anchor points where precious observations are available. In this talk I will give an overview of some of these theoretical models, indicating areas of uncertainty and places where the models are on firmer ground. For convenience, theorists usually divide planet formation into a series of stages: formation of solid bodies from dust, aggregation of solid bodies into protoplanets, late-stage growth and the formation of giant planets, and planetary migration. Here I will concentrate mostly on the second and third of these stages (understanding of the first and last stages is rather limited, and the author's understanding is especially so). The intermediate stages involve interplay between several physical processes: physical collisions, gravitational scattering, dynamical friction, gas drag, and the capture and collapse of atmospheres. I will describe these processes in some detail, and show using analytical models how these effects can lead to a variety of planetary outcomes. This work was supported by NASA's Planetary Geology and Geophysics and TPF Foundation Science Mission programmes.

The California-Kepler Survey. V. Peas in a Pod: Planets in a Kepler Multi-planet System Are Similar in Size and Regularly Spaced

NASA Astrophysics Data System (ADS)

Weiss, Lauren M.; Marcy, Geoffrey W.; Petigura, Erik A.; Fulton, Benjamin J.; Howard, Andrew W.; Winn, Joshua N.; Isaacson, Howard T.; Morton, Timothy D.; Hirsch, Lea A.; Sinukoff, Evan J.; Cumming, Andrew; Hebb, Leslie; Cargile, Phillip A.

2018-01-01

We have established precise planet radii, semimajor axes, incident stellar fluxes, and stellar masses for 909 planets in 355 multi-planet systems discovered by Kepler. In this sample, we find that planets within a single multi-planet system have correlated sizes: each planet is more likely to be the size of its neighbor than a size drawn at random from the distribution of observed planet sizes. In systems with three or more planets, the planets tend to have a regular spacing: the orbital period ratios of adjacent pairs of planets are correlated. Furthermore, the orbital period ratios are smaller in systems with smaller planets, suggesting that the patterns in planet sizes and spacing are linked through formation and/or subsequent orbital dynamics. Yet, we find that essentially no planets have orbital period ratios smaller than 1.2, regardless of planet size. Using empirical mass–radius relationships, we estimate the mutual Hill separations of planet pairs. We find that 93% of the planet pairs are at least 10 mutual Hill radii apart, and that a spacing of ∼20 mutual Hill radii is most common. We also find that when comparing planet sizes, the outer planet is larger in 65% ± 0.4% of cases, and the typical ratio of the outer to inner planet size is positively correlated with the temperature difference between the planets. This could be the result of photo-evaporation. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by the University of California, and California Institute of Technology, and the University of Hawaii.

Astronomers Image Lowest-mass Exoplanet Around a Sun-like Star

NASA Image and Video Library

2017-12-08

Caption: Glowing a dark magenta, the newly discovered exoplanet GJ 504b weighs in with about four times Jupiter's mass, making it the lowest-mass planet ever directly imaged around a star like the sun. Credit: NASA/Goddard/S. Wiessinger Using infrared data from the Subaru Telescope in Hawaii, an international team of astronomers has imaged a giant planet around the bright star GJ 504. Several times the mass of Jupiter and similar in size, the new world, dubbed GJ 504b, is the lowest-mass planet ever detected around a star like the sun using direct imaging techniques. "If we could travel to this giant planet, we would see a world still glowing from the heat of its formation with a color reminiscent of a dark cherry blossom, a dull magenta," said Michael McElwain, a member of the discovery team at NASA's Goddard Space Flight Center in Greenbelt, Md. "Our near-infrared camera reveals that its color is much more blue than other imaged planets, which may indicate that its atmosphere has fewer clouds." Read more: 1.usa.gov/15Ba6fI NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

HAT-P-26b: A Neptune-mass Exoplanet with Primordial Solar Heavy Element Abundance

NASA Astrophysics Data System (ADS)

Wakeford, Hannah R.; Sing, David K.; Kataria, Tiffany; Deming, Drake; Nikolov, Nikolay; Lopez, Eric; Tremblin, Pascal; Skalid Amundsen, David; Lewis, Nikole K.; Mandell, Avi; Fortney, Jonathan J.; Knutson, Heather; Benneke, Björn; Evans, Tom M.

2017-01-01

A trend in giant planet mass and atmospheric heavy elemental abundance was first noted last century from observations of planets in our own solar system. These four data points from Jupiter, Saturn, Uranus, and Neptune have served as a corner stone of planet formation theory. Here we add another point in the mass-metallicity trend from a detailed observational study of the extrasolar planet HAT-P-26b, which inhabits the critical mass regime near Neptune and Uranus. Neptune-sized worlds are among the most common planets in our galaxy and frequently exist in orbital periods very different from that of our own solar system ice giants. Atmospheric studies are the principal window into these worlds, and thereby into their formation and evolution, beyond those of our own solar system. Using the Hubble Space Telescope and Spitzer, from the optical to the infrared, we conducted a detailed atmospheric study of the Neptune-mass exoplanet HAT-P-26b over 0.5 to 4.5 μm. We detect prominent H2O absorption at 1.4 μm to 525 ppm in the atmospheric transmission spectrum. We determine that HAT-P-26b’s atmosphere is not rich in heavy elements (≈1.8×solar), which goes distinctly against the solar system mass-metallicity trend. This likely indicates that HAT-P-26b’s atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime with little contamination from metal-rich planetesimals.

HAT-P-26b: A Neptune-mass Exoplanet with Primordial Solar Heavy Element Abundance

NASA Astrophysics Data System (ADS)

Wakeford, Hannah; Sing, David; Deming, Drake; Kataria, Tiffany; Lopez, Eric

2016-10-01

A trend in giant planet mass and atmospheric heavy elemental abundance was first noted last century from observations of planets in our own solar system. These four data points from Jupiter, Saturn, Uranus, and Neptune have served as a corner stone of planet formation theory. Here we add another point in the mass-metallicity trend from a detailed observational study of the extrasolar planet HAT-P-26b, which inhabits the critical mass regime near Neptune and Uranus. Neptune-sized worlds are among the most common planets in our galaxy and frequently exist in orbital periods very different from that of our own solar system ice giants. Atmospheric studies are the principal window into these worlds, and thereby into their formation and evolution, beyond those of our own solar system. Using the Hubble Space Telescope and Spitzer, from the optical to the infrared, we conducted a detailed atmospheric study of the Neptune-mass exoplanet HAT-P-26b over 0.5 to 4.5 μm. We detect prominent H2O absorption at 1.4 μm to 525 ppm in the atmospheric transmission spectrum. We determine that HAT-P-26b's atmosphere is not rich in heavy elements (≈1.8×solar), which goes distinctly against the solar system mass-metallicity trend. This likely indicates that HAT-P-26b's atmosphere is primordial and obtained its gaseous envelope late in its disk lifetime with little contamination from metal-rich planetesimals.

Effect of the rotation and tidal dissipation history of stars on the evolution of close-in planets

NASA Astrophysics Data System (ADS)

Bolmont, Emeline; Mathis, Stéphane

2016-11-01

Since 20 years, a large population of close-in planets orbiting various classes of low-mass stars (from M-type to A-type stars) has been discovered. In such systems, the dissipation of the kinetic energy of tidal flows in the host star may modify its rotational evolution and shape the orbital architecture of the surrounding planetary system. In this context, recent observational and theoretical works demonstrated that the amplitude of this dissipation can vary over several orders of magnitude as a function of stellar mass, age and rotation. In addition, stellar spin-up occurring during the Pre-Main-Sequence (PMS) phase because of the contraction of stars and their spin-down because of the torque applied by magnetized stellar winds strongly impact angular momentum exchanges within star-planet systems. Therefore, it is now necessary to take into account the structural and rotational evolution of stars when studying the orbital evolution of close-in planets. At the same time, the presence of planets may modify the rotational dynamics of the host stars and as a consequence their evolution, magnetic activity and mixing. In this work, we present the first study of the dynamics of close-in planets of various masses orbiting low-mass stars (from 0.6~M_⊙ to 1.2~M_⊙) where we compute the simultaneous evolution of the star's structure, rotation and tidal dissipation in its external convective envelope. We demonstrate that tidal friction due to the stellar dynamical tide, i.e. tidal inertial waves excited in the convection zone, can be larger by several orders of magnitude than the one of the equilibrium tide currently used in Celestial Mechanics, especially during the PMS phase. Moreover, because of this stronger tidal friction in the star, the orbital migration of the planet is now more pronounced and depends more on the stellar mass, rotation and age. This would very weakly affect the planets in the habitable zone because they are located at orbital distances such that stellar tide-induced migration happens on very long timescales. We also demonstrate that the rotational evolution of host stars is only weakly affected by the presence of planets except for massive companions.

Innocent Bystanders: Orbital Dynamics of Exomoons During Planet–Planet Scattering

NASA Astrophysics Data System (ADS)

Hong, Yu-Cian; Raymond, Sean N.; Nicholson, Philip D.; Lunine, Jonathan I.

2018-01-01

Planet–planet scattering is the leading mechanism to explain the broad eccentricity distribution of observed giant exoplanets. Here we study the orbital stability of primordial giant planet moons in this scenario. We use N-body simulations including realistic oblateness and evolving spin evolution for the giant planets. We find that the vast majority (∼80%–90% across all our simulations) of orbital parameter space for moons is destabilized. There is a strong radial dependence, as moons past ∼ 0.1 {R}{Hill} are systematically removed. Closer-in moons on Galilean-moon-like orbits (<0.04 R Hill) have a good (∼20%–40%) chance of survival. Destabilized moons may undergo a collision with the star or a planet, be ejected from the system, be captured by another planet, be ejected but still orbiting its free-floating host planet, or survive on heliocentric orbits as “planets.” The survival rate of moons increases with the host planet mass but is independent of the planet’s final (post-scattering) orbits. Based on our simulations, we predict the existence of an abundant galactic population of free-floating (former) moons.

ORBITAL DISTRIBUTIONS OF CLOSE-IN PLANETS AND DISTANT PLANETS FORMED BY SCATTERING AND DYNAMICAL TIDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagasawa, M.; Ida, S., E-mail: nagasawa.m.ad@m.titech.ac.jp

2011-12-01

We investigated the formation of close-in planets (hot Jupiters) by a combination of mutual scattering, Kozai effect, and tidal circularization, through N-body simulations of three gas giant planets, and compared the results with discovered close-in planets. We found that in about 350 cases out of 1200 runs ({approx}30%), the eccentricity of one of the planets is excited highly enough for tidal circularization by mutual close scatterings followed by secular effects due to outer planets, such as the Kozai mechanism, and the planet becomes a close-in planet through the damping of eccentricity and semimajor axis. The formation probability of close-in planetsmore » by such scattering is not affected significantly by the effect of the general relativity and inclusion of inertial modes in addition to fundamental modes in the tides. Detailed orbital distributions of the formed close-in planets and their counterpart distant planets in our simulations were compared with observational data. We focused on the possibility for close-in planets to retain non-negligible eccentricities ({approx}> 0.1) on timescales of {approx}10{sup 9} yr and have high inclinations, because close-in planets in eccentric or highly inclined orbits have recently been discovered. In our simulations we found that as many as 29% of the close-in planets have retrograde orbits, and the retrograde planets tend to have small eccentricities. On the other hand, eccentric close-in planets tend to have orbits of small inclinations.« less

ON THE LIKELIHOOD OF PLANET FORMATION IN CLOSE BINARIES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang-Condell, Hannah, E-mail: hjangcon@uwyo.edu

2015-02-01

To date, several exoplanets have been discovered orbiting stars with close binary companions (a ≲ 30 AU). The fact that planets can form in these dynamically challenging environments implies that planet formation must be a robust process. The initial protoplanetary disks in these systems from which planets must form should be tidally truncated to radii of a few AU, which indicates that the efficiency of planet formation must be high. Here, we examine the truncation of circumstellar protoplanetary disks in close binary systems, studying how the likelihood of planet formation is affected over a range of disk parameters. If themore » semimajor axis of the binary is too small or its eccentricity is too high, the disk will have too little mass for planet formation to occur. However, we find that the stars in the binary systems known to have planets should have once hosted circumstellar disks that were capable of supporting planet formation despite their truncation. We present a way to characterize the feasibility of planet formation based on binary orbital parameters such as stellar mass, companion mass, eccentricity, and semimajor axis. Using this measure, we can quantify the robustness of planet formation in close binaries and better understand the overall efficiency of planet formation in general.« less

An independent determination of Fomalhaut b's orbit and the dynamical effects on the outer dust belt

NASA Astrophysics Data System (ADS)

Beust, H.; Augereau, J.-C.; Bonsor, A.; Graham, J. R.; Kalas, P.; Lebreton, J.; Lagrange, A.-M.; Ertel, S.; Faramaz, V.; Thébault, P.

2014-01-01

Context. The nearby star Fomalhaut harbors a cold, moderately eccentric (e ~ 0.1) dust belt with a sharp inner edge near 133 au. A low-mass, common proper motion companion, Fomalhaut b (Fom b), was discovered near the inner edge and was identified as a planet candidate that could account for the belt morphology. However, the most recent orbit determination based on four epochs of astrometry over eight years reveals a highly eccentric orbit (e = 0.8 ± 0.1) that appears to cross the belt in the sky plane projection. Aims: We perform here a full orbital determination based on the available astrometric data to independently validate the orbit estimates previously presented. Adopting our values for the orbital elements and their associated uncertainties, we then study the dynamical interaction between the planet and the dust ring, to check whether the proposed disk sculpting scenario by Fom b is plausible. Methods: We used a dedicated MCMC code to derive the statistical distributions of the orbital elements of Fom b. Then we used symplectic N-body integration to investigate the dynamics of the dust belt, as perturbed by a single planet. Different attempts were made assuming different masses for Fom b. We also performed a semi-analytical study to explain our results. Results: Our results are in good agreement with others regarding the orbit of Fom b. We find that the orbit is highly eccentric, is close to apsidally aligned with the belt, and has a mutual inclination relative to the belt plane of <29° (67% confidence). If coplanar, this orbit crosses the disk. Our dynamical study then reveals that the observed planet could sculpt a transient belt configuration with a similar eccentricity to what is observed, but it would not be simultaneously apsidally aligned with the planet. This transient configuration only occurs a short time after the planet is placed on such an orbit (assuming an initially circular disk), a time that is inversely proportional to the planet's mass, and that is in any case much less than the 440 Myr age of the star. Conclusions: We constrain how long the observed dust belt could have survived with Fom b on its current orbit, as a function of its possible mass. This analysis leads us to conclude that Fom b is likely to have low mass, that it is unlikely to be responsible for the sculpting of the belt, and that it supports the hypothesis of a more massive, less eccentric planet companion Fomalhaut c.

A new era. Healing the injuries we have inflicted on our planet.

PubMed

Berry, T

1992-03-01

The health of the earth is essential for the well-being of every living creature on the planet; however, our plundering industrial economy has disrupted the earth's biosystems. Such neglect can no longer be accepted. Medicine is in the same situation as the entire range of human activities: All must find a way to exist in harmony with the natural world. We have been so caught up in our scientific capacity to alter the natural world that we have ignored its most basic structure. We must, therefore, enter a new era-the "Ecozoic" era, a period when humans would live on the earth in a mutually enhancing manner. This transition will require changes at a most profound level in human activity. Three principles form the basis for the Ecozoic era: Humans must recognize the universe as a communion of subjects, not a collection of objects. The earth is primary; humans are derivative. The planet will never again function as it has in the past. To enter the Ecozoic era, humans need sciences that create a new way of understanding the natural world as possessing its own unique spontaneities. Especially needed are biological sciences that have a "feel for the organism." This move from anthropology to "earthology" and cosmology is a comprehensive challenge to all our professions.

Orbital evolution studies of planet-crossing asteroids

NASA Astrophysics Data System (ADS)

Hahn, Gerhard; Lagerkvist, Claes-Ingvar

The orbits of 26 planet-crossing Aten-Apollo-Amor asteroids are predicted on the basis of numerical integrations covering 33,000 or 100,000 yrs; the values reported supplement the preliminary findings of Hahn and Lagerkvist (1987). A solar-system dynamics model accounting for the effects of all planets from Venus to Neptune is employed, along with the 15th-order integration algorithm RADAU (Everhart, 1985). The results are presented in extensive tables and graphs and discussed in detail.

Sesquinary Catenae on the Martian Satellite Phobos from Reaccretion of Escaping Ejecta

DTIC Science & Technology

2016-08-30

Life near the Roche limit—behavior of ejecta from satellites close to planets . Icarus 42, 422–441 (1980). 13. Soter, S. in Studies of the Terrestrial...sesquinaries are probes of the primary ejection process, but are also bound to the dynamics of the planet -satellite system. Unlike secondaries, to...intermediate between vesc and the orbital velocity vorb. When the satellite is far from the planet , sesquinaries can produce primary- like crater morphology

Pursuing the planet-debris disk connection: Analysis of upper limits from the Anglo-Australian planet search

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wittenmyer, Robert A.; Marshall, Jonathan P., E-mail: rob@phys.unsw.edu.au

2015-02-01

Solid material in protoplanetary disks will suffer one of two fates after the epoch of planet formation; either being bound up into planetary bodies, or remaining in smaller planetesimals to be ground into dust. These end states are identified through detection of sub-stellar companions by periodic radial velocity (or transit) variations of the star, and excess emission at mid- and far-infrared wavelengths, respectively. Since the material that goes into producing the observable outcomes of planet formation is the same, we might expect these components to be related both to each other and their host star. Heretofore, our knowledge of planetarymore » systems around other stars has been strongly limited by instrumental sensitivity. In this work, we combine observations at far-infrared wavelengths by IRAS, Spitzer, and Herschel with limits on planetary companions derived from non-detections in the 16 year Anglo-Australian Planet Search to clarify the architectures of these (potential) planetary systems and search for evidence of correlations between their constituent parts. We find no convincing evidence of such correlations, possibly owing to the dynamical history of the disk systems, or the greater distance of the planet-search targets. Our results place robust limits on the presence of Jupiter analogs which, in concert with the debris disk observations, provides insights on the small-body dynamics of these nearby systems.« less

Hydro-gravitational-dynamics cosmology is crucial to astrobiology and the biological big bang at two million years

NASA Astrophysics Data System (ADS)

Gibson, Carl H.

2015-09-01

Hydro-Gravitational-Dynamics (HGD) cosmology predicts that the 1012 s (30 Kyr) H-He4 plasma protogalaxies become, by viscous fragmentation, proto-globular-star-cluster PGC clumps of a trillion small planets, at the 1013 s transition to gas. Larger planets and stars result from mergers of these hot 3000 K hydrogen planets in the PGCs. Stardust oxides of life chemicals C, N, O, Fe, Si seed the planets when the stars explode as supernovae. Hydrogen reduces the metal oxides and silicates to metal and rocky planet cores with massive hot water oceans at critical water temperature 647 K in which organic chemistry and life can develop. Because information is continually exchanged between the merging planets, they form a cosmic soup. The biological big bang occurs between 2 Myr when liquid water rains hot deep oceans in the cooling cosmos, and 8 Myr when the oceans freeze6. Thus, HGD cosmology explains the Hoyle/Wickramasinghe concept of cometary panspermia by giving a vast, hot, nourishing, cosmological primordial soup for abiogenesis, and the means for transmitting the resulting life forms and their evolving RNA/DNA mechanisms widely throughout the universe. A primordial astrophysical basis is provided for astrobiology by HGD cosmology. Concordance ΛCDMHC cosmology is rendered obsolete by the observation of complex life on Earth.

Alpha Centauri's siren call has frustrated planet hunters

NASA Astrophysics Data System (ADS)

Clery, Daniel

2018-04-01

Alpha Centauri, a three-star system just 4 light-years away that is the sun's nearest neighbor, ought to be a great place to look for Earth-like planets. But last week, at a meeting of the European Astronomical Society here, astronomers lamented that the system has so far thwarted discovery efforts—and announced new schemes to probe it. The two sunlike stars, Alpha Centauri A and B, orbit each other closely while Proxima Centauri, a tempestuous red dwarf, hangs onto the system tenuously in a much more distant orbit. In 2016, astronomers discovered an Earth-mass planet around Proxima Centauri, but few think the planet, blasted by radiation and fierce stellar winds, is habitable. Astrobiologists believe the other two stars are more likely to host temperate, Earth-like worlds.

It's in Our Hands Now

ERIC Educational Resources Information Center

Ward, Jane

2010-01-01

The world's political leaders failed to agree a fair, ambitious and legally binding accord that would protect the planet from catastrophic global warming at the United Nations' Copenhagen conference on climate change. This makes grassroots action all the more essential to save the world from devastating climate change. The UK Government championed…

On the Possibility of Habitable Trojan Planets in Binary Star Systems.

PubMed

Schwarz, Richard; Funk, Barbara; Bazsó, Ákos

2015-12-01

Approximately 60% of all stars in the solar neighbourhood (up to 80% in our Milky Way) are members of binary or multiple star systems. This fact led to the speculations that many more planets may exist in binary systems than are currently known. To estimate the habitability of exoplanetary systems, we have to define the so-called habitable zone (HZ). The HZ is defined as a region around a star where a planet would receive enough radiation to maintain liquid water on its surface and to be able to build a stable atmosphere. We search for new dynamical configurations-where planets may stay in stable orbits-to increase the probability to find a planet like the Earth.

Records of Migration in the Exoplanet Configurations

NASA Astrophysics Data System (ADS)

Michtchenko, Tatiana A.; Rodriguez Colucci, A.; Tadeu Dos Santos, M.

2013-05-01

Abstract (2,250 Maximum Characters): When compared to our Solar System, many exoplanet systems exhibit quite unusual planet configurations; some of these are hot Jupiters, which orbit their central stars with periods of a few days, others are resonant systems composed of two or more planets with commensurable orbital periods. It has been suggested that these configurations can be the result of a migration processes originated by tidal interactions of the planets with disks and central stars. The process known as planet migration occurs due to dissipative forces which affect the planetary semi-major axes and cause the planets to move towards to, or away from, the central star. In this talk, we present possible signatures of planet migration in the distribution of the hot Jupiters and resonant exoplanet pairs. For this task, we develop a semi-analytical model to describe the evolution of the migrating planetary pair, based on the fundamental concepts of conservative and dissipative dynamics of the three-body problem. Our approach is based on an analysis of the energy and the orbital angular momentum exchange between the two-planet system and an external medium; thus no specific kind of dissipative forces needs to be invoked. We show that, under assumption that dissipation is weak and slow, the evolutionary routes of the migrating planets are traced by the stationary solutions of the conservative problem (Birkhoff, Dynamical systems, 1966). The ultimate convergence and the evolution of the system along one of these modes of motion are determined uniquely by the condition that the dissipation rate is sufficiently smaller than the roper frequencies of the system. We show that it is possible to reassemble the starting configurations and migration history of the systems on the basis of their final states, and consequently to constrain the parameters of the physical processes involved.

Hubble Observes the Moons and Rings of Uranus

NASA Technical Reports Server (NTRS)

1994-01-01

This NASA Hubble Space Telescope image of the planet Uranus reveals the planet's rings, at least five of the inner moons, and bright clouds in the planet's southern hemisphere. Hubble now allows astronomers to revisit the planet at a level of detail not possible since the Voyager 2 spacecraft flew by the planet briefly, nearly a decade ago.

Hubble's new view was obtained on August 14, 1994, when Uranus was 1.7 billion miles (2.8 billion kilometers) from Earth. Similar details, as imaged by the Wide Field Planetary Camera 2, were only previously seen by the Voyager 2 spacecraft that flew by Uranus in 1986 (the rings were discovered by stellar occultation experiments in 1977, but not seen directly until Voyager flew to Uranus). Since the flyby, none of these inner satellites has been observed further, and detailed observations of the rings and Uranus' atmosphere have not been possible, because the rings are lost in the planet's glare as seen through ground-based optical telescopes.

Each of the inner moons appears as a string of three dots in this picture because it is a composite of three images, taken about six minutes apart. When these images are combined, they show the motion of the moons compared with the sky background. Because the moons move much more rapidly than our own Moon, they change position noticeably over only a few minutes. (These multiple images also help to distinguish the moons from stars and imaging detector artifacts, i.e., cosmic rays and electronic noise).

Thanks to Hubble's capabilities, astronomers will now be able to determine the orbits more precisely. With this increase in accuracy, astronomers can better probe the unusual dynamics of Uranus' complicated satellite system. Measuring the moons' brightness in several colors might offer clues to the satellites' origin by providing new information on their mineralogical composition. Similar measurements of the rings should yield new insights into their composition and origin.

One of the four gas giant planets of our solar system, Uranus is largely featureless. HST does reveal a high altitude haze which appears as a bright 'cap' above the planet's south pole, along with clouds at southern latitudes (similar structures were observed by Voyager). Unlike Earth, Uranus' south pole points toward the Sun during part of the planet's 84- year orbit. Thanks to its high resolution and ability to make observations over many years, Hubble can follow seasonal changes in Uranus' atmosphere, which should be unusual given the planet's large tilt.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Astrobiology: An astronomer's perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bergin, Edwin A.

2014-12-08

In this review we explore aspects of the field of astrobiology from an astronomical viewpoint. We therefore focus on the origin of life in the context of planetary formation, with additional emphasis on tracing the most abundant volatile elements, C, H, O, and N that are used by life on Earth. We first explore the history of life on our planet and outline the current state of our knowledge regarding the delivery of the C, H, O, N elements to the Earth. We then discuss how astronomers track the gaseous and solid molecular carriers of these volatiles throughout the processmore » of star and planet formation. It is now clear that the early stages of star formation fosters the creation of water and simple organic molecules with enrichments of heavy isotopes. These molecules are found as ice coatings on the solid materials that represent microscopic beginnings of terrestrial worlds. Based on the meteoritic and cometary record, the process of planet formation, and the local environment, lead to additional increases in organic complexity. The astronomical connections towards this stage are only now being directly made. Although the exact details are uncertain, it is likely that the birth process of star and planets likely leads to terrestrial worlds being born with abundant water and organics on the surface.« less

World-leading science with SPIRou - The nIR spectropolarimeter / high-precision velocimeter for CFHT

NASA Astrophysics Data System (ADS)

Delfosse, X.; Donati, J.-F.; Kouach, D.; Hébrard, G.; Doyon, R.; Artigau, E.; Bouchy, F.; Boisse, I.; Brun, A. S.; Hennebelle, P.; Widemann, T.; Bouvier, J.; Bonfils, X.; Morin, J.; Moutou, C.; Pepe, F.; Udry, S.; do Nascimento, J.-D.; Alencar, S. H. P.; Castilho, B. V.; Martioli, E.; Wang, S. Y.; Figueira, P.; Santos, N. C.

2013-11-01

SPIRou is a near-infrared (nIR) spectropolarimeter / velocimeter proposed as a new-generation instrument for CFHT. SPIRou aims in particular at becoming world-leader on two forefront science topics, (i) the quest for habitable Earth-like planets around very- low-mass stars, and (ii) the study of low-mass star and planet formation in the presence of magnetic fields. In addition to these two main goals, SPIRou will be able to tackle many key programs, from weather patterns on brown dwarf to solar-system planet atmospheres, to dynamo processes in fully-convective bodies and planet habitability. The science programs that SPIRou proposes to tackle are forefront (identified as first priorities by most research agencies worldwide), ambitious (competitive and complementary with science programs carried out on much larger facilities, such as ALMA and JWST) and timely (ideally phased with complementary space missions like TESS and CHEOPS). SPIRou is designed to carry out its science mission with maximum efficiency and optimum precision. More specifically, SPIRou will be able to cover a very wide single-shot nIR spectral domain (0.98-2.35 μm) at a resolving power of 73.5K, providing unpolarized and polarized spectra of low-mass stars with a ˜15% average throughput and a radial velocity (RV) precision of 1 m/s.

From Extrasolar Planets to Exo-Earths

NASA Astrophysics Data System (ADS)

Fischer, Debra

2018-06-01

The ancient Greeks debated whether the Earth was unique, or innumerable worlds existed around other Suns. Twenty five years ago, technology and human ingenuity enabled the discovery of the first extrasolar planet candidates. The architectures of these first systems, with gas giant planets in star-skirting orbits, were unexpected and again raised an echo of that ancient question: is the Earth typical or unique? We are interested in this seemingly anthropocentric question because with all of our searching and discoveries, Earth is the only place where life has been found. It is the question of whether life exists elsewhere that energizes the search for exoplanets. The trajectory of this field has been stunning. After a steady stream of detections with the radial velocity method, a burst of discovery was made possible with the NASA Kepler mission. While thousands of smaller planets have now been found, true Earth analogs have eluded robust detection. However, we are sharpening the knives of our technology and without a doubt we now stand at the threshold of detecting hundreds of Earth analogs. Using Gaia, TESS, WFIRST, JWST and new ground-based spectrographs, we will learn the names and addresses of the worlds that orbit nearby stars and we will be ready to probe their atmospheres. We will finally resolve the ancient question of whether life is unique or common.

Cracking the Code of Faraway Worlds

NASA Technical Reports Server (NTRS)

2007-01-01

This infrared data from NASA's Spitzer Space Telescope - called a spectrum - tells astronomers that a distant gas planet, a so-called 'hot Jupiter' called HD 209458b, might be smothered with high clouds. It is one of the first spectra of an alien world.

A spectrum is created when an instrument called a spectrograph spreads light from an object apart into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object.

Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called 'transiting' hot-Jupiter planets using the 'secondary eclipse' technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors.

When astronomers first saw the infrared spectrum above, they were shocked. It doesn't look anything like what theorists had predicted. Theorists though the spectra for hot, Jupiter-like planets like this one would be filled with the signatures of molecules in the planets' atmospheres. But the spectrum doesn't show any molecules. It is what astronomers call 'flat.' For example, theorists thought there'd be signatures of water in the wavelength ranges of 8 to 9 microns. The fact that water is not seen there might indicate that the water is hidden under a thick blanket of high, dry clouds.

This spectrum was produced by Dr. Mark R. Swain of NASA's Jet Propulsion Laboratory in Pasadena, Calif., using a complex set of mathematical tools. It was derived using two different methods, both of which led to the same result. The data were taken on July 6 and 13, 2005, by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center and his team using Spitzer's infrared spectrograph.

HABITABLE CLIMATES: THE INFLUENCE OF ECCENTRICITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dressing, Courtney D.; Spiegel, David S.; Scharf, Caleb A.

2010-10-01

In the outer regions of the habitable zone, the risk of transitioning into a globally frozen 'snowball' state poses a threat to the habitability of planets with the capacity to host water-based life. Here, we use a one-dimensional energy balance climate model (EBM) to examine how obliquity, spin rate, orbital eccentricity, and the fraction of the surface covered by ocean might influence the onset of such a snowball state. For an exoplanet, these parameters may be strikingly different from the values observed for Earth. Since, for a constant semimajor axis, the annual mean stellar irradiation scales with (1 - emore » {sup 2}){sup -1/2}, one might expect the greatest habitable semimajor axis (for fixed atmospheric composition) to scale as (1 - e {sup 2}){sup -1/4}. We find that this standard simple ansatz provides a reasonable lower bound on the outer boundary of the habitable zone, but the influence of both obliquity and ocean fraction can be profound in the context of planets on eccentric orbits. For planets with eccentricity 0.5, for instance, our EBM suggests that the greatest habitable semimajor axis can vary by more than 0.8 AU (78%) depending on obliquity, with higher obliquity worlds generally more stable against snowball transitions. One might also expect that the long winter at an eccentric planet's apoastron would render it more susceptible to global freezing. Our models suggest that this is not a significant risk for Earth-like planets around Sun-like stars, as considered here, since such planets are buffered by the thermal inertia provided by oceans covering at least 10% of their surface. Since planets on eccentric orbits spend much of their year particularly far from the star, such worlds might turnout to be especially good targets for direct observations with missions such as TPF-Darwin. Nevertheless, the extreme temperature variations achieved on highly eccentric exo-Earths raise questions about the adaptability of life to marginally or transiently habitable conditions.« less

Remote Sensing Data Analytics for Planetary Science with PlanetServer/EarthServer

NASA Astrophysics Data System (ADS)

Rossi, Angelo Pio; Figuera, Ramiro Marco; Flahaut, Jessica; Martinot, Melissa; Misev, Dimitar; Baumann, Peter; Pham Huu, Bang; Besse, Sebastien

2016-04-01

Planetary Science datasets, beyond the change in the last two decades from physical volumes to internet-accessible archives, still face the problem of large-scale processing and analytics (e.g. Rossi et al., 2014, Gaddis and Hare, 2015). PlanetServer, the Planetary Science Data Service of the EC-funded EarthServer-2 project (#654367) tackles the planetary Big Data analytics problem with an array database approach (Baumann et al., 2014). It is developed to serve a large amount of calibrated, map-projected planetary data online, mainly through Open Geospatial Consortium (OGC) Web Coverage Processing Service (WCPS) (e.g. Rossi et al., 2014; Oosthoek et al., 2013; Cantini et al., 2014). The focus of the H2020 evolution of PlanetServer is still on complex multidimensional data, particularly hyperspectral imaging and topographic cubes and imagery. In addition to hyperspectral and topographic from Mars (Rossi et al., 2014), the use of WCPS is applied to diverse datasets on the Moon, as well as Mercury. Other Solar System Bodies are going to be progressively available. Derived parameters such as summary products and indices can be produced through WCPS queries, as well as derived imagery colour combination products, dynamically generated and accessed also through OGC Web Coverage Service (WCS). Scientific questions translated into queries can be posed to a large number of individual coverages (data products), locally, regionally or globally. The new PlanetServer system uses the the Open Source Nasa WorldWind (e.g. Hogan, 2011) virtual globe as visualisation engine, and the array database Rasdaman Community Edition as core server component. Analytical tools and client components of relevance for multiple communities and disciplines are shared across service such as the Earth Observation and Marine Data Services of EarthServer. The Planetary Science Data Service of EarthServer is accessible on http://planetserver.eu. All its code base is going to be available on GitHub, on https://github.com/planetserver References: Baumann, P., et al. (2015) Big Data Analytics for Earth Sciences: the EarthServer approach, International Journal of Digital Earth, doi: 10.1080/17538947.2014.1003106. Cantini, F. et al. (2014) Geophys. Res. Abs., Vol. 16, #EGU2014-3784. Gaddis, L., and T. Hare (2015), Status of tools and data for planetary research, Eos, 96, dos: 10.1029/2015EO041125. Hogan, P., 2011. NASA World Wind: Infrastructure for Spatial Data. Technical report. Proceedings of the 2nd International Conference on Computing for Geospatial Research & Applications ACM. Oosthoek, J.H.P, et al. (2013) Advances in Space Research. doi: 10.1016/j.asr.2013.07.002. Rossi, A. P., et al. (2014) PlanetServer/EarthServer: Big Data analytics in Planetary Science. Geophysical Research Abstracts, Vol. 16, #EGU2014-5149.

A Dynamical Perspective on Additional Planets in 55 Cancri

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Barnes, Rory; Gorelick, Noel

2008-12-01

Five planets are known to orbit the star 55 Cancri. The recently discovered planet f at 0.78 AU (Fischer et al.) is located at the inner edge of a previously identified stable zone that separates the three close-in planets from planet d at 5.9 AU. Here we map the stability of the orbital space between planets f and d using a suite of n-body integrations that include an additional, yet-to-be-discovered planet g with a radial velocity amplitude of 5 ms-1 (planet mass = 0.5-1.2 Saturn masses). We find a large stable zone extending from 0.9 to 3.8 AU at eccentricities below 0.4. For each system we quantify the probability of detecting planets b-f on their current orbits given perturbations from hypothetical planet g, in order to further constrain the mass and orbit of an additional planet. We find that large perturbations are associated with specific mean motion resonances (MMRs) with planets f and d. We show that two MMRs, 3f:1g (the 1:3 MMR between planets g and f) and 4g:1d cannot contain a planet g. The 2f:1g MMR is unlikely to contain a planet more massive than ~20 M⊕. The 3g:1d and 5g:2d MMRs could contain a resonant planet but the resonant location is strongly confined. The 3f:2g, 2g:1d, and 3g:2d MMRs exert a stabilizing influence and could contain a resonant planet. Furthermore, we show that the stable zone may in fact contain 2-3 additional planets, if they are ~50 M⊕ each. Finally, we show that any planets exterior to planet d must reside beyond 10 AU.

Grain size evolution and convection regimes of the terrestrial planets

NASA Astrophysics Data System (ADS)

Rozel, A.; Golabek, G. J.; Boutonnet, E.

2011-12-01

A new model of grain size evolution has recently been proposed in Rozel et al. 2010. This new approach stipulates that the grain size dynamics is governed by two additive and simultaneous processes: grain growth and dynamic recrystallization. We use the usual normal grain growth laws for the growth part. For dynamic recrystallization, reducing the mean grain size increases the total area of grain boundaries. Grain boundaries carry some surface tension, so some energy is required to decrease the mean grain size. We consider that this energy is available during mechanical work. It is usually considered to produce some heat via viscous dissipation. A partitioning parameter f is then required to know what amount of energy is dissipated and what part is converted in surface tension. This study gives a new calibration of the partitioning parameter on major Earth materials involved in the dynamic of the terrestrial planets. Our calibration is in adequation with the published piezometric relations available in the literature (equilibrium grain size versus shear stress). We test this new model of grain size evolution in a set of numerical computations of the dynamics of the Earth using stagYY. We show that the grain size evolution has a major effect on the convection regimes of terrestrial planets.

Debris disks as signposts of terrestrial planet formation

NASA Astrophysics Data System (ADS)

Raymond, S. N.; Armitage, P. J.; Moro-Martín, A.; Booth, M.; Wyatt, M. C.; Armstrong, J. C.; Mandell, A. M.; Selsis, F.; West, A. A.

2011-06-01

There exists strong circumstantial evidence from their eccentric orbits that most of the known extra-solar planetary systems are the survivors of violent dynamical instabilities. Here we explore the effect of giant planet instabilities on the formation and survival of terrestrial planets. We numerically simulate the evolution of planetary systems around Sun-like stars that include three components: (i) an inner disk of planetesimals and planetary embryos; (ii) three giant planets at Jupiter-Saturn distances; and (iii) an outer disk of planetesimals comparable to estimates of the primitive Kuiper belt. We calculate the dust production and spectral energy distribution of each system by assuming that each planetesimal particle represents an ensemble of smaller bodies in collisional equilibrium. Our main result is a strong correlation between the evolution of the inner and outer parts of planetary systems, i.e. between the presence of terrestrial planets and debris disks. Strong giant planet instabilities - that produce very eccentric surviving planets - destroy all rocky material in the system, including fully-formed terrestrial planets if the instabilities occur late, and also destroy the icy planetesimal population. Stable or weakly unstable systems allow terrestrial planets to accrete in their inner regions and significant dust to be produced in their outer regions, detectable at mid-infrared wavelengths as debris disks. Stars older than ~100 Myr with bright cold dust emission (in particular at λ ~ 70 μm) signpost dynamically calm environments that were conducive to efficient terrestrial accretion. Such emission is present around ~16% of billion-year old Solar-type stars. Our simulations yield numerous secondary results: 1) the typical eccentricities of as-yet undetected terrestrial planets are ~0.1 but there exists a novel class of terrestrial planet system whose single planet undergoes large amplitude oscillations in orbital eccentricity and inclination; 2) by scaling our systems to match the observed semimajor axis distribution of giant exoplanets, we predict that terrestrial exoplanets in the same systems should be a few times more abundant at ~0.5 AU than giant or terrestrial exoplanets at 1 AU; 3) the Solar System appears to be unusual in terms of its combination of a rich terrestrial planet system and a low dust content. This may be explained by the weak, outward-directed instability that is thought to have caused the late heavy bombardment. The movie associated to Fig. 2 is available in electronic form at http://www.aanda.org

In Situ Probe Science at Saturn

NASA Astrophysics Data System (ADS)

Atkinson, David H.; Lunine, Jonathan I.; Simon-Miller, Amy A.; Atreya, Sushil K.; Brinckerhoff, William B.; Colaprete, Anthony; Coustenis, Athena; Fletcher, Leigh N.; Guillot, Tristan; Lebreton, Jean-Pierre; Mahaffy, Paul; Mousis, Olivier; Orton, Glenn S.; Reh, Kim; Spilker, Linda J.; Spilker, Thomas R.; Webster, Chris R.

2014-05-01

A fundamental goal of solar system exploration is to understand the origin of the solar system, the initial stages, conditions, and processes by which the solar system formed, how the formation process was initiated, and the nature of the interstellar seed material from which the solar system was born. Key to understanding solar system formation and subsequent dynamical and chemical evolution is the origin and evolution of the giant planets and their atmospheres. Several theories have been put forward to explain the process of solar system formation, and the origin and evolution of the giant planets and their atmospheres. Each theory offers quantifiable predictions of the abundances of noble gases He, Ne, Ar, Kr, and Xe, and abundances of key isotopic ratios 4He/3He, D/H, 15N/14N, 18O/16O, and 13C/12C. Detection of certain disequilibrium species, diagnostic of deeper internal processes and dynamics of the atmosphere, would also help discriminate between competing theories. Many of the key atmospheric constituents needed to discriminate between alternative theories of giant planet formation and chemical evolution are either spectrally inactive or primarily located in the deeper atmosphere inaccessible to remote sensing from Earth, flyby, or orbiting spacecraft. Abundance measurements of these key constituents, including the two major molecular carriers of carbon, methane and carbon monoxide (neither of which condense in Saturn's atmosphere), sulfur which is expected to be well-mixed below the 4 to 5-bar ammonium hydrosulfide (NH4SH) cloud, and gradients of nitrogen below the NH4SH cloud and oxygen in the upper layers of the H2O and H2O-NH4 solution cloud, must be made in situ and can only be achieved by an entry probe descending through 10 bars. Measurements of the critical abundance profiles of these key constituents into the deeper well-mixed atmosphere must be complemented by measurements of the profiles of atmospheric structure and dynamics at high vertical resolution that also require in situ exploration. The atmospheres of the giant planets can also serve as laboratories to better understand the atmospheric chemistries, dynamics, processes, and climates on all planets in the solar system including Earth, and offer a context and provide a ground truth for exoplanets and exoplanetary systems. Additionally, Giant planets have long been thought to play a critical role in the development of potentially habitable planetary systems. In the context of giant planet science provided by the Galileo, Juno, and Cassini missions to Jupiter and Saturn, a small, relatively shallow Saturn probe capable of measuring abundances and isotopic ratios of key atmospheric constituents, and atmospheric structure including pressures, temperatures, dynamics, and cloud locations and properties not accessible by remote sensing can serve to test competing theories of solar system and giant planet origin, chemical, and dynamical evolution. Acknowledgements This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. Copyright 2013 California Institute of Technology. U.S. Government sponsorship acknowledged. O. Mousis acknowledges support from CNES.

K2 Finds Earth-Sized Planets Artist Concept

NASA Image and Video Library

2016-07-18

This artist's concept shows NASA's Kepler Space Telescope on its K2 mission. In July 2016, an international team of astronomers announced they had discovered more than 100 new planets using this telescope. The batch includes four planets in the size range of Earth that are orbiting a single dwarf star, depicted in this illustration. Two of these planets are too hot to support life as we know it, but two are in the star's "habitable" zone, where liquid water could exist on the surface. These small, rocky worlds are far closer to their star than Mercury is to our sun. But because the star is smaller and cooler than ours, its habitable zone is much closer. One of the two planets in the habitable zone, K2-72c, has a "year" about 15 Earth-days long -- the time it takes to complete one orbit. This closer planet is likely about 10 percent warmer than Earth. The slightly more distant planet in the habitable zone, K2-72e, has a year lasting 24 Earth days, and would be about 6 percent colder than Earth. http://photojournal.jpl.nasa.gov/catalog/PIA20698

Exploring the Effects of Stellar Multiplicity on Exoplanet Occurrence Rates

NASA Astrophysics Data System (ADS)

Barclay, Thomas; Shabram, Megan

2017-06-01

Determining the frequency of habitable worlds is a key goal of the Kepler mission. During Kepler's four year investigation it detected thousands of transiting exoplanets with sizes varying from smaller than Mercury to larger than Jupiter. Finding planets was just the first step to determining frequency, and for the past few years the mission team has been modeling the reliability and completeness of the Kepler planet sample. One effect that has not typically been built into occurrence rate statistics is that of stellar multiplicity. If a planet orbits the primary star in a binary or triple star system then the transit depth will be somewhat diluted resulting in a modest underestimation in the planet size. However, if a detected planet orbits a fainter star then the error in measured planet radius can be very significant. We have taken a hypothetical star and planet population and passed that through a Kepler detection model. From this we have derived completeness corrections for a realistic case of a Universe with binary stars and compared that with a model Universe where all stars are single. We report on the impact that binaries have on exoplanet population statistics.

Utilizing the Upcoming Gravity Measurements from Cassini's Proximal Orbits for Studying the Atmospheric Dynamics of Saturn - How Deep Do the Winds Penetrate?

NASA Astrophysics Data System (ADS)

Kaspi, Y.; Galanti, E.

2014-12-01

At the end of the Cassini mission, the spacecraft will descend into close-by proximal orbits around Saturn. During those proximal orbits, Cassini will obtain high precision gravity measurements of the planet. In this talk, we will discuss how this data can be used to estimate the depth of the observed flows on the planet. This can be done in several ways: 1. measurements of the high order even harmonics which beyond J10 are dominated by the dynamics; 2. measurements of odd gravity harmonics which have no contribution from a static planet, and therefore are a pure signature of dynamics; 3. upper limits on the depth can be obtained by comparing low order even harmonics from dynamical models to the difference between the measured low order even harmonics and the largest possible values of a static planet; 4. direct latitudinally varying measurements of the gravity field exerted on the spacecraft. We will discuss how these methods may be applied and show that given the expected sensitivity of Cassini the odd harmonics J3 and J5 will have the best sensitivity to deep dynamics, allowing detection of winds reaching only O(100km) deep, if those exist on Saturn. We use a hierarchy of dynamical models ranging from full 3D dynamical circulation models to simplified dynamical models where the sensitivity of the gravity field to the dynamics can be explored. In order to invert the gravity field to be measured by Cassini into the depth dependent circulation, an adjoint inverse model is constructed for the dynamical models, thus allowing backward integration of the dynamical model. This tool can be used for examination of various scenarios, including cases in which the depth of the wind depends on latitudinal position. In summary, we expect that the very end of Cassini's tour holds an opportunity for gravity measurements that may finally allow answering one of the long-lasting puzzles in planetary science regarding the depth of the zonal jets on the gas giants. In fact, as Juno will be performing similar measurements we hope to be able to build a picture of the dynamics for both Jupiter and Saturn. Answering this puzzle, will likely help explain the origin of the multiple jet streams and strong equatorial superrotation on the gas giants.

Tatooines Future: The Eccentric Response of Keplers Circumbinary Planets to Common-Envelope Evolution of their Host Stars

NASA Technical Reports Server (NTRS)

Kostov, Veselin B.; Moore, Keavin; Tamayo, Daniel; Jayawardhana, Ray; Rinehart, Stephen A.

2016-01-01

Inspired by the recent Kepler discoveries of circumbinary planets orbiting nine close binary stars, we explore the fate of the former as the latter evolve off the main sequence. We combine binary star evolution models with dynamical simulations to study the orbital evolution of these planets as their hosts undergo common-envelope stages, losing in the process a tremendous amount of mass on dynamical timescales. Five of the systems experience at least one Roche-lobe overflow and common-envelope stages (Kepler-1647 experiences three), and the binary stars either shrink to very short orbits or coalesce; two systems trigger a double-degenerate supernova explosion. Kepler's circumbinary planets predominantly remain gravitationally bound at the end of the common-envelope phase, migrate to larger orbits, and may gain significant eccentricity; their orbital expansion can be more than an order of magnitude and can occur over the course of a single planetary orbit. The orbits these planets can reach are qualitatively consistent with those of the currently known post-common-envelope, eclipse-time variations circumbinary candidates. Our results also show that circumbinary planets can experience both modes of orbital expansion (adiabatic and non-adiabatic) if their host binaries undergo more than one common-envelope stage; multiplanet circumbinary systems like Kepler-47 can experience both modes during the same common-envelope stage. Additionally, unlike Mercury orbiting the Sun, a circumbinary planet with the same semi-major axis can survive the common envelope evolution of a close binary star with a total mass of 1 Solar Mass.

The Dynamics of Tightly-packed Planetary Systems in the Presence of an Outer Planet: Case Studies Using Kepler-11 and Kepler-90

NASA Astrophysics Data System (ADS)

Granados Contreras, A. P.; Boley, A. C.

2018-03-01

We explore the effects of an undetected outer giant planet on the dynamics, observability, and stability of Systems with Tightly-packed Inner Planets (STIPs). We use direct numerical simulations along with secular theory and synthetic secular frequency spectra to analyze how analogues of Kepler-11 and Kepler-90 behave in the presence of a nearly co-planar, Jupiter-like outer perturber with semimajor axes between 1 and 5.2 au. Most locations of the outer perturber do not affect the evolution of the inner planetary systems, apart from altering precession frequencies. However, there are locations at which an outer planet causes system instability due to, in part, secular eccentricity resonances. In Kepler-90, there is a range of orbital distances for which the outer perturber drives planets b and c, through secular interactions, onto orbits with inclinations that are ∼16° away from the rest of the planets. Kepler-90 is stable in this configuration. Such secular resonances can thus affect the observed multiplicity of transiting systems. We also compare the synthetic apsidal and nodal precession frequencies with the secular theory and find some misalignment between principal frequencies, indicative of strong interactions between the planets (consistent with the system showing TTVs). First-order libration angles are calculated to identify MMRs in the systems, for which two near-MMRs are shown in Kepler-90, with a 5:4 between b and c, as well as a 3:2 between g and h.

A whole new Mercury: MESSENGER reveals a dynamic planet at the last frontier of the inner solar system

NASA Astrophysics Data System (ADS)

Johnson, Catherine L.; Hauck, , Steven A.

2016-11-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission yielded a wealth of information about the innermost planet. For the first time, visible images of the entire planet, absolute altimetry measurements and a global gravity field, measurements of Mercury's surface composition, magnetic field, exosphere, and magnetosphere taken over more than four Earth years are available. From these data, two overarching themes emerge. First, multiple data sets and modeling efforts point toward a dynamic ancient history. Signatures of graphite in the crust suggest solidification of an early magma ocean, image data show extensive volcanism and tectonic features indicative of subsequent global contraction, and low-altitude measurements of magnetic fields reveal an ancient magnetic field. Second, the present-day Mercury environment is far from quiescent. Convective motions in the outer core support a modern magnetic field whose strength and geometry are unique among planets with global magnetic fields. Furthermore, periodic and aperiodic variations in the magnetosphere and exosphere have been observed, some of which couple to the surface and the planet's deep interior. Finally, signatures of geologically recent volatile activity at the surface have been detected. Mercury's early history and its present-day environment have common elements with the other inner solar system bodies. However, in each case there are also crucial differences and these likely hold the key to further understanding of Mercury and terrestrial planet evolution. MESSENGER's exploration of Mercury has enabled a new view of the innermost planet, and more importantly has set the stage for much-needed future exploration.

Tidal-Rotational Dynamics of Solar System Worlds, from the Moon to Pluto

NASA Astrophysics Data System (ADS)

Keane, James Tuttle

The spins of planetary bodies are not stagnant; they evolve in response to both external and internal forces. One way a planet's spin can change is through true polar wander. True polar wander is the reorientation of a planetary body with respect to its angular momentum vector, and occurs when mass is redistributed within the body, changing its principal axes of inertia. True polar wander can literally reshape a world, and has important implications for a variety of processes--from the long-term stability of polar volatiles in the permanently shadowed regions of airless worlds like the Moon and Mercury, to the global tectonic patterns of icy worlds like Pluto. In this dissertation, we investigate three specific instances of planetary true polar wander, and their associated consequences. In Chapter 2 we investigate the classic problem of the Moon's dynamical figure. By considering the effects of a fossil figure supported by an elastic lithosphere, and the contribution of impact basins to the figure, we find that the lunar figure is consistent with the Moon's lithosphere freezing in when the Moon was much closer to the Earth, on a low eccentricity synchronous orbit. The South Pole-Aitken impact basin is the single largest perturbation to the Moon's figure and resulted in tens of degrees of true polar wander after its formation. In Chapter 3 we continue our analyses of the lunar figure in light of the discovery of a lunar "volatile" paleopole, preserved in the distribution of hydrogen near the Moon's poles. We find that the formation and evolution of the Procellarum KREEP Terrain significantly altered the Moon's orientation, implying that some fraction of the Moon's polar volatiles are ancient--predating the geologic activity within the Procellarum region. In Chapter 4 we investigate how the formation of the giant, basin-filling glacier, Sputnik Planitia reoriented Pluto. This reorientation is recorded in both the present- day location of Sputnik Planitia (near the Pluto-Charon tidal axis), and the tectonic record of Pluto. This reorientation likely reflects a coupling between Pluto's volatile cycles and rotational dynamics, and may be active on other worlds with comparably large, mobile volatile reservoirs. Finally, in Chapter 5 we consider the broader context of these studies, and touch on future investigations of true polar wander on Mercury, Venus, Mars, Vesta, Ceres, and other worlds in our solar system.

A method for the investigation of hyperbolic motions in the gravitational field of a spheroidal planet

NASA Astrophysics Data System (ADS)

Konks, V. Ia.

1981-05-01

Barrar's (1961) method for the analysis of the motion of a satellite of an oblate planet is extended to the case of hyperbolic motion. An analysis is presented of the motion of a material point in the gravitational field of a fixed center, combined with a gravitational dipole located at the point of inertia of a dynamically symmetric planet. Formulas are obtained for the hyperbolic motion of a spacecraft in the gravitational field of a spheroidal planet with an accuracy up to the second zonal harmonic of the expansion of its potential into a Legendre polynomial series in spherical coordinates.

Characterizing extrasolar planets

NASA Astrophysics Data System (ADS)

Brown, Timothy M.

Transiting extrasolar planets provide the best current opportunities for characterizing the physical properties of extrasolar planets. In this review, I first describe the geometry of planetary transits, and methods for detecting and refining the observations of such transits. I derive the methods by which transit light curves and radial velocity data can be analyzed to yield estimates of the planetary radius, mass, and orbital parameters. I also show how visible-light and infrared spectroscopy can be valuable tools for understanding the composition, temperature, and dynamics of the atmospheres of transiting planets. Finally, I relate the outcome of a participatory lecture-hall exercise relating to one term in the Drake equation, namely the lifetime of technical civilizations.

Synergies Between Asteroseismology and Exoplanetary Science

NASA Astrophysics Data System (ADS)

Huber, Daniel

Over the past decade asteroseismology has become a powerful method to systematically characterize host stars and dynamical architectures of exoplanet systems. In this contribution I review current key synergies between asteroseismology and exoplanetary science such as the precise determination of planet radii and ages, the measurement of orbital eccentricities, stellar obliquities and their impact on hot Jupiter formation theories, and the importance of asteroseismology on spectroscopic analyses of exoplanet hosts. I also give an outlook on future synergies such as the characterization of sub-Neptune-size planets orbiting solar-type stars, the study of planet populations orbiting evolved stars, and the determination of ages of intermediate-mass stars hosting directly imaged planets.

The Constraint of Coplanarity: Compact multi-planet system outer architectures and formation.-UP

NASA Astrophysics Data System (ADS)

Jontof-Hutter, Daniel

The Kepler mission discovered 92 systems with 4 or more transiting exoplanets. Systems like Kepler-11 with six "mini-Neptunes" on orbital periods well inside that of Venus pose a challenge to planet formation theory which is broadly split into two competing paradigms. One theory invokes the formation of Neptunes beyond the "snow line", followed by inward migration and assembly into compact configurations near the star. The alternative is that low density planets form in situ at all distances in the protoplanetary nebula. The two paradigms disagree on the occurrence of Jovian planets at longer orbital periods than the transiting exoplanets since such massive planets would impede the inward migration of multiple volatile-rich planets to within a fraction of 1 AU. The likelihood of all the known planets at systems like Kepler-11 to be transiting is very sensitive to presence of outer Jovian planets for a wide range in orbital distance and relative inclination of the Jovian planet. This can put upper limits on the occurrence of Jovian planets by the condition that the six known planets have to have low mutual inclinations most of the time in order for their current cotransiting state to be plausible. Most of these systems have little or no RV data. Hence, our upper limits may be the best constraints on the occurrence of Jovian planets in compact co-planar systems for years to come, and may help distinguish the two leading paradigms of planet formation theory. Methodology. We propose to use an established n-body code (MERCURY) to perform long-term simulations of systems like Kepler-11 with the addition of a putative Jovian planet considering a range of orbital distances. These simulations will test for which initial conditions a Jovian planet would prevent the known planets from all transiting at the same time. We will 1) determine at what orbital distances and inclinations an outer Jovian planet would make the observed configuration of Kepler-11 very unlikely. 2) Test the effect of an undetected planet in the large dynamical space between Kepler-11 f and Kepler 11 g on our upper limits on a Jovian outer planet. 3) Repeat the analysis for all compact systems of 4 or more transiting planets with published planetary masses (including Kepler-79, Kepler-33, and Kepler-80) 5) Repeat the analysis for all systems of 4 or more transiting planets where the condition of long-term orbital stability provides useful upper limits on planetary masses, using their orbital periods and an appropriate mass-radius relation. 6) Measure an upper limit on the occurrence rate of outer Jovian planets. If we find an occurrence rate significantly lower than the known occurrence rate of Jovian planets from RV surveys, this would be evidence in support of the migration model as Jovian planets are expected impede the assembly of compact coplanar systems of low-density planets close to the host star. Relevance. According to the XRP Solicitation, investigations are expected to directly support the goal of "understanding exoplanetary systems", by doing one or more of the following..."improve understanding of the origins of exoplanetary systems". This proposal will help distinguish between competing paradigms in planet formation with dynamical modeling, and hence will improve our understanding of the origins of exoplanetary systems. This proposal will in no way require analysis of archival Kepler data, and relies only on the published masses, radii and orbital periods of high muliplicity systems discovered by Kepler. Therefore, our proposal is not appropriate for ADAP.

Asteroids in three-body mean motion resonances with planets

NASA Astrophysics Data System (ADS)

Smirnov, Evgeny A.; Dovgalev, Ilya S.; Popova, Elena A.

2018-04-01

We have identified all asteroids in three-body mean-motion resonances in all possible planets configurations. The identification was done dynamically: the orbits of the asteroids were integrated for 100,000 yrs and the set of the resonant arguments was numerically analyzed. We have found that each possible planets configuration has a lot of the resonant asteroids. In total 65,972 resonant asteroids (≈14.1% of the total number of 467,303 objects from AstDyS database) have been identified.

The Realm of Close-in Planets

NASA Astrophysics Data System (ADS)

Clark Fabrycky, Daniel

2018-04-01

The space within about 1 AU of other stars in the Galaxy is an exciting place to be a planet. The categories of "hot Jupiters", "super-Earths", "sub-Neptunes", and recently terrestrial analogues, have been revealed by Doppler programs and space-based transit missions. In this talk, we review how N-body modelling of the data teach us the properties of these planets and their orbital architectures. We also review the major dynamical ideas about the formation and evolution of these systems.

Comparative Studies to Be a Theme for the Joint Assembly in Montreal

NASA Astrophysics Data System (ADS)

Mendillo, Michael; Schubert, Gerald; Alexander, Joan; Strangeway, Robert

2004-02-01

To have a truly global view of geophysical systems, it helps to have a few globes to view. Our solar system offers a rich set of case studies on how environmental systems form and evolve. The temperature structures of atmospheres, their circulation patterns, and their optical emissions are governed by the same basic laws of physics and photochemistry, but with constituents and solar flux input values that vary dramatically over the span of the planets. The escape of gases from the Earth and those planets and moons with dense atmospheres involve processes rather different from those associated with sputtered gases from the far more abundant regoliths of rock and ice. The origins and dynamics of plasmas and magnetic fields, their interactions with the flowing solar wind and/or rapidly rotating planetary fields, and episodic ``space weather'' events provide additional areas of common science in remarkably different settings. The Earth and its companions thus comprise the only known set of experiments in planetary formation for which there is actual data to validate and to challenge theory and computer models. While observations are abundant for Earth, and beyond the ``discovery mode'' set for many of the planets and moons, there remain crucial gaps in our understanding and formidable problems to solve at each of these worlds. Coupling processes, perhaps most of all, from regions below and above the environmental systems being studied are at the forefront of current work, drawing attention to the need for advanced observational capabilities and breakthroughs in computer simulation techniques.

[Dr James Lovelock and story about GAIA hypothesis].

PubMed

Gajić, Vladimir

2011-01-01

Gaia is the Anglo-Saxon term for the Hellenic term Gea or Ge, which means Earth. The GAIA hypothesis was launched almost 40 years ago by the famous chemist James Lovelock, who was engaged by the National Aeronautics and Space Administration (NASA) to create a sensitive instrument for searching forms of extraterrestrial life on other planets. Then he published the book The ages of GAIA, which perturbed the world's scientific public of those days. Lovelock struck upon this idea in the late sixties of the past century, during the space race with Russians, when he was hired hy the National Aeronautics and Space Administration to conduct a series of experiments to find and explore life forms on the planet Mars. Experiments executed by the American module Viking failed to trace any life form, as Lovelock had predicted. He called it a dead equilibrium. Then he turned to Earth, whose perspective is totally different from its first neighbors. Venus and Mars, and is far from a dead equilibrium. DAISYWORLD: In this hypothesis. Lovelock represents Earth as one living, giant super organism, composed of all living creatures and its material environnent. In that super organisnm, the level of oxygen, weather conditions, ocean salinity and so on are under constant influence of physical, chemical and biological processes, which provide the existence for such life forms on Earth. Dr James Lovelock represents a pioneer of climatology, and his hypothesis gives a unique insight into the correlation of dynamic processes on our planet, no matter whether they are of physical or biological nature.

Theoretical Implications of the PSR B1620-26 Triple System and Its Planet

NASA Astrophysics Data System (ADS)

Ford, Eric B.; Joshi, Kriten J.; Rasio, Frederic A.; Zbarsky, Boris

2000-01-01

We present a new theoretical analysis of the PSR B1620-26 triple system in the globular cluster M4, based on the latest radio pulsar timing data, which now include measurements of five time derivatives of the pulse frequency. These data allow us to determine the mass and orbital parameters of the second companion completely (up to the usual unknown orbital inclination angle i2). The current best-fit parameters correspond to a second companion of planetary mass, m2sini2~=7×10-3 Msolar , in an orbit of eccentricity e2~=0.45 and semimajor axis a2~=60 AU. Using numerical scattering experiments, we study a possible formation scenario for the triple system, which involves a dynamical exchange interaction between the binary pulsar and a primordial star-planet system. The current orbital parameters of the triple are consistent with such a dynamical origin and suggest that the separation of the parent star-planet system was very large, >~50 AU. We also examine the possible origin of the anomalously high eccentricity of the inner binary pulsar. While this eccentricity could have been induced during the same dynamical interaction that created the triple, we find that it could equally well arise from long-term secular perturbation effects in the triple, combining the general relativistic precession of the inner orbit with the Newtonian gravitational perturbation of the planet. The detection of a planet in this system may be taken as evidence that large numbers of extrasolar planetary systems, not unlike those discovered recently in the solar neighborhood, also exist in old star clusters.

Trojans in habitable zones.

PubMed

Schwarz, Richard; Pilat-Lohinger, Elke; Dvorak, Rudolf; Erdi, Balint; Sándor, Zsolt

2005-10-01

With the aid of numerical experiments we examined the dynamical stability of fictitious terrestrial planets in 1:1 mean motion resonance with Jovian-like planets of extrasolar planetary systems. In our stability study of the so-called "Trojan" planets in the habitable zone, we used the restricted three-body problem with different mass ratios of the primary bodies. The application of the three-body problem showed that even massive Trojan planets can be stable in the 1:1 mean motion resonance. From the 117 extrasolar planetary systems only 11 systems were found with one giant planet in the habitable zone. Out of this sample set we chose four planetary systems--HD17051, HD27442, HD28185, and HD108874--for further investigation. To study the orbital behavior of the stable zone in the different systems, we used direct numerical computations (Lie Integration Method) that allowed us to determine the escape times and the maximum eccentricity of the fictitious "Trojan planets."

Timing of the formation and migration of giant planets as constrained by CB chondrites

PubMed Central

Johnson, Brandon C.; Walsh, Kevin J.; Minton, David A.; Krot, Alexander N.; Levison, Harold F.

2016-01-01

The presence, formation, and migration of giant planets fundamentally shape planetary systems. However, the timing of the formation and migration of giant planets in our solar system remains largely unconstrained. Simulating planetary accretion, we find that giant planet migration produces a relatively short-lived spike in impact velocities lasting ~0.5 My. These high-impact velocities are required to vaporize a significant fraction of Fe,Ni metal and silicates and produce the CB (Bencubbin-like) metal-rich carbonaceous chondrites, a unique class of meteorites that were created in an impact vapor-melt plume ~5 My after the first solar system solids. This indicates that the region where the CB chondrites formed was dynamically excited at this early time by the direct interference of the giant planets. Furthermore, this suggests that the formation of the giant planet cores was protracted and the solar nebula persisted until ~5 My. PMID:27957541

Dynamics and Chemistry of Planet Construction

NASA Astrophysics Data System (ADS)

Taylor, G. J.

2010-03-01

Sophisticated calculations of how planetesimals assembled into the terrestrial planets can be tested by using models of the chemistry of the solar nebula. Jade Bond (previously at University of Arizona and now at the Planetary Science Institute, Tucson, AZ), Dante Lauretta (University of Arizona) and Dave O'Brien (Planetary Sciences Institute) combined planetary accretion simulations done by O'Brien, Alessandro Morbidelli (Observatoire de Nice, France), and Hal Levison (Southwest Research Institute, Boulder) with calculations of the solar nebula chemistry as a function of time and distance from the Sun to determine the overall chemical composition of the planets formed in the simulations. They then compared the simulated planets with the compositions of Earth and Mars. The simulated planets have chemical compositions similar to real planets, indicating that the accretion calculations are reasonable. Questions remain about the accretion of water and other highly volatile compounds, including C and N, which are essential for life.

Timing of the formation and migration of giant planets as constrained by CB chondrites.

PubMed

Johnson, Brandon C; Walsh, Kevin J; Minton, David A; Krot, Alexander N; Levison, Harold F

2016-12-01

The presence, formation, and migration of giant planets fundamentally shape planetary systems. However, the timing of the formation and migration of giant planets in our solar system remains largely unconstrained. Simulating planetary accretion, we find that giant planet migration produces a relatively short-lived spike in impact velocities lasting ~0.5 My. These high-impact velocities are required to vaporize a significant fraction of Fe,Ni metal and silicates and produce the CB (Bencubbin-like) metal-rich carbonaceous chondrites, a unique class of meteorites that were created in an impact vapor-melt plume ~5 My after the first solar system solids. This indicates that the region where the CB chondrites formed was dynamically excited at this early time by the direct interference of the giant planets. Furthermore, this suggests that the formation of the giant planet cores was protracted and the solar nebula persisted until ~5 My.

Leveraging the Thousands of Known Planets to Inform TESS Follow-Up

NASA Astrophysics Data System (ADS)

Ballard, Sarah

2017-10-01

The Solar System furnishes our most familiar planetary architecture: many planets, orbiting nearly coplanar to one another. However, a typical system of planets in the Milky Way orbits a much smaller M dwarf star, and these stars furnish a different blueprint in key ways than the conditions that nourished evolution of life on Earth. With ensemble studies of hundreds-to-thousands of exoplanets, I will describe the emerging links between planet formation from disks, orbital dynamics of planets, and the content and observability of planetary atmospheres. These quantities can be tied to observables even in discovery light curves, to enable judicious selection of follow-up targets from the ground and from space. After TESS exoplanet discoveries start in earnest, the studies of individual planets with large, space-based platforms comprise the clear next step toward understanding the hospitability of the Milky Way to life. Our success hinges upon leveraging the many thousands of planet discoveries in hand to determine how to use these precious and limited resources.

HIDING IN THE SHADOWS: SEARCHING FOR PLANETS IN PRE-TRANSITIONAL AND TRANSITIONAL DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dobinson, Jack; Leinhardt, Zoë M.; Dodson-Robinson, Sarah E.

Transitional and pre-transitional disks can be explained by a number of mechanisms. This work aims to find a single observationally detectable marker that would imply a planetary origin for the gap and, therefore, indirectly indicate the presence of a young planet. N-body simulations were conducted to investigate the effect of an embedded planet of one Jupiter mass on the production of instantaneous collisional dust derived from a background planetesimal disk. Our new model allows us to predict the dust distribution and resulting observable markers with greater accuracy than previous works. Dynamical influences from a planet on a circular orbit aremore » shown to enhance dust production in the disk interior and exterior to the planet orbit, while removing planetesimals from the orbit itself, creating a clearly defined gap. In the case of an eccentric planet, the gap opened by the planet is not as clear as the circular case, but there is a detectable asymmetry in the dust disk.« less

The origin of the eccentricity of the hot Jupiter in CI Tau

NASA Astrophysics Data System (ADS)

Rosotti, G. P.; Booth, R. A.; Clarke, C. J.; Teyssandier, J.; Facchini, S.; Mustill, A. J.

2017-01-01

Following the recent discovery of the first radial velocity planet in a star still possessing a protoplanetary disc (CI Tau), we examine the origin of the planet's eccentricity (e ˜0.3). We show through long time-scale (105 orbits) simulations that the planetary eccentricity can be pumped by the disc, even when its local surface density is well below the threshold previously derived from short time-scale integrations. We show that the disc may be able to excite the planet's orbital eccentricity in <1 Myr for the system parameters of CI Tau. We also perform two-planet scattering experiments and show that alternatively the observed planet may plausibly have acquired its eccentricity through dynamical scattering of a migrating lower mass planet, which has either been ejected from the system or swallowed by the central star. In the latter case the present location and eccentricity of the observed planet can be recovered if it was previously stalled within the disc's magnetospheric cavity.

Volatile inventory and early evolution of the planetary atmospheres

NASA Astrophysics Data System (ADS)

Marov, Mikhail Ya.; Ipatov, Sergei I.

Formation of atmospheres of the inner planets involved the concurrent processes of mantle degassing and collisions that culminated during the heavy bombardment. Volatile-rich icy planetesimals impacting on the planets as a late veneer strongly contributed to the volatile inventory. Icy remnants of the outer planet accretion significantly complemented the accumulation of the lithophile and atmophile elements forced out onto the surface of the inner planets from silicate basaltic magma enriched in volatiles. Orbital dynamics of small bodies, including near-Earth asteroids, comets, and bodies from the Edgeworth-Kuiper belt evolving to become inner planet crossers, is addressed to examine different plausible amounts of volatile accretion. The relative importance of comets and chondrites in the delivery of volatiles is constrained by the observed fractionation pattern of noble gas abundances in the atmospheres of inner planets. The following development of the early atmospheres depended on the amount of volatiles expelled from the interiors and deposited by impactors, while the position of the planet relative to the Sun and its mass affected its climatic evolution.

EFFECTS OF DYNAMICAL EVOLUTION OF GIANT PLANETS ON THE DELIVERY OF ATMOPHILE ELEMENTS DURING TERRESTRIAL PLANET FORMATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matsumura, Soko; Brasser, Ramon; Ida, Shigeru, E-mail: s.matsumura@dundee.ac.uk

2016-02-10

Recent observations started revealing the compositions of protostellar disks and planets beyond the solar system. In this paper, we explore how the compositions of terrestrial planets are affected by the dynamical evolution of giant planets. We estimate the initial compositions of the building blocks of these rocky planets by using a simple condensation model, and numerically study the compositions of planets formed in a few different formation models of the solar system. We find that the abundances of refractory and moderately volatile elements are nearly independent of formation models, and that all the models could reproduce the abundances of thesemore » elements of the Earth. The abundances of atmophile elements, on the other hand, depend on the scattering rate of icy planetesimals into the inner disk, as well as the mixing rate of the inner planetesimal disk. For the classical formation model, neither of these mechanisms are efficient and the accretion of atmophile elements during the final assembly of terrestrial planets appears to be difficult. For the Grand Tack model, both of these mechanisms are efficient, which leads to a relatively uniform accretion of atmophile elements in the inner disk. It is also possible to have a “hybrid” scenario where the mixing is not very efficient but the scattering is efficient. The abundances of atmophile elements in this case increase with orbital radii. Such a scenario may occur in some of the extrasolar planetary systems, which are not accompanied by giant planets or those without strong perturbations from giants. We also confirm that the Grand Tack scenario leads to the distribution of asteroid analogues where rocky planetesimals tend to exist interior to icy ones, and show that their overall compositions are consistent with S-type and C-type chondrites, respectively.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bromley, Benjamin C.; Kenyon, Scott J., E-mail: bromley@physics.utah.edu, E-mail: skenyon@cfa.harvard.edu

Correlations in the orbits of several minor planets in the outer solar system suggest the presence of a remote, massive Planet Nine. With at least 10 times the mass of the Earth and a perihelion well beyond 100 au, Planet Nine poses a challenge to planet formation theory. Here we expand on a scenario in which the planet formed closer to the Sun and was gravitationally scattered by Jupiter or Saturn onto a very eccentric orbit in an extended gaseous disk. Dynamical friction with the gas then allowed the planet to settle in the outer solar system. We explore thismore » possibility with a set of numerical simulations. Depending on how the gas disk evolves, scattered super-Earths or small gas giants settle on a range of orbits, with perihelion distances as large as 300 au. Massive disks that clear from the inside out on million-year timescales yield orbits that allow a super-Earth or gas giant to shepherd the minor planets as observed. A massive planet can achieve a similar orbit in a persistent, low-mass disk over the lifetime of the solar system.« less

SIM Lite Detection of Habitable Planets in P-Type Binary-Planetary Systems

NASA Technical Reports Server (NTRS)

Pan, Xiaopei; Shao, Michael; Shaklan, Stuart; Goullioud, Renaud

2010-01-01

Close binary stars like spectroscopic binaries create a completely different environment than single stars for the evolution of a protoplanetary disk. Dynamical interactions between one star and protoplanets in such systems provide more challenges for theorists to model giant planet migration and formation of multiple planets. For habitable planets the majority of host stars are in binary star systems. So far only a small amount of Jupiter-size planets have been discovered in binary stars, whose minimum separations are 20 AU and the median value is about 1000 AU (because of difficulties in radial velocity measurements). The SIM Lite mission, a space-based astrometric observatory, has a unique capability to detect habitable planets in binary star systems. This work analyzed responses of the optical system to the field stop for companion stars and demonstrated that SIM Lite can observe exoplanets in visual binaries with small angular separations. In particular we investigated the issues for the search for terrestrial planets in P-type binary-planetary systems, where the planets move around both stars in a relatively distant orbit.

Vega's hot dust from icy planetesimals scattered inwards by an outward-migrating planetary system

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Bonsor, Amy

2014-07-01

Vega has been shown to host multiple dust populations, including both hot exozodiacal dust at sub-au radii and a cold debris disc extending beyond 100 au. We use dynamical simulations to show how Vega's hot dust can be created by long-range gravitational scattering of planetesimals from its cold outer regions. Planetesimals are scattered progressively inwards by a system of 5-7 planets from 30 to 60 au to very close-in. In successful simulations, the outermost planets are typically Neptune mass. The back-reaction of planetesimal scattering causes these planets to migrate outwards and continually interact with fresh planetesimals, replenishing the source of scattered bodies. The most favourable cases for producing Vega's exozodi have negative radial mass gradients, with sub-Saturn- to Jupiter-mass inner planets at 5-10 au and outer planets of 2.5 - 20 M⊕ . The mechanism fails if a Jupiter-sized planet exists beyond ˜15 au because the planet preferentially ejects planetesimals before they can reach the inner system. Direct-imaging planet searches can therefore directly test this mechanism.

Trojan resonant dynamics, stability, and chaotic diffusion, for parameters relevant to exoplanetary systems

NASA Astrophysics Data System (ADS)

Páez, Rocío Isabel; Efthymiopoulos, Christos

2015-02-01

The possibility that giant extrasolar planets could have small Trojan co-orbital companions has been examined in the literature from both viewpoints of the origin and dynamical stability of such a configuration. Here we aim to investigate the dynamics of hypothetical small Trojan exoplanets in domains of secondary resonances embedded within the tadpole domain of motion. To this end, we consider the limit of a massless Trojan companion of a giant planet. Without other planets, this is a case of the elliptic restricted three body problem (ERTBP). The presence of additional planets (hereafter referred to as the restricted multi-planet problem, RMPP) induces new direct and indirect secular effects on the dynamics of the Trojan body. The paper contains a theoretical and a numerical part. In the theoretical part, we develop a Hamiltonian formalism in action-angle variables, which allows us to treat in a unified way resonant dynamics and secular effects on the Trojan body in both the ERTBP or the RMPP. In both cases, our formalism leads to a decomposition of the Hamiltonian in two parts, . , called the basic model, describes resonant dynamics in the short-period (epicyclic) and synodic (libration) degrees of freedom, while contains only terms depending trigonometrically on slow (secular) angles. is formally identical in the ERTBP and the RMPP, apart from a re-definition of some angular variables. An important physical consequence of this analysis is that the slow chaotic diffusion along resonances proceeds in both the ERTBP and the RMPP by a qualitatively similar dynamical mechanism. We found that this is best approximated by the paradigm of `modulational diffusion'. In the paper's numerical part, we then focus on the ERTBP in order to make a detailed numerical demonstration of the chaotic diffusion process along resonances. Using color stability maps, we first provide a survey of the resonant web for characteristic mass parameter values of the primary, in which the secondary resonances from 1:5 to 1:12 (ratio of the short over the synodic period), as well as their transverse resonant multiplets, appear. We give numerical examples of diffusion of weakly chaotic orbits in the resonant web. We finally make a statistics of the escaping times in the resonant domain, and find power-law tails of the distribution of the escaping times for the slowly diffusing chaotic orbits. Implications of resonant dynamics in the search for Trojan exoplanets are discussed.

Hubble 2020: Outer Planet Atmospheres Legacy (OPAL) Program

NASA Astrophysics Data System (ADS)

Simon, Amy

2017-08-01

Long time base observations of the outer planets are critical in understanding the atmospheric dynamics and evolution of the gas giants. We propose yearly monitoring of each giant planet for the remainder of Hubble's lifetime to provide a lasting legacy of increasingly valuable data for time-domain studies. The Hubble Space Telescope is a unique asset to planetary science, allowing high spatial resolution data with absolute photometric knowledge. For the outer planets, gas/ice giant planets Jupiter, Saturn, Uranus and Neptune, many phenomena happen on timescales of years to decades, and the data we propose are beyond the scope of a typical GO program. Hubble is the only platform that can provide high spatial resolution global studies of cloud coloration, activity, and motion on a consistent time basis to help constrain the underlying mechanics.

Shell worlds

NASA Astrophysics Data System (ADS)

Roy, Kenneth I.; Kennedy, Robert G., III; Fields, David E.

2013-02-01

The traditional concept of terraforming assumes ready availability of candidate planets with acceptable qualities: orbiting a star in its "Goldilocks zone", liquid water, enough mass, years longer than days, magnetic field, etc. But even stipulating affordable interstellar travel, we still might never find a good candidate elsewhere. Whatever we found likely would require centuries of heavy terraforming, just as Mars or Venus would here. Our increasing appreciation of the ubiquity of life suggests that any terra nova would already possess it. We would then face the dilemma of introducing alien life forms (us, our microbes) into another living world. Instead, we propose a novel method to create habitable environments for humanity by enclosing airless, sterile, otherwise useless planets, moons, and even large asteroids within engineered shells, which avoids the conundrum. These shells are subject to two opposing internal stresses: compression due to the primary's gravity, and tension from atmospheric pressure contained inside. By careful design, these two cancel each other resulting in zero net shell stress. Beneath the shell an Earth-like environment could be created similar in almost all respects to that of Home, except for gravity, regardless of the distance to the sun or other star. Englobing a small planet, moon, or even a dwarf planet like Ceres, would require astronomical amounts of material (quadrillions of tons) and energy, plus a great deal of time. It would be a quantum leap in difficulty over building Dyson Dots or industrializing our solar system, perhaps comparable to a mission across interstellar space with a living crew within their lifetime. But when accomplished, these constructs would be complete (albeit small) worlds, not merely large habitats. They could be stable across historic timescales, possibly geologic. Each would contain a full, self-sustaining ecology, which might evolve in curious directions over time. This has interesting implications for SETI as well.

Taking the Earth's Pulse

USGS Publications Warehouse

Woodward, Robert L.; Benz, Harley Mitchell; Shedlock, Kaye M.; Brown, William M.

2000-01-01

During the past 35 years, scientists have developed a vast network of seismometers that record earthquakes, volcanic eruptions, and nuclear explosions throughout the world. Seismographic data support disaster response, scientific research, and global security. With this network, the United States maintains world leadership in monitoring the greatest natural and technological events that threaten our planet's population.

Taking the Earth's pulse

USGS Publications Warehouse

Woodward, Robert L.; Benz, Harly M.; Brown, William M.

1997-01-01

During the past 35 years, scientists have developed a vast network of seismometers that record earthquakes, volcanic eruptions, and nuclear explosions throughout the world. Seismographic data support disaster response, scientific research, and global security. With this network, the United States maintains world leadership in monitoring the greatest natural and technological events that threaten our planet's population.

NASA NASA CONNECT: Special World Space Congress. [Videotape].

ERIC Educational Resources Information Center

National Aeronautics and Space Administration, Hampton, VA. Langley Research Center.

NASA CONNECT is an annual series of free integrated mathematics, science, and technology instructional distance learning programs for students in grades 5-8. This video presents the World Space Congress 2002, the meeting of the decade for space professionals. Topics discussed range from the discovery of distant planets to medical advancements,…

The Immersive LearningScape--Knowledge Transposed: Learning Globally, Applying Locally

ERIC Educational Resources Information Center

Jimenez-Eliaeson, Tomas

2011-01-01

In an increasingly global world, where events in one corner of the world simultaneously affect other remote areas of the planet, global competition is becoming a continuously evolving phenomenon. Competition is also increasingly becoming an individual endeavor. Individual's own knowledge and skills will be the differentiators in a global economy.…

Waking up to Water

ERIC Educational Resources Information Center

Hines, Chris

2007-01-01

Climate change is having a major effect on water cycles. There is an increased intensity and frequency of severe storms resulting in flooding. Floods in other parts of the world cause death on a major scale. Meanwhile across the planet, one billion people (a sixth of the world's population) do not have access to safe drinking water, and two…

Junior BioBlitz Takes Learning Outside

ERIC Educational Resources Information Center

Himschoot, Rebecca

2017-01-01

Evidence is mounting that children have decreasing exposure to the natural world, which makes sense as the population of the planet urbanizes and many interests and assignments involve digital technology. According to the United Nations, 54% of the world's population now live in cities (2014), and a 2010 study by the Kaiser Health Foundation found…

Recovering Neptune 170 Years After its Initial Discovery

NASA Astrophysics Data System (ADS)

Myles, Justin

2017-01-01

Recent work by Trujillo and Shephard (2014) and Batygin and Brown (2016) has shown an as-yet unexplained clustering of the periapse vectors of the most distant Kuiper Belt objects. This unusual clustering has motivated the search for an unseen perturbing planet that is responsible for maintaining the alignment. As a proof of concept of a technique for locating unseen solar system planets, we use dynamical N-body integrations to simulate the orbital dynamics of distant Kuiper Belt objects, with the aim of determining the orbital parameters of Neptune (which, for the sake of exercise, we assume is, as-yet, undiscovered). In this poster, we determine the accuracy with which the perturbing planet’s orbital elements and sky location can be determined, and we show how the lessons learned can improve the search strategy for potentially undiscovered trans-Neptunian planets.

Planetary Systems Dynamics Eccentric patterns in debris disks & Planetary migration in binary systems

NASA Astrophysics Data System (ADS)

Faramaz, V.; Beust, H.; Augereau, J.-C.; Bonsor, A.; Thébault, P.; Wu, Y.; Marshall, J. P.; del Burgo, C.; Ertel, S.; Eiroa, C.; Montesinos, B.; Mora, A.

2014-01-01

We present some highlights of two ongoing investigations that deal with the dynamics of planetary systems. Firstly, until recently, observed eccentric patterns in debris disks were found in young systems. However recent observations of Gyr-old eccentric debris disks leads to question the survival timescale of this type of asymmetry. One such disk was recently observed in the far-IR by the Herschel Space Observatory around ζ2 Reticuli. Secondly, as a binary companion orbits a circumprimary disk, it creates regions where planet formation is strongly handicapped. However, some planets were detected in this zone in tight binary systems (γ Cep, HD 196885). We aim to determine whether a binary companion can affect migration such that planets are brought in these regions and focus in particular on the planetesimal-driven migration mechanism.

ARCHITECTURE AND DYNAMICS OF KEPLER'S CANDIDATE MULTIPLE TRANSITING PLANET SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lissauer, Jack J.; Jenkins, Jon M.; Borucki, William J.

About one-third of the {approx}1200 transiting planet candidates detected in the first four months of Kepler data are members of multiple candidate systems. There are 115 target stars with two candidate transiting planets, 45 with three, 8 with four, and 1 each with five and six. We characterize the dynamical properties of these candidate multi-planet systems. The distribution of observed period ratios shows that the vast majority of candidate pairs are neither in nor near low-order mean-motion resonances. Nonetheless, there are small but statistically significant excesses of candidate pairs both in resonance and spaced slightly too far apart to bemore » in resonance, particularly near the 2:1 resonance. We find that virtually all candidate systems are stable, as tested by numerical integrations that assume a nominal mass-radius relationship. Several considerations strongly suggest that the vast majority of these multi-candidate systems are true planetary systems. Using the observed multiplicity frequencies, we find that a single population of planetary systems that matches the higher multiplicities underpredicts the number of singly transiting systems. We provide constraints on the true multiplicity and mutual inclination distribution of the multi-candidate systems, revealing a population of systems with multiple super-Earth-size and Neptune-size planets with low to moderate mutual inclinations.« less

Characterizing Transiting Planets with JWST Spectra: Simulations and Retrievals

NASA Technical Reports Server (NTRS)

Greene, Tom; Line, Michael; Fortney, Jonathan

2015-01-01

There are now well over a thousand confirmed exoplanets, ranging from hot to cold and large to small worlds. JWST spectra will provide much more detailed information on the molecular constituents, chemical compositions, and thermal properties of the atmospheres of transiting planets than is now known. We explore this by modeling clear, cloudy,and high mean molecular weight atmospheres of typical hot Jupiter, warm Neptune, warm sub-Neptune, and cool super-Earth planets and then simulating their JWST transmission and emission spectra. These simulations were performed for several JWST instrument modes over 1 - 11 microns and incorporate realistic signal and noise components. We then performed state-of the art retrievals to determine how well temperatures and abundances (CO, CO2, H2O, NH3) will be constrained and over what pressures for these different planet types. Using these results, we appraise what instrument modes will be most useful for determining what properties of the different planets, and we assess how well we can constrain their compositions, CO ratios, and temperature profiles.

Ancient Planet in a Globular Cluster Core

NASA Image and Video Library

2010-03-31

Release Date: July 10, 2003 A rich starry sky fills the view from an ancient gas-giant planet in the core of the globular star cluster M4, as imagined in this artist's concept. The 13-billion-year-old planet orbits a helium white-dwarf star and the millisecond pulsar B1620-26, seen at lower left. The globular cluster is deficient in heavier elements for making planets, so the existence of such a world implies that planet formation may have been quite efficient and common in the early universe. Object Names: B1620-26, M4 Image Type: Artwork Illustration Credit: NASA and G. Bacon (STScI) To learn more about this image go to: www.nasa.gov/centers/goddard/news/topstory/2003/0709hstss... NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Observability of planet-disc interactions in CO kinematics

NASA Astrophysics Data System (ADS)

Pérez, Sebastián; Casassus, S.; Benítez-Llambay, P.

2018-06-01

Empirical evidence of planets in gas-rich circumstellar discs is required to constrain giant planet formation theories. Here we study the kinematic patterns which arise from planet-disc interactions and their observability in CO rotational emission lines. We perform three-dimensional hydrodynamical simulations of single giant planets, and predict the emergent intensity field with radiative transfer. Pressure gradients at planet-carved gaps, spiral wakes and vortices bear strong kinematic counterparts. The iso-velocity contours in the CO(2-1) line centroids vo reveal large-scale perturbations, corresponding to abrupt transitions from below sub-Keplerian to super-Keplerian rotation along with radial and vertical flows. The increase in line optical depth at the edge of the gap also modulates vo, but this is a mild effect compared to the dynamical imprint of the planet-disc interaction. The large-scale deviations from the Keplerian rotation thus allow the planets to be indirectly detected via the first moment maps of molecular gas tracers, at ALMA angular resolutions. The strength of these deviations depends on the mass of the perturber. This initial study paves the way to eventually determine the mass of the planet by comparison with more detailed models.

Infrared radiation from an extrasolar planet.

PubMed

Deming, Drake; Seager, Sara; Richardson, L Jeremy; Harrington, Joseph

2005-04-07

A class of extrasolar giant planets--the so-called 'hot Jupiters' (ref. 1)--orbit within 0.05 au of their primary stars (1 au is the Sun-Earth distance). These planets should be hot and so emit detectable infrared radiation. The planet HD 209458b (refs 3, 4) is an ideal candidate for the detection and characterization of this infrared light because it is eclipsed by the star. This planet has an anomalously large radius (1.35 times that of Jupiter), which may be the result of ongoing tidal dissipation, but this explanation requires a non-zero orbital eccentricity (approximately 0.03; refs 6, 7), maintained by interaction with a hypothetical second planet. Here we report detection of infrared (24 microm) radiation from HD 209458b, by observing the decrement in flux during secondary eclipse, when the planet passes behind the star. The planet's 24-microm flux is 55 +/- 10 microJy (1sigma), with a brightness temperature of 1,130 +/- 150 K, confirming the predicted heating by stellar irradiation. The secondary eclipse occurs at the midpoint between transits of the planet in front of the star (to within +/- 7 min, 1sigma), which means that a dynamically significant orbital eccentricity is unlikely.

An independent planet search in the Kepler dataset. II. An extremely low-density super-Earth mass planet around Kepler-87

NASA Astrophysics Data System (ADS)

Ofir, Aviv; Dreizler, Stefan; Zechmeister, Mathias; Husser, Tim-Oliver

2014-01-01

Context. The primary goal of the Kepler mission is the measurement of the frequency of Earth-like planets around Sun-like stars. However, the confirmation of the smallest of Kepler's candidates in long periods around FGK dwarfs is extremely difficult or even beyond the limit of current radial velocity technology. Transit timing variations (TTVs) may offer the possibility for these confirmations of near-resonant multiple systems by the mutual gravitational interaction of the planets. Aims: We previously detected the second planet candidate in the KOI 1574 system. The two candidates have relatively long periods (about 114 d and 191 d) and are in 5:3 resonance. We therefore searched for TTVs in this particularly promising system. Methods: The full Kepler data was detrended with the proven SARS pipeline. The entire data allowed one to search for TTVs of the above signals, and to search for additional transit-like signals. Results: We detected strong anti-correlated TTVs of the 114 d and 191 d signals, dynamically confirming them as members of the same system. Dynamical simulations reproducing the observed TTVs allowed us to also determine the masses of the planets. We found KOI 1574.01 (hereafter Kepler-87 b) to have a radius of 13.49 ± 0.55 R⊕ and a mass of 324.2 ± 8.8 M⊕, and KOI 1574.02 (Kepler-87 c) to have a radius of 6.14 ± 0.29 R⊕ and a mass of 6.4 ± 0.8 M⊕. Both planets have low densities of 0.729 and 0.152 g cm-3, respectively, which is non-trivial for such cold and old (7-8 Gyr) planets. Specifically, Kepler-87 c is the lowest-density planet in the super-Earth mass range. Both planets are thus particularly amenable to modeling and planetary structure studies, and also present an interesting case where ground-based photometric follow-up of Kepler planets is very desirable. Finally, we also detected two more short-period super-Earth sized (<2 R⊕) planetary candidates in the system, making the relatively high multiplicity of this system notable against the general paucity of multiple systems in the presence of giant planets like Kepler-87 b.

Detectable close-in planets around white dwarfs through late unpacking

NASA Astrophysics Data System (ADS)

Veras, Dimitri; Gänsicke, Boris T.

2015-02-01

Although 25-50 per cent of white dwarfs (WDs) display evidence for remnant planetary systems, their orbital architectures and overall sizes remain unknown. Vibrant close-in (≃1 R⊙) circumstellar activity is detected at WDs spanning many Gyr in age, suggestive of planets further away. Here we demonstrate how systems with 4 and 10 closely packed planets that remain stable and ordered on the main sequence can become unpacked when the star evolves into a WD and experience pervasive inward planetary incursions throughout WD cooling. Our full-lifetime simulations run for the age of the Universe and adopt main-sequence stellar masses of 1.5, 2.0 and 2.5 M⊙, which correspond to the mass range occupied by the progenitors of typical present-day WDs. These results provide (i) a natural way to generate an ever-changing dynamical architecture in post-main-sequence planetary systems, (ii) an avenue for planets to achieve temporary close-in orbits that are potentially detectable by transit photometry and (iii) a dynamical explanation for how residual asteroids might pollute particularly old WDs.

Causal discovery in the geosciences-Using synthetic data to learn how to interpret results

NASA Astrophysics Data System (ADS)

Ebert-Uphoff, Imme; Deng, Yi

2017-02-01

Causal discovery algorithms based on probabilistic graphical models have recently emerged in geoscience applications for the identification and visualization of dynamical processes. The key idea is to learn the structure of a graphical model from observed spatio-temporal data, thus finding pathways of interactions in the observed physical system. Studying those pathways allows geoscientists to learn subtle details about the underlying dynamical mechanisms governing our planet. Initial studies using this approach on real-world atmospheric data have shown great potential for scientific discovery. However, in these initial studies no ground truth was available, so that the resulting graphs have been evaluated only by whether a domain expert thinks they seemed physically plausible. The lack of ground truth is a typical problem when using causal discovery in the geosciences. Furthermore, while most of the connections found by this method match domain knowledge, we encountered one type of connection for which no explanation was found. To address both of these issues we developed a simulation framework that generates synthetic data of typical atmospheric processes (advection and diffusion). Applying the causal discovery algorithm to the synthetic data allowed us (1) to develop a better understanding of how these physical processes appear in the resulting connectivity graphs, and thus how to better interpret such connectivity graphs when obtained from real-world data; (2) to solve the mystery of the previously unexplained connections.

Influence of stellar multiplicity on planet formation. II. Planets are less common in multiple-star systems with separations smaller than 1500 AU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ji; Fischer, Debra A.; Xie, Ji-Wei

2014-08-20

Almost half of the stellar systems in the solar neighborhood are made up of multiple stars. In multiple-star systems, planet formation is under the dynamical influence of stellar companions, and the planet occurrence rate is expected to be different from that of single stars. There have been numerous studies on the planet occurrence rate of single star systems. However, to fully understand planet formation, the planet occurrence rate in multiple-star systems needs to be addressed. In this work, we infer the planet occurrence rate in multiple-star systems by measuring the stellar multiplicity rate for planet host stars. For a subsamplemore » of 56 Kepler planet host stars, we use adaptive optics (AO) imaging and the radial velocity (RV) technique to search for stellar companions. The combination of these two techniques results in high search completeness for stellar companions. We detect 59 visual stellar companions to 25 planet host stars with AO data. Three stellar companions are within 2'' and 27 within 6''. We also detect two possible stellar companions (KOI 5 and KOI 69) showing long-term RV acceleration. After correcting for a bias against planet detection in multiple-star systems due to flux contamination, we find that planet formation is suppressed in multiple-star systems with separations smaller than 1500 AU. Specifically, we find that compared to single star systems, planets in multiple-star systems occur 4.5 ± 3.2, 2.6 ± 1.0, and 1.7 ± 0.5 times less frequently when a stellar companion is present at a distance of 10, 100, and 1000 AU, respectively. This conclusion applies only to circumstellar planets; the planet occurrence rate for circumbinary planets requires further investigation.« less

Headlines: Planet Earth: Improving Climate Literacy with Short Format News Videos

NASA Astrophysics Data System (ADS)

Tenenbaum, L. F.; Kulikov, A.; Jackson, R.

2012-12-01

One of the challenges of communicating climate science is the sense that climate change is remote and unconnected to daily life--something that's happening to someone else or in the future. To help face this challenge, NASA's Global Climate Change website http://climate.nasa.gov has launched a new video series, "Headlines: Planet Earth," which focuses on current climate news events. This rapid-response video series uses 3D video visualization technology combined with real-time satellite data and images, to throw a spotlight on real-world events.. The "Headlines: Planet Earth" news video products will be deployed frequently, ensuring timeliness. NASA's Global Climate Change Website makes extensive use of interactive media, immersive visualizations, ground-based and remote images, narrated and time-lapse videos, time-series animations, and real-time scientific data, plus maps and user-friendly graphics that make the scientific content both accessible and engaging to the public. The site has also won two consecutive Webby Awards for Best Science Website. Connecting climate science to current real-world events will contribute to improving climate literacy by making climate science relevant to everyday life.

Do habitable worlds require magnetic fields?

NASA Astrophysics Data System (ADS)

Brain, D. A.; Egan, H. L.; Ma, Y. J.; Jarvinen, R.; Jakosky, B. M.; Moore, T. E.; Garcia-Sage, K.

2017-12-01

Of the three terrestrial worlds that have significant atmospheres (Venus, Earth, and Mars), only Earth also possesses a global dynamo magnetic field. This magnetic field is often thought to have shielded the planet from the impinging solar wind, preventing the atmosphere from being stripped away to space. The atmospheres of Mars and Venus, by contrast, are thought to have escaped to space or been dessicated (respectively) due at least in part to their planet's lack of global magnetic field. The assumption that global scale magnetic fields are a necessary requirement for surface habitability is widely used both in the planetary and exoplanetary communities, but this assumption has been called into question in recent years based both on theoretical arguments and on observations returned by spacecraft. Here we summarize the arguments "for" and "against" the importance of magnetic fields for planetary habitability, and review the observations that teach us about the role of magnetic fields. We then identify several ongoing efforts and likely fruitful avenues for determining whether a dynamo field is necessary for life to be possible at a planet's surface.

Habitability of super-Earth planets around other suns: models including Red Giant Branch evolution.

PubMed

von Bloh, W; Cuntz, M; Schröder, K-P; Bounama, C; Franck, S

2009-01-01

The unexpected diversity of exoplanets includes a growing number of super-Earth planets, i.e., exoplanets with masses of up to several Earth masses and a similar chemical and mineralogical composition as Earth. We present a thermal evolution model for a 10 Earth-mass planet orbiting a star like the Sun. Our model is based on the integrated system approach, which describes the photosynthetic biomass production and takes into account a variety of climatological, biogeochemical, and geodynamical processes. This allows us to identify a so-called photosynthesis-sustaining habitable zone (pHZ), as determined by the limits of biological productivity on the planetary surface. Our model considers solar evolution during the main-sequence stage and along the Red Giant Branch as described by the most recent solar model. We obtain a large set of solutions consistent with the principal possibility of life. The highest likelihood of habitability is found for "water worlds." Only mass-rich water worlds are able to realize pHZ-type habitability beyond the stellar main sequence on the Red Giant Branch.

Properties of the single Jovian planet population and the pursuit of Solar system analogues

NASA Astrophysics Data System (ADS)

Agnew, Matthew T.; Maddison, Sarah T.; Horner, Jonathan

2018-07-01

While the number of exoplanets discovered continues to increase at a rapid rate, we are still to discover any system that truly resembles the Solar system. Existing and near future surveys will likely continue this trend of rapid discovery. To see if these systems are Solar system analogues, we will need to efficiently allocate resources to carry out intensive follow-up observations. We seek to uncover the properties and trends across systems that indicate how much of the habitable zone is stable in each system to provide focus for planet hunters. We study the dynamics of all known single Jovian planetary systems to assess the dynamical stability of the habitable zone around their host stars. We perform a suite of simulations of all systems where the Jovian planet will interact gravitationally with the habitable zone, and broadly classify these systems. Besides the system's mass ratio (Mpl/Mstar), the Jovian planet's semimajor axis (apl), and eccentricity (epl), we find that there are no underlying system properties which are observable that indicate the potential for planets to survive within the system's habitable zone. We use Mpl/Mstar, apl, and epl to generate a parameter space over which the unstable systems cluster, thus allowing us to predict which systems to exclude from future observational or numerical searches for habitable exoplanets. We also provide a candidate list of 20 systems that have completely stable habitable zones and Jovian planets orbiting beyond the habitable zone as potential first-order Solar system analogues.

Properties of the single Jovian planet population and the pursuit of Solar system analogues

NASA Astrophysics Data System (ADS)

Agnew, Matthew T.; Maddison, Sarah T.; Horner, Jonathan

2018-04-01

While the number of exoplanets discovered continues to increase at a rapid rate, we are still to discover any system that truly resembles the Solar system. Existing and near future surveys will likely continue this trend of rapid discovery. To see if these systems are Solar system analogues, we will need to efficiently allocate resources to carry out intensive follow-up observations. We seek to uncover the properties and trends across systems that indicate how much of the habitable zone is stable in each system to provide focus for planet hunters. We study the dynamics of all known single Jovian planetary systems, to assess the dynamical stability of the habitable zone around their host stars. We perform a suite of simulations of all systems where the Jovian planet will interact gravitationally with the habitable zone, and broadly classify these systems. Besides the system's mass ratio (Mpl/Mstar), and the Jovian planet's semi-major axis (apl) and eccentricity (epl), we find that there are no underlying system properties which are observable that indicate the potential for planets to survive within the system's habitable zone. We use Mpl/Mstar, apl and epl to generate a parameter space over which the unstable systems cluster, thus allowing us to predict which systems to exclude from future observational or numerical searches for habitable exoplanets. We also provide a candidate list of 20 systems that have completely stable habitable zones and Jovian planets orbiting beyond the habitable zone as potential first order Solar system analogues.

Characterizing the Variable Dust Permeability of Planet-induced Gaps

NASA Astrophysics Data System (ADS)

Weber, Philipp; Benítez-Llambay, Pablo; Gressel, Oliver; Krapp, Leonardo; Pessah, Martin E.

2018-02-01

Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can significantly alter the dust dynamics. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle size for retention outside a gap as a function of particle size, as well as various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet’s orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains—potentially limiting the accretion of solids onto forming terrestrial planets.

Low mass planet migration in magnetically torqued dead zones - I. Static migration torque

NASA Astrophysics Data System (ADS)

McNally, Colin P.; Nelson, Richard P.; Paardekooper, Sijme-Jan; Gressel, Oliver; Lyra, Wladimir

2017-12-01

Motivated by models suggesting that the inner planet forming regions of protoplanetary discs are predominantly lacking in viscosity-inducing turbulence, and are possibly threaded by Hall-effect generated large-scale horizontal magnetic fields, we examine the dynamics of the corotation region of a low-mass planet in such an environment. The corotation torque in an inviscid, isothermal, dead zone ought to saturate, with the libration region becoming both symmetrical and of a uniform vortensity, leading to fast inward migration driven by the Lindblad torques alone. However, in such a low viscosity situation, the material on librating streamlines essentially preserves its vortensity. If there is relative radial motion between the disc gas and the planet, the librating streamlines will no longer be symmetrical. Hence, if the gas is torqued by a large-scale magnetic field so that it undergoes a net inflow or outflow past the planet, driving evolution of the vortensity and inducing asymmetry of the corotation region, the corotation torque can grow, leading to a positive torque. In this paper, we treat this effect by applying a symmetry argument to the previously studied case of a migrating planet in an inviscid disc. Our results show that the corotation torque due to a laminar Hall-induced magnetic field in a dead zone behaves quite differently from that studied previously for a viscous disc. Furthermore, the magnetic field induced corotation torque and the dynamical corotation torque in a low viscosity disc can be regarded as one unified effect.

Dynamical Analysis of the Circumprimary Planet in the Eccentric Binary System HD 59686

NASA Astrophysics Data System (ADS)

Trifonov, Trifon; Lee, Man Hoi; Reffert, Sabine; Quirrenbach, Andreas

2018-04-01

We present a detailed orbital and stability analysis of the HD 59686 binary-star planet system. HD 59686 is a single-lined, moderately close (a B = 13.6 au) eccentric (e B = 0.73) binary, where the primary is an evolved K giant with mass M = 1.9 M ⊙ and the secondary is a star with a minimum mass of m B = 0.53 M ⊙. Additionally, on the basis of precise radial velocity (RV) data, a Jovian planet with a minimum mass of m p = 7 M Jup, orbiting the primary on a nearly circular S-type orbit with e p = 0.05 and a p = 1.09 au, has recently been announced. We investigate large sets of orbital fits consistent with HD 59686's RV data by applying bootstrap and systematic grid search techniques coupled with self-consistent dynamical fitting. We perform long-term dynamical integrations of these fits to constrain the permitted orbital configurations. We find that if the binary and the planet in this system have prograde and aligned coplanar orbits, there are narrow regions of stable orbital solutions locked in a secular apsidal alignment with the angle between the periapses, Δω, librating about 0°. We also test a large number of mutually inclined dynamical models in an attempt to constrain the three-dimensional orbital architecture. We find that for nearly coplanar and retrograde orbits with mutual inclination 145° ≲ Δi ≤ 180°, the system is fully stable for a large range of orbital solutions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antonini, Fabio; Lithwick, Yoram; Hamers, Adrian S.

Gas giants orbiting their host star within the ice line are thought to have migrated to their current locations from farther out. Here we consider the origin and dynamical evolution of observed Jupiters, focusing on hot and warm Jupiters with outer friends. We show that the majority of the observed Jupiter pairs (20 out of 24) are dynamically unstable if the inner planet is placed at ≳1 au distance from the stellar host. This finding is at odds with formation theories that invoke the migration of such planets from semimajor axes ≳1 au due to secular dynamical processes (e.g., secularmore » chaos, Lidov–Kozai [LK] oscillations) coupled with tidal dissipation. In fact, the results of N -body integrations show that the evolution of dynamically unstable systems does not lead to tidal migration but rather to planet ejections and collisions with the host star. This and other arguments lead us to suggest that most of the observed planets with a companion could not have been transported from farther out through secular migration processes. More generally, by using a combination of numerical and analytic techniques, we show that the high- e LK migration scenario can only account for less than 10% of all gas giants observed between 0.1 and 1 au. Simulations of multiplanet systems support this result. Our study indicates that rather than starting on highly eccentric orbits with orbital periods above 1 yr, these “warm” Jupiters are more likely to have reached the region where they are observed today without having experienced significant tidal dissipation.« less

Terrestrial planet formation.

PubMed

Righter, K; O'Brien, D P

2011-11-29

Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (~10(6) y), followed by planetesimals to embryos (lunar to Mars-sized objects; few 10(6) y), and finally embryos to planets (10(7)-10(8) y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids.

Terrestrial planet formation

PubMed Central

Righter, K.; O’Brien, D. P.

2011-01-01

Advances in our understanding of terrestrial planet formation have come from a multidisciplinary approach. Studies of the ages and compositions of primitive meteorites with compositions similar to the Sun have helped to constrain the nature of the building blocks of planets. This information helps to guide numerical models for the three stages of planet formation from dust to planetesimals (∼106 y), followed by planetesimals to embryos (lunar to Mars-sized objects; few × 106 y), and finally embryos to planets (107–108 y). Defining the role of turbulence in the early nebula is a key to understanding the growth of solids larger than meter size. The initiation of runaway growth of embryos from planetesimals ultimately leads to the growth of large terrestrial planets via large impacts. Dynamical models can produce inner Solar System configurations that closely resemble our Solar System, especially when the orbital effects of large planets (Jupiter and Saturn) and damping mechanisms, such as gas drag, are included. Experimental studies of terrestrial planet interiors provide additional constraints on the conditions of differentiation and, therefore, origin. A more complete understanding of terrestrial planet formation might be possible via a combination of chemical and physical modeling, as well as obtaining samples and new geophysical data from other planets (Venus, Mars, or Mercury) and asteroids. PMID:21709256

The same frequency of planets inside and outside open clusters of stars.

PubMed

Meibom, Søren; Torres, Guillermo; Fressin, Francois; Latham, David W; Rowe, Jason F; Ciardi, David R; Bryson, Steven T; Rogers, Leslie A; Henze, Christopher E; Janes, Kenneth; Barnes, Sydney A; Marcy, Geoffrey W; Isaacson, Howard; Fischer, Debra A; Howell, Steve B; Horch, Elliott P; Jenkins, Jon M; Schuler, Simon C; Crepp, Justin

2013-07-04

Most stars and their planets form in open clusters. Over 95 per cent of such clusters have stellar densities too low (less than a hundred stars per cubic parsec) to withstand internal and external dynamical stresses and fall apart within a few hundred million years. Older open clusters have survived by virtue of being richer and denser in stars (1,000 to 10,000 per cubic parsec) when they formed. Such clusters represent a stellar environment very different from the birthplace of the Sun and other planet-hosting field stars. So far more than 800 planets have been found around Sun-like stars in the field. The field planets are usually the size of Neptune or smaller. In contrast, only four planets have been found orbiting stars in open clusters, all with masses similar to or greater than that of Jupiter. Here we report observations of the transits of two Sun-like stars by planets smaller than Neptune in the billion-year-old open cluster NGC6811. This demonstrates that small planets can form and survive in a dense cluster environment, and implies that the frequency and properties of planets in open clusters are consistent with those of planets around field stars in the Galaxy.

The Ice Worlds Partnership Takes Planetarium Audiences to our Polar Regions and Beyond

NASA Astrophysics Data System (ADS)

Schloss, A.; Sumners, C.; Reiff, P.

2008-12-01

The modern planetarium is an immersive full-dome theater that can take audiences to Polar Regions in the past, present, and future and can simulate dynamic polar events. The Ice Worlds show was produced for the International Polar Year by a collaborative effort led by the University of New Hampshire in partnership with the Houston Museum of Natural Science and Evans & Sutherland, and funded by the National Science Foundation. Ice Worlds uses an innovative mix of data, satellite imagery, actual footage in the field and animated scenes to tell the story of ice on Earth. Planetariums are extending their traditional space science content with Earth science topics: a move facilitated by the revolution in full-dome immersive video and techniques for capturing high-resolution still and video images. Ice Worlds appeals to planetarium audiences by also comparing Earth to other icy planets in our solar system. Ice Worlds presented several challenges: how to make a show about ice interesting and informative, how to include new research findings in the show without dating it, how to make the show appropriate for planetariums and suitable for use in school programs, and most critical - how to produce the entire show from initial concept to final cut in nine months. This paper describes the steps in producing Ice Worlds from concept to final product, and describes supporting materials designed to support education and outreach in the fast-growing portable dome (Discovery Dome) arena. We will show clips from the show. If space permits, we will show the show in fulldome in a portable dome system.

Dynamical Studies of N-Body Gravity and Tidal Dissipation in the TRAPPIST-1 Star System

NASA Astrophysics Data System (ADS)

Nayak, Michael; Kuettel, Donald H.; Stebler, Shane T.; Udrea, Bogdan

2018-01-01

To date, we have discovered a total of 2,729 planetary systems that contain more than 3,639 known exoplanets [1]. A majority of these are defined as compact systems, containing multiple exoplanets within 0.25 AU of the central star. It has been shown that tightly packed exoplanets avoid colliding due to long-term resonance-induced orbit stability [2]. However, due to extreme proximity, these planets experience intense gravitational forces from each other that are unprecedented within our own solar system, which makes the existence of exomoons doubtful. We present the results of an initial study evaluating dynamical stability of potential exomoons within such highly compact systems.This work is baselined around TRAPPIST-1, an ultra-cool dwarf star that hosts seven temperate terrestrial planets, three of which are in the habitable zone, orbiting within 0.06 AU [3]. N-body simulations place a grid of test particles varying semi-major axis, eccentricity, and inclination around the three habitable zone planets. We find that most exomoons with semi-major axes less than half the Hill sphere of their respective planet are stable over 10 kyrs, with several stable over 300 kyrs.However, in compact systems, tidal influences from other planets can compete with tidal effects from the primary planet, resulting in possible instabilities and massive amounts of tidal dissipation. We investigate these effects with a large grid search that incorporates exomoon radius, tidal quality factor and a range of planet rigidities. Results of simulations that combine n-body gravity effects with both planetary and satellite tides are presented and contrasted with n-body results. Finally, we examine long-term stability (> 1Myrs) of the stable subset of test particles from the n-body simulation with the addition of tidal dissipation, to determine if exomoons can survive around planets e, f, and g in the TRAPPIST-1 system.[1] Schneider (2017). The Extrasolar Planets Encyclopedia. http://exoplanet.eu/catalog/.[2] Tamayo et al (2017). Convergent Migration Renders TRAPPIST-1 Long-lived. ApJL, 840(2), L19.[3] Gillon et al (2016). Temperate Earth-sized planets transiting a nearby ultracool dwarf star. Nature, 533 (7602), 221-224.

Towards The Exo-Earth Era

NASA Astrophysics Data System (ADS)

Horner, J.

2017-09-01

In the past few years, the number of planets discovered orbiting other stars has grown dramatically, and newly discovered planets are now announced on an almost daily basis. In this presentation, I will describe how simulations of the orbital evolution of such planets can help us to better constrain their orbits, and even allow us to identify systems that are not all they seem to be. In addition, in coming years it is likely that the first truly Earth-like exoplanets will be discovered, and I will describe how those same dynamical tools will prove vital in assessing which of those planets are the most promising targets in the search for life beyond the Solar system.

Design and Performance of the Terrestrial Planet Finder Coronagraph

NASA Technical Reports Server (NTRS)

White, Mary L.; Shaklan, Stuart; Lisman, P. Doulas; Ho, Timothy; Mouroulis, Pantazis; Basinger, Scott; Ledeboer, Bill; Kwack, Eug; Kissil, Andy; Mosier, Gary;

Planets around pulsars - Implications for planetary formation

NASA Technical Reports Server (NTRS)

Bodenheimer, Peter

1993-01-01

Data on planets around pulsars are summarized, and different models intended to explain the formation mechanism are described. Both theoretical and observational evidence suggest that very special circumstances are required for the formation of planetary systems around pulsars, namely, the prior presence of a millisecond pulsar with a close binary companion, probably a low mass main-sequence star. It is concluded that the discovery of two planets around PSR 1257+12 is important for better understanding the problems of dynamics and stellar evolution. The process of planetary formation should be learned through intensive studies of the properties of disks near young objects and application of techniques for detection of planets around main-sequence solar-type stars.

Stable habitable zones of single Jovian planet systems

NASA Astrophysics Data System (ADS)

Agnew, Matthew T.; Maddison, Sarah T.; Thilliez, Elodie; Horner, Jonathan

2017-11-01

With continued improvement in telescope sensitivity and observational techniques, the search for rocky planets in stellar habitable zones is entering an exciting era. With so many exoplanetary systems available for follow-up observations to find potentially habitable planets, one needs to prioritize the ever-growing list of candidates. We aim to determine which of the known planetary systems are dynamically capable of hosting rocky planets in their habitable zones, with the goal of helping to focus future planet search programmes. We perform an extensive suite of numerical simulations to identify regions in the habitable zones of single Jovian planet systems where Earth-mass planets could maintain stable orbits, specifically focusing on the systems in the Catalog of Earth-like Exoplanet Survey Targets (CELESTA). We find that small, Earth-mass planets can maintain stable orbits in cases where the habitable zone is largely, or partially, unperturbed by a nearby Jovian, and that mutual gravitational interactions and resonant mechanisms are capable of producing stable orbits even in habitable zones that are significantly or completely disrupted by a Jovian. Our results yield a list of 13 single Jovian planet systems in CELESTA that are not only capable of supporting an Earth-mass planet on stable orbits in their habitable zone, but for which we are also able to constrain the orbits of the Earth-mass planet such that the induced radial velocity signals would be detectable with next generation instruments.

The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

NASA Astrophysics Data System (ADS)

Ramm, D. J.; Nelson, B. E.; Endl, M.; Hearnshaw, J. B.; Wittenmyer, R. A.; Gunn, F.; Bergmann, C.; Kilmartin, P.; Brogt, E.

2016-08-01

We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary ν Octantis (K1 III/IV). This system (a_{bin} ˜ 2.6 au, P ˜ 1050 d) is conjectured to have a Jovian planet with a semimajor axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P ˜ 415 d) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on cross-correlation function bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 yr. The sensitive orbital dynamics allow us to constrain the 3D architecture with a broad prior probability distribution on the mutual inclination, which with posterior samples obtained from an N-body Markov chain Monte Carlo is found to be 152.5°±^{0.7}_{0.6}. None of these samples are dynamically stable beyond 106 yr. However, a grid search around the best-fitting solution finds a region that has many models stable for 107 yr, and includes one model within 1σ that is stable for at least 108 yr. The planet's exceptional nature demands robust independent verification and makes the theoretical understanding of its formation a worthy challenge.

DYNAMICS AND ECCENTRICITY FORMATION OF PLANETS IN OGLE-06-109L SYSTEM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Su; Zhao Gang; Zhou Jilin, E-mail: zhoujl@nju.edu.c

2009-11-20

Recent observation of the microlensing technique reveals two giant planets at 2.3 AU and 4.6 AU around the star OGLE-06-109L. The eccentricity of the outer planet (e{sub c} ) is estimated to be 0.11{sup +0.17}{sub -0.04}, comparable to that of Saturn (0.01-0.09). The similarities between the OGLE-06-109L system and the solar system indicate that they may have passed through similar histories during their formation stage. In this paper, we investigate the dynamics and formation of the orbital architecture in the OGLE-06-109L system. For the present two planets with their nominal locations, the secular motions are stable as long as theirmore » eccentricities (e{sub b} , e{sub c} ) fulfill e {sup 2} {sub b} + e {sup 2} {sub c} <= 0.3{sup 2}. Earth-size bodies might be formed and are stable in the habitable zone (0.25-0.36 AU) of the system. Three possible scenarios may be accounted for the formation of e{sub b} and e{sub c} : (1) convergent migration of two planets and the 3:1 mean motion resonance (MMR) trapping; (2) planetary scattering; and (3) divergent migration and the 3:1 MMR crossing. As we showed that the probability for the two giant planets in 3:1 MMR is low (approx3%), scenario (1) is less likely. According to models (2) and (3), the final eccentricity of inner planet (e{sub b} ) may oscillate between [0-0.06], comparable to that of Jupiter (0.03-0.06). An inspection of e{sub b} , e{sub c} 's secular motion may be helpful to understand which model is really responsible for the eccentricity formation.« less

The Kepler-19 System: A Thick-envelope Super-Earth with Two Neptune-mass Companions Characterized Using Radial Velocities and Transit Timing Variations

NASA Astrophysics Data System (ADS)

Malavolta, Luca; Borsato, Luca; Granata, Valentina; Piotto, Giampaolo; Lopez, Eric; Vanderburg, Andrew; Figueira, Pedro; Mortier, Annelies; Nascimbeni, Valerio; Affer, Laura; Bonomo, Aldo S.; Bouchy, Francois; Buchhave, Lars A.; Charbonneau, David; Collier Cameron, Andrew; Cosentino, Rosario; Dressing, Courtney D.; Dumusque, Xavier; Fiorenzano, Aldo F. M.; Harutyunyan, Avet; Haywood, Raphaëlle D.; Johnson, John Asher; Latham, David W.; Lopez-Morales, Mercedes; Lovis, Christophe; Mayor, Michel; Micela, Giusi; Molinari, Emilio; Motalebi, Fatemeh; Pepe, Francesco; Phillips, David F.; Pollacco, Don; Queloz, Didier; Rice, Ken; Sasselov, Dimitar; Ségransan, Damien; Sozzetti, Alessandro; Udry, Stéphane; Watson, Chris

2017-05-01

We report a detailed characterization of the Kepler-19 system. This star was previously known to host a transiting planet with a period of 9.29 days, a radius of 2.2 R ⊕, and an upper limit on the mass of 20 M ⊕. The presence of a second, non-transiting planet was inferred from the transit time variations (TTVs) of Kepler-19b over eight quarters of Kepler photometry, although neither the mass nor period could be determined. By combining new TTVs measurements from all the Kepler quarters and 91 high-precision radial velocities obtained with the HARPS-N spectrograph, using dynamical simulations we obtained a mass of 8.4 ± 1.6 M ⊕ for Kepler-19b. From the same data, assuming system coplanarity, we determined an orbital period of 28.7 days and a mass of 13.1 ± 2.7 M ⊕ for Kepler-19c and discovered a Neptune-like planet with a mass of 20.3 ± 3.4 M ⊕ on a 63-day orbit. By comparing dynamical simulations with non-interacting Keplerian orbits, we concluded that neglecting interactions between planets may lead to systematic errors that can hamper the precision in the orbital parameters when the data set spans several years. With a density of 4.32 ± 0.87 g cm-3 (0.78 ± 0.16 ρ ⊕) Kepler-19b belongs to the group of planets with a rocky core and a significant fraction of volatiles, in opposition to low-density planets characterized only by transit time variations and an increasing number of rocky planets with Earth-like density. Kepler-19 joins the small number of systems that reconcile transit timing variation and radial velocity measurements.

Toward a Deterministic Model of Planetary Formation. I. A Desert in the Mass and Semimajor Axis Distributions of Extrasolar Planets

NASA Astrophysics Data System (ADS)

Ida, S.; Lin, D. N. C.

2004-03-01

In an attempt to develop a deterministic theory for planet formation, we examine the accretion of cores of giant planets from planetesimals, gas accretion onto the cores, and their orbital migration. We adopt a working model for nascent protostellar disks with a wide variety of surface density distributions in order to explore the range of diversity among extrasolar planetary systems. We evaluate the cores' mass growth rate Mc through runaway planetesimal accretion and oligarchic growth. The accretion rate of cores is estimated with a two-body approximation. In the inner regions of disks, the cores' eccentricity is effectively damped by their tidal interaction with the ambient disk gas and their early growth is stalled by ``isolation.'' In the outer regions, the cores' growth rate is much smaller. If some cores can acquire more mass than a critical value of several Earth masses during the persistence of the disk gas, they would be able to rapidly accrete gas and evolve into gas giant planets. The gas accretion process is initially regulated by the Kelvin-Helmholtz contraction of the planets' gas envelope. Based on the assumption that the exponential decay of the disk gas mass occurs on the timescales ~106-107 yr and that the disk mass distribution is comparable to those inferred from the observations of circumstellar disks of T Tauri stars, we carry out simulations to predict the distributions of masses and semimajor axes of extrasolar planets. In disks as massive as the minimum-mass disk for the solar system, gas giants can form only slightly outside the ``ice boundary'' at a few AU. However, cores can rapidly grow above the critical mass inside the ice boundary in protostellar disks with 5 times more heavy elements than those of the minimum-mass disk. Thereafter, these massive cores accrete gas prior to its depletion and evolve into gas giants. The limited persistence of the disk gas and the decline in the stellar gravity prevent the formation of cores capable of efficient gas accretion outside 20-30 AU. Unimpeded dynamical accretion of gas is a runaway process that is terminated when the residual gas is depleted either globally or locally in the form of a gap in the vicinity of their orbits. Since planets' masses grow rapidly from 10 to 100 M⊕, the gas giant planets rarely form with asymptotic masses in this intermediate range. Our model predicts a paucity of extrasolar planets with mass in the range 10-100 M⊕ and semimajor axis less than 3 AU. We refer to this deficit as a ``planet desert.'' We also examine the dynamical evolution of protoplanets by considering the effect of orbital migration of giant planets due to their tidal interactions with the gas disks, after they have opened up gaps in the disks. The effect of migration is to sharpen the boundaries and to enhance the contrast of the planet desert. It also clarifies the separation between the three populations of rocky, gas giant, and ice giant planets. Based on our results, we suggest that the planets' mass versus semimajor axes diagram can provide strong constraints on the dominant formation processes of planets analogous to the implications of the color-magnitude diagram on the paths of stellar evolution. We show that the mass and semimajor axis distributions generated in our simulations for the gas giants are consistent with those of the known extrasolar planets. Our results also indicate that a large fraction (90%-95%) of the planets that have migrated to within 0.05 AU must have perished. Future observations can determine the existence and the boundaries of the planet desert in this diagram, which can be used to extrapolate the ubiquity of rocky planets around nearby stars. Finally, the long-term dynamical interaction between planets of various masses can lead to both eccentricity excitation and scattering of planets to large semimajor axes. These effects are to be included in future models.

The Water Content of Exo-earths in the Habitable Zone around Low-mass Stars

NASA Astrophysics Data System (ADS)

Mulders, Gijs Dirk; Ciesla, Fred; Pascucci, Ilaria; apai, Daniel

2015-08-01

Terrestrial planets in the habitable zones of low-mass M dwarf stars have become the focus of many astronomical studies: they are more easily accessible to detection and characterization than their counterparts around sunlike stars. The habitability of these planets, however, faces a number of challenges, including inefficient or negligible water delivery during accretion. To understand the water content of planets in and around the habitable zone, simulations of the final stages of planet formation are necessary.We present detailed accretion simulations of wet and dry planetary embryos around a range of stellar masses. We focus on different pathways of delivering water from beyond the snow line to terrestrial planets in the habitable zone. We explore the impact of using either asteroid-like or comet-like bodies, and the effects of a dispersion in snow line locations. We derive the probability distribution of water abundances for terrestrial sized planets in the habitable zone.While these models predict that the bulk of terrestrial planets in the habitable zones of M stars will be dry, a small fraction receives earth-like amounts of water. Given their larger numbers and higher planet occurrence rates, this population of water-enriched worlds in the habitable zone of M stars may equal that around sun-like stars in numbers.References:Ciesla, Mulders et al. 2015Mulders et al. ApJ subm.

Development and Application of the Transit Timing Planet Detection Technique

NASA Astrophysics Data System (ADS)

Steffen, J. H.; Agol, E.

2005-12-01

We present the development and application of a new planet detection technique that uses the transit timing of a known, transiting planet. The transits of a solitary planet orbiting a star occur at equally spaced intervals in time. If a second planet is present, then dynamical interactions within the system will cause the time interval between transits to vary. These transit time variations (TTV) can be used to infer the orbital elements and mass of the unseen, perturbing planet. In some cases, particularly near mean-motion resonances, this technique could detect planets with masses less than the mass of the Earth---a capability not yet achieved by other planet detection schemes. We present an analysis of the set of transit times of the TrES-1 system given by Charbonneau et al. (2005). While no convincing evidence for a second planet in the TrES-1 system was found from that data, we constrain the mass that a perturbing planet could have as a function of the semi-major axis ratio of the two planets and the eccentricity of the perturbing planet. Near low-order, mean-motion resonances (within about 1% fractional deviation), we find that a secondary planet must generally have a mass comparable to or less than the mass of the Earth--showing that this data is the first to have sensitivity to sub Earth-mass planets. We present results from our studies that use simulated data and from an ongoing analysis of the HD209458 system. These results show that TTV will be an important tool in the detection and characterization of extrasolar planetary systems.

Spitzer Transits of New TESS Planets

NASA Astrophysics Data System (ADS)

Crossfield, Ian; Werner, Michael; Dragomir, Diana; Kreidberg, Laura; Benneke, Bjoern; Deming, Drake; Gorjian, Varoujan; Guo, Xueying; Dressing, Courtney; Yu, Liang; Kane, Stephen; Christiansen, Jessie; Berardo, David; Morales, Farisa

2018-05-01

TESS will soon begin searching the sky for new transiting planets around the nearest, brightest stars, and JWST will become the world-leading facility in exoplanet atmospheric characterization. A key TESS goal is to provide the best atmospheric targets to JWST. However, many new TESS planets will exhibit just a few transits each, so their transit ephemerides will be only weakly constrained; without additional constraints on the planet orbit, the transits will be quickly "lost" long before JWST transit spectroscopy can commence. Some TESS planets will also be good targets for JWST secondary eclipses observations, but these eclipses will be even harder to pin down from TESS data alone. Spitzer's IR sensitivity and photometric stability can identify the transits and eclipses of the most favorable TESS planets and set the stage for JWST atmospheric characterization on a large scale. We request 550 hr to use Spitzer to measure precise transits and eclipses of new planets from the first year of TESS, refining their properties and ensuring their transits and eclipses can be recovered for many years to come. We will focus on the smaller planets for which ground-based observations are impractical and for which JWST spectroscopy will have a high impact. The time baseline provided by Spitzer will pin down the ephemerides far into the future. Thus our proposed program will secure these planets for future JWST spectroscopy to reveal their atmospheric makeup, chemistry, cloud properties, and formation history in unprecedented detail.

The dynamical systems approach to numerical integration

NASA Astrophysics Data System (ADS)

Wisdom, Jack

2018-03-01

The dynamical systems approach to numerical integration is reviewed and extended. The new method is compared to some alternative methods based on the Lie series approach. The test problem is the motion of the outer planets. The algorithms developed using the dynamical systems approach perform well.

Exoplanets Clue to Sun's Curious Chemistry

NASA Astrophysics Data System (ADS)

2009-11-01

A ground-breaking census of 500 stars, 70 of which are known to host planets, has successfully linked the long-standing "lithium mystery" observed in the Sun to the presence of planetary systems. Using ESO's successful HARPS spectrograph, a team of astronomers has found that Sun-like stars that host planets have destroyed their lithium much more efficiently than "planet-free" stars. This finding does not only shed light on the lack of lithium in our star, but also provides astronomers with a very efficient way of finding stars with planetary systems. "For almost 10 years we have tried to find out what distinguishes stars with planetary systems from their barren cousins," says Garik Israelian, lead author of a paper appearing this week in the journal Nature. "We have now found that the amount of lithium in Sun-like stars depends on whether or not they have planets." Low levels of this chemical element have been noticed for decades in the Sun, as compared to other solar-like stars, and astronomers have been unable to explain the anomaly. The discovery of a trend among planet-bearing stars provides a natural explanation to this long-standing mystery. "The explanation of this 60 year-long puzzle is for us rather simple," adds Israelian. "The Sun lacks lithium because it has planets." This conclusion is based on the analysis of 500 stars, including 70 planet-hosting stars. Most of these stars were monitored for several years with ESO's High Accuracy Radial Velocity Planet Searcher. This spectrograph, better known as HARPS, is attached to ESO's 3.6-metre telescope and is the world's foremost exoplanet hunter. "This is the best possible sample available to date to understand what makes planet-bearing stars unique," says co-author Michel Mayor. The astronomers looked in particular at Sun-like stars, almost a quarter of the whole sample. They found that the majority of stars hosting planets possess less than 1% of the amount of lithium shown by most of the other stars. "Like our Sun, these stars have been very efficient at destroying the lithium they inherited at birth," says team member Nuno Santos. "Using our unique, large sample, we can also prove that the reason for this lithium reduction is not related to any other property of the star, such as its age." Unlike most other elements lighter than iron, the light nuclei of lithium, beryllium and boron are not produced in significant amounts in stars. Instead, it is thought that lithium, composed of just three protons and four neutrons, was mainly produced just after the Big Bang, 13.7 billion years ago. Most stars will thus have the same amount of lithium, unless this element has been destroyed inside the star. This result also provides the astronomers with a new, cost-effective way to search for planetary systems: by checking the amount of lithium present in a star astronomers can decide which stars are worthy of further significant observing efforts. Now that a link between the presence of planets and curiously low levels of lithium has been established, the physical mechanism behind it has to be investigated. "There are several ways in which a planet can disturb the internal motions of matter in its host star, thereby rearrange the distribution of the various chemical elements and possibly cause the destruction of lithium. It is now up to the theoreticians to figure out which one is the most likely to happen," concludes Mayor. More information This research was presented in a paper that appears in the 12 November 2009 issue of Nature (Enhanced lithium depletion in Sun-like stars with orbiting planets, by G. Israelian et al.). The team is composed of Garik Israelian, Elisa Delgado Mena, Carolina Domínguez Cerdeña, and Rafael Rebolo (Instituto de Astrofisíca de Canarias, La Laguna, Tenerife, Spain), Nuno Santos and Sergio Sousa (Centro de Astrofisica, Universidade de Porto, Portugal), Michel Mayor and Stéphane Udry (Observatoire de Genève, Switzerland), and Sofia Randich (INAF, Osservatorio di Arcetri, Firenze, Italy). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Climate variations on Earth-like circumbinary planets

PubMed Central

Popp, Max; Eggl, Siegfried

2017-01-01

The discovery of planets orbiting double stars at close distances has sparked increasing scientific interest in determining whether Earth-analogues can remain habitable in such environments and how their atmospheric dynamics is influenced by the rapidly changing insolation. In this work we present results of the first three-dimensional numerical experiments of a water-rich planet orbiting a double star. We find that the periodic forcing of the atmosphere has a noticeable impact on the planet's climate. Signatures of the forcing frequencies related to the planet's as well as to the binary's orbital periods are present in a variety of climate indicators such as temperature and precipitation, making the interpretation of potential observables challenging. However, for Earth-like greenhouse gas concentrations, the variable forcing does not change the range of insolation values allowing for habitable climates substantially. PMID:28382929

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilat-Lohinger, E.; Bazsó, A.; Funk, B.

Gravitational perturbations in multi-planet systems caused by an accompanying star are the subject of this investigation. Our dynamical model is based on the binary star HD 41004 AB where a giant planet orbits HD 41004 A. We modify the orbital parameters of this system and analyze the motion of a hypothetical test planet surrounding HD 41004 A on an interior orbit to the detected giant planet. Our numerical computations indicate perturbations due to mean motion and secular resonances (SRs). The locations of these resonances are usually connected to high eccentricity and highly inclined motion depending strongly on the binary-planet architecture.more » As the positions of mean motion resonances can easily be determined, the main purpose of this study is to present a new semi-analytical method to determine the location of an SR without huge computational effort.« less

An Upstart Web Catalog Challenges an Academic-Library Giant

ERIC Educational Resources Information Center

Foster, Andrea L.

2008-01-01

21-year-old Aaron Swartz is attempting to turn the library world upside down. He is taking on the subscription-based WorldCat, the largest bibliographic database on the planet, by building a free online book catalog that anyone can update. Many academic librarians are wary of Mr. Swartz's project because it will allow nonlibrarians, who may be…

Journey to Planet Earth: Land of Plenty, Land of Want. The Public Television Series. [Videotape].

ERIC Educational Resources Information Center

1999

This videotape gives students the opportunity to view farming practices in four distinctly different countries: Zimbabwe, France, China, and the United States. By viewing farming methods throughout the world and studying the different challenges facing the world's farmers, students will be able to appreciate the commonality of all farmers--they…

WOW! Windows on the Wild: A Biodiversity Primer.

ERIC Educational Resources Information Center

Braus, Judy, Ed.; And Others

Windows on the Wild is an environmental education program of the World Wildlife Fund. This issue of WOW! focuses on biodiversity. Topics include: an interview with one of the world's leading experts on biodiversity; the lighter side of biodiversity through comics and cartoons; a species-scape that compares the number of species on the planet;…

Teaching Significance: Keeping the Humanities Alive in a STEM-Bending World

ERIC Educational Resources Information Center

Donovan, Jill

2017-01-01

The natural world and the scientific and mathematical tools we use to explore, measure, and understand it should fill us with awe and wonder, and light all kinds of inspirational fires in us. On a planet so desperately in need of scientific breakthroughs, engineering innovations, and newborn technologies, we should be thrilled by the excitement in…

The Elementary Child's Place in the Natural World

ERIC Educational Resources Information Center

Allen, Phoebe

2013-01-01

Phoebe Allen's article speaks for the early bonding of children to the natural world prior to the elementary class. She also suggests the continuing exploration of children at elementary age in the outdoors in order to build the necessary sense of wonder and love of the environment to overcome anxiety over the negative realities of the planet's…

Leon Foucault: His Life, Times and Achievements

ERIC Educational Resources Information Center

Aczel, Amir D.

2004-01-01

Leon Foucault's dramatic demonstration of the rotation of the Earth using a freely-rotating pendulum in 1850 shocked the world of science. Scientists were stunned that such a simple proof of our planet's rotation had to wait so long to be developed. Foucault's public demonstration, which was repeated at many locations around the world, put an end…

Dynamical Simulations of HD 69830

NASA Astrophysics Data System (ADS)

Payne, Matthew J.; Ford, Eric B.; Wyatt, Mark C.; Booth, Mark

2009-02-01

Previous studies have developed models for the growth and migration of three planets orbiting HD 69830. We perform n-body simulations using MERCURY (Chambers 1999) to explore the implications of these models for: 1) the excitation of planetary orbits via planet-planet interactions, 2) the accretion and clearing of a putative planetesimal disk, 3) the distribution of planetesimal orbits following migration, and 4) the implications for the origin of the observed infrared emission from the HD 69830 system. We report preliminary results that suggest new constraints on the formation of HD 69830.

The Dynamics of Tide and Resonances in Exoplanetary Systems

NASA Astrophysics Data System (ADS)

Chen, Y. Y.

2015-05-01

In recent years, the planet formation theory and planetary system dynamics have become an important area of astronomy. With more details of exoplanets being found, many characteristics quite different from the solar system have been found in the exoplanetary systems. A large number of planets are found to be very close to their host star, and their periods are only a few days, which brings strong tidal dissipation with the star. Many period ratios of adjacent planets in multi-planetary systems are close to the simple integer ratios, which indicates that the planets are likely in the mean motion resonances (MMRs). The range of the angles between the orbital plane of the planets and the equatorial plane of their hosts expands from ≤sssim 7(°) for the planets in the solar system to 0(°) ˜ 180(°) , and some retrograde hot Jupiters exist. These new phenomena are testing out the traditional planetary formation theory and planetary system dynamics, but also provide an unprecedented opportunity for their further improvement and development. Based on these latest observational data and statistical features, the thesis investigates some special configurations combining the resonances and tidal dissipation by the way of planetary system dynamics. The thesis first reviews the primary applications and the latest progress in the tide as well as various resonances of exoplanets. Then it gives some tidal model derivations, including the classic one and most popular one, in order to understand the assumptions of the equilibrium tide. Meanwhile, the average rates of change of orbital elements under tidal dissipation are exhibited. By both numerical simulation and theoretical analysis, the following three questions are investigated: the evolution of the eccentricity of planets in the non-synchronous spin-orbit resonances, the characteristics of nearly 2:1 MMR and Laplace resonance under tidal dissipation, and the promoting role of the gravity of outer gas disk for exciting the planets in its inner cavity. Chapter 3 takes into account the tidal dissipation and the gravity from planet deformation, and concludes that, the tidal dissipation rates in all the non-synchronous spin-orbit resonances are greater than that in the quasi-stationary state of the spin of the planet, so the eccentricity is also damped within a shorter duration. In order to explain the formation of two period ratios nearly 2:1 in the three planet HD40307 system, Chapter 4 simulates the evolution paths of planets in two different situations. If the planets are always stable during and after the dissipation of gas disk, their eccentricities directly from the interaction among planets are very small (˜ 10(-4) ). So the changing timescale of period ratios is much larger than the age of the system. On the contrary, if the planets have experienced unstable phases, their eccentricities would be excited, which can accelerate the evolution of the period ratios effectively. In this situation, three paths exist to achieve the current configuration, whose initial semi-major axes respectively correspond to three different regions on the plane of two period ratios. It can be inferred that the instability stage after the dissipation of the gas disk is a necessary condition for the system to achieve the evolution from 2:1 MMRs to the current configuration under tidal dissipation with the star. Chapter 5 proposes a mechanism to reduce the critical inclination of orbital pumping, in order to explain the retrograde hot Jupiters in latest observations. Considering the gravity of the outer gas disk, a secular resonance would occur between the planets in the inner cavity if they are in appropriate positions, which pumps the mutual inclination of the planets and induces the Kozai resonance between them in some situations. Then the eccentricity and inclination of the inner planet will be excited eventually. We develop the equation of the rates of change of orbital elements under the secular perturbation in hierarchical three-body system (with respect to an arbitrary plane rather than the invariant plane of the two orbits), as well as give the rates of change of orbital elements under a 2-D disk gravity equations. Combining the two parts, the results by integrating the evolution equations are good approximation of the N-body simulations. By scanning the parameter spaces using the evolution equations, we get the preliminary critical condition for the retrograde hot Jupiters formed, and give a complete discussion of the impact of relevant parameters.

Checking the compatibility of the cold Kuiper belt with a planetary instability migration model

NASA Astrophysics Data System (ADS)

Gomes, Rodney; Nesvorný, David; Morbidelli, Alessandro; Deienno, Rogerio; Nogueira, Erica

2018-05-01

The origin of the orbital structure of the cold component of the Kuiper belt is still a hot subject of investigation. Several features of the solar system suggest that the giant planets underwent a phase of global dynamical instability, but the actual dynamical evolution of the planets during the instability is still debated. To explain the structure of the cold Kuiper belt, Nesvorny (2015, AJ 150,68) argued for a "soft" instability, during which Neptune never achieved a very eccentric orbit. Here we investigate the possibility of a more violent instability, from an initially more compact fully resonant configuration of 5 giant planets. We show that the orbital structure of the cold Kuiper belt can be reproduced quite well provided that the cold population formed in situ, with an outer edge between 44 - 45 au and never had a large mass.

A dynamical study on extrasolar comets

NASA Astrophysics Data System (ADS)

Loibnegger, B.; Dvorak, R.

2017-09-01

Since the detection of absorption features in spectra of beta Pictoris varying on short time scales it is known that comets exist in other stellar systems. We investigate the dynamics of comets in two differently build systems (HD 10180 and HIP 14810). The outcomes of the scattering process, as there are collisions with the planets, captures and ejections from the systems are analysed statistically. Collisions and close encounters with the planets are investigated in more detail in order to conclude about transport of water and organic material. We will also investigate the possibility of detection of comets in other planetary systems.

Mars

NASA Technical Reports Server (NTRS)

Kieffer, Hugh H. (Editor); Jakosky, Bruce M. (Editor); Snyder, Conway W. (Editor); Matthews, Mildred S. (Editor)

1992-01-01

The present volume on Mars discusses visual, photographic and polarimetric telescopic observations, spacecraft exploration of Mars, the origin and thermal evolution of Mars, and the bulk composition, mineralogy, and internal structure of the planet. Attention is given to Martian gravity and topography, stress and tectonics on Mars, long-term orbital and spin dynamics of Mars, and Martian geodesy and cartography. Topics addressed include the physical volcanology of Mars, the canyon system on planet, Martian channels and valley networks, and ice in the Martian regolith. Also discussed are Martian aeolian processes, sediments, and features, polar deposits of Mars, dynamics of the Martian atmosphere, and the seasonal behavior of water on Mars.

Comparing TRAPPIST-1 to the Solar System

NASA Image and Video Library

2018-02-05

This graph presents known properties of the seven TRAPPIST-1 exoplanets (labeled b through h), showing how they stack up to the inner rocky worlds in our own solar system. The horizontal axis shows the level of illumination that each planet receives from its host star. TRAPPIST-1 is a mere 9 percent the mass of our Sun, and its temperature is much cooler. But because the TRAPPIST-1 planets orbit so closely to their star, they receive comparable levels of light and heat to Earth and its neighboring planets. The vertical axis shows the densities of the planets. Density, calculated based on a planet's mass and volume, is the first important step in understanding a planet's composition. The plot shows that the TRAPPIST-1 planet densities range from being similar to Earth and Venus at the upper end, down to values comparable to Mars at the lower end. The relative sizes of the planets are indicated by the circles. The masses and densities of the TRAPPIST-1 planets were determined by careful measurements of slight variations in the timings of their orbits using extensive observations made by NASA's Spitzer and Kepler space telescopes, in combination with data from Hubble and a number of ground-based telescopes. These measurements are the most precise to date for any system of exoplanets. By comparing these measurements with theoretical models of how planets form and evolve, researchers have determined that they are all rocky in overall composition. Estimates suggest the lower-density planets could have large quantities of water -- as much as 5 percent by mass for TRAPPIST-1d. Earth, in comparison, has only about 0.02 percent of its mass in the form of water. https://photojournal.jpl.nasa.gov/catalog/PIA22095

32 New Exoplanets Found

NASA Astrophysics Data System (ADS)

2009-10-01

oday, at an international ESO/CAUP exoplanet conference in Porto, the team who built the High Accuracy Radial Velocity Planet Searcher, better known as HARPS, the spectrograph for ESO's 3.6-metre telescope, reports on the incredible discovery of some 32 new exoplanets, cementing HARPS's position as the world's foremost exoplanet hunter. This result also increases the number of known low-mass planets by an impressive 30%. Over the past five years HARPS has spotted more than 75 of the roughly 400 or so exoplanets now known. "HARPS is a unique, extremely high precision instrument that is ideal for discovering alien worlds," says Stéphane Udry, who made the announcement. "We have now completed our initial five-year programme, which has succeeded well beyond our expectations." The latest batch of exoplanets announced today comprises no less than 32 new discoveries. Including these new results, data from HARPS have led to the discovery of more than 75 exoplanets in 30 different planetary systems. In particular, thanks to its amazing precision, the search for small planets, those with a mass of a few times that of the Earth - known as super-Earths and Neptune-like planets - has been given a dramatic boost. HARPS has facilitated the discovery of 24 of the 28 planets known with masses below 20 Earth masses. As with the previously detected super-Earths, most of the new low-mass candidates reside in multi-planet systems, with up to five planets per system. In 1999, ESO launched a call for opportunities to build a high resolution, extremely precise spectrograph for the ESO 3.6-metre telescope at La Silla, Chile. Michel Mayor, from the Geneva Observatory, led a consortium to build HARPS, which was installed in 2003 and was soon able to measure the back-and-forward motions of stars by detecting small changes in a star's radial velocity - as small as 3.5 km/hour, a steady walking pace. Such a precision is crucial for the discovery of exoplanets and the radial velocity method, which detects small changes in the radial velocity of a star as it wobbles slightly under the gentle gravitational pull from an (unseen) exoplanet, has been most prolific method in the search for exoplanets. In return for building the instrument, the HARPS consortium was granted 100 observing nights per year during a five-year period to carry out one of the most ambitious systematic searches for exoplanets so far implemented worldwide by repeatedly measuring the radial velocities of hundreds of stars that may harbour planetary systems. The programme soon proved very successful. Using HARPS, Mayor's team discovered - among others - in 2004, the first super-Earth (around µ Ara; in 2006, the trio of Neptunes around HD 69830; in 2007, Gliese 581d, the first super Earth in the habitable zone of a small star (eso0722); and in 2009, the lightest exoplanet so far detected around a normal star, Gliese 581e (eso0915). More recently, they found a potentially lava-covered world, with density similar to that of the Earth's (eso0933). "These observations have given astronomers a great insight into the diversity of planetary systems and help us understand how they can form," says team member Nuno Santos. The HARPS consortium was very careful in their selection of targets, with several sub-programmes aimed at looking for planets around solar-like stars, low-mass dwarf stars, or stars with a lower metal content than the Sun. The number of exoplanets known around low-mass stars - so-called M dwarfs - has also dramatically increased, including a handful of super Earths and a few giant planets challenging planetary formation theory. "By targeting M dwarfs and harnessing the precision of HARPS we have been able to search for exoplanets in the mass and temperature regime of super-Earths, some even close to or inside the habitable zone around the star," says co-author Xavier Bonfils. The team found three candidate exoplanets around stars that are metal-deficient. Such stars are thought to be less favourable for the formation of planets, which form in the metal-rich disc around the young star. However, planets up to several Jupiter masses have been found orbiting metal-deficient stars, setting an important constraint for planet formation models. Although the first phase of the observing programme is now officially concluded, the team will pursue their effort with two ESO Large Programmes looking for super-Earths around solar-type stars and M dwarfs and some new announcements are already foreseen in the coming months, based on the last five years of measurements. There is no doubt that HARPS will continue to lead the field of exoplanet discoveries, especially pushing towards the detection of Earth-type planets. More information This discovery was announced today at the ESO/CAUP conference "Towards Other Earths: perspectives and limitations in the ELT era", taking place in Porto, Portugal, on 19-23 October 2009. This conference discusses the new generation of instruments and telescopes that is now being conceived and built by different teams around the world to allow the discovery of other Earths, especially for the European Extremely Large Telescope (E-ELT). The new planets are simultaneously presented by Michel Mayor at the international symposium "Heirs of Galileo: Frontiers of Astronomy" in Madrid, Spain. This research was presented in a series of eight papers submitted - or soon to be submitted - to the Astronomy and Astrophysics journal. The team is composed of * Geneva Observatory: M. Mayor, S. Udry, D. Queloz, F. Pepe, C. Lovis, D. Ségransan, X. Bonfils * LAOG Grenoble: X. Delfosse, T. Forveille, X. Bonfils, C. Perrier * CAUP Porto: N.C. Santos * ESO: G. Lo Curto, D. Naef * University of Bern: W. Benz, C. Mordasini * IAP Paris: F. Bouchy, G. Hébrard * LAM Marseille: C. Moutou * Service d'aéronomie, Paris: J.-L. Bertaux ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky". * The web page of the conference "Towards Other Earths: perspectives and limitations in the ELT era" is at http://www.astro.up.pt/investigacao/conferencias/toe2009/

Characterising Hot-Jupiters' atmospheres with observations and modelling

NASA Astrophysics Data System (ADS)

Tinetti, G.

2007-08-01

Exoplanet transit photometry and spectroscopy are currently the best techniques to probe the atmospheres of extrasolar worlds. The best targets to be observed with these methods, are the planets that orbit very close to their parent star, both because their probability to transit grows and their atmospheres are warmer and more expanded, hence easier to probe. These characteristics are met by the so called Hot-Jupiters, massive low-density gaseous planets orbiting very close-in. Phase-curves allow to observe the change in brightness in the combined light of the planet-star system, also for non-transiting exoplanets. We review here the most crucial observations performed with the Hubble and Spitzer Space Telescopes at multiple wavelenghts, and the most successful models proposed in the literature to plan and interpret those observations. In particular we will focus on most recent observations and modelling claiming the detection of water vapour in the atmospheres of these planets. Further into the future, the JamesWebb Space Telescope will allow to probe the atmospheres of smaller size-planets with the same techniques. We briefly report here the results expected for hot and warm Neptunes, or transiting terrestrial planets.

Stability Analysis of the Planetary System Orbiting Upsilon Andromedae. 2; Simulations Using New Lick Observatory Fits

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Rivera, Eugenio J.; DeVincenzi, Donald (Technical Monitor)

2001-01-01

We present results of long-term numerical orbital integrations designed to test the stability of the three-planet system orbiting upsilon Andromedae and short-term integrations to test whether mutual perturbations among the planets can be used to determine planetary masses. Our initial conditions are based on recent fits to the radial velocity data obtained by the planet search group at Lick Observatory. The new fits result in significantly more stable systems than did the initially announced planetary parameters. Our integrations using the 2000 February parameters show that if the system is nearly planar, then it is stable for at least 100 Myr for m(sub f) = 1/sin i less than or = 4. In some stable systems, the eccentricity of the inner planet experiences large oscillations. The relative periastra of the outer two planets' orbits librate about 0 deg. in most of the stable systems; if future observations imply that the periastron longitudes of these planets are very closely aligned at the present epoch, dynamical simulations may provide precise estimates for the masses and orbital inclinations of these two planets.

M Stars as Targets for Terrestrial Exoplanet Searches And Biosignature Detection

NASA Astrophysics Data System (ADS)

Scalo, John; Kaltenegger, Lisa; Segura, Ant Gona; Fridlund, Malcolm; Ribas, Ignasi; Kulikov, Yu. N.; Grenfell, John L.; Rauer, Hieke; Odert, Petra; Leitzinger, Martin; Selsis, F.; Khodachenko, Maxim L.; Eiroa, Carlos; Kasting, Jim; Lammer, Helmut

2007-02-01

The changing view of planets orbiting low mass stars, M stars, as potentially hospitable worlds for life and its remote detection was motivated by several factors, including the demonstration of viable atmospheres and oceans on tidally locked planets, normal incidence of dust disks, including debris disks, detection of planets with masses in the 5-20 M⊕ range, and predictions of unusually strong spectral biosignatures. We present a critical discussion of M star properties that are relevant for the long- and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets, and the advantages and disadvantages of M stars as targets in searches for terrestrial HZ planets using various detection techniques. Biological viability seems supported by unmatched very long-term stability conferred by tidal locking, small HZ size, an apparent short-fall of gas giant planet perturbers, immunity to large astrosphere compressions, and several other factors, assuming incidence and evolutionary rate of life benefit from lack of variability. Tectonic regulation of climate and dynamo generation of a protective magnetic field, especially for a planet in synchronous rotation, are important unresolved questions that must await improved geodynamic models, though they both probably impose constraints on the planet mass. M star HZ terrestrial planets must survive a number of early trials in order to enjoy their many Gyr of stability. Their formation may be jeopardized by an insufficient initial disk supply of solids, resulting in the formation of objects too small and/or dry for habitability. The small empirical gas giant fraction for M stars reduces the risk of formation suppression or orbit disruption from either migrating or nonmigrating giant planets, but effects of perturbations from lower mass planets in these systems are uncertain. During the first ~1 Gyr, atmospheric retention is at peril because of intense and frequent stellar flares and sporadic energetic particle events, and impact erosion, both enhanced, the former dramatically, for M star HZ semimajor axes. Loss of atmosphere by interactions with energetic particles is likely unless the planetary magnetic moment is sufficiently large. For the smallest stellar masses a period of high planetary surface temperature, while the parent star approaches the main sequence, must be endured. The formation and retention of a thick atmosphere and a strong magnetic field as buffers for a sufficiently massive planet emerge as prerequisites for an M star planet to enter a long period of stability with its habitability intact. However, the star will then be subjected to short-term fluctuations with consequences including frequent unpredictable variation in atmospheric chemistry and surficial radiation field. After a review of evidence concerning disks and planets associated with M stars, we evaluate M stars as targets for future HZ planet search programs. Strong advantages of M stars for most approaches to HZ detection are offset by their faintness, leading to severe constraints due to accessible sample size, stellar crowding (transits), or angular size of the HZ (direct imaging). Gravitational lensing is unlikely to detect HZ M star planets because the HZ size decreases with mass faster than the Einstein ring size to which the method is sensitive. M star Earth-twin planets are predicted to exhibit surprisingly strong bands of nitrous oxide, methyl chloride, and methane, and work on signatures for other climate categories is summarized. The rest of the paper is devoted to an examination of evidence and implications of the unusual radiation and particle environments for atmospheric chemistry and surface radiation doses, and is summarized in the Synopsis. We conclude that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations. A detection or repeated nondetections could provide a unique opportunity to partially answer a fundamental and recurrent question about the relation between stability and complexity, one that is not addressed by remote detection from a planet orbiting a solar-like star, and can only be studied on Earth using restricted microbial systems in serial evolution experiments or in artificial life simulations. This proposal requires a planet that has retained its atmosphere and a water supply. The discussion given here suggests that observations of M star exoplanets can decide this latter question with only slight modifications to plans already in place for direct imaging terrestrial exoplanet missions. Key Words: M star planets-Habitable planets - Life and stellar activity - Spectral biosignatures - Terrestrial planet formation - Exoplanet properties. Astrobiology 7(1), 85 - 166.

Three regimes of extrasolar planet radius inferred from host star metallicities.

PubMed

Buchhave, Lars A; Bizzarro, Martin; Latham, David W; Sasselov, Dimitar; Cochran, William D; Endl, Michael; Isaacson, Howard; Juncher, Diana; Marcy, Geoffrey W

2014-05-29

Approximately half of the extrasolar planets (exoplanets) with radii less than four Earth radii are in orbits with short periods. Despite their sheer abundance, the compositions of such planets are largely unknown. The available evidence suggests that they range in composition from small, high-density rocky planets to low-density planets consisting of rocky cores surrounded by thick hydrogen and helium gas envelopes. Here we report the metallicities (that is, the abundances of elements heavier than hydrogen and helium) of more than 400 stars hosting 600 exoplanet candidates, and find that the exoplanets can be categorized into three populations defined by statistically distinct (∼4.5σ) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (radii less than 1.7 Earth radii), gas dwarf planets with rocky cores and hydrogen-helium envelopes (radii between 1.7 and 3.9 Earth radii) and ice or gas giant planets (radii greater than 3.9 Earth radii). These transitions correspond well with those inferred from dynamical mass estimates, implying that host star metallicity, which is a proxy for the initial solids inventory of the protoplanetary disk, is a key ingredient regulating the structure of planetary systems.

Three regimes of extrasolar planet radius inferred from host star metallicities

PubMed Central

Buchhave, Lars A.; Bizzarro, Martin; Latham, David W.; Sasselov, Dimitar; Cochran, William D.; Endl, Michael; Isaacson, Howard; Juncher, Diana; Marcy, Geoffrey W.

2014-01-01

Approximately half of the extrasolar planets (exoplanets) with radii less than four Earth radii are in orbits with short periods1. Despite their sheer abundance, the compositions of such planets are largely unknown. The available evidence suggests that they range in composition from small, high-density rocky planets to low-density planets consisting of rocky cores surrounded by thick hydrogen and helium gas envelopes. Here we report the metallicities (that is, the abundances of elements heavier than hydrogen and helium) of more than 400 stars hosting 600 exoplanet candidates, and find that the exoplanets can be categorized into three populations defined by statistically distinct (~4.5σ) metallicity regions. We interpret these regions as reflecting the formation regimes of terrestrial-like planets (radii less than 1.7 Earth radii), gas dwarf planets with rocky cores and hydrogen-helium envelopes (radii between 1.7 and 3.9 Earth radii) and ice or gas giant planets (radii greater than 3.9 Earth radii). These transitions correspond well with those inferred from dynamical mass estimates2,3, implying that host star metallicity, which is a proxy for the initial solids inventory of the protoplanetary disk, is a key ingredient regulating the structure of planetary systems. PMID:24870544

Exploring an Earth-sized neighbor: ground-based transmission spectroscopy of GJ1132b, a rocky planet transiting a small nearby M-dwarf

NASA Astrophysics Data System (ADS)

Diamond-Lowe, Hannah; Berta-Thompson, Zachory K.; Charbonneau, David; Irwin, Jonathan; Newton, Elisabeth R.; Dittmann, Jason

2017-01-01

The terrestrial planets of the Solar System are rocky worlds that did not accrete envelopes of hydrogen and helium, but instead possess thin secondary atmospheres, or no atmosphere at all. Until recently, most exoplanet atmospheric studies have centered around hot Jupiters, for which high planet-to-star radius ratios and short orbital periods allowed for observable transmission spectra. Now we have the opportunity to probe the atmosphere of a small, rocky exoplanet. GJ1132b has a radius of 1.2 Earth radii and a mass of 1.6 Earth masses, and orbits an M-dwarf 12 parsecs away. Determining the composition of GJ1132b's atmosphere is essential to understanding the nature of atmospheric evolution on terrestrial planets. We observed five transits of GJ1132b using the Magellan Clay telescope with the LDSS3C multi-object spectrograph. We compare the transit depth of GJ1132b in wavelength bins ranging from 0.65 -- 1.04 microns to infer whether or not GJ1132b has maintained its primordial hydrogen-dominated atmosphere. Should we find evidence of a hydrogen-dominated atmosphere, this would imply that a terrestrial planet is able to accrete and retain a low mean-molecular weight atmosphere from the planetary nebula. Coupled with recent UV spectra of the host star, our results can clarify the process of atmospheric escape on terrestrial worlds, with implications for formation histories of M-dwarf planets and the potential for habitability in these systems. If instead GJ1132b possesses a low mean-molecular weight atmosphere, we look to future observations with JWST and the ground-based extremely large telescopes to characterize its atmosphere.This material is based upon work supported by the National Science Foundation Graduate Research Fellowship Program. This work was made possible by a grant from the John Templeton Foundation.

Cracking the Code of Faraway Worlds

NASA Technical Reports Server (NTRS)

2007-01-01

This infrared data from NASA's Spitzer Space Telescope - called a spectrum - tells astronomers that a distant gas planet, a so-called 'hot Jupiter' called HD 209458b, might be smothered with high clouds. It is one of the first spectra of an alien world.

A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object.

Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called 'transiting' hot-Jupiter planets using the 'secondary eclipse' technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors.

When astronomers first saw the infrared spectrum above, they were shocked. It doesn't look anything like what theorists had predicted. For example, theorists thought there'd be signatures of water in the wavelength ranges of 8 to 9 microns. The fact that water is not detected might indicate that it is hidden under a thick blanket of high, dry clouds.

In addition, the spectrum shows signs of silicate dust -- tiny grains of sand -- in the wavelength range of 9 to 10 microns. This suggests that the planet's skies could be filled with high clouds of dust unlike anything seen in our own solar system.

There is also an unidentified molecular signature at 7.78 microns. Future observations using Spitzer's spectrograph should be able to determine the nature of the mysterious feature.

This spectrum was produced by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center, Greenbelt, Md. and his colleagues. The data were taken by Spitzer's infrared spectrograph on July 6 and 13, 2005.

Cracking the Code of Faraway Worlds

NASA Image and Video Library

2007-02-21

This infrared data from NASA's Spitzer Space Telescope -- called a spectrum -- tells astronomers that a distant gas planet, a so-called "hot Jupiter" called HD 209458b, might be smothered with high clouds. It is one of the first spectra of an alien world. A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object. Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called "transiting" hot-Jupiter planets using the "secondary eclipse" technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors. When astronomers first saw the infrared spectrum above, they were shocked. It doesn't look anything like what theorists had predicted. For example, theorists thought there'd be signatures of water in the wavelength ranges of 8 to 9 microns. The fact that water is not detected might indicate that it is hidden under a thick blanket of high, dry clouds. In addition, the spectrum shows signs of silicate dust -- tiny grains of sand -- in the wavelength range of 9 to 10 microns. This suggests that the planet's skies could be filled with high clouds of dust unlike anything seen in our own solar system. There is also an unidentified molecular signature at 7.78 microns. Future observations using Spitzer's spectrograph should be able to determine the nature of the mysterious feature. This spectrum was produced by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center, Greenbelt, Md. and his colleagues. The data were taken by Spitzer's infrared spectrograph on July 6 and 13, 2005. http://photojournal.jpl.nasa.gov/catalog/PIA09197

Cracking the Code of Faraway Worlds

NASA Image and Video Library

2007-02-21

This infrared data from NASA's Spitzer Space Telescope -- called a spectrum -- tells astronomers that a distant gas planet, a so-called "hot Jupiter" called HD 209458b, might be smothered with high clouds. It is one of the first spectra of an alien world. A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object. Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called "transiting" hot-Jupiter planets using the "secondary eclipse" technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors. When astronomers first saw the infrared spectrum above, they were shocked. It doesn't look anything like what theorists had predicted. For example, theorists thought there'd be signatures of water in the wavelength ranges of 8 to 9 microns. The fact that water is not detected might indicate that it is hidden under a thick blanket of high, dry clouds. In addition, the spectrum shows signs of silicate dust -- tiny grains of sand -- in the wavelength range of 9 to 10 microns. This suggests that the planet's skies could be filled with high clouds of dust unlike anything seen in our own solar system. There is also an unidentified molecular signature at 7.78 microns. Future observations using Spitzer's spectrograph should be able to determine the nature of the mysterious feature. This spectrum was produced by Dr. Jeremy Richardson of NASA's Goddard Space Flight Center, Greenbelt, Md. and his colleagues. The data were taken by Spitzer's infrared spectrograph on July 6 and 13, 2005. http://photojournal.jpl.nasa.gov/catalog/PIA09198

Jupiter's decisive role in the inner Solar System's early evolution.

PubMed

Batygin, Konstantin; Laughlin, Greg

2015-04-07

The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System's terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter's inward migration entrained s ≳ 10-100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System's terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

Planet signatures and Size Segregation in Debris Discs

NASA Astrophysics Data System (ADS)

Thébault, Philippe

2014-01-01

The response of a debris disc to a planetary perturber is the result of the complex interplay between gravitational effects, grain collisions and stellar radiation pressure (Stark & Kuchner (2009). We investigate to what extent this response can depart from the pure gravitational case when including grain collisional production and radiation pressure. We use the DyCoSS code (Thébault (2012), designed to study the coupled effect of collisions and dynamics for systems at steady state with one perturbing body. We focus on two outcomes: the 2D surface density profile of the disc+planet system, and the way the Particle Size Distribution (PSD) is spatially segregated within the disc. We consider two set-ups: 1) a narrow ring with an exterior ``shepherding'' planet, and 2) an extended disc in which a planet is embedded. For each case, the planet mass and orbit are explored as free parameters, and an unperturbed ``no-planet'' case is also considered. Another parameter is the disc's collisional activity, as parameterized by its optical depth τ.

Remote sensing for oceanography: Past, present, future

NASA Technical Reports Server (NTRS)

Mcgoldrick, L. F.

1984-01-01

Oceanic dynamics was traditionally investigated by sampling from instruments in situ, yielding quantitative measurements that are intermittent in both space and time; the ocean is undersampled. The need to obtain proper sampling of the averaged quantities treated in analytical and numerical models is at present the most significant limitation on advances in physical oceanography. Within the past decade, many electromagnetic techniques for the study of the Earth and planets were applied to the study of the ocean. Now satellites promise nearly total coverage of the world's oceans using only a few days to a few weeks of observations. Both a review of the early and present techniques applied to satellite oceanography and a description of some future systems to be launched into orbit during the remainder of this century are presented. Both scientific and technologic capabilities are discussed.

Early Hydrodynamic Escape Limits Rocky Planets to Less Than or Equal to 1.6 Earth Radii

NASA Technical Reports Server (NTRS)

Lehmer, O. R.; Catling, D. C.

2017-01-01

In the past decade thousands of exoplanet candidates and hundreds of confirmed exoplanets have been found. For sub-Neptune-sized planets, those less than approx. 10 Earth masses, we can separate planets into two broad categories: predominantly rocky planets, and gaseous planets with thick volatile sheaths. Observations and subsequent analysis of these planets show that rocky planets are only found with radii less than approx. 1.6 Earth radii. No rocky planet has yet been found that violates this limit. We propose that hydrodynamic escape of hydrogen rich protoatmospheres, accreted by forming planets, explains the limit in rocky planet size. Following the hydrodynamic escape model employed by Luger et al. (2015), we modelled the XUV driven escape from young planets (less than approx.100 Myr in age) around a Sun-like star. With a simple, first-order model we found that the rocky planet radii limit occurs consistently at approx. 1.6 Earth radii across a wide range of plausible parameter spaces. Our model shows that hydrodynamic escape can explain the observed cutoff between rocky and gaseous planets. Fig. 1 shows the results of our model for rocky planets between 0.5 and 10 Earth masses that accrete 3 wt. % H2/He during formation. The simulation was run for 100 Myr, after that time the XUV flux drops off exponentially and hydrodynamic escape drops with it. A cutoff between rocky planets and gaseous ones is clearly seen at approx. 1.5-1.6 Earth radii. We are only interested in the upper size limit for rocky planets. As such, we assumed pure hydrogen atmospheres and the highest possible isothermal atmospheric temperatures, which will produce an upper limit on the hydrodynamic loss rate. Previous work shows that a reasonable approximation for an upper temperature limit in a hydrogen rich protoatmosphere is 2000-3000 K, consistent with our assumptions. From these results, we propose that the observed dichotomy between mini-Neptunes and rocky worlds is simply explained by an early episode of thermally-driven hydrodynamic escape when host stars have saturated XUV fluxes.

Cracking the Code of Faraway Worlds

NASA Technical Reports Server (NTRS)

2007-01-01

This infrared data from NASA's Spitzer Space Telescope - called a spectrum - tells astronomers that a distant gas planet, a so-called 'hot Jupiter' called HD 189733b, might be smothered with high clouds. It is one of the first spectra of an alien world.

A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object.

Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called 'transiting' hot-Jupiter planets using the 'secondary eclipse' technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors.

Astronomers were perplexed when they first saw the infrared spectrum above. It doesn't look anything like what theorists had predicted. Theorists thought the spectra of hot, Jupiter-like planets like this one would be filled with the signatures of molecules in the planets' atmospheres. But the spectrum doesn't show any molecules, and is instead what astronomers call 'flat.' For example, theorists thought there'd be a strong signature of water in the form of a big drop in the wavelength range between 7 and 10 microns. The fact that water is not detected may indicate that it is hidden underneath a thick blanket of high, dry clouds. The average brightness of the spectrum is also a bit lower than theoretical predictions, suggesting that very high winds are rapidly moving the terrific heat of the noonday sun from the day side of HD 189733b to the night side.

This spectrum was produced by Dr. Carl Grillmair of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif., and his colleagues. The data were taken by Spitzer's infrared spectrograph on November 22, 2006.

Cracking the Code of Faraway Worlds

NASA Image and Video Library

2007-02-21

This infrared data from NASA's Spitzer Space Telescope -- called a spectrum -- tells astronomers that a distant gas planet, a so-called "hot Jupiter" called HD 189733b, might be smothered with high clouds. It is one of the first spectra of an alien world. A spectrum is created when an instrument called a spectrograph cracks light from an object open into a rainbow of different wavelengths. Patterns or ripples within the spectrum indicate the presence, or absence, of molecules making up the object. Astronomers using Spitzer's spectrograph were able to obtain infrared spectra for two so-called "transiting" hot-Jupiter planets using the "secondary eclipse" technique. In this method, the spectrograph first collects the combined infrared light from the planet plus its star, then, as the planet is eclipsed by the star, the infrared light of just the star. Subtracting the latter from the former reveals the planet's own rainbow of infrared colors. Astronomers were perplexed when they first saw the infrared spectrum above. It doesn't look anything like what theorists had predicted. Theorists thought the spectra of hot, Jupiter-like planets like this one would be filled with the signatures of molecules in the planets' atmospheres. But the spectrum doesn't show any molecules, and is instead what astronomers call "flat." For example, theorists thought there'd be a strong signature of water in the form of a big drop in the wavelength range between 7 and 10 microns. The fact that water is not detected may indicate that it is hidden underneath a thick blanket of high, dry clouds. The average brightness of the spectrum is also a bit lower than theoretical predictions, suggesting that very high winds are rapidly moving the terrific heat of the noonday sun from the day side of HD 189733b to the night side. This spectrum was produced by Dr. Carl Grillmair of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif., and his colleagues. The data were taken by Spitzer's infrared spectrograph on November 22, 2006. http://photojournal.jpl.nasa.gov/catalog/PIA09199

Hydrothermal Habitats: Measurements of Bulk Microbial Elemental Composition, and Models of Hydrothermal Influences on the Evolution of Dwarf Planets

NASA Astrophysics Data System (ADS)

Neveu, Marc Francois Laurent

Finding habitable worlds is a key driver of solar system exploration. Many solar system missions seek environments providing liquid water, energy, and nutrients, the three ingredients necessary to sustain life. Such environments include hydrothermal systems, spatially-confined systems where hot aqueous fluid circulates through rock by convection. I sought to characterize hydrothermal microbial communities, collected in hot spring sediments and mats at Yellowstone National Park, USA, by measuring their bulk elemental composition. To do so, one must minimize the contribution of non-biological material to the samples analyzed. I demonstrate that this can be achieved using a separation method that takes advantage of the density contrast between cells and sediment and preserves cellular elemental contents. Using this method, I show that in spite of the tremendous physical, chemical, and taxonomic diversity of Yellowstone hot springs, the composition of microorganisms there is surprisingly ordinary. This suggests the existence of a stoichiometric envelope common to all life as we know it. Thus, future planetary investigations could use elemental fingerprints to assess the astrobiological potential of hydrothermal settings beyond Earth. Indeed, hydrothermal activity may be widespread in the solar system. Most solar system worlds larger than 200 km in radius are dwarf planets, likely composed of an icy, cometary mantle surrounding a rocky, chondritic core. I enhance a dwarf planet evolution code, including the effects of core fracturing and hydrothermal circulation, to demonstrate that dwarf planets likely have undergone extensive water-rock interaction. This supports observations of aqueous products on their surfaces. I simulate the alteration of chondritic rock by pure water or cometary fluid to show that aqueous alteration feeds back on geophysical evolution: it modifies the fluid antifreeze content, affecting its persistence over geological timescales; and the distribution of radionuclides, whose decay is a chief heat source on dwarf planets. Interaction products can be observed if transported to the surface. I simulate numerically how cryovolcanic transport is enabled by primordial and hydrothermal volatile exsolution. Cryovolcanism seems plausible on dwarf planets in light of images recently returned by spacecrafts. Thus, these coupled geophysical-geochemical models provide a comprehensive picture of dwarf planet evolution, processes, and habitability.

Precisely measuring the density of small transiting exoplanets with particular emphasis on longer period planet using the HARPS-N spectrograph

NASA Astrophysics Data System (ADS)

Buchhave, Lars A.

2015-08-01

The majority of exoplanets discovered by the Kepler Mission have sizes that range between 1-4 Earth radii, populating a regime of planets with no Solar System analogues. This regime is critical for understanding the frequency of potentially habitable worlds and to help inform planet formation theories, because it contains the transition from lower-density planets with extended H/He envelopes to higher-density rocky planets with compact atmospheres. HARPS-N is an ultra-stable high-resolution spectrograph optimized for the measurement of precise radial velocities, yielding precise planetary masses and thus densities of small transiting exoplanets. In this talk, I will review the progress to populate the mass-radius parameter space with precisely measured densities of small planets. I will in particular focus on the latest HARPS-N results and their implication for our understanding of these super-Earth and small Neptune type planets.Additionally, I will discuss our progress to measure the masses of longer period sub-Neptune sized planets. In Buchhave el al. 2014, we found suggestive observational evidence that the transition from rocky to gaseous planets might depend on the orbital period, such that larger planets further away from their host star could be massive planets without a large gaseous envelope. To test this hypothesis, we have used HARPS-N to observe longer period planet candidates to determine whether they are in fact massive rocky planets or if they have extended H/He envelopes and thus lower bulk densities.HARPS-N at the Telescopio Nazionale Galileo, La Palma is an international collaboration and was funded by the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, and the Italian National Astrophysical Institute, University of St. Andrews, Queens University Belfast, and University of Edinburgh.

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-01-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34 +0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

The Ruinous Influence of Close Binary Companions on Planetary Systems

NASA Astrophysics Data System (ADS)

Kraus, Adam L.; Ireland, Michael; Mann, Andrew; Huber, Daniel; Dupuy, Trent J.

2017-06-01

The majority of solar-type stars are found in binary systems, and the dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of nearly 500 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. We super-resolve some binary systems to projected separations of under 5 AU, showing that planets might form in these dynamically active environments. However, the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside acut = 47 +59/-23 AU, the planet occurrence rate in binary systems is only Sbin = 0.34+0.14/-0.15 times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion.

Planetary size comparisons: A photographic study

NASA Technical Reports Server (NTRS)

Meszaros, S. P.

1983-01-01

Over the past two decades NASA spacecraft missions obtained photographs permitting accurate size measurements of the planets and moons, and their surface features. Planetary global views are displayed at the same scale, in each picture to allow visual size comparisons. Additionally, special geographical features on some of the planets are compared with selected Earth areas, again at the same scale. Artist renderings and estimated sizes are used for worlds not yet reached by spacecraft. Included with each picture is number designation for use in ordering copies of the photos.

The Quest for Other Worlds

NASA Astrophysics Data System (ADS)

Trimble, Virginia

2004-05-01

In the 4^th century BCE, Epicurus taught that there are an infinite number of worlds like (and unlike) ours, and Aristotle taught that there is only one. Neither hypothesis can currently be falsified. Over the ensuing millennia, the concept of aperoi kosmoi (plurality of worlds, or plenitude) has had four rather different meanings, each with a modern descendent, and all conceivably true. Some interpretations permit direct observation and knowledge of other worlds; some do not. The talk will explore these, ending with a précis of recent searches for planets orbiting other stars.

World Space Congress: a vision quest.

PubMed

Iannotta, Ben

2003-01-01

The World Space Congress (WSC) in October, 2002, brought together luminaries, aerospace engineers, students, and scientists to discuss strategies for reviving the world's space agency. WSC lectures and plenary sessions focused on future research in space. Among topics discussed are the use of the Hubble Space Telescope to scan for habitable planets and obtain data about the beginning of the universe, new weather satellites, planetary protection from comets or asteroids, exploration and establishment of colonies on the Moon and Mars, medical advances, the role of space exploration in the world economy.

Phylodynamics and movement of Phycodnaviruses among aquatic environments

PubMed Central

Gimenes, Manuela V; Zanotto, Paolo M de A; Suttle, Curtis A; da Cunha, Hillândia B; Mehnert, Dolores U

2012-01-01

Phycodnaviruses have a significant role in modulating the dynamics of phytoplankton, thereby influencing community structure and succession, nutrient cycles and potentially atmospheric composition because phytoplankton fix about half the carbon dioxide (CO2) on the planet, and some algae release dimethylsulphoniopropionate when lysed by viruses. Despite their ecological importance and widespread distribution, relatively little is known about the evolutionary history, phylogenetic relationships and phylodynamics of the Phycodnaviruses from freshwater environments. Herein we provide novel data on Phycodnaviruses from the largest river system on earth—the Amazon Basin—that were compared with samples from different aquatic systems from several places around the world. Based on phylogenetic inference using DNA polymerase (pol) sequences we show the presence of distinct populations of Phycodnaviridae. Preliminary coarse-grained phylodynamics and phylogeographic inferences revealed a complex dynamics characterized by long-term fluctuations in viral population sizes, with a remarkable worldwide reduction of the effective population around 400 thousand years before the present (KYBP), followed by a recovery near to the present time. Moreover, we present evidence for significant viral gene flow between freshwater environments, but crucially almost none between freshwater and marine environments. PMID:21796218

Spin-orbital Tidal Dynamics and Tidal Heating in the TRAPPIST-1 Multiplanet System

NASA Astrophysics Data System (ADS)

Makarov, Valeri V.; Berghea, Ciprian T.; Efroimsky, Michael

2018-04-01

We perform numerical simulations of the TRAPPIST-1 system of seven exoplanets orbiting a nearby M dwarf, starting with a previously suggested stable configuration. The long-term stability of this configuration is confirmed, but the motion of planets is found to be chaotic. The eccentricity values are found to vary within finite ranges. The rates of tidal dissipation and tidal evolution of orbits are estimated, assuming an Earth-like rheology for the planets. We find that under this assumption, the planets b, d, and e were captured in the 3:2 or higher spin–orbit resonances during the initial spin-down, but slipped further down into the 1:1 resonance. Depending on its rheology, the innermost planet b may be captured in a stable pseudosynchronous rotation. Nonsynchronous rotation ensures higher levels of tidal dissipation and internal heating. The positive feedback between the viscosity and the dissipation rate—and the ensuing runaway heating—are terminated by a few self-regulation processes. When the temperature is high and the viscosity is low enough, the planet spontaneously leaves the 3:2 resonance. Further heating is stopped either by passing the peak dissipation or by the emergence of partial melt in the mantle. In the post-solidus state, the tidal dissipation is limited to the levels supported by the heat transfer efficiency. The tides on the host star are unlikely to have had a significant dynamical impact. The tides on the synchronized inner planets tend to reduce these planets’ orbital eccentricity, possibly contributing thereby to the system’s stability.

Magellan

NASA Technical Reports Server (NTRS)

1985-01-01

Of all the planets in the solar system, Venus is the most like our own Earth in size, mass, and distance from the Sun. The motions of our planetary "twin" were known to the ancients, and its apparent changes in shape, similar to the phases of the Moon, were first studied by Galileo more than four centuries ago. In the modern era, it is by far the most visited world in the solar system - more than 20 spacecraft from the Soviet Union and the United States have been sent there since the early 1960's. The clouds of Venus have been probed, the structure and composition of its atmosphere measured, its landscape photographed, and its rocks chemically analyzed by automated landers. Yet, for all our fascination with Venus, we have only a sketchy, general knowledge of the planet's surface. While the other three "terrestrial" worlds - Earth, Mercury, and Mars have long since been mapped, details of the face of Venus are still largely unknown, due to the planet's dense, constant cloud cover. The clouds prevent us from ever photographing the solid surface, even from space, with conventional cameras. Beginning in the early 1960s, scientists on Earth began to counter this problem by using radar waves, which, unlike visible light, are able to penetrate the Venusian clouds and reflect off the solid planet back to Earth. With the help of computer processing, these radar reflections can be turned into pictures of the Venus surface. Earth-based radar imaging is thus extremely valuable. but it also is limited-Venus always shows the same hemisphere to us when it is near enough in its orbit for high-resolution study, so only a fraction of the planet can be explored from Earth.

Outer-planet scattering can gently tilt an inner planetary system

NASA Astrophysics Data System (ADS)

Gratia, Pierre; Fabrycky, Daniel

2017-01-01

Chaotic dynamics are expected during and after planet formation, and a leading mechanism to explain large eccentricities of gas giant exoplanets is planet-planet gravitational scattering. The same scattering has been invoked to explain misalignments of planetary orbital planes with respect to their host star's spin. However, an observational puzzle is presented by Kepler-56, which has two inner planets (b and c) that are nearly coplanar with each other, yet are more than 45° inclined to their star's equator. Thus, the spin-orbit misalignment might be primordial. Instead, we further develop the hypothesis in the discovery paper, that planets on wider orbits generated misalignment through scattering, and as a result gently torqued the inner planets away from the equator plane of the star. We integrated the equations of motion for Kepler-56 b and c along with an unstable outer system initialized with either two or three Jupiter-mass planets. We address here whether the violent scattering that generates large mutual inclinations can leave the inner system intact, tilting it gently. In almost all of the cases initially with two outer planets, either the inner planets remain nearly coplanar with each other in the star's equator plane, or they are scattered violently to high mutual inclination and high spin-orbit misalignment. On the contrary, of the systems with three unstable outer planets, a spin-orbit misalignment large enough to explain the observations is generated 28 per cent of the time for coplanar inner planets, which is consistent with the observed frequency of this phenomenon reported so far. We conclude that multiple-planet scattering in the outer parts of the system may account for this new population of coplanar planets hosted by oblique stars.

The Pan-Pacific Planet Search. IV. Two Super-Jupiters in a 3:5 Resonance Orbiting the Giant Star HD 33844

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Johnson, John Asher; Butler, R. P.; Horner, Jonathan; Wang, Liang; Robertson, Paul; Jones, M. I.; Jenkins, J. S.; Brahm, R.; Tinney, C. G.; Mengel, M. W.; Clark, J.

2016-02-01

We report the discovery of two giant planets orbiting the K giant HD 33844 based on radial velocity data from three independent campaigns. The planets move on nearly circular orbits with semimajor axes {a}b\\=1.60+/- 0.02 AU and {a}c=2.24+/- 0.05 AU, and have minimum masses (m sin I) of {M}b=1.96+/- 0.12 {M}{{Jup}} and {M}c=1.76+/- 0.18 {M}{{Jup}}. Detailed N-body dynamical simulations show that the two planets have remained on stable orbits for more than 106 years for low eccentricities and are most likely trapped in a mutual 3:5 mean motion resonance.

A Planetary System around the nearby M Dwarf GJ 667C with At Least One Super-Earth in Its Habitable Zone

NASA Astrophysics Data System (ADS)

Anglada-Escudé, Guillem; Arriagada, Pamela; Vogt, Steven S.; Rivera, Eugenio J.; Butler, R. Paul; Crane, Jeffrey D.; Shectman, Stephen A.; Thompson, Ian B.; Minniti, Dante; Haghighipour, Nader; Carter, Brad D.; Tinney, C. G.; Wittenmyer, Robert A.; Bailey, Jeremy A.; O'Toole, Simon J.; Jones, Hugh R. A.; Jenkins, James S.

2012-05-01

We re-analyze 4 years of HARPS spectra of the nearby M1.5 dwarf GJ 667C available through the European Southern Observatory public archive. The new radial velocity (RV) measurements were obtained using a new data analysis technique that derives the Doppler measurement and other instrumental effects using a least-squares approach. Combining these new 143 measurements with 41 additional RVs from the Magellan/Planet Finder Spectrograph and Keck/High Resolution Echelle Spectrometer spectrometers reveals three additional signals beyond the previously reported 7.2 day candidate, with periods of 28 days, 75 days, and a secular trend consistent with the presence of a gas giant (period ~10 years). The 28 day signal implies a planet candidate with a minimum mass of 4.5 M ⊕ orbiting well within the canonical definition of the star's liquid water habitable zone (HZ), that is, the region around the star at which an Earth-like planet could sustain liquid water on its surface. Still, the ultimate water supporting capability of this candidate depends on properties that are unknown such as its albedo, atmospheric composition, and interior dynamics. The 75 day signal is less certain, being significantly affected by aliasing interactions among a potential 91 day signal, and the likely rotation period of the star at 105 days detected in two activity indices. GJ 667C is the common proper motion companion to the GJ 667AB binary, which is metal-poor compared to the Sun. The presence of a super-Earth in the HZ of a metal-poor M dwarf in a triple star system supports the evidence that such worlds should be ubiquitous in the Galaxy.

ERCA 2008 - From the Human Dimensions of Global Environmental Change to the Observation of the Earth from Space

NASA Astrophysics Data System (ADS)

Boutron, Claude

2009-02-01

This book is the eighth volume in the series of books published within the framework of the European Research Course on Atmospheres ("ERCA"). ERCA was initiated in 1993 by the University Joseph Fourier of Grenoble, in order to provide PhD students and scientists from Europe and the rest of the world with a multidisciplinary course, which covers especially: the climate system and climate change; the physics and chemistry of the Earth's atmosphere; the human dimensions of environmental change; the other planets and satellites in the solar system and beyond. Since 1993, sixteen sessions have been attended by more 800 participants from 50 countries. The seventeenth session will take place from 12 January to 13 February 2009. This new volume contains twenty two chapters dealing with a wide range of topics. The following subjects are covered: the human dimensions of global environmental change; climate change and cryospheric evolution in China; the projections of twenty-first century climate over Europe; the understanding of the health impacts of air pollutants; air quality and human welfare; photocatalytic self-cleaning materials; radiative transfer in the cloudy atmosphere; laboratory modelling of atmospheric dynamical processes; stratospheric ozone; the applications of stable isotope analysis to atmospheric trace gas budgets; nitrogen oxides in the troposphere; the observation of the solid Earth, the oceans and land waters; the surface mass balance of the Greenland ice sheet; sea surface salinity reconstruction as seen with foraminifera shells; sources markers in aerosols, oceanic particles and sediments; the nucleation of atmospheric particles; the characterization of atmospheric aerosol episodes in China; the solar magnetic activity; the present and past climates of planet Mars; the outer solar system; Titan as an analog of Earth's past and future; the detection and characterization of extrasolar planets.

Hubble Finds New Dark Spot on Neptune

NASA Technical Reports Server (NTRS)

1995-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet.

The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared.

Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere.

Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere.

The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

a Numerical Study of Close Approaches for a Cloud of Debris Considering Atmospheric Drag and Lift

NASA Astrophysics Data System (ADS)

Gomes, Vivian; Golebiewska, Justyna; Prado, Antonio

The present paper study close approaches between a group of debris and a planet. The dynamical model considers the atmosphere of the planet, both in terms of drag as well as lift. This cloud is created during the passage of the spacecraft by the atmosphere of the planet, which is the responsible by the explosion of the spacecraft. The dynamical system is compos by the planet, the Sun, and the spacecraft, which explodes and becomes a cloud of debris. The planet and the Sun are in circular planar orbits. The equations of motion are the ones of the circular planar restricted three-body problem with the addition of the forces given by the atmospheric: drag and lift. The planet Jupiter is used for the numerical simulations. The initial conditions of the spacecraft and the debris are specified at the periapsis, which is the point where the explosion occurs. The equations of motion are numerically integrated forward in time for each particle, until a point where the particle is at a distance that can be considered far enough from the planet and it is possible to disregard the effects of the planet and consider the Sun-particle as a two-body system. Then we compute the velocity, energy and angular momentum after the passage by the planet, for each particle, based in the two-body celestial mechanics. From those results, the eccentricity and the semi-major axis of each particle can be obtained. Then, the orbit of the spacecraft is integrated backwards in time, as a single body. The difference from the usual close approaches technique is the presence of the atmosphere of the planet, which generates a drag and a lift forces in the spacecraft, which causes the explosion and modifies the trajectories of the debris generated by the explosion. The primary objective of the present paper is to map the modifications of the orbits of the debris that compose the cloud due to the close approach with the planet. Emphasis is given to map the orbital parameters of the debris after the close approach with the planet. Then, the effects are compared with the same maneuvers performed without the inclusion of the atmosphere. This type of research is useful, because it helps to obtain the size and density of the cloud of debris after the passage, as a function of time. That information has impact on the evaluations of the risks that spacecrafts suffer when passing by shorter distances from this cloud.

Jules Verne Voyager, Jr: An Interactive Map Tool for Teaching Plate Tectonics

NASA Astrophysics Data System (ADS)

Hamburger, M. W.; Meertens, C. M.

2010-12-01

We present an interactive, web-based map utility that can make new geological and geophysical results accessible to a large number and variety of users. The tool provides a user-friendly interface that allows users to access a variety of maps, satellite images, and geophysical data at a range of spatial scales. The map tool, dubbed 'Jules Verne Voyager, Jr.', allows users to interactively create maps of a variety of study areas around the world. The utility was developed in collaboration with the UNAVCO Consortium for study of global-scale tectonic processes. Users can choose from a variety of base maps (including "Face of the Earth" and "Earth at Night" satellite imagery mosaics, global topography, geoid, sea-floor age, strain rate and seismic hazard maps, and others), add a number of geographic and geophysical overlays (coastlines, political boundaries, rivers and lakes, earthquake and volcano locations, stress axes, etc.), and then superimpose both observed and model velocity vectors representing a compilation of 2933 GPS geodetic measurements from around the world. A remarkable characteristic of the geodetic compilation is that users can select from some 21 plates' frames of reference, allowing a visual representation of both 'absolute' plate motion (in a no-net rotation reference frame) and relative motion along all of the world's plate boundaries. The tool allows users to zoom among at least three map scales. The map tool can be viewed at http://jules.unavco.org/VoyagerJr/Earth. A more detailed version of the map utility, developed in conjunction with the EarthScope initiative, focuses on North America geodynamics, and provides more detailed geophysical and geographic information for the United States, Canada, and Mexico. The ‘EarthScope Voyager’ can be accessed at http://jules.unavco.org/VoyagerJr/EarthScope. Because the system uses pre-constructed gif images and overlays, the system can rapidly create and display maps to a large number of users simultaneously and does not require any special software installation on users' systems. In addition, a javascript-based educational interface, dubbed "Exploring our Dynamic Planet", incorporates the map tool, explanatory material, background scientific material, and curricular activities that encourage users to explore Earth processes using the Jules Verne Voyager, Jr. tool. Exploring our Dynamic Planet can be viewed at http://www.dpc.ucar.edu/VoyagerJr/. Because of its flexibility, the map utilities can be used for hands-on exercises exploring plate interaction in a range of academic settings, from high school science classes to entry-level undergraduate to graduate-level tectonics courses.

The detection and characterization of a nontransiting planet by transit timing variations.

PubMed

Nesvorný, David; Kipping, David M; Buchhave, Lars A; Bakos, Gáspár Á; Hartman, Joel; Schmitt, Allan R

2012-06-01

The Kepler mission is monitoring the brightness of ~150,000 stars, searching for evidence of planetary transits. As part of the Hunt for Exomoons with Kepler (HEK) project, we report a planetary system with two confirmed planets and one candidate planet discovered with the publicly available data for KOI-872. Planet b transits the host star with a period P(b) = 33.6 days and exhibits large transit timing variations indicative of a perturber. Dynamical modeling uniquely detects an outer nontransiting planet c near the 5:3 resonance (P(c) = 57.0 days) with a mass 0.37 times that of Jupiter. Transits of a third planetary candidate are also found: a 1.7-Earth radius super-Earth with a 6.8-day period. Our analysis indicates a system with nearly coplanar and circular orbits, reminiscent of the orderly arrangement within the solar system.

Superrotation on Venus, on Titan, and Elsewhere

NASA Astrophysics Data System (ADS)

Read, Peter L.; Lebonnois, Sebastien

2018-05-01

The superrotation of the atmospheres of Venus and Titan has puzzled dynamicists for many years and seems to put these planets in a very different dynamical regime from most other planets. In this review, we consider how to define superrotation objectively and explore the constraints that determine its occurrence. Atmospheric superrotation also occurs elsewhere in the Solar System and beyond, and we compare Venus and Titan with Earth and other planets for which wind estimates are available. The extreme superrotation on Venus and Titan poses some difficult challenges for numerical models of atmospheric circulation, much more difficult than for more rapidly rotating planets such as Earth or Mars. We consider mechanisms for generating and maintaining a superrotating state, all of which involve a global meridional overturning circulation. The role of nonaxisymmetric eddies is crucial, however, but the detailed mechanisms may differ between Venus, Titan, and other planets.

The Anglo-Australian Planet Search. XXIII. Two New Jupiter Analogs

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G.; Butler, R. P.; Jones, H. R. A.; Tuomi, Mikko; Salter, G. S.; Carter, B. D.; Koch, F. Elliott; O'Toole, S. J.; Bailey, J.; Wright, D.

2014-03-01

We report the discovery of two long-period giant planets from the Anglo-Australian Planet Search. HD 154857c is in a multiple-planet system, while HD 114613b appears to be solitary. HD 114613b has an orbital period P = 10.5 yr, and a minimum mass msin i of 0.48 M Jup; HD 154857c has P = 9.5 yr and msin i = 2.6 M Jup. These new data confirm the planetary nature of the previously unconstrained long-period object in the HD 154857 system. We have performed detailed dynamical stability simulations which show that the HD 154857 two-planet system is stable on timescales of at least 108 yr. These results highlight the continued importance of "legacy" surveys with long observational baselines; these ongoing campaigns are critical for determining the population of Jupiter analogs, and hence of those planetary systems with architectures most like our own solar system.

Pluto: Planet or "Dwarf Planet"?

NASA Astrophysics Data System (ADS)

Voelzke, M. R.; de Araújo, M. S. T.

2010-09-01

In August 2006 during the XXVI General Assembly of the International Astronomical Union (IAU), taken place in Prague, Czech Republic, new parameters to define a planet were established. According to this new definition Pluto will be no more the ninth planet of the Solar System but it will be changed to be a "dwarf planet". This reclassification of Pluto by the academic community clearly illustrates how dynamic science is and how knowledge of different areas can be changed and evolves through the time, allowing to perceive Science as a human construction in a constant transformation, subject to political, social and historical contexts. These epistemological characteristics of Science and, in this case, of Astronomy, constitute important elements to be discussed in the lessons, so that this work contributes to enable Science and Physics teachers who perform a basic education to be always up to date on this important astronomical fact and, thereby, carry useful information to their teaching.

Exoplanet dynamics. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars.

PubMed

Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

2015-02-06

Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets' rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere. Copyright © 2015, American Association for the Advancement of Science.

Biosignatures of Exoplanets

NASA Technical Reports Server (NTRS)

Kiang, Nancy Y.

2017-01-01

There was a time during Western civilization when musing about worlds other than Earth could be life-threatening. In 1600 Giordano Bruno was burnt at the stake as a heretic for claiming, amongst other things, that the fixed stars were in fact suns with planets moving around them, and furthermore, that lifeforms similar to those on Earth might exist on these planets. Although these ideas were not the result of scientific observation but rather of philosophical reflexions, Giordano Bruno is today recognized as the father of the idea of exoplanets. The study of planets revolving around distant stars has become one of the most thrilling disciplines in astronomy. As it did 400 years ago, this subject touches on the most profound questions of mankind, including the uniqueness of the planet Earth and even our own uniqueness as an intelligent species. As always in astronomy distance is an issue. While it requires a lot of patience to reach the planets within our own solar system, direct visits to exoplanets will not be feasible in the foreseeable future. Is there an alternative approach to find a second Earth?

Monitoring Active Atmospheres on Uranus and Neptune

NASA Astrophysics Data System (ADS)

Rages, Kathy

2009-07-01

We propose Snapshot observations of Uranus and Neptune to monitor changes in their atmospheres on time scales of weeks and months, as we have been doing for the past seven years. Previous Hubble Space Telescope observations {including previous Snapshot programs 8634, 10170, 10534, and 11156}, together with near-IR images obtained using adaptive optics on the Keck Telescope, reveal both planets to be dynamic worlds which change on time scales ranging from hours to {terrestrial} years. Uranus equinox occurred in December 2007, and the northern hemisphere is becoming fully visible for the first time since the early 1960s. HST observations during the past several years {Hammel et al. 2005, Icarus 175, 284 and references therein} have revealed strongly wavelength-dependent latitudinal structure, the presence of numerous visible-wavelength cloud features in the northern hemisphere, at least one very long-lived discrete cloud in the southern hemisphere, and in 2006 the first clearly defined dark spot seen on Uranus. Long-term ground-based observations {Lockwood and Jerzekiewicz, 2006, Icarus 180, 442; Hammel and Lockwood 2007, Icarus 186, 291} reveal seasonal brightness changes that seem to demand the appearance of a bright northern polar cap within the next few years. Recent HST and Keck observations of Neptune {Sromovsky et al. 2003, Icarus 163, 256 and references therein} show a general increase in activity at south temperate latitudes until 2004, when Neptune returned to a rather Voyager-like appearance with discrete bright spots rather than active latitude bands. Further Snapshot observations of these two dynamic planets will elucidate the nature of long-term changes in their zonal atmospheric bands and clarify the processes of formation, evolution, and dissipation of discrete albedo features.

Sustainability, collapse and oscillations in a simple World-Earth model

NASA Astrophysics Data System (ADS)

Nitzbon, Jan; Heitzig, Jobst; Parlitz, Ulrich

2017-07-01

The Anthropocene is characterized by close interdependencies between the natural Earth system and the global human society, posing novel challenges to model development. Here we present a conceptual model describing the long-term co-evolution of natural and socio-economic subsystems of Earth. While the climate is represented via a global carbon cycle, we use economic concepts to model socio-metabolic flows of biomass and fossil fuels between nature and society. A well-being-dependent parametrization of fertility and mortality governs human population dynamics. Our analysis focuses on assessing possible asymptotic states of the Earth system for a qualitative understanding of its complex dynamics rather than quantitative predictions. Low dimension and simple equations enable a parameter-space analysis allowing us to identify preconditions of several asymptotic states and hence fates of humanity and planet. These include a sustainable co-evolution of nature and society, a global collapse and everlasting oscillations. We consider different scenarios corresponding to different socio-cultural stages of human history. The necessity of accounting for the ‘human factor’ in Earth system models is highlighted by the finding that carbon stocks during the past centuries evolved opposing to what would ‘naturally’ be expected on a planet without humans. The intensity of biomass use and the contribution of ecosystem services to human well-being are found to be crucial determinants of the asymptotic state in a (pre-industrial) biomass-only scenario without capital accumulation. The capitalistic, fossil-based scenario reveals that trajectories with fundamentally different asymptotic states might still be almost indistinguishable during even a centuries-long transient phase. Given current human population levels, our study also supports the claim that besides reducing the global demand for energy, only the extensive use of renewable energies may pave the way into a sustainable future.

This dynamic earth: the story of plate tectonics

USGS Publications Warehouse

Kious, W. Jacquelyne; Tilling, Robert I.

1996-01-01

In the early 1960s, the emergence of the theory of plate tectonics started a revolution in the earth sciences. Since then, scientists have verified and refined this theory, and now have a much better understanding of how our planet has been shaped by plate-tectonic processes. We now know that, directly or indirectly, plate tectonics influences nearly all geologic processes, past and present. Indeed, the notion that the entire Earth's surface is continually shifting has profoundly changed the way we view our world.People benefit from, and are at the mercy of, the forces and consequences of plate tectonics. With little or no warning, an earthquake or volcanic eruption can unleash bursts of energy far more powerful than anything we can generate. While we have no control over plate-tectonic processes, we now have the knowledge to learn from them. The more we know about plate tectonics, the better we can appreciate the grandeur and beauty of the land upon which we live, as well as the occasional violent displays of the Earth's awesome power.This booklet gives a brief introduction to the concept of plate tectonics and complements the visual and written information in This Dynamic Planet (see Further reading), a map published in 1994 by the U.S. Geological Survey (USGS) and the Smithsonian Institution. The booklet highlights some of the people and discoveries that advanced the development of the theory and traces its progress since its proposal. Although the general idea of plate tectonics is now widely accepted, many aspects still continue to confound and challenge scientists. The earth-science revolution launched by the theory of plate tectonics is not finished.

The Earth Microbiome Project and modeling the planets microbial potential (Invited)

NASA Astrophysics Data System (ADS)

Gilbert, J. A.

2013-12-01

The understanding of Earth's climate and ecology requires multiscale observations of the biosphere, of which microbial life are a major component. However, to acquire and process physical samples of soil, water and air that comprise the appropriate spatial and temporal resolution to capture the immense variation in microbial dynamics, would require a herculean effort and immense financial resources dwarfing even the most ambitious projects to date. To overcome this hurdle we created the Earth Microbiome Project, a crowd-sourced effort to acquire physical samples from researchers around the world that are, importantly, contextualized with physical, chemical and biological data detailing the environmental properties of that sample in the location and time it was acquired. The EMP leverages these existing efforts to target a systematic analysis of microbial taxonomic and functional dynamics across a vast array of environmental parameter gradients. The EMP captures the environmental gradients, location, time and sampling protocol information about every sample donated by our valued collaborators. Physical samples are then processed using a standardized DNA extraction, PCR, and shotgun sequencing protocol to generate comparable data regarding the microbial community structure and function in each sample. To date we have processed >17,000 samples from 40 different biomes. One of the key goals of the EMP is to map the spatiotemporal variability of microbial communities to capture the changes in important functional processes that need to be appropriately expressed in models to provide reliable forecasts of ecosystem phenotype across our changing planet. This is essential if we are to develop economically sound strategies to be good stewards of our Earth. The EMP recognizes that environments are comprised of complex sets of interdependent parameters and that the development of useful predictive computational models of both terrestrial and atmospheric systems requires recognition and accommodation of sources of uncertainty.

Analogs from LEO: Mapping Earth Observations to Planetary Science & Astrobiology. (Invited)

NASA Astrophysics Data System (ADS)

Hand, K. P.; Painter, T. H.

2010-12-01

If, as Charles Lyell articulated ‘the present is the key to the past’ for terrestrial geology, then perhaps by extension the Earth, our planet, is the key to understanding other planets. This is the basic premise behind planetary analogs. Many planetary science missions, however, utilize orbiters and are therefore constrained to remote sensing. This is the reverse of how we developed our understanding of Earth’s environments; remote sensing is a relatively new tool for understanding environments and processes on Earth. Here we present several cases and comparisons between Earth’s cryosphere and icy worlds of the outer Solar System (e.g. Europa, Titan, and Enceladus), where much of our knowledge is limited to remote observations (the sole exception being the Huygens probe to Titan). Three regions are considered: glaciers in the Sierra Nevada, the permafrost lakes of Alaska’s North Slope, and spreading centers of the ocean floor. Two key issues are examined: 1) successes and limitations for understanding processes that shape icy worlds, and 2) successes and limitations for assessing the habitability of icy worlds from orbit. Finally, technological considerations for future orbiting mission to icy worlds are presented.

Multiverses of the past

NASA Astrophysics Data System (ADS)

Trimble, V.

2009-07-01

More than 2000 years ago, Epicurus taught that there are an infinite number of other worlds, both like and unlike ours, and Aristotle taught that there are none. Neither hypothesis can currently be falsified, and some versions of current multiverses perhaps never can be, which has contributed to occasional claims that ``this isn't science!" (a common complaint about cosmology for centuries). Define ``cosmos", or ``world", or ``universe" to mean the largest structure of which you and the majority of knowledgeable contemporaries will admit to being a part. This begins with the small, earth-centered worlds of ancient Egyptian paintings, Greek mythology, and Genesis, which a god could circumnavigate in a day and humans in a generation. These tend to expand and become helio- rather than geo-centric (not quite monotonically in time) and are succeeded by various assemblages of sun-like stars with planets of their own. Finite vs. infinite assemblages are debated and then the issue of whether the Milky Way is unique (so that ``island universes" made sense, even if you were against the idea) for a couple of centuries. Today one thinks as a rule of the entire 4-dimensional space-time we might in principle communicate with and all its contents. Beyond are the modern multi-verses, sequential (cyclic or oscillating), hierarchical, or non-communicating entities in more than four dimensions. Each of these has older analogues, and, in every milieu where the ideas have been discussed, there have been firm supporters and firm opponents, some of whose ideas are explored here. Because astronomical observations have firmly settled some earlier disputes in favor of very many galaxies and very many stars with planets, ``other worlds" can now refer only to other planets like Earth or to other universes. The focus is on the latter.

Dynamics and Origin of the 2:1 Orbital Resonances of the GJ 876 Planets

NASA Astrophysics Data System (ADS)

Lee, Man Hoi; Peale, S. J.

2002-03-01

The discovery by Marcy and coworkers of two planets in 2:1 orbital resonance about the star GJ 876 has been supplemented by a dynamical fit to the data by Laughlin & Chambers, which places the planets in coplanar orbits deep in three resonances at the 2:1 mean-motion commensurability. The selection of this almost singular state by the dynamical fit means that the resonances are almost certainly real, and with the small amplitudes of libration of the resonance variables, indefinitely stable. Several unusual properties of the 2:1 resonances are revealed by the GJ 876 system. The libration of both lowest order mean-motion resonance variables and the secular resonance variable, θ1=λ1- 2λ2+ϖ1, θ2=λ1- 2λ2+ϖ2, and θ3=ϖ1-ϖ2, about 0° (where λ1,2 are the mean longitudes of the inner and outer planet and ϖ1,2 are the longitudes of periapse) differs from the familiar geometry of the Io-Europa pair, where θ2 and θ3 librate about 180°. By considering the condition that ϖ1=ϖ2 for stable simultaneous librations of θ1 and θ2, we show that the GJ 876 geometry results from the large orbital eccentricities ei, whereas the very small eccentricities in the Io-Europa system lead to the latter's geometry. Surprisingly, the GJ 876 configuration, with θ1, θ2, and θ3 all librating, remains stable for e1 up to 0.86 and for amplitude of libration of θ1 approaching 45° with the current eccentricities-further supporting the indefinite stability of the existing system. Any process that drives originally widely separated orbits toward each other could result in capture into the observed resonances at the 2:1 commensurability. We find that forced inward migration of the outer planet of the GJ 876 system results in certain capture into the observed resonances if initially e1<~0.06 and e2<~0.03 and the migration rate |a2/a2|<~3×10- 2(a2/AU)-3/2yr-1. Larger eccentricities lead to likely capture into higher order resonances before the 2:1 commensurability is reached. The planets are sufficiently massive to open gaps in the nebular disk surrounding the young GJ 876 and to clear the disk material between them, and the resulting planet-nebular interaction typically forces the outer planet to migrate inward on the disk viscous timescale, whose inverse is about 3 orders of magnitude less than the above upper bound on |a2/a2| for certain capture. If there is no eccentricity damping, eccentricity growth is rapid with continued migration within the resonance, with ei exceeding the observed values after a further reduction in the semimajor axes ai of only 7%. With eccentricity damping ei/ei=-K|ai/ai|, the eccentricities reach equilibrium values that remain constant for arbitrarily long migration within the resonances. The equilibrium eccentricities are close to the observed eccentricities for K~100 if there is migration and damping of the outer planet only, but for K~10 if there is also migration and damping of the inner planet. This result is independent of the magnitude or functional form of the migration rate ai as long as ei/ei=-K|ai/ai|. Although existing analytic estimates of the effects of planet-nebula interaction are consistent with this form of eccentricity damping for certain disk parameter values, it is as yet unclear that such interaction can produce the large value of K required to obtain the observed eccentricities. The alternative eccentricity damping by tidal dissipation within the star or the planets is completely negligible, so the observed dynamical properties of the GJ 876 system may require an unlikely fine-tuning of the time of resonance capture to be near the end of the nebula lifetime.

The Lore of Saturn

NASA Image and Video Library

2007-03-01

The giant planet is a moody world whose disposition appears to change with he view. Its atmosphere rages with thunderous and hurricane-like storms. Its majestic rings spin a tale of ancient collisions and cataclysm

Resonant Capture and Tidal Evolution in Circumbinary Systems: Testing the Case of Kepler-38

NASA Astrophysics Data System (ADS)

Zoppetti, F. A.; Beaugé, C.; Leiva, A. M.

2018-04-01

Circumbinary planets are thought to form far from the central binary and migrate inwards by interactions with the circumbinary disk, ultimately stopping near their present location either by a planetary trap near the disk inner edge or by resonance capture. Here, we analyze the second possibility, presenting a detailed numerical study on the capture process, resonant dynamics and tidal evolution of circumbinary planets in high-order mean-motion resonances (MMRs). Planetary migration was modeled as an external acceleration in an N-body code, while tidal effects were incorporated with a weak-friction equilibrium tide model. As a working example we chose Kepler-38, a highly evolved system with a planet in the vicinity of the 5/1 MMR. Our simulations show that resonance capture is a high-probability event under a large range of system parameters, although several different resonant configuration are possible. We identified three possible outcomes: aligned librations, anti-aligned librations and chaotic solutions. All were found to be dynamically stable, even after the dissipation of the disk, for time-spans of the order of the system's age. We found that while tidal evolution decreases the binary's separation, the semimajor axis of the planet is driven outwards. Although the net effect is a secular increase in the mean-motion ratio, the system requires a planetary tidal parameter of the order of unity to reproduce the observed orbital configuration. The results presented here open an interesting outlook into the complex dynamics of high-order resonances in circumbinary systems.

Resonant capture and tidal evolution in circumbinary systems: testing the case of Kepler-38

NASA Astrophysics Data System (ADS)

Zoppetti, F. A.; Beaugé, C.; Leiva, A. M.

2018-07-01

Circumbinary planets are thought to form far from the central binary and migrate inwards by interactions with the circumbinary disc, ultimately stopping near their present location either by a planetary trap near the disc inner edge or by resonance capture. Here, we analyse the second possibility, presenting a detailed numerical study on the capture process, resonant dynamics, and tidal evolution of circumbinary planets in high-order mean-motion resonances (MMRs). Planetary migration was modelled as an external acceleration in an N-body code, while tidal effects were incorporated with a weak-friction equilibrium tide model. As a working example, we chose Kepler-38, a highly evolved system with a planet in the vicinity of the 5/1 MMR. Our simulations show that resonance capture is a high-probability event under a large range of system parameters, although several different resonant configuration are possible. We identified three possible outcomes: aligned librations, anti-aligned librations, and chaotic solutions. All were found to be dynamically stable, even after the dissipation of the disc, for time spans of the order of the system's age. We found that while tidal evolution decreases the binary's separation, the semimajor axis of the planet is driven outwards. Although the net effect is a secular increase in the mean-motion ratio, the system requires a planetary tidal parameter of the order of unity to reproduce the observed orbital configuration. The results presented here open an interesting outlook into the complex dynamics of high-order resonances in circumbinary systems.

A Journey through the Universe

NASA Astrophysics Data System (ADS)

Morison, Ian

2014-09-01

1. Watchers of the skies; 2. Our Sun; 3. Aspects of our Solar System; 4. The rocky planets; 5. The hunt for Planet X; 6. Voyages to the outer planets; 7. Harbingers of doom; 8. Impact!; 9. 400 years of the telescope; 10. The family of stars; 11. Aging stars; 12. The search for other worlds; 13. Are we alone? The search for life beyond the Earth; 14. Our island Universe; 15. Wonders of the southern sky; 16: Proving Einstein right; 17. Black holes - no need to be afraid; 18. It's about time; 19. Hubble's heritage - the astronomer and the telescope that honours his name; 20. The violent Universe; 21. The invisible Universe: dark matter and dark energy; 22. The afterglow of creation; 23. To infinity and beyond; Index.

An international approach to Mission to Planet Earth

NASA Technical Reports Server (NTRS)

Lawrence, Robert M.; Sadeh, Willy Z.; Tsygichko, Viktor N.

1992-01-01

The new international political constellation resulting from the disintegration of the Soviet Union opens up unique opportunities for cooperation in the space arena. Precedents since 1955 indicate a pervasive interest in mutual cooperation to use military reconnaissance and surveillance satellites for space observations to enforce treaty verification and compliance. One of the avenues that offer immediate prospects for fruitful cooperation is the incorporation of the military reconnaissance and surveillance satellite capabilities of both U.S. and Russia into the Mission to Planet Earth. Formation of a United Nations Satellite (UNSAT) fleet drawn from the American and Russian space assets is proposed. The role of UNSAT is to provide world wide monitoring of both military and enviromental activities under the umbrella of the Mission to Planet Earth.

Proceedings of the 39th Lunar and Planetary Science Conference

NASA Technical Reports Server (NTRS)

2008-01-01

Sessions with oral presentations include: A SPECIAL SESSION: MESSENGER at Mercury, Mars: Pingos, Polygons, and Other Puzzles, Solar Wind and Genesis: Measurements and Interpretation, Asteroids, Comets, and Small Bodies, Mars: Ice On the Ground and In the Ground, SPECIAL SESSION: Results from Kaguya (SELENE) Mission to the Moon, Outer Planet Satellites: Not Titan, Not Enceladus, SPECIAL SESSION: Lunar Science: Past, Present, and Future, Mars: North Pole, South Pole - Structure and Evolution, Refractory Inclusions, Impact Events: Modeling, Experiments, and Observations, Mars Sedimentary Processes from Victoria Crater to the Columbia Hills, Formation and Alteration of Carbonaceous Chondrites, New Achondrite GRA 06128/GRA 06129 - Origins Unknown, The Science Behind Lunar Missions, Mars Volcanics and Tectonics, From Dust to Planets (Planetary Formation and Planetesimals):When, Where, and Kaboom! Astrobiology: Biosignatures, Impacts, Habitability, Excavating a Comet, Mars Interior Dynamics to Exterior Impacts, Achondrites, Lunar Remote Sensing, Mars Aeolian Processes and Gully Formation Mechanisms, Solar Nebula Shake and Bake: Mixing and Isotopes, Lunar Geophysics, Meteorites from Mars: Shergottite and Nakhlite Invasion, Mars Fluvial Geomorphology, Chondrules and Chondrule Formation, Lunar Samples: Chronology, Geochemistry, and Petrology, Enceladus, Venus: Resurfacing and Topography (with Pancakes!), Overview of the Lunar Reconnaissance Orbiter Mission, Mars Sulfates, Phyllosilicates, and Their Aqueous Sources, Ordinary and Enstatite Chondrites, Impact Calibration and Effects, Comparative Planetology, Analogs: Environments and Materials, Mars: The Orbital View of Sediments and Aqueous Mineralogy, Planetary Differentiation, Titan, Presolar Grains: Still More Isotopes Out of This World, Poster sessions include: Education and Public Outreach Programs, Early Solar System and Planet Formation, Solar Wind and Genesis, Asteroids, Comets, and Small Bodies, Carbonaceous Chondrites, Chondrules and Chondrule Formation, Chondrites, Refractory Inclusions, Organics in Chondrites, Meteorites: Techniques, Experiments, and Physical Properties, MESSENGER and Mercury, Lunar Science Present: Kaguya (SELENE) Results, Lunar Remote Sensing: Basins and Mapping of Geology and Geochemistry, Lunar Science: Dust and Ice, Lunar Science: Missions and Planning, Mars: Layered, Icy, and Polygonal, Mars Stratigraphy and Sedimentology, Mars (Peri)Glacial, Mars Polar (and Vast), Mars, You are Here: Landing Sites and Imagery, Mars Volcanics and Magmas, Mars Atmosphere, Impact Events: Modeling, Experiments, and Observation, Ice is Nice: Mostly Outer Planet Satellites, Galilean Satellites, The Big Giant Planets, Astrobiology, In Situ Instrumentation, Rocket Scientist's Toolbox: Mission Science and Operations, Spacecraft Missions, Presolar Grains, Micrometeorites, Condensation-Evaporation: Stardust Ties, Comet Dust, Comparative Planetology, Planetary Differentiation, Lunar Meteorites, Nonchondritic Meteorites, Martian Meteorites, Apollo Samples and Lunar Interior, Lunar Geophysics, Lunar Science: Geophysics, Surface Science, and Extralunar Components, Mars, Remotely, Mars Orbital Data - Methods and Interpretation, Mars Tectonics and Dynamics, Mars Craters: Tiny to Humongous, Mars Sedimentary Mineralogy, Martian Gullies and Slope Streaks, Mars Fluvial Geomorphology, Mars Aeolian Processes, Mars Data and Mission,s Venus Mapping, Modeling, and Data Analysis, Titan, Icy Dwarf Satellites, Rocket Scientist's Toolbox: In Situ Analysis, Remote Sensing Approaches, Advances, and Applications, Analogs: Sulfates - Earth and Lab to Mars, Analogs: Remote Sensing and Spectroscopy, Analogs: Methods and Instruments, Analogs: Weird Places!. Print Only Early Solar System, Solar Wind, IDPs, Presolar/Solar Grains, Stardust, Comets, Asteroids, and Phobos, Venus, Mercury, Moon, Meteorites, Mars, Astrobiology, Impacts, Outer Planets, Satellites, and Rings, Support for Mission Operations, Analog Education and Public Outreach.

Water-rich planets: How habitable is a water layer deeper than on Earth?

NASA Astrophysics Data System (ADS)

Noack, L.; Höning, D.; Rivoldini, A.; Heistracher, C.; Zimov, N.; Journaux, B.; Lammer, H.; Van Hoolst, T.; Bredehöft, J. H.

2016-10-01

Water is necessary for the origin and survival of life as we know it. In the search for life-friendly worlds, water-rich planets therefore are obvious candidates and have attracted increasing attention in recent years. The surface H2O layer on such planets (containing a liquid water ocean and possibly high-pressure ice below a specific depth) could potentially be hundreds of kilometres deep depending on the water content and the evolution of the proto-atmosphere. We study possible constraints for the habitability of deep water layers and introduce a new habitability classification relevant for water-rich planets (from Mars-size to super-Earth-size planets). A new ocean model has been developed that is coupled to a thermal evolution model of the mantle and core. Our interior structure model takes into account depth-dependent thermodynamic properties and the possible formation of high-pressure ice. We find that heat flowing out of the silicate mantle can melt an ice layer from below (in some cases episodically), depending mainly on the thickness of the ocean-ice shell, the mass of the planet, the surface temperature and the interior parameters (e.g. radioactive mantle heat sources). The high pressure at the bottom of deep water-ice layers could also impede volcanism at the water-mantle boundary for both stagnant lid and plate tectonics silicate shells. We conclude that water-rich planets with a deep ocean, a large planet mass, a high average density or a low surface temperature are likely less habitable than planets with an Earth-like ocean.

On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

NASA Astrophysics Data System (ADS)

Fleming, David; Barnes, Rory; Graham, David E.; Luger, Rodrigo; Quinn, Thomas R.

2018-04-01

To date, no binary star system with an orbital period less than 7.5 days has been observed to host a circumbinary planet (CBP), a puzzling observation given the thousands of binary stars with orbital periods < 10 days discovered by the Kepler mission (Kirk et al., 2016) and the observational biases that favor their detection (Munoz & Lai, 2015). We outline a mechanism that explains the observed lack of CBPs via coupled stellar-tidal evolution of isolated binary stars. Tidal forces between low-mass, short-period binary stars on the pre-main sequence slow the stellar rotations, transferring rotational angular momentum to the orbit as the stars approach the tidally locked state. This transfer increases the binary orbital period, expanding the region of dynamical instability around the binary, and destabilizing CBPs that tend to preferentially orbit just beyond the initial dynamical stability limit. After the stars tidally lock, we find that angular momentum loss due to magnetic braking can significantly shrink the binary orbit, and hence the region of dynamical stability, over time impacting where surviving CBPs are observed relative to the boundary. We perform simulations over a wide range of parameter space and find that the expansion of the instability region occurs for most plausible initial conditions and that in some cases, the stability semi-major axis doubles from its initial value. We examine the dynamical and observable consequences of a CBP falling within the dynamical instability limit by running N-body simulations of circumbinary planetary systems and find that typically, at least one planet is ejected from the system. We apply our theory to the shortest period Kepler binary that possesses a CBP, Kepler-47, and find that its existence is consistent with our model. Under conservative assumptions, we find that coupled stellar-tidal evolution of pre-main sequence binary stars removes at least one close-in CBP in 87% of multi-planet circumbinary systems.

DYNAMICS OF TIDALLY CAPTURED PLANETS IN THE GALACTIC CENTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trani, Alessandro A.; Bressan, Alessandro; Mapelli, Michela

2016-11-01

Recent observations suggest ongoing planet formation in the innermost parsec of the Galactic center. The supermassive black hole (SMBH) might strip planets or planetary embryos from their parent star, bringing them close enough to be tidally disrupted. Photoevaporation by the ultraviolet field of young stars, combined with ongoing tidal disruption, could enhance the near-infrared luminosity of such starless planets, making their detection possible even with current facilities. In this paper, we investigate the chance of planet tidal captures by means of high-accuracy N -body simulations exploiting Mikkola's algorithmic regularization. We consider both planets lying in the clockwise (CW) disk andmore » planets initially bound to the S-stars. We show that tidally captured planets remain on orbits close to those of their parent star. Moreover, the semimajor axis of the planetary orbit can be predicted by simple analytic assumptions in the case of prograde orbits. We find that starless planets that were initially bound to CW disk stars have mild eccentricities and tend to remain in the CW disk. However, we speculate that angular momentum diffusion and scattering by other young stars in the CW disk might bring starless planets into orbits with low angular momentum. In contrast, planets initially bound to S-stars are captured by the SMBH on highly eccentric orbits, matching the orbital properties of the clouds G1 and G2. Our predictions apply not only to planets but also to low-mass stars initially bound to the S-stars and tidally captured by the SMBH.« less

Vesper - Venus Chemistry and Dynamics Orbiter - A NASA Discovery Mission Proposal: Submillimeter Investigation of Atmospheric Chemistry and Dynamics

NASA Technical Reports Server (NTRS)

Chin, Gordon

2011-01-01

Vesper conducts a focused investigation of the chemistry and dynamics of the middle atmosphere of our sister planet- from the base of the global cloud cover to the lower thermosphere. The middle atmosphere controls the stability of the Venus climate system. Vesper determines what processes maintain the atmospheric chemical stability, cause observed variability of chemical composition, control the escape of water, and drive the extreme super-rotation. The Vesper science investigation provides a unique perspective on the Earth environment due to the similarities in the middle atmosphere processes of both Venus and the Earth. Understanding key distinctions and similarities between Venus and Earth will increase our knowledge of how terrestrial planets evolve along different paths from nearly identical initial conditions.

Gas Velocities Reveal Newly Born Planets in a Disk

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-06-01

Occasionally, science comes together beautifully for a discovery and sometimes this happens for more than one team at once! Today we explore how two independent collaborations of scientists simultaneously found the very first kinematic evidence for young planets forming in a protoplanetary disk. Though they explored the same disk, the two teams in fact discovered different planets.Evidence for PlanetsALMAs view of the dust in the protoplanetary disk surrounding the young star HD 163296. Todays studies explore not the dust, but the gas of this disk. [ALMA (ESO/NAOJ/NRAO); A. Isella; B. Saxton (NRAO/AUI/NSF)]Over the past three decades, weve detected around 4,000 fully formed exoplanets. Much more elusive, however, are the young planets still in the early stages of formation; only a handful of these have been discovered. More observations of early-stage exoplanets are needed in order to understand how these worlds are born in dusty protoplanetary-disk environments, how they grow their atmospheres, and how they evolve.Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) have produced stunning images of protoplanetary disks. The unprecedented resolution of these images reveals substructure in the form of gaps and rings, hinting at the presence of planets that orbit within the disk and clear out their paths as they move. But there are also non-planet mechanisms that could produce such substructure, like grain growth around ice lines, or hydrodynamic instabilities in the disk.How can we definitively determine whether there are nascent planets embedded in these disks? Direct direction of a point source in a dust gap would be a strong confirmation, but now we have the next best thing: kinematic evidence for planets, from the motion of a disks gas.Observations of carbon monoxide line emission at +1km/s from the systemic velocity (left) vs. the outcome of a computer simulation (right) in the Pinte et al. study. A visible kink occurs in the flow, which can be reproduced by the presence of a 2-Jupiter-mass planet at 260 AU. [Pinte et al. 2018]Watching Gas MoveIn two papers published today in ApJL one led by Richard Teague (University of Michigan) and the other led by Christophe Pinte (Monash University in Australia and Grenoble Alpes University in France) astronomers have announced the detection of distinctive signs of planets in the gas motion of the disk surrounding HD 163296. This young star, located about 330 light-years away, is only 4 million years old.Unlike studies that hinge on observations of a disks dust which only makes up 1% of the disks mass! both studies here took a new approach: they used detailed ALMA observations revealing the dynamics of the disks carbon monoxide gas. By studying the gass motion, the teams found deviations from the Keplerian velocity that would be expected if there were no planets present. The authors then ran simulations to demonstrate that the deviations are consistent with local pressure perturbations caused by the passage of giant planets.Rotational velocity deviations due to changes in the local pressure, caused in this simulation by the presence of planets. [Teague et al. 2018]Giants FoundWhat did they find? Teague and collaborators, whose technique to identify velocity variations is best suited to explore the inner regions of the disk, discovered evidence for two separate Jupiter-mass planets orbiting at distances of 83 AU and 137 AU in the disk. Pinte and collaborators, whose velocity-measurement technique better explores the outer regions of the disk, found evidence for a two-Jupiter-mass planet orbiting at 260 AU.These results will rely on additional imaging in the coming years to confirm the presence of these newly born planets and a detection of point sources at these radii remains a hopeful goal for the future. Nonetheless, the new techniques explored here by Teague, Pinte, and collaborators are a promising route for young exoplanet discovery and characterization in other disks imaged by ALMA and future instruments.CitationRichard Teague et al 2018 ApJL 860 L12. doi:10.3847/2041-8213/aac6d7C. Pinte et al 2018 ApJL 860 L13. doi:10.3847/2041-8213/aac6dc

Habitability and the Possibility of Extraterrestrial Life in the Early Telescope Era

NASA Astrophysics Data System (ADS)

Reynolds, Sarah

2014-01-01

Early telescopic observations of the Moon and planets prompted great interest in the already-existing debate about the possibility of life on the Moon and other worlds. New observations of the lunar surface, revealing an apparently Earth-like terrain and possibly the presence of bodies of water, were often considered in relation to their implications for the existence of lunar inhabitants. This depended upon establishing what constituted the fundamental requirements for life and the boundaries of habitability. The growing support for the heliocentric Copernican astronomy was also changing perceptions of the relationships between the Earth, the Moon, and the planets. Works such as Johannes Kepler’s Somnium and John Wilkins’ The Discovery of a World in the Moone presented views of extraterrestrial life that were shifting from the supernatural to the natural, in correspondence with the celestial bodies’ new positions in the cosmos. This paper considers how these and other works from the early telescope era reveal changes in the nature of astronomical speculation about extraterrestrial life and the conditions construed as “habitability,” and what significance that history has for us today in the new era of extrasolar planet discovery.

The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

NASA Technical Reports Server (NTRS)

Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagne, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob;

Multiphase Dynamics of Magma Oceans

NASA Astrophysics Data System (ADS)

Boukaré, Charles-Edouard; Ricard, Yanick; Parmentier, Edgar M.

2017-04-01

Since the earliest study of the Apollo lunar samples, the magma ocean hypothesis has received increasing consideration for explaining the early evolution of terrestrial planets. Giant impacts seem to be able to melt significantly large planets at the end of their accretion. The evolution of the resulting magma ocean would set the initial conditions (thermal and compositionnal structure) for subsequent long-term solid-state planet dynamics. However, magma ocean dynamics remains poorly understood. The major challenge relies on understanding interactions between the physical properties of materials (e.g., viscosity (at liquid or solid state), buoyancy) and the complex dynamics of an extremely vigorously convecting system. Such complexities might be neglected in cases where liquidus/adiabat interactions and density stratification leads to stable situations. However, interesting possibilities arise when exploring magma ocean dynamics in other regime. In the case of the Earth, recent studies have shown that the liquidus might intersect the adiabat at mid-mantle depth and/or that solids might be buoyant at deep mantle conditions. These results require the consideration of more sophisticated scenarios. For instance, how does bottom-up crystallization look with buoyant crystals? To understand this complex dynamics, we develop a multiphase phase numerical code that can handle simultaneously phase change, the convection in each phase and in the slurry, as well as the compaction or decompaction of the two phases. Although our code can only run in a limited parameter range (Rayleigh number, viscosity contrast between phases, Prandlt number), it provides a rich dynamics that illustrates what could have happened. For a given liquidus/adiabat configuration and density contrast between melt and solid, we explore magma ocean scenarios by varying the relative timescales of three first order processes: solid-liquid separation, thermo-chemical convective motions and magma ocean cooling.

77 FR 55101 - National Wilderness Month, 2012

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-06

... centuries, America's dramatic landscapes have attracted people from around the world to begin new lives and... responsibility that falls to us all as Americans and as inhabitants of this small planet. During National...

Alien plants

NASA Astrophysics Data System (ADS)

2018-04-01

No-one’s ever travelled to an extrasolar planet, or even observed one that we’re sure harbours life. But if plants do exist on such alien worlds, we can have fun speculating what form they might take.

14th Annual P3 Awards: A National Student Design ...

EPA Pesticide Factsheets

2017-02-14

EPA as part of its People, Prosperity and the Planet (P3) Award Program – is seeking applications proposing to research, develop, and design solutions to real world challenges involving sustainability.

Earth science: Extraordinary world

NASA Astrophysics Data System (ADS)

Day, James M. D.

2016-09-01

The isotopic compositions of objects that formed early in the evolution of the Solar System have been found to be similar to Earth's composition -- overturning notions of our planet's chemical distinctiveness. See Letters p.394 & p.399

Super-Earths, Warm-Neptunes, and Hot-Jupiters: Transmission Spectroscopy for Comparative Planetology

NASA Astrophysics Data System (ADS)

Fraine, Jonathan D.; Deming, Drake; Knutson, Heather; Jordán, Andrés

2014-11-01

We used the Kepler, Hubble, and Spitzer Space Telescopes to probe the diversity of exoplanetary atmospheres with transmission spectroscopy, constraining atomic and molecular absorption in Jupiter- and Neptune-sized exoplanets. The detections and non-detections of molecular species such as water, methane, and carbon monoxide lead to greater understanding of planet formation and evolution. Recent significant advances in both theoretical and observational discoveries from planets like HD189733b, HD209458b, GJ436, as well as our own work with HAT-P-11b and GJ1214b, have shown that the range of measurable atmospheric properties spans from clear, molecular absorption dominated worlds to opaque worlds, with cloudy, hazy, or high mean molecular weight atmospheres. Characterization of these significant non-detections allows us to infer the existence of cloud compositions at high altitudes, or mean molecular weights upwards of ~1000x solar. Neither scenario was expected from extrapolations of solar system analogs. We present here our published results from GJ1214b and HAT-P-11b, as well as our recent work on HAT-P-7b and HAT-P-13b. We search for evidence of atmospheric hazes and clouds, and place constraints on the relative abundance of water vapor, methane, and carbon monoxide-- in the case of cloud-free atmospheres. We conclude by discussing how our results compare to transmission spectra obtained for other similar planets, and use these combined data to develop a better understanding for the nature of these distant and alien worlds.

Taking the Measure of the Universe : Precision Astrometry with SIM PlanetQuest

NASA Technical Reports Server (NTRS)

Unwin, Stephen C.; Shao, Michael; Tanner, Angelle M.; Allen, Ronald J.; Beichman, Charles A.; Boboltz, David; Catanzarite, Joseph H.; Chaboyer, Brian C.; Ciardi, David R.; Edberg, Stephen J.;

An empirically derived three-dimensional Laplace resonance in the Gliese 876 planetary system

NASA Astrophysics Data System (ADS)

Nelson, Benjamin E.; Robertson, Paul M.; Payne, Matthew J.; Pritchard, Seth M.; Deck, Katherine M.; Ford, Eric B.; Wright, Jason T.; Isaacson, Howard T.

2016-01-01

We report constraints on the three-dimensional orbital architecture for all four planets known to orbit the nearby M dwarf Gliese 876 based solely on Doppler measurements and demanding long-term orbital stability. Our data set incorporates publicly available radial velocities taken with the ELODIE and CORALIE spectrographs, High Accuracy Radial velocity Planet Searcher (HARPS), and Keck HIgh Resolution Echelle Spectrometer (HIRES) as well as previously unpublished HIRES velocities. We first quantitatively assess the validity of the planets thought to orbit GJ 876 by computing the Bayes factors for a variety of different coplanar models using an importance sampling algorithm. We find that a four-planet model is preferred over a three-planet model. Next, we apply a Newtonian Markov chain Monte Carlo algorithm to perform a Bayesian analysis of the planet masses and orbits using an N-body model in three-dimensional space. Based on the radial velocities alone, we find that a 99 per cent credible interval provides upper limits on the mutual inclinations for the three resonant planets (Φcb < 6.20° for the {c} and {b} pair and Φbe < 28.5° for the {b} and {e} pair). Subsequent dynamical integrations of our posterior sample find that the GJ 876 planets must be roughly coplanar (Φcb < 2.60° and Φbe < 7.87°, suggesting that the amount of planet-planet scattering in the system has been low. We investigate the distribution of the respective resonant arguments of each planet pair and find that at least one argument for each planet pair and the Laplace argument librate. The libration amplitudes in our three-dimensional orbital model support the idea of the outer three planets having undergone significant past disc migration.

EXTRASOLAR BINARY PLANETS. II. DETECTABILITY BY TRANSIT OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, K. M.; Ida, S.; Ochiai, H.

2015-05-20

We discuss the detectability of gravitationally bound pairs of gas-giant planets (which we call “binary planets”) in extrasolar planetary systems that are formed through orbital instability followed by planet–planet dynamical tides during their close encounters, based on the results of N-body simulations by Ochiai et al. (Paper I). Paper I showed that the formation probability of a binary is as much as ∼10% for three giant planet systems that undergo orbital instability, and after post-capture long-term tidal evolution, the typical binary separation is three to five times the sum of the physical radii of the planets. The binary planets aremore » stable during the main-sequence lifetime of solar-type stars, if the stellarcentric semimajor axis of the binary is larger than 0.3 AU. We show that detecting modulations of transit light curves is the most promising observational method to detect binary planets. Since the likely binary separations are comparable to the stellar diameter, the shape of the transit light curve is different from transit to transit, depending on the phase of the binary’s orbit. The transit durations and depth for binary planet transits are generally longer and deeper than those for the single planet case. We point out that binary planets could exist among the known inflated gas-giant planets or objects classified as false positive detections at orbital radii ≳0.3 AU, propose a binary planet explanation for the CoRoT candidate SRc01 E2 1066, and show that binary planets are likely to be present in, and could be detected using, Kepler-quality data.« less

The Dynamical Structure of HR 8799's Inner Debris Disk

NASA Astrophysics Data System (ADS)

Contro, B.; Wittenmyer, Robert A.; Horner, J.; Marshall, Jonathan P.

2015-06-01

The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system.

The Dynamical Structure of HR 8799's Inner Debris Disk.

PubMed

Contro, B; Wittenmyer, Robert A; Horner, J; Marshall, Jonathan P

2015-06-01

The HR 8799 system, with its four giant planets and two debris belts, has an architecture closely mirroring that of our Solar system where the inner, warm asteroid belt and outer, cool Edgeworth-Kuiper belt bracket the giant planets. As such, it is a valuable laboratory for examining exoplanetary dynamics and debris disk-exoplanet interactions. Whilst the outer debris belt of HR 8799 has been well resolved by previous observations, the spatial extent of the inner disk remains unknown. This leaves a significant question mark over both the location of the planetesimals responsible for producing the belt's visible dust and the physical properties of those grains. We have performed the most extensive simulations to date of the inner, unresolved debris belt around HR 8799, using UNSW Australia's Katana supercomputing facility to follow the dynamical evolution of a model inner disk comprising 300,298 particles for a period of 60 Ma. These simulations have enabled the characterisation of the extent and structure of the inner disk in detail, and will in future allow us to provide a first estimate of the small-body impact rate and water delivery prospects for possible (as-yet undetected) terrestrial planet (s) in the inner system.

The Search for Habitable Worlds. 1. The Viability of a Starshade Mission

NASA Technical Reports Server (NTRS)

Turnbull, Margaret C.; Glassman, Tiffany; Roberge, Aki; Cash, Webster; Noecker, Charley; Lo, Amy; Mason, Brian; Oakley, Phil; Bally, John

2012-01-01

As part of NASA's mission to explore habitable planets orbiting nearby stars, this article explores the detection and characterization capabilities of a 4 m space telescope plus 50 m starshade located at the Earth-Sun L2 point, known as the New Worlds Observer (NWO). Our calculations include the true spectral types and distribution of stars on the sky, an iterative target selection protocol designed to maximize efficiency based on prior detections, and realistic mission constraints. We conduct simulated observing runs for a wide range in exozodiacal background levels (epsilon = 1-100 times the local zodi brightness) and overall prevalence of Earth-like terrestrial planets (eta(sub solar halo))0.1-1). We find that even without any return visits, the NWO baseline architecture (IWA = 65 mas, limiting FPB = 4 x 10(exp -11) can achieve a 95% probability of detecting and spectrally characterizing at least one habitable Earth-like planet and an expectation value of approximately 3 planets found, within the mission lifetime and delta V budgets, even in the worst-case scenario (eta(sub solar halo) = 0.1 and = epsilon = 100 zodis for every target). This achievement requires about 1 yr of integration time spread over the 5 yr mission, leaving the remainder of the telescope time for UV-NIR general astrophysics. Cost and technical feasibility considerations point to a "sweet spot" in starshade design near a 50 m starshade effective diameter. with 12 or 16 petals, at a distance of 70,000-100,000 km from the telescope.

Worlds Fantastic, Worlds Familiar

NASA Astrophysics Data System (ADS)

Buratti, Bonnie J.

2017-02-01

Introduction; 1. Mercury: the hottest little place; 2. Venus: an even hotter place; 3. Mars: the abode of life?; 4. Asteroids and comets: sweat the small stuff; 5. Galileo's treasures: worlds of fire and ice; 6. Enceladus: an active iceball in space; 7. Titan: an Earth in deep freeze?; 8. Iapetus and its friends: the weirdest 'planets' in the Solar System; 9. Pluto: the first view of the 'third zone'; 10. Earths above: the search for exoplanets and life in the universe; Epilogue; Glossary; Acknowledgements; Index.

Characterization of the K2-18 multi-planetary system with HARPS. A habitable zone super-Earth and discovery of a second, warm super-Earth on a non-coplanar orbit

NASA Astrophysics Data System (ADS)

Cloutier, R.; Astudillo-Defru, N.; Doyon, R.; Bonfils, X.; Almenara, J.-M.; Benneke, B.; Bouchy, F.; Delfosse, X.; Ehrenreich, D.; Forveille, T.; Lovis, C.; Mayor, M.; Menou, K.; Murgas, F.; Pepe, F.; Rowe, J.; Santos, N. C.; Udry, S.; Wünsche, A.

2017-12-01

Aims: The bright M2.5 dwarf K2-18 (Ms = 0.36 M⊙, Rs = 0.41 R⊙) at 34 pc is known to host a transiting super-Earth-sized planet orbiting within the star's habitable zone; K2-18b. Given the superlative nature of this system for studying an exoplanetary atmosphere receiving similar levels of insolation as the Earth, we aim to characterize the planet's mass which is required to interpret atmospheric properties and infer the planet's bulk composition. Methods: We have obtained precision radial velocity measurements with the HARPS spectrograph. We then coupled those measurements with the K2 photometry to jointly model the observed radial velocity variation with planetary signals and a correlated stellar activity model based on Gaussian process regression. Results: We measured the mass of K2-18b to be 8.0 ± 1.9M⊕ with a bulk density of 3.3 ± 1.2 g/cm3 which may correspond to a predominantly rocky planet with a significant gaseous envelope or an ocean planet with a water mass fraction ≳50%. We also find strong evidence for a second, warm super-Earth K2-18c (mp,csinic = 7.5 ± 1.3 M⊕) at approximately nine days with a semi-major axis 2.4 times smaller than the transiting K2-18b. After re-analyzing the available light curves of K2-18 we conclude that K2-18c is not detected in transit and therefore likely has an orbit that is non-coplanar with the orbit of K2-18b although only a small mutual inclination is required for K2-18c to miss a transiting configuration; | Δi| 1-2°. A suite of dynamical integrations are performed to numerically confirm the system's dynamical stability. By varying the simulated orbital eccentricities of the two planets, dynamical stability constraints are used as an additional prior on each planet's eccentricity posterior from which we constrain eb < 0.43 and ec < 0.47 at the level of 99% confidence. Conclusions: The discovery of the inner planet K2-18c further emphasizes the prevalence of multi-planet systems around M dwarfs. The characterization of the density of K2-18b reveals that the planet likely has a thick gaseous envelope which, along with its proximity to the solar system, makes the K2-18 planetary system an interesting target for the atmospheric study of an exoplanet receiving Earth-like insolation. Table A.2 is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A35

The dynamical behaviour of our planetary system. Proceedings. 4th Alexander von Humboldt Colloquium on Celestial Mechanics, Ramsau (Austria), 17 - 23 Mar 1996.

NASA Astrophysics Data System (ADS)

Dvorak, R.; Henrard, J.

1996-03-01

The following topics were dealt with: celestial mechanics, dynamical astronomy, planetary systems, resonance scattering, Hamiltonian mechanics non-integrability, irregular periodic orbits, escape, dynamical system mapping, fast Fourier method, precession-nutation, Nekhoroshev theorem, asteroid dynamics, the Trojan problem, planet-crossing orbits, Kirkwood gaps, future research, human comprehension limitations.

Indirect and Direct Signatures of Young Planets in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Zhu, Zhaohuan; Stone, James M.; Dong, Ruobing; Rafikov, Roman; Bai, Xue-Ning

2015-12-01

Directly finding young planets around protostars is challenging since protostars are highly variable and obscured by dust. However, young planets will interact with protoplanetary disks, inducing disk features such as gaps, spiral arms, and asymmetric features, which are much easier to be detected. Transitional disks, which are protoplanetary disks with gaps and holes, are excellent candidates for finding young planets. Although these disks have been studied extensively in observations (e.g. using Subaru, VLT, ALMA, EVLA), theoretical models still need to be developed to explain observations. We have constructed numerical simulations, including dust particle dynamics and MHD effects, to study planet-disk interaction, with an emphasis on explaining observations. Our simulations have successfully reproduced spiral arms, gaps and asymmetric features observed in transitional disks. Furthermore, by comparing with observations, we have constrained protoplanetary disk properties and pinpoint potential planets in these disks. We will present progress in constructing global simulations to study transitional disks, including using our recently developed Athena++ code with static-mesh-refinement for MHD. Finally we suggest that accreting circumplanetary disks can release an observable amount of energy and could be the key to detect young planets directly. We will discuss how JWST and next generation telescopes can help to find these young planets with circumplanetary disks.

DETECTABILITY OF EARTH-LIKE PLANETS IN CIRCUMSTELLAR HABITABLE ZONES OF BINARY STAR SYSTEMS WITH SUN-LIKE COMPONENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eggl, Siegfried; Pilat-Lohinger, Elke; Haghighipour, Nader, E-mail: siegfried.eggl@univie.ac.at

2013-02-20

Given the considerable percentage of stars that are members of binaries or stellar multiples in the solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the {alpha} Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones (HZ), especially in close S-type binary systems, can be rather inaccurate. Recent progress in this field, however, allows us to identify regions around the star permitting permanent habitability. While the discovery ofmore » {alpha} Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogs in HZs. We provide analytical expressions for the maximum and rms values of radial velocity and astrometric signals, as well as transit probabilities of terrestrial planets in such systems, showing that the dynamical interaction of the second star with the planet may indeed facilitate the planets' detection. As an example, we discuss the detectability of additional Earth-like planets in the averaged, extended, and permanent HZs around both stars of the {alpha} Centauri system.« less

Fluxgate magnetometers for outer planets exploration

NASA Technical Reports Server (NTRS)

Acuna, M. H.

1974-01-01

The exploration of the interplanetary medium and the magnetospheres of the outer planets requires the implementation of magnetic field measuring instrumentation with wide dynamic range, high stability, and reliability. The fluxgate magnetometers developed for the Pioneer 11 and Mariner-Jupiter-Saturn missions are presented. These instruments cover the range of .01 nT to 2 million nT with optimum performance characteristics and low power consumption.

THE RADIAL VELOCITY TATOOINE SEARCH FOR CIRCUMBINARY PLANETS: PLANET DETECTION LIMITS FOR A SAMPLE OF DOUBLE-LINED BINARY STARS-INITIAL RESULTS FROM KECK I/HIRES, SHANE/CAT/HAMSPEC, AND TNG/SARG OBSERVATIONS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konacki, Maciej; Helminiak, Krzysztof G.; Muterspaugh, Matthew W.

2009-10-10

We present preliminary results of the first and on-going radial velocity survey for circumbinary planets. With a novel radial velocity technique employing an iodine absorption cell, we achieve an unprecedented radial velocity (RV) precision of up to 2 m s{sup -1} for double-lined binary stars. The high-resolution spectra collected with the Keck I/Hires, TNG/Sarg, and Shane/CAT/Hamspec telescopes/spectrographs over the years 2003-2008 allow us to derive RVs and compute planet detection limits for 10 double-lined binary stars. For this initial sample of targets, we can rule out planets on dynamically stable orbits with masses as small as approx0.3 to 3 Mmore » {sub Jup} for the orbital periods of up to approx5.3 years. Even though the presented sample of stars is too small to make any strong conclusions, it is clear that the search for circumbinary planets is now technique-wise possible and eventually will provide new constraints for the planet formation theories.« less

Volatiles Inventory to the Inner Planets Due to Small Bodies Migration

NASA Technical Reports Server (NTRS)

Marov, M. Y.; Ipatov, S. I.

2003-01-01

The concurrent processes of endogeneous and exogeneous origin are assumed to be responsible for the volatile reserves in the terrestrial planets. Volatiles inventory through collisions is rooted in orbital dynamics of small bodies including near-Earth objects (NEOs), short and long-period comets, and trans-Neptunian objects (TNOs), the latter probably supplying a large amount of Jupiter crossing objects (JCOs). Our model testifies that even a relatively small portion (approx. 0.001) of JCOs which transit to orbits with aphelia inside Jupiter's orbit (Q<4.7 AU) and reside such orbits during more than 1 Myr may contribute significantly in collisions with the terrestrial planets. The total mass of volatiles delivered to the Earth from the feeding zone of the giant planets could be greater than the mass of the Earth's oceans.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, Joshua; Tremaine, Scott; Chambers, John, E-mail: joshuajw@princeton.edu

Collisional fragmentation is shown to not be a barrier to rocky planet formation at small distances from the host star. Simple analytic arguments demonstrate that rocky planet formation via collisions of homogeneous gravity-dominated bodies is possible down to distances of order the Roche radius ( r {sub Roche}). Extensive N -body simulations with initial bodies ≳1700 km that include plausible models for fragmentation and merging of gravity-dominated bodies confirm this conclusion and demonstrate that rocky planet formation is possible down to ∼1.1 r {sub Roche}. At smaller distances, tidal effects cause collisions to be too fragmenting to allow mass buildupmore » to a final, dynamically stable planetary system. We argue that even differentiated bodies can accumulate to form planets at distances that are not much larger than r {sub Roche}.« less

VLT Detects First Superstorm on Exoplanet

NASA Astrophysics Data System (ADS)

2010-06-01

Astronomers have measured a superstorm for the first time in the atmosphere of an exoplanet, the well-studied "hot Jupiter" HD209458b. The very high-precision observations of carbon monoxide gas show that it is streaming at enormous speed from the extremely hot day side to the cooler night side of the planet. The observations also allow another exciting "first" - measuring the orbital speed of the exoplanet itself, providing a direct determination of its mass. The results appear this week in the journal Nature. "HD209458b is definitely not a place for the faint-hearted. By studying the poisonous carbon monoxide gas with great accuracy we found evidence for a super wind, blowing at a speed of 5000 to 10 000 km per hour" says Ignas Snellen, who led the team of astronomers. HD209458b is an exoplanet of about 60% the mass of Jupiter orbiting a solar-like star located 150 light-years from Earth towards the constellation of Pegasus (the Winged Horse). Circling at a distance of only one twentieth the Sun-Earth distance, the planet is heated intensely by its parent star, and has a surface temperature of about 1000 degrees Celsius on the hot side. But as the planet always has the same side to its star, one side is very hot, while the other is much cooler. "On Earth, big temperature differences inevitably lead to fierce winds, and as our new measurements reveal, the situation is no different on HD209458b," says team member Simon Albrecht. HD209458b was the first exoplanet to be found transiting: every 3.5 days the planet moves in front of its host star, blocking a small portion of the starlight during a three-hour period. During such an event a tiny fraction of the starlight filters through the planet's atmosphere, leaving an imprint. A team of astronomers from the Leiden University, the Netherlands Institute for Space Research (SRON), and MIT in the United States, have used ESO's Very Large Telescope and its powerful CRIRES spectrograph to detect and analyse these faint fingerprints, observing the planet for about five hours, as it passed in front of its star. "CRIRES is the only instrument in the world that can deliver spectra that are sharp enough to determine the position of the carbon monoxide lines at a precision of 1 part in 100 000," says another team member Remco de Kok. "This high precision allows us to measure the velocity of the carbon monoxide gas for the first time using the Doppler effect." The astronomers achieved several other firsts. They directly measured the velocity of the exoplanet as it orbits its home star. "In general, the mass of an exoplanet is determined by measuring the wobble of the star and assuming a mass for the star, according to theory. Here, we have been able to measure the motion of the planet as well, and thus determine both the mass of the star and of the planet," says co-author Ernst de Mooij. Also for the first time, the astronomers measured how much carbon is present in the atmosphere of this planet. "It seems that H209458b is actually as carbon-rich as Jupiter and Saturn. This could indicate that it was formed in the same way," says Snellen. "In the future, astronomers may be able to use this type of observation to study the atmospheres of Earth-like planets, to determine whether life also exists elsewhere in the Universe." More information This research was presented in a paper that appears this week in the journal Nature: "The orbital motion, absolute mass, and high-altitude winds of exoplanet HD209458b", by I. Snellen et al. The team is composed of Ignas A. G. Snellen and Ernst J. W. de Mooij, (Leiden Observatory, The Netherlands), Remco J. de Kok (SRON, Utrecht, The Netherlands), and Simon Albrecht (Massachusetts Institute of Technology, USA). ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".

Abrupt Climate Transition of Icy Worlds from Snowball to Moist or Runaway Greenhouse

NASA Astrophysics Data System (ADS)

Yang, J.; Ding, F.; Ramirez, R. M.; Peltier, W. R.; Hu, Y.; Liu, Y.

2017-12-01

Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by the evolutionary history of its climate. It has been suggested that icy planets and moons become habitable after their initial ice shield melts as their host stars brighten. Here we show from global climate model simulations that a habitable state is not achieved in the climatic evolution of those icy planets and moons that possess an inactive carbonate-silicate cycle and low concentrations of greenhouse gases. Examples for such planetary bodies are the icy moons Europa and Enceladus, and certain icy exoplanets orbiting G and F stars. We find that the stellar fluxes that are required to overcome a planet's initial snowball state are so large that they lead to significant water loss and preclude a habitable planet. Specifically, they exceed the moist greenhouse limit, at which water vapour accumulates at high altitudes where it can readily escape, or the runaway greenhouse limit, at which the strength of the greenhouse increases until the oceans boil away. We suggest that some icy planetary bodies may transition directly to a moist or runaway greenhouse without passing through a habitable Earth-like state.

Abrupt climate transition of icy worlds from snowball to moist or runaway greenhouse

NASA Astrophysics Data System (ADS)

Yang, Jun; Ding, Feng; Ramirez, Ramses M.; Peltier, W. R.; Hu, Yongyun; Liu, Yonggang

2017-08-01

Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by the evolutionary history of its climate. It has been suggested that icy planets and moons become habitable after their initial ice shield melts as their host stars brighten. Here we show from global climate model simulations that a habitable state is not achieved in the climatic evolution of those icy planets and moons that possess an inactive carbonate-silicate cycle and low concentrations of greenhouse gases. Examples for such planetary bodies are the icy moons Europa and Enceladus, and certain icy exoplanets orbiting G and F stars. We find that the stellar fluxes that are required to overcome a planet's initial snowball state are so large that they lead to significant water loss and preclude a habitable planet. Specifically, they exceed the moist greenhouse limit, at which water vapour accumulates at high altitudes where it can readily escape, or the runaway greenhouse limit, at which the strength of the greenhouse increases until the oceans boil away. We suggest that some icy planetary bodies may transition directly to a moist or runaway greenhouse without passing through a habitable Earth-like state.

Star Masses and Star-Planet Distances for Earth-like Habitability.

PubMed

Waltham, David

2017-01-01

This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M ⊙ < M < 1.04 M ⊙ , and the range for planets with at least simple life is 0.57 M ⊙  < M < 1.64 M ⊙ . Key Words: Habitability-Habitable zone-Anthropic-Red dwarfs-Initial mass function. Astrobiology 17, 61-77.

Star Masses and Star-Planet Distances for Earth-like Habitability

PubMed Central

2017-01-01

Abstract This paper presents statistical estimates for the location and duration of habitable zones (HZs) around stars of different mass. The approach is based upon the assumption that Earth's location, and the Sun's mass, should not be highly atypical of inhabited planets. The results support climate-model-based estimates for the location of the Sun's HZ except models giving a present-day outer-edge beyond 1.64 AU. The statistical approach also demonstrates that there is a habitability issue for stars smaller than 0.65 solar masses since, otherwise, Earth would be an extremely atypical inhabited world. It is difficult to remove this anomaly using the assumption that poor habitability of planets orbiting low-mass stars results from unfavorable radiation regimes either before, or after, their stars enter the main sequence. However, the anomaly is well explained if poor habitability results from tidal locking of planets in the HZs of small stars. The expected host-star mass for planets with intelligent life then has a 95% confidence range of 0.78 M⊙ < M < 1.04 M⊙, and the range for planets with at least simple life is 0.57 M⊙ < M < 1.64 M⊙. Key Words: Habitability—Habitable zone—Anthropic—Red dwarfs—Initial mass function. Astrobiology 17, 61–77. PMID:28103107

M stars as targets for terrestrial exoplanet searches and biosignature detection.

PubMed

Scalo, John; Kaltenegger, Lisa; Segura, Antígona; Segura, Ant Gona; Fridlund, Malcolm; Ribas, Ignasi; Kulikov, Yu N; Grenfell, John L; Rauer, Heike; Odert, Petra; Leitzinger, Martin; Selsis, F; Khodachenko, Maxim L; Eiroa, Carlos; Kasting, Jim; Lammer, Helmut

2007-02-01

The changing view of planets orbiting low mass stars, M stars, as potentially hospitable worlds for life and its remote detection was motivated by several factors, including the demonstration of viable atmospheres and oceans on tidally locked planets, normal incidence of dust disks, including debris disks, detection of planets with masses in the 5-20 M() range, and predictions of unusually strong spectral biosignatures. We present a critical discussion of M star properties that are relevant for the long- and short-term thermal, dynamical, geological, and environmental stability of conventional liquid water habitable zone (HZ) M star planets, and the advantages and disadvantages of M stars as targets in searches for terrestrial HZ planets using various detection techniques. Biological viability seems supported by unmatched very long-term stability conferred by tidal locking, small HZ size, an apparent short-fall of gas giant planet perturbers, immunity to large astrosphere compressions, and several other factors, assuming incidence and evolutionary rate of life benefit from lack of variability. Tectonic regulation of climate and dynamo generation of a protective magnetic field, especially for a planet in synchronous rotation, are important unresolved questions that must await improved geodynamic models, though they both probably impose constraints on the planet mass. M star HZ terrestrial planets must survive a number of early trials in order to enjoy their many Gyr of stability. Their formation may be jeopardized by an insufficient initial disk supply of solids, resulting in the formation of objects too small and/or dry for habitability. The small empirical gas giant fraction for M stars reduces the risk of formation suppression or orbit disruption from either migrating or nonmigrating giant planets, but effects of perturbations from lower mass planets in these systems are uncertain. During the first approximately 1 Gyr, atmospheric retention is at peril because of intense and frequent stellar flares and sporadic energetic particle events, and impact erosion, both enhanced, the former dramatically, for M star HZ semimajor axes. Loss of atmosphere by interactions with energetic particles is likely unless the planetary magnetic moment is sufficiently large. For the smallest stellar masses a period of high planetary surface temperature, while the parent star approaches the main sequence, must be endured. The formation and retention of a thick atmosphere and a strong magnetic field as buffers for a sufficiently massive planet emerge as prerequisites for an M star planet to enter a long period of stability with its habitability intact. However, the star will then be subjected to short-term fluctuations with consequences including frequent unpredictable variation in atmospheric chemistry and surficial radiation field. After a review of evidence concerning disks and planets associated with M stars, we evaluate M stars as targets for future HZ planet search programs. Strong advantages of M stars for most approaches to HZ detection are offset by their faintness, leading to severe constraints due to accessible sample size, stellar crowding (transits), or angular size of the HZ (direct imaging). Gravitational lensing is unlikely to detect HZ M star planets because the HZ size decreases with mass faster than the Einstein ring size to which the method is sensitive. M star Earth-twin planets are predicted to exhibit surprisingly strong bands of nitrous oxide, methyl chloride, and methane, and work on signatures for other climate categories is summarized. The rest of the paper is devoted to an examination of evidence and implications of the unusual radiation and particle environments for atmospheric chemistry and surface radiation doses, and is summarized in the Synopsis. We conclude that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations. A detection or repeated nondetections could provide a unique opportunity to partially answer a fundamental and recurrent question about the relation between stability and complexity, one that is not addressed by remote detection from a planet orbiting a solar-like star, and can only be studied on Earth using restricted microbial systems in serial evolution experiments or in artificial life simulations. This proposal requires a planet that has retained its atmosphere and a water supply. The discussion given here suggests that observations of M star exoplanets can decide this latter question with only slight modifications to plans already in place for direct imaging terrestrial exoplanet missions.