Are Giant Planet Satellites Mini-solar Systems?

NASA Astrophysics Data System (ADS)

Mosqueira, I.; Estrada, P. R.

2003-12-01

The regular satellites of Jupiter and Saturn exhibit a number of characteristics strongly suggestive of formation in a thin (aspect ratio H/r ˜ 0.1) circumplanetary gas disk (Mosqueira and Estrada 2003a). Also, the mass ratio of the largest satellites to the primary μ ˜ 10-4 lead one to think of these satellite systems as scaled-down solar systems. Yet, the larger mass ratio for the giant planets to the primary μ ˜ 10-3 appears to limit the usefulness of the planet-satellite analogy. If gap-opening determines the final size of at least Jupiter (Lin and Papaloizou 1993), then significantly smaller objects would be unable to truncate the disk. There are, however, at least two significant difficulties with this point of view. First, the non-linear or thermal gap-opening criterion (Lin and Papaloizou 1993) does not yield a Jupiter mass. Second, the migration timescale due to planet-disk interactions (Ward 1997) is too fast for the formation of giant planets through the core accretion process (Pollack et. al 1996) despite recent work which has lengthened it by up to an order of magnitude (Tanaka et al. 2002, D'Angelo et al. 2002, Bate et al. 2003). An alternative viewpoint has accretion taking place in a weakly turbulent disk, and the survival of both planets and satellites a direct consequence of gap-opening. In this view at least the largest satellites (Mosqueira and Estrada 2003b) and planetary cores ( ˜ 10 M⊕ ; Rafikov 2002) were able to open gaps in the disk. However, because the waves launched by such pertubers do not become non-linear immediately, the gap begins to form a distance away from the perturber given by the shocking length of acoustic waves (Goodman and Rafikov 2001; Rafikov 2002). Estrada and Mosqueira (2003) have suggested that the annulus of material adjacent to the proto-planet that immediately precedes the runaway gas accretion phase (Pollack et al. 1996) can be used to provide the mass needed to lead to the formation of a giant planet. If

VizieR Online Data Catalog: AO imaging of KOIs with gas giant planets (Wang+, 2015)

NASA Astrophysics Data System (ADS)

Wang, J.; Fischer, D. A.; Horch, E. P.; Xie, J.-W.

2017-09-01

From the NASA Exoplanet Archive (http://exoplanetarchive.ipac.caltech.edu), we select Kepler Objects of Interest (KOIs) that satisfy the following criteria: (1) disposition of either Candidate or Confirmed, (2) stellar effective temperature (Teff) lower than 6500 K, (3) stellar surface gravity (log g) higher than 4.0, (4) Kepler magnitude (KP) brighter than 14th mag, (5) with at least one gas giant planet (3.8 R{earth}=gas giant planets. Stellar and orbital parameters for these KOIs are given in Table 1. The median distance of these KOIs is 580 pc. There are 27 multi-planet systems among 84 KOIs. (2 data files).

Migration of Gas Giant Planets in Gravitationally Unstable Disks

NASA Astrophysics Data System (ADS)

Michael, Scott; Durisen, Richard H.; Boley, Aaron C.

2011-08-01

Characterization of migration in gravitationally unstable disks is necessary to understand the fate of protoplanets formed by disk instability. As part of a larger study, we are using a three-dimensional radiative hydrodynamics code to investigate how an embedded gas giant planet interacts with a gas disk that undergoes gravitational instabilities (GIs). This Letter presents results from simulations with a Jupiter-mass planet placed in orbit at 25 AU within a 0.14 M sun disk. The disk spans 5-40 AU around a 1 M sun star and is initially marginally unstable. In one simulation, the planet is inserted prior to the eruption of GIs; in another, it is inserted only after the disk has settled into a quasi-steady GI-active state, where heating by GIs roughly balances radiative cooling. When the planet is present from the beginning, its own wake stimulates growth of a particular global mode with which it strongly interacts, and the planet plunges inward 6 AU in about 103 years. In both cases with embedded planets, there are times when the planet's radial motion is slow and varies in direction. At other times, when the planet appears to be interacting with strong spiral modes, migration both inward and outward can be relatively rapid, covering several AUs over hundreds of years. Migration in both cases appears to stall near the inner Lindblad resonance of a dominant low-order mode. Planet orbit eccentricities fluctuate rapidly between about 0.02 and 0.1 throughout the GI-active phases of the simulations.

Capture of terrestrial-sized moons by gas giant planets.

PubMed

Williams, Darren M

2013-04-01

Terrestrial moons with masses >0.1 M (symbol in text) possibly exist around extrasolar giant planets, and here we consider the energetics of how they might form. Binary-exchange capture can occur if a binary-terrestrial object (BTO) is tidally disrupted during a close encounter with a giant planet and one of the binary members is ejected while the other remains as a moon. Tidal disruption occurs readily in the deep gravity wells of giant planets; however, the large encounter velocities in the wells make binary exchange more difficult than for planets of lesser mass. In addition, successful capture favors massive binaries with large rotational velocities and small component mass ratios. Also, since the interaction tends to leave the captured moons on highly elliptical orbits, permanent capture is only possible around planets with sizable Hill spheres that are well separated from their host stars.

Reinflating Giant Planets

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-01-01

Two new, large gas-giant exoplanets have been discovered orbiting close to their host stars. A recent study examining these planets and others like them may help us to better understand what happens to close-in hot Jupiters as their host stars reach the end of their main-sequence lives.OversizedGiantsUnbinned transit light curves for HAT-P-65b. [Adapted from Hartman et al. 2016]The discovery of HAT-P-65b and HAT-P-66b, two new transiting hot Jupiters, is intriguing. These planets have periods of just under 3 days and masses of roughly 0.5 and 0.8 times that of Jupiter, but their sizes are whats really interesting: they have inflated radii of 1.89 and 1.59 times that of Jupiter.These two planets, discovered using the Hungarian-made Automated Telescope Network (HATNet) in Arizona and Hawaii, mark the latest in an ever-growing sample of gas-giant exoplanets with radii larger than expected based on theoretical planetary structure models.What causes this discrepancy? Did the planets just fail to contract to the expected size when they were initially formed, or were they reinflated later in their lifetimes? If the latter, how? These are questions that scientists are only now starting to be able to address using statistics of the sample of close-in, transiting planets.Unbinned transit light curves for HAT-P-66b. [Hartman et al. 2016]Exploring Other PlanetsLed by Joel Hartman (Princeton University), the team that discovered HAT-P-65b and HAT-P-66b has examined these planets observed parameters and those of dozens of other known close-in, transiting exoplanets discovered with a variety of transiting exoplanet missions: HAT, WASP, Kepler, TrES, and KELT. Hartman and collaborators used this sample to draw conclusions about what causes some of these planets to have such large radii.The team found that there is a statistically significant correlation between the radii of close-in giant planets and the fractional ages of their host stars (i.e., the stars age divided by its full

Possible Rapid Gas Giant Planet Formation in the Solar Nebula and Other Protoplanetary Disks.

PubMed

Boss

2000-06-20

Gas giant planets have been detected in orbit around an increasing number of nearby stars. Two theories have been advanced for the formation of such planets: core accretion and disk instability. Core accretion, the generally accepted mechanism, requires several million years or more to form a gas giant planet in a protoplanetary disk like the solar nebula. Disk instability, on the other hand, can form a gas giant protoplanet in a few hundred years. However, disk instability has previously been thought to be important only in relatively massive disks. New three-dimensional, "locally isothermal," hydrodynamical models without velocity damping show that a disk instability can form Jupiter-mass clumps, even in a disk with a mass (0.091 M middle dot in circle within 20 AU) low enough to be in the range inferred for the solar nebula. The clumps form with initially eccentric orbits, and their survival will depend on their ability to contract to higher densities before they can be tidally disrupted at successive periastrons. Because the disk mass in these models is comparable to that apparently required for the core accretion mechanism to operate, the models imply that disk instability could obviate the core accretion mechanism in the solar nebula and elsewhere.

On the Radii of Close-in Giant Planets.

PubMed

Burrows; Guillot; Hubbard; Marley; Saumon; Lunine; Sudarsky

2000-05-01

The recent discovery that the close-in extrasolar giant planet HD 209458b transits its star has provided a first-of-its-kind measurement of the planet's radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet tau Bootis b. Including the effects of stellar irradiation, we estimate the general behavior of radius/age trajectories for such planets and interpret the large measured radii of HD 209458b and tau Boo b in that context. We find that HD 209458b must be a hydrogen-rich gas giant. Furthermore, the large radius of a close-in gas giant is not due to the thermal expansion of its atmosphere but to the high residual entropy that remains throughout its bulk by dint of its early proximity to a luminous primary. The large stellar flux does not inflate the planet but retards its otherwise inexorable contraction from a more extended configuration at birth. This implies either that such a planet was formed near its current orbital distance or that it migrated in from larger distances (>/=0.5 AU), no later than a few times 107 yr of birth.

Growing the gas-giant planets by the gradual accumulation of pebbles

NASA Astrophysics Data System (ADS)

Levison, Harold F.; Kretke, Katherine A.; Duncan, Martin J.

2015-08-01

It is widely held that the first step in forming gas-giant planets, such as Jupiter and Saturn, was the production of solid `cores' each with a mass roughly ten times that of the Earth. Getting the cores to form before the solar nebula dissipates (in about one to ten million years; ref. 3) has been a major challenge for planet formation models. Recently models have emerged in which `pebbles' (centimetre-to-metre-sized objects) are first concentrated by aerodynamic drag and then gravitationally collapse to form objects 100 to 1,000 kilometres in size. These `planetesimals' can then efficiently accrete left-over pebbles and directly form the cores of giant planets. This model is known as `pebble accretion' theoretically, it can produce cores of ten Earth masses in only a few thousand years. Unfortunately, full simulations of this process show that, rather than creating a few such cores, it produces a population of hundreds of Earth-mass objects that are inconsistent with the structure of the Solar System. Here we report that this difficulty can be overcome if pebbles form slowly enough to allow the planetesimals to gravitationally interact with one another. In this situation, the largest planetesimals have time to scatter their smaller siblings out of the disk of pebbles, thereby stifling their growth. Our models show that, for a large and physically reasonable region of parameter space, this typically leads to the formation of one to four gas giants between 5 and 15 astronomical units from the Sun, in agreement with the observed structure of the Solar System.

Planetary Formation: From the Earth and Moon to Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Lissauer, Jack; DeVincenzi, Donald (Technical Monitor)

1999-01-01

An overview of current theories of star and planet formation is presented. These models are based upon observations of the Solar System and of young stars and their environments. They 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 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. Specific issues to be discussed include: (1) how large a solid core is needed to initiate rapid accumulation of gas? (2) can giant planets form very close to stars? (3) could a giant impact leading to lunar formation have occurred approximately 100 million years after the condensation of the oldest meteorites?

Planetary Formation: From the Earth and Moon to Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

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

1999-01-01

An overview of current theories of star and planet formation is presented. These models are based upon observations of the Solar System and of young stars and their environments. They 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 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. Specific issues to be discussed include: (1) how large a solid core is needed to initiate rapid accumulation of gas? (2) can giant planets form very close to stars? (3) could a giant impact leading to lunar formation have occurred approx. 100 million years after the condensation of the oldest meteorites?

Survival of a proto-atmosphere through the stage of giant impacts: the mechanical aspects

NASA Astrophysics Data System (ADS)

Genda, Hidenori; Abe, Yutaka

2003-07-01

When a giant impact occurs, atmosphere loss may occur due to global ground motion excited by a strong shock wave traveling in the planetary interior. Here, the relations between the ground motion and the amount of the lost atmosphere are systematically investigated through calculations of a spherically one-dimensional atmospheric motion for various initial atmospheric conditions. The fraction of the lost atmosphere to the total mass of the atmosphere is found to be controlled only by the ground velocity and, insensitive to the initial atmospheric conditions. Unlike the previous studies (Ahrens, 1990, Origin of the Earth, H.E. Newson, J.H. Jones (Eds.), pp. 211-227; Ahrens, 1993, Annu. Rev. Earth Planet. Sci. 21, 525-555; Chen and Ahrens, 1997, Phys. Earth Planet. Inter. 100, 21-26); the estimated loss fraction for the giant impact is only 20%. Significant escape occurs only when the ground velocity is close to the escape velocity. Thus, most of the atmosphere should survive the giant impact. The cause of the difference from previous estimates is discussed from energetic and dynamic points of view. Moreover, if our estimates are applied to the atmosphere of the impactor planet, a significant fraction of it is carried to the target planet. Survival of the proto-atmosphere has very important effects on the origin and evolution of the terrestrial planets' volatile budget.

Migration of accreting giant planets

NASA Astrophysics Data System (ADS)

Robert, C.; Crida, A.; Lega, E.; Méheut, H.

2017-09-01

Giant planets forming in protoplanetary disks migrate relative to their host star. By repelling the gas in their vicinity, they form gaps in the disk's structure. If they are effectively locked in their gap, it follows that their migration rate is governed by the accretion of the disk itself onto the star, in a so-called type II fashion. Recent results showed however that a locking mechanism was still lacking, and was required to understand how giant planets may survive their disk. We propose that planetary accretion may play this part, and help reach this slow migration regime.

The SEEDs of Planet Formation: Indirect Signatures of Giant Planets in Transitional Disks

NASA Technical Reports Server (NTRS)

Grady, Carol; Currie, T.

2012-01-01

We live in a planetary system with 2 gas giant planets, and as a resu lt of RV, transit, microlensing, and transit timing studies have ide ntified hundreds of giant planet candidates in the past 15 years. Su ch studies have preferentially concentrated on older, low activity So lar analogs, and thus tell us little about .when, where, and how gian t planets form in their disks, or how frequently they form in disks associated with intermediate-mass stars.

Evidence of an Upper Bound on the Masses of Planets and Its Implications for Giant Planet Formation

NASA Astrophysics Data System (ADS)

Schlaufman, Kevin C.

2018-01-01

Celestial bodies with a mass of M≈ 10 {M}{Jup} have been found orbiting nearby stars. It is unknown whether these objects formed like gas-giant planets through core accretion or like stars through gravitational instability. I show that objects with M≲ 4 {M}{Jup} orbit metal-rich solar-type dwarf stars, a property associated with core accretion. Objects with M≳ 10 {M}{Jup} do not share this property. This transition is coincident with a minimum in the occurrence rate of such objects, suggesting that the maximum mass of a celestial body formed through core accretion like a planet is less than 10 {M}{Jup}. Consequently, objects with M≳ 10 {M}{Jup} orbiting solar-type dwarf stars likely formed through gravitational instability and should not be thought of as planets. Theoretical models of giant planet formation in scaled minimum-mass solar nebula Shakura–Sunyaev disks with standard parameters tuned to produce giant planets predict a maximum mass nearly an order of magnitude larger. To prevent newly formed giant planets from growing larger than 10 {M}{Jup}, protoplanetary disks must therefore be significantly less viscous or of lower mass than typically assumed during the runaway gas accretion stage of giant planet formation. Either effect would act to slow the Type I/II migration of planetary embryos/giant planets and promote their survival. These inferences are insensitive to the host star mass, planet formation location, or characteristic disk dissipation time.

On the Terminal Rotation Rates of Giant Planets

NASA Astrophysics Data System (ADS)

Batygin, Konstantin

2018-04-01

Within the general framework of the core-nucleated accretion theory of giant planet formation, the conglomeration of massive gaseous envelopes is facilitated by a transient period of rapid accumulation of nebular material. While the concurrent build-up of angular momentum is expected to leave newly formed planets spinning at near-breakup velocities, Jupiter and Saturn, as well as super-Jovian long-period extrasolar planets, are observed to rotate well below criticality. In this work, we demonstrate that the large luminosity of a young giant planet simultaneously leads to the generation of a strong planetary magnetic field, as well as thermal ionization of the circumplanetary disk. The ensuing magnetic coupling between the planetary interior and the quasi-Keplerian motion of the disk results in efficient braking of planetary rotation, with hydrodynamic circulation of gas within the Hill sphere playing the key role of expelling spin angular momentum to the circumstellar nebula. Our results place early-stage giant planet and stellar rotation within the same evolutionary framework, and motivate further exploration of magnetohydrodynamic phenomena in the context of the final stages of giant planet formation.

Giant planet magnetospheres

NASA Technical Reports Server (NTRS)

Bagenal, Fran

1992-01-01

The classification of the giant planet magnetospheres into two varieties is examined: the large symmetric magnetospheres of Jupiter and Saturn and the smaller irregular ones of Uranus and Neptune. The characteristics of the plasma and the current understanding of the magnetospheric processes are considered for each planet. The energetic particle populations, radio emissions, and remote sensing of magnetospheric processes in the giant planet magneotospheres are discussed.

On the Possibility of Enrichment and Differentiation in Gas Giants During Birth by Disk Instability

NASA Astrophysics Data System (ADS)

Boley, Aaron C.; Durisen, Richard H.

2010-11-01

We investigate the coupling between rock-size solids and gas during the formation of gas giant planets by disk fragmentation in the outer regions of massive disks. In this study, we use three-dimensional radiative hydrodynamic simulations and model solids as a spatial distribution of particles. We assume that half of the total solid fraction is in small grains and half in large solids. The former are perfectly entrained with the gas and set the opacity in the disk, while the latter are allowed to respond to gas drag forces, with the back reaction on the gas taken into account. To explore the maximum effects of gas-solid interactions, we first consider 10 cm size particles. We then compare these results to a simulation with 1 km size particles, which explores the low-drag regime. We show that (1) disk instability planets have the potential to form large cores due to aerodynamic capturing of rock-size solids in spiral arms before fragmentation; (2) temporary clumps can concentrate tens of M ⊕ of solids in very localized regions before clump disruption; (3) the formation of permanent clumps, even in the outer disk, is dependent on the grain-size distribution, i.e., the opacity; (4) nonaxisymmetric structure in the disk can create disk regions that have a solids-to-gas ratio greater than unity; (5) the solid distribution may affect the fragmentation process; (6) proto-gas giants and proto-brown dwarfs can start as differentiated objects prior to the H2 collapse phase; (7) spiral arms in a gravitationally unstable disk are able to stop the inward drift of rock-size solids, even redistributing them to larger radii; and (8) large solids can form spiral arms that are offset from the gaseous spiral arms. We conclude that planet embryo formation can be strongly affected by the growth of solids during the earliest stages of disk accretion.

Thermodynamics of giant planet formation: shocking hot surfaces on circumplanetary discs

NASA Astrophysics Data System (ADS)

Szulágyi, J.; Mordasini, C.

2017-02-01

The luminosity of young giant planets can inform about their formation and accretion history. The directly imaged planets detected so far are consistent with the `hot-start' scenario of high entropy and luminosity. If nebular gas passes through a shock front before being accreted into a protoplanet, the entropy can be substantially altered. To investigate this, we present high-resolution, three-dimensional radiative hydrodynamic simulations of accreting giant planets. The accreted gas is found to fall with supersonic speed in the gap from the circumstellar disc's upper layers on to the surface of the circumplanetary disc and polar region of the protoplanet. There it shocks, creating an extended hot supercritical shock surface. This shock front is optically thick; therefore, it can conceal the planet's intrinsic luminosity beneath. The gas in the vertical influx has high entropy which when passing through the shock front decreases significantly while the gas becomes part of the disc and protoplanet. This shows that circumplanetary discs play a key role in regulating a planet's thermodynamic state. Our simulations furthermore indicate that around the shock surface extended regions of atomic - sometimes ionized - hydrogen develop. Therefore, circumplanetary disc shock surfaces could influence significantly the observational appearance of forming gas giants.

The Effects of Gravitational Instabilities on Gas Giant Planet Migration in Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Michael, Scott A.; Durisen, R. H.

2010-05-01

In this paper we conduct several three-dimensional radiative hydrodynamic simulations to explore the effect of the inclusion of gas giant planets in gravitationally unstable protoplanetary disks. We compare several simulations carried out with the CHYMERA code including: a baseline simulation without a planet, and three simulations including planets of various masses 0.3, 1 and 3 Jupiter masses. The planets are inserted into the baseline simulation after the gravitational instabilities (GIs) have grown to non-linear amplitude. The planets are inserted at the same radius, which coincides with the co-rotation radius of the dominant global mode in the baseline simulation. We examine the effect that the GIs have on migration rates as well as the potential of halting inward migration. We also examine the effect the insertion of the planet has on the global torques caused by the GIs. Furthermore, we explore the relationship between planet mass and migration rates and effect on GIs.

Photoevaporation Does Not Create a Pileup of Giant Planets at 1 au

NASA Astrophysics Data System (ADS)

Wise, A. W.; Dodson-Robinson, S. E.

2018-03-01

The semimajor axis distribution of giant exoplanets appears to have a pileup near 1 au. Photoevaporation opens a gap in the inner few au of gaseous disks before dissipating them. Here, we investigate if photoevaporation can significantly affect the final distribution of giant planets by modifying gas surface density and hence Type II migration rates near the photoevaporation gap. We first use an analytic disk model to demonstrate that newly formed giant planets have a long migration epoch before photoevaporation can significantly alter their migration rates. Next, we present new 2D hydrodynamic simulations of planets migrating in photoevaporating disks, in which each are paired with a control simulation of migration in an otherwise identical disk without photoevaporation. We show that in disks with surface densities near the minimum threshold for forming giant planets, photoevaporation alters the final semimajor axis of a migrating gas giant by at most 5% over the course of 0.1 Myr of migration. Once the disk mass has become low enough for photoevaporation to carve a sharp gap, migration has almost completely stalled due to the low surface density of gas at the Lindblad resonances. We find that photoevaporation modifies migration rates so little that it is unlikely to leave a significant signature on the distribution of giant exoplanets.

Hot-start Giant Planets Form with Radiative Interiors

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

Berardo, David; Cumming, Andrew, E-mail: david.berardo@mcgill.ca, E-mail: andrew.cumming@mcgill.ca

In the hot-start core accretion formation model for gas giants, the interior of a planet is usually assumed to be fully convective. By calculating the detailed internal evolution of a planet assuming hot-start outer boundary conditions, we show that such a planet will in fact form with a radially increasing internal entropy profile, so that its interior will be radiative instead of convective. For a hot outer boundary, there is a minimum value for the entropy of the internal adiabat S {sub min} below which the accreting envelope does not match smoothly onto the interior, but instead deposits high entropymore » material onto the growing interior. One implication of this would be to at least temporarily halt the mixing of heavy elements within the planet, which are deposited by planetesimals accreted during formation. The compositional gradient this would impose could subsequently disrupt convection during post-accretion cooling, which would alter the observed cooling curve of the planet. However, even with a homogeneous composition, for which convection develops as the planet cools, the difference in cooling timescale will change the inferred mass of directly imaged gas giants.« less

Kuiper Prize: Giant Planet Atmospheres

NASA Astrophysics Data System (ADS)

Ingersoll, Andrew P.

2007-10-01

The study of giant planet atmospheres is near and dear to me, for several reasons. First, the giant planets are photogenic; the colored clouds are great tracers, and one can make fantastic movies of the atmosphere in motion. Second, the giant planets challenge us with storms that last for hundreds of years and winds that blow faster the farther you go from the sun. Third, they remind us of Earth with their hurricanes, auroras, and lightning, but they also are the link to the 200 giant planets that have been discovered around other stars. This talk will cover the past, present, and future (one hopes) of giant planet research. I will review the surprises of the Voyager and Galileo eras, and will discuss what we are learning now from the Cassini orbiter. I will review the prospects for answering the outstanding questions like: Where's the water? What is providing the colors of the clouds? How deep do the features extend? Where do the winds get their energy? What is the role of the magnetic field? Finally, I will briefly discuss how extrasolar giant planets compare with objects in our own solar system.

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.

EFFECTS OF DYNAMICAL EVOLUTION OF GIANT PLANETS ON SURVIVAL OF TERRESTRIAL PLANETS

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

Matsumura, Soko; Ida, Shigeru; Nagasawa, Makiko

2013-04-20

The orbital distributions of currently observed extrasolar giant planets allow marginally stable orbits for hypothetical, terrestrial planets. In this paper, we propose that many of these systems may not have additional planets on these ''stable'' orbits, since past dynamical instability among giant planets could have removed them. We numerically investigate the effects of early evolution of multiple giant planets on the orbital stability of the inner, sub-Neptune-like planets which are modeled as test particles, and determine their dynamically unstable region. Previous studies have shown that the majority of such test particles are ejected out of the system as a resultmore » of close encounters with giant planets. Here, we show that secular perturbations from giant planets can remove test particles at least down to 10 times smaller than their minimum pericenter distance. Our results indicate that, unless the dynamical instability among giant planets is either absent or quiet like planet-planet collisions, most test particles down to {approx}0.1 AU within the orbits of giant planets at a few AU may be gone. In fact, out of {approx}30% of survived test particles, about three quarters belong to the planet-planet collision cases. We find a good agreement between our numerical results and the secular theory, and present a semi-analytical formula which estimates the dynamically unstable region of the test particles just from the evolution of giant planets. Finally, our numerical results agree well with the observations, and also predict the existence of hot rocky planets in eccentric giant planet systems.« less

Exploring the Relationship Between Planet Mass and Atmospheric Metallicity for Cool Giant Planets

NASA Astrophysics Data System (ADS)

Thomas, Nancy H.; Wong, Ian; Knutson, Heather; Deming, Drake; Desert, Jean-Michel; Fortney, Jonathan J.; Morley, Caroline; Kammer, Joshua A.; Line, Michael R.

2016-10-01

Measurements of the average densities of exoplanets have begun to help constrain their bulk compositions and to provide insight into their formation locations and accretionary histories. Current mass and radius measurements suggest an inverse relationship between a planet's bulk metallicity and its mass, a relationship also seen in the gas and ice giant planets of our own solar system. We expect atmospheric metallicity to similarly increase with decreasing planet mass, but there are currently few constraints on the atmospheric metallicities of extrasolar giant planets. For hydrogen-dominated atmospheres, equilibrium chemistry models predict a transition from CO to CH4 below ~1200 K. However, with increased atmospheric metallicity the relative abundance of CH4 is depleted and CO is enhanced. In this study we present new secondary eclipse observations of a set of cool (<1200 K) giant exoplanets at 3.6 and 4.5 microns using the Spitzer Space Telescope, which allow us to constrain their relative abundances of CH4 and CO and corresponding atmospheric metallicities. We discuss the implications of our results for the proposed correlation between planet mass and atmospheric metallicity as predicted by the core accretion models and observed in our solar system.

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

The Giant Planet Satellite Exospheres

NASA Technical Reports Server (NTRS)

McGrath, Melissa A.

2014-01-01

Exospheres are relatively common in the outer solar system among the moons of the gas giant planets. They span the range from very tenuous, surface-bounded exospheres (e.g., Rhea, Dione) to quite robust exospheres with exobase above the surface (e.g., lo, Triton), and include many intermediate cases (e.g., Europa, Ganymede, Enceladus). The exospheres of these moons exhibit an interesting variety of sources, from surface sputtering, to frost sublimation, to active plumes, and also well illustrate another common characteristic of the outer planet satellite exospheres, namely, that the primary species often exists both as a gas in atmosphere, and a condensate (frost or ice) on the surface. As described by Yelle et al. (1995) for Triton, "The interchange of matter between gas and solid phases on these bodies has profound effects on the physical state of the surface and the structure of the atmosphere." A brief overview of the exospheres of the outer planet satellites will be presented, including an inter-comparison of these satellites exospheres with each other, and with the exospheres of the Moon and Mercury.

Giant planets: Clues on current and past organic chemistry in the outer solar system

NASA Technical Reports Server (NTRS)

Pollack, James B.; Atreya, Sushil K.

1992-01-01

The giant planets of the outer solar system - Jupiter, Saturn, Uranus, and Neptune - were formed in the same flattened disk of gas and dust, the solar nebula, as the terrestrial planets were. Yet, the giant planets differ in some very fundamental ways from the terrestrial planets. Despite enormous differences, the giant planets are relevant to exobiology in general and the origin of life on the Earth in particular. The giant planets are described as they are today. Their basic properties and the chemistry occurring in their atmospheres is discussed. Theories of their origin are explored and aspects of these theories that may have relevance to exobiology and the origin of life on Earth are stressed.

Isotopic ratios D/H and 15N/14N in giant planets

NASA Astrophysics Data System (ADS)

Marboeuf, Ulysse; Thiabaud, Amaury; Alibert, Yann; Benz, Willy

2018-04-01

The determination of isotopic ratios in planets is important since it allows us to investigate the origins and initial composition of materials. The present work aims to determine the possible range of values for isotopic ratios D/H and 15N/14N in giant planets. The main objective is to provide valuable theoretical assumptions on the isotopic composition of giant planets, their internal structure, and the main reservoirs of species. We use models of ice formation and planet formation that compute the composition of ices and gas accreted in the core and the envelope of planets. Assuming a single initial value for isotopic ratios in volatile species, and disruption of planetesimals in the envelope of gaseous planets, we obtain a wide variety of D/H and 15N/14N ratios in low-mass planets (≤100 Mearth) due to the migration pathway of planets, the accretion time of gas species whose relative abundance evolves with time, and isotope exchanges among species. If giant planets with mass greater than 100 Mearth have solar isotopic ratios such as Jupiter and Saturn due to their higher envelope mass, Neptune-type planets present values ranging between one and three times the solar value. It seems therefore difficult to use isotopic ratios in the envelope of these planets to get information about their formation in the disc. For giant planets, the ratios allow us to constrain the mass fraction of volatile species in the envelope needed to reproduce the observational data by assuming initial values for isotopic ratios in volatile species.

Gap opening by gas accretion and influence on planet populations

NASA Astrophysics Data System (ADS)

Crida, A.; Bitsch, B.; Ndugu, N.; Morbidelli, A.

2017-09-01

Giant planets grow and migrate in protoplanetary disks. Because they accrete gas from their horseshoe region until the latter is depleted, we find that giant planets can open a gap before being lost into their central star by type I migration. A reduced type II migration is then enough and necessary to limit the total amount of migration that a giant planet suffers during its formation.

Planetesimal dissolution in the envelopes of the forming, giant planets

NASA Technical Reports Server (NTRS)

Pollack, J. B.; Podolak, M.; Bodenheimer, P.; Christofferson, B.

1986-01-01

An evaluation is made of the capacity of planetesimals to penetrate the envelopes of giant planets during their growth phase, by means of a core instability mechanism in which the growing core becomes gradually more adept in the gravitational concentration of gas from its solar nebula environment, until a runaway gas accretion occurs. If most of the accreted mass is contained in planetesimals larger that about 1 km, the critical core mass for runaway accretion will not significantly change when planetesimal dissolution is taken into account; it is accordingly suggested that giant planet envelopes should contain above-solar proportions of virtually all elements, relative to hydrogen.

MISCIBILITY CALCULATIONS FOR WATER AND HYDROGEN IN GIANT PLANETS

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

Soubiran, François; Militzer, Burkhard

2015-06-20

We present results from ab initio simulations of liquid water–hydrogen mixtures in the range from 2 to 70 GPa and from 1000 to 6000 K, covering conditions in the interiors of ice giant planets and parts of the outer envelope of gas giant planets. In addition to computing the pressure and the internal energy, we derive the Gibbs free energy by performing a thermodynamic integration. For all conditions under consideration, our simulations predict hydrogen and water to mix in all proportions. The thermodynamic behavior of the mixture can be well described with an ideal mixing approximation. We suggest that amore » substantial fraction of water and hydrogen in giant planets may occur in homogeneously mixed form rather than in separate layers. The extent of mixing depends on the planet’s interior dynamics and its conditions of formation, in particular on how much hydrogen was present when icy planetesimals were delivered. Based on our results, we do not predict water–hydrogen mixtures to phase separate during any stage of the evolution of giant planets. We also show that the hydrogen content of an exoplanet is much higher if the mixed interior is assumed.« less

Giant Planets: Good Neighbors for Habitable Worlds?

NASA Astrophysics Data System (ADS)

Georgakarakos, Nikolaos; Eggl, Siegfried; Dobbs-Dixon, Ian

2018-04-01

The presence of giant planets influences potentially habitable worlds in numerous ways. Massive celestial neighbors can facilitate the formation of planetary cores and modify the influx of asteroids and comets toward Earth analogs later on. Furthermore, giant planets can indirectly change the climate of terrestrial worlds by gravitationally altering their orbits. Investigating 147 well-characterized exoplanetary systems known to date that host a main-sequence star and a giant planet, we show that the presence of “giant neighbors” can reduce a terrestrial planet’s chances to remain habitable, even if both planets have stable orbits. In a small fraction of systems, however, giant planets slightly increase the extent of habitable zones provided that the terrestrial world has a high climate inertia. In providing constraints on where giant planets cease to affect the habitable zone size in a detrimental fashion, we identify prime targets in the search for habitable worlds.

Giant Planets in Open Clusters and Binaries: Observational Constraints on Migration

NASA Astrophysics Data System (ADS)

Quinn, Samuel N.; White, Russel J.; Latham, David W.; Buchhave, Lars A.; Torres, Guillermo

2016-01-01

Some giant planets migrate from their birthplace beyond the ice line to short-period orbits just a fraction of an AU from their host stars. Though many theories have been proposed, it is not yet clear which mechanism is most important for migration, and by extension, in which types of planetary system we can expect a greater prevalence of disruptive gas giant migration. One way to constrain this process is to observe the orbital properties of migrating planets, which are expected to be shaped according to the mode of migration: in general, interaction with the gas disk should produce circular, coplanar orbits, while multi-body processes stir up eccentricities and inclinations. Unfortunately, tidal and magnetic interactions between hot Jupiters and their host stars can obscure these differences by damping eccentricities and inclinations over time, so the most direct constraints will come from difficult-to-observe young systems. Additional constraints on migration can be obtained by observing the architectures of systems containing short-period giant planets: if an outer companion is often responsible for driving migration, there should be a higher incidence of massive companions on wide orbits in hot Jupiter systems than in systems not hosting a short-period giant planet. Further, the properties of these outer companions can help differentiate between multi-body migration mechanisms. We describe two complementary surveys that we have carried out to address these problems. The first, a precise radial-velocity survey in nearby adolescent (100-600 Myr) open clusters, characterizes the orbits of giant planets soon after migration. The second, an adaptive optics imaging survey of hot Jupiter host stars, constrains the population of wide companions in hot Jupiter systems. We present the results from these two surveys and discuss the orbital properties and system architectures of our discoveries in the context of giant planet migration.

On The Possibility of Enrichment and Differentiation in Gas Giants During Birth by Disk Instability

NASA Astrophysics Data System (ADS)

Boley, Aaron C.; Durisen, R. H.

2011-01-01

We investigate the coupling between rock-size solids and gas during the formation of gas giant planets by disk fragmentation in the outer regions of massive disks. In this study, we use three-dimensional radiative hydrodynamics simulations and model solids as a spatial distribution of particles. We assume that half of the total solid fraction is in small grains and half in large solids. The former are perfectly entrained with the gas and set the opacity, while the latter are allowed to respond to gas drag forces. To explore the maximum effects of gas-solid interactions, we first consider 10cm-size particles. We then compare these results to a simulation with 1km-size particles, which explores the low-drag regime.We show that (1) disk instability planets have the potential to form large cores due to aerodynamic capturing of rock-size solids in spiral arms before fragmentation; (2) that temporary clumps can concentrate tens of M⊕ of solids in very localized regions before clump disruption; (3) that the formation of permanent clumps, even in the outer disk, is dependent on the opacity; (4) that nonaxisymmetric structure in the disk can create disk regions that have a solids-to-gas ratio greater than unity; (5) that the solid distribution may affect the fragmentation process; (6) that proto-gas giants and proto-brown dwarfs can start as differentiated objects prior to the H2 collapse phase; (7) that spiral arms in a gravitationally unstable disk are able to stop the inward drift of rock-size solids, even redistributing them to larger radii; and, (8) that large solids can form spiral arms that are offset from the gaseous spiral arms. ACB's support was provided in part under contract with the California Institute of Technology (Caltech) funded by NASA through the Sagan Fellowship Program. RHD was supported by NASA Origins of Solar Systems grant NNX08AK36G.

Giant Planets in Open Clusters

NASA Astrophysics Data System (ADS)

Quinn, S. N.; White, R. J.; Latham, D. W.

2015-10-01

Two decades after the discovery of 51 Peg b, more than 200 hot Jupiters have now been confirmed, but the details of their inward migration remain uncertain. While it is widely accepted that short period giant planets could not have formed in situ, several different mechanisms (e.g., Type II migration, planet-planet scattering, Kozai-Lidov cycles) may contribute to shrinking planetary orbits, and the relative importance of each is not well-constrained. Migration through the gas disk is expected to preserve circular, coplanar orbits and must occur quickly (within ˜ 10 Myr), whereas multi-body processes should initially excite eccentricities and inclinations and may take hundreds of millions of years. Subsequent evolution of the system (e.g., orbital circularization and inclination damping via tidal interaction with the host star) may obscure these differences, so observing hot Jupiters soon after migration occurs can constrain the importance of each mechanism. Fortunately, the well-characterized stars in young and adolescent open clusters (with known ages and compositions) provide natural laboratories for such studies, and recent surveys have begun to take advantage of this opportunity. We present a review of the discoveries in this emerging realm of exoplanet science, discuss the constraints they provide for giant planet formation and migration, and reflect on the future direction of the field.

A Gas-poor Planetesimal Feeding Model for the Formation of Giant Planet Satellite Systems: Disk Size and Formation Timescale

NASA Astrophysics Data System (ADS)

Estrada, P. R.; Mosqueira, I.

2003-05-01

Mosqueira and Estrada (2003a) argue that following giant planet accretion a largely quiescent circumplanetary disk may form with most of the mass inside a radius located outside, but perhaps close to, the centrifugal radius rc = RH/48, where the specific angular momentum of the collapsing giant planet gaseous envelope achieves centrifugal balance, and extending as far as the irregular satellites at RH/5 due to the high specific angular momentum of parcels of gas accreted from distances several times RH during the final stages of planetary growth (Lubow et al. 1999). Provided that allowances are made for the capture of Triton from heliocentric orbit, this picture fits well with the primordial satellite systems of all four giant planets. Because strong gas turbulence would smooth out the gas surface density of the disk, this description can only apply if the turbulence subsides as planetary accretion ceases. Although the viability of a hydrodynamic shear instability in Keplerian disks that can sustain significant post-accretion turbulence and drive evolution of the gas disk is in serious doubt (see Mosqueira et al. this conference), the possibility has not yet been totally ruled out. This leads us to consider gas-poor scenarios that might produce a close-in regular satellite system. To this end, we re-examine the ideas of Safronov et al. (1986) to see whether a gas-free (or nearly gas-free) model can be made consistent with the extent of the regular satellites of the giant planets. In this model, planetesimals containing most of the mass of solids (Mizuno et al. 1978; Weidenschilling 1997) that are de-coupled from the gas and whose dynamics must be followed independently are collisionally captured and form a swarm of circumplanetary objects lasting for perhaps ˜ 106 years. While such a swarm might occupy a significant fraction of the Hill radius of the planet, the small net angular momentum of the swarm might lead to the formation of close-in prograde satellites as

A giant planet imaged in the disk of the young star beta Pictoris.

PubMed

Lagrange, A-M; Bonnefoy, M; Chauvin, G; Apai, D; Ehrenreich, D; Boccaletti, A; Gratadour, D; Rouan, D; Mouillet, D; Lacour, S; Kasper, M

2010-07-02

Here, we show that the approximately 10-million-year-old beta Pictoris system hosts a massive giant planet, beta Pictoris b, located 8 to 15 astronomical units from the star. This result confirms that gas giant planets form rapidly within disks and validates the use of disk structures as fingerprints of embedded planets. Among the few planets already imaged, beta Pictoris b is the closest to its parent star. Its short period could allow for recording of the full orbit within 17 years.

Forming Giant Planet Cores by Pebble Accretion -- Why Slow and Steady wins the Race

NASA Astrophysics Data System (ADS)

Kretke, Katherine A.; Levison, Harold F.

2014-05-01

In recent years there has been a radical new solution proposed to solve the problem of giant planet core formation. "Pebbles", particles ranging from centimeters to meters in size, have been shown to accrete extremely efficiently due to aerodynamic drag. Large capture cross-sections combined with fast pebble drift rates can allow a single planetesimal to grow from Ceres size to 10s of Earth masses well within the lifetime of gaseous circumstellar disks. However, at large sizes, the the capture-cross section of pebbles goes with the Hill sphere, forcing pebble accretion to becomes a fundamentally "oligarchic-like" process. This makes it difficult to form a few giant planet cores; instead a more generic result is many 10s to 100s of competing oligarchs. In this work, we present a way to get around this oligarchic dilemma If pebbles are assumed to form slowly over a long period of time, then the planetesimal growth rates are slow enough for the planetesimals to dynamically excite each other. As the larger planetisimals/proto-planets stir their smaller companions, these smaller bodies are excited to such a degree that they spend only a small fraction of their orbits embedded in the cooler pebble disk. This allows the larger bodies to starve their neighbors and maintain a relative runaway growth rate to high mass, effectively forming the cores of giant planets.

Time for Gas Planets to Grow

NASA Technical Reports Server (NTRS)

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

2001-01-01

Giant planets like Jupiter need a large reservoir of gas to grow to full size. New observations indicate that such planetary nurseries last twice as long as previously thought. These observations, and their implications for the abundance of Jupiter-like planets within our galaxy, are discussed herein.

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.

Formation of Ice Giant Satellites During Thommes Model Mirgration

NASA Astrophysics Data System (ADS)

Fuse, Christopher; Spiegelberg, Josephine

2018-01-01

Inconsistencies between ice giant planet characteristics and classic planet formation theories have led to a re-evaluation of the formation of the outer Solar system. Thommes model migration delivers proto-Uranus and Neptune from orbits interior to Saturn to their current locations. The Thommes model has also been able to reproduce the large Galilean and Saturnian moons via interactions between the proto-ice giants and the gas giant moon disks.As part of a series of investigations examining the effects of Thommes model migration on the formation of moons, N-body simulations of the formation of the Uranian and Neptunian satellite systems were performed. Previous research has yielded conflicting results as to whether satellite systems are stable during planetary migration. Some studies, such as Beaugé (2002) concluded that the system was not stable over the proposed duration of migration. Conversely, Fuse and Neville (2011) and Yokoyama et al. (2011) found that moons were retained, though the nature of the resulting system was heavily influenced by interactions with planetesimals and other large objects. The results of the current study indicate that in situ simulations of the Uranus and Neptune systems can produce stable moons. Whether with current orbital parameters or located at pre-migration, inner Solar system semi-major axes, the simulations end with 5.8 ± 0.15 or 5.9 ± 0.7 regular satellites around Uranus and Neptune, respectively. Preliminary simulations of a proto-moon disk around a single planet migrating via the Thommes model have failed to retain moons. Furthermore, simulations of ejection of the current Uranian satellite system retained at most one moon. Thus, for the Thommes model to be valid, it is likely that moon formation did not begin until after migration ended. Future work will examine the formation of gas and ice giant moons through other migration theories, such as the Nice model (Tsiganis et al. 2006).

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

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.

Polarimetry Of Planetary Atmospheres: From The Solar System Gas Giants To Extrasolar Planets

NASA Astrophysics Data System (ADS)

Buenzli, Esther; Bazzon, A.; Schmid, H. M.

2011-09-01

The polarization of light reflected from a planet provides unique information on the atmosphere structure and scattering properties of particles in the upper atmosphere. The solar system planets show a large variety of atmospheric polarization properties, from the thick, highly polarizing haze on Titan and the poles of Jupiter, Rayleigh scattering by molecules on Uranus and Neptune, to clouds in the equatorial region of Jupiter or on Venus. Polarimetry is also a promising differential technique to search for and characterize extra-solar planets, e.g. with the future VLT planet finder instrument SPHERE. For the preparation of the SPHERE planet search program we have made a suite of polarimetric observations and models for the solar system gas giants. The phase angles for the outer planets are small for Earth bound observations and the integrated polarization is essentially zero due to the symmetric backscattering situation. However, a second order scattering effect produces a measurable limb polarization for resolved planetary disks. We have made a detailed model for the spectropolarimetric signal of the limb polarization of Uranus between 520 and 935 nm to derive scattering properties of haze and cloud particles and to predict the polarization signal from an extra-solar point of view. We are also investigating imaging polarimetry of the thick haze layers on Titan and the poles of Jupiter. Additionally, we have calculated a large grid of intensity and polarization phase curves for simpler atmosphere models of extrasolar planets.

Planet traps and first planets: The critical metallicity for gas giant formation

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

Hasegawa, Yasuhiro; Hirashita, Hiroyuki, E-mail: yasu@asiaa.sinica.edu.tw, E-mail: hirashita@asiaa.sinica.edu.tw

2014-06-10

The ubiquity of planets poses an interesting question: when are first planets formed in galaxies? We investigate this by adopting a theoretical model where planet traps are combined with the standard core accretion scenario in which the efficiency of forming planetary cores directly relates to the metallicity ([Fe/H]) in disks. Three characteristic exoplanetary populations are examined: hot Jupiters, exo-Jupiters around 1 AU, and low-mass planets in tight orbits, such as super-Earths. We statistically compute planet formation frequencies (PFFs), as well as the orbital radius (〈R{sub rapid}〉) within which gas accretion becomes efficient enough to form Jovian planets, as a functionmore » of metallicity (–2 ≤ [Fe/H] ≤–0.6). We show that the total PFFs for these three populations increase steadily with metallicity. This is the direct outcome of the core accretion picture. For the metallicity range considered here, the population of low-mass planets dominates Jovian planets. The Jovian planets contribute to the PFFs above [Fe/H] ≅ –1. We find that the hot Jupiters form more efficiently than the exo-Jupiters at [Fe/H] ≲ –0.7. This arises from the slower growth of planetary cores and their more efficient radial inward transport by the host traps in lower metallicity disks. We show that the critical metallicity for forming Jovian planets is [Fe/H] ≅ –1.2 by comparing 〈R{sub rapid}〉 of hot Jupiters and low-mass planets. The comparison intrinsically links to the different gas accretion efficiency between these two types of planets. Therefore, this study implies that important physical processes in planet formation may be tested by exoplanet observations around metal-poor stars.« less

Comparison Simulations of Gas Giant Planet Formation via Disk Instability

NASA Astrophysics Data System (ADS)

Pickett, Megan K.; Cai, K.; Durisen, R.; Milne, M.

2011-01-01

There has been disagreement about whether cooling in protoplanetary disks can be sufficiently fast to induce the formation of gas giant protoplanets via gravitational instabilities. Simulations by our own group and others indicate that this method of planet formation does not work for disks around young, low-mass stars inside several tens of AU, while simulations by other groups show fragmentation into protoplanetary clumps in this region. To allow direct comparison in hopes of isolating the cause of the differences, we here present a comparison high-resolution three-dimensional hydrodynamics simulation of a protoplanetary disk,using an improved version of one of our own radiative schemes. We find that the disk does not fragment in our code but instead quickly settles into a state with only low amplitude nonaxisymmetric structure, which persists for at least several outer disk rotations. Further, we see no rapid radiative or convective cooling.

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

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

A desert of gas giant planets beyond tens of au: from feast to famine

NASA Astrophysics Data System (ADS)

Nayakshin, Sergei

2017-09-01

It is argued that frequency of gravitational fragmentation of young massive discs around FGK stars may be much higher than commonly believed. Numerical simulations presented here show that survival of gas giant planets at large separations from their host stars is very model dependent. Low-mass clumps in slowly cooling discs are found to accrete gas very slowly and migrate inward very rapidly in the well-known type I regime (no gap open). They are either tidally disrupted or survive as planets inwards of about 10 au. In this regime, probability of clump survival at large separations is extremely low, perhaps as low as 0.001, requiring up to a dozen clumps per star early on to explain the observed population. In contrast, initially massive clumps or low-mass clumps born in rapidly cooling discs accrete gas rapidly. Opening deep gaps in the disc, they migrate in the much slower type II regime and are more likely to survive beyond tens of au. The frequency of disc fragmentation in this case is at the per cent level if the clump growth saturates at brown dwarf masses but may be close to 100 per cent if clumps evolve into low stellar mass companions. Taking these theoretical uncertainties into account, current observations limit the number of planet mass clumps hatched by young massive discs around FGK stars to between 0.01 and ˜10. A deeper theoretical understanding of such discs is needed to narrow this uncertainty down.

The Last Gasp of Gas Giant Planet Formation: A Spitzer Study of the 5 Myr Old Cluster NGC 2362

NASA Astrophysics Data System (ADS)

Currie, Thayne; Lada, Charles J.; Plavchan, Peter; Robitaille, Thomas P.; Irwin, Jonathan; Kenyon, Scott J.

2009-06-01

Expanding upon the Infrared Array Camera (IRAC) survey from Dahm & Hillenbrand, we describe Spitzer IRAC and Multiband Imaging Photometer for Spitzer observations of the populous, 5 Myr old open cluster NGC 2362. We analyze the mid-IR colors of cluster members and compared their spectral energy distributions (SEDs) to star+circumstellar disk models to constrain the disk morphologies and evolutionary states. Early/intermediate-type confirmed/candidate cluster members either have photospheric mid-IR emission or weak, optically thin IR excess emission at λ >= 24 μm consistent with debris disks. Few late-type, solar/subsolar-mass stars have primordial disks. The disk population around late-type stars is dominated by disks with inner holes (canonical "transition disks") and "homologously depleted" disks. Both types of disks represent an intermediate stage between primordial disks and debris disks. Thus, in agreement with previous results, we find that multiple paths for the primordial-to-debris disk transition exist. Because these "evolved primordial disks" greatly outnumber primordial disks, our results undermine standard arguments in favor of a lsim105 yr timescale for the transition based on data from Taurus-Auriga. Because the typical transition timescale is far longer than 105 yr, these data also appear to rule out standard ultraviolet photoevaporation scenarios as the primary mechanism to explain the transition. Combining our data with other Spitzer surveys, we investigate the evolution of debris disks around high/intermediate-mass stars and investigate timescales for giant planet formation. Consistent with Currie et al., the luminosity of 24 μm emission in debris disks due to planet formation peaks at ≈10-20 Myr. If the gas and dust in disks evolve on similar timescales, the formation timescale for gas giant planets surrounding early-type, high/intermediate-mass (gsim1.4 M sun) stars is likely 1-5 Myr. Most solar/subsolar-mass stars detected by Spitzer have

Toward a Deterministic Model of Planetary Formation. II. The Formation and Retention of Gas Giant Planets around Stars with a Range of Metallicities

NASA Astrophysics Data System (ADS)

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

2004-11-01

The apparent dependence of detection frequency of extrasolar planets on the metallicity of their host stars is investigated with Monte Carlo simulations using a deterministic core-accretion planet formation model. According to this model, gas giants formed and acquired their mass Mp through planetesimal coagulation followed by the emergence of cores onto which gas is accreted. These protoplanets migrate and attain their asymptotic semimajor axis a through tidal interaction with their nascent disk. Based on the observed properties of protostellar disks, we generate an Mp-a distribution. Our results reproduce the observed lack of planets with intermediate mass Mp=10-100 M⊕ and a<~3 AU and with large mass Mp>~103 M⊕ and a<~0.2 AU. Based on the simulated Mp-a distributions, we also evaluate the metallicity dependence of the fraction of stars harboring planets that are detectable with current radial velocity surveys. If protostellar disks attain the same fraction of heavy elements as contained in their host stars, the detection probability around metal-rich stars would be greatly enhanced because protoplanetary cores formed in them can grow to several Earth masses prior to their depletion. These large masses are required for the cores to initiate rapid gas accretion and to transform into giant planets. The theoretically extrapolated metallicity dependence is consistent with the observations. This correlation does not arise naturally in the gravitational-instability scenario. We also suggest other metallicity dependences of the planet distributions that can be tested by ongoing observations.

Giant Planets in Reflected Light: What Science Can We Expect?

NASA Technical Reports Server (NTRS)

Marley, Mark

2016-01-01

Interpreting the reflection spectra of cool giant planets will be a challenge. Spectra of such worlds are expected to be primarily shaped by scattering from clouds and hazes and punctuated by absorption bands of methane, water, and ammonia. While the warmest giants may be cloudless, their atmospheres will almost certainly sport substantial photochemical hazes. Furthermore the masses of most direct imaging targets will be constrained by radial velocity observations, their radii, and thus atmospheric gravity, will be imperfectly known. The uncertainty in planet radius and gravity will compound with uncertain aerosol properties to make estimation of key absorber abundances difficult. To address such concerns our group is developing atmospheric retrieval tools to constrain quantities of interest, particular gas mixing ratios. We have applied our Markov Chain Monte Carlo methods to simulated data of the quality expected from the WFIRST CGI instrument and found that given sufficiently high SNR data we can confidentially identify and constrain the abundance of methane, cloud top pressures, gravity, and the star-planet-observer phase angle. In my presentation I will explain the expected characteristics of cool extrasolar giant planet reflection spectra, discuss these and other challenges in their interpretation, and summarize the science results we can expect from direct imaging observations.

Inner Super-Earths, Outer Gas Giants: How Pebble Isolation and Migration Feedback Keep Jupiters Cold

NASA Astrophysics Data System (ADS)

Fung, Jeffrey; Lee, Eve J.

2018-06-01

The majority of gas giants (planets of masses ≳102 M ⊕) are found to reside at distances beyond ∼1 au from their host stars. Within 1 au, the planetary population is dominated by super-Earths of 2–20 M ⊕. We show that this dichotomy between inner super-Earths and outer gas giants can be naturally explained should they form in nearly inviscid disks. In laminar disks, a planet can more easily repel disk gas away from its orbit. The feedback torque from the pile-up of gas inside the planet’s orbit slows down and eventually halts migration. A pressure bump outside the planet’s orbit traps pebbles and solids, starving the core. Gas giants are born cold and stay cold: more massive cores are preferentially formed at larger distances, and they barely migrate under disk feedback. We demonstrate this using two-dimensional hydrodynamical simulations of disk–planet interaction lasting up to 105 years: we track planet migration and pebble accretion until both come to an end by disk feedback. Whether cores undergo runaway gas accretion to become gas giants or not is determined by computing one-dimensional gas accretion models. Our simulations show that in an inviscid minimum mass solar nebula, gas giants do not form inside ∼0.5 au, nor can they migrate there while the disk is present. We also explore the dependence on disk mass and find that gas giants form further out in less massive disks.

Migration of Gas Giant Planets in a Gravitationally Unstable Disk

NASA Astrophysics Data System (ADS)

Desai, Karna Mahadev; Steiman-Cameron, Thomas Y.; Michael, Scott; Durisen, Richard H.

2017-01-01

Understanding the migration of giant planets in gravitationally unstable protoplanetary disks is important for understanding planetary system architecture, especially the existence of planets orbiting close to and at large distances from their stars. Migration rates can determine the efficiency of planet formation and survival rates of planets. We present results from simulations of 0.3, 1, and 3 Jupiter-mass planets in a 0.14 M⊙ protoplanetary disk around a 1 M⊙ star, where the disk is marginally unstable to gravitational instabilities (GIs). Each planet is simulated separately. We use CHYMERA, a radiative 3D hydrodynamics code developed by the Indiana University Hydrodynamics Group. The simulations include radiative cooling governed by realistic dust opacities. The planets are inserted into the disk, once the disk has settled into its quasi-steady GI-active phase. We simulate each of the 0.3, 1, and 3 Jupiter-mass planets by inserting it at three different locations in the disk, at the corotation radius and at the inner and outer Lindblad resonances. No matter where placed, the 3 Jupiter-mass planets tend to drift inexorably inward but with a rate that slows after many orbital periods. The 1 Jupiter-mass planets migrate mostly inward, but their motion can be delayed or reversed near the corotation of the two-armed wave. The 0.3 Jupiter-mass planets are much less predictable and frequently migrate outward. We analyze how the density of matter and waves in the disk at different azimuthal locations affect the migration.

Exploring Kepler Giant Planets in the Habitable Zone

NASA Astrophysics Data System (ADS)

Hill, Michelle L.; Kane, Stephen R.; Seperuelo Duarte, Eduardo; Kopparapu, Ravi K.; Gelino, Dawn M.; Wittenmyer, Robert A.

2018-06-01

The Kepler mission found hundreds of planet candidates within the Habitable Zones (HZ) of their host star, including over 70 candidates with radii larger than three Earth radii (R ⊕) within the optimistic HZ (OHZ). These giant planets are potential hosts to large terrestrial satellites (or exomoons) which would also exist in the HZ. We calculate the occurrence rates of giant planets (R p = 3.0–25 R ⊕) in the OHZ, and find a frequency of (6.5 ± 1.9)% for G stars, (11.5 ± 3.1)% for K stars, and (6 ± 6)% for M stars. We compare this with previously estimated occurrence rates of terrestrial planets in the HZ of G, K, and M stars and find that if each giant planet has one large terrestrial moon then these moons are less likely to exist in the HZ than terrestrial planets. However, if each giant planet holds more than one moon, then the occurrence rates of moons in the HZ would be comparable to that of terrestrial planets, and could potentially exceed them. We estimate the mass of each planet candidate using the mass–radius relationship developed by Chen & Kipping. We calculate the Hill radius of each planet to determine the area of influence of the planet in which any attached moon may reside, then calculate the estimated angular separation of the moon and planet for future imaging missions. Finally, we estimate the radial velocity semi-amplitudes of each planet for use in follow-up observations.

Direct imaging search for the "missing link" in giant planet formation

NASA Astrophysics Data System (ADS)

Ngo, Henry; Mawet, Dimitri; Ruane, Garreth; Xuan, Wenhao; Bowler, Brendan; Cook, Therese; Zawol, Zoe

2018-01-01

While transit and radial velocity detection techniques have probed giant planet populations at close separations (within a few au), current direct imaging surveys are finding giant planets at separations of 10s-100s au. Furthermore, these directly imaged planets are very massive, including some with masses above the deuterium burning limit. It is not certain whether these objects represent the high mass end of planet formation scenarios or the low mass end of star formation. We present a direct imaging survey to search for the "missing link" population between the close-in RV and transiting giant planets and the extremely distant directly imaged giant planets (i.e. giant planets between 5-10 au). Finding and characterizing this population allows for comparisons with the formation models of closer-in planets and connects directly imaged planets with closer-in planets in semi-major axis phase space. In addition, microlensing surveys have suggested a large reservoir of giant planets exist in this region. To find these "missing link" giant planets, our survey searches for giant planets around M-stars. The ubiquity of M-stars provide a large number of nearby targets and their L-band contrast with planets allow for sensitivities to smaller planet masses than surveys conducted at shorter wavelengths. Along with careful target selection, we use Keck's L-band vector vortex coronagraph to enable sensitivities of a few Jupiter masses as close as 4 au to their host stars. We present our completed 2-year survey targeting 200 young (10-150 Myr), nearby M-stars and our ongoing work to follow-up over 40 candidate objects.

Visible and Near-IR Imaging of Giant Planets: Outer Manifestations of Deeper Secrets

NASA Astrophysics Data System (ADS)

Hammel, Heidi B.

1996-09-01

Visible and near-infrared imaging of the giant planets -- Jupiter, Saturn, Uranus, and Neptune -- probes the outermost layers of clouds in these gaseous atmospheres. Not only are the images beautiful and striking in their color and diversity of detail, they also provide quantitative clues to the dynamical and chemical processes taking place both at the cloud tops and deeper in the interior: zonal wind profiles can be extracted; wavelength-dependent center-to-limb brightness variations yield valuable data for modeling vertical aerosol structure; the presence of planetary-scale atmospheric waves can sometimes be deduced; variations of cloud color and brightness with latitude provide insight into the underlying mechanisms driving circulation; development and evolution of discrete atmospheric features trace both exogenic and endogenic events. During the 1980's, our understanding of the giant planets was revolutionized by detailed visible-wavelength images taken by the Voyager spacecraft of these planets' atmospheres. However, those images were static: brief snapshots in time of four complex and dynamic atmospheric systems. In short, those images no longer represent the current appearance of these planets. Recently, our knowledge of the atmospheres of the gas giant planets has undergone major new advances, due in part to the excellent imaging capability and longer-term temporal sampling of the Hubble Space Telescope (HST) and the Galileo Mission to Jupiter. In this talk, I provide an update on our current understanding of the gas giants based on recent visible and near-infrared imaging, highlighting results from the collision of Comet Shoemaker-Levy 9 with Jupiter, Saturn's White Spots, intriguing changes in the atmosphere of Uranus, and Neptune's peripatetic clouds.

Planet Formation

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Young, Richard E. (Technical Monitor)

1997-01-01

Modern theories of star and planet formation, which are based upon observations of the Solar System and of young stars and their environments, predict that most single stars should have rocky planets in orbit about them; the frequency 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 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. Models for the formation of the giant planets found in recent radial velocity searches are discussed.

Giant Planet Occurrence Rate as a Function of Stellar Mass

NASA Astrophysics Data System (ADS)

Reffert, Sabine; Bergmann, Christoph; Quirrenbach, Andreas; Trifonov, Trifon; Künstler, Andreas

2013-07-01

For over 12 years we have carried out a Doppler survey at Lick Observatory, identifying 15 planets and 20 candidate planets in a sample of 373 G and K giant stars. We investigate giant planet occurrence rate as a function of stellar mass and metallicity in this sample, which covers the mass range from about 1 to 3.5-5.0 solar masses. We confirm the presence of a strong planet-metallicity correlation in our giant star sample, which is fully consistent with the well-known planet-metallicity correlation for main-sequence stars. Furthermore, we find a very strong dependence of the giant planet occurrence rate on stellar mass, which we fit with a gaussian distribution. Stars with masses of about 1.9 solar masses have the highest probability of hosting a giant planet, whereas the planet occurrence rate drops rapidly for masses larger than 2.5 to 3.0 solar masses. We do not find any planets around stars more massive than 2.7 solar masses, although we have 113 stars with masses between 2.7 and 5.0 solar masses in our sample (planet occurrence rate in that mass range: 0% +1.6% at 68.3% confidence). This result is not due to a bias related to planet detectability as a function of stellar mass. We conclude that larger mass stars do not form giant planets which are observable at orbital distances of a few AU today. Possible reasons include slower growth rate due to the snow-line being located further out, longer migration timescale and faster disk depletion.

On the Minimum Core Mass for Giant Planet Formation

NASA Astrophysics Data System (ADS)

Piso, Ana-Maria; Youdin, Andrew; Murray-Clay, Ruth

2013-07-01

The core accretion model proposes that giant planets form by the accretion of gas onto a solid protoplanetary core. Previous studies have found that there exists a "critical core mass" past which hydrostatic solutions can no longer be found and unstable atmosphere collapse occurs. This core mass is typically quoted to be around 10Me. In standard calculations of the critical core mass, planetesimal accretion deposits enough heat to alter the luminosity of the atmosphere, increasing the core mass required for the atmosphere to collapse. In this study we consider the limiting case in which planetesimal accretion is negligible and Kelvin-Helmholtz contraction dominates the luminosity evolution of the planet. We develop a two-layer atmosphere model with an inner convective region and an outer radiative zone that matches onto the protoplanetary disk, and we determine the minimum core mass for a giant planet to form within the typical disk lifetime for a variety of disk conditions. We denote this mass as critical core mass. The absolute minimum core mass required to nucleate atmosphere collapse is ˜ 8Me at 5 AU and steadily decreases to ˜ 3.5Me at 100 AU, for an ideal diatomic gas with a solar composition and a standard ISM opacity law. Lower opacity and disk temperature significantly reduce the critical core mass, while a decrease in the mean molecular weight of the nebular gas results in a larger critical core mass. Our results yield lower mass cores than corresponding studies for large planetesimal accretion rates.

Implications of the giant planets for the formation and evolution of planetary systems

NASA Technical Reports Server (NTRS)

Stevenson, David J.

1989-01-01

The giant planet region in the solar system appears to be bounded inside by the limit of water condensation, suggesting that the most abundant astrophysical condensate plays an important role in giant planet formation. Indeed, Jupiter and Saturn exhibit evidence for rock and/or ice cores or central concentrations that probably accumulated first, acting as nuclei for subsequent gas accumulation. This is a 'planetary' accumulation process, distinct from the stellar formation process, even though most of Jupiter has a similar composition to the primordial sun. Uranus and Neptune appear to exhibit evidence of an important role for giant impacts in their structure and evolution. No simple picture emerges for the temperature structure of the solar nebula from observations alone. However, it seems likely that Jupiter is the key to the planetary system, and a similar planet could be expected for other systems. The data and inferences from these data are summarized for the entire known solar system beyond the asteroid belt.

A DEFINITION FOR GIANT PLANETS BASED ON THE MASS–DENSITY RELATIONSHIP

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

Hatzes, Artie P.; Rauer, Heike, E-mail: artie@tls-tautenburg.de, E-mail: Heike.Rauer@dlr.de

We present the mass–density relationship (log M − log ρ) for objects with masses ranging from planets (M ≈ 0.01 M{sub Jup}) to stars (M > 0.08 M{sub ⊙}). This relationship shows three distinct regions separated by a change in slope in the log M − log ρ plane. In particular, objects with masses in the range 0.3 M{sub Jup}–60 M{sub Jup} follow a tight linear relationship with no distinguishing feature to separate the low-mass end (giant planets) from the high-mass end (brown dwarfs). We propose a new definition of giant planets simply based on changes in the slope ofmore » the log M versus log ρ relationship. By this criterion, objects with masses less than ≈0.3 M{sub Jup} are low-mass planets, either icy or rocky. Giant planets cover the mass range 0.3 M{sub Jup}–60 M{sub Jup}. Analogous to the stellar main sequence, objects on the upper end of the giant planet sequence (brown dwarfs) can simply be referred to as “high-mass giant planets,” while planets with masses near that of Jupiter can be called “low-mass giant planets.”.« less

Thermal escape from extrasolar giant planets.

PubMed

Koskinen, Tommi T; Lavvas, Panayotis; Harris, Matthew J; Yelle, Roger V

2014-04-28

The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres.

The comparative effect of FUV, EUV and X-ray disc photoevaporation on gas giant separations

NASA Astrophysics Data System (ADS)

Jennings, Jeff; Ercolano, Barbara; Rosotti, Giovanni P.

2018-04-01

Gas giants' early (≲ 5 Myr) orbital evolution occurs in a disc losing mass in part to photoevaporation driven by high energy irradiance from the host star. This process may ultimately overcome viscous accretion to disperse the disc and halt migrating giants by starving their orbits of gas, imprinting on giant planet separations in evolved systems. Inversion of this distribution could then give insight into whether stellar FUV, EUV or X-ray flux dominates photoevaporation, constraining planet formation and disc evolution models. We use a 1D hydrodynamic code in population syntheses for gas giants undergoing Type II migration in a viscously evolving disc subject to either a primarily FUV, EUV or X-ray flux from a pre-solar T Tauri star. The photoevaporative mass loss profile's unique peak location and width in each energetic regime produces characteristic features in the distribution of giant separations: a severe dearth of ≲ 2 MJ planets interior to 5 AU in the FUV scenario, a sharp concentration of ≲ 3 MJ planets between ≈1.5 - 2 AU in the EUV case, and a relative abundance of ≈2 - 3.5 MJ giants interior to 0.5 AU in the X-ray model. These features do not resemble the observational sample of gas giants with mass constraints, though our results do show some weaker qualitative similarities. We thus assess how the differing photoevaporative profiles interact with migrating giants and address the effects of large model uncertainties as a step to better connect disc models with trends in the exoplanet population.

The comparative effect of FUV, EUV and X-ray disc photoevaporation on gas giant separations

NASA Astrophysics Data System (ADS)

Jennings, Jeff; Ercolano, Barbara; Rosotti, Giovanni P.

2018-07-01

Gas giants' early (≲5 Myr) orbital evolution occurs in a disc losing mass in part to photoevaporation driven by high energy irradiance from the host star. This process may ultimately overcome viscous accretion to disperse the disc and halt migrating giants by starving their orbits of gas, imprinting on giant planet separations in evolved systems. Inversion of this distribution could then give insight into whether the stellar FUV, EUV or X-ray flux dominates photoevaporation, constraining planet formation and disc evolution models. We use a 1D hydrodynamic code in population syntheses for gas giants undergoing Type II migration in a viscously evolving disc subject to either a primarily FUV, EUV or X-ray flux from a pre-solar T Tauri star. The photoevaporative mass loss profile's unique peak location and width in each energetic regime produces characteristic features in the distribution of giant separations: a severe dearth of ≲2 MJ planets interior to 5 au in the FUV scenario, a sharp concentration of ≲3 MJ planets between ≈1.5-2 au in the EUV case and a relative abundance of ≈2-3.5 MJ giants interior to 0.5 au in the X-ray model. These features do not resemble the observational sample of gas giants with mass constraints, although our results do show some weaker qualitative similarities. We thus assess how the differing photoevaporative profiles interact with migrating giants and address the effects of large model uncertainties as a step to better connect disc models with trends in the exoplanet population.

Planet Formation and the Characteristics of Extrasolar Planets

NASA Technical Reports Server (NTRS)

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

2000-01-01

An overview of current theories of planetary growth, emphasizing the formation of extrasolar planets, is presented. Models of planet formation are based upon observations of the Solar System, extrasolar planets, and young stars and their environments. 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 planets begin their growth like terrestrial planets, but if they become massive enough before the protoplanetary disk dissipates, then they are able to accumulate substantial amounts of gas. These models predict that rocky planets should form in orbit about most single stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. A potential hazard to planetary systems is radial decay of planetary orbits resulting from interactions with material within the disk. Planets more massive than Earth have the potential to decay the fastest, and may be able to sweep up smaller planets in their path. The implications of the giant planets found in recent radial velocity searches for the abundances of habitable planets are discussed.

Seeing Double with K2: Testing Re-inflation with Two Remarkably Similar Planets around Red Giant Branch Stars

NASA Astrophysics Data System (ADS)

Grunblatt, Samuel K.; Huber, Daniel; Gaidos, Eric; Lopez, Eric D.; Howard, Andrew W.; Isaacson, Howard T.; Sinukoff, Evan; Vanderburg, Andrew; Nofi, Larissa; Yu, Jie; North, Thomas S. H.; Chaplin, William; Foreman-Mackey, Daniel; Petigura, Erik; Ansdell, Megan; Weiss, Lauren; Fulton, Benjamin; Lin, Douglas N. C.

2017-12-01

Despite more than 20 years since the discovery of the first gas giant planet with an anomalously large radius, the mechanism for planet inflation remains unknown. Here, we report the discovery of K2-132b, an inflated gas giant planet found with the NASA K2 Mission, and a revised mass for another inflated planet, K2-97b. These planets orbit on ≈9 day orbits around host stars that recently evolved into red giants. We constrain the irradiation history of these planets using models constrained by asteroseismology and Keck/High Resolution Echelle Spectrometer spectroscopy and radial velocity measurements. We measure planet radii of 1.31 ± 0.11 R J and 1.30 ± 0.07 R J, respectively. These radii are typical for planets receiving the current irradiation, but not the former, zero age main-sequence irradiation of these planets. This suggests that the current sizes of these planets are directly correlated to their current irradiation. Our precise constraints of the masses and radii of the stars and planets in these systems allow us to constrain the planetary heating efficiency of both systems as 0.03{ % }-0.02 % +0.03 % . These results are consistent with a planet re-inflation scenario, but suggest that the efficiency of planet re-inflation may be lower than previously theorized. Finally, we discuss the agreement within 10% of the stellar masses and radii, and the planet masses, radii, and orbital periods of both systems, and speculate that this may be due to selection bias in searching for planets around evolved stars.

Thermal escape from extrasolar giant planets

PubMed Central

Koskinen, Tommi T.; Lavvas, Panayotis; Harris, Matthew J.; Yelle, Roger V.

2014-01-01

The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres. PMID:24664923

Theories of the origin and evolution of the giant planets

NASA Technical Reports Server (NTRS)

Pollack, J. B.; Bodenheimer, P.

1989-01-01

Following the accretion of solids and gases in the solar nebula, the giant planets contracted to their present sizes over the age of the solar system. It is presently hypothesized that this contraction was rapid, but not hydrodynamic; at a later stage, a nebular disk out of which the regular satellites formed may have been spun out of the outer envelope of the contracting giant planets due to a combination of total angular momentum conservation and the outward transfer of specific angular momentum in the envelope. If these hypotheses are true, the composition of the irregular satellites directly reflects the composition of planetesimals from which the giant planets formed, while the composition of the regular satellites is indicative of the composition of the less volatile components of the outer envelopes of the giant planets.

A Gas-Poor Planetesimal Feeding Model for the Formation of Giant Planet Satellite Systems: Consequences for the Atmosphere of Titan

NASA Technical Reports Server (NTRS)

Estrada, P. R.; Mosqueira, I.

2005-01-01

Given our presently inadequate understanding of the turbulent state of the solar and planetary nebulae, we believe the way to make progress in satellite formation is to consider two end member models that avoid over-reliance on specific choices of the turbulence (alpha), which is essentially a free parameter. The first end member model postulates turbulence decay once giant planet accretion ends. If so, Keplerian disks must eventually pass through the quiescent phases, so that the survival of satellites (and planets) ultimately hinges on gap-opening. In this scenario, the criterion for gap-opening itself sets the value for the gas surface density of the satellite disk.

Giant Planet Candidates, Brown Dwarfs, and Binaries from the SDSS-III MARVELS Planet Survey.

NASA Astrophysics Data System (ADS)

Thomas, Neil; Ge, Jian; Li, Rui; de Lee, Nathan M.; Heslar, Michael; Ma, Bo; SDSS-Iii Marvels Team

2015-01-01

We report the discoveries of giant planet candidates, brown dwarfs, and binaries from the SDSS-III MARVELS survey. The finalized 1D pipeline has provided 18 giant planet candidates, 16 brown dwarfs, and over 500 binaries. An additional 96 targets having RV variability indicative of a giant planet companion are also reported for future investigation. These candidates are found using the advanced MARVELS 1D data pipeline developed at UF from scratch over the past three years. This pipeline carefully corrects most of the instrument effects (such as trace, slant, distortion, drifts and dispersion) and observation condition effects (such as illumination profile, fiber degradation, and tracking variations). The result is long-term RV precisions that approach the photon limits in many cases for the ~89,000 individual stellar observations. A 2D version of the pipeline that uses interferometric information is nearing completion and is demonstrating a reduction of errors to half the current levels. The 2D processing will be used to increase the robustness of the detections presented here and to find new candidates in RV regions not confidently detectable with the 1D pipeline. The MARVELS survey has produced the largest homogeneous RV measurements of 3300 V=7.6-12 FGK stars with a well defined cadence of 27 RV measurements over 2 years. The MARVELS RV data and other follow-up data (photometry, high contrast imaging, high resolution spectroscopy and RV measurements) will explore the diversity of giant planet companion formation and evolution around stars with a broad range in metallicity (Fe/H -1.5-0.5), mass ( 0.6-2.5M(sun)), and environment (thin disk and thick disk), and will help to address the key scientific questions identified for the MARVELS survey including, but not limited to: Do metal poor stars obey the same trends for planet occurrence as metal rich stars? What is the distribution of giant planets around intermediate-mass stars and binaries? Is the 'planet desert

Survival of extrasolar giant planet moons in planet-planet scattering

NASA Astrophysics Data System (ADS)

CIAN HONG, YU; Lunine, Jonathan; Nicholson, Phillip; Raymond, Sean

2015-12-01

Planet-planet scattering is the best candidate mechanism for explaining the eccentricity distribution of exoplanets. Here we study the survival and dynamics of exomoons under strong perturbations during giant planet scattering. During close encounters, planets and moons exchange orbital angular momentum and energy. The most common outcomes are the destruction of moons by ejection from the system, collision with the planets and the star, and scattering of moons onto perturbed but still planet-bound orbits. A small percentage of interesting moons can remain bound to ejected (free-floating) planets or be captured by a different planet. Moons' survival rate is correlated with planet observables such as mass, semi-major axis, eccentricity and inclination, as well as the close encounter distance and the number of close encounters. In addition, moons' survival rate and dynamical outcomes are predetermined by the moons' initial semi-major axes. The survival rate drops quickly as moons' distances increase, but simulations predict a good chance of survival for the Galilean moons. Moons with different dynamical outcomes occupy different regions of orbital parameter space, which may enable the study of moons' past evolution. Potential effects of planet obliquity evolution caused by close encounters on the satellites’ stability and dynamics will be reported, as well as detailed and systematic studies of individual close encounter events.

New steps in testing the Tidal Downsizing hypothesis for planet formation

NASA Astrophysics Data System (ADS)

Nayakshin, S.

2013-09-01

of our model is that giant young proto-planets, in addition to interrupting accretion flows by creating deep gaps, can also feed their protostars by "restarting" the accretion flows. Since dust sediments and is locked in the solid cores, the envelopes of these proto-planets are dust-poor. Therefore, in Nayakshin (2013) we proposed that the observed transition discs with large inner holes, accreting gas but not dust, may in fact be exactly the systems accreting dust-poor envelopes of giant planets being in the process of "downsizing". We shall also discuss whether this model can acount for some of the most challenging exoplanetary systems found by Kepler, such as the densly packed multiplanet worlds Kepler 36 and Kepler 11. The obvious challenge is that bringing in a massive giant planet could destabilise the orbits of the inner lower mass planets. (2) Whether the massive young protoplanets born by gravitational instability at 100 AU migrate rapidly inward (which is the key assumption of TD) or stay behind and accrete gas rapidly to become Brown Dwarfs is a key issue for both planet and low mass binary companion formation fields. Population synthesis models based on analytical estimates of the process (Forgan and Rice, 2013) show that only a few percent of their theoretical discs are in the TD regime; most produce BDs and low mass stars, as previously found by Stamattelos and Whitworth (2009). Nayakshin and Cha (2013; MNRAS accepted) study the effect of radiative preheating from growing giant planets on their immediate disc environment. It is found that gas in vicinity of the protostar is significantly hotter than found in simulations and analytical estimates that neglect the preheating effect. Clumps less massive than 6 Jupiter masses are found to build massive hot radiative atmospheres around them, "protecting" them from further gas accretion. These clumps rapidly migrate in and are in the TD regime, in whereas clumps more massive than 10 Jupiter masses indeed form

Long term evolution of planetary systems with a terrestrial planet and a giant planet.

NASA Astrophysics Data System (ADS)

Georgakarakos, Nikolaos; Dobbs-Dixon, Ian; Way, Michael J.

2017-06-01

We study the long term orbital evolution of a terrestrial planet under the gravitational perturbations of a giant planet. In particular, we are interested in situations where the two planets are in the same plane and are relatively close. We examine both possible configurations: the giant planet orbit being either outside or inside the orbit of the smaller planet. The perturbing potential is expanded to high orders and an analytical solution of the terrestrial planetary orbit is derived. The analytical estimates are then compared against results from the numerical integration of the full equations of motion and we find that the analytical solution works reasonably well. An interesting finding is that the new analytical estimates improve greatly the predictions for the timescales of the orbital evolution of the terrestrial planet compared to an octupole order expansion.

Hot super-Earths and giant planet cores from different migration histories

NASA Astrophysics Data System (ADS)

Cossou, Christophe; Raymond, Sean N.; Hersant, Franck; Pierens, Arnaud

2014-09-01

Planetary embryos embedded in gaseous protoplanetary disks undergo Type I orbital migration. Migration can be inward or outward depending on the local disk properties but, in general, only planets more massive than several M⊕ can migrate outward. Here we propose that an embryo's migration history determines whether it becomes a hot super-Earth or the core of a giant planet. Systems of hot super-Earths (or mini-Neptunes) form when embryos migrate inward and pile up at the inner edge of the disk. Giant planet cores form when inward-migrating embryos become massive enough to switch direction and migrate outward. We present simulations of this process using a modified N-body code, starting from a swarm of planetary embryos. Systems of hot super-Earths form in resonant chains with the innermost planet at or interior to the disk inner edge. Resonant chains are disrupted by late dynamical instabilities triggered by the dispersal of the gaseous disk. Giant planet cores migrate outward toward zero-torque zones, which move inward and eventually disappear as the disk disperses. Giant planet cores migrate inward with these zones and are stranded at ~1-5 AU. Our model reproduces several properties of the observed extra-solar planet populations. The frequency of giant planet cores increases strongly when the mass in solids is increased, consistent with the observed giant exoplanet - stellar metallicity correlation. The frequency of hot super-Earths is not a function of stellar metallicity, also in agreement with observations. Our simulations can reproduce the broad characteristics of the observed super-Earth population.

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.

Star-planet interactions. IV. Possibility of detecting the orbit-shrinking of a planet around a red giant

NASA Astrophysics Data System (ADS)

Meynet, Georges; Eggenberger, Patrick; Privitera, Giovanni; Georgy, Cyril; Ekström, Sylvia; Alibert, Yann; Lovis, Christophe

2017-06-01

The surface rotations of some red giants are so fast that they must have been spun up by tidal interaction with a close companion, either another star, a brown dwarf, or a planet. We focus here on the case of red giants that are spun up by tidal interaction with a planet. When the distance between the planet and the star decreases, the spin period of the star decreases, the orbital period of the planet decreases, and the reflex motion of the star increases. We study the change rate of these three quantities when the circular orbit of a planet of 15 MJ that initially orbits a 2 M⊙ star at 1 au shrinks under the action of tidal forces during the red giant phase. We use stellar evolution models coupled with computations of the orbital evolution of the planet, which allows us to follow the exchanges of angular momentum between the star and the orbit in a consistent way. We obtain that the reflex motion of the red giant star increases by more than 1 m s-1 per year in the last 40 yr before the planet engulfment. During this phase, the reflex motion of the star is between 660 and 710 m s-1. The spin period of the star increases by more than about 10 min per year in the last 3000 yr before engulfment. During this period, the spin period of the star is shorter than 0.7 yr. During this same period, the variation in orbital period, which is shorter than 0.18 yr, is on the same order of magnitude. Changes in reflex-motion and spin velocities are very small and thus most likely out of reach of being observed. The most promising way of detecting this effect is through observations of transiting planets, that is, through changes of the beginning or end of the transit. For the relatively long orbital periods expected around red giants, long observing runs of typically a few years are needed. Interesting star-planet systems that currently are in this stage of orbit-shrinking would be red giants with fast rotation (above typically 4-5 km s-1), a low surface gravity (log g lower

Sustained Accretion on Gas Giants Surrounded by Low-Turbulence Circumplanetary Disks

NASA Astrophysics Data System (ADS)

D'Angelo, Gennaro; Marzari, Francesco

2015-11-01

Gas giants more massive than Saturn acquire most of their envelope while surrounded by a circumplanetary disk (CPD), which extends over a fraction of the planet’s Hill radius. Akin to circumstellar disks, CPDs may be subject to MRI-driven turbulence and contain low-turbulence regions, i.e., dead zones. It was suggested that CPDs may inhibit sustained gas accretion, thus limiting planet growth, because gas transport through a CPD may be severely reduced by a dead zone, a consequence at odds with the presence of Jupiter-mass (and larger) planets. We studied how an extended dead zone influences gas accretion on a Jupiter-mass planet, using global 3D hydrodynamics calculations with mesh refinements. The accretion flow from the circumstellar disk to the CPD is resolved locally at the length scale Rj, Jupiter's radius. The gas kinematic viscosity is assumed to be constant and the dead zone around the planet is modeled as a region of much lower viscosity, extending from ~Rj out to ~60Rj and off the mid-plane for a few CPD scale heights. We obtain accretion rates only marginally smaller than those reported by, e.g., D'Angelo et al. (2003), Bate et al. (2003), Bodenheimer et al. (2013), who applied the same constant kinematic viscosity everywhere, including in the CPD. As found by several previous studies (e.g., D’Angelo et al. 2003; Bate et al. 2003; Tanigawa et al. 2012; Ayliffe and Bate 2012; Gressel et al. 2013; Szulágyi et al. 2014), the accretion flow does not proceed through the CPD mid-plane but rather at and above the CPD surface, hence involving MRI-active regions (Turner et al. 2014). We conclude that the presence of a dead zone in a CPD does not inhibit gas accretion on a giant planet. Sustained accretion in the presence of a CPD is consistent not only with the formation of Jupiter but also with observed extrasolar planets more massive than Jupiter. We place these results in the context of the growth and migration of a pair of giant planets locked in the 2

Long Term Evolution of Planetary Systems with a Terrestrial Planet and a Giant Planet

NASA Technical Reports Server (NTRS)

Georgakarakos, Nikolaos; Dobbs-Dixon, Ian; Way, Michael J.

2016-01-01

We study the long term orbital evolution of a terrestrial planet under the gravitational perturbations of a giant planet. In particular, we are interested in situations where the two planets are in the same plane and are relatively close. We examine both possible configurations: the giant planet orbit being either outside or inside the orbit of the smaller planet. The perturbing potential is expanded to high orders and an analytical solution of the terrestrial planetary orbit is derived. The analytical estimates are then compared against results from the numerical integration of the full equations of motion and we find that the analytical solution works reasonably well. An interesting finding is that the new analytical estimates improve greatly the predictions for the timescales of the orbital evolution of the terrestrial planet compared to an octupole order expansion. Finally, we briefly discuss possible applications of the analytical estimates in astrophysical problems.

Planet Formation

NASA Technical Reports Server (NTRS)

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

1998-01-01

An overview of current theories of star and planet formation is presented. These models are based upon observations of the Solar System and of young stars and their environments. They 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 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.

On the Nature and Timing of Giant Planet Migration in the Solar System

NASA Astrophysics Data System (ADS)

Agnor, Craig B.

2016-05-01

Giant planet migration is a natural outcome of gravitational scattering and planet formation processes (Fernandez & Ip 1984). There is compelling evidence that the solar system's giant planets experienced large-scale migration involving close approaches between planets as well as smooth radial migration via planetesimal scattering. Aspects of giant planet migration have been invoked to explain many features of the outer solar system including the resonant structure of the Kuiper Belt (e.g., Malhotra 1993, Levison et al. 2008), the eccentricities of Jupiter and Saturn (Tsiganis et al. 2005, Morbidelli et al. 2009), the capture of Jupiter's Trojan companions (Morbidelli et al. 2005) and the capture of irregular planetary satellites (e.g., Nesvorny et al. 2007) to name a few. If this migration epoch occurred after the formation of the inner planets, then it may also explain the so-called lunar Late Heavy Bombardment (Gomes et al. 2005). This scenario necessarily requires coeval terrestrial and migrating giant planets. Recent N-body integrations exploring this issue have shown that giant planet migration may excite the terrestrial system via nodal and apsidal secular resonances (e.g., Brasser et al. 2013), may drive the terrestrial planets to crossing orbits (Kaib & Chambers 2016) or alternatively leave the inner solar system in a state closely resembling the observed one (Roig et al. 2016). The factors accounting for the large range of outcomes remain unclear. Using linear secular models and N-body simulations I am identifying and characterising the principal aspects of giant planet migration that excite the terrestrial planets' orbits. I will present these results and discuss how they inform the nature and timing of giant planet migration in the solar system.

The International Outer Planets Watch atmospheres node database of giant-planet images

NASA Astrophysics Data System (ADS)

Hueso, R.; Legarreta, J.; Sánchez-Lavega, A.; Rojas, J. F.; Gómez-Forrellad, J. M.

2011-10-01

The Atmospheres Node of the International Outer Planets Watch (IOPW) is aimed to encourage the observations and study of the atmospheres of the Giant Planets. One of its main activities is to provide an interaction between the professional and amateur astronomical communities maintaining an online and fully searchable database of images of the giant planets obtained from amateur astronomers and available to both professional and amateurs [1]. The IOPW database contains about 13,000 image observations of Jupiter and Saturn obtained in the visible range with a few contributions of Uranus and Neptune. We describe the organization and structure of the database as posted in the Internet and in particular the PVOL software (Planetary Virtual Observatory & Laboratory) designed to manage the site and based in concepts from Virtual Observatory projects.

New Directions in Giant Planet Formation

NASA Astrophysics Data System (ADS)

Youdin, Andrew

The proposed research will explore the limits of the core accretion mechanism for forming giant planets, both in terms of timescale and orbital distance. This theoretical research will be useful in interpreting the results of ongoing exoplanet searches. The effects of radiogenic heating and aerodynamic accretion of pebbles and boulders will be included in time-dependent models of atmospheric structure and growth. To investigate these issues, we will develop and publicly share a protoplanet atmospheric evolution code as an extension of the MESA stellar evolution code. By focusing on relevant processes in the early stages of giant planet formation, we can refine model predictions for exoplanet searches at a wide range of stellar ages and distances from the host star.

Planet Formation

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Fonda, Mark (Technical Monitor)

2002-01-01

Modern theories of star and planet formation and of the orbital stability of planetary systems are described and used to discuss possible characteristics of undiscovered planetary systems. The most detailed models of planetary growth are based upon observations of planets and smaller bodies within our own Solar System and of young stars and their environments. 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 planets begin their growth as do terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. These models predict that rocky planets should form in orbit about most single stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. A potential hazard to planetary systems is radial decay of planetary orbits resulting from interactions with material within the disk. Planets more massive than Earth have the potential to decay the fastest, and may be able to sweep up smaller planets in their path. The implications of the giant planets found in recent radial velocity searches for the abundances of habitable planets are discussed, and the methods that are being used and planned for detecting and characterizing extrasolar planets are reviewed.

Formation of the Giant Planets by Concurrent Accretion of Solids and Gas

NASA Technical Reports Server (NTRS)

Hubickyj, Olenka

1997-01-01

Models were developed to simulate planet formation. Three major phases are characterized in the simulations: (1) planetesimal accretion rate, which dominates that of gas, rapidly increases owing to runaway accretion, then decreases as the planet's feeding zone is depleted; (2) occurs when both solid and gas accretion rates are small and nearly independent of time; and (3) starts when the solid and gas masses are about equal and is marked by runaway gas accretion. The models applicability to planets in our Solar System are judged using two basic "yardsticks". The results suggest that the solar nebula dissipated while Uranus and Neptune were in the second phase, during which, for a relatively long time, the masses of their gaseous envelopes were small but not negligible compared to the total masses. Background information, results and a published article are included in the report.

[Extrasolar terrestrial planets and possibility of extraterrestrial life].

PubMed

Ida, Shigeru

2003-12-01

Recent development of research on extrasolar planets are reviewed. About 120 extrasolar Jupiter-mass planets have been discovered through the observation of Doppler shift in the light of their host stars that is caused by acceleration due to planet orbital motions. Although the extrasolar planets so far observed may be limited to gas giant planets and their orbits differ from those of giant planets in our Solar system (Jupiter and Saturn), the theoretically predicted probability of existence of extrasolar terrestrial planets that can have liquid water ocean on their surface is comparable to that of detectable gas giant planets. Based on the number of extrasolar gas giants detected so far, about 100 life-sustainable planets may exist within a range of 200 light years. Indirect observation of extrasolar terrestrial planets would be done with space telescopes within several years and direct one may be done within 20 years. The latter can detect biomarkers on these planets as well.

The Effect of Protoplanetary Disk Cooling Times on the Formation of Gas Giant Planets by Gravitational Instability

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

Boss, Alan P., E-mail: aboss@carnegiescience.edu

2017-02-10

Observational evidence exists for the formation of gas giant planets on wide orbits around young stars by disk gravitational instability, but the roles of disk instability and core accretion for forming gas giants on shorter period orbits are less clear. The controversy extends to population synthesis models of exoplanet demographics and to hydrodynamical models of the fragmentation process. The latter refers largely to the handling of radiative transfer in three-dimensional (3D) hydrodynamical models, which controls heating and cooling processes in gravitationally unstable disks, and hence dense clump formation. A suite of models using the β cooling approximation is presented here.more » The initial disks have masses of 0.091 M {sub ⊙} and extend from 4 to 20 au around a 1 M {sub ⊙} protostar. The initial minimum Toomre Qi values range from 1.3 to 2.7, while β ranges from 1 to 100. We show that the choice of Q {sub i} is equal in importance to the β value assumed: high Q{sub i} disks can be stable for small β , when the initial disk temperature is taken as a lower bound, while low Q{sub i} disks can fragment for high β . These results imply that the evolution of disks toward low Q{sub i} must be taken into account in assessing disk fragmentation possibilities, at least in the inner disk, i.e., inside about 20 au. The models suggest that if low Q{sub i} disks can form, there should be an as yet largely undetected population of gas giants orbiting G dwarfs between about 6 au and 16 au.« less

Four new planets around giant stars and the mass-metallicity correlation of planet-hosting stars

NASA Astrophysics Data System (ADS)

Jones, M. I.; Jenkins, J. S.; Brahm, R.; Wittenmyer, R. A.; Olivares E., F.; Melo, C. H. F.; Rojo, P.; Jordán, A.; Drass, H.; Butler, R. P.; Wang, L.

2016-05-01

Context. Exoplanet searches have revealed interesting correlations between the stellar properties and the occurrence rate of planets. In particular, different independent surveys have demonstrated that giant planets are preferentially found around metal-rich stars and that their fraction increases with the stellar mass. Aims: During the past six years we have conducted a radial velocity follow-up program of 166 giant stars to detect substellar companions and to characterize their orbital properties. Using this information, we aim to study the role of the stellar evolution in the orbital parameters of the companions and to unveil possible correlations between the stellar properties and the occurrence rate of giant planets. Methods: We took multi-epoch spectra using FEROS and CHIRON for all of our targets, from which we computed precision radial velocities and derived atmospheric and physical parameters. Additionally, velocities computed from UCLES spectra are presented here. By studying the periodic radial velocity signals, we detected the presence of several substellar companions. Results: We present four new planetary systems around the giant stars HIP 8541, HIP 74890, HIP 84056, and HIP 95124. Additionally, we study the correlation between the occurrence rate of giant planets with the stellar mass and metallicity of our targets. We find that giant planets are more frequent around metal-rich stars, reaching a peak in the detection of f = 16.7+15.5-5.9% around stars with [Fe/H] ~ 0.35 dex. Similarly, we observe a positive correlation of the planet occurrence rate with the stellar mass, between M⋆ ~ 1.0 and 2.1 M⊙, with a maximum of f = 13.0+10.1-4.2% at M⋆ = 2.1 M⊙. Conclusions: We conclude that giant planets are preferentially formed around metal-rich stars. In addition, we conclude that they are more efficiently formed around more massive stars, in the stellar mass range of ~1.0-2.1 M⊙. These observational results confirm previous findings for solar

THE EVOLUTION OF CIRCUMPLANETARY DISKS AROUND PLANETS IN WIDE ORBITS: IMPLICATIONS FOR FORMATION THEORY, OBSERVATIONS, AND MOON SYSTEMS

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

Shabram, Megan; Boley, Aaron C.

2013-04-10

Using radiation hydrodynamics simulations, we explore the evolution of circumplanetary disks around wide-orbit proto-gas giants. At large distances from the star ({approx}100 AU), gravitational instability followed by disk fragmentation can form low-mass substellar companions (massive gas giants and/or brown dwarfs) that are likely to host large disks. We examine the initial evolution of these subdisks and their role in regulating the growth of their substellar companions, as well as explore consequences of their interactions with circumstellar material. We find that subdisks that form in the context of GIs evolve quickly from a very massive state. Long-term accretion rates from themore » subdisk onto the proto-gas giant reach {approx}0.3 Jupiter masses kyr{sup -1}. We also find consistency with previous simulations, demonstrating that subdisks are truncated at {approx}1/3 of the companion's Hill radius and are thick, with (h/r) of {approx}> 0.2. The thickness of subdisks draws to question the use of thin-disk approximations for understanding the behavior of subdisks, and the morphology of subdisks has implications for the formation and extent of satellite systems. These subdisks create heating events in otherwise cold regions of the circumstellar disk and serve as planet formation beacons that can be detected by instruments such as ALMA.« less

PLANET ENGULFMENT BY {approx}1.5-3 M{sub sun} RED GIANTS

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

Kunitomo, M.; Ikoma, M.; Sato, B.

2011-08-20

Recent radial-velocity surveys for GK clump giants have revealed that planets also exist around {approx}1.5-3 M{sub sun} stars. However, no planets have been found inside 0.6 AU around clump giants, in contrast to solar-type main-sequence stars, many of which harbor short-period planets such as hot Jupiters. In this study, we examine the possibility that planets were engulfed by host stars evolving on the red-giant branch (RGB). We integrate the orbital evolution of planets in the RGB and helium-burning phases of host stars, including the effects of stellar tide and stellar mass loss. Then we derive the critical semimajor axis (ormore » the survival limit) inside which planets are eventually engulfed by their host stars after tidal decay of their orbits. Specifically, we investigate the impact of stellar mass and other stellar parameters on the survival limit in more detail than previous studies. In addition, we make detailed comparisons with measured semimajor axes of planets detected so far, which no previous study has done. We find that the critical semimajor axis is quite sensitive to stellar mass in the range between 1.7 and 2.1 M{sub sun}, which suggests a need for careful comparison between theoretical and observational limits of the existence of planets. Our comparison demonstrates that all planets orbiting GK clump giants that have been detected are beyond the survival limit, which is consistent with the planet-engulfment hypothesis. However, on the high-mass side (>2.1M{sub sun}), the detected planets are orbiting significantly far from the survival limit, which suggests that engulfment by host stars may not be the main reason for the observed lack of short-period giant planets. To confirm our conclusion, the detection of more planets around clump giants, especially with masses {approx}> 2.5M{sub sun}, is required.« less

The accretion of migrating giant planets

NASA Astrophysics Data System (ADS)

Dürmann, Christoph; Kley, Wilhelm

2017-02-01

Aims: Most studies concerning the growth and evolution of massive planets focus either on their accretion or their migration only. In this work we study both processes concurrently to investigate how they might mutually affect one another. Methods: We modeled a two-dimensional disk with a steady accretion flow onto the central star and embedded a Jupiter mass planet at 5.2 au. The disk is locally isothermal and viscosity is modeled using a constant α. The planet is held on a fixed orbit for a few hundred orbits to allow the disk to adapt and carve a gap. After this period, the planet is released and free to move according to the gravitational interaction with the gas disk. The mass accretion onto the planet is modeled by removing a fraction of gas from the inner Hill sphere, and the removed mass and momentum can be added to the planet. Results: Our results show that a fast migrating planet is able to accrete more gas than a slower migrating planet. Utilizing a tracer fluid we analyzed the origin of the accreted gas originating predominantly from the inner disk for a fast migrating planet. In the case of slower migration, the fraction of gas from the outer disk increases. We also found that even for very high accretion rates, in some cases gas crosses the planetary gap from the inner to the outer disk. Our simulations show that the crossing of gas changes during the migration process as the migration rate slows down. Therefore, classical type II migration where the planet migrates with the viscous drift rate and no gas crosses the gap is no general process but may only occur for special parameters and at a certain time during the orbital evolution of the planet.

Protoplanetary Disks and Planet Formation a Computational Perspective

NASA Astrophysics Data System (ADS)

Backus, Isaac

In this thesis I present my research on the early stages of planet formation. Using advanced computational modeling techniques, I study global gas and gravitational dynamics in proto- planetary disks (PPDs) on length scales from the radius of Jupiter to the size of the solar system. In that environment, I investigate the formation of gas giants and the migration, enhancement, and distribution of small solids--the precursors to planetesimals and gas giant cores. I examine numerical techniques used in planet formation and PPD modeling, especially methods for generating initial conditions (ICs) in these unstable, chaotic systems. Disk simulation outcomes may depend strongly on ICs, which may explain results in the literature. I present the largest suite of high resolution PPD simulations to-date and argue that direct fragmentations of PPDs around M-Dwarfs is a plausible path to rapidly forming gas giants. I implement dust physics to track the migration of centimeter and smaller dust grains in very high resolution PPD simulations. While current dust methods are slow, with strict resolution and/or time-stepping requirements, and have some serious numerical issues, we can still demonstrate that dust does not concentrate at the pressure maxima of spiral arms, an indication that spiral features observed in the dust component are at least as well resolved in the gas. Additionally, coherent spiral arms do not limit dust settling. We suggest a novel mechanism for disk fragmentation at large radii driven by dust accretion from the surrounding nebula. We also investigate self induced dust traps, a mechanism which may help explain the growth of solids beyond meter sizes. We argue that current apparent demonstrations of this mechanism may be due to numerical artifacts and require further investigation.

Optical Spectra of Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Heap, Sara R.; Hubeny, Ivan; Sudarsky, David; Burrows, Adam

2004-01-01

The flux distribution of a planet relative to its host star is a critical quantity for planning space observatories to detect and characterize extrasolar giant planets (EGP's). In this paper, we present optical planet-star contrasts of Jupiter-mass planets as a function of stellar type, orbital distance, and planetary cloud characteristics. As originally shown by Sudarsky et al. (2000, 2003), the phaseaveraged brightness of an EGP does not necessarily decrease monotonically with greater orbital distance because of changes in its albedo and absorption spectrum at lower temperatures. We apply our results to Eclipse, a 1.8-m optical telescope + coronograph to be proposed as a NASA Discovery mission later this year.

The Longevity of Water Ice on Ganymedes and Europas around Migrated Giant Planets

NASA Astrophysics Data System (ADS)

Lehmer, Owen R.; Catling, David C.; Zahnle, Kevin J.

2017-04-01

The gas giant planets in the Solar System have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. If a Jupiter-like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. Here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. The hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to the star. At some planet-star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. This runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. However, for icy moons of Ganymede’s size around a Sun-like star we found that surface water (either ice or liquid) can persist indefinitely outside the runaway greenhouse orbital distance. In contrast, the surface water on smaller moons of Europa’s size will only persist on timescales greater than 1 Gyr at distances ranging 1.49-0.74 au around a Sun-like star for Bond albedos of 0.2 and 0.8, where the lower albedo becomes relevant if ice melts. Consequently, small moons can lose their icy shells, which would create a torus of H atoms around their host planet that might be detectable in future observations.

Evolution of Earth Like Planets

NASA Astrophysics Data System (ADS)

Monroy-Rodríguez, M. A.; Vega, K. M.

2017-07-01

In order to study and explain the evolution of our own planet we have done a review of works related to the evolution of Earth-like planets. From the stage of proto-planet to the loss of its atmosphere. The planetary formation from the gas and dust of the proto-planetary disk, considering the accretion by the process of migration, implies that the material on the proto-planet is very mixed. The newborn planet is hot and compact, it begins its process of stratification by gravity separation forming a super dense nucleus, an intermediate layer of convective mantle and an upper mantle that is less dense, with material that emerges from zones at very high pressure The surface with low pressure, in this process the planet expands and cools. This process also releases gas to the surface, forming the atmosphere, with the gas gravitationally bounded. The most important thing for the life of the planet is the layer of convective mantle, which produces the magnetic field, when it stops the magnetic field disappears, as well as the rings of van allen and the solar wind evaporates the atmosphere, accelerating the evolution and cooling of the planet. In a natural cycle of cataclysms and mass extinctions, the solar system crosses the galactic disk every 30 million years or so, the increase in the meteorite fall triggers the volcanic activity and the increase in the release of CO2 into the atmosphere reaching critical levels (4000 billion tons) leads us to an extinction by overheating that last 100 000 years, the time it takes CO2 to sediment to the ocean floor. Human activity will lead us to reach critical levels of CO2 in approximately 300 years.

Formation of Outer Planets: Overview

NASA Technical Reports Server (NTRS)

Lissauer, Jack

2003-01-01

An overview of current theories of planetary formation, with emphasis on giant planets is presented. The most detailed models are based upon observation of our own Solar System and of young stars and their environments. Terrestrial planets are believe 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. According to the prevailing core instability model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk disspates. The primary questions regarding the core instability model is whether planets with small cores can accrete gaseous enveloples within the lifetimes of gaseous protoplanetary disks. The main alternative giant planet formation model is the disk instability model, in which gaseous planets form directly via gravitational instabilities within protoplanetary disks. Formation of giant planets via gas instability has never been demonstrated for realistic disk conditions. Moreover, this model has difficulty explaining the supersolar abundances of heavy elements in Jupiter and Saturn, and it does not explain the orgin of planets like Uranus and Neptune.

The formation of giant planets in wide orbits by photoevaporation-synchronized migration

NASA Astrophysics Data System (ADS)

Guilera, O. M.; Miller Bertolami, M. M.; Ronco, M. P.

2017-10-01

The discovery of giant planets in wide orbits represents a major challenge for planet formation theory. In the standard core accretion paradigm, planets are expected to form at radial distances ≲20 au in order to form massive cores (with masses ≳10 M⊕) able to trigger the gaseous runaway growth before the dissipation of the disc. This has encouraged authors to find modifications of the standard scenario as well as alternative theories like the formation of planets by gravitational instabilities in the disc to explain the existence of giant planets in wide orbits. However, there is not yet consensus on how these systems are formed. In this Letter, we present a new natural mechanism for the formation of giant planets in wide orbits within the core accretion paradigm. If photoevaporation is considered, after a few Myr of viscous evolution a gap in the gaseous disc is opened. We found that, under particular circumstances planet migration becomes synchronized with the evolution of the gap, which results in an efficient outward planet migration. This mechanism is found to allow the formation of giant planets with masses Mp ≲ 1MJup in wide stable orbits as large as ∼130 au from the central star.

The Obliquities of the Giant Planets

NASA Astrophysics Data System (ADS)

Hamilton, D. P.; Ward, Wm. R.

2002-09-01

Jupiter has by far the smallest obliquity ( ~ 3o) of the planets (not counting tidally de-spun Mercury and Venus) which may be reflective of its formation by hydrodynamic gas flow rather than stochastic impacts. Saturn's obliquity ( ~ 26o), however, seems to belie this simple formation picture. But since the spin angular momentum of any planet is much smaller than its orbital angular momentum, post-formation obliquity can be strongly modified by passing through secular spin-orbit resonances, i.e., when the spin axis precession rate of the planet matches one of the frequencies describing the precession of the orbit plane. Spin axis precession is due to the solar torque on both the oblate figure of the planet and any orbiting satellites. In the case of Jupiter, the torque on the Galilean satellites is the principal cause of its 4.5*105 year precession; Saturn's precession of 1.8*106 years is dominated by Titan. In the past, the planetary spin axis precession rates should have been much faster due to the massive circumplanetary disks from which the current satellites condensed. The regression of the orbital node of a planet is due to the gravitational perturbations of the other planets. Nodal regression is not uniform, but is instead a composite of the planetary system's normal modes. For Jupiter and Saturn, the principal frequency is the nu16, with a period of ~ 49,000 years; the amplitude of this term is I ~ 0o.36 for Jupiter and I ~ 0o.90 for Saturn. In spite of the small amplitudes, slow adiabatic passages through this resonance (due to circumplanetary disk dispersal) could increase planetary obliquities from near zero to ~ [tan1/3 I] ~ 10o. We will discuss scenarios in which giant planet obliquities are affected by this and other resonances, and will use Jupiter's low obliquity to constrain the mass and duration of a satellite precursor disk. DPH acknowledges support from NSF Career Grant AST 9733789 and WRW is grateful to the NASA OSS and PGG programs.

Planet Formation - Overview

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.

2005-01-01

Modern theories of star and planet formation are based upon observations of planets and smaller bodies within our own Solar System, exoplanets &round normal stars and of young stars and their environments. 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 planets begin their growth as do terrestrial planets, but they become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. These models predict that rocky planets should form in orbit about most single stars. It is uncertain whether or not gas giant planet formation is common, because most protoplanetary disks may dissipate before solid planetary cores can grow large enough to gravitationally trap substantial quantities of gas. A potential hazard to planetary systems is radial decay of planetary orbits resulting from interactions with material within the disk. Planets more massive than Earth have the potential to decay the fastest, and may be able to sweep up smaller planets in their path.

New and updated stellar parameters for 71 evolved planet hosts. On the metallicity-giant planet connection

NASA Astrophysics Data System (ADS)

Mortier, A.; Santos, N. C.; Sousa, S. G.; Adibekyan, V. Zh.; Delgado Mena, E.; Tsantaki, M.; Israelian, G.; Mayor, M.

2013-09-01

Context. It is still being debated whether the well-known metallicity-giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. Aims: To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity-giant planet connection for evolved stars. Methods: A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. Results: All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (log g < 3.0 dex) with respect to red giants without

Formation of Large Regular Satellites of Giant Planets in an Extended Gaseous Nebula: Subnebula Model and Accretion of Satellites

NASA Technical Reports Server (NTRS)

Mosqueira, I.; Estrada, P. R.

2000-01-01

We model the subnebulae of Jupiter and Saturn wherein satellite accretion took place. We expect a giant planet subnebula to be composed of an optically thick (given gaseous opacity) inner region inside of the planet's centrifugal radius (located at r(sub c, sup J) = l5R(sub J) for Jupiter and r(sub c, sup S) = 22R(sub S) for Saturn), and an optically thin, extended outer disk out to a fraction of the planet's Roche lobe, which we choose to be R(sub roche)/5 (located at approximately 150R(sub J) near the inner irregular satellites for Jupiter, and approximately 200R(sub S) near Phoebe for Saturn). This places Titan and Ganymede in the inner disk, Callisto and Iapetus in the outer disk, and Hyperion in the transition region. The inner disk is the leftover of the gas accreted by the protoplanet. The outer disk results from the solar torque on nebula gas flowing into the protoplanet during the time of giant planet gap opening. For the sake of specificity, we use a cosmic mixture 'minimum mass' model to constrain the gas densities of the inner disks of Jupiter and Saturn (and also Uranus). For the total mass of the outer disk we use the simple scaling M(sub disk) = M(sub P)tau(sub gap)/tau(sub acc), where M(sub P) is the mass of the giant planet, tau(sub gap) is the gap opening timescale, and tau(sub acc) is the giant planet accretion time. This gives a total outer disk mass of approximately 100M(sub Callisto) for Jupiter and possibly approximately 200M(sub Iapetus) for Saturn (which contain enough condensables to form Callisto and Iapetus respectively). Our model has Ganymede at a subnebula temperature of approximately 250 K and Titan at approximately 100 K. The outer disks of Jupiter and Saturn have constant temperatures of 130 K and 90 K respectively.

The Evolution of Gas Giant Entropy During Formation by Runaway Accretion

NASA Astrophysics Data System (ADS)

Berardo, David; Cumming, Andrew; Marleau, Gabriel-Dominique

2017-01-01

We calculate the evolution of gas giant planets during the runaway gas accretion phase of formation, to understand how the luminosity of young giant planets depends on the accretion conditions. We construct steady-state envelope models, and run time-dependent simulations of accreting planets with the code Modules for Experiments in Stellar Astrophysics. We show that the evolution of the internal entropy depends on the contrast between the internal adiabat and the entropy of the accreted material, parametrized by the shock temperature T 0 and pressure P 0. At low temperatures ({T}0≲ 300-1000 {{K}}, depending on model parameters), the accreted material has a lower entropy than the interior. The convection zone extends to the surface and can drive a high luminosity, leading to rapid cooling and cold starts. For higher temperatures, the accreted material has a higher entropy than the interior, giving a radiative zone that stalls cooling. For {T}0≳ 2000 {{K}}, the surface-interior entropy contrast cannot be accommodated by the radiative envelope, and the accreted matter accumulates with high entropy, forming a hot start. The final state of the planet depends on the shock temperature, accretion rate, and starting entropy at the onset of runaway accretion. Cold starts with L≲ 5× {10}-6 {L}⊙ require low accretion rates and starting entropy, and the temperature of the accreting material needs to be maintained close to the nebula temperature. If instead the temperature is near the value required to radiate the accretion luminosity, 4π {R}2σ {T}04˜ ({GM}\\dot{M}/R), as suggested by previous work on radiative shocks in the context of star formation, gas giant planets form in a hot start with L˜ {10}-4 {L}⊙ .

How Turbulence Can Set the Radial Distribution of Gas Giants Formed by Pebble Accretion

NASA Astrophysics Data System (ADS)

Morley Rosenthal, Mickey; Murray-Clay, Ruth

2018-04-01

I discuss how turbulence impacts the orbital separation at which the cores of gas giants can form via pebble accretion. While pebble accretion is extremely rapid for massive planets, I demonstrate that pebble accretion is inhibited at protoplanet masses, an effect which is strongly enhanced in a turbulent disk. Using these considerations I derive a “minimum” mass, past which pebble accretion proceeds on timescales less than the disk lifetime. By considering core formation where early growth to this minimum mass proceeds by gravitational focusing of planetesimals, I demonstrate that the the semi-major axes where gas giants can form are more restricted as the strength of the nebular turbulence increases — e.g. formation can only occur at distances < 30 AU for α > 10^-2. I also examine the implications of turbulence on the mass gas giants can reach before opening a substantial gap and halting growth. I find that while weak turbulence allows gas giants to form far out in the disk, the masses of these planets are substantially lower (< 1 Jupiter mass), which would preclude them from having been detected by the current generation of direct imaging surveys.

JUPITER WILL BECOME A HOT JUPITER: CONSEQUENCES OF POST-MAIN-SEQUENCE STELLAR EVOLUTION ON GAS GIANT PLANETS

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

Spiegel, David S.; Madhusudhan, Nikku, E-mail: dave@ias.edu, E-mail: Nikku.Madhusudhan@yale.edu

When the Sun ascends the red giant branch (RGB), its luminosity will increase and all the planets will receive much greater irradiation than they do now. Jupiter, in particular, might end up more highly irradiated than the hot Neptune GJ 436b and, hence, could appropriately be termed a 'hot Jupiter'. When their stars go through the RGB or asymptotic giant branch stages, many of the currently known Jupiter-mass planets in several-AU orbits will receive levels of irradiation comparable to the hot Jupiters, which will transiently increase their atmospheric temperatures to {approx}1000 K or more. Furthermore, massive planets around post-main-sequence starsmore » could accrete a non-negligible amount of material from the enhanced stellar winds, thereby significantly altering their atmospheric chemistry as well as causing a significant accretion luminosity during the epochs of most intense stellar mass loss. Future generations of infrared observatories might be able to probe the thermal and chemical structure of such hot Jupiters' atmospheres. Finally, we argue that, unlike their main-sequence analogs (whose zonal winds are thought to be organized in only a few broad, planetary-scale jets), red-giant hot Jupiters should have multiple, narrow jets of zonal winds and efficient day-night redistribution.« less

Do Close-in Giant Planets Orbiting Evolved Stars Prefer Eccentric Orbits?

NASA Astrophysics Data System (ADS)

Grunblatt, Samuel K.; Huber, Daniel; Gaidos, Eric; Lopez, Eric D.; Barclay, Thomas; Chontos, Ashley; Sinukoff, Evan; Van Eylen, Vincent; Howard, Andrew W.; Isaacson, Howard T.

2018-07-01

The NASA Kepler and K2 Missions have recently revealed a population of transiting giant planets orbiting moderately evolved, low-luminosity red giant branch stars. Here, we present radial velocity (RV) measurements of three of these systems, revealing significantly non-zero orbital eccentricities in each case. Comparing these systems with the known planet population suggests that close-in giant planets around evolved stars tend to have more eccentric orbits than those around main sequence stars. We interpret this as tentative evidence that the orbits of these planets pass through a transient, moderately eccentric phase where they shrink faster than they circularize due to tides raised on evolved host stars. Additional RV measurements of currently known systems, along with new systems discovered by the recently launched NASA Transiting Exoplanet Survey Satellite (TESS) mission, may constrain the timescale and mass dependence of this process.

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

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.

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.

Kepler-432: A Red Giant Interacting with One of its Two Long-period Giant Planets

NASA Astrophysics Data System (ADS)

Quinn, Samuel N.; White, Timothy. R.; Latham, David W.; Chaplin, William J.; Handberg, Rasmus; Huber, Daniel; Kipping, David M.; Payne, Matthew J.; Jiang, Chen; Silva Aguirre, Victor; Stello, Dennis; Sliski, David H.; Ciardi, David R.; Buchhave, Lars A.; Bedding, Timothy R.; Davies, Guy R.; Hekker, Saskia; Kjeldsen, Hans; Kuszlewicz, James S.; Everett, Mark E.; Howell, Steve B.; Basu, Sarbani; Campante, Tiago L.; Christensen-Dalsgaard, Jørgen; Elsworth, Yvonne P.; Karoff, Christoffer; Kawaler, Steven D.; Lund, Mikkel N.; Lundkvist, Mia; Esquerdo, Gilbert A.; Calkins, Michael L.; Berlind, Perry

2015-04-01

We report the discovery of Kepler-432b, a giant planet ({{M}b}=5.41-0.18+0.32 {{M}Jup}, {{R}b}=1.145-0.039+0.036 {{R}Jup}) transiting an evolved star ({{M}\\star }=1.32-0.07+0.10 {{M}⊙ },{{R}\\star }=4.06-0.08+0.12 {{R}⊙ }) with an orbital period of {{P}b}=52.501129-0.000053+0.000067 days. Radial velocities (RVs) reveal that Kepler-432b orbits its parent star with an eccentricity of e=0.5134-0.0089+0.0098, which we also measure independently with asterodensity profiling (AP; e=0.507-0.114+0.039), thereby confirming the validity of AP on this particular evolved star. The well-determined planetary properties and unusually large mass also make this planet an important benchmark for theoretical models of super-Jupiter formation. Long-term RV monitoring detected the presence of a non-transiting outer planet (Kepler-432c; {{M}c}sin {{i}c}=2.43-0.24+0.22 {{M}Jup}, {{P}c}=406.2-2.5+3.9 days), and adaptive optics imaging revealed a nearby (0\\buildrel{\\prime\\prime}\\over{.} 87), faint companion (Kepler-432B) that is a physically bound M dwarf. The host star exhibits high signal-to-noise ratio asteroseismic oscillations, which enable precise measurements of the stellar mass, radius, and age. Analysis of the rotational splitting of the oscillation modes additionally reveals the stellar spin axis to be nearly edge-on, which suggests that the stellar spin is likely well aligned with the orbit of the transiting planet. Despite its long period, the obliquity of the 52.5 day orbit may have been shaped by star-planet interaction in a manner similar to hot Jupiter systems, and we present observational and theoretical evidence to support this scenario. Finally, as a short-period outlier among giant planets orbiting giant stars, study of Kepler-432b may help explain the distribution of massive planets orbiting giant stars interior to 1 AU.

Full exploration of the giant planet population around β Pictoris

NASA Astrophysics Data System (ADS)

Lagrange, A.-M.; Keppler, M.; Meunier, N.; Lannier, J.; Beust, H.; Milli, J.; Bonnavita, M.; Bonnefoy, M.; Borgniet, S.; Chauvin, G.; Delorme, P.; Galland, F.; Iglesias, D.; Kiefer, F.; Messina, S.; Vidal-Madjar, A.; Wilson, P. A.

2018-05-01

Context. The search for extrasolar planets has been limited so far to close orbit (typ. ≤5 au) planets around mature solar-type stars on the one hand, and to planets on wide orbits (≥10 au) around young stars on the other hand. To get a better view of the full giant planet population, we have started a survey to search for giant planets around a sample of carefully selected young stars. Aims: This paper aims at exploring the giant planet population around one of our targets, β Pictoris, over a wide range of separations. With a disk and a planet already known, the β Pictoris system is indeed a very precious system for studies of planetary formation and evolution, as well as of planet-disk interactions. Methods: We analyse more than 2000 HARPS high-resolution spectra taken over 13 years as well as NaCo images recorded between 2003 and 2016. We combine these data to compute the detection probabilities of planets throughout the disk, from a fraction of au to a few dozen au. Results: We exclude the presence of planets more massive than 3 MJup closer than 1 au and further than 10 au, with a 90% probability. 15+ MJup companions are excluded throughout the disk except between 3 and 5 au with a 90% probability. In this region, we exclude companions with masses larger than 18 (resp. 30) MJup with probabilities of 60 (resp. 90) %. Based on data obtained with the ESO3.6 m/HARPS spectrograph at La Silla, and with NaCO on the VLT.The RV data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A108

High surface magnetic field in red giants as a new signature of planet engulfment?

NASA Astrophysics Data System (ADS)

Privitera, Giovanni; Meynet, Georges; Eggenberger, Patrick; Georgy, Cyril; Ekström, Sylvia; Vidotto, Aline A.; Bianda, Michele; Villaver, Eva; ud-Doula, Asif

2016-09-01

Context. Red giant stars may engulf planets. This may increase the rotation rate of their convective envelope, which could lead to strong dynamo-triggered magnetic fields. Aims: We explore the possibility of generating magnetic fields in red giants that have gone through the process of a planet engulfment. We compare them with similar models that evolve without any planets. We discuss the impact of magnetic braking through stellar wind on the evolution of the surface velocity of the parent star. Methods: By studying rotating stellar models with and without planets and an empirical relation between the Rossby number and the surface magnetic field, we deduced the evolution of the surface magnetic field along the red giant branch. The effects of stellar wind magnetic braking were explored using a relation deduced from magnetohydrodynamics simulations. Results: The stellar evolution model of a red giant with 1.7 M⊙ without planet engulfment and with a time-averaged rotation velocity during the main sequence equal to 100 km s-1 shows a surface magnetic field triggered by convection that is stronger than 10 G only at the base of the red giant branch, that is, for gravities log g> 3. When a planet engulfment occurs, this magnetic field can also appear at much lower gravities, that is, at much higher luminosities along the red giant branch. The engulfment of a 15 MJ planet typically produces a dynamo-triggered magnetic field stronger than 10 G for gravities between 2.5 and 1.9. We show that for reasonable magnetic braking laws for the wind, the high surface velocity reached after a planet engulfment may be maintained sufficiently long to be observable. Conclusions: High surface magnetic fields for red giants in the upper part of the red giant branch are a strong indication of a planet engulfment or of an interaction with a companion. Our theory can be tested by observing fast-rotating red giants such as HD 31994, Tyc 0347-00762-1, Tyc 5904-00513-1, and Tyc 6054

The Longevity of Water Ice on Ganymedes and Europas around Migrated Giant Planets

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

Lehmer, Owen R.; Catling, David C.; Zahnle, Kevin J., E-mail: olehmer@gmail.com

The gas giant planets in the Solar System have a retinue of icy moons, and we expect giant exoplanets to have similar satellite systems. If a Jupiter-like planet were to migrate toward its parent star the icy moons orbiting it would evaporate, creating atmospheres and possible habitable surface oceans. Here, we examine how long the surface ice and possible oceans would last before being hydrodynamically lost to space. The hydrodynamic loss rate from the moons is determined, in large part, by the stellar flux available for absorption, which increases as the giant planet and icy moons migrate closer to themore » star. At some planet–star distance the stellar flux incident on the icy moons becomes so great that they enter a runaway greenhouse state. This runaway greenhouse state rapidly transfers all available surface water to the atmosphere as vapor, where it is easily lost from the small moons. However, for icy moons of Ganymede’s size around a Sun-like star we found that surface water (either ice or liquid) can persist indefinitely outside the runaway greenhouse orbital distance. In contrast, the surface water on smaller moons of Europa’s size will only persist on timescales greater than 1 Gyr at distances ranging 1.49–0.74 au around a Sun-like star for Bond albedos of 0.2 and 0.8, where the lower albedo becomes relevant if ice melts. Consequently, small moons can lose their icy shells, which would create a torus of H atoms around their host planet that might be detectable in future observations.« less

On the Composition of Young, Directly Imaged Giant Planets

NASA Technical Reports Server (NTRS)

Moses, J. I.; Marley, M. S.; Zahnle, K.; Line, M. R.; Fortney, J. J.; Barman, T. S.; Visscher, C.; Lewis, N. K.; Wolff, M. J.

2016-01-01

The past decade has seen significant progress on the direct detection and characterization of young, self-luminous giant planets at wide orbital separations from their host stars. Some of these planets show evidence for disequilibrium processes like transport-induced quenching in their atmospheres; photochemistry may also be important, despite the typically large orbital distances. Disequilibrium chemical processes such as these can alter the expected composition, spectral behavior, thermal structure, and cooling history of the planets, and can potentially confuse determinations of bulk elemental ratios, which provide important insights into planet-formation mechanisms. Using a thermo/photochemical kinetics and transport model, we investigate the extent to which disequilibrium chemical processes affect the composition and spectra of directly imaged giant exoplanets. Results for specific "young Jupiters" such as HR 8799 b and c and 51 Eri b are presented, as are general trends as a function of planetary effective temperature, surface gravity, incident ultraviolet flux, and strength of deep atmospheric convection. We find that quenching is very important on young Jupiters, leading to CO/CH4 and N2/NH3 ratios much greater than; and H2O mixing ratios a factor of a few less than chemical equilibrium predictions. Photochemistry can also be important on such planets, with CO2 and HCN being key photochemical products. Carbon dioxide becomes a particularly major constituent when stratospheric temperatures are low and recycling of water following H2O photolysis becomes stifled. Young Jupiters with effective temperatures less than 700 degrees Kelvin are in a particularly interesting photochemical regime that differs from both transiting hot Jupiters and our own solar-system giant planets.

Characterizing Cool Giant Planets in Reflected Light

NASA Technical Reports Server (NTRS)

Marley, Mark

2016-01-01

While the James Webb Space Telescope will detect and characterize extrasolar planets by transit and direct imaging, a new generation of telescopes will be required to detect and characterize extrasolar planets by reflected light imaging. NASA's WFIRST space telescope, now in development, will image dozens of cool giant planets at optical wavelengths and will obtain spectra for several of the best and brightest targets. This mission will pave the way for the detection and characterization of terrestrial planets by the planned LUVOIR or HabEx space telescopes. In my presentation I will discuss the challenges that arise in the interpretation of direct imaging data and present the results of our group's effort to develop methods for maximizing the science yield from these planned missions.

Characterizing Cold Giant Planets in Reflected Light: Lessons from 50 Years of Outer Solar System Exploration and Observation

NASA Technical Reports Server (NTRS)

Marley, Mark Scott; Hammel, Heidi

2014-01-01

A space based coronagraph, whether as part of the WFIRST/AFTA mission or on a dedicated space telescope such as Exo-C or -S, will be able to obtain photometry and spectra of multiple gas giant planets around nearby stars, including many known from radial velocity detections. Such observations will constrain the masses, atmospheric compositions, clouds, and photochemistry of these worlds. Giant planet albedo models, such as those of Cahoy et al. (2010) and Lewis et al. (this meeting), will be crucial for mission planning and interpreting the data. However it is equally important that insights gleaned from decades of solar system imaging and spectroscopy of giant planets be leveraged to optimize both instrument design and data interpretation. To illustrate these points we will draw on examples from solar system observations, by both HST and ground based telescopes, as well as by Voyager, Galileo, and Cassini, to demonstrate the importance clouds, photochemical hazes, and various molecular absorbers play in sculpting the light scattered by solar system giant planets. We will demonstrate how measurements of the relative depths of multiple methane absorption bands of varying strengths have been key to disentangling the competing effects of gas column abundances, variations in cloud height and opacity, and scattering by high altitude photochemical hazes. We will highlight both the successes, such as the accurate remote determination of the atmospheric methane abundance of Jupiter, and a few failures from these types of observations. These lessons provide insights into technical issues facing spacecraft designers, from the selection of the most valuable camera filters to carry to the required capabilities of the flight spectrometer, as well as mission design questions such as choosing the most favorable phase angles for atmospheric characterization.

Origin of the orbital architecture of the giant planets of the Solar System.

PubMed

Tsiganis, K; Gomes, R; Morbidelli, A; Levison, H F

2005-05-26

Planetary formation theories suggest that the giant planets formed on circular and coplanar orbits. The eccentricities of Jupiter, Saturn and Uranus, however, reach values of 6 per cent, 9 per cent and 8 per cent, respectively. In addition, the inclinations of the orbital planes of Saturn, Uranus and Neptune take maximum values of approximately 2 degrees with respect to the mean orbital plane of Jupiter. Existing models for the excitation of the eccentricity of extrasolar giant planets have not been successfully applied to the Solar System. Here we show that a planetary system with initial quasi-circular, coplanar orbits would have evolved to the current orbital configuration, provided that Jupiter and Saturn crossed their 1:2 orbital resonance. We show that this resonance crossing could have occurred as the giant planets migrated owing to their interaction with a disk of planetesimals. Our model reproduces all the important characteristics of the giant planets' orbits, namely their final semimajor axes, eccentricities and mutual inclinations.

OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N{sub 2} FORMATION BY IMPACT SHOCK

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

Ishimaru, Ryo; Matsui, Takafumi; Sekine, Yasuhito

2011-11-01

Titan is the only satellite that possesses a thick atmosphere, composed mainly of N{sub 2} and CH{sub 4}. However, its origin and evolution remain largely unknown. Knowledge of the acquirement of a N{sub 2} atmosphere on Titan would provide insights into nitrogen evolution in planetary atmospheres as well as the formation of satellite systems around gas giants. Previous studies have proposed that the atmospheric N{sub 2} would have been converted from NH{sub 3} via shock heating by accreting satellitesimals in the highly reducing proto-atmosphere composed of NH{sub 3} and CH{sub 4}. Nevertheless, the validity of this mechanism strongly depends onmore » both the composition of the proto-atmosphere and kinetics of shock chemistry. Here, we show that a CO{sub 2}-rich oxidizing proto-atmosphere is necessary to form N{sub 2} from NH{sub 3} efficiently by atmospheric shock heating. Efficient shock production of N{sub 2} is inhibited in a reducing proto-atmosphere composed of NH{sub 3} and CH{sub 4}, because CH{sub 4} plays as the coolant gas owing to its large heat capacity. Our calculations show that the amount of N{sub 2} produced in a CO{sub 2}-rich proto-atmosphere could have reached {approx}20 times that on the present Titan. Although further quantitative analysis are required (especially, the occurrence of catalytic reactions), our results imply that the chemical composition of satellitesimals that formed the Saturnian system is required to be oxidizing if the current atmospheric N{sub 2} is derived from the shock heating in the proto-atmosphere during accretion. This supports the formation of regular satellites in an actively supplied circumplanetary disk using CO{sub 2}-rich materials originated from the solar nebula at the final stage of gas giant formation.« less

The atmospheres of earthlike planets after giant impact events

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

Lupu, R. E.; Freedman, Richard; Zahnle, Kevin

2014-03-20

It is now understood that the accretion of terrestrial planets naturally involves giant collisions, the moon-forming impact being a well-known example. In the aftermath of such collisions, the surface of the surviving planet is very hot and potentially detectable. Here we explore the atmospheric chemistry, photochemistry, and spectral signatures of post-giant-impact terrestrial planets enveloped by thick atmospheres consisting predominantly of CO{sub 2} and H{sub 2}O. The atmospheric chemistry and structure are computed self-consistently for atmospheres in equilibrium with hot surfaces with composition reflecting either the bulk silicate Earth (which includes the crust, mantle, atmosphere, and oceans) or Earth's continental crust.more » We account for all major molecular and atomic opacity sources including collision-induced absorption. We find that these atmospheres are dominated by H{sub 2}O and CO{sub 2}, while the formation of CH{sub 4} and NH{sub 3} is quenched because of short dynamical timescales. Other important constituents are HF, HCl, NaCl, and SO{sub 2}. These are apparent in the emerging spectra and can be indicative that an impact has occurred. The use of comprehensive opacities results in spectra that are a factor of two lower brightness temperature in the spectral windows than predicted by previous models. The estimated luminosities show that the hottest post-giant-impact planets will be detectable with near-infrared coronagraphs on the planned 30 m class telescopes. The 1-4 μm will be most favorable for such detections, offering bright features and better contrast between the planet and a potential debris disk. We derive cooling timescales on the order of 10{sup 5-6} yr on the basis of the modeled effective temperatures. This leads to the possibility of discovering tens of such planets in future surveys.« less

Search for giant planets in M 67. IV. Survey results

NASA Astrophysics Data System (ADS)

Brucalassi, A.; Koppenhoefer, J.; Saglia, R.; Pasquini, L.; Ruiz, M. T.; Bonifacio, P.; Bedin, L. R.; Libralato, M.; Biazzo, K.; Melo, C.; Lovis, C.; Randich, S.

2017-07-01

Context. We present the results of a seven-year-long radial velocity survey of a sample of 88 main-sequence and evolved stars to reveal signatures of Jupiter-mass planets in the solar-age and solar-metallicity open cluster M 67. Aims: We aim at studying the frequency of giant planets in this cluster with respect to the field stars. In addition, our sample is also ideal to perform a long-term study to compare the chemical composition of stars with and without giant planets in detail. Methods: We analyzed precise radial velocity (RV) measurements obtained with the HARPS spectrograph at the European Southern Observatory (La Silla), the SOPHIE spectrograph at the Observatoire de Haute-Provence (France), the HRS spectrograph at the Hobby Eberly Telescope (Texas), and the HARPS-N spectrograph at the Telescopio Nazionale Galileo (La Palma). Additional RV data come from the CORALIE spectrograph at the Euler Swiss Telescope (La Silla). We conducted Monte Carlo simulations to estimate the occurrence rate of giant planets in our radial velocity survey. We considered orbital periods between 1.0 day and 1000 days and planet masses between 0.2 MJ and 10.0 MJ. We used a measure of the observational detection efficiency to determine the frequency of planets for each star. Results: All the planets previously announced in this RV campaign with their properties are summarized here: 3 hot Jupiters around the main-sequence stars YBP1194, YBP1514, and YBP401, and 1 giant planet around the evolved star S364. Two additional planet candidates around the stars YBP778 and S978 are also analyzed in the present work. We discuss stars that exhibit large RV variability or trends individually. For 2 additional stars, long-term trends are compatible with new binary candidates or substellar objects, which increases the total number of binary candidates detected in our campaign to 14. Based on the Doppler-detected planets discovered in this survey, we find an occurrence of giant planets of 18

CORRELATIONS BETWEEN COMPOSITIONS AND ORBITS ESTABLISHED BY THE GIANT IMPACT ERA OF PLANET FORMATION

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

Dawson, Rebekah I.; Lee, Eve J.; Chiang, Eugene, E-mail: rdawson@psu.edu

The giant impact phase of terrestrial planet formation establishes connections between super-Earths’ orbital properties (semimajor axis spacings, eccentricities, mutual inclinations) and interior compositions (the presence or absence of gaseous envelopes). Using N -body simulations and analytic arguments, we show that spacings derive not only from eccentricities, but also from inclinations. Flatter systems attain tighter spacings, a consequence of an eccentricity equilibrium between gravitational scatterings, which increase eccentricities, and mergers, which damp them. Dynamical friction by residual disk gas plays a critical role in regulating mergers and in damping inclinations and eccentricities. Systems with moderate gas damping and high solid surfacemore » density spawn gas-enveloped super-Earths with tight spacings, small eccentricities, and small inclinations. Systems in which super-Earths coagulate without as much ambient gas, in disks with low solid surface density, produce rocky planets with wider spacings, larger eccentricities, and larger mutual inclinations. A combination of both populations can reproduce the observed distributions of spacings, period ratios, transiting planet multiplicities, and transit duration ratios exhibited by Kepler super-Earths. The two populations, both formed in situ, also help to explain observed trends of eccentricity versus planet size, and bulk density versus method of mass measurement (radial velocities versus transit timing variations). Simplifications made in this study—including the limited time span of the simulations, and the approximate treatments of gas dynamical friction and gas depletion history—should be improved on in future work to enable a detailed quantitative comparison to the observations.« less

When Push Comes to Shove: Gap-opening, Disk Clearing and the In Situ Formation of Giant Planets

NASA Technical Reports Server (NTRS)

Mosqueira, I.; Estrada, P. R.

2004-01-01

Here we investigate a scenario in which cores as small as a few Earth masses stall in the terrestrial planet region, but continue to grow as a result of the Type I migration of other Earth sized objects, taking place in a timescale approx. 10(exp 6) years similar to the disk clearing timescale (such migration may thus significantly reduce the accretion efficiency, particularly in the terrestrial planet region). Since the core may intercept such inwardly migrating objects (possibly by altering the surface density to the point that the object stalls within the core's feeding zone) or coalesce with neighboring cores, its growth may continue until it reaches a CCM. The question then arises whether such a core can accrete enough gas to become a Jovian-sized giant planet. In the limit of low opacity (such that the protoplanet s tidal torque fails to clear gas from its feeding zone in time to prevent its accretion), the final mass of the planet is given by the gaseous isolation mass (provided alpha is < or approx. = 10(exp -4) and that the gas component dominates the planet's mass).

Circumplanetary discs around young giant planets: a comparison between core-accretion and disc instability

NASA Astrophysics Data System (ADS)

Szulágyi, J.; Mayer, L.; Quinn, T.

2017-01-01

Circumplanetary discs can be found around forming giant planets, regardless of whether core accretion or gravitational instability built the planet. We carried out state-of-the-art hydrodynamical simulations of the circumplanetary discs for both formation scenarios, using as similar initial conditions as possible to unveil possible intrinsic differences in the circumplanetary disc mass and temperature between the two formation mechanisms. We found that the circumplanetary discs' mass linearly scales with the circumstellar disc mass. Therefore, in an equally massive protoplanetary disc, the circumplanetary discs formed in the disc instability model can be only a factor of 8 more massive than their core-accretion counterparts. On the other hand, the bulk circumplanetary disc temperature differs by more than an order of magnitude between the two cases. The subdiscs around planets formed by gravitational instability have a characteristic temperature below 100 K, while the core-accretion circumplanetary discs are hot, with temperatures even greater than 1000 K when embedded in massive, optically thick protoplanetary discs. We explain how this difference can be understood as the natural result of the different formation mechanisms. We argue that the different temperatures should persist up to the point when a full-fledged gas giant forms via disc instability; hence, our result provides a convenient criterion for observations to distinguish between the two main formation scenarios by measuring the bulk temperature in the planet vicinity.

THE CALIFORNIA PLANET SURVEY IV: A PLANET ORBITING THE GIANT STAR HD 145934 AND UPDATES TO SEVEN SYSTEMS WITH LONG-PERIOD PLANETS

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

Katherina Feng, Y.; Wright, Jason T.; Nelson, Benjamin

2015-02-10

We present an update to seven stars with long-period planets or planetary candidates using new and archival radial velocities from Keck-HIRES and literature velocities from other telescopes. Our updated analysis better constrains orbital parameters for these planets, four of which are known multi-planet systems. HD 24040 b and HD 183263 c are super-Jupiters with circular orbits and periods longer than 8 yr. We present a previously unseen linear trend in the residuals of HD 66428 indicative of an additional planetary companion. We confirm that GJ 849 is a multi-planet system and find a good orbital solution for the c component: it is a 1more » M {sub Jup} planet in a 15 yr orbit (the longest known for a planet orbiting an M dwarf). We update the HD 74156 double-planet system. We also announce the detection of HD 145934 b, a 2 M {sub Jup} planet in a 7.5 yr orbit around a giant star. Two of our stars, HD 187123 and HD 217107, at present host the only known examples of systems comprising a hot Jupiter and a planet with a well constrained period greater than 5 yr, and with no evidence of giant planets in between. Our enlargement and improvement of long-period planet parameters will aid future analysis of origins, diversity, and evolution of planetary systems.« less

Observationally Constraining Gas Giant Composition via Their Host Star Abundances

NASA Astrophysics Data System (ADS)

Teske, Johanna; Thorngren, Daniel; Fortney, Jonathan

2018-01-01

While the photospheric abundances of the Sun match many rock-forming elemental abundances in the Earth to within 10 mol%, as well as in Mars, the Moon, and meteorites, the Solar System giant planets are of distinctly non-stellar composition — Jupiter's bulk metallicity (inferred from its bulk density, measured from spacecraft data) is ∼ x5-10 solar, and Saturn is ∼ x10-20 solar. This knowledge has led to dramatic advances in understanding models of core accretion, which now match the heavy element enrichment of each of the Solar System's giant planets. However, we have thus far lacked similar data for exoplanets to use as a check for formation and composition models over a much larger parameter space. Here we present a study of the host stars of a sample of cool transiting gas giants with measured bulk metal fractions (as in Thorngren et al. 2016) to better constrain the relation Zplanet/Zstar — giant exoplanet metal enrichment relative to the host star. We add a new dimension of chemical variation, measuring C, O, Mg, Si, Ni, and well as Fe (on which previous Zplanet/Zstar calculations were based). Our analysis provides the best constraints to date on giant exoplanet interior composition and how this relates to formation environment, and make testable predictions for JWST observations of exoplanet atmospheres.

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.

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

A NEW HYBRID N-BODY-COAGULATION CODE FOR THE FORMATION OF GAS GIANT 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

2011-04-20

We describe an updated version of our hybrid N-body-coagulation code for planet formation. In addition to the features of our 2006-2008 code, our treatment now includes algorithms for the one-dimensional evolution of the viscous disk, the accretion of small particles in planetary atmospheres, gas accretion onto massive cores, and the response of N-bodies to the gravitational potential of the gaseous disk and the swarm of planetesimals. To validate the N-body portion of the algorithm, we use a battery of tests in planetary dynamics. As a first application of the complete code, we consider the evolution of Pluto-mass planetesimals in amore » swarm of 0.1-1 cm pebbles. In a typical evolution time of 1-3 Myr, our calculations transform 0.01-0.1 M{sub sun} disks of gas and dust into planetary systems containing super-Earths, Saturns, and Jupiters. Low-mass planets form more often than massive planets; disks with smaller {alpha} form more massive planets than disks with larger {alpha}. For Jupiter-mass planets, masses of solid cores are 10-100 M{sub +}.« less

Giant Impacts and Earth's Primordial Atmosphere

NASA Astrophysics Data System (ADS)

Agnor, C.; Asphaug, E.

2002-09-01

Estimates of Earth's accretion timescale based on modeling (e.g. Wetherill 1990) and isotopic evidence (Halliday and Porcelli 2000) indicate that the Earth formed in 25-100 Myr. At least a portion of this accretion took place in the presence of the solar nebula. While the problem of nailing down the nebular lifetime remains open, observations of dust disks surrounding young stars and meteoritic evidence suggest that the gas disk existed and was involved in making planetary material for 10 Myr (e.g. Podosek & Cassen 1994, Trilling et al. 2001). The persistence of a remnant of the nebula's original gas disk during terrestrial planet accretion is certainly plausible. The existence of this remnant nebula has dynamical (Agnor & Ward 2002, Kominami & Ida 2002) and geochemical (Porcelli & Pepin 2000) implications for terrestrial planet formation. Nakazawa et al. (1985) explored the structure of Earth's primordial atmosphere as the solar nebula was dissipating. They found that even for low surface densities of nebular gas ( σ gas ~ 1 g cm-2 or ~0.1% of the minimum mass nebula), Earth can capture a significant primordial atmosphere directly from the nebula (i.e. total mass up to a few lunar masses, or ~ 105 times the current atmosphere). Such a massive primordial atmosphere may have played a dynamical role in the formation of the Moon (e.g. models of lunar capture have employed aerodynamic drag in Earth's atmosphere as the primary mechanism for reducing the Moon's orbital energy, Nakazawa et al. 1983). Conversely, the formation of the Moon may have played a role in removing Earth's primordial atmosphere. Giant impacts have been suggested as one possible mechanism that could accomplish global atmospheric removal (Ahrens 1993). We are using smooth particle hydrodynamics (SPH) to model the removal of Earth's primordial atmosphere via giant impact. We employ initial conditions similar to recent works on lunar formation (e.g. Canup & Asphaug 2001) but also include ideal gas

Pebble-isolation mass: Scaling law and implications for the formation of super-Earths and gas giants

NASA Astrophysics Data System (ADS)

Bitsch, Bertram; Morbidelli, Alessandro; Johansen, Anders; Lega, Elena; Lambrechts, Michiel; Crida, Aurélien

2018-04-01

The growth of a planetary core by pebble accretion stops at the so-called pebble isolation mass, when the core generates a pressure bump that traps drifting pebbles outside its orbit. The value of the pebble isolation mass is crucial in determining the final planet mass. If the isolation mass is very low, gas accretion is protracted and the planet remains at a few Earth masses with a mainly solid composition. For higher values of the pebble isolation mass, the planet might be able to accrete gas from the protoplanetary disc and grow into a gas giant. Previous works have determined a scaling of the pebble isolation mass with cube of the disc aspect ratio. Here, we expand on previous measurements and explore the dependency of the pebble isolation mass on all relevant parameters of the protoplanetary disc. We use 3D hydrodynamical simulations to measure the pebble isolation mass and derive a simple scaling law that captures the dependence on the local disc structure and the turbulent viscosity parameter α. We find that small pebbles, coupled to the gas, with Stokes number τf < 0.005 can drift through the partial gap at pebble isolation mass. However, as the planetary mass increases, particles must be decreasingly smaller to penetrate the pressure bump. Turbulent diffusion of particles, however, can lead to an increase of the pebble isolation mass by a factor of two, depending on the strength of the background viscosity and on the pebble size. We finally explore the implications of the new scaling law of the pebble isolation mass on the formation of planetary systems by numerically integrating the growth and migration pathways of planets in evolving protoplanetary discs. Compared to models neglecting the dependence of the pebble isolation mass on the α-viscosity, our models including this effect result in higher core masses for giant planets. These higher core masses are more similar to the core masses of the giant planets in the solar system.

Thoughts on the Theory of Irradiated Giant Planets

NASA Astrophysics Data System (ADS)

Burrows, Adam; Sudarsky, David; Hubeny, Ivan

2004-06-01

We have derived physical diagnostics that can inform the direct detection and remote sensing programs of extrasolar giant planets (EGPs) now being planned or proposed. Stellar irradiation of the planet's atmosphere and the effects of water and ammonia clouds are incorporated in a consistent fashion. Whether an EGP is at wide or close-in separations from its parent star, direct detection will soon be possible and will yield centrally important physical and chemical constraints. Our theory of irradiated EGPs is being developed to meet this challenge.

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.

Planet Formation

NASA Astrophysics Data System (ADS)

Klahr, Hubert; Brandner, Wolfgang

2011-02-01

1. Historical notes on planet formation Bodenheimer; 2. The formation and evolution of planetary systems Bouwman et al.; 3. Destruction of protoplanetary disks by photoevaporation Richling, Hollenbach and Yorke; 4. Turbulence in protoplanetary accretion disks Klahr, Rozyczka, Dziourkevitch, Wunsch and Johansen; 5. The origin of solids in the early solar system Trieloff and Palme; 6. Experiments on planetesimal formation Wurm and Blum; 7. Dust coagulation in protoplanetary disks Henning, Dullemond, Wolf and Dominik; 8. The accretion of giant planet cores Thommes and Duncan; 9. Planetary transits: direct vision of extrasolar planets Lecavelier des Etangs and Vidal-Madjar; 10. The core accretion - gas capture model Hubickyj; 11. Properties of exoplanets Marcy, Fischer, Butler and Vogt; 12. Giant planet formation: theories meet observations Boss; 13. From hot Jupiters to hot Neptures … and below Lovis, Mayor and Udry; 14. Disk-planet interaction and migration Masset and Kley; 15. The Brown Dwarf - planet relation Bate; 16. From astronomy to astrobiology Brandner; 17. Overview and prospective Lin.

Oxygen in the stratospheres of the giant planets and Titan

NASA Astrophysics Data System (ADS)

Feuchtgruber, H.; Lellouch, E.; Encrenaz, Th.; Bezard, B.; Coustenis, A.; Drossart, P.; Salama, A.; de Graauw, Th.; Davis, G. R.

1999-03-01

Infrared spectra of the Short-Wavelength Spectrometer (SWS) of ISO at wavelengths between 25 - 45 μm have provided the first detection of stratospheric H2O on all four giant planets and Titan. Together with SWS observations of CO2 at 14.98 μm, leading to first detections on Neptune, Saturn and Jupiter an external source of oxygen is required to explain the derived upper stratospheric mixing ratios of up to several ppb at mbar-μbar levels. We provide an overview on the required amounts of external oxygen fluxes and a detailed discussion on the various scenarios for the origin of CO2 in the stratospheres of the giant planets.

On the possibility of enrichment and differentiation in gas giants during birth by disk instability

NASA Astrophysics Data System (ADS)

Boley, Aaron C.; Durisen, Richard H.

2011-11-01

We investigate the coupling between solids and gas during the formation of gas giant planets by disk fragmentation in the outer regions of massive disks. We find that fragments can become differentiated at birth. Even if an entire clump does not survive, differentiation could create solids cores that survive to accrete gaseous envelopes later.

Making an Iron Planet: The Case for Repeated Hit and Run Collisions

NASA Astrophysics Data System (ADS)

Asphaug, E. I.; Reufer, A.

2014-12-01

Earth, Venus, Mars and some of the largest asteroids have massive silicate mantles surrounding iron cores, and chondritic compositions. Against this backdrop are anomalies like the iron planet Mercury, and the Moon with almost no core, and metallic asteroids like Psyche. The Moon can be explained by giant impact, but for Mercury a giant impact (Benz et al., Icarus 1988) is problematic. Mercury must retain substantial volatiles after its obliteration (e.g. Peplowski et al., Science 2011), and must somehow avoid accreting its ejected silicates (Gladman and Coffey, MAPS 2009). SPH simulations have shown (Asphaug and Reufer, Nature Geosciences 2014; Sarid et al., LPSC 2014) that a differentiated chondritic proto-Mercury about 3 times its present mass can be stripped of its mantle in one energetic hit and run collision with a larger planet (proto-Venus or proto-Earth). To preserve Mercury's volatiles we also consider the scenario of lower energy hit and runs, in succession. We show that if 20 Mars-like planets accreted stochastically to form Venus and the Earth, then the statistics of attrition is likely to lead to one planet (Mercury) expressing repeated mantle stripping, and another planet (Mars) relatively undisturbed. For iron asteroids the "missing mantle paradox" likewise looms prominent. Where does it go, and how do we strip away so much mantle rock (in some cases down to a bare iron core; Yang et al., Nature 2007, Moskovitz et al., EPSL 2011) while leaving asteroids like Vesta presumably intact? According to the hit and run hypothesis, the sink for all this missing silicate is the larger accreted bodies at the top of the feeding chain, as they win the pairwise dynamical competition for stripped materials. This exotic origin of relics is only relevant to those few pairwise encounters that do not accrete both bodies. So the small survivors are lucky, and how they are lucky -- their attrition bias -- is manifested as compositional diversity and a preponderance of

RE-INFLATED WARM JUPITERS AROUND RED GIANTS

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

Lopez, Eric D.; Fortney, Jonathan J.

2016-02-10

Since the discovery of the first transiting hot Jupiters, models have sought to explain the anomalously large radii of highly irradiated gas giants. We now know that the size of hot Jupiter radius anomalies scales strongly with a planet's level of irradiation and numerous models like tidal heating, ohmic dissipation, and thermal tides have since been developed to help explain these inflated radii. In general, however, these models can be grouped into two broad categories: models that directly inflate planetary radii by depositing a fraction of the incident irradiation into the interior and models that simply slow a planet's radiativemore » cooling, allowing it to retain more heat from formation and thereby delay contraction. Here we present a new test to distinguish between these two classes of models. Gas giants orbiting at moderate orbital periods around post-main-sequence stars will experience enormous increases to their irradiation as their host stars move up the sub-giant and red-giant branches. If hot Jupiter inflation works by depositing irradiation into the planet's deep interiors then planetary radii should increase in response to the increased irradiation. This means that otherwise non-inflated gas giants at moderate orbital periods of >10 days can re-inflate as their host stars evolve. Here we explore the circumstances that can lead to the creation of these “re-inflated” gas giants and examine how the existence or absence of such planets can be used to place unique constraints on the physics of the hot Jupiter inflation mechanism. Finally, we explore the prospects for detecting this potentially important undiscovered population of planets.« less

The Formation of the Earth-Moon System and the Planets

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Young, Richard E. (Technical Monitor)

1998-01-01

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 are based upon observations of the Solar System and of young stars and their environments. They 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.

Shedding light on the eccentricity valley: Gap heating and eccentricity excitation of giant planets in protoplanetary disks

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

Tsang, David; Cumming, Andrew; Turner, Neal J., E-mail: dtsang@physics.mcgill.ca

2014-02-20

We show that the first order (non-co-orbital) corotation torques are significantly modified by entropy gradients in a non-barotropic protoplanetary disk. Such non-barotropic torques can dramatically alter the balance that, for barotropic cases, results in the net eccentricity damping for giant gap-clearing planets embedded in the disk. We demonstrate that stellar illumination can heat the gap enough for the planet's orbital eccentricity to instead be excited. We also discuss the 'Eccentricity Valley' noted in the known exoplanet population, where low-metallicity stars have a deficit of eccentric planets between ∼0.1 and ∼1 AU compared to metal-rich systems. We show that this featuremore » in the planet distribution may be due to the self-shadowing of the disk by a rim located at the dust sublimation radius ∼0.1 AU, which is known to exist for several T Tauri systems. In the shadowed region between ∼0.1 and ∼1 AU, lack of gap insolation allows disk interactions to damp eccentricity. Outside such shadowed regions stellar illumination can heat the planetary gaps and drive eccentricity growth for giant planets. We suggest that the self-shadowing does not arise at higher metallicity due to the increased optical depth of the gas interior to the dust sublimation radius.« less

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.

N-body simulations of planet formation: understanding exoplanet system architectures

NASA Astrophysics Data System (ADS)

Coleman, Gavin; Nelson, Richard

2015-12-01

Observations have demonstrated the existence of a significant population of compact systems comprised of super-Earths and Neptune-mass planets, and a population of gas giants that appear to occur primarily in either short-period (<10 days) or longer period (>100 days) orbits. The broad diversity of system architectures raises the question of whether or not the same formation processes operating in standard disc models can explain these planets, or if different scenarios are required instead to explain the widely differing architectures. To explore this issue, we present the results from a comprehensive suite of N-body simulations of planetary system formation that include the following physical processes: gravitational interactions and collisions between planetary embryos and planetesimals; type I and II migration; gas accretion onto planetary cores; self-consistent viscous disc evolution and disc removal through photo-evaporation. Our results indicate that the formation and survival of compact systems of super-Earths and Neptune-mass planets occur commonly in disc models where a simple prescription for the disc viscosity is assumed, but such models never lead to the formation and survival of gas giant planets due to migration into the star. Inspired in part by the ALMA observations of HL Tau, and by MHD simulations that display the formation of long-lived zonal flows, we have explored the consequences of assuming that the disc viscosity varies in both time and space. We find that the radial structuring of the disc leads to conditions in which systems of giant planets are able to form and survive. Furthermore, these giants generally occupy those regions of the mass-period diagram that are densely populated by the observed gas giants, suggesting that the planet traps generated by radial structuring of protoplanetary discs may be a necessary ingredient for forming giant planets.

The SOPHIE search for northern extrasolar planets. X. Detection and characterization of giant planets by the dozen

NASA Astrophysics Data System (ADS)

Hébrard, G.; Arnold, L.; Forveille, T.; Correia, A. C. M.; Laskar, J.; Bonfils, X.; Boisse, I.; Díaz, R. F.; Hagelberg, J.; Sahlmann, J.; Santos, N. C.; Astudillo-Defru, N.; Borgniet, S.; Bouchy, F.; Bourrier, V.; Courcol, B.; Delfosse, X.; Deleuil, M.; Demangeon, O.; Ehrenreich, D.; Gregorio, J.; Jovanovic, N.; Labrevoir, O.; Lagrange, A.-M.; Lovis, C.; Lozi, J.; Moutou, C.; Montagnier, G.; Pepe, F.; Rey, J.; Santerne, A.; Ségransan, D.; Udry, S.; Vanhuysse, M.; Vigan, A.; Wilson, P. A.

2016-04-01

We present new radial velocity measurements of eight stars that were secured with the spectrograph SOPHIE at the 193 cm telescope of the Haute-Provence Observatory. The measurements allow detecting and characterizing new giant extrasolar planets. The host stars are dwarfs of spectral types between F5 and K0 and magnitudes of between 6.7 and 9.6; the planets have minimum masses Mp sin I of between 0.4 to 3.8 MJup and orbitalperiods of several days to several months. The data allow only single planets to be discovered around the first six stars (HD 143105, HIP 109600, HD 35759, HIP 109384, HD 220842, and HD 12484), but one of them shows the signature of an additional substellar companion in the system. The seventh star, HIP 65407, allows the discovery of two giant planets that orbit just outside the 12:5 resonance in weak mutual interaction. The last star, HD 141399, was already known to host a four-planet system; our additional data and analyses allow new constraints to be set on it. We present Keplerian orbits of all systems, together with dynamical analyses of the two multi-planet systems. HD 143105 is one of the brightest stars known to host a hot Jupiter, which could allow numerous follow-up studies to be conducted even though this is not a transiting system. The giant planets HIP 109600b, HIP 109384b, and HD 141399c are located in the habitable zone of their host star. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium (programs 07A.PNP.CONS to 15A.PNP.CONS).Full version of the SOPHIE measurements (Table 1) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A145

Global hydromagnetic simulations of a planet embedded in a dead zone: Gap opening, gas accretion, and formation of a protoplanetary jet

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

Gressel, O.; Nelson, R. P.; Turner, N. J.

We present global hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations with mesh refinement of accreting planets embedded in protoplanetary disks (PPDs). The magnetized disk includes Ohmic resistivity that depends on the overlying mass column, leading to turbulent surface layers and a dead zone near the midplane. The main results are: (1) the accretion flow in the Hill sphere is intrinsically three-dimensional for HD and MHD models. Net inflow toward the planet is dominated by high-latitude flows. A circumplanetary disk (CPD) forms. Its midplane flows outward in a pattern whose details differ between models. (2) The opening of a gap magnetically couplesmore » and ignites the dead zone near the planet, leading to stochastic accretion, a quasi-turbulent flow in the Hill sphere, and a CPD whose structure displays high levels of variability. (3) Advection of magnetized gas onto the rotating CPD generates helical fields that launch magnetocentrifugally driven outflows. During one specific epoch, a highly collimated, one-sided jet is observed. (4) The CPD's surface density is ∼30 g cm{sup −2}, small enough for significant ionization and turbulence to develop. (5) The accretion rate onto the planet in the MHD simulation reaches a steady value 8 × 10{sup –3} M {sub ⊕} yr{sup –1} and is similar in the viscous HD runs. Our results suggest that gas accretion onto a forming giant planet within a magnetized PPD with a dead zone allows rapid growth from Saturnian to Jovian masses. As well as being relevant for giant planet formation, these results have important implications for the formation of regular satellites around gas giant planets.« less

The SEEDS of Planet Formation: Indirect Signatures of Giant Planets in Transitional Disks

NASA Technical Reports Server (NTRS)

Grady, Carol

2012-01-01

Circumstellar disks associated with PMS stars are the site where planetesimals form and grow, and ultimately where planets are produced. A key phase in the evolution of such disks is the phase where clearing of the disk has begun, potentially enabling direct detection of giant planets, but the disk retains sufficient material that indirect signatures that these are young planetary systems are also present. After reviewing what has been learned from studies of the IR spectral energy distribution and (sub )mm-interferometry, I will discuss recent results obtained as part of the Strategic Exploration of Exoplanets and Disks with Subaru (SEEDS).

Predicting the Atmospheric Composition of Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Sharp, A. G.; Moses, J. I.; Friedson, A. J.; Fegley, B., Jr.; Marley, M. S.; Lodders, K.

2004-01-01

To date, approximately 120 planet-sized objects have been discovered around other stars, mostly through the radial-velocity technique. This technique can provide information about a planet s minimum mass and its orbital period and distance; however, few other planetary data can be obtained at this point in time unless we are fortunate enough to find an extrasolar giant planet that transits its parent star (i.e., the orbit is edge-on as seen from Earth). In that situation, many physical properties of the planet and its parent star can be determined, including some compositional information. Our prospects of directly obtaining spectra from extrasolar planets may improve in the near future, through missions like NASA's Terrestrial Planet Finder. Most of the extrasolar giant planets (EGPs) discovered so far have masses equal to or greater than Jupiter's mass, and roughly 16% have orbital radii less than 0.1 AU - extremely close to the parent star by our own Solar-System standards (note that Mercury is located at a mean distance of 0.39 AU and Jupiter at 5.2 AU from the Sun). Although all EGPs are expected to have hydrogen-dominated atmospheres similar to Jupiter, the orbital distance can strongly affect the planet's temperature, physical, chemical, and spectral properties, and the abundance of minor, detectable atmospheric constituents. Thermochemical equilibrium models can provide good zero-order predictions for the atmospheric composition of EGPs. However, both the composition and spectral properties will depend in large part on disequilibrium processes like photochemistry, chemical kinetics, atmospheric transport, and haze formation. We have developed a photochemical kinetics, radiative transfer, and 1-D vertical transport model to study the atmospheric composition of EGPs. The chemical reaction list contains H-, C-, O-, and N-bearing species and is designed to be valid for atmospheric temperatures ranging from 100-3000 K and pressures up to 50 bar. Here we examine

The Pan-Pacific Planet Search. VII. The Most Eccentric Planet Orbiting a Giant Star

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Jones, M. I.; Horner, Jonathan; Kane, Stephen R.; Marshall, J. P.; Mustill, A. J.; Jenkins, J. S.; Pena Rojas, P. A.; Zhao, Jinglin; Villaver, Eva; Butler, R. P.; Clark, Jake

2017-12-01

Radial velocity observations from three instruments reveal the presence of a 4 M Jup planet candidate orbiting the K giant HD 76920. HD 76920b has an orbital eccentricity of 0.856 ± 0.009, making it the most eccentric planet known to orbit an evolved star. There is no indication that HD 76920 has an unseen binary companion, suggesting a scattering event rather than Kozai oscillations as a probable culprit for the observed eccentricity. The candidate planet currently approaches to about four stellar radii from its host star, and is predicted to be engulfed on a ∼100 Myr timescale due to the combined effects of stellar evolution and tidal interactions.

Superflares and Giant Planets

NASA Astrophysics Data System (ADS)

Rubenstein, Eric P.

2001-02-01

Nine solar analogues, stars similar in size and composition to the Sun, are known to have produced enormous flares. These outbursts, which were from 100 to 10 million times the size of even the largest solar flares, have puzzled astronomers, because sunlike stars should in theory vary little in brightness. A likely explanation is that these stars have unseen planetary companions circling in close orbits. Giant planets with large magnetic fields would, over time, entangle the magnetic fields of the parent stars. Eventually, the stretched and twisted magnetic-field lines would break and reattach themselves in a less complicated arrangement. This process, called magnetic reconnection, neatly explains how vast amounts of energy can be released so suddenly from superflaring solar analogues.

Gas Velocities Reveal Newly Born Planets in a Disk

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-06-01

, 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

The mass of planet GJ 676A b from ground-based astrometry. A planetary system with two mature gas giants suitable for direct imaging

NASA Astrophysics Data System (ADS)

Sahlmann, J.; Lazorenko, P. F.; Ségransan, D.; Astudillo-Defru, N.; Bonfils, X.; Delfosse, X.; Forveille, T.; Hagelberg, J.; Lo Curto, G.; Pepe, F.; Queloz, D.; Udry, S.; Zimmerman, N. T.

2016-11-01

The star GJ 676A is an M0 dwarf hosting both gas-giant and super-Earth-type planets that were discovered with radial-velocity measurements. Using FORS2/VLT, we obtained position measurements of the star in the plane of the sky that tightly constrain its astrometric reflex motion caused by the super-Jupiter planet "b" in a 1052-day orbit. This allows us to determine the mass of this planet to be , which is 40% higher than the minimum mass inferred from the radial-velocity orbit. Using new HARPS radial-velocity measurements, we improve upon the orbital parameters of the inner low-mass planets "d" and "e" and we determine the orbital period of the outer giant planet "c" to be Pc = 7340 days under the assumption of a circular orbit. The preliminary minimum mass of planet "c" is Mcsini = 6.8 MJ with an upper limit of 39 MJ that we set using NACO/VLT high-contrast imaging. We also determine precise parallaxes and relative proper motions for both GJ 676A and its wide M3 companion GJ 676B. Although the system is probably quite mature, the masses and projected separations ( 0.̋1-0.̋4) of planets "b" and "c" make them promising targets for direct imaging with future instruments in space and on extremely large telescopes. In particular, we estimate that GJ 676A b and GJ 676A c are promising targets for directly detecting their reflected light with the WFIRST space mission. Our study demonstrates the synergy of radial-velocity and astrometric surveys that is necessary to identify the best targets for such a mission. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 385.C-0416 (A,B), 086.C-0515(A), 089.C-0115(D,E), 072.C-0488(E), 180.C-0886(A), 183.C-0437(A), 085.C-0019(A), 091.C-0034(A), 095.C-0551(A), 096.C-0460(A).Full Table A.2 is only 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/595/A77

On the history and future of cosmic planet formation

NASA Astrophysics Data System (ADS)

Behroozi, Peter; Peeples, Molly S.

2015-12-01

We combine constraints on galaxy formation histories with planet formation models, yielding the Earth-like and giant planet formation histories of the Milky Way and the Universe as a whole. In the Hubble volume (1013 Mpc3), we expect there to be ˜1020 Earth-like and ˜1020 giant planets; our own galaxy is expected to host ˜109 and ˜1010 Earth-like and giant planets, respectively. Proposed metallicity thresholds for planet formation do not significantly affect these numbers. However, the metallicity dependence for giant planets results in later typical formation times and larger host galaxies than for Earth-like planets. The Solar system formed at the median age for existing giant planets in the Milky Way, and consistent with past estimates, formed after 80 per cent of Earth-like planets. However, if existing gas within virialized dark matter haloes continues to collapse and form stars and planets, the Universe will form over 10 times more planets than currently exist. We show that this would imply at least a 92 per cent chance that we are not the only civilization the Universe will ever have, independent of arguments involving the Drake equation.

On The History and Future of Cosmic Planet Formation

NASA Astrophysics Data System (ADS)

Behroozi, Peter

2016-03-01

We combine constraints on galaxy formation histories with planet formation models, yielding the Earth-like and giant planet formation histories of the Milky Way and the Universe as a whole. In the Hubble Volume (1013 Mpc3), we expect there to be ~1020 Earth-like and ~1020 giant planets; our own galaxy is expected to host ~109 and ~1010 Earth-like and giant planets, respectively. Proposed metallicity thresholds for planet formation do not significantly affect these numbers. However, the metallicity dependence for giant planets results in later typical formation times and larger host galaxies than for Earth-like planets. The Solar System formed at the median age for existing giant planets in the Milky Way, and consistent with past estimates, formed after 80% of Earth-like planets. However, if existing gas within virialised dark matter haloes continues to collapse and form stars and planets, the Universe will form over 10 times more planets than currently exist. We show that this would imply at least a 92% chance that we are not the only civilisation the Universe will ever have, independent of arguments involving the Drake Equation.

Artist's Concept of Hubble-Discovered Ancient Gas-Giant Planet

NASA Technical Reports Server (NTRS)

2003-01-01

NASA's Hubble Space Telescope (HST) precisely measured the mass of the oldest known planet in our Milky Way Galaxy bringing closure to a decade of speculation. Scientists weren't sure if the object was a planet or a brown dwarf. Hubble's analysis shows that the object is 2.5 times the mass of Jupiter, confirming that it is indeed a planet. At an estimated age of 13 billion years, the planet is more than twice the age of Earth's 4.5 billion years. It formed around a young, sun-like star barely 1 million years after our universe's birth in the Big Bang. The ancient planet resides in an unlikely, rough neighborhood. It orbits a peculiar pair of burned-out stars in the crowded core cluster of more than 100,000 stars. Its very existence provides evidence that the first planets formed rapidly, within a billion years of the Big Bang, and leads astronomers to conclude that planets may be very abundant in our galaxy. This artist's concept depicts the planet with a view of a rich star filled sky.

The Gemini Planet-finding Campaign: The Frequency Of Giant Planets around Debris Disk Stars

NASA Astrophysics Data System (ADS)

Wahhaj, Zahed; Liu, Michael C.; Nielsen, Eric L.; Biller, Beth A.; Hayward, Thomas L.; Close, Laird M.; Males, Jared R.; Skemer, Andrew; Ftaclas, Christ; Chun, Mark; Thatte, Niranjan; Tecza, Matthias; Shkolnik, Evgenya L.; Kuchner, Marc; Reid, I. Neill; de Gouveia Dal Pino, Elisabete M.; Alencar, Silvia H. P.; Gregorio-Hetem, Jane; Boss, Alan; Lin, Douglas N. C.; Toomey, Douglas W.

2013-08-01

We have completed a high-contrast direct imaging survey for giant planets around 57 debris disk stars as part of the Gemini NICI Planet-Finding Campaign. We achieved median H-band contrasts of 12.4 mag at 0.''5 and 14.1 mag at 1'' separation. Follow-up observations of the 66 candidates with projected separation <500 AU show that all of them are background objects. To establish statistical constraints on the underlying giant planet population based on our imaging data, we have developed a new Bayesian formalism that incorporates (1) non-detections, (2) single-epoch candidates, (3) astrometric and (4) photometric information, and (5) the possibility of multiple planets per star to constrain the planet population. Our formalism allows us to include in our analysis the previously known β Pictoris and the HR 8799 planets. Our results show at 95% confidence that <13% of debris disk stars have a >=5 M Jup planet beyond 80 AU, and <21% of debris disk stars have a >=3 M Jup planet outside of 40 AU, based on hot-start evolutionary models. We model the population of directly imaged planets as d 2 N/dMdavpropm α a β, where m is planet mass and a is orbital semi-major axis (with a maximum value of a max). We find that β < -0.8 and/or α > 1.7. Likewise, we find that β < -0.8 and/or a max < 200 AU. For the case where the planet frequency rises sharply with mass (α > 1.7), this occurs because all the planets detected to date have masses above 5 M Jup, but planets of lower mass could easily have been detected by our search. If we ignore the β Pic and HR 8799 planets (should they belong to a rare and distinct group), we find that <20% of debris disk stars have a >=3 M Jup planet beyond 10 AU, and β < -0.8 and/or α < -1.5. Likewise, β < -0.8 and/or a max < 125 AU. Our Bayesian constraints are not strong enough to reveal any dependence of the planet frequency on stellar host mass. Studies of transition disks have suggested that about 20% of stars are undergoing planet

Library of Giant Planet Reflection Spectra for WFirst and Future Space Telescopes

NASA Astrophysics Data System (ADS)

Smith, Adam J. R. W.; Fortney, Jonathan; Morley, Caroline; Batalha, Natasha E.; Lewis, Nikole K.

2018-01-01

Future large space space telescopes will be able to directly image exoplanets in optical light. The optical light of a resolved planet is due to stellar flux reflected by Rayleigh scattering or cloud scattering, with absorption features imprinted due to molecular bands in the planetary atmosphere. To aid in the design of such missions, and to better understand a wide range of giant planet atmospheres, we have built a library of model giant planet reflection spectra, for the purpose of determining effective methods of spectral analysis as well as for comparison with actual imaged objects. This library covers a wide range of parameters: objects are modeled at ten orbital distances between 0.5 AU and 5.0 AU, which ranges from planets too warm for water clouds, out to those that are true Jupiter analogs. These calculations include six metalicities between solar and 100x solar, with a variety of different cloud thickness parameters, and across all possible phase angles.

Magnetic fields in giant planet formation and protoplanetary discs

NASA Astrophysics Data System (ADS)

Keith, Sarah Louise

2015-12-01

Protoplanetary discs channel accretion onto their host star. How this is achieved is critical to the growth of giant planets which capture their massive gaseous atmosphere from the surrounding flow. Theoretical studies find that an embedded magnetic field could power accretion by hydromagnetic turbulence or torques from a large-scale field. This thesis presents a study of the inuence of magnetic fields in three key aspects of this process: circumplanetary disc accretion, gas flow across gaps in protoplanetary discs, and magnetic-braking in accretion discs. The first study examines the conditions needed for self-consistent accretion driven by magnetic fields or gravitational instability. Models of these discs typically rely on hydromagnetic turbulence as the source of effective viscosity. However, magnetically coupled,accreting regions may be so limited that the disc may not support sufficient inflow. An improved Shakura-Sunyaev ? disc is used to calculate the ionisation fraction and strength of non-ideal effects. Steady magnetically-driven accretion is limited to the thermally ionised, inner disc so that accretion in the remainder of the disc is time-dependent. The second study addresses magnetic flux transport in an accretion gap evacuated by a giant planet. Assuming the field is passively drawn along with the gas, the hydrodynamical simulation of Tanigawa, Ohtsuki & Machida (2012) is used for an a posteriori analysis of the gap field structure. This is used to post-calculate magnetohydrodynamical quantities. This assumption is self-consistent as magnetic forces are found to be weak, and good magnetic coupling ensures the field is frozen into the gas. Hall drift dominates across much of the gap, with the potential to facilitate turbulence and modify the toroidal field according to the global field orientation. The third study considers the structure and stability of magnetically-braked accretion discs. Strong evidence for MRI dead-zones has renewed interest in

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.

Planets around the evolved stars 24 Boötis and γ Libra: A 30 d-period planet and a double giant-planet system in possible 7:3 MMR

NASA Astrophysics Data System (ADS)

Takarada, Takuya; Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Nagasawa, Makiko; Izumiura, Hideyuki; Kambe, Eiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru

2018-05-01

We report the detection of planets around two evolved giant stars from radial velocity measurements at Okayama Astrophysical observatory. 24 Boo (G3 IV) has a mass of 0.99 M_{⊙}, a radius of 10.64 R_{⊙}, and a metallicity of [Fe/H] = -0.77. The star hosts one planet with a minimum mass of 0.91 MJup and an orbital period of 30.35 d. The planet has one of the shortest orbital periods among those ever found around evolved stars using radial-velocity methods. The stellar radial velocities show additional periodicity with 150 d, which can probably be attributed to stellar activity. The star is one of the lowest-metallicity stars orbited by planets currently known. γ Lib (K0 III) is also a metal-poor giant with a mass of 1.47 M_{⊙}, a radius of 11.1 R_{⊙}, and [Fe/H] = -0.30. The star hosts two planets with minimum masses of 1.02 MJup and 4.58 MJup, and periods of 415 d and 964 d, respectively. The star has the second-lowest metallicity among the giant stars hosting more than two planets. Dynamical stability analysis for the γ Lib system sets the minimum orbital inclination angle to be about 70° and suggests that the planets are in 7:3 mean-motion resonance, though the current best-fitting orbits for the radial-velocity data are not totally regular.

Revealing a universal planet-metallicity correlation for planets of different solar-type stars

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

Wang, Ji; Fischer, Debra A., E-mail: ji.wang@yale.edu

2015-01-01

The metallicity of exoplanet systems serves as a critical diagnostic of planet formation mechanisms. Previous studies have demonstrated the planet–metallicity correlation for large planets (R{sub P} ⩾ 4 R{sub E}); however, a correlation has not been found for smaller planets. With a sample of 406 Kepler objects of interest whose stellar properties are determined spectroscopically, we reveal a universal planet–metallicity correlation: not only gas-giant planets (3.9 R{sub E}

Giant elves: Lightning-generated electromagnetic pulses in giant planets.

NASA Astrophysics Data System (ADS)

Luque Estepa, Alejandro; Dubrovin, Daria; José Gordillo-Vázquez, Francisco; Ebert, Ute; Parra-Rojas, Francisco Carlos; Yair, Yoav; Price, Colin

2015-04-01

We currently have direct optical observations of atmospheric electricity in the two giant gaseous planets of our Solar System [1-5] as well as radio signatures that are possibly generated by lightning from the two icy planets Uranus and Neptune [6,7]. On Earth, the electrical activity of the troposphere is associated with secondary electrical phenomena called Transient Luminous Events (TLEs) that occur in the mesosphere and lower ionosphere. This led some researchers to ask if similar processes may also exist in other planets, focusing first on the quasi-static coupling mechanism [8], which on Earth is responsible for halos and sprites and then including also the induction field, which is negligible in our planet but dominant in Saturn [9]. However, one can show that, according to the best available estimation for lightning parameters, in giant planets such as Saturn and Jupiter the effect of the electromagnetic pulse (EMP) dominates the effect that a lightning discharge has on the lower ionosphere above it. Using a Finite-Differences, Time-Domain (FDTD) solver for the EMP we found [10] that electrically active storms may create a localized but long-lasting layer of enhanced ionization of up to 103 cm-3 free electrons below the ionosphere, thus extending the ionosphere downward. We also estimate that the electromagnetic pulse transports 107 J to 1010 J toward the ionosphere. There emissions of light of up to 108 J would create a transient luminous event analogous to a terrestrial elve. Although these emissions are about 10 times fainter than the emissions coming from the lightning itself, it may be possible to target them for detection by filtering the appropiate wavelengths. [1] Cook, A. F., II, T. C. Duxbury, and G. E. Hunt (1979), First results on Jovian lightning, Nature, 280, 794, doi:10.1038/280794a0. [2] Little, B., C. D. Anger, A. P. Ingersoll, A. R. Vasavada, D. A. Senske, H. H. Breneman, W. J. Borucki, and The Galileo SSI Team (1999), Galileo images of

Model Atmospheres and Spectra for Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Freedman, Richard S.; Beebe, Reta (Technical Monitor)

2000-01-01

In the past few years much new observational data has become available for brown dwarfs and extra solar planets. Not only are new objects being discovered but the availability of higher resolution spectra is improving. This allows a better comparison between the models and the available data, and places new constraints on the models which now have to be made more physically realistic in order to better interpret the observations. Under this grant, an array of new opacities were calculated and successfully applied to a variety of physical situations that were used as input to model available observations of brown dwarfs and extra solar giant planets.

Reduced gas accretion on super-Earths and ice giants

NASA Astrophysics Data System (ADS)

Lambrechts, M.; Lega, E.

2017-10-01

A large fraction of giant planets have gaseous envelopes that are limited to about 10% of their total mass budget. Such planets are present in the solar system (Uranus, Neptune) and are frequently observed in short periods around other stars (the so-called super-Earths). In contrast to these observations, theoretical calculations based on the evolution of hydrostatic envelopes argue that such low-mass envelopes cannot be maintained around cores exceeding five Earth masses. Instead, under nominal disk conditions, these planets would acquire massive envelopes through runaway gas accretion within the lifetime of the protoplanetary disk. In this work we show that planetary envelopes are not in hydrostatic balance, which slows down envelope growth. A series of 3D global, radiative hydrodynamical simulations reveal a steady-state gas flow, which enters through the poles and exits in the disk midplane. Gas is pushed through the outer envelope in about ten orbital timescales. In regions of the disk that are not significantly dust-depleted, envelope accretion onto cores of about five Earth masses can get stalled as the gas flow enters the deep interior. Accreted solids sublimate deep in the convective interior, but small opacity-providing grains are trapped in the flow and do not settle, which further prevents rapid envelope accretion. The transition to runaway gas accretion can however be reached when cores grow larger than typical super-Earths, beyond 15 Earth masses, and preferably when disk opacities are below κ = 1 cm2/g. These findings offer an explanation for the typical low-mass envelopes around the cores of super-Earths.

Dust ablation on the giant planets: Consequences for stratospheric photochemistry

NASA Astrophysics Data System (ADS)

Moses, Julianne I.; Poppe, Andrew R.

2017-11-01

Ablation of interplanetary dust supplies oxygen to the upper atmospheres of Jupiter, Saturn, Uranus, and Neptune. Using recent dynamical model predictions for the dust influx rates to the giant planets (Poppe et al., 2016), we calculate the ablation profiles and investigate the subsequent coupled oxygen-hydrocarbon neutral photochemistry in the stratospheres of these planets. We find that dust grains from the Edgeworth-Kuiper Belt, Jupiter-family comets, and Oort-cloud comets supply an effective oxygen influx rate of 1.0-0.7+2.2 ×107 O atoms cm-2 s-1 to Jupiter, 7.4-5.1+16 ×104 cm-2 s-1 to Saturn, 8.9-6.1+19 ×104 cm-2 s-1 to Uranus, and 7.5-5.1+16 ×105 cm-2 s-1 to Neptune. The fate of the ablated oxygen depends in part on the molecular/atomic form of the initially delivered products, and on the altitude at which it was deposited. The dominant stratospheric products are CO, H2O, and CO2, which are relatively stable photochemically. Model-data comparisons suggest that interplanetary dust grains deliver an important component of the external oxygen to Jupiter and Uranus but fall far short of the amount needed to explain the CO abundance currently seen in the middle stratospheres of Saturn and Neptune. Our results are consistent with the theory that all of the giant planets have experienced large cometary impacts within the last few hundred years. Our results also suggest that the low background H2O abundance in Jupiter's stratosphere is indicative of effective conversion of meteoric oxygen to CO during or immediately after the ablation process - photochemistry alone cannot efficiently convert the H2O into CO on the giant planets.

All in the Family: What Brown Dwarfs Teach Us About Extrasolar Giant Planets

NASA Technical Reports Server (NTRS)

Marley, M.

2003-01-01

As we await the first direct image of an extrasolar giant planet, we can turn to theory and the experience gained in the campaign to detect and understand brown dwarfs for guidance on what to expect. As with any new arrival to a family, there should be a strong family resemblance (one hopes) along with notable unique features and interesting peculiarities. The 300 or so known L and T dwarfs, combined with our own giant planets, already span much of the effective temperature range within which extrasolar planets will be found. Only objects with thick, easily detectable, water clouds have yet to be seen. Thus we already know much of the family. I will describe what we have learned from studying these objects, focusing on the important roles clouds and atmospheric chemistry play in affecting their atmospheres and emergent spectra. Relying on these findings and theoretical models, I'll sketch out what we can expect from extrasolar giant planets, focusing on easily detectable features. Some wild cards, of course, are to be expected. Photochemical hazes, in particular, may obscure the family traits on the faces of Jupiter's distant cousins and may make one wonder, at least momentarily, about the milkman.

Giant planet migration during FU Orionis outbursts: 1D disc models

NASA Astrophysics Data System (ADS)

Dunhill, A. C.

2018-05-01

I present the results of semi-analytic calculations of migrating planets in young, outbursting circumstellar discs. Formed far out in the disc via gravitational fragmentation early on in its lifetime, these planets typically migrate at very slow rates and are therefore mostly expected to remain at large radii (such as is the case in HR 8799). I show that changes in the disc structure during FUor outbursts affect the planet's ability to maintain a gap and can allow a massive giant planet's semimajor axis to reduce by almost 5 per cent in a single outburst under the most optimistic conditions. Given that a single disc will likely undergo ˜10 such outbursts this process can significantly alter the expected radial distribution for GI-formed planets.

Oxygen isotopes and the moon-forming giant impact.

PubMed

Wiechert, U; Halliday, A N; Lee, D C; Snyder, G A; Taylor, L A; Rumble, D

2001-10-12

We have determined the abundances of 16O, 17O, and 18O in 31 lunar samples from Apollo missions 11, 12, 15, 16, and 17 using a high-precision laser fluorination technique. All oxygen isotope compositions plot within +/-0.016 per mil (2 standard deviations) on a single mass-dependent fractionation line that is identical to the terrestrial fractionation line within uncertainties. This observation is consistent with the Giant Impact model, provided that the proto-Earth and the smaller impactor planet (named Theia) formed from an identical mix of components. The similarity between the proto-Earth and Theia is consistent with formation at about the same heliocentric distance. The three oxygen isotopes (delta17O) provide no evidence that isotopic heterogeneity on the Moon was created by lunar impacts.

Planet population synthesis driven by pebble accretion in cluster environments

NASA Astrophysics Data System (ADS)

Ndugu, N.; Bitsch, B.; Jurua, E.

2018-02-01

The evolution of protoplanetary discs embedded in stellar clusters depends on the age and the stellar density in which they are embedded. Stellar clusters of young age and high stellar surface density destroy protoplanetary discs by external photoevaporation and stellar encounters. Here, we consider the effect of background heating from newly formed stellar clusters on the structure of protoplanetary discs and how it affects the formation of planets in these discs. Our planet formation model is built on the core accretion scenario, where we take the reduction of the core growth time-scale due to pebble accretion into account. We synthesize planet populations that we compare to observations obtained by radial velocity measurements. The giant planets in our simulations migrate over large distances due to the fast type-II migration regime induced by a high disc viscosity (α = 5.4 × 10-3). Cold Jupiters (rp > 1 au) originate preferably from the outer disc, due to the large-scale planetary migration, while hot Jupiters (rp < 0.1 au) preferably form in the inner disc. We find that the formation of gas giants via pebble accretion is in agreement with the metallicity correlation, meaning that more gas giants are formed at larger metallicity. However, our synthetic population of isolated stars host a significant amount of giant planets even at low metallicity, in contradiction to observations where giant planets are preferably found around high metallicity stars, indicating that pebble accretion is very efficient in the standard pebble accretion framework. On the other hand, discs around stars embedded in cluster environments hardly form any giant planets at low metallicity in agreement with observations, where these changes originate from the increased temperature in the outer parts of the disc, which prolongs the core accretion time-scale of the planet. We therefore conclude that the outer disc structure and the planet's formation location determines the giant planet

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

Polarimetry of gas planets

NASA Astrophysics Data System (ADS)

Joos, Franco

The quest for new worlds was not only an adventure at the times of Columbus. Also nowadays mankind searches for new, undiscovered territories. But today they lie no longer only on our Earth, but also well outside the solar system. There, new planets are sought and found. One of the challenges of modern astrophysics is the direct detection of extra- solar planets. To reach this goal, the largest available telescopes and most sophisticated detection techniques are required. A promising method to "see" and analyse extra-solar planets is based on the fact, that light reflected by a planet can be polarised. For its detection, accurate polarisation measurements are needed. This is one of the methods ESO intends to make use of to find new planets outside the solar system. The Institute of Astronomy of ETH Zürich contributes ZIMPOL to this planet-finder project. ZIMPOL is a very sensitive imaging polarimeter. This thesis is situated within the ESO-planet-finder project. It deals with two problems that are crucial for a successful mission: (1) Instrumental polarisation can seriously hamper the performance of the instrument. It is therefore essential, to keep instrumental polarisation very low. (2) A knowledge of the polarisation properties of our targets would be very helpful. For this reason the polarisation properties of our solar system planets are investigated. Promising candidates for a detection with ZIMPOL are large planets with atmospheres similar to those of our giant gas planets Jupiter, Saturn, Uranus and Neptune. In the first part of the thesis the planet-finder project is presented and the role of ZIMPOL is explained. To obtain the instrumental polarisation, the polarimetric properties of mirrors and other optical components of our planet- finder instrument are analysed. The instrumental polarisation for the wavelength range of 600 to 1000 nm and for all zenith distances is calculated with Mueller matrices. Methods for reducing the instrumental polarisation

Europa, tidally heated oceans, and habitable zones around giant planets

NASA Astrophysics Data System (ADS)

Reynolds, R. T.; McKay, C. P.; Kasting, J. F.

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. Europa could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such a case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of eons and in which life could perhaps evolve. A zone around a giant planet is defined in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In this solar system, this radiatively-heated habitable zone contains the earth.

Europa, tidally heated oceans, and habitable zones around giant planets

NASA Technical Reports Server (NTRS)

Reynolds, Ray T.; Mckay, Christopher P.; Kasting, James F.

1987-01-01

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. Europa could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such a case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of eons and in which life could perhaps evolve. A zone around a giant planet is defined in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In this solar system, this radiatively-heated habitable zone contains the earth.

Europa, tidally heated oceans, and habitable zones around giant planets.

PubMed

Reynolds, R T; McKay, C P; Kasting, J F

1987-01-01

Tidal dissipation in the satellites of a giant planet may provide sufficient heating to maintain an environment favorable to life on the satellite surface or just below a thin ice layer. In our own solar system, Europa, one of the Galilean satellites of Jupiter, could have a liquid ocean which may occasionally receive sunlight through cracks in the overlying ice shell. In such case, sufficient solar energy could reach liquid water that organisms similar to those found under Antarctic ice could grow. In other solar systems, larger satellites with more significant heat flow could represent environments that are stable over an order of Aeons and in which life could perhaps evolve. We define a zone around a giant planet in which such satellites could exist as a tidally-heated habitable zone. This zone can be compared to the habitable zone which results from heating due to the radiation of a central star. In our solar system, this radiatively-heated habitable zone contains the Earth.

Coupled Evolution with Tides of the Radius and Orbit of Transiting Giant Planets

NASA Astrophysics Data System (ADS)

Ibgui, Laurent; Burrows, A.

2009-12-01

Some transiting extrasolar giant planets have measured radii larger than predicted by the standard theory. We explore the possibility that an earlier episode of tidal heating can explain such radius anomalies and apply the formalism we develop to HD 209458b as an example. We find that for strong enough tides the planet's radius can undergo a transient phase of inflation that temporarily interrupts canonical, monotonic shrinking due to radiative losses. Importantly, an earlier episode of tidal heating can result in a planet with an inflated radius, even though its orbit has nearly circularized. Moreover, we confirm that at late times, and under some circumstances, by raising tides on the star itself a planet can spiral into its host. We note that a 3 to 10 solar planet atmospheric opacity with no tidal heating is sufficient to explain the observed radius of HD 209458b. However, our model demonstrates that with an earlier phase of episodic tidal heating we can fit the observed radius of HD 209458b even with lower (solar) atmospheric opacities. This work demonstrates that, if a planet is left with an appreciable eccentricity after early inward migration and/or dynamical interaction, coupling radius and orbit evolution in a consistent fashion that includes tidal heating, stellar irradiation, and detailed model atmospheres might offer a generic solution to the inflated radius puzzle for transiting extrasolar giant planets.

Silica Debris Disk Evidence for Giant Planet Forming Impacts

NASA Astrophysics Data System (ADS)

Lisse, C.

2014-04-01

Giant impacts are major formation events in the history of our solar system. The final assembly of the planets, as we understand it, had to include massive fast collision events as the planets grew to objects with large escape velocities or in regions of high Keplerian velocities (Chambers 2004; Kenyon & Bromley 2004a,b, 2006; Fegley & Schaefer 2005). These massive impact events should create large amounts of glassy silica material derived from the rapid melting, vaporization, and refreezing of normal silicate rich primitive rocky material. We report here the detection of 4 bright silica-rich debris disks in the Spitzer IRS spectral archive, and the possible identification of 7 others. The stellar types of the system primaries span from A5V to G0V, their ages are 10 - 100 Myr, and the dust is warm, 280 - 480 K, and is located between 1.5 and 6 AU, well inside the systems' terrestrial planet regions. The minimum amount of detected 0.1 - 20 dust mass ranges from 10^21 - 10^23 kg; assuming < 10% dust formation efficiency (Benz 2009, 2011) this implies collisions involving impactors massing at least 10^22 - 10^24 kg, i.e. from Moon to Earth mass. We find possible trends in the mineralogy of the silica, with predominantly amorphous silica found in the 2 younger systems, and crystalline silica in the older systems. We speculate this is due higher velocity impacts found in younger, hotter systems, coupled with the effects of energetic photon annealing of small amorphous silica grains. All of these measures are consistent with the creation of silica rich rubble, or construction debris, during the terrestrial planet formation era of giant impacts.

WFIRST: Retrieval Studies of Directly Imaged Extrasolar Giant Planets

NASA Astrophysics Data System (ADS)

Marley, Mark; Lupu, Roxana; Lewis, Nikole K.; WFIRST Coronagraph SITs

2018-01-01

The typical direct imaging and spectroscopy target for the WFIRST Coronagraph will be a mature Jupiter-mass giant planet at a few AU from an FGK star. The spectra of such planets is expected to be shaped primarily by scattering from H2O clouds and absorption by gaseous NH3 and CH4. We have computed forward model spectra of such typical planets and applied noise models to understand the quality of photometry and spectra we can expect. Using such simulated datasets we have conducted Markov Chain Monte Carlo and MultiNest retrievals to derive atmospheric abundance of CH4, cloud scattering properties, gravity, and other parameters for various planets and observing modes. Our focus has primarily been to understand which combinations of photometry and spectroscopy at what SNR allow retrievals of atmospheric methane mixing ratios to within a factor of ten of the true value. This is a challenging task for directly imaged planets as the planet mass and radius--and thus surface gravity--are not as well constrained as in the case of transiting planets. We find that for plausible planets and datasets of the quality expected to be obtained by WFIRST it should be possible to place such constraints, at least for some planets. We present some examples of our retrieval results and explain how they have been utilized to help set design requirements on the coronagraph camera and integrated field spectrometer.

The Leonard Award Address: On the Difficulties of Making Earth-Like Planets

NASA Astrophysics Data System (ADS)

Taylor, Stuart Ross

1999-05-01

Here I discuss the series of events that led to the formation and evolution of our planet to examine why the Earth is unique in the solar system. A multitude of factors are involved. These begin with the initial size and angular momentum of the fragment that separated from a molecular cloud. These are crucial in determining whether a planetary system or a double star develops from the resulting nebula. Another requirement is that there must be an adequate concentration of heavy elements to provide the two percent 'rock' and 'ice' components of the original nebula. An essential step in forming rocky planets in the inner nebula is loss of gas and depletion of volatile elements due to early solar activity, that is linked to the mass of the central star. The lifetime of the gaseous nebula controls the formation of gas giants. In our system, fine timing was needed to form the gas giant, Jupiter before the gas in the nebula was depleted. Although Uranus and Neptune eventually formed cores large enough to capture gas, they missed out and ended as ice giants The early formation of Jupiter is responsible for the existence of the asteroid belt (and our supply of meteorites) and the small size of Mars while the gas giant now acts as a gravitational shield for the terrestrial planets. The Earth and the other inner planets accreted long after the giant planets in a gas-free inner nebula from volatile-depleted planetesimals that were probably already differentiated into metallic cores and silicate mantles. The accumulation of the Earth from such planetesimals was essentially a stochastic process, accounting for the differences among the four rocky inner planets including the startling contrast between those two apparent twins, Earth and Venus. Impact history and accretion of a few more or less planetesimals were apparently crucial. The origin of the Moon by a single massive impact with a body larger than Mars accounts for the obliquity (and its stability) and spin of the Earth

Type II Migration and Giant Planet Survival

NASA Technical Reports Server (NTRS)

Ward, William R.

2003-01-01

Type II migration, in which a newly formed large planet opens a gap in its precursor circumstellar nebula and subsequently evolves with it, has been implicated as a delivery mechanism responsible for close stellar companions. Large scale migration is possible in a viscously spreading disk of surface density sigma (r,t) when most of it is sacrificed to the primary in order to promote a small portion of the disk to much higher angular momentum orbits. Embedded planets generally follow its evolution unless their own angular momentum is comparable to that of the disk. The fraction of the starting disk mass, M (sub d) = 2pi integral rsigma(r,0)dr, that is consumed by the star depends on the distance at which material escapes the disk's outer boundary. If the disk is allowed to expand indefinitely, virtually all of the disk will fall into the primary in order to send a vanishingly small portion to infinity. For such a case, it is difficult to explain the survival of any giant planets, including Jupiter and Saturn. Realistically, however, there are processes that could truncate a disk at a finite distance, r(sub d). Recent numerical modeling has illustrated that planets can survive in this case. We show here that much of these results can be understood by simple conservation arguments.

Testing giant planet formation in the transitional disk of SAO 206462 using deep VLT/SPHERE imaging

NASA Astrophysics Data System (ADS)

Maire, A.-L.; Stolker, T.; Messina, S.; Müller, A.; Biller, B. A.; Currie, T.; Dominik, C.; Grady, C. A.; Boccaletti, A.; Bonnefoy, M.; Chauvin, G.; Galicher, R.; Millward, M.; Pohl, A.; Brandner, W.; Henning, T.; Lagrange, A.-M.; Langlois, M.; Meyer, M. R.; Quanz, S. P.; Vigan, A.; Zurlo, A.; van Boekel, R.; Buenzli, E.; Buey, T.; Desidera, S.; Feldt, M.; Fusco, T.; Ginski, C.; Giro, E.; Gratton, R.; Hubin, N.; Lannier, J.; Le Mignant, D.; Mesa, D.; Peretti, S.; Perrot, C.; Ramos, J. R.; Salter, G.; Samland, M.; Sissa, E.; Stadler, E.; Thalmann, C.; Udry, S.; Weber, L.

2017-05-01

Context. The SAO 206462 (HD 135344B) disk is one of the few known transitional disks showing asymmetric features in scattered light and thermal emission. Near-infrared scattered-light images revealed two bright outer spiral arms and an inner cavity depleted in dust. Giant protoplanets have been proposed to account for the disk morphology. Aims: We aim to search for giant planets responsible for the disk features and, in the case of non-detection, to constrain recent planet predictions using the data detection limits. Methods: We obtained new high-contrast and high-resolution total intensity images of the target spanning the Y to the K bands (0.95-2.3 μm) using the VLT/SPHERE near-infrared camera and integral field spectrometer. Results: The spiral arms and the outer cavity edge are revealed at high resolutions and sensitivities without the need for aggressive image post-processing techniques, which introduce photometric biases. We do not detect any close-in companions. For the derivation of the detection limits on putative giant planets embedded in the disk, we show that the knowledge of the disk aspect ratio and viscosity is critical for the estimation of the attenuation of a planet signal by the protoplanetary dust because of the gaps that these putative planets may open. Given assumptions on these parameters, the mass limits can vary from 2-5 to 4-7 Jupiter masses at separations beyond the disk spiral arms. The SPHERE detection limits are more stringent than those derived from archival NaCo/L' data and provide new constraints on a few recent predictions of massive planets (4-15 MJ) based on the spiral density wave theory. The SPHERE and ALMA data do not favor the hypotheses on massive giant planets in the outer disk (beyond 0.6''). There could still be low-mass planets in the outer disk and/or planets inside the cavity. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 095.C

THE PROPERTIES OF HEAVY ELEMENTS IN GIANT PLANET ENVELOPES

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

Soubiran, François; Militzer, Burkhard

The core-accretion model for giant planet formation suggests a two-layer picture for the initial structure of Jovian planets, with heavy elements in a dense core and a thick H–He envelope. Late planetesimal accretion and core erosion could potentially enrich the H–He envelope in heavy elements, which is supported by the threefold solar metallicity that was measured in Jupiter’s atmosphere by the Galileo entry probe. In order to reproduce the observed gravitational moments of Jupiter and Saturn, models for their interiors include heavy elements, Z , in various proportions. However, their effect on the equation of state of the hydrogen–helium mixturesmore » has not been investigated beyond the ideal mixing approximation. In this article, we report results from ab initio simulations of fully interacting H–He– Z mixtures in order to characterize their equation of state and to analyze possible consequences for the interior structure and evolution of giant planets. Considering C, N, O, Si, Fe, MgO, and SiO{sub 2}, we show that the behavior of heavy elements in H–He mixtures may still be represented by an ideal mixture if the effective volumes and internal energies are chosen appropriately. In the case of oxygen, we also compute the effect on the entropy. We find the resulting changes in the temperature–pressure profile to be small. A homogeneous distribution of 2% oxygen by mass changes the temperature in Jupiter’s interior by only 80 K.« less

Analytical Solutions for Radiative Transfer: Implications for Giant Planet Formation by Disk Instability

NASA Astrophysics Data System (ADS)

Boss, Alan P.

2009-03-01

The disk instability mechanism for giant planet formation is based on the formation of clumps in a marginally gravitationally unstable protoplanetary disk, which must lose thermal energy through a combination of convection and radiative cooling if they are to survive and contract to become giant protoplanets. While there is good observational support for forming at least some giant planets by disk instability, the mechanism has become theoretically contentious, with different three-dimensional radiative hydrodynamics codes often yielding different results. Rigorous code testing is required to make further progress. Here we present two new analytical solutions for radiative transfer in spherical coordinates, suitable for testing the code employed in all of the Boss disk instability calculations. The testing shows that the Boss code radiative transfer routines do an excellent job of relaxing to and maintaining the analytical results for the radial temperature and radiative flux profiles for a spherical cloud with high or moderate optical depths, including the transition from optically thick to optically thin regions. These radial test results are independent of whether the Eddington approximation, diffusion approximation, or flux-limited diffusion approximation routines are employed. The Boss code does an equally excellent job of relaxing to and maintaining the analytical results for the vertical (θ) temperature and radiative flux profiles for a disk with a height proportional to the radial distance. These tests strongly support the disk instability mechanism for forming giant planets.

Nebula-based Primordial Atmospheres of Planets Around Solar-Like Stars Revised

NASA Astrophysics Data System (ADS)

Scherf, Manuel; Lammer, H.; Leitzinger, M.; Odert, P.; Güdel, M.; Hanslmeier, A.

2012-05-01

At the beginning of a planetary system, in the stage of the stellar nebula and the growing-phase of the planets, planetesimals and Earth-like proto-planets accumulate a remarkable amount of gas, mainly consisting of hydrogen and helium. The mass of such a primordial atmosphere was first estimated for the proto-Earth by Hayashi et al. (1979), with up to 1026 g accumulated within 106 years. Furthermore it is commonly expected that these primordial atmospheres will be completely dissipated due to irradiation of the stellar EUV-flux during the first 108 years. Recent observations of young solar-like stars indicate that the efficiency and effect of the EUV-flux after the nebula disappeared, was highly overestimated by previous studies. We show that parts of these dense hydrogen/helium-gas envelopes may sustain this early active stage of a young star. Implications on the habitability are also discussed.

First-Principles Computer Simulations of Dense Plasmas and Application to the Interiors of Giant Planets

NASA Astrophysics Data System (ADS)

Militzer, Burkhard

2013-06-01

This presentation will review three recent applications of first-principles computer simulation techniques to study matter at extreme temperature-pressure conditions that are of relevance to astrophysics. First we report a recent methodological advance in all-electron path integral Monte Carlo (PIMC) that allowed us to extend this method beyond hydrogen and helium to elements with core electrons [1]. We combine results from PIMC and with density functional molecular dynamics (DFT-MD) simulations and derive a coherent equation of state (EOS) for water and carbon plasmas in the regime from 1-50 Mbar and 104-109 K that can be compared to laboratory shock wave experiments. Second we apply DFT-MD simulations to characterize superionic water in the interiors of Uranus and Neptune. By adopting a thermodynamic integration technique, we derive the Gibbs free energy in order to demonstrate the existence of a phase transformation from body-centered cubic to face-centered cubic superionic water [2]. Finally we again use DFT-MD to study the interiors of gas giant planets. We determine the EOS for hydrogen-helium mixtures spanning density-temperature conditions in the deep interiors of giant planets, 0.2-9.0 g/cc and 1000-80000 K [3]. We compare the simulation results with the semi-analytical EOS model by Saumon and Chabrier. We present a revision to the mass-radius relationship which makes the hottest exoplanets increase in radius by ~0.2 Jupiter radii at fixed entropy and for masses greater than 0.5 Jupiter masses. This change is large enough to have possible implications for some discrepant inflated giant exoplanets. We conclude by demonstrating that all materials in the cores of giant planets, ices, MgO, SiO2, and iron, will all dissolve into metallic hydrogen. This implies the cores of Jupiter and Saturn have been at least partially eroded. [1] K. P. Driver, B. Militzer, Phys. Rev. Lett. 108 (2012) 115502. [2] H. F. Wilson, M. L. Wong, B. Militzer, http://arxiv.org/abs/1211

Planetary Formation: From The Earth And Moon To Extrasolar Planets

NASA Technical Reports Server (NTRS)

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

1999-01-01

An overview of current theories of planetary growth, emphasizing the formation of habitable planets, is presented. These models are based upon observations of the Solar System and of young stars and their environments. They 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. 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 planets begin their growth like terrestrial planets, but if they become massive enough before the protoplanetary disk dissipates, then they are able to accumulate substantial amounts of gas. Specific issues to be discussed include: (1) how do giant planets influence the formation and habitability of terrestrial planets? (2) could a giant impact leading to lunar formation have occurred - 100 million years after the condensation of the oldest meteorites?

The Anglo-Australian Planet Search. XXII. Two New Multi-planet Systems

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Horner, J.; Tuomi, Mikko; Salter, G. S.; Tinney, C. G.; Butler, R. P.; Jones, H. R. A.; O'Toole, S. J.; Bailey, J.; Carter, B. D.; Jenkins, J. S.; Zhang, Z.; Vogt, S. S.; Rivera, Eugenio J.

2012-07-01

We report the detection of two new planets from the Anglo-Australian Planet Search. These planets orbit two stars each previously known to host one planet. The new planet orbiting HD 142 has a period of 6005 ± 427 days, and a minimum mass of 5.3 M Jup. HD 142c is thus a new Jupiter analog: a gas-giant planet with a long period and low eccentricity (e = 0.21 ± 0.07). The second planet in the HD 159868 system has a period of 352.3 ± 1.3 days and m sin i = 0.73 ± 0.05 M Jup. In both of these systems, including the additional planets in the fitting process significantly reduced the eccentricity of the original planet. These systems are thus examples of how multiple-planet systems can masquerade as moderately eccentric single-planet systems.

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.

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.

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

Electrodynamics on extrasolar giant planets

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

Koskinen, T. T.; Yelle, R. V.; Lavvas, P.

2014-11-20

Strong ionization on close-in extrasolar giant planets (EGPs) suggests that their atmospheres may be affected by ion drag and resistive heating arising from wind-driven electrodynamics. Recent models of ion drag on these planets, however, are based on thermal ionization only and do not include the upper atmosphere above the 1 mbar level. These models are also based on simplified equations of resistive magnetohydrodynamics that are not always valid in extrasolar planet atmospheres. We show that photoionization dominates over thermal ionization over much of the dayside atmosphere above the 100 mbar level, creating an upper ionosphere dominated by ionization of Hmore » and He and a lower ionosphere dominated by ionization of metals such as Na, K, and Mg. The resulting dayside electron densities on close-in exoplanets are higher than those encountered in any planetary ionosphere of the solar system, and the conductivities are comparable to the chromosphere of the Sun. Based on these results and assumed magnetic fields, we constrain the conductivity regimes on close-in EGPs and use a generalized Ohm's law to study the basic effects of electrodynamics in their atmospheres. We find that ion drag is important above the 10 mbar level where it can also significantly alter the energy balance through resistive heating. Due to frequent collisions of the electrons and ions with the neutral atmosphere, however, ion drag is largely negligible in the lower atmosphere below the 10 mbar level for a reasonable range of planetary magnetic moments. We find that the atmospheric conductivity decreases by several orders of magnitude in the night side of tidally locked planets, leading to a potentially interesting large-scale dichotomy in electrodynamics between the day and night sides. A combined approach that relies on UV observations of the upper atmosphere, phase curve and Doppler measurements of global dynamics, and visual transit observations to probe the alkali metals can

Exploring our outer solar system - The Giant Planet System Observers

NASA Astrophysics Data System (ADS)

Cooper, J. F.; Sittler, E. C., Jr.; Sturner, S. J.; Pitman, J. T.

As space-faring peoples now work together to plan and implement future missions that robotically prepare for landing humans to explore the Moon, and later Mars, the time is right to develop evolutionary approaches for extending this next generation of exploration beyond Earth's terrestrial planet neighbors to the realm of the giant planets. And while initial fly-by missions have been hugely successful in providing exploratory surveys of what lies beyond Mars, we need to consider now what robotic precursor mission capabilities we need to emplace that prepare us properly, and comprehensively, for long-term robotic exploration, and eventual human habitation, beyond Mars to the outer reaches of our solar system. To develop practical strategies that can establish prioritized capabilities, and then develop a means for achieving those capabilities within realistic budget and technology considerations, and in reasonable timeframes, is our challenge. We suggest one component of such an approach to future outer planets exploration is a series of Giant Planets System Observer (GPSO) missions that provide for long- duration observations, monitoring, and relay functions to help advance our understanding of the outer planets and thereby enable a sound basis for planning their eventual exploration by humans. We envision these missions as being comparable to taking Hubble-class remote-sensing facilities, along with the space physics capabilities of long-lived geospace and heliospheric missions, to the giant planet systems and dedicating long observing lifetimes (HST, 16 yr.; Voyagers, 29 yr.) to the exhaustive study and characterization of those systems. GPSO missions could feature 20-yr+ extended mission lifetimes, direct inject trajectories to maximize useful lifetime on target, placement strategies that take advantage of natural environment shielding (e.g., Ganymede magnetic field) where possible, orbit designs having favorable planetary system viewing geometries, comprehensive

A NICMOS direct imaging search for giant planets around the seven single white dwarfs in the Hyades

NASA Astrophysics Data System (ADS)

Zinnecker, Hans

2003-07-01

We propose to use the NIC1 camera on HST to search for massive giant planets around the known seven single white dwarfs in the nearby Hyades cluster at sub-arcsec separations. At an age of 625 Myr, the white dwarfs had protogenitor masses of about 3 solar masses, and massive gaseous giant planets should have formed in the massive circumstellar disks around these ex Herbig A0 stars, probably at orbital separations similar or slightly larger than that of Jupiter {5 AU} in our own solar system. Such planets would have survived the post-Main Sequence mass loss of the parent star, and would have migrated outward adiabatically by a factor 4.5, equal to the ratio of initial to final stellar mass {3Mo/0.66Mo}, due to conservation of orbital angular momentum during the mass loss {AGB and PN} phase. Thus the orbital separation NOW would be 4.5 x 5 AU = 22.5 AU, which at the distance of the Hyades {45 pc} corresponds to 0.50 arcsec. Simulations with TinyTim then show that giant planets at this separation with masses in the range 6-12 Jupiter masses and apparent J and H magnitudes in the range 20.5-23.3 mag {from Baraffe or Burrows models} can be spatially resolved around the Hyades white dwarfs. Their J and H brightnesses are known to be 15 +/- 0.5 mag, implying a median star-planet brightness ratio of 1000:1 {7.5 mag}. This combination of dynamic range and orbital separation is observable with NICMOS, by subtracting images taken at two roll angles. Therefore, the proposed near-IR diffraction-limited observations in the F110W and F160W filters promise to resolve giant planets around low-mass stars for the first time. If successful, the observations would also prove that giant planets do form around early-type stars more massive than the Sun.

A possible giant planet orbiting the cataclysmic variable LX Ser

NASA Astrophysics Data System (ADS)

Li, Kai; Hu, Shaoming; Zhou, Jilin; Wu, Donghong; Guo, Difu; Jiang, Yunguo; Gao, Dongyang; Chen, Xu; Wang, Xianyu

2017-04-01

LX Ser is a deeply eclipsing cataclysmic variable with an orbital period of 0.1584325 d. 62 new eclipse times were determined by our observations and the AAVSO International Data base. Combining all available eclipse times, we analyzed the O - C behavior of LX Ser. We found that the O - C diagram of LX Ser shows a sinusoidal oscillation with a period of 22.8 yr and an amplitude of 0.00035 d. Two mechanisms (i.e., the Applegate mechanism and the light-travel time effect) are applied to explain the cyclic modulation. We found that it is difficult to apply the Applegate mechanism to explain the cyclic oscillation in the orbital period. Therefore, the cyclic period change is most likely to be caused by the light-travel time effect due to the presence of a third body. The mass of the tertiary component was determined to be M3 ∼ 7.5 MJup. We supposed that the tertiary companion is plausibly a giant planet. The stability of the giant planet was checked, and we found that the multiple system is stable.

Seismology of Giant Planets: General Overview and Results from the Kepler K2 Observations of Neptune

NASA Astrophysics Data System (ADS)

Gaulme, Patrick

2017-10-01

For this invited contribution, I was asked to give an overview about the application of helio and aster-oseismic techniques to study the interior of giant planets, and to specifically present the recent observations of Neptune by Kepler K2. Seismology applied to giant planets could drastically change our understanding of their deep interiors, as it has happened with the Earth, the Sun, and many main-sequence and evolved stars. The study of giant planets' composition is important for understanding both the mechanisms enabling their formation and the origins of planetary systems, in particular our own. Unfortunately, its determination is complicated by the fact that their interior is thought not to be homogeneous, so that spectroscopic determinations of atmospheric abundances are probably not representative of the planet as a whole. Instead, the determination of their composition and structure must rely on indirect measurements and interior models. Giant planets are mostly fluid and convective, which makes their seismology much closer to that of solar-like stars than that of terrestrial planets. Hence, helioseismology techniques naturally transfer to giant planets. In addition, two alternative methods can be used: photometry of the solar light reflected by planetary atmospheres, and ring seismology in the specific case of Saturn. The current decade has been promising thanks to the detection of Jupiter's acoustic oscillations with the ground-based imaging-spectrometer SYMPA and indirect detection of Saturn's f-modes in its rings by the NASA Cassini orbiter. This has motivated new projects of ground-based and space-borne instruments that are under development. The K2 observations represented the first opportunity to search for planetary oscillations with visible photometry. Despite the excellent quality of K2 data, the noise level of the power spectrum of the light curve was not low enough to detect Neptune's oscillations. The main results from the K2 observations are

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

Ammonium hydrosulfide and clouds in the atmospheres of the giant planets.

NASA Astrophysics Data System (ADS)

Ibragimov, K. Yu.; Solodovnik, A. A.

The physicochemical properties of two possible compounds - ammonium hydrosulfide (NH4SH) and ammonium sulfide (NH4)2S - that may be formed in a reaction of ammonia NH3 with hydrogen sulfide H2S are discussed, and the probability of their formation is analyzed on the basis of the Le Chatelier principle. It is shown that the conditions of their formation on the basis of available data on the concentration ratio of the reagents (NH3 and H2S) in the atmospheres of giant planets make the appearance of enough NH4SH for cloud formation highly problematic. Accordingly, the authors propose as an alternative candidate for a cloud-forming role ammonium sulfide (NH4)2S, for whose formation the conditions in the atmospheres of the giant planets are more favorable. The possible spatial localization of (NH4)2S clouds is estimated, and the result is used in an attempt to identify this compound as one of the chromophores.

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.

A Jupiter-mass planet around the K0 giant HD 208897

NASA Astrophysics Data System (ADS)

Yılmaz, M.; Sato, B.; Bikmaev, I.; Selam, S. O.; Izumiura, H.; Keskin, V.; Kambe, E.; Melnikov, S. S.; Galeev, A.; Özavcı, İ.; Irtuganov, E. N.; Zhuchkov, R. Ya.

2017-11-01

For over 10 years, we have carried out a precise radial velocity (RV) survey to find substellar companions around evolved G, K-type stars to extend our knowledge of planet formation and evolution. We performed high precision RV measurements for the giant star HD 208897 using an iodine (I2) absorption cell. The measurements were made at TÜBİTAK National Observatory (TUG; RTT150) and Okayama Astrophysical Observatory (OAO). For the origin of the periodic variation seen in the RV data of the star, we adopted a Keplerian motion caused by an unseen companion. We found that the star hosts a planet with a minimum mass of m2sini = 1.40 MJ, which is relatively low compared to those of known planets orbiting evolved intermediate-mass stars. The planet is in a nearly circular orbit with a period of P = 353 days at about 1 AU distance from the host star. The star is metal rich and located at the early phase of ascent along the red giant branch. The photometric observations of the star at Ankara University Kreiken Observatory (AUKR) and the Hipparcos photometry show no sign of variation with periods associated with the RV variation. Neither bisector velocity analysis nor analysis of the Ca II and Hα lines shows any correlation with the RV measurements. This work was supported by The Scientific and Technological Research Council of Turkey (TÜBİTAK), the project number of 114F099.

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).

THE ANGLO-AUSTRALIAN PLANET SEARCH. XXII. TWO NEW MULTI-PLANET SYSTEMS

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

Wittenmyer, Robert A.; Horner, J.; Salter, G. S.

2012-07-10

We report the detection of two new planets from the Anglo-Australian Planet Search. These planets orbit two stars each previously known to host one planet. The new planet orbiting HD 142 has a period of 6005 {+-} 427 days, and a minimum mass of 5.3 M{sub Jup}. HD 142c is thus a new Jupiter analog: a gas-giant planet with a long period and low eccentricity (e = 0.21 {+-} 0.07). The second planet in the HD 159868 system has a period of 352.3 {+-} 1.3 days and m sin i = 0.73 {+-} 0.05 M{sub Jup}. In both of thesemore » systems, including the additional planets in the fitting process significantly reduced the eccentricity of the original planet. These systems are thus examples of how multiple-planet systems can masquerade as moderately eccentric single-planet systems.« less

Mars’ Growth Stunted by an Early Giant Planet Instability

NASA Astrophysics Data System (ADS)

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

2017-10-01

Many dynamical aspects of the solar system can be explained by the outer planets experiencing a period of orbital instability. Though often correlated with a perceived delayed spike in the lunar cratering record known as the Late Heavy Bombardment (LHB), recent work suggests that this event may have occurred during the epoch of terrestrial planet formation. Though current simulations of terrestrial accretion can reproduce many observed qualities of the solar system, replicating the small mass of Mars requires modification to standard planet formation models. Here we use direct numerical simulations to show that an early instability in the outer solar system regularly yields properly sized Mars analogues. In 80% of simulations, we produce a Mars of the appropriate mass. Our most successful outcomes occur when the terrestrial planets evolve 10 million years (Myr), and accrete several Mars sized embryos in the Mars forming region before the instability takes place. Mars is left behind as a stranded embryo, while the remainder of these bodies are either ejected from the system or scattered towards the inner solar system where they deliver water to Earth. An early giant planet instability can thus replicate both the inner and outer solar system in a single model.

Runaway greenhouse effect on exomoons due to irradiation from hot, young giant planets

NASA Astrophysics Data System (ADS)

Heller, R.; Barnes, R.

2015-04-01

The Kepler space telescope has proven capable of detecting transits of objects almost as small as the Earth's Moon. Some studies suggest that moons as small as 0.2 Earth masses can be detected in the Kepler data by transit timing variations and transit duration variations of their host planets. If such massive moons exist around giant planets in the stellar habitable zone (HZ), then they could serve as habitats for extraterrestrial life. While earlier studies on exomoon habitability assumed the host planet to be in thermal equilibrium with the absorbed stellar flux, we here extend this concept by including the planetary luminosity from evolutionary shrinking. Our aim is to assess the danger of exomoons to be in a runaway greenhouse state due to extensive heating from the planet. We apply pre-computed evolution tracks for giant planets to calculate the incident planetary radiation on the moon as a function of time. Added to the stellar flux, the total illumination yields constraints on a moon's habitability. Ultimately, we include tidal heating to evaluate a moon's energy budget. We use a semi-analytical formula to parameterize the critical flux for the moon to experience a runaway greenhouse effect. Planetary illumination from a 13-Jupiter-mass planet onto an Earth-sized moon at a distance of ten Jupiter radii can drive a runaway greenhouse state on the moon for about 200 million years (Myr). When stellar illumination equivalent to that received by Earth from the Sun is added, then the runaway greenhouse holds for about 500 Myr. After 1000 Myr, the planet's habitable edge has moved inward to about six Jupiter radii. Exomoons in orbits with eccentricities of 0.1 experience strong tidal heating; they must orbit a 13-Jupiter-mass host beyond 29 or 18 Jupiter radii after 100 Myr (at the inner and outer boundaries of the stellar HZ, respectively), and beyond 13 Jupiter radii (in both cases) after 1000 Myr to be habitable. If a roughly Earth-sized, Earth-mass moon would

Flow of Planets, Not Weak Tidal Evolution, Produces the Short-Period Planet Distribution with More Planets than Expected

NASA Astrophysics Data System (ADS)

Taylor, Stuart F.

2013-01-01

The most unexpected planet finding is arguably the number of those with shorter periods than theorists had expected, because most such close planets had been expected to migrate into the star in shorter timescales than the ages of the stars. Subsequent effort has been made to show how tidal dissipation in stars due to planets could be weaker than expected, but we show how the occurrence distribution of differently-sized planets is more consistent with the explanation that these planets have more recently arrived as a flow of inwardly migrating planets, with giant planets more likely to be found while gradually going through a short period stage. This continual ``flow'' of new planets arriving from further out is presumably supplied by the flow likely responsible for the short period pileup of giant planets (Socrates+ 2011). We have previously shown that the shortest period region of the exoplanet occurrence distribution has a fall-off shaped by inward tidal migration due to stellar tides, that is, tides on the star caused by the planets (Taylor 2011, 2012). The power index of the fall-off of giant and intermediate radius planet candidates found from Kepler data (Howard+ 2011) is close to the index of 13/3 which is expected for planets in circular orbits undergoing tidal migration. However, there is a discrepancy of the strength of the tidal migration determined using fits to the giant and medium planets distributions. This discrepancy is best resolved by the explanation that more giant than medium radii planets migrate through these short period orbits. We also present a correlation between higher eccentricity of planetary orbits with higher Fe/H of host stars, which could be explained by high eccentricity planets being associated with recent episodes of other planets into stars. By the time these planets migrate to become hot Jupiters, the pollution may be mixed into the star. The clearing of other planets by migrating hot giant planets may result in hot Jupiters

Two New Long-period Giant Planets from the McDonald Observatory Planet Search and Two Stars with Long-period Radial Velocity Signals Related to Stellar Activity Cycles

NASA Astrophysics Data System (ADS)

Endl, Michael; Brugamyer, Erik J.; Cochran, William D.; MacQueen, Phillip J.; Robertson, Paul; Meschiari, Stefano; Ramirez, Ivan; Shetrone, Matthew; Gullikson, Kevin; Johnson, Marshall C.; Wittenmyer, Robert; Horner, Jonathan; Ciardi, David R.; Horch, Elliott; Simon, Attila E.; Howell, Steve B.; Everett, Mark; Caldwell, Caroline; Castanheira, Barbara G.

2016-02-01

We report the detection of two new long-period giant planets orbiting the stars HD 95872 and HD 162004 (ψ1 Dra B) by the McDonald Observatory planet search. The planet HD 95872b has a minimum mass of 4.6 {M}{{Jup}} and an orbital semimajor axis of 5.2 AU. The giant planet ψ1 Dra Bb has a minimum mass of 1.5 {M}{{Jup}} and an orbital semimajor axis of 4.4 AU. Both of these planets qualify as Jupiter analogs. These results are based on over one and a half decades of precise radial velocity (RV) measurements collected by our program using the McDonald Observatory Tull Coude spectrograph at the 2.7 m Harlan J. Smith Telescope. In the case of ψ1 Dra B we also detect a long-term nonlinear trend in our data that indicates the presence of an additional giant planet, similar to the Jupiter-Saturn pair. The primary of the binary star system, ψ1 Dra A, exhibits a very large amplitude RV variation due to another stellar companion. We detect this additional member using speckle imaging. We also report two cases—HD 10086 and HD 102870 (β Virginis)—of significant RV variation consistent with the presence of a planet, but that are probably caused by stellar activity, rather than reflexive Keplerian motion. These two cases stress the importance of monitoring the magnetic activity level of a target star, as long-term activity cycles can mimic the presence of a Jupiter-analog planet.

How empty are disk gaps opened by giant planets?

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

Fung, Jeffrey; Shi, Ji-Ming; Chiang, Eugene, E-mail: fung@astro.utoronto.ca

2014-02-20

Gap clearing by giant planets has been proposed to explain the optically thin cavities observed in many protoplanetary disks. How much material remains in the gap determines not only how detectable young planets are in their birth environments, but also how strong co-rotation torques are, which impacts how planets can survive fast orbital migration. We determine numerically how the average surface density inside the gap, Σ{sub gap}, depends on planet-to-star mass ratio q, Shakura-Sunyaev viscosity parameter α, and disk height-to-radius aspect ratio h/r. Our results are derived from our new graphics processing unit accelerated Lagrangian hydrodynamical code PEnGUIn and aremore » verified by independent simulations with ZEUS90. For Jupiter-like planets, we find Σ{sub gap}∝q {sup –2.2}α{sup 1.4}(h/r){sup 6.6}, and for near brown dwarf masses, Σ{sub gap}∝q {sup –1}α{sup 1.3}(h/r){sup 6.1}. Surface density contrasts inside and outside gaps can be as large as 10{sup 4}, even when the planet does not accrete. We derive a simple analytic scaling, Σ{sub gap}∝q {sup –2}α{sup 1}(h/r){sup 5}, that compares reasonably well to empirical results, especially at low Neptune-like masses, and use discrepancies to highlight areas for progress.« less

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

The development of spheroidal bodies theory for proto-planetary dynamics problem solving

NASA Astrophysics Data System (ADS)

Krot, A. M.

2007-08-01

There is not a full statistical equilibrium in a gas-dust proto-planetary cloud because of long relaxation time for proto-planet formation in own gravitational field. This protoplanetary system behavior can be described by Jeans equation in partial derivations relatively a distribution function. The problem for finding a general solution of Jeans equation is connected directly with an analytical expression for potential of gravitational field. Thus, the determination of gravitational potential is the main problem of statistical dynamics for proto-planetary system. The work shows this task of protoplanetary dynamics can be solved on the basis of spheroidal bodies theory [1]-[4]. Within the framework of this theory, cosmological bodies have fuzzy outlines and are represented by means of spheroidal forms. The proposed theory follows from the conception for forming a spheroidal body as a proto-planet from dust-like nebula; it permits to derive the form of distribution functions for an immovable spheroidal body [1],[2] and rotating one [3],[4] as well as their density masses (gravitational potentials and strengths) and also to find the distribution function of specific angular momentum for the rotating spheroidal body [4]. References: [1] A.M.Krot, Achievement in Modern Radioelectronics, 1996, no.8, pp.66-81 (in Russian). [2] A.M.Krot, Proc. SPIE's 13thAnnual Intern.Symp. "AeroSense", Orlando, Florida, USA, 1999, vol.3710, pp.1248-1259. [3] A.M.Krot, Proc. 35th COSPAR Scientific Assembly, Paris, France, 2004, Abstract A-00162. [4] A.Krot, Proc. EGU General Assembly, Vienna, Austria, 2006, Geophys. Res. Abstracts, vol.8, A-00216; SRef-ID: 1607-7962/gra/.

Anatomy of a flaring proto-planetary disk around a young intermediate-mass star.

PubMed

Lagage, Pierre-Olivier; Doucet, Coralie; Pantin, Eric; Habart, Emilie; Duchêne, Gaspard; Ménard, François; Pinte, Christophe; Charnoz, Sébastien; Pel, Jan-Willem

2006-10-27

Although planets are being discovered around stars more massive than the Sun, information about the proto-planetary disks where such planets have built up is sparse. We have imaged mid-infrared emission from polycyclic aromatic hydrocarbons at the surface of the disk surrounding the young intermediate-mass star HD 97048 and characterized the disk. The disk is in an early stage of evolution, as indicated by its large content of dust and its hydrostatic flared geometry, indicative of the presence of a large amount of gas that is well mixed with dust and gravitationally stable. The disk is a precursor of debris disks found around more-evolved A stars such as beta-Pictoris and provides the rare opportunity to witness the conditions prevailing before (or during) planet formation.

DIRECT DETECTION OF PRECURSORS OF GAS GIANTS FORMED BY GRAVITATIONAL INSTABILITY WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

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

Mayer, Lucio; Peters, Thomas; Pineda, Jaime E.

Phases of gravitational instability are expected in the early phases of disk evolution, when the disk mass is still a substantial fraction of the mass of the star. Disk fragmentation into sub-stellar objects could occur in the cold exterior part of the disk. Direct detection of massive gaseous clumps on their way to collapse into gas giant planets would offer an unprecedented test of the disk instability model. Here we use state-of-the-art 3D radiation-hydro simulations of disks undergoing fragmentation into massive gas giants, post-processed with RADMC-3D to produce dust continuum emission maps. These are then fed into the Common Astronomymore » Software Applications (CASA) ALMA simulator. The synthetic maps show that both overdense spiral arms and actual clumps at different stages of collapse can be detected with the Atacama Large Millimeter/submillimeter Array (ALMA) in the full configuration at the distance of the Ophiuchus star forming region (125 pc). The detection of clumps is particularly effective at shorter wavelengths (690 GHz) combining two resolutions with multi-scale clean. Furthermore, we show that a flux-based estimate of the mass of a protoplanetary clump can be comparable to a factor of three higher than the gravitationally bound clump mass. The estimated mass depends on the assumed opacity, and on the gas temperature, which should be set using the input of radiation-hydro simulations. We conclude that ALMA has the capability to detect “smoking gun” systems that are a signpost of the disk instability model for gas giant planet formation.« less

Kepler-36: a pair of planets with neighboring orbits and dissimilar densities.

PubMed

Carter, Joshua A; Agol, Eric; Chaplin, William J; Basu, Sarbani; Bedding, Timothy R; Buchhave, Lars A; Christensen-Dalsgaard, Jørgen; Deck, Katherine M; Elsworth, Yvonne; Fabrycky, Daniel C; Ford, Eric B; Fortney, Jonathan J; Hale, Steven J; Handberg, Rasmus; Hekker, Saskia; Holman, Matthew J; Huber, Daniel; Karoff, Christopher; Kawaler, Steven D; Kjeldsen, Hans; Lissauer, Jack J; Lopez, Eric D; Lund, Mikkel N; Lundkvist, Mia; Metcalfe, Travis S; Miglio, Andrea; Rogers, Leslie A; Stello, Dennis; Borucki, William J; Bryson, Steve; Christiansen, Jessie L; Cochran, William D; Geary, John C; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer; Howard, Andrew W; Jenkins, Jon M; Klaus, Todd; Koch, David G; Latham, David W; MacQueen, Phillip J; Sasselov, Dimitar; Steffen, Jason H; Twicken, Joseph D; Winn, Joshua N

2012-08-03

In the solar system, the planets' compositions vary with orbital distance, with rocky planets in close orbits and lower-density gas giants in wider orbits. The detection of close-in giant planets around other stars was the first clue that this pattern is not universal and that planets' orbits can change substantially after their formation. Here, we report another violation of the orbit-composition pattern: two planets orbiting the same star with orbital distances differing by only 10% and densities differing by a factor of 8. One planet is likely a rocky "super-Earth," whereas the other is more akin to Neptune. These planets are 20 times more closely spaced and have a larger density contrast than any adjacent pair of planets in the solar system.

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

Giant Planets around FGK Stars Probably Form through Core Accretion

NASA Astrophysics Data System (ADS)

Wang, Wei; Wang, Liang; Li, Xiang; Chen, Yuqin; Zhao, Gang

2018-06-01

We present a statistical study of the planet–metallicity (P–M) correlation by comparing the 744 stars with candidate planets (SWPs) in the Kepler field that have been observed with LAMOST, and a sample of distance-independent, fake “twin” stars in the Kepler field with no planet reported (CKSNPs) yet. With well-defined and carefully selected large samples, we find for the first time a turnoff P–M correlation of Δ[Fe/H]SWPs–SNPs, which on average increases from ∼0.00 ± 0.03 dex to 0.06 ± 0.03 dex, and to 0.12 ± 0.03 for stars with Earth-, Neptune-, and Jupiter-sized planets successively, and then declines to ∼‑0.01 ± 0.03 dex for more massive planets or brown dwarfs. Moreover, the percentage of those systems with positive Δ[Fe/H] has the same turnoff pattern. We also find that FG-type stars follow this general trend, but K-type stars are different. Moderate metal enhancement (∼0.1–0.2 dex) for K-type stars with planets of radii between 2 and 4 R ⊕, compared to CKSNPs is observed, which indicates much higher metallicities are required for Super-Earths and Neptune-sized planets to form around K-type stars. We point out that the P–M correlation is actually metallicity-dependent, i.e., the correlation is positive at solar and supersolar metallicities, and negative at subsolar metallicities. No steady increase of Δ[Fe/H] against planet sizes is observed for rocky planets, excluding the pollution scenario as a major mechanism for the P–M correlation. All these clues suggest that giant planets probably form differently from rocky planets or more massive planets/brown dwarfs, and the core accretion scenario is highly favored, and high metallicity is a prerequisite for massive planets to form.

The Occurrence of Additional Giant Planets Inside the Water-Ice Line in Systems with Hot Jupiters: Evidence Against High-Eccentricity Migration

NASA Astrophysics Data System (ADS)

Schlaufman, Kevin C.; Winn, Joshua N.

2016-07-01

The origin of Jupiter-mass planets with orbital periods of only a few days is still uncertain. It is widely believed that these planets formed near the water-ice line of the protoplanetary disk, and subsequently migrated into much smaller orbits. Most of the proposed migration mechanisms can be classified either as disk-driven migration, or as excitation of a very high eccentricity followed by tidal circularization. In the latter scenario, the giant planet that is destined to become a hot Jupiter spends billions of years on a highly eccentric orbit, with apastron near the water-ice line. Eventually, tidal dissipation at periastron shrinks and circularizes the orbit. If this is correct, then it should be especially rare for hot Jupiters to be accompanied by another giant planet interior to the water-ice line. Using the current sample of giant planets discovered with the Doppler technique, we find that hot Jupiters with P orb < 10 days are no more or less likely to have exterior Jupiter-mass companions than longer-period giant planets with P orb ≥ 10 days. This result holds for exterior companions both inside and outside of the approximate location of the water-ice line. These results are difficult to reconcile with the high-eccentricity migration scenario for hot Jupiter formation.

Exploring H2O Prominence in Reflection Spectra of Cool Giant Planets

NASA Astrophysics Data System (ADS)

MacDonald, Ryan J.; Marley, Mark S.; Fortney, Jonathan J.; Lewis, Nikole K.

2018-05-01

The H2O abundance of a planetary atmosphere is a powerful indicator of formation conditions. Inferring H2O in the solar system giant planets is challenging, due to condensation depleting the upper atmosphere of water vapor. Substantially warmer hot Jupiter exoplanets readily allow detections of H2O via transmission spectroscopy, but such signatures are often diminished by the presence of clouds composed of other species. In contrast, highly scattering water clouds can brighten planets in reflected light, enhancing molecular signatures. Here, we present an extensive parameter space survey of the prominence of H2O absorption features in reflection spectra of cool (Teff < 400 K) giant exoplanetary atmospheres. The impact of effective temperature, gravity, metallicity, and sedimentation efficiency is explored. We find prominent H2O features around 0.94 μm, 0.83 μm, and across a wide spectral region from 0.4 to 0.73 μm. The 0.94 μm feature is only detectable where high-altitude water clouds brighten the planet: Teff ∼ 150 K, g ≳ 20 ms‑2, fsed ≳ 3, m ≲ 10× solar. In contrast, planets with g ≲ 20 ms‑2 and Teff ≳ 180 K display substantially prominent H2O features embedded in the Rayleigh scattering slope from 0.4 to 0.73 μm over a wide parameter space. High fsed enhances H2O features around 0.94 μm, and enables these features to be detected at lower temperatures. High m results in dampened H2O absorption features, due to water vapor condensing to form bright, optically thick clouds that dominate the continuum. We verify these trends via self-consistent modeling of the low-gravity exoplanet HD 192310c, revealing that its reflection spectrum is expected to be dominated by H2O absorption from 0.4 to 0.73 μm for m ≲ 10× solar. Our results demonstrate that H2O is manifestly detectable in reflected light spectra of cool giant planets only marginally warmer than Jupiter, providing an avenue to directly constrain the C/O and O/H ratios of a hitherto

Layered semi-convection and tides in giant planet interiors. I. Propagation of internal waves

NASA Astrophysics Data System (ADS)

André, Q.; Barker, A. J.; Mathis, S.

2017-09-01

Context. Layered semi-convection is a possible candidate to explain Saturn's luminosity excess and the abnormally large radius of some hot Jupiters. In giant planet interiors, it could lead to the creation of density staircases, which are convective layers separated by thin stably stratified interfaces. These are also observed on Earth in some lakes and in the Arctic Ocean. Aims: We aim to study the propagation of internal waves in a region of layered semi-convection, with the aim to predict energy transport by internal waves incident upon a density staircase. The goal is then to understand the resulting tidal dissipation when these waves are excited by other bodies such as moons in giant planets systems. Methods: We used a local Cartesian analytical model, taking into account the complete Coriolis acceleration at any latitude, thus generalising previous works. We used a model in which stably stratified interfaces are infinitesimally thin, before relaxing this assumption with a second model that assumes a piecewise linear stratification. Results: We find transmission of incident internal waves to be strongly affected by the presence of a density staircase, even if these waves are initially pure inertial waves (which are restored by the Coriolis acceleration). In particular, low-frequency waves of all wavelengths are perfectly transmitted near the critical latitude, defined by θc = sin-1(ω/ 2Ω), where ω is the wave's frequency and Ω is the rotation rate of the planet. Otherwise, short-wavelength waves are only efficiently transmitted if they are resonant with a free mode (interfacial gravity wave or short-wavelength inertial mode) of the staircase. In all other cases, waves are primarily reflected unless their wavelengths are longer than the vertical extent of the entire staircase (not just a single step). Conclusions: We expect incident internal waves to be strongly affected by the presence of a density staircase in a frequency-, latitude- and wavelength

The first H-band spectrum of the giant planet β Pictoris b

DOE PAGES

Chilcote, Jeffrey; Barman, Travis; Fitzgerald, Michael P.; ...

2014-12-12

Using the recently installed Gemini Planet Imager (GPI), we have obtained the first H-band spectrum of the planetary companion to the nearby young star β Pictoris. GPI is designed to image and provide low-resolution spectra of Jupiter-sized, self-luminous planetary companions around young nearby stars. These observations were taken covering the H band (1.65 μm). The spectrum has a resolving power of ~45 and demonstrates the distinctive triangular shape of a cool substellar object with low surface gravity. Using atmospheric models, we find an effective temperature of 1600-1700 K and a surface gravity of log (g) = 3.5-4.5 (cgs units). Thesemore » values agree well with "hot-start" predictions from planetary evolution models for a gas giant with mass between 10 and 12 M Jup and age between 10 and 20 Myr.« less

On the origin and composition of Theia: Constraints from new models of the Giant Impact

NASA Astrophysics Data System (ADS)

Meier, M. M. M.; Reufer, A.; Wieler, R.

2014-11-01

Knowing the isotopic composition of Theia, the proto-planet which collided with the Earth in the Giant Impact that formed the Moon, could provide interesting insights on the state of homogenization of the inner Solar System at the late stages of terrestrial planet formation. We use the known isotopic and modeled chemical compositions of the bulk silicate mantles of Earth and Moon and combine them with different Giant Impact models, to calculate the possible ranges of isotopic composition of Theia in O, Si, Ti, Cr, Zr and W in each model. We compare these ranges to the isotopic composition of carbonaceous chondrites, Mars, and other Solar System materials. In the absence of post-impact isotopic re-equilibration, the recently proposed high angular momentum models of the Giant Impact ("impact-fission", Cúk, M., Stewart, S.T. [2012]. Science 338, 1047; and "merger", Canup, R.M. [2012]. Science 338, 1052) allow - by a narrow margin - for a Theia similar to CI-chondrites, and Mars. The "hit-and-run" model (Reufer, A., Meier, M.M.M., Benz, W., Wieler, R. [2012]. Icarus 221, 296-299) allows for a Theia similar to enstatite-chondrites and other Earth-like materials. If the Earth and Moon inherited their different mantle FeO contents from the bulk mantles of the proto-Earth and Theia, the high angular momentum models cannot explain the observed difference. However, both the hit-and-run as well as the classical or "canonical" Giant Impact model naturally explain this difference as the consequence of a simple mixture of two mantles with different FeO. Therefore, the simplest way to reconcile the isotopic similarity, and FeO dissimilarity, of Earth and Moon is a Theia with an Earth-like isotopic composition and a higher (∼20%) mantle FeO content.

The role of plasma/neutral source and loss processes in shaping the giant planet magnetospheres

NASA Astrophysics Data System (ADS)

Delamere, P. A.

2014-12-01

The giant planet magnetospheres are filled with neutral and ionized gases originating from satellites orbiting deep within the magnetosphere. The complex chemical and physical pathways for the flow of mass and energy in this partially ionized plasma environment is critical for understanding magnetospheric dynamics. The flow of mass at Jupiter and Saturn begins, primarily, with neutral gases emanating from Io (~1000 kg/s) and Enceladus (~200 kg/s). In addition to ionization losses, the neutral gases are absorbed by the planet, its rings, or escape at high speeds from the magnetosphere via charge exchange reactions. The net result is a centrifugally confined torus of plasma that is transported radially outward, distorting the magnetic field into a magnetodisc configuration. Ultimately the plasma is lost to the solar wind. A critical parameter for shaping the magnetodisc and determining its dynamics is the radial plasma mass transport rate (~500 kg/s and ~50 kg/s for Jupiter and Saturn respectively). Given the plasma transport rates, several simple properties of the giant magnetodiscs can be estimated including the physical scale of the magnetosphere, the magnetic flux transport, and the magnitude of azimuthal magnetic field bendback. We will discuss transport-related magnetic flux conservation and the mystery of plasma heating—two critical issues for shaping the giant planet magnetospheres.

Migration Processes and Volatiles Inventory to the Inner Planets

NASA Technical Reports Server (NTRS)

Marov, M. Y.; Ipatov, S. I.

2004-01-01

Comets and asteroids colliding with the terrestrial planets can deliver volatiles and organic or prebiotic compounds to the planets, thereby depositing on the planets the fundamental building-blocks for life. The inner planets contain heavier and cosmically less abundant elements in an iron-silicate matrix than the giant planets. This can be caused by the following three mechanisms: uneven fractionation and condensation in the accretionary disk; unequal degree of degassing of the composed matter; and heterogeneous accretion. Asteroid-size bodies consisting of the last low-temperature condensates (similar to most primitive chondritic meteorites, and enriched in hydrated silicates and trapped gases) are believed to have fallen onto the inner planets during the process of the giant planets formation. The relative contribution of either endogenous (i.e. outgassing) or exogenous (i.e. asteroid/comet collisions) sources is difficult to assess, although it is constrained by the pattern of noble gas abundances in the planetary atmospheres.

Discovery of a warm, dusty giant planet around HIP 65426

NASA Astrophysics Data System (ADS)

Chauvin, G.; Desidera, S.; Lagrange, A.-M.; Vigan, A.; Gratton, R.; Langlois, M.; Bonnefoy, M.; Beuzit, J.-L.; Feldt, M.; Mouillet, D.; Meyer, M.; Cheetham, A.; Biller, B.; Boccaletti, A.; D'Orazi, V.; Galicher, R.; Hagelberg, J.; Maire, A.-L.; Mesa, D.; Olofsson, J.; Samland, M.; Schmidt, T. O. B.; Sissa, E.; Bonavita, M.; Charnay, B.; Cudel, M.; Daemgen, S.; Delorme, P.; Janin-Potiron, P.; Janson, M.; Keppler, M.; Le Coroller, H.; Ligi, R.; Marleau, G. D.; Messina, S.; Mollière, P.; Mordasini, C.; Müller, A.; Peretti, S.; Perrot, C.; Rodet, L.; Rouan, D.; Zurlo, A.; Dominik, C.; Henning, T.; Menard, F.; Schmid, H.-M.; Turatto, M.; Udry, S.; Vakili, F.; Abe, L.; Antichi, J.; Baruffolo, A.; Baudoz, P.; Baudrand, J.; Blanchard, P.; Bazzon, A.; Buey, T.; Carbillet, M.; Carle, M.; Charton, J.; Cascone, E.; Claudi, R.; Costille, A.; Deboulbe, A.; De Caprio, V.; Dohlen, K.; Fantinel, D.; Feautrier, P.; Fusco, T.; Gigan, P.; Giro, E.; Gisler, D.; Gluck, L.; Hubin, N.; Hugot, E.; Jaquet, M.; Kasper, M.; Madec, F.; Magnard, Y.; Martinez, P.; Maurel, D.; Le Mignant, D.; Möller-Nilsson, O.; Llored, M.; Moulin, T.; Origné, A.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Puget, P.; Rabou, P.; Ramos, J.; Rigal, R.; Rochat, S.; Roelfsema, R.; Rousset, G.; Roux, A.; Salasnich, B.; Sauvage, J.-F.; Sevin, A.; Soenke, C.; Stadler, E.; Suarez, M.; Weber, L.; Wildi, F.; Antoniucci, S.; Augereau, J.-C.; Baudino, J.-L.; Brandner, W.; Engler, N.; Girard, J.; Gry, C.; Kral, Q.; Kopytova, T.; Lagadec, E.; Milli, J.; Moutou, C.; Schlieder, J.; Szulágyi, J.; Thalmann, C.; Wahhaj, Z.

2017-09-01

Aims: The SHINE program is a high-contrast near-infrared survey of 600 young, nearby stars aimed at searching for and characterizing new planetary systems using VLT/SPHERE's unprecedented high-contrast and high-angular-resolution imaging capabilities. It is also intended to place statistical constraints on the rate, mass and orbital distributions of the giant planet population at large orbits as a function of the stellar host mass and age to test planet-formation theories. Methods: We used the IRDIS dual-band imager and the IFS integral field spectrograph of SPHERE to acquire high-contrast coronagraphic differential near-infrared images and spectra of the young A2 star HIP 65426. It is a member of the 17 Myr old Lower Centaurus-Crux association. Results: At a separation of 830 mas (92 au projected) from the star, we detect a faint red companion. Multi-epoch observations confirm that it shares common proper motion with HIP 65426. Spectro-photometric measurements extracted with IFS and IRDIS between 0.95 and 2.2 μm indicate a warm, dusty atmosphere characteristic of young low-surface-gravity L5-L7 dwarfs. Hot-start evolutionary models predict a luminosity consistent with a 6-12 MJup, Teff = 1300-1600 K and R = 1.5 ± 0.1 RJup giant planet. Finally, the comparison with Exo-REM and PHOENIX BT-Settl synthetic atmosphere models gives consistent effective temperatures but with slightly higher surface gravity solutions of log (g) = 4.0-5.0 with smaller radii (1.0-1.3 RJup). Conclusions: Given its physical and spectral properties, HIP 65426 b occupies a rather unique placement in terms of age, mass, and spectral-type among the currently known imaged planets. It represents a particularly interesting case to study the presence of clouds as a function of particle size, composition, and location in the atmosphere, to search for signatures of non-equilibrium chemistry, and finally to test the theory of planet formation and evolution. Based on observations collected at La Silla

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.

Physical Conditions and Exobiology Potential of Icy Satellites of the Giant Planets

NASA Astrophysics Data System (ADS)

Simakov, M. B.

2017-05-01

All giant planets of the Solar system have a big number of satellites. A small part of them consist very large bodies, quite comparable to planets of terrestrial type, but including very significant share of water ice. Galileo spacecraft has given indications, primarily from magnetometer and gravity data, of the possibility that three of Jupiter's four large moons, Europa, Ganymede and Callisto have internal oceans. Formation of such satellites is a natural phenomenon, and satellite systems definitely should exist at extrasolar planets. The most recent models of the icy satellites interior lead to the conclusion that a substantial liquid layer exists today under relatively thin ice cover inside. The putative internal water ocean provide some exobiological niches on these bodies. We can see all conditions needed for origin and evolution of biosphere - liquid water, complex organic chemistry and energy sources for support of biological processes - are on the moons. The existing of liquid water ocean within icy world can be consequences of the physical properties of water ice, and they neither require the addition of antifreeze substances nor any other special conditions. On Earth life exists in all niches where water exists in liquid form for at least a portion of the year. Possible metabolic processes, such as nitrate/nitrite reduction, sulfate reduction and methanogenesis could be suggested for internal oceans of Titan and Jovanian satellites. Excreted products of the primary chemoautotrophic organisms could serve as a source for other types of microorganisms (heterotrophes). Subglacial life may be widespread among such planetary bodies as satellites of extrasolar giant planets, detected in our Galaxy.

NH4SH and cloud cover in the atmospheres of the giant planets

NASA Astrophysics Data System (ADS)

Ibragimov, K. Iu.; Solodovnik, A. A.

1991-02-01

The probability of the formation of NH4SH and (NH4)2S is examined on the basis of the Le Chatelier principle. It is shown that it is very doubtful if NH4SH can be created in the atmospheres of the giant planets in quantities sufficient for cloud formation. Thus (NH4)2S is considered as a more likely candidate for cloud formation in the atmospheres of these planets, inasmuch as the conditions for its production there are more favorable.

Giant impacts on giant planets

NASA Astrophysics Data System (ADS)

de Pater, Imke

2017-08-01

The 2009 impact and recent superbolides on Jupiter caught the world by surprise and cast doubt on impactor flux estimates for the outer solar system. Enhanced amateur planetary imaging techniques yield both high spatial resolution (enabling the 2009 impact debris field detection) and rapid frame rates (enabling the 2010/2012 impact flash detections and lightcurve measurements).We propose a ToO program to image future impacts on Jupiter and Saturn. To remove the possibility of impact cloud non-detections, the program will be triggered only if an existing impact debris field is seen, an object on a collision course with Jupiter or Saturn is discovered, or an impact light curve is measured with an estimated total energy large enough to generate an impact cloud in a giant planet atmosphere (10^19 J).HST provides the only way to image these events in the ultraviolet, providing information on aerosol altitudes and on smaller particles that are less visible to ground-based infrared observations. High-resolution imaging with proper timing (not achievable from the ground) is required to measure precisely both the velocity fields of impact sites and the optical spectrum of impact debris. HST observations of past impacts on Jupiter have also served both as cornerstones of science investigations at other wavelengths and as vehicles for effective public outreach.Large outer solar system impacts are governed by the same physics as in the terrestrial events that dominate the impact threat to humans. Studying the behavior of impactors of various sizes and compositions, as they enter the atmosphere at varying angles and speeds, will better quantify terrestrial impact hazards.

Retired A Stars Revisited: An Updated Giant Planet Occurrence Rate as a Function of Stellar Metallicity and Mass

NASA Astrophysics Data System (ADS)

Ghezzi, Luan; Montet, Benjamin T.; Johnson, John Asher

2018-06-01

Exoplanet surveys of evolved stars have provided increasing evidence that the formation of giant planets depends not only on stellar metallicity ([Fe/H]) but also on the mass ({M}\\star ). However, measuring accurate masses for subgiants and giants is far more challenging than it is for their main-sequence counterparts, which has led to recent concerns regarding the veracity of the correlation between stellar mass and planet occurrence. In order to address these concerns, we use HIRES spectra to perform a spectroscopic analysis on a sample of 245 subgiants and derive new atmospheric and physical parameters. We also calculate the space velocities of this sample in a homogeneous manner for the first time. When reddening corrections are considered in the calculations of stellar masses and a ‑0.12 {M}ȯ offset is applied to the results, the masses of the subgiants are consistent with their space velocity distributions, contrary to claims in the literature. Similarly, our measurements of their rotational velocities provide additional confirmation that the masses of subgiants with {M}\\star ≥slant 1.6 M ⊙ (the “retired A stars”) have not been overestimated in previous analyses. Using these new results for our sample of evolved stars, together with an updated sample of FGKM dwarfs, we confirm that giant planet occurrence increases with both stellar mass and metallicity up to 2.0 M ⊙. We show that the probability of formation of a giant planet is approximately a one-to-one function of the total amount of metals in the protoplanetary disk {M}\\star {10}[{Fe/{{H}}]}. This correlation provides additional support for the core accretion mechanism of planet formation.

Radiative Transfer Modeling in Proto-planetary Disks

NASA Astrophysics Data System (ADS)

Kasper, David; Jang-Condell, Hannah; Kloster, Dylan

2016-01-01

Young Stellar Objects (YSOs) are rich astronomical research environments. Planets form in circumstellar disks of gas and dust around YSOs. With ever increasing capabilities of the observational instruments designed to look at these proto-planetary disks, most notably GPI, SPHERE, and ALMA, more accurate interfaces must be made to connect modeling of the disks with observation. PaRTY (Parallel Radiative Transfer in YSOs) is a code developed previously to model the observable density and temperature structure of such a disk by self-consistently calculating the structure of the disk based on radiative transfer physics. We present upgrades we are implementing to the PaRTY code to improve its accuracy and flexibility. These upgrades include: creating a two-sided disk model, implementing a spherical coordinate system, and implementing wavelength-dependent opacities. These upgrades will address problems in the PaRTY code of infinite optical thickness, calculation under/over-resolution, and wavelength-independent photon penetration depths, respectively. The upgraded code will be used to better model disk perturbations resulting from planet formation.

Are Strong Zonal Winds in Giant Planets Caused by Density-Stratification?

NASA Astrophysics Data System (ADS)

Verhoeven, J.; Stellmach, S.

2012-12-01

One of the most striking features of giant planets like Jupiter and Saturn are the zonal wind patterns observed on their surfaces. The mechanism that drives this differential rotation is still not clearly identified and is currently strongly debated in the astro- and geophysics community. Different mechanisms have been proposed over the last decades. Here, a recently discovered mechanism based on background density stratification (Glatzmaier et al., 2009) is investigated. This mechanism has the potential to overcome known difficulties of previous explanations and its efficiency has been demonstrated in 2-d simulations covering equatorial planes. By performing highly resolved numerical simulations in a local Cartesian geometry, we are able to test the efficiency and functionality of this mechanism in turbulent, rotating convection in three spatial dimensions. The choice of a Cartesian model geometry naturally excludes other known mechanisms capable of producing differential rotation, thus allowing us to investigate the role of density stratification in isolation. Typically, the dynamics can be classified into two main regimes: A regime exhibiting strong zonal winds for weak to moderate thermal driving and a regime where zonal winds are largely absent in the case of a strong thermal forcing. Our results indicate that previous 2-d results must be handled with care and can only explain parts of the full 3-d behavior. We show that the density-stratification mechanism tends to operate in a more narrow parameter range in 3-d as compared to 2-d simulations. The dynamics of the regime transition is shown to differ in both cases, which renders scaling laws derived from two-dimensional studies questionable. Based on our results, we provide estimates for the importance of the density-stratification mechanism for giant planets like Jupiter (strong density stratification), for systems like the Earth's core (weak density stratification) and compare its efficiency with other

Clouds in exoplanet atmospheres: comparison of two apparently similar giant planets

NASA Astrophysics Data System (ADS)

Bruno, Giovanni; Lewis, Nikole K.; Stevenson, Kevin; Deming, Drake; Filippazzo, Joe; Fraine, Jonathan D.; Hill, Matthew; Kilpatrick, Brian; Line, Michael R.; Morley, Caroline; Wakeford, Hannah; Collins, Karen A.; Conti, Dennis M.; Garlitz, Joseph; Rodriguez, Joseph

2017-06-01

We present a study aimed at a better understanding of the physics of clouds, which have been shown prevalent in hot Jupiter atmospheres. We compare and contrast the atmospheric spectra of WASP-67 b and HAT-P-38 b, part of our HST/WFC3 and Spitzer observation programs of exoplanets in transmission spectroscopy and secondary eclipses. These two planets lie in a very similar region of the equilibrium temperature-surface gravity parameter space and their compared analysis is therefore particularly significant.With the help of retrieval exercises on the molecules characterizing the 1.1-1.7 microns WFC3 spectra, we discuss which conclusions can be drawn about the atmospheric processes of these two giant planets.

Revisiting the Microlensing Event OGLE 2012-BLG-0026: A Solar Mass Star with Two Cold Giant Planets

NASA Technical Reports Server (NTRS)

Beaulieu, J.-P.; Bennett, D. P.; Batista, V.; Fukui, A.; Marquette, J.-B.; Brillant, S.; Cole, A. A.; Rogers, L. A.; Sumi, T.; Abe, F.

2016-01-01

Two cold gas giant planets orbiting a G-type main-sequence star in the galactic disk were previously discovered in the high-magnification microlensing event OGLE-2012-BLG-0026. Here, we present revised host star flux measurements and a refined model for the two-planet system using additional light curve data. We performed high angular resolution adaptive optics imaging with the Keck and Subaru telescopes at two epochs while the source star was still amplified. We detected the lens flux, H = 16.39 +/- 0.08. The lens, a disk star, is brighter than predicted from the modeling in the original study. We revisited the light curve modeling using additional photometric data from the B and C telescope in New Zealand and CTIO 1.3 m H-band light curve. We then include the Keck and Subaru adaptive optic observation constraints. The system is composed of an approximately 4-9 Gyr lens star of M(sub lens) = 1.06 +/- 0.05 solar mass at a distance of D(sub lens) = 4.0 +/- 0.3 kpc, orbited by two giant planets of 0.145 +/- 0.008 M(sub Jup) and 0.86 +/- 0.06 M(sub Jup), with projected separations of 4.0 +/- 0.5 au and 4.8 +/- 0.7 au, respectively. Because the lens is brighter than the source star by 16 +/- 8% in H, with no other blend within one arcsec, it will be possible to estimate its metallicity using subsequent IR spectroscopy with 8-10 m class telescopes. By adding a constraint on the metallicity it will be possible to refine the age of the system.

Clearing Residual Planetesimals by Sweeping Secular Resonances in Transitional Disks: A Lone-planet Scenario for the Wide Gaps in Debris Disks around Vega and Fomalhaut

NASA Astrophysics Data System (ADS)

Zheng, Xiaochen; Lin, Douglas N. C.; Kouwenhoven, M. B. N.; Mao, Shude; Zhang, Xiaojia

2017-11-01

Extended gaps in the debris disks of both Vega and Fomalhaut have been observed. These structures have been attributed to tidal perturbations by multiple super-Jupiter gas giant planets. Within the current observational limits, however, no such massive planets have been detected. Here we propose a less stringent “lone-planet” scenario to account for the observed structure with a single eccentric gas giant and suggest that clearing of these wide gaps is induced by its sweeping secular resonance. With a series of numerical simulations, we show that the gravitational potential of the natal disk induces the planet to precess. At the locations where its precession frequency matches the precession frequency the planet imposes on the residual planetesimals, their eccentricity is excited by its resonant perturbation. Due to the hydrodynamic drag by the residual disk gas, the planetesimals undergo orbital decay as their excited eccentricities are effectively damped. During the depletion of the disk gas, the planet’s secular resonance propagates inward and clears a wide gap over an extended region of the disk. Although some residual intermediate-size planetesimals may remain in the gap, their surface density is too low to either produce super-Earths or lead to sufficiently frequent disruptive collisions to generate any observable dusty signatures. The main advantage of this lone-planet sweeping-secular-resonance model over the previous multiple gas giant tidal truncation scenario is the relaxed requirement on the number of gas giants. The observationally inferred upper mass limit can also be satisfied provided the hypothetical planet has a significant eccentricity. A significant fraction of solar or more massive stars bear gas giant planets with significant eccentricities. If these planets acquired their present-day kinematic properties prior to the depletion of their natal disks, their sweeping secular resonance would effectively impede the retention of neighboring

Ice Giant Exploration

NASA Astrophysics Data System (ADS)

Rymer, A. M.; Arridge, C. S.; Masters, A.; Turtle, E. P.; Simon, A. A.; Hofstadter, M. D.; Turrini, D.; Politi, R.

2015-12-01

The Ice Giants in our solar system, Uranus and Neptune, are fundamentally different from their Gas Giant siblings Jupiter and Saturn, from the different proportions of rock and ice to the configuration of their planetary magnetic fields. Kepler space telescope discoveries of exo-planets indicate that planets of this type are among the most ubiquitous universally and therefore a future mission to explore the nature of the Ice Giants in our own solar system will provide insights into the nature of extra-solar system objects in general. Uranus has the smallest self- luminosity of all the planets, potentially related to catastrophic events early in the planet's history, which also may explain Uranus' large obliquity. Uranus' atmosphere is subject to extreme seasonal forcing making it unique in the Solar System. Neptune is also unique in a number of ways, notably its large moon Triton which is likely a captured Kuiper Belt Object and one of only two moons in the solar system with a robustly collisional atmosphere. Similar to Uranus, the angle between the solar wind and the magnetic dipole axis is subject to large-amplitude variations on both diurnal and seasonal timescales, but peculiarly it has one of the quietest magnetospheres of the solar system, at least according to Voyager 2, the only spacecraft to encounter Neptune to date. A comprehensive mission, as advocated in the Decadal Survey, would provide enormous science return but is also challenging and expensive. In this presentation we will discuss mission scenarios and suggest how collaboration between disciplines and internationally can help us to pursue a mission that includes Ice Giant exploration.

Model Atmospheres for Massive Gas Giants with Thick Clouds: Application to the HR 8799 Planets and Predictions for Future Detections

NASA Astrophysics Data System (ADS)

Madhusudhan, Nikku; Burrows, Adam; Currie, Thayne

2011-08-01

We have generated an extensive new suite of massive giant planet atmosphere models and used it to obtain fits to photometric data for the planets HR 8799b, c, and d. We consider a wide range of cloudy and cloud-free models. The cloudy models incorporate different geometrical and optical thicknesses, modal particle sizes, and metallicities. For each planet and set of cloud parameters, we explore grids in gravity and effective temperature, with which we determine constraints on the planet's mass and age. Our new models yield statistically significant fits to the data, and conclusively confirm that the HR 8799 planets have much thicker clouds than those required to explain data for typical L and T dwarfs. Both models with (1) physically thick forsterite clouds and a 60 μm modal particle size and (2) clouds made of 1 μm sized pure iron droplets and 1% supersaturation fit the data. Current data are insufficient to accurately constrain the microscopic cloud properties, such as composition and particle size. The range of best-estimated masses for HR 8799b, HR 8799c, and HR 8799d conservatively span 2-12 MJ , 6-13 MJ , and 3-11 MJ , respectively, and imply coeval ages between ~10 and ~150 Myr, consistent with previously reported stellar ages. The best-fit temperatures and gravities are slightly lower than values obtained by Currie et al. using even thicker cloud models. Finally, we use these models to predict the near-to-mid-IR colors of soon-to-be imaged planets. Our models predict that planet-mass objects follow a locus in some near-to-mid-IR color-magnitude diagrams that is clearly separable from the standard L/T dwarf locus for field brown dwarfs.

Modelling of deep gaps created by giant planets in protoplanetary disks

NASA Astrophysics Data System (ADS)

Kanagawa, Kazuhiro D.; Tanaka, Hidekazu; Muto, Takayuki; Tanigawa, Takayuki

2017-12-01

A giant planet embedded in a protoplanetary disk creates a gap. This process is important for both theory and observation. Using results of a survey for a wide parameter range with two-dimensional hydrodynamic simulations, we constructed an empirical formula for the gap structure (i.e., the radial surface density distribution), which can reproduce the gap width and depth obtained by two-dimensional simulations. This formula enables us to judge whether an observed gap is likely to be caused by an embedded planet or not. The propagation of waves launched by the planet is closely connected to the gap structure. It makes the gap wider and shallower as compared with the case where an instantaneous wave damping is assumed. The hydrodynamic simulations show that the waves do not decay immediately at the launching point of waves, even when the planet is as massive as Jupiter. Based on the results of hydrodynamic simulations, we also obtained an empirical model of wave propagation and damping in cases of deep gaps. The one-dimensional gap model with our wave propagation model is able to reproduce the gap structures in hydrodynamic simulations well. In the case of a Jupiter-mass planet, we also found that the waves with a smaller wavenumber (e.g., m = 2) are excited and transport the angular momentum to a location far away from the planet. The wave with m = 2 is closely related with a secondary wave launched by a site opposite from the planet.

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

A common mass scaling for satellite systems of gaseous planets.

PubMed

Canup, Robin M; Ward, William R

2006-06-15

The Solar System's outer planets that contain hydrogen gas all host systems of multiple moons, which notably each contain a similar fraction of their respective planet's mass (approximately 10(-4)). This mass fraction is two to three orders of magnitude smaller than that of the largest satellites of the solid planets (such as the Earth's Moon), and its common value for gas planets has been puzzling. Here we model satellite growth and loss as a forming giant planet accumulates gas and rock-ice solids from solar orbit. We find that the mass fraction of its satellite system is regulated to approximately 10(-4) by a balance of two competing processes: the supply of inflowing material to the satellites, and satellite loss through orbital decay driven by the gas. We show that the overall properties of the satellite systems of Jupiter, Saturn and Uranus arise naturally, and suggest that similar processes could limit the largest moons of extrasolar Jupiter-mass planets to Moon-to-Mars size.

Carbon-rich Giant Planets: Atmospheric Chemistry, Thermal Inversions, Spectra, and Formation Conditions

NASA Astrophysics Data System (ADS)

Madhusudhan, Nikku; Mousis, Olivier; Johnson, Torrence V.; Lunine, Jonathan I.

2011-12-01

The recent inference of a carbon-rich atmosphere, with C/O >= 1, in the hot Jupiter WASP-12b motivates the exotic new class of carbon-rich planets (CRPs). We report a detailed study of the atmospheric chemistry and spectroscopic signatures of carbon-rich giant (CRG) planets, the possibility of thermal inversions in their atmospheres, the compositions of icy planetesimals required for their formation via core accretion, and the apportionment of ices, rock, and volatiles in their envelopes. Our results show that CRG atmospheres probe a unique region in composition space, especially at high temperature (T). For atmospheres with C/O >= 1, and T >~ 1400 K in the observable atmosphere, most of the oxygen is bound up in CO, while H2O is depleted and CH4 is enhanced by up to two or three orders of magnitude each, compared to equilibrium compositions with solar abundances (C/O = 0.54). These differences in the spectroscopically dominant species for the different C/O ratios cause equally distinct observable signatures in the spectra. As such, highly irradiated transiting giant exoplanets form ideal candidates to estimate atmospheric C/O ratios and to search for CRPs. We also find that the C/O ratio strongly affects the abundances of TiO and VO, which have been suggested to cause thermal inversions in highly irradiated hot Jupiter atmospheres. A C/O = 1 yields TiO and VO abundances of ~100 times lower than those obtained with equilibrium chemistry assuming solar abundances, at P ~ 1 bar. Such a depletion is adequate to rule out thermal inversions due to TiO/VO even in the most highly irradiated hot Jupiters, such as WASP-12b. We estimate the compositions of the protoplanetary disk, the planetesimals, and the envelope of WASP-12b, and the mass of ices dissolved in the envelope, based on the observed atmospheric abundances. Adopting stellar abundances (C/O = 0.44) for the primordial disk composition and low-temperature formation conditions (T <~ 30 K) for WASP-12b lead to a C

The International Deep Planet Survey. II. The frequency of directly imaged giant exoplanets with stellar mass

NASA Astrophysics Data System (ADS)

Galicher, R.; Marois, C.; Macintosh, B.; Zuckerman, B.; Barman, T.; Konopacky, Q.; Song, I.; Patience, J.; Lafrenière, D.; Doyon, R.; Nielsen, E. L.

2016-10-01

Context. Radial velocity and transit methods are effective for the study of short orbital period exoplanets but they hardly probe objects at large separations for which direct imaging can be used. Aims: We carried out the international deep planet survey of 292 young nearby stars to search for giant exoplanets and determine their frequency. Methods: We developed a pipeline for a uniform processing of all the data that we have recorded with NIRC2/Keck II, NIRI/Gemini North, NICI/Gemini South, and NACO/VLT for 14 yr. The pipeline first applies cosmetic corrections and then reduces the speckle intensity to enhance the contrast in the images. Results: The main result of the international deep planet survey is the discovery of the HR 8799 exoplanets. We also detected 59 visual multiple systems including 16 new binary stars and 2 new triple stellar systems, as well as 2279 point-like sources. We used Monte Carlo simulations and the Bayesian theorem to determine that 1.05+2.80-0.70% of stars harbor at least one giant planet between 0.5 and 14 MJ and between 20 and 300 AU. This result is obtained assuming uniform distributions of planet masses and semi-major axes. If we consider power law distributions as measured for close-in planets instead, the derived frequency is 2.30+5.95-1.55%, recalling the strong impact of assumptions on Monte Carlo output distributions. We also find no evidence that the derived frequency depends on the mass of the hosting star, whereas it does for close-in planets. Conclusions: The international deep planet survey provides a database of confirmed background sources that may be useful for other exoplanet direct imaging surveys. It also puts new constraints on the number of stars with at least one giant planet reducing by a factor of two the frequencies derived by almost all previous works. Tables 11-15 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http

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.

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.

Planet Formation

NASA Astrophysics Data System (ADS)

Podolak, Morris

2018-04-01

the planetary embryo can attract gas from the surrounding disk and grow to be a gas giant. If the disk dissipates before the process is complete, the result will be an object like Uranus or Neptune, which has a small, but significant, complement of hydrogen and helium. The main question is whether the protoplanetary core can grow large enough before the disk dissipates. A second scenario is the disk instability (DI) scenario. This scenario posits that the disk itself is unstable and tends to develop regions of higher than normal density. Such regions collapse under their own gravity to form Jupiter-mass protoplanets. In the DI scenario a Jupiter-mass clump of gas can form—in several hundred years which will eventually contract into a gas giant planet. The difficulty here is to bring the disk to a condition where such instabilities will form. Now that we have discovered nearly 3000 planetary systems, there will be numerous examples against which to test these scenarios.

Migration of giant planets in a time-dependent planetesimal accretion disc

NASA Astrophysics Data System (ADS)

Del Popolo, A.; Ekşi, K. Y.

2002-05-01

In this paper we develop further the model for the migration of planets introduced in Del Popolo et al. We first model the protoplanetary nebula as a time-dependent accretion disc, and find self-similar solutions to the equations of the accretion disc that give us explicit formulae for the spatial structure and the temporal evolution of the nebula. These equations are then used to obtain the migration rate of the planet in the planetesimal disc, and to study how the migration rate depends on the disc mass, on its time evolution and on some values of the dimensionless viscosity parameter α . We find that planets that are embedded in planetesimal discs, having total mass of 10-4 -0.1Msolar , can migrate inward a large distance for low values of α (e.g., α ~=10-3 -10-2 ) and/or large disc mass, and can survive only if the inner disc is truncated or because of tidal interaction with the star. Orbits with larger a are obtained for smaller values of the disc mass and/or for larger values of α . This model may explain several orbital features of the recently discovered giant planets orbiting nearby stars.

Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn's rapid gas accretion

NASA Astrophysics Data System (ADS)

Raymond, Sean N.; Izidoro, Andre

2017-11-01

There is a long-standing debate regarding the origin of the terrestrial planets' water as well as the hydrated C-type asteroids. Here we show that the inner Solar System's water is a simple byproduct of the giant planets' formation. Giant planet cores accrete gas slowly until the conditions are met for a rapid phase of runaway growth. As a gas giant's mass rapidly increases, the orbits of nearby planetesimals are destabilized and gravitationally scattered in all directions. Under the action of aerodynamic gas drag, a fraction of scattered planetesimals are deposited onto stable orbits interior to Jupiter's. This process is effective in populating the outer main belt with C-type asteroids that originated from a broad (5-20 AU-wide) region of the disk. As the disk starts to dissipate, scattered planetesimals reach sufficiently eccentric orbits to cross the terrestrial planet region and deliver water to the growing Earth. This mechanism does not depend strongly on the giant planets' orbital migration history and is generic: whenever a giant planet forms it invariably pollutes its inner planetary system with water-rich bodies.

REVISITING THE MICROLENSING EVENT OGLE 2012-BLG-0026: A SOLAR MASS STAR WITH TWO COLD GIANT PLANETS

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

Beaulieu, J.-P.; Batista, V.; Marquette, J.-B., E-mail: beaulieu@iap.fr, E-mail: batista@iap.fr, E-mail: marquett@iap.fr

2016-06-20

Two cold gas giant planets orbiting a G-type main-sequence star in the galactic disk were previously discovered in the high-magnification microlensing event OGLE-2012-BLG-0026. Here, we present revised host star flux measurements and a refined model for the two-planet system using additional light curve data. We performed high angular resolution adaptive optics imaging with the Keck and Subaru telescopes at two epochs while the source star was still amplified. We detected the lens flux, H = 16.39 ± 0.08. The lens, a disk star, is brighter than predicted from the modeling in the original study. We revisited the light curve modelingmore » using additional photometric data from the B and C telescope in New Zealand and CTIO 1.3 m H -band light curve. We then include the Keck and Subaru adaptive optic observation constraints. The system is composed of a ∼4–9 Gyr lens star of M {sub lens} = 1.06 ± 0.05 M {sub ⊙} at a distance of D {sub lens} = 4.0 ± 0.3 kpc, orbited by two giant planets of 0.145 ± 0.008 M {sub Jup} and 0.86 ± 0.06 M {sub Jup}, with projected separations of 4.0 ± 0.5 au and 4.8 ± 0.7 au, respectively. Because the lens is brighter than the source star by 16 ± 8% in H, with no other blend within one arcsec, it will be possible to estimate its metallicity using subsequent IR spectroscopy with 8–10 m class telescopes. By adding a constraint on the metallicity it will be possible to refine the age of the system.« less

Inferring giant planets from ALMA millimeter continuum and line observations in (transition) disks

NASA Astrophysics Data System (ADS)

Facchini, S.; Pinilla, P.; van Dishoeck, E. F.; de Juan Ovelar, M.

2018-05-01

Context. Radial gaps or cavities in the continuum emission in the IR-mm wavelength range are potential signatures of protoplanets embedded in their natal protoplanetary disk are. Hitherto, models have relied on the combination of mm continuum observations and near-infrared scattered light images to put constraints on the properties of embedded planets. Atacama Large Millimeter/submillimeter Array (ALMA) observations are now probing spatially resolved rotational line emission of CO and other chemical species. These observations can provide complementary information on the mechanism carving the gaps in dust and additional constraints on the purported planet mass. Aims: We investigate whether the combination of ALMA continuum and CO line observations can constrain the presence and mass of planets embedded in protoplanetary disks. Methods: We post-processed azimuthally averaged 2D hydrodynamical simulations of planet-disk models, in which the dust densities and grain size distributions are computed with a dust evolution code that considers radial drift, fragmentation, and growth. The simulations explored various planet masses (1 MJ ≤ Mp ≤ 15 MJ) and turbulent parameters (10-4 ≤ α ≤ 10-3). The outputs were then post-processed with the thermochemical code DALI, accounting for the radially and vertically varying dust properties. We obtained the gas and dust temperature structures, chemical abundances, and synthetic emission maps of both thermal continuum and CO rotational lines. This is the first study combining hydrodynamical simulations, dust evolution, full radiative transfer, and chemistry to predict gas emission of disks hosting massive planets. Results: All radial intensity profiles of 12CO, 13CO, and C18O show a gap at the planet location. The ratio between the location of the gap as seen in CO and the peak in the mm continuum at the pressure maximum outside the orbit of the planet shows a clear dependence on planet mass and is independent of disk

Opportunities for Laboratory Opacity Chemistry Studies to Facilitate Characterization of Young Giant Planets and Brown Dwarfs

NASA Technical Reports Server (NTRS)

Marley, Mark; Freedman, Richard S.

2015-01-01

The thermal emission spectra of young giant planets is shaped by the opacity of atoms and molecules residing in their atmospheres. While great strides have been made in improving the opacities of important molecules, particularly NH3 and CH4, at high temperatures, much more work is needed to understand the opacity and chemistry of atomic Na and K. The highly pressure broadened fundamental band of Na and K in the optical stretches into the near-infrared, strongly influencing the shape of the Y and K spectral bands. Since young giant planets are bright in these bands it is important to understand the influences on the spectral shape. Discerning gravity and atmospheric composition is difficult, if not impossible, without both good atomic opacities as well as an excellent understanding of the relevant atmospheric chemistry. Since Na and K condense at temperatures near 500 to 600 K, the chemistry of the condensation process must be well understood as well, particularly any disequilibrium chemical pathways. Comparisons of the current generation of sophisticated atmospheric models and available data, however, reveal important shortcomings in the models. We will review the current state of observations and theory of young giant planets and will discuss these and other specific examples where improved laboratory measurements for alkali compounds have the potential of substantially improving our understanding of these atmospheres.

OGLE-2017-BLG-1522: A Giant Planet around a Brown Dwarf Located in the Galactic Bulge

NASA Astrophysics Data System (ADS)

Jung, Y. K.; Udalski, A.; Gould, A.; Ryu, Y.-H.; Yee, J. C.; and; Han, C.; Albrow, M. D.; Lee, C.-U.; Kim, S.-L.; Hwang, K.-H.; Chung, S.-J.; Shin, I.-G.; Zhu, W.; Cha, S.-M.; Kim, D.-J.; Lee, Y.; Park, B.-G.; Lee, D.-J.; Kim, H.-W.; Pogge, R. W.; The KMTNet Collaboration; Szymański, M. K.; Mróz, P.; Poleski, R.; Skowron, J.; Pietrukowicz, P.; Soszyński, I.; Kozłowski, S.; Ulaczyk, K.; Pawlak, M.; Rybicki, K.; The OGLE Collaboration

2018-05-01

We report the discovery of a giant planet in the OGLE-2017-BLG-1522 microlensing event. The planetary perturbations were clearly identified by high-cadence survey experiments despite the relatively short event timescale of t E ∼ 7.5 days. The Einstein radius is unusually small, θ E = 0.065 mas, implying that the lens system either has very low mass or lies much closer to the microlensed source than the Sun, or both. A Bayesian analysis yields component masses ({M}host},{M}planet})=({46}-25+79,{0.75}-0.40+1.26) {M}{{J}} and source-lens distance {D}LS}={0.99}-0.54+0.91 {kpc}, implying that this is a brown-dwarf/Jupiter system that probably lies in the Galactic bulge, a location that is also consistent with the relatively low lens-source relative proper motion μ = 3.2 ± 0.5 mas yr‑1. The projected companion-host separation is {0.59}-0.11+0.12 {au}, indicating that the planet is placed beyond the snow line of the host, i.e., a sl ∼ 0.12 au. Planet formation scenarios combined with the small companion-host mass ratio q ∼ 0.016 and separation suggest that the companion could be the first discovery of a giant planet that formed in a protoplanetary disk around a brown-dwarf host.

ECCENTRIC JUPITERS VIA DISK–PLANET INTERACTIONS

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

Duffell, Paul C.; Chiang, Eugene, E-mail: duffell@berkeley.edu, E-mail: echiang@astro.berkeley.edu

2015-10-20

Numerical hydrodynamics calculations are performed to determine the conditions under which giant planet eccentricities can be excited by parent gas disks. Unlike in other studies, Jupiter-mass planets are found to have their eccentricities amplified—provided their orbits start off as eccentric. We disentangle the web of co-rotation, co-orbital, and external resonances to show that this finite-amplitude instability is consistent with that predicted analytically. Ellipticities can grow until they reach of order of the disk's aspect ratio, beyond which the external Lindblad resonances that excite eccentricity are weakened by the planet's increasingly supersonic epicyclic motion. Forcing the planet to still larger eccentricitiesmore » causes catastrophic eccentricity damping as the planet collides into gap walls. For standard parameters, the range of eccentricities for instability is modest; the threshold eccentricity for growth (∼0.04) is not much smaller than the final eccentricity to which orbits grow (∼0.07). If this threshold eccentricity can be lowered (perhaps by non-barotropic effects), and if the eccentricity driving documented here survives in 3D, it may robustly explain the low-to-moderate eccentricities ≲0.1 exhibited by many giant planets (including Jupiter and Saturn), especially those without planetary or stellar companions.« less

The Radial Velocity Variability of the K-giant γ Draconis: Stellar Variability Masquerading as a Planet

NASA Astrophysics Data System (ADS)

Hatzes, A. P.; Endl, M.; Cochran, W. D.; MacQueen, P. J.; Han, I.; Lee, B.-C.; Kim, K.-M.; Mkrtichian, D.; Döllinger, M.; Hartmann, M.; Karjalainen, M.; Dreizler, S.

2018-03-01

We present precise stellar radial velocity (RV) measurements of γ Dra taken from 2003 to 2017. The data from 2003 to 2011 show coherent, long-lived variations with a period of 702 days. These variations are consistent with the presence of a planetary companion having m sin i = 10.7 M Jup whose orbital properties are typical for giant planets found around evolved stars. An analysis of the Hipparcos photometry, Ca II S-index measurements, and measurements of the spectral line shapes during this time show no variations with the RV of the planet, which seems to “confirm” the presence of the planet. However, RV measurements taken from 2011–2017 seem to refute this. From 2011–2013, the RV variations virtually disappear, only to return in 2014 but with a noticeable phase shift. The total RV variations are consistent either with amplitude variations on timescales of ≈10.6 year, or the beating effect between two periods of 666 and 801 days. It seems unlikely that both these signals stem from a two-planet system. A simple dynamical analysis indicates that there is only a 1%–2% chance that the two-planet system is stable. Rather, we suggest that this multi-periodic behavior may represent a new form of stellar variability, possibly related to oscillatory convective modes. If such intrinsic stellar variability is common around K giant stars and is attributed to planetary companions, then the planet occurrence rate among these stars may be significantly lower than thought.

The Spiral Wave Instability Induced by a Giant Planet. I. Particle Stirring in the Inner Regions of Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Bae, Jaehan; Nelson, Richard P.; Hartmann, Lee

2016-12-01

We have recently shown that spiral density waves propagating in accretion disks can undergo a parametric instability by resonantly coupling with and transferring energy into pairs of inertial waves (or inertial-gravity waves when buoyancy is important). In this paper, we perform inviscid three-dimensional global hydrodynamic simulations to examine the growth and consequence of this instability operating on the spiral waves driven by a Jupiter-mass planet in a protoplanetary disk. We find that the spiral waves are destabilized via the spiral wave instability (SWI), generating hydrodynamic turbulence and sustained radially alternating vertical flows that appear to be associated with long wavelength inertial modes. In the interval 0.3 {R}{{p}}≤slant R≤slant 0.7{R}{{p}}, where R p denotes the semimajor axis of the planetary orbit (assumed to be 5 au), the estimated vertical diffusion rate associated with the turbulence is characterized by {α }{diff}∼ (0.2{--}1.2)× {10}-2. For the disk model considered here, the diffusion rate is such that particles with sizes up to several centimeters are vertically mixed within the first pressure scale height. This suggests that the instability of spiral waves launched by a giant planet can significantly disperse solid particles and trace chemical species from the midplane. In planet formation models where the continuous local production of chondrules/pebbles occurs over Myr timescales to provide a feedstock for pebble accretion onto these bodies, this stirring of solid particles may add a time constraint: planetary embryos and large asteroids have to form before a gas giant forms in the outer disk, otherwise the SWI will significantly decrease the chondrule/pebble accretion efficiency.

Making the Moon from a fast-spinning Earth: a giant impact followed by resonant despinning.

PubMed

Ćuk, Matija; Stewart, Sarah T

2012-11-23

A common origin for the Moon and Earth is required by their identical isotopic composition. However, simulations of the current giant impact hypothesis for Moon formation find that most lunar material originated from the impactor, which should have had a different isotopic signature. Previous Moon-formation studies assumed that the angular momentum after the impact was similar to that of the present day; however, Earth-mass planets are expected to have higher spin rates at the end of accretion. Here, we show that typical last giant impacts onto a fast-spinning proto-Earth can produce a Moon-forming disk derived primarily from Earth's mantle. Furthermore, we find that a faster-spinning early Earth-Moon system can lose angular momentum and reach the present state through an orbital resonance between the Sun and Moon.

The ODINUS Mission Concept: a Mission to the Ice Giant Planets

NASA Astrophysics Data System (ADS)

Turrini, Diego; Politi, Romolo; Peron, Roberto; Grassi, Davide; Plainaki, Christina; Barbieri, Mauro; Massimo Lucchesi, David; Magni, Gianfranco; Altieri, Francesca; Cottini, Valeria; Gorius, Nicolas; Gaulme, Patrick; Schmider, François-Xavier; Adriani, Alberto; Piccioni, Giuseppe

2014-05-01

We present the scientific case and the mission concept for the comparative exploration of the ice giant planets Uranus and Neptune and their satellites with a pair of twin spacecraft: ODINUS (Origins, Dynamics and Interiors of Neptunian and Uranian Systems). The ODINUS proposal was submitted in response to the call for white papers for the definition of the themes of the L2 and L3 mission in the framework of the ESA Cosmic Vision 2015-2025 program. The goal of ODINUS is the advancement of our understanding of the ancient past of the Solar System and, more generally, of how planetary systems form and evolve. The mission concept is focused on providing elements to answer to the scientific themes of the Cosmic Vision 2015-2025 program: What are the conditions for planetary formation and the emergency of life? How does the Solar System work? What are the fundamental physical laws of the Universe? In order to achieve its goals, the ODINUS mission concept proposed the use of two twin spacecraft to be put in orbit around Uranus and Neptune respectively, with selected flybys of their satellites. The proposed measurements aim to study the atmospheres and magnetospheres of the planets, the surfaces of the satellites, and the interior structure and composition of both satellites and planets. An important possibility for performing fundamental physics studies (among them tests of general relativity theory) is offered by the cruise phase. After the extremely positive evaluation of ESA Senior Survey Committee, who stated that 'the exploration of the icy giants appears to be a timely milestone, fully appropriate for an L class mission', we discuss strategies to comparatively study Uranus and Neptune with future international missions.

Detection of Extrasolar Planets by Transit Photometry

NASA Technical Reports Server (NTRS)

Borucki, William; Koch, David; Webster, Larry; Dunham, Edward; Witteborn, Fred; Jenkins, Jon; Caldwell, Douglas; Showen, Robert; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

A knowledge of other planetary systems that includes information on the number, size, mass, and spacing of the planets around a variety of star types is needed to deepen our understanding of planetary system formation and processes that give rise to their final configurations. Recent discoveries show that many planetary systems are quite different from the solar system in that they often possess giant planets in short period orbits. The inferred evolution of these planets and their orbital characteristics imply the absence of Earth-like planets near the habitable zone. Information on the properties of the giant-inner planets is now being obtained by both the Doppler velocity and the transit photometry techniques. The combination of the two techniques provides the mass, size, and density of the planets. For the planet orbiting star HD209458, transit photometry provided the first independent confirmation and measurement of the diameter of an extrasolar planet. The observations indicate a planet 1.27 the diameter of Jupiter with 0.63 of its mass (Charbonneau et al. 1999). The results are in excellent agreement with the theory of planetary atmospheres for a planet of the indicated mass and distance from a solar-like star. The observation of the November 23, 1999 transit of that planet made by the Ames Vulcan photometer at Lick Observatory is presented. In the future, the combination of the two techniques will greatly increase the number of discoveries and the richness of the science yield. Small rocky planets at orbital distances from 0.9 to 1.2 AU are more likely to harbor life than the gas giant planets that are now being discovered. However, new technology is needed to find smaller, Earth-like planets, which are about three hundred times less massive than Jupiter-like planets. The Kepler project is a space craft mission designed to discover hundreds of Earth-size planets in and near the habitable zone around a wide variety of stars. To demonstrate that the

Giant planets and their satellites: What are the relationships between their properties and how they formed

NASA Technical Reports Server (NTRS)

Stevenson, David J.

1991-01-01

The following subject areas are covered: (1) the mass distribution; (2) interior models; (3) atmospheric compositions and their implications; (4) heat flows and their implications; (5) satellite systems; (6) temperatures in the solar nebula; and (7) giant planet formation.

DEUTERIUM BURNING IN MASSIVE GIANT PLANETS AND LOW-MASS BROWN DWARFS FORMED BY CORE-NUCLEATED ACCRETION

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

Bodenheimer, Peter; D'Angelo, Gennaro; Lissauer, Jack J.

Using detailed numerical simulations, we study the formation of bodies near the deuterium-burning limit according to the core-nucleated giant planet accretion scenario. The objects, with heavy-element cores in the range 5-30 M{sub Circled-Plus }, are assumed to accrete gas up to final masses of 10-15 Jupiter masses (M{sub Jup}). After the formation process, which lasts 1-5 Myr and which ends with a ''cold-start'', low-entropy configuration, the bodies evolve at constant mass up to an age of several Gyr. Deuterium burning via proton capture is included in the calculation, and we determined the mass, M{sub 50}, above which more than 50%more » of the initial deuterium is burned. This often-quoted borderline between giant planets and brown dwarfs is found to depend only slightly on parameters, such as core mass, stellar mass, formation location, solid surface density in the protoplanetary disk, disk viscosity, and dust opacity. The values for M{sub 50} fall in the range 11.6-13.6 M{sub Jup}, in agreement with previous determinations that do not take the formation process into account. For a given opacity law during the formation process, objects with higher core masses form more quickly. The result is higher entropy in the envelope at the completion of accretion, yielding lower values of M{sub 50}. For masses above M{sub 50}, during the deuterium-burning phase, objects expand and increase in luminosity by one to three orders of magnitude. Evolutionary tracks in the luminosity versus time diagram are compared with the observed position of the companion to Beta Pictoris.« less

Short-term collisional evolution of a disc perturbed by a giant-planet embryo

NASA Astrophysics Data System (ADS)

Charnoz, S.; Thébault, P.; Brahic, A.

2001-07-01

A simple numerical model has been developed to study the evolution of a disc of planetesimals under mutual inelastic collisions in the potential field of a central body and of an embedded giant-planet embryo. Masses for the latter range from 0.5 to 300 Earth masses. A mass of 15 Moplus is typical of the solid-core model for the formation of giant planets. The initially cold disc consists of a few thousand particles. Those initially present between one and three Hill radii from the perturber's orbit are transferred to very eccentric orbits causing violent collisions throughout the disc. The perturbation propagates far from the perturber, like a heat transfer: a 15 Moplus perturber orbiting at 5.2 a.u. heats up the disc from 2.3 to at least 11 a.u. from the central body in a few 105 to 106 years. Relative velocities are typically increased by a factor of 10 to 100. The extent of the heated region increases with the protoplanet's mass while the propagation timescale decreases. The resulting radial mixing has potential applications for the origin of the Asteroid Belt, in particular for the radial distribution of the asteroid's spectroscopic families.

Transiting circumbinary planets Kepler-34 b and Kepler-35 b

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

Welsh, William F.; Orosz, Jerome A.; Carter, Joshua A.

Most Sun-like stars in the Galaxy reside in gravitationally-bound pairs of stars called 'binary stars'. While long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of Kepler-16. Incontrovertible evidence was provided by the miniature eclipses ('transits') of the stars by the planet. However, questions remain about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we present two additional transiting circumbinary planets, Kepler-34 and Kepler-35. Each is a low-density gas giant planet on an orbit closely aligned with that of its parentmore » stars. Kepler-34 orbits two Sun-like stars every 289 days, while Kepler-35 orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. Due to the orbital motion of the stars, the planets experience large multi-periodic variations in incident stellar radiation. The observed rate of circumbinary planets implies > ~1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.« less

ON THE EFFECT OF GIANT PLANETS ON THE SCATTERING OF PARENT BODIES OF IRON METEORITE FROM THE TERRESTRIAL PLANET REGION INTO THE ASTEROID BELT: A CONCEPT STUDY

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

Haghighipour, Nader; Scott, Edward R. D., E-mail: nader@ifa.hawaii.edu

2012-04-20

In their model for the origin of the parent bodies of iron meteorites, Bottke et al. proposed differentiated planetesimals, formed in 1-2 AU during the first 1.5 Myr, as the parent bodies, and suggested that these objects and their fragments were scattered into the asteroid belt as a result of interactions with planetary embryos. Although viable, this model does not include the effect of a giant planet that might have existed or been growing in the outer regions. We present the results of a concept study where we have examined the effect of a planetary body in the orbit ofmore » Jupiter on the early scattering of planetesimals from the terrestrial region into the asteroid belt. We integrated the orbits of a large battery of planetesimals in a disk of planetary embryos and studied their evolutions for different values of the mass of the planet. Results indicate that when the mass of the planet is smaller than 10 M{sub Circled-Plus }, its effects on the interactions among planetesimals and planetary embryos are negligible. However, when the planet mass is between 10 and 50 M{sub Circled-Plus }, simulations point to a transitional regime with {approx}50 M{sub Circled-Plus} being the value for which the perturbing effect of the planet can no longer be ignored. Simulations also show that further increase of the mass of the planet strongly reduces the efficiency of the scattering of planetesimals from the terrestrial planet region into the asteroid belt. We present the results of our simulations and discuss their possible implications for the time of giant planet formation.« less

Large eccentricity, low mutual inclination: the three-dimensional architecture of a hierarchical system of giant planets

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

Dawson, Rebekah I.; Clubb, Kelsey I.; Johnson, John Asher

2014-08-20

We establish the three-dimensional architecture of the Kepler-419 (previously KOI-1474) system to be eccentric yet with a low mutual inclination. Kepler-419b is a warm Jupiter at semi-major axis a=0.370{sub −0.006}{sup +0.007} AU with a large eccentricity (e = 0.85{sub −0.07}{sup +0.08}) measured via the 'photoeccentric effect'. It exhibits transit timing variations (TTVs) induced by the non-transiting Kepler-419c, which we uniquely constrain to be a moderately eccentric (e = 0.184 ± 0.002), hierarchically separated (a = 1.68 ± 0.03 AU) giant planet (7.3 ± 0.4 M {sub Jup}). We combine 16 quarters of Kepler photometry, radial-velocity (RV) measurements from the HIghmore » Resolution Echelle Spectrometer on Keck, and improved stellar parameters that we derive from spectroscopy and asteroseismology. From the RVs, we measure the mass of the inner planet to be 2.5 ± 0.3 M {sub Jup} and confirm its photometrically measured eccentricity, refining the value to e = 0.83 ± 0.01. The RV acceleration is consistent with the properties of the outer planet derived from TTVs. We find that despite their sizable eccentricities, the planets are coplanar to within 9{sub −6}{sup +8} degrees, and therefore the inner planet's large eccentricity and close-in orbit are unlikely to be the result of Kozai migration. Moreover, even over many secular cycles, the inner planet's periapse is most likely never small enough for tidal circularization. Finally, we present and measure a transit time and impact parameter from four simultaneous ground-based light curves from 1 m class telescopes, demonstrating the feasibility of ground-based follow-up of Kepler giant planets exhibiting large TTVs.« less

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.

Volatile accretion history of the terrestrial planets and dynamic implications.

PubMed

Albarède, Francis

2009-10-29

Accretion left the terrestrial planets depleted in volatile components. Here I examine evidence for the hypothesis that the Moon and the Earth were essentially dry immediately after the formation of the Moon-by a giant impact on the proto-Earth-and only much later gained volatiles through accretion of wet material delivered from beyond the asteroid belt. This view is supported by U-Pb and I-Xe chronologies, which show that water delivery peaked approximately 100 million years after the isolation of the Solar System. Introduction of water into the terrestrial mantle triggered plate tectonics, which may have been crucial for the emergence of life. This mechanism may also have worked for the young Venus, but seems to have failed for Mars.

Kepler-91b: a planet at the end of its life. Planet and giant host star properties via light-curve variations

NASA Astrophysics Data System (ADS)

Lillo-Box, J.; Barrado, D.; Moya, A.; Montesinos, B.; Montalbán, J.; Bayo, A.; Barbieri, M.; Régulo, C.; Mancini, L.; Bouy, H.; Henning, T.

2014-02-01

Context. The evolution of planetary systems is intimately linked to the evolution of their host stars. Our understanding of the whole planetary evolution process is based on the wide planet diversity observed so far. Only a few tens of planets have been discovered orbiting stars ascending the red giant branch. Although several theories have been proposed, the question of how planets die remains open owing to the small number statistics, making it clear that the sample of planets around post-main sequence stars needs to be enlarged. Aims: In this work we study the giant star Kepler-91 (KOI-2133) in order to determine the nature of a transiting companion. This system was detected by the Kepler Space Telescope, which identified small dims in its light curve with a period of 6.246580 ± 0.000082 days. However, its planetary confirmation is needed due to the large pixel size of the Kepler camera, which can hide other stellar configurations able to mimic planet-like transit events. Methods: We analysed Kepler photometry to 1) re-calculate transit parameters; 2) study the light-curve modulations; and 3) to perform an asteroseismic analysis (accurate stellar parameter determination) by identifying solar-like oscillations on the periodogram. We also used a high-resolution and high signal-to-noise ratio spectrum obtained with the Calar Alto Fiber-fed Échelle spectrograph (CAFE) to measure stellar properties. Additionally, false-positive scenarios were rejected by obtaining high-resolution images with the AstraLux lucky imaging camera on the 2.2 m telescope at the Calar Alto Observatory. Results: We confirm the planetary nature of the object transiting the star Kepler-91 by deriving a mass of Mp=0.88+0.17-0.33 MJup and a planetary radius of Rp=1.384+0.011-0.054 RJup. Asteroseismic analysis produces a stellar radius of R⋆ = 6.30 ± 0.16 R⊙ and a mass of M⋆ = 1.31 ± 0.10 M⊙. We find that its eccentric orbit (e=0.066+0.013-0.017) is just 1.32+0.07-0.22 R⋆ away from

The Orbital and Planetary Phase Variations of Jupiter-sized Planets: Characterizing Present and Future Giants

NASA Astrophysics Data System (ADS)

Mayorga, Laura C.; Jackiewicz, Jason; Rages, Kathy; West, Robert; Knowles, Ben; Lewis, Nikole K.; Marley, Mark S.

2018-01-01

Knowledge of how the brightness and color of a planet varies with viewing angle is essential for the design of future direct imaging missions and deriving constraints on atmospheric properties. However, measuring the phase curves for the solar system gas giants is impossible from the ground. Using data Cassini/ISS obtained during its flyby of Jupiter, I measured Jupiter's phase curve in six bands spanning 400-1000 nm. I found that Jupiter's brightness is less than that of a Lambertian scatterer and that its color varies more with phase angle than predicted by theoretical models. For hot Jupiters, the light from the planet cannot be spatially isolated from that of the star. As a result, determining the planetary phase curve requires removing the phase-dependent contributions from the host star. I consider the effect of varying the stellar model and present a parameterization of the Doppler beaming amplitude that depends upon the planetary mass, orbital period, and the stellar temperature. I consider the detectability of Doppler beaming amplitudes with data from TESS and find that TESS will be less sensitive to this signal than Kepler. This work was supported by the National Science Foundation Graduate Research Fellowship Program and the New Mexico Higher Education Department Graduate Scholarship Program.

Detection of planet candidates around K giants. HD 40956, HD 111591, and HD 113996

NASA Astrophysics Data System (ADS)

Jeong, G.; Lee, B.-C.; Han, I.; Omiya, M.; Izumiura, H.; Sato, B.; Harakawa, H.; Kambe, E.; Mkrtichian, D.

2018-02-01

Aims: The purpose of this paper is to detect and investigate the nature of long-term radial velocity (RV) variations of K-type giants and to confirm planetary companions around the stars. Methods: We have conducted two planet search programs by precise RV measurement using the 1.8 m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) and the 1.88 m telescope at Okayama Astrophysical Observatory (OAO). The BOAO program searches for planets around 55 early K giants. The OAO program is looking for 190 G-K type giants. Results: In this paper, we report the detection of long-period RV variations of three K giant stars, HD 40956, HD 111591, and HD 113996. We investigated the cause of the observed RV variations and conclude the substellar companions are most likely the cause of the RV variations. The orbital analyses yield P = 578.6 ± 3.3 d, m sin i = 2.7 ± 0.6 MJ, a = 1.4 ± 0.1 AU for HD 40956; P = 1056.4 ± 14.3 d, m sin i = 4.4 ± 0.4 MJ, a = 2.5 ± 0.1 AU for HD 111591; P = 610.2 ± 3.8 d, m sin i = 6.3 ± 1.0 MJ, a = 1.6 ± 0.1 AU for HD 113996. Based on observations made with the BOES at BOAO in Korea and HIDES at OAO in Japan.Tables 3-5 are only 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/610/A3

A Search for Refraction in the Kepler Gas Giant Data Set

NASA Astrophysics Data System (ADS)

Sheets, Holly; Jacob, Laurent; Cowan, Nicolas; Deming, Drake

2018-01-01

I will present the results of the first systematic search for refraction in the atmospheres of giant planets in the Kepler data set. We used the approximations of Sidis and Sari (ApJ, 2010, 720, 904S) to select the best candidates from the Kepler planet catalog for the search. We set limits on the strength of the effect, and I will relate these limits to other, more recent modeling methods.

Giant Transiting Planets Observations GITPO

NASA Astrophysics Data System (ADS)

Afonso, C.; Henning, Th.; Weldrake, D.; Mazeh, T.; Dreizler, S.

The search for extrasolar planets is nowadays one of the most promising science drivers in Astronomy. The radial velocity technique proved to be successful in planet hunting, harvesting more than a hundred planets to date. In these last recent years, the transit method has come to fruition, with the detection of seven Jupiter-mass extrasolar transiting planets in close-in orbits ({ AU). Currently, the radius of planets can only be determined from transiting planets, representing the principal motivation and strength of this technique. The MPIA is presently building the Large Area Imager (LAIWO) for the 1m telescope in the Wise Observatory, Israel. LAIWO will have a field of view of one square degree. An intensive search for extra-solar planets will be performed with the 1m Wise telescope, together with the 1.2m MONET telescope in Texas. We will monitor three fields at a given time during three years and more than 200 nights per year. We expect several dozens of extra-solar planets.

Transition disks: four candidates for ongoing giant planet formation in Ophiuchus

NASA Astrophysics Data System (ADS)

Orellana, M.; Cieza, L. A.; Schreiber, M. R.; Merín, B.; Brown, J. M.; Pellizza, L. J.; Romero, G. A.

2012-03-01

Among the large set of Spitzer-selected transitional disks that we have examined in the Ophiuchus molecular, four disks have been identified as (giant) planet-forming candidates based on the morphology of their spectral energy distributions (SEDs), their apparent lack of stellar companions, and evidence of accretion. Here we characterize the structures of these disks modeling their optical, infrared, and (sub)millimeter SEDs. We use the Monte Carlo radiative transfer package RADMC to construct a parametric model of the dust distribution in a flared disk with an inner cavity and calculate the temperature structure that is consistent with the density profile, when the disk is in thermal equilibrium with the irradiating star. For each object, we conducted a Bayesian exploration of the parameter space generating Monte Carlo Markov chains (MCMC) that allow the identification of the best-fit model parameters and to constrain their range of statistical confidence. Our calculations imply that evacuated cavities with radii ~2-8 AU are present that appear to have been carved by embedded giant planets. We found parameter values that are consistent with those previously given in the literature, indicating that there has been a mild degree of grain growth and dust settling, which deserves to be investigated with further modeling and follow-up observations. Resolved images with (sub)millimeter interferometers would be required to break some of the degeneracies of the models and more tightly constrain the physical properties of these fascinating disks.

Planetary radio astronomy: Earth, giant planets, and beyond

NASA Astrophysics Data System (ADS)

Rucker, H. O.; Panchenko, M.; Weber, C.

2014-11-01

The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.

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

Lunar and terrestrial planet formation in the Grand Tack scenario

PubMed Central

Jacobson, S. A.; Morbidelli, A.

2014-01-01

We present conclusions from a large number of N-body simulations of the giant impact phase of terrestrial planet formation. We focus on new results obtained from the recently proposed Grand Tack model, which couples the gas-driven migration of giant planets to the accretion of the terrestrial planets. The giant impact phase follows the oligarchic growth phase, which builds a bi-modal mass distribution within the disc of embryos and planetesimals. By varying the ratio of the total mass in the embryo population to the total mass in the planetesimal population and the mass of the individual embryos, we explore how different disc conditions control the final planets. The total mass ratio of embryos to planetesimals controls the timing of the last giant (Moon-forming) impact and its violence. The initial embryo mass sets the size of the lunar impactor and the growth rate of Mars. After comparing our simulated outcomes with the actual orbits of the terrestrial planets (angular momentum deficit, mass concentration) and taking into account independent geochemical constraints on the mass accreted by the Earth after the Moon-forming event and on the time scale for the growth of Mars, we conclude that the protoplanetary disc at the beginning of the giant impact phase must have had most of its mass in Mars-sized embryos and only a small fraction of the total disc mass in the planetesimal population. From this, we infer that the Moon-forming event occurred between approximately 60 and approximately 130 Myr after the formation of the first solids and was caused most likely by an object with a mass similar to that of Mars. PMID:25114304

Giant Transiting Planets Observations - GITPO

NASA Astrophysics Data System (ADS)

Afonso, C.

2006-08-01

The search for extrasolar planets is nowadays one of the most promising science drivers in Astronomy. The radial velocity technique proved to be successful in planet hunting, harvesting more than a hundred planets to date. In these last years, the transit method has come to fruition, with the detection of seven Jupiter-mass extrasolar transiting planets in close-in orbits (< 0.05 AU). Currently, the radius of planets can only be determined from transiting planets, representing the principal motivation and strength of this technique. The MPIA is presently building the Large Area Imager (LAIWO) for the 1m telescope in the Wise Observatory, Israel. LAIWO will have a field of view of one square degree. An intensive search for extra-solar planets will be performed with the 1m Wise telecope, together with the 1.2m MONET telescope in Texas. We will monitor three fields at a given time during three years and more than 200 nights per year. We expect several dozens of extra-solar planets.

Binary Black Hole Mergers from Planet-like Migrations.

PubMed

Gould; Rix

2000-03-20

If supermassive black holes (BHs) are generically present in galaxy centers, and if galaxies are built up through hierarchical merging, BH binaries are at least temporary features of most galactic bulges. Observations suggest, however, that binary BHs are rare, pointing toward a binary lifetime far shorter than the Hubble time. We show that, almost regardless of the detailed mechanism, all stellar dynamical processes are too slow in reducing the orbital separation once orbital velocities in the binary exceed the virial velocity of the system. We propose that a massive gas disk surrounding a BH binary can effect its merger rapidly, in a scenario analogous to the orbital decay of super-Jovian planets due to a proto-planetary disk. As in the case of planets, gas accretion onto the secondary (here a supermassive BH) is integrally connected with its inward migration. Such accretion would give rise to quasar activity. BH binary mergers could therefore be responsible for many or most quasars.

The physical characteristics of the surface of the satellites and rings of giant planets

NASA Astrophysics Data System (ADS)

Vidmachenko, A. P.; Morozhenko, O. V.

2017-10-01

The book gives the main results of the study of the optical characteristics of the field diffusely reflected radiation and physical characteristics of the surface of the satellites of giant planets and their rings. The publication is intended for teachers of higher educational institutions, students - graduate students and professionals who specialize in experimental physics and astrophysics and solar system surfaces.

Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants?

PubMed Central

Leitzinger, M.; Odert, P.; Kulikov, Yu.N.; Lammer, H.; Wuchterl, G.; Penz, T.; Guarcello, M.G.; Micela, G.; Khodachenko, M.L.; Weingrill, J.; Hanslmeier, A.; Biernat, H.K.; Schneider, J.

2011-01-01

We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. PMID:21969736

Could CoRoT-7b and Kepler-10b be remnants of evaporated gas or ice giants?

PubMed

Leitzinger, M; Odert, P; Kulikov, Yu N; Lammer, H; Wuchterl, G; Penz, T; Guarcello, M G; Micela, G; Khodachenko, M L; Weingrill, J; Hanslmeier, A; Biernat, H K; Schneider, J

2011-10-01

We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a "Hot Neptune" nor a "Hot Uranus"-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects.

The nature of the giant exomoon candidate Kepler-1625 b-i

NASA Astrophysics Data System (ADS)

Heller, René

2018-02-01

The recent announcement of a Neptune-sized exomoon candidate around the transiting Jupiter-sized object Kepler-1625 b could indicate the presence of a hitherto unknown kind of gas giant moon, if confirmed. Three transits of Kepler-1625 b have been observed, allowing estimates of the radii of both objects. Mass estimates, however, have not been backed up by radial velocity measurements of the host star. Here we investigate possible mass regimes of the transiting system that could produce the observed signatures and study them in the context of moon formation in the solar system, i.e., via impacts, capture, or in-situ accretion. The radius of Kepler-1625 b suggests it could be anything from a gas giant planet somewhat more massive than Saturn (0.4 MJup) to a brown dwarf (BD; up to 75 MJup) or even a very-low-mass star (VLMS; MJup ≈ 0.11 M⊙). The proposed companion would certainly have a planetary mass. Possible extreme scenarios range from a highly inflated Earth-mass gas satellite to an atmosphere-free water-rock companion of about 180 M⊕. Furthermore, the planet-moon dynamics during the transits suggest a total system mass of 17.6-12.6+19.2 MJup. A Neptune-mass exomoon around a giant planet or low-mass BD would not be compatible with the common mass scaling relation of the solar system moons about gas giants. The case of a mini-Neptune around a high-mass BD or a VLMS, however, would be located in a similar region of the satellite-to-host mass ratio diagram as Proxima b, the TRAPPIST-1 system, and LHS 1140 b. The capture of a Neptune-mass object around a 10 MJup planet during a close binary encounter is possible in principle. The ejected object, however, would have had to be a super-Earth object, raising further questions of how such a system could have formed. In summary, this exomoon candidate is barely compatible with established moon formation theories. If it can be validated as orbiting a super-Jovian planet, then it would pose an exquisite riddle for

Young Brown Dwarfs and Giant Planets as Companions to Weak-Line T Tauri Stars

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang; Frink, Sabine; Kohler, Rainer; Kunkel, Michael

Weak-line T Tauri stars, contrary to classical T Tauri stars, no longer possess massive circumstellar disks. In weak-line T Tauri stars, the circumstellar matter was either accreted onto the T Tauri star or has been redistributed. Disk instabilities in the outer disk might result in the formation of brown dwarfs and giant planets. Based on photometric and spectroscopic studies of ROSAT sources, we have selected an initial sample of 200 weak-line T Tauri stars in the Chamaeleon T association and the Scorpius-Centaurus OB association. In the course of follow-up observations, we identified visual and spectroscopic binary stars and excluded them from our final list, as the complex dynamics and gravitational interaction in binary systems might aggravate or even completely inhibit the formation of planets (depending on physical separation of the binary components and their mass ratio). The membership of individual stars to the associations was established from proper motion studies and radial velocity surveys. Our final sample consists of 70 single weak-line T Tauri stars. We have initiated a program to spatially resolve young brown dwarfs and young giant planets as companions to single weak-line T Tauri stars using adaptive optics at the ESO 3.6 m telescope and HST/NICMOS. In this poster we describe the observing strategy and present first results of our adaptive optics observations. An update on the program status can be found at http://www.astro.uiuc.edu/~brandner/text/bd/bd.html

Transiting circumbinary planets Kepler-34 b and Kepler-35 b.

PubMed

Welsh, William F; Orosz, Jerome A; Carter, Joshua A; Fabrycky, Daniel C; Ford, Eric B; Lissauer, Jack J; Prša, Andrej; Quinn, Samuel N; Ragozzine, Darin; Short, Donald R; Torres, Guillermo; Winn, Joshua N; Doyle, Laurance R; Barclay, Thomas; Batalha, Natalie; Bloemen, Steven; Brugamyer, Erik; Buchhave, Lars A; Caldwell, Caroline; Caldwell, Douglas A; Christiansen, Jessie L; Ciardi, David R; Cochran, William D; Endl, Michael; Fortney, Jonathan J; Gautier, Thomas N; Gilliland, Ronald L; Haas, Michael R; Hall, Jennifer R; Holman, Matthew J; Howard, Andrew W; Howell, Steve B; Isaacson, Howard; Jenkins, Jon M; Klaus, Todd C; Latham, David W; Li, Jie; Marcy, Geoffrey W; Mazeh, Tsevi; Quintana, Elisa V; Robertson, Paul; Shporer, Avi; Steffen, Jason H; Windmiller, Gur; Koch, David G; Borucki, William J

2012-01-11

Most Sun-like stars in the Galaxy reside in gravitationally bound pairs of stars (binaries). Although long anticipated, the existence of a 'circumbinary planet' orbiting such a pair of normal stars was not definitively established until the discovery of the planet transiting (that is, passing in front of) Kepler-16. Questions remained, however, about the prevalence of circumbinary planets and their range of orbital and physical properties. Here we report two additional transiting circumbinary planets: Kepler-34 (AB)b and Kepler-35 (AB)b, referred to here as Kepler-34 b and Kepler-35 b, respectively. Each is a low-density gas-giant planet on an orbit closely aligned with that of its parent stars. Kepler-34 b orbits two Sun-like stars every 289 days, whereas Kepler-35 b orbits a pair of smaller stars (89% and 81% of the Sun's mass) every 131 days. The planets experience large multi-periodic variations in incident stellar radiation arising from the orbital motion of the stars. The observed rate of circumbinary planets in our sample implies that more than ∼1% of close binary stars have giant planets in nearly coplanar orbits, yielding a Galactic population of at least several million.

How can periodic orbits puzzle out the coexistence of terrestrial planets with giant eccentric ones?

NASA Astrophysics Data System (ADS)

Antoniadou, K. I.; Libert, A.-S.

2017-09-01

Hitherto unprecedented detections of exoplanets have been triggered by missions and ground based telescopes. The quest of ``exo-Earths'' has become intriguing and the long-term stability of planetary orbits is a crucial factor for the biosphere to evolve. Planets in mean-motion resonances (MMRs) prompt the investigation of the dynamics in the framework of the three-body problem, where the families of stable periodic orbits constitute the backbone of stability domains in phase space. In this talk, we address the question of the possible coexistence of terrestrial planets with a giant companion on circular or eccentric orbit and explore the extent of the stability regions, when both the eccentricity of the outer giant planet and the semi-major axis of the inner terrestrial one vary, i.e. we investigate both non-resonant and resonant configurations. The families of periodic orbits in the restricted three-body problem are computed for the 3/2, 2/1, 5/2, 3/1, 4/1 and 5/1 MMRs. We then construct maps of dynamical stability (DS-maps) to identify the boundaries of the stability domains where such a coexistence is allowed. Guided by the periodic orbits, we delve into regular motion in phase space and propose the essential values of the orbital elements, in order for such configurations to survive long time spans and hence, for observations to be complemented or revised.

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

Lunar and terrestrial planet formation in the Grand Tack scenario.

PubMed

Jacobson, S A; Morbidelli, A

2014-09-13

We present conclusions from a large number of N-body simulations of the giant impact phase of terrestrial planet formation. We focus on new results obtained from the recently proposed Grand Tack model, which couples the gas-driven migration of giant planets to the accretion of the terrestrial planets. The giant impact phase follows the oligarchic growth phase, which builds a bi-modal mass distribution within the disc of embryos and planetesimals. By varying the ratio of the total mass in the embryo population to the total mass in the planetesimal population and the mass of the individual embryos, we explore how different disc conditions control the final planets. The total mass ratio of embryos to planetesimals controls the timing of the last giant (Moon-forming) impact and its violence. The initial embryo mass sets the size of the lunar impactor and the growth rate of Mars. After comparing our simulated outcomes with the actual orbits of the terrestrial planets (angular momentum deficit, mass concentration) and taking into account independent geochemical constraints on the mass accreted by the Earth after the Moon-forming event and on the time scale for the growth of Mars, we conclude that the protoplanetary disc at the beginning of the giant impact phase must have had most of its mass in Mars-sized embryos and only a small fraction of the total disc mass in the planetesimal population. From this, we infer that the Moon-forming event occurred between approximately 60 and approximately 130 Myr after the formation of the first solids and was caused most likely by an object with a mass similar to that of Mars. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

GIANT IMPACT: AN EFFICIENT MECHANISM FOR THE DEVOLATILIZATION OF SUPER-EARTHS

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

Liu, Shang-Fei; Hori, Yasunori; Lin, D. N. C.

Mini-Neptunes and volatile-poor super-Earths coexist on adjacent orbits in proximity to host stars such as Kepler-36 and Kepler-11. Several post-formation processes have been proposed for explaining the origin of the compositional diversity between neighboring planets: mass loss via stellar XUV irradiation, degassing of accreted material, and in situ accumulation of the disk gas. Close-in planets are also likely to experience giant impacts during the advanced stage of planet formation. This study examines the possibility of transforming volatile-rich super-Earths/mini-Neptunes into volatile-depleted super-Earths through giant impacts. We present the results of three-dimensional hydrodynamic simulations of giant impacts in the accretionary and disruptivemore » regimes. Target planets are modeled with a three-layered structure composed of an iron core, silicate mantle, and hydrogen/helium envelope. In the disruptive case, the giant impact can remove most of the H/He atmosphere immediately and homogenize the refractory material in the planetary interior. In the accretionary case, the planet is able to retain more than half of the original gaseous envelope, while a compositional gradient suppresses efficient heat transfer as the planetary interior undergoes double-diffusive convection. After the giant impact, a hot and inflated planet cools and contracts slowly. The extended atmosphere enhances the mass loss via both a Parker wind induced by thermal pressure and hydrodynamic escape driven by the stellar XUV irradiation. As a result, the entire gaseous envelope is expected to be lost due to the combination of those processes in both cases. Based on our results, we propose that Kepler-36b may have been significantly devolatilized by giant impacts, while a substantial fraction of Kepler-36c’s atmosphere may remain intact. Furthermore, the stochastic nature of giant impacts may account for the observed large dispersion in the mass–radius relationship of close

The giant planets and their satellites: Report on the Cospar Symposium, Ottawa, Canada, May 18-21, 1982

USGS Publications Warehouse

Kivelson, M.G.; Behannon, K.W.; Cravens, T.E.; de Pater, I.; Johnson, T.V.; Matson, D.L.; Masursky, H.; Southwood, D.J.; Vasyliunas, V.M.

1983-01-01

A Symposium on the Giant Planets and Their Satellites was presented in conjunction with the Twenty-fourth Plenary Meeting of the Committee on Space Research. This paper summarizes the talks presented and places the remaining papers of this volume in context. ?? 1983.

Exploring Disks Around Planets

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

Giant planets are thought to form in circumstellar disks surrounding young stars, but material may also accrete into a smaller disk around the planet. Weve never detected one of these circumplanetary disks before but thanks to new simulations, we now have a better idea of what to look for.Image from previous work simulating a Jupiter-mass planet forming inside a circumstellar disk. The planet has its own circumplanetary disk of accreted material. [Frdric Masset]Elusive DisksIn the formation of giant planets, we think the final phase consists of accretion onto the planet from a disk that surrounds it. This circumplanetary disk is important to understand, since it both regulates the late gas accretion and forms the birthplace of future satellites of the planet.Weve yet to detect a circumplanetary disk thus far, because the resolution needed to spot one has been out of reach. Now, however, were entering an era where the disk and its kinematics may be observable with high-powered telescopes (like the Atacama Large Millimeter Array).To prepare for such observations, we need models that predict the basic characteristics of these disks like the mass, temperature, and kinematic properties. Now a researcher at the ETH Zrich Institute for Astronomy in Switzerland, Judit Szulgyi, has worked toward this goal.Simulating CoolingSzulgyi performs a series of 3D global radiative hydrodynamic simulations of 1, 3, 5, and 10 Jupiter-mass (MJ) giant planets and their surrounding circumplanetary disks, embedded within the larger circumstellar disk around the central star.Density (left column), temperature (center), and normalized angular momentum (right) for a 1 MJ planet over temperatures cooling from 10,000 K (top) to 1,000 K (bottom). At high temperatures, a spherical circumplanetary envelope surrounds the planet, but as the planet cools, the envelope transitions around 64,000 K to a flattened disk. [Szulgyi 2017]This work explores the effects of different planet temperatures and

Detection of Planets Orbiting Sun-Like Stars

NASA Astrophysics Data System (ADS)

Marcy, Geoffrey W.; Butler, R. Paul

1996-12-01

During the past 11 months, astronomers have finally discovered planets orbiting Sun-like stars. A total of eight planets has been detected by the Doppler technique, and there are possible planets detected by astrometry around one other star. Some of the new planets exhibit properties similar to those in our Solar System. But many of them have properties that were unexpected. Several planets are more massive than Jupiter, and some orbit their host star in orbits smaller than Mercury's orbit. Equally unexpected is that three of these planets have noncircular orbits. Current theory of the formation of planetary systems is challenged to account for these new planetary properties, but several models are emerging, involving gravitational scattering of planetesimals and viscous or tidal decay of orbits. The occurrence rate of true analogs of our Solar System will soon be determined with the detection of long-period gas giants analogous to Jupiter.

On the Variation of Zonal Gravity Coefficients of a Giant Planet Caused by Its Deep Zonal Flows

NASA Astrophysics Data System (ADS)

Kong, Dali; Zhang, Keke; Schubert, Gerald

2012-04-01

Rapidly rotating giant planets are usually marked by the existence of strong zonal flows at the cloud level. If the zonal flow is sufficiently deep and strong, it can produce hydrostatic-related gravitational anomalies through distortion of the planet's shape. This paper determines the zonal gravity coefficients, J 2n , n = 1, 2, 3, ..., via an analytical method taking into account rotation-induced shape changes by assuming that a planet has an effective uniform density and that the zonal flows arise from deep convection and extend along cylinders parallel to the rotation axis. Two different but related hydrostatic models are considered. When a giant planet is in rigid-body rotation, the exact solution of the problem using oblate spheroidal coordinates is derived, allowing us to compute the value of its zonal gravity coefficients \\bar{J}_{2n}, n=1,2,3, \\dots, without making any approximation. When the deep zonal flow is sufficiently strong, we develop a general perturbation theory for estimating the variation of the zonal gravity coefficients, \\Delta {J}_{2n}={J}_{2n}-\\bar{J}_{2n}, n=1,2,3, \\dots, caused by the effect of the deep zonal flows for an arbitrarily rapidly rotating planet. Applying the general theory to Jupiter, we find that the deep zonal flow could contribute up to 0.3% of the J 2 coefficient and 0.7% of J 4. It is also found that the shape-driven harmonics at the 10th zonal gravity coefficient become dominant, i.e., \\Delta {J}_{2n} \\,{\\ge}\\, \\bar{J}_{2n} for n >= 5.

Planet Traps and Planetary Cores: Origins of the Planet-Metallicity Correlation

NASA Astrophysics Data System (ADS)

Hasegawa, Yasuhiro; Pudritz, Ralph E.

2014-10-01

Massive exoplanets are observed preferentially around high metallicity ([Fe/H]) stars while low-mass exoplanets do not show such an effect. This so-called planet-metallicity correlation generally favors the idea that most observed gas giants at r < 10 AU are formed via a core accretion process. We investigate the origin of this phenomenon using a semi-analytical model, wherein the standard core accretion takes place at planet traps in protostellar disks where rapid type I migrators are halted. We focus on the three major exoplanetary populations—hot Jupiters, exo-Jupiters located at r ~= 1 AU, and the low-mass planets. We show using a statistical approach that the planet-metallicity correlations are well reproduced in these models. We find that there are specific transition metallicities with values [Fe/H] = -0.2 to -0.4, below which the low-mass population dominates, and above which the Jovian populations take over. The exo-Jupiters significantly exceed the hot Jupiter population at all observed metallicities. The low-mass planets formed via the core accretion are insensitive to metallicity, which may account for a large fraction of the observed super-Earths and hot-Neptunes. Finally, a controlling factor in building massive planets is the critical mass of planetary cores (M c, crit) that regulates the onset of rapid gas accretion. Assuming the current data is roughly complete at [Fe/H] > -0.6, our models predict that the most likely value of the "mean" critical core mass of Jovian planets is langM c, critrang ~= 5 M ⊕ rather than 10 M ⊕. This implies that grain opacities in accreting envelopes should be reduced in order to lower M c, crit.

SIM PlanetQuest Key Project Precursor Observations to Detect Gas Giant Planets Around Young Stars

NASA Technical Reports Server (NTRS)

Tanner, Angelle; Beichman, Charles; Akeson, Rachel; Ghez, Andrea; Grankin, Konstantin N.; Herbst, William; Hillenbrand, Lynne; Huerta, Marcos; Konopacky, Quinn; Metchev, Stanimir;

Detectability of the Reflection Signal from Inner Planets

NASA Technical Reports Server (NTRS)

Borucki, W. J.; Jenkins, J. M.; Scargle, J.; Koch, D.; Doyle, L. R.; Cuzzi, Jeffrey (Technical Monitor)

1996-01-01

Mayor and Queloz (1996) and Marcy and Butler (1996) have found massive planets with orbital periods Tp=approx.4 days around two solar-like stars (51 Pegasi and v Andromeda). These planets are most likely similar in size and composition to the gas giants in our solar system (Burrows et al 1996). Based on this expectation and assuming the same albedo as Jupiter, we examined the feasibility of searching for similar planets with a dedicated space-based 1-m telescope. The Kepler mission will survey approximately 70,000 main-sequence dwarf stars from 9 to 14 mag continuously for four years to detect transiting Earthlike planets. Based on the detection statistics of Marcy and Butler, we expect to detect 1400 inner-orbit giant planets. Such planets in a much wider range of orbital inclinations (i) will produce nearly sinusoidal modulations of the star light flux due to the varying planetary phases. The relative signal amplitudes are of order 2x10(exp -5) and decrease as Tp(exp 4/3) for i >> 0deg. We estimated the expected signal to noise ratio (SNR) using the solar irradiance measurements from the ACRIM 1 experiment along with expected shot and detector noises. The figure shows SNR as a function of Tp for a 12 mag star, and indicates the planet radius required for detection. The survey will be sensitive to planets with periods from 12 hr to approx.8 days at the 6 sigma level.

Numerical simulation of experiments in the Giant Planet Facility

NASA Technical Reports Server (NTRS)

Green, M. J.; Davy, W. C.

1979-01-01

Utilizing a series of existing computer codes, ablation experiments in the Giant Planet Facility are numerically simulated. Of primary importance is the simulation of the low Mach number shock layer that envelops the test model. The RASLE shock-layer code, used in the Jupiter entry probe heat-shield design, is adapted to the experimental conditions. RASLE predictions for radiative and convective heat fluxes are in good agreement with calorimeter measurements. In simulating carbonaceous ablation experiments, the RASLE code is coupled directly with the CMA material response code. For the graphite models, predicted and measured recessions agree very well. Predicted recession for the carbon phenolic models is 50% higher than that measured. This is the first time codes used for the Jupiter probe design have been compared with experiments.

Chemical abundances and kinematics of 257 G-, K-type field giants. Setting a base for further analysis of giant-planet properties orbiting evolved stars

NASA Astrophysics Data System (ADS)

Adibekyan, V. Zh.; Benamati, L.; Santos, N. C.; Alves, S.; Lovis, C.; Udry, S.; Israelian, G.; Sousa, S. G.; Tsantaki, M.; Mortier, A.; Sozzetti, A.; De Medeiros, J. R.

2015-06-01

We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) for a sample of 257 G- and K-type evolved stars from the CORALIE planet search programme. To date, only one of these stars is known to harbour a planetary companion. We aimed to characterize this large sample of evolved stars in terms of chemical abundances and kinematics, thus setting a solid base for further analysis of planetary properties around giant stars. This sample, being homogeneously analysed, can be used as a comparison sample for other planet-related studies, as well as for different type of studies related to stellar and Galaxy astrophysics. The abundances of the chemical elements were determined using an local thermodynamic equilibrium (LTE) abundance analysis relative to the Sun, with the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. To separate the Galactic stellar populations, both a purely kinematical approach and a chemical method were applied. We confirm the overabundance of Na in giant stars compared to the field FGK dwarfs. This enhancement might have a stellar evolutionary character, but departures from LTE may also produce a similar enhancement. Our chemical separation of stellar populations also suggests a `gap' in metallicity between the thick-disc and high-α metal-rich stars, as previously observed in dwarfs sample from HARPS. The present sample, as most of the giant star samples, also suffers from the B - V colour cut-off, which excludes low-log g stars with high metallicities, and high-log g star with low [Fe/H]. For future studies of planet occurrence dependence on stellar metallicity around these evolved stars, we suggest to use a subsample of stars in a `cut-rectangle' in the log g-[Fe/H] diagram to overcome the aforementioned issue.

A Cloud Microphysics Model for the Gas Giant Planets

NASA Astrophysics Data System (ADS)

Palotai, Csaba J.; Le Beau, Raymond P.; Shankar, Ramanakumar; Flom, Abigail; Lashley, Jacob; McCabe, Tyler

2016-10-01

Recent studies have significantly increased the quality and the number of observed meteorological features on the jovian planets, revealing banded cloud structures and discrete features. Our current understanding of the formation and decay of those clouds also defines the conceptual modes about the underlying atmospheric dynamics. The full interpretation of the new observational data set and the related theories requires modeling these features in a general circulation model (GCM). Here, we present details of our bulk cloud microphysics model that was designed to simulate clouds in the Explicit Planetary Hybrid-Isentropic Coordinate (EPIC) GCM for the jovian planets. The cloud module includes hydrological cycles for each condensable species that consist of interactive vapor, cloud and precipitation phases and it also accounts for latent heating and cooling throughout the transfer processes (Palotai and Dowling, 2008. Icarus, 194, 303-326). Previously, the self-organizing clouds in our simulations successfully reproduced the vertical and horizontal ammonia cloud structure in the vicinity of Jupiter's Great Red Spot and Oval BA (Palotai et al. 2014, Icarus, 232, 141-156). In our recent work, we extended this model to include water clouds on Jupiter and Saturn, ammonia clouds on Saturn, and methane clouds on Uranus and Neptune. Details of our cloud parameterization scheme, our initial results and their comparison with observations will be shown. The latest version of EPIC model is available as open source software from NASA's PDS Atmospheres Node.

Coupling between atmospheric layers in gaseous giant planets due to lightning-generated electromagnetic pulses

NASA Astrophysics Data System (ADS)

Luque, A.; Dubrovin, D.; Gordillo-Vázquez, F. J.; Ebert, U.; Parra-Rojas, F. C.; Yair, Y.; Price, C.

2014-10-01

Atmospheric electricity has been detected in all gaseous giants of our solar system and is therefore likely present also in extrasolar planets. Building upon measurements from Saturn and Jupiter, we investigate how the electromagnetic pulse emitted by a lightning stroke affects upper layers of a gaseous giant. This effect is probably significantly stronger than that on Earth. We find that electrically active storms may create a localized but long-lasting layer of enhanced ionization of up to 103 cm-3 free electrons below the ionosphere, thus extending the ionosphere downward. We also estimate that the electromagnetic pulse transports 107 J to 1010 J toward the ionosphere. There emissions of light of up to 108 J would create a transient luminous event analogous to a terrestrial "elve."

SDSS-III MARVELS Planet Candidate RV Follow-up

NASA Astrophysics Data System (ADS)

Ge, Jian; Thomas, Neil; Ma, Bo; Li, Rui; SIthajan, Sirinrat

2014-02-01

Planetary systems, discovered by the radial velocity (RV) surveys, reveal strong correlations between the planet frequency and stellar properties, such as metallicity and mass, and a greater diversity in planets than found in the solar system. However, due to the sample sizes of extant surveys (~100 to a few hundreds of stars) and their heterogeneity, many key questions remained to be addressed: Do metal poor stars obey the same trends for planet occurrence as metal rich stars? What is the distribution of giant planets around intermediate- mass stars and binaries? Is the ``planet desert'' within 0.6 AU in the planet orbital distribution of intermediate-mass stars real? The MARVELS survey has produced the largest homogeneous RV measurements of 3300 V=7.6-12 FGK stars. The latest data pipeline effort at UF has been able to remove long term systematic errors suffered in the earlier data pipeline. 18 high confident giant planet candidates have been identified among newly processed data. We propose to follow up these giant planet candidates with the KPNO EXPERT instrument to confirm the detection and also characterize their orbits. The confirmed planets will be used to measure occurrence rates, distributions and multiplicity of giants planets around F,G,K stars with a broad range of mass (~0.6-2.5 M_⊙) and metallicity ([Fe/H]~-1.5-0.5). The well defined MARVELS survey cadence allows robust determinations of completeness limits for rigorously testing giant planet formation theories and constraining models.

Volatile Loss from the Proto-Lunar Disk

NASA Astrophysics Data System (ADS)

Albarede, F.

2016-12-01

Exchange of volatile elements between the Moon and Earth depends on the intrinsic volatility of each element in a H-free tenuous gas, gravitational escape, and the mean free path of elements. The H2 pressure in the gas formed by the giant impact is far too low to allow hydrodynamic entrainment of other species. A condition for gravitational escape is, therefore, that thermal velocity exceeds escape velocity at the base of the exosphere where collisions between atoms cease. Away from the Earth, the vertical pull of the disk is only a small fraction of the radial pull of the Earth, which is strong enough to keep all the elements but H and He in terrestrial orbits, and the disk exosphere is thick. The proportion of gas orbiting above the exosphere is small, its temperature has been strongly reduced by adiabatic expansion, and therefore escape of lunar volatiles to Earth should be very limited. Whether elements have been lost by escape from the Moon to Earth nevertheless can be tested by comparing the relative abundances of elements with very similar chemistry and intrinsic volatility, but with very different atomic masses. Standard sequences of mineral condensation from the Solar Nebula and T50 are irrelevant to the proto-lunar disk. Condensation temperatures in the Solar Nebula are known to vary wildly with PH2, and the PH2 of the Solar Nebula is largely insensitive to the condensation of solid mineral phases, such as those forming the mantle and core of planets. Lunar accretion follows an opposite scenario, with an early and dramatic pressure drop due to metal and silicate condensation, which is the rationale behind the intrinsic volatility scale of Albarede et al. (2015). It is observed that, despite a broad mass range, the degree of depletion in the Moon relative to the Earth or CIs is similar for chemical kins, such as the groups of alkali elements (Li, Na, K, Rb, Cs), halogens (F, Cl, Br, I), or Zn and Cd. This observation argues against massive escape of

Resolving the inconsistency between the ice giants and cometary D/H ratios

NASA Astrophysics Data System (ADS)

Ali-Dib, M.; Mousis, O.; Petit, J.-M.; Lunine, J. I.

2014-12-01

The properties and chemical compositions of giant planets strongly depend on their formation locations. The formation mechanisms of the ice giants Uranus and Neptune, and their elemental and isotopic compositions, have long been debated. The density of solids in the outer protosolar nebula is too low to explain their formation within a timescale consistent with the presence of the gaseous protoplanetary disk, and spectroscopic observations show that both planets are highly enriched in carbon, very poor in nitrogen, and the ices from which they originally formed might had deuterium-to-hydrogen ratios lower than the predicted cometary value, unexplained properties observed in no other planets. Here we show that all these properties can be explained naturally if Uranus and Neptune both formed at the carbon monoxide iceline location, namely the region where this gas condensates in the protosolar nebula. This outer region of the protosolar nebula intrinsically has enough surface density to form both planets from carbon-rich solids but nitrogen-depleted gas, in abundances consistent with their observed values. Water rich interiors originating mostly from transformed CO ices reconcile the D/H value observed in Uranus and Neptune with the cometary value.

Growing the terrestrial planets from the gradual accumulation of submeter-sized objects.

PubMed

Levison, Harold F; Kretke, Katherine A; Walsh, Kevin J; Bottke, William F

2015-11-17

Building the terrestrial planets has been a challenge for planet formation models. In particular, classical theories have been unable to reproduce the small mass of Mars and instead predict that a planet near 1.5 astronomical units (AU) should roughly be the same mass as Earth. Recently, a new model called Viscously Stirred Pebble Accretion (VSPA) has been developed that can explain the formation of the gas giants. This model envisions that the cores of the giant planets formed from 100- to 1,000-km bodies that directly accreted a population of pebbles-submeter-sized objects that slowly grew in the protoplanetary disk. Here we apply this model to the terrestrial planet region and find that it can reproduce the basic structure of the inner solar system, including a small Mars and a low-mass asteroid belt. Our models show that for an initial population of planetesimals with sizes similar to those of the main belt asteroids, VSPA becomes inefficient beyond ∼ 1.5 AU. As a result, Mars's growth is stunted, and nothing large in the asteroid belt can accumulate.

Accumulation of planets into the proto-planetary cloud as a process of occurring an amount of characteristic scales into the nonlinear self organized dynamical systems

NASA Astrophysics Data System (ADS)

Professor Khachay, Yurie

2015-04-01

Two characteristic times are significant for evolution the interior of the homogeneous proto-planetary cloud: the time of bodies free fall towards the clouds mass center and the time of sound distribution through the cloud. With the beginning of proto-planetary disk fragmentation and accumulation of the proto-planets from the bodies and particles there are formed matter content heterogeneities of the finite dimension, heterogeneities of temperature, density and values of kinetic coefficients. The system became more and more complicated with interior interconnections. By the growing of the bodies the difference between the values of the characteristic times and dimensions become larger. The dynamical evolution of the system we could observe with use the numerical modeling of the Earth and Moon formation into the 3-D model [1,2]. The fact, that the linear dimensions of the objects during the accumulation process change from the centimeter and meter dimensions to some thousands of kilometers significantly prevent the mathematical description of these processes. The corresponding values of the no dimensional similarity criterions, which are included into the systems of differential equations, which describe the proto-planetary growing, the conditions for entropy and mass on the growing surface, the equations of the impulse balance, energy and mass into the interior parts of the planet change on an orders of values. Therefore we used very detailed space and time grids for solution the problem using the method of finite differences. The additional complications occur according to necessity to take into account the nonlinear dependence of matter viscosity from the temperature, pressure and chemical matter content. At last we took into account the principal random distribution of heterogeneities, stipulated by bodies and particles falling. Only progression towards that direction and constructing corresponding systems of observation and interpretation allow to hope

Investigating the Orbital Period Valley of Giant Planets in Kepler Data

NASA Astrophysics Data System (ADS)

Thomas, Brianna P.; Birkby, Jayne L.

2016-01-01

Transit light curves contain a wealth of information about the basic properties of a planet, such as its radius, semi-major axis, and orbital period. For the latter property, there is a distinct lack of planets with periods between 10 to 100 days. This gap could be caused by something as simple as observational bias, or as prominent as planetary formation or migration. Here, we report an investigation into the atmosphere of planets within this orbital period valley, to search for differences that may indicate a different formation mechanism or migration path to those outside of it. We do this by searching for the secondary eclipse of planets in the valley in order to measure their albedos. We determined an optimal target for this: KOI-366 b (P ~ 75 days). However, we find that despite the exquisite precision of Kepler data, it cannot constrain the albedo for this long-orbit planet candidate. We measure a 1σ upper limit on the geometric albedo of Ag,1σ ≤ 2.0. We highlight that additional scatter in the light curve is likely caused by a ~ 2-day pulsation of the giant host star, and that further data is required to measure the secondary eclipse. KOI-366 is one of the best suited of all host stars with long period exoplanet candidates for follow-up due to its relatively bright magnitude (Kp = 11.7 mag), but the full investigation of the reflective properties of long period planets may require space-based observations from future instruments, such as WFIRST, that will be more sensitive to objects further away from their host stars. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution. This work was performed in part under contract with the Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

The ODINUS Mission Concept: a Mission for the exploration the Ice Giant Planets

NASA Astrophysics Data System (ADS)

Peron, Roberto

We present the scientific case and the mission concept of a proposal for the the comparative exploration of the ice giant planets Uranus and Neptune and their satellites with a pair of twin spacecraft: ODINUS (Origins, Dynamics and Interiors of Neptunian and Uranian Systems). The ODINUS proposal was submitted in response to the call for white papers for the definition of the themes of the L2 and L3 mission in the framework of ESA Cosmic Vision 2015-2025 program. The goal of ODINUS is the advancement of our understanding of the ancient past of the Solar System and, more generally, of how planetary systems form and evolve. The mission concept is focused on providing elements to answer to the scientific themes of the Cosmic Vision 2015-2025 program: What are the conditions for planetary formation and the emergency of life? How does the Solar System work? What are the fundamental physical laws of the Universe? In order to achieve its goals, ODINUS foresees the use of two twin spacecraft to be placed in orbit around Uranus and Neptune respectively, with selected flybys of their satellites. The proposed measurements aim to study the atmospheres and magnetospheres of the planets, the surfaces of the satellites, and the interior structure and composition of both satellites and planets. An important possibility for performing fundamental physics studies (among them tests of general relativity theory) is offered by the cruise phase. After the extremely positive evaluation of ESA Senior Survey Committee, who stated that ``the exploration of the icy giants appears to be a timely milestone, fully appropriate for an L class mission'', we discuss strategies to comparatively study Uranus and Neptune with future international missions.

Convection and Dynamo Action in Ice Giant Dynamo Models with Electrical Conductivity Stratification

NASA Astrophysics Data System (ADS)

Soderlund, K. M.; Featherstone, N. A.; Heimpel, M. H.; Aurnou, J. M.

2017-12-01

Uranus and Neptune are relatively unexplored, yet critical for understanding the physical and chemical processes that control the behavior and evolution of giant planets. Because their multipolar magnetic fields, three-jet zonal winds, and extreme energy balances are distinct from other planets in our Solar System, the ice giants provide a unique opportunity to test hypotheses for internal dynamics and magnetic field generation. While it is generally agreed that dynamo action in the ionic ocean generates their magnetic fields, the mechanisms that control the morphology, strength, and evolution of the dynamos - which are likely distinct from those in the gas giants and terrestrial planets - are not well understood. We hypothesize that the dynamos and zonal winds are dynamically coupled and argue that their characteristics are a consequence of quasi-three-dimensional turbulence in their interiors. Here, we will present new dynamo simulations with an inner electrically conducting region and outer electrically insulating layer to self-consistently couple the ionic oceans and molecular envelopes of these planets. For each simulation, the magnetic field morphology and amplitude, zonal flow profile, and internal heat flux pattern will be compared against corresponding observations of Uranus and Neptune. We will also highlight how these simulations will both contribute to and benefit from a future ice giant mission.

Scattering V-type asteroids during the giant planet instability: a step for Jupiter, a leap for basalt

NASA Astrophysics Data System (ADS)

Brasil, P. I. O.; Roig, F.; Nesvorný, D.; Carruba, V.

2017-06-01

V-type asteroids are a taxonomic class whose surface is associated with a basaltic composition. The only known source of V-type asteroids in the Main Asteroid Belt is (4) Vesta, which is located in the inner part of the Main Belt. However, many V-type asteroids cannot be dynamically linked to Vesta, in particular, those asteroids located in the middle and outer parts of the Main Belt. Previous works have failed to find mechanisms to transport V-type asteroids from the inner to the middle and outer belts. In this work, we propose a dynamical mechanism that could have acted on primordial asteroid families. We consider a model of the giant planet migration known as the jumping Jupiter model with five planets. Our study is focused on the period of 10 Myr that encompasses the instability phase of the giant planets. We show that, for different hypothetical Vesta-like paleo-families in the inner belt, the perturbations caused by the ice giant that is scattered into the asteroid belt before being ejected from the Solar system are able to scatter V-type asteroids to the middle and outer belts. Based on the orbital distribution of V-type candidates identified from the Sloan Digital Sky Survey and the VISTA Survey colours, we show that this mechanism is efficient enough provided that the hypothetical paleo-family originated from a 100 to 500 km crater excavated on the surface of (4) Vesta. This mechanism is able to explain the currently observed V-type asteroids in the middle and outer belts, with the exception of (1459) Magnya.

An Integral-Field Spectrograph for a Terrestrial Planet Finding Mission

NASA Technical Reports Server (NTRS)

Heap, Sara R.

2011-01-01

We describe a conceptual design for an integral field spectrograph for characterizing exoplanets that we developed for NASA's Terrestrial Planet Finder Coronagraph (TPF-C), although it is equally applicable to an external-occulter mission. The spectrograph fulfills all four scientific objectives of a terrestrial planet finding mission by: (1) Spectrally characterizing the atmospheres of detected planets in search of signatures of habitability or even biological activity; (2) Directly detecting terrestrial planets in the habitable zone around nearby stars; (3) Studying all constituents of a planetary system including terrestrial and giant planets, gas and dust around sun-like stars of different ages and metallicities; (4) Enabling simultaneous, high-spatial-resolution, spectroscopy of all astrophysical sources regardless of central source luminosity, such as AGN's, proplyds, etc.

Planet traps and planetary cores: origins of the planet-metallicity correlation

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

Hasegawa, Yasuhiro; Pudritz, Ralph E., E-mail: yasu@asiaa.sinica.edu.tw, E-mail: pudritz@physics.mcmaster.ca

2014-10-10

Massive exoplanets are observed preferentially around high metallicity ([Fe/H]) stars while low-mass exoplanets do not show such an effect. This so-called planet-metallicity correlation generally favors the idea that most observed gas giants at r < 10 AU are formed via a core accretion process. We investigate the origin of this phenomenon using a semi-analytical model, wherein the standard core accretion takes place at planet traps in protostellar disks where rapid type I migrators are halted. We focus on the three major exoplanetary populations—hot Jupiters, exo-Jupiters located at r ≅ 1 AU, and the low-mass planets. We show using a statisticalmore » approach that the planet-metallicity correlations are well reproduced in these models. We find that there are specific transition metallicities with values [Fe/H] = –0.2 to –0.4, below which the low-mass population dominates, and above which the Jovian populations take over. The exo-Jupiters significantly exceed the hot Jupiter population at all observed metallicities. The low-mass planets formed via the core accretion are insensitive to metallicity, which may account for a large fraction of the observed super-Earths and hot-Neptunes. Finally, a controlling factor in building massive planets is the critical mass of planetary cores (M {sub c,} {sub crit}) that regulates the onset of rapid gas accretion. Assuming the current data is roughly complete at [Fe/H] > –0.6, our models predict that the most likely value of the 'mean' critical core mass of Jovian planets is (M {sub c,} {sub crit}) ≅ 5 M {sub ⊕} rather than 10 M {sub ⊕}. This implies that grain opacities in accreting envelopes should be reduced in order to lower M {sub c,} {sub crit}.« less

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 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.

A giant planet in the triple system HD 132563

NASA Astrophysics Data System (ADS)

Desidera, S.; Carolo, E.; Gratton, R.; Martinez Fiorenzano, A. F.; Endl, M.; Mesa, D.; Barbieri, M.; Bonavita, M.; Cecconi, M.; Claudi, R. U.; Cosentino, R.; Marzari, F.; Scuderi, S.

2011-09-01

As part of our radial velocity planet-search survey performed with SARG at TNG, we monitored the components of HD 132563 for ten years. It is a binary system formed by two rather similar solar type stars with a projected separation of 4.1 arcsec, which corresponds to 400 AU at the distance of 96 pc. The two components are moderately metal-poor ([Fe/H] = -0.19), and the age of the system is about 5 Gyr. We detected RV variations of HD 132563B with period of 1544 days and semi-amplitude of 26 m/s. From the star characteristics and line profile measurements, we infer their Keplerian origin. Therefore HD 132563B turns out to host a planet with a projected mass msini = 1.49 MJ at 2.6 AU with a moderately eccentric orbit (e = 0.22). The planet around HD 132563B is one of the few that are known in triple stellar systems, as we found that the primary HD 132563A is itself a spectroscopic binary with a period longer than 15 years and an eccentricity higher than 0.65. The spectroscopic component was not detected in adaptive-optics images taken with the instrument AdOpt mounted at the TNG, since it expected at a projected separation that was smaller than 0.2 arcsec at the time of our observations. A small excess in K band difference between the components with respect to the difference in V band is compatible with a companion of about 0.55 M⊙. A preliminary statistical analysis of when planets occur in triple systems indicate a similar frequency of planets around the isolated component in a triple system, components of wide binaries and single stars. There is no significant iron abundance difference between the components. The lack of stars in binary systems and open clusters showing strong enhancements of iron abundance, which are comparable to the typical metallicity difference between stars with and without giant planets, agrees with the idea that accretion of planetary material producing iron abundance anomalies over 0.1 dex is rare. Based on observations made with the

Laser-driven shock experiments on precompressed water: Implications for "icy" giant planets.

PubMed

Lee, Kanani K M; Benedetti, L Robin; Jeanloz, Raymond; Celliers, Peter M; Eggert, Jon H; Hicks, Damien G; Moon, Stephen J; Mackinnon, Andrew; Da Silva, Luis B; Bradley, David K; Unites, Walter; Collins, Gilbert W; Henry, Emeric; Koenig, Michel; Benuzzi-Mounaix, Alessandra; Pasley, John; Neely, David

2006-07-07

Laser-driven shock compression of samples precompressed to 1 GPa produces high-pressure-temperature conditions inducing two significant changes in the optical properties of water: the onset of opacity followed by enhanced reflectivity in the initially transparent water. The onset of reflectivity at infrared wavelengths can be interpreted as a semiconductor<-->electronic conductor transition in water, and is found at pressures above approximately 130 GPa for single-shocked samples precompressed to 1 GPa. Our results indicate that conductivity in the deep interior of "icy" giant planets is greater than realized previously because of an additional contribution from electrons.

Chemical fingerprints of hot Jupiter planet formation

NASA Astrophysics Data System (ADS)

Maldonado, J.; Villaver, E.; Eiroa, C.

2018-05-01

Context. The current paradigm to explain the presence of Jupiter-like planets with small orbital periods (P < 10 days; hot Jupiters), which involves their formation beyond the snow line following inward migration, has been challenged by recent works that explore the possibility of in situ formation. Aims: We aim to test whether stars harbouring hot Jupiters and stars with more distant gas-giant planets show any chemical peculiarity that could be related to different formation processes. Methods: Our methodology is based on the analysis of high-resolution échelle spectra. Stellar parameters and abundances of C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn for a sample of 88 planet hosts are derived. The sample is divided into stars hosting hot (a < 0.1 au) and cool (a > 0.1 au) Jupiter-like planets. The metallicity and abundance trends of the two sub-samples are compared and set in the context of current models of planet formation and migration. Results: Our results show that stars with hot Jupiters have higher metallicities than stars with cool distant gas-giant planets in the metallicity range +0.00/+0.20 dex. The data also shows a tendency of stars with cool Jupiters to show larger abundances of α elements. No abundance differences between stars with cool and hot Jupiters are found when considering iron peak, volatile elements or the C/O, and Mg/Si ratios. The corresponding p-values from the statistical tests comparing the cumulative distributions of cool and hot planet hosts are 0.20, <0.01, 0.81, and 0.16 for metallicity, α, iron-peak, and volatile elements, respectively. We confirm previous works suggesting that more distant planets show higher planetary masses as well as larger eccentricities. We note differences in age and spectral type between the hot and cool planet host samples that might affect the abundance comparison. Conclusions: The differences in the distribution of planetary mass, period, eccentricity, and stellar host

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

Dissociation of MgSiO3 in the cores of gas giants and terrestrial exoplanets.

PubMed

Umemoto, Koichiro; Wentzcovitch, Renata M; Allen, Philip B

2006-02-17

CaIrO3-type MgSiO3 is the planet-forming silicate stable at pressures and temperatures beyond those of Earth's core-mantle boundary. First-principles quasiharmonic free-energy computations show that this mineral should dissociate into CsCl-type MgO cotunnite-type SiO2 at pressures and temperatures expected to occur in the cores of the gas giants + and in terrestrial exoplanets. At approximately 10 megabars and approximately 10,000 kelvin, cotunnite-type SiO2 should have thermally activated electron carriers and thus electrical conductivity close to metallic values. Electrons will give a large contribution to thermal conductivity, and electronic damping will suppress radiative heat transport.

An ultrahot gas-giant exoplanet with a stratosphere.

PubMed

Evans, Thomas M; Sing, David K; Kataria, Tiffany; Goyal, Jayesh; Nikolov, Nikolay; Wakeford, Hannah R; Deming, Drake; Marley, Mark S; Amundsen, David S; Ballester, Gilda E; Barstow, Joanna K; Ben-Jaffel, Lotfi; Bourrier, Vincent; Buchhave, Lars A; Cohen, Ofer; Ehrenreich, David; García Muñoz, Antonio; Henry, Gregory W; Knutson, Heather; Lavvas, Panayotis; Etangs, Alain Lecavelier des; Lewis, Nikole K; López-Morales, Mercedes; Mandell, Avi M; Sanz-Forcada, Jorge; Tremblin, Pascal; Lupu, Roxana

2017-08-02

Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum. Conversely, if there is a stratosphere-where temperature increases with altitude-these molecular features will be observed in emission. It has been suggested that stratospheres could form in highly irradiated exoplanets, but the extent to which this occurs is unresolved both theoretically and observationally. A previous claim for the presence of a stratosphere remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements. Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet stratosphere at 5σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide.

An ultrahot gas-giant exoplanet with a stratosphere

NASA Astrophysics Data System (ADS)

Evans, Thomas M.; Sing, David K.; Kataria, Tiffany; Goyal, Jayesh; Nikolov, Nikolay; Wakeford, Hannah R.; Deming, Drake; Marley, Mark S.; Amundsen, David S.; Ballester, Gilda E.; Barstow, Joanna K.; Ben-Jaffel, Lotfi; Bourrier, Vincent; Buchhave, Lars A.; Cohen, Ofer; Ehrenreich, David; García Muñoz, Antonio; Henry, Gregory W.; Knutson, Heather; Lavvas, Panayotis; Lecavelier Des Etangs, Alain; Lewis, Nikole K.; López-Morales, Mercedes; Mandell, Avi M.; Sanz-Forcada, Jorge; Tremblin, Pascal; Lupu, Roxana

2017-08-01

Infrared radiation emitted from a planet contains information about the chemical composition and vertical temperature profile of its atmosphere. If upper layers are cooler than lower layers, molecular gases will produce absorption features in the planetary thermal spectrum. Conversely, if there is a stratosphere—where temperature increases with altitude—these molecular features will be observed in emission. It has been suggested that stratospheres could form in highly irradiated exoplanets, but the extent to which this occurs is unresolved both theoretically and observationally. A previous claim for the presence of a stratosphere remains open to question, owing to the challenges posed by the highly variable host star and the low spectral resolution of the measurements. Here we report a near-infrared thermal spectrum for the ultrahot gas giant WASP-121b, which has an equilibrium temperature of approximately 2,500 kelvin. Water is resolved in emission, providing a detection of an exoplanet stratosphere at 5σ confidence. These observations imply that a substantial fraction of incident stellar radiation is retained at high altitudes in the atmosphere, possibly by absorbing chemical species such as gaseous vanadium oxide and titanium oxide.

The Pan-Pacific Planet Search. II. Confirmation of a Two-planet System around HD 121056

NASA Astrophysics Data System (ADS)

Wittenmyer, Robert A.; Wang, Liang; Liu, Fan; Horner, Jonathan; Endl, Michael; Johnson, John Asher; Tinney, C. G.; Carter, B. D.

2015-02-01

Precise radial velocities from the Anglo-Australian Telescope (AAT) confirm the presence of a rare short-period planet around the K0 giant HD 121056. An independent two-planet solution using the AAT data shows that the inner planet has P = 89.1 ± 0.1 days, and m sin i = 1.35 ± 0.17 MJup. These data also confirm the planetary nature of the outer companion, with m sin i = 3.9 ± 0.6 MJup and a = 2.96 ± 0.16 AU. HD 121056 is the most-evolved star to host a confirmed multiple-planet system, and is a valuable example of a giant star hosting both a short-period and a long-period planet.

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

Detecting Close-In Extrasolar Giant Planets with the Kepler Photometer via Scattered Light

NASA Astrophysics Data System (ADS)

Jenkins, J. M.; Doyle, L. R.; Kepler Discovery Mission Team

2003-05-01

NASA's Kepler Mission will be launched in 2007 primarily to search for transiting Earth-sized planets in the habitable zones of solar-like stars. In addition, it will be poised to detect the reflected light component from close-in extrasolar giant planets (CEGPs) similar to 51 Peg b. Here we use the DIARAD/SOHO time series along with models for the reflected light signatures of CEGPs to evaluate Kepler's ability to detect such planets. We examine the detectability as a function of stellar brightness, stellar rotation period, planetary orbital inclination angle, and planetary orbital period, and then estimate the total number of CEGPs that Kepler will detect over its four year mission. The analysis shows that intrinsic stellar variability of solar-like stars is a major obstacle to detecting the reflected light from CEGPs. Monte Carlo trials are used to estimate the detection threshold required to limit the total number of expected false alarms to no more than one for a survey of 100,000 stellar light curves. Kepler will likely detect 100-760 51 Peg b-like planets by reflected light with orbital periods up to 7 days. LRD was supported by the Carl Sagan Chair at the Center for the Study of Life in the Universe, a division of the SETI Institute. JMJ received support from the Kepler Mission Photometer and Science Office at NASA Ames Research Center.

Warm Disks from Giant Impacts

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-10-01

In the process of searching for exoplanetary systems, weve discovered tens of debris disks close around distant stars that are especially bright in infrared wavelengths. New research suggests that we might be looking at the late stages of terrestrial planet formation in these systems.Forming Terrestrial PlanetsAccording to the widely-accepted formation model for our solar-system, protoplanets the size of Mars formed within a protoplanetary disk around our Sun. Eventually, the depletion of the gas in the disk led the orbits of these protoplanets to become chaotically unstable. Finally, in the giant impact stage, many of the protoplanets collided with each other ultimately leading to the formation of the terrestrial planets and their moons as we know them today.If giant impact stages occur in exoplanetary systems, too leading to the formation of terrestrial exoplanets how would we detect this process? According to a study led by Hidenori Genda of the Tokyo Institute of Technology, we might be already be witnessing this stage in observations of warm debris disks around other stars. To test this, Genda and collaborators model giant impact stages and determine what we would expect to see from a system undergoing this violent evolution.Modeling CollisionsSnapshots of a giant impact in one of the authors simulations. The collision causes roughly 0.05 Earth masses of protoplanetary material to be ejected from the system. Click for a closer look! [Genda et al. 2015]The collaborators run a series of simulations evolving protoplanetary bodies in a solar system. The simulations begin 10 Myr into the lifetime of the solar system, i.e., after the gas from the protoplanetary disk has had time to be cleared and the protoplanetary orbits begin to destabilize. The simulations end when the protoplanets are done smashing into each other and have again settled into stable orbits, typically after ~100 Myr.The authors find that, over an average giant impact stage, the total amount of

Planet formation: constraints from transiting extrasolar planets

NASA Astrophysics Data System (ADS)

Guillot, T.; Santos, N.; Pont, F.; Iro, N.; Melo, C.; Ribas, I.

Ten extrasolar planets with masses between 105 and 430M⊕ are known to transit their star. The knowledge of their mass and radius allows an estimate of their composition, but uncertainties on equations of state, opacities and possible missing energy sources imply that only inaccurate constraints can be derived when considering each planet separately. This is illustrated by HD209458b and XO-1b, two planets that appear to be larger than models would predict. Using a relatively simple evolution model, we show that the radius anomaly, i.e. the difference between the measured and theoretically calculated radii, is anticorrelated with the metallicity of the parent star. This implies that the present size, structure and composition of these planets is largely determined by the initial metallicity of the protoplanetary disk, and not, or to a lesser extent, by other processes such as the differences in the planets' orbital evolutions, tides due to finite eccentricities/inclinations and planet evaporation. Using evolution models including the presence of a core and parametrized missing physics, we show that all nine planets belong to a same ensemble characterized by a mass of heavy elements MZ that is a steep function of the stellar metallicity: from ˜ 10 M⊕ around a solar composition star, to ˜ 100 M⊕ for twice the solar metallicity. Together with the observed lack of giant planets in close orbits around metal-poor stars, these results imply that heavy elements play a key role in the formation of close-in giant planets. The large values of MZ and of the planet enrichments for metal-rich stars shows the need for alternative theories of planet formation including migration and subsequent collection of planetesimals.

Kepler planet-detection mission: introduction and first results.

PubMed

Borucki, William J; Koch, David; Basri, Gibor; Batalha, Natalie; Brown, Timothy; Caldwell, Douglas; Caldwell, John; Christensen-Dalsgaard, Jørgen; Cochran, William D; DeVore, Edna; Dunham, Edward W; Dupree, Andrea K; Gautier, Thomas N; Geary, John C; Gilliland, Ronald; Gould, Alan; Howell, Steve B; Jenkins, Jon M; Kondo, Yoji; Latham, David W; Marcy, Geoffrey W; Meibom, Søren; Kjeldsen, Hans; Lissauer, Jack J; Monet, David G; Morrison, David; Sasselov, Dimitar; Tarter, Jill; Boss, Alan; Brownlee, Don; Owen, Toby; Buzasi, Derek; Charbonneau, David; Doyle, Laurance; Fortney, Jonathan; Ford, Eric B; Holman, Matthew J; Seager, Sara; Steffen, Jason H; Welsh, William F; Rowe, Jason; Anderson, Howard; Buchhave, Lars; Ciardi, David; Walkowicz, Lucianne; Sherry, William; Horch, Elliott; Isaacson, Howard; Everett, Mark E; Fischer, Debra; Torres, Guillermo; Johnson, John Asher; Endl, Michael; MacQueen, Phillip; Bryson, Stephen T; Dotson, Jessie; Haas, Michael; Kolodziejczak, Jeffrey; Van Cleve, Jeffrey; Chandrasekaran, Hema; Twicken, Joseph D; Quintana, Elisa V; Clarke, Bruce D; Allen, Christopher; Li, Jie; Wu, Haley; Tenenbaum, Peter; Verner, Ekaterina; Bruhweiler, Frederick; Barnes, Jason; Prsa, Andrej

2010-02-19

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

A giant planet undergoing extreme-ultraviolet irradiation by its hot massive-star host.

PubMed

Gaudi, B Scott; Stassun, Keivan G; Collins, Karen A; Beatty, Thomas G; Zhou, George; Latham, David W; Bieryla, Allyson; Eastman, Jason D; Siverd, Robert J; Crepp, Justin R; Gonzales, Erica J; Stevens, Daniel J; Buchhave, Lars A; Pepper, Joshua; Johnson, Marshall C; Colon, Knicole D; Jensen, Eric L N; Rodriguez, Joseph E; Bozza, Valerio; Novati, Sebastiano Calchi; D'Ago, Giuseppe; Dumont, Mary T; Ellis, Tyler; Gaillard, Clement; Jang-Condell, Hannah; Kasper, David H; Fukui, Akihiko; Gregorio, Joao; Ito, Ayaka; Kielkopf, John F; Manner, Mark; Matt, Kyle; Narita, Norio; Oberst, Thomas E; Reed, Phillip A; Scarpetta, Gaetano; Stephens, Denice C; Yeigh, Rex R; Zambelli, Roberto; Fulton, B J; Howard, Andrew W; James, David J; Penny, Matthew; Bayliss, Daniel; Curtis, Ivan A; DePoy, D L; Esquerdo, Gilbert A; Gould, Andrew; Joner, Michael D; Kuhn, Rudolf B; Labadie-Bartz, Jonathan; Lund, Michael B; Marshall, Jennifer L; McLeod, Kim K; Pogge, Richard W; Relles, Howard; Stockdale, Christopher; Tan, T G; Trueblood, Mark; Trueblood, Patricia

2017-06-22

The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300-10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1); the planet is itself as hot as a red dwarf star of type M (ref. 2). WASP-33b displays a large heat differential between its dayside and nightside, and is highly inflated-traits that have been linked to high insolation. However, even at the temperature of its dayside, its atmosphere probably resembles the molecule-dominated atmospheres of other planets and, given the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be substantially ablated over the lifetime of its star. Here we report observations of the bright star HD 195689 (also known as KELT-9), which reveal a close-in (orbital period of about 1.48 days) transiting giant planet, KELT-9b. At approximately 10,170 kelvin, the host star is at the dividing line between stars of type A and B, and we measure the dayside temperature of KELT-9b to be about 4,600 kelvin. This is as hot as stars of stellar type K4 (ref. 5). The molecules in K stars are entirely dissociated, and so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. Furthermore, KELT-9b receives 700 times more extreme-ultraviolet radiation (that is, with wavelengths shorter than 91.2 nanometres) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star.

Giant-Planet Chemistry: Ammonium Hydrosulfide (NH4SH), Its IR Spectra and Thermal and Radiolytic Stabilities

NASA Technical Reports Server (NTRS)

Loeffler, Mark J.; Hudson, Reggie L.; Chanover, Nancy J.; Simon, Amy A.

2015-01-01

Here we present our recent studies of proton-irradiated and unirradiated ammonium hydrosulfide, NH4SH, a compound predicted to be an important tropospheric cloud component of Jupiter and other giant planets. We irradiated both crystalline and amorphous NH4SH at 10-160 K and used IR spectroscopy to observe and identify reaction products in the ice, specifically NH3 and long-chained sulfur-containing ions. Crystalline NH4SH was amorphized during irradiation at all temperatures studied with the rate being the fastest at the lowest temperatures. Irradiation of amorphous NH4SH at approximately 10-75 K showed that 60-80% of the NH4 + remained when equilibrium was reached, and that NH4SH destruction rates were relatively constant within this temperature range. Irradiations at higher temperatures produced different dose dependence and were accompanied by pressure outbursts that, in some cases, fractured the ice. The thermal stability of irradiated NH4SH was found to be greater than that of unirradiated NH4SH, suggesting that an irradiated giant-planet cloud precipitate can exist at temperatures and altitudes not previously considered.

Influence of periodic orbits on the formation of giant planetary systems

NASA Astrophysics Data System (ADS)

Libert, Anne-Sophie; Sotiriadis, Sotiris; Antoniadou, Kyriaki I.

2018-02-01

The late-stage formation of giant planetary systems is rich in interesting dynamical mechanisms. Previous simulations of three giant planets initially on quasi-circular and quasi-coplanar orbits in the gas disc have shown that highly mutually inclined configurations can be formed, despite the strong eccentricity and inclination damping exerted by the disc. Much attention has been directed to inclination-type resonance, asking for large eccentricities to be acquired during the migration of the planets. Here we show that inclination excitation is also present at small to moderate eccentricities in two-planet systems that have previously experienced an ejection or a merging and are close to resonant commensurabilities at the end of the gas phase. We perform a dynamical analysis of these planetary systems, guided by the computation of planar families of periodic orbits and the bifurcation of families of spatial periodic orbits. We show that inclination excitation at small to moderate eccentricities can be produced by (temporary) capture in inclination-type resonance and the possible proximity of the non-coplanar systems to spatial periodic orbits contributes to maintaining their mutual inclination over long periods of time.

The GAPS Programme with HARPS-N at TNG . XIV. Investigating giant planet migration history via improved eccentricity and mass determination for 231 transiting planets

NASA Astrophysics Data System (ADS)

Bonomo, A. S.; Desidera, S.; Benatti, S.; Borsa, F.; Crespi, S.; Damasso, M.; Lanza, A. F.; Sozzetti, A.; Lodato, G.; Marzari, F.; Boccato, C.; Claudi, R. U.; Cosentino, R.; Covino, E.; Gratton, R.; Maggio, A.; Micela, G.; Molinari, E.; Pagano, I.; Piotto, G.; Poretti, E.; Smareglia, R.; Affer, L.; Biazzo, K.; Bignamini, A.; Esposito, M.; Giacobbe, P.; Hébrard, G.; Malavolta, L.; Maldonado, J.; Mancini, L.; Martinez Fiorenzano, A.; Masiero, S.; Nascimbeni, V.; Pedani, M.; Rainer, M.; Scandariato, G.

2017-06-01

We carried out a Bayesian homogeneous determination of the orbital parameters of 231 transiting giant planets (TGPs) that are alone or have distant companions; we employed differential evolution Markov chain Monte Carlo methods to analyse radial-velocity (RV) data from the literature and 782 new high-accuracy RVs obtained with the HARPS-N spectrograph for 45 systems over 3 years. Our work yields the largest sample of systems with a transiting giant exoplanet and coherently determined orbital, planetary, and stellar parameters. We found that the orbital parameters of TGPs in non-compact planetary systems are clearly shaped by tides raised by their host stars. Indeed, the most eccentric planets have relatively large orbital separations and/or high mass ratios, as expected from the equilibrium tide theory. This feature would be the outcome of planetary migration from highly eccentric orbits excited by planet-planet scattering, Kozai-Lidov perturbations, or secular chaos. The distribution of α = a/aR, where a and aR are the semi-major axis and the Roche limit, for well-determined circular orbits peaks at 2.5; this agrees with expectations from the high-eccentricity migration (HEM), although it might not be limited to this migration scenario. The few planets of our sample with circular orbits and α> 5 values may have migrated through disc-planet interactions instead of HEM. By comparing circularisation times with stellar ages, we found that hot Jupiters with a< 0.05 au have modified tidal quality factors 105 ≲ Q'p ≲ 109, and that stellar Q's ≳ 106 - 107 are required to explain the presence of eccentric planets at the same orbital distance. As aby-product of our analysis, we detected a non-zero eccentricity e = 0.104-0.018+0.021 for HAT-P-29; we determined that five planets that were previously regarded to be eccentric or to have hints of non-zero eccentricity, namely CoRoT-2b, CoRoT-23b, TrES-3b, HAT-P-23b, and WASP-54b, have circular orbits or undetermined

External supply of oxygen to the atmospheres of the giant planets.

PubMed

Feuchtgruber, H; Lellouch, E; de Graauw, T; Bézard, B; Encrenaz, T; Griffin, M

1997-09-11

The atmospheres of the giant planets are reducing, being mainly composed of hydrogen, helium and methane. But the rings and icy satellites that surround these planets, together with the flux of interplanetary dust, could act as important sources of oxygen, which would be delivered to the atmospheres mainly in the form of water ice or silicate dust. Here we report the detection, by infrared spectroscopy, of gaseous H2O in the upper atmospheres of Saturn, Uranus and Neptune. The implied H2O column densities are 1.5 x 10(15), 9 x 10(13) and 3 x 10(14) molecules cm(-2) respectively. CO2 in comparable amounts was also detected in the atmospheres of Saturn and Neptune. These observations can be accounted for by external fluxes of 10(5)-10(7) H2O molecules cm(-2) s(-1) and subsequent chemical processing in the atmospheres. The presence of gaseous water and infalling dust will affect the photochemistry, energy budget and ionospheric properties of these atmospheres. Moreover, our findings may help to constrain the injection rate and possible activity of distant icy objects in the Solar System.

Growing the terrestrial planets from the gradual accumulation of submeter-sized objects

PubMed Central

Levison, Harold F.; Kretke, Katherine A.; Walsh, Kevin J.; Bottke, William F.

2015-01-01

Building the terrestrial planets has been a challenge for planet formation models. In particular, classical theories have been unable to reproduce the small mass of Mars and instead predict that a planet near 1.5 astronomical units (AU) should roughly be the same mass as Earth. Recently, a new model called Viscously Stirred Pebble Accretion (VSPA) has been developed that can explain the formation of the gas giants. This model envisions that the cores of the giant planets formed from 100- to 1,000-km bodies that directly accreted a population of pebbles—submeter-sized objects that slowly grew in the protoplanetary disk. Here we apply this model to the terrestrial planet region and find that it can reproduce the basic structure of the inner solar system, including a small Mars and a low-mass asteroid belt. Our models show that for an initial population of planetesimals with sizes similar to those of the main belt asteroids, VSPA becomes inefficient beyond ∼ 1.5 AU. As a result, Mars’s growth is stunted, and nothing large in the asteroid belt can accumulate. PMID:26512109

FEEDBACK FROM MASSIVE STARS AND GAS EXPULSION FROM PROTO-GLOBULAR CLUSTERS

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

Calura, F.; Romano, D.; D’Ercole, A.

2015-11-20

Globular clusters (GCs) are considerably more complex structures than previously thought, harboring at least two stellar generations that present clearly distinct chemical abundances. Scenarios explaining the abundance patterns in GCs mostly assume that originally the clusters had to be much more massive than today, and that the second generation of stars originates from the gas shed by stars of the first generation (FG). The lack of metallicity spread in most GCs further requires that the supernova-enriched gas ejected by the FG is completely lost within ∼30 Myr, a hypothesis never tested by means of three-dimensional hydrodynamic simulations. In this paper,more » we use 3D hydrodynamic simulations including stellar feedback from winds and supernovae, radiative cooling and self-gravity to study whether a realistic distribution of OB associations in a massive proto-GC of initial mass M{sub tot} ∼ 10{sup 7} M{sub ⊙} is sufficient to expel its entire gas content. Our numerical experiment shows that the coherence of different associations plays a fundamental role: as the bubbles interact, distort, and merge, they carve narrow tunnels that reach deeper and deeper toward the innermost cluster regions, and through which the gas is able to escape. Our results indicate that after 3 Myr, the feedback from stellar winds is responsible for the removal of ∼40% of the pristine gas, and that after 14 Myr, 99% of the initial gas mass has been removed.« less

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.

A Low Mass for Mars from Jupiter's Early Gas-Driven Migration

NASA Technical Reports Server (NTRS)

Walsh, Kevin J.; Morbidelli, Alessandro; Raymond, Sean N.; O'Brien, David P.; Mandell, Avi M.

2011-01-01

Jupiter and Saturn formed in a few million years from a gas-dominated protoplanetary disk, and were susceptible to gas-driven migration of their orbits on timescales of only approximately 100,000 years. Hydrodynamic simulations show that these giant planets can undergo a two-stage, inward-then-outward, migration. The terrestrial planets finished accreting much later and their characteristics, including Mars' small mass, are best reproduced by starting from a planetesimal disk with an outer edge at about one astronomical unit from the Sun (1 AU is the Earth-Sun distance). Here we report simulations of the early Solar System that show how the inward migration of Jupiter to 1.5 AU, and its subsequent outward migration, lead to a planetesimal disk truncated at 1 AU; the terrestrial planets then form from this disk over the next 30-50 million years, with an Earth/Mars mass ratio consistent with observations. Scattering by Jupiter initially empties but then repopulates the asteroid belt, with inner-belt bodies originating between 1 and 3 AU and outer-belt bodies originating between and beyond the giant planets. This explains the significant compositional differences across the asteroid belt. The key aspect missing from previous models of terrestrial planet formation is the substantial radial migration of the giant planets, which suggests that their behaviour is more similar to that inferred for extrasolar planets than previously thought.

Finding A Planet Through the Dust

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-05-01

Finding planets in the crowded galactic center is a difficult task, but infrared microlensing surveys give us a fighting chance! Preliminary results from such a study have already revealed a new exoplanet lurking in the dust of the galactic bulge.Detection BiasesUKIRT-2017 microlensing survey fields (blue), plotted over a map showing the galactic-plane dust extinction. The location of the newly discovered giant planet is marked with blue crosshairs. [Shvartzvald et al. 2018]Most exoplanets weve uncovered thus far were found either via transits dips in a stars light as the planet passes in front of its host star or via radial velocity wobbles of the star as the orbiting planet tugs on it. These techniques, while highly effective, introduce a selection bias in the types of exoplanets we detect: both methods tend to favor discovery of close-in, large planets orbiting small stars; these systems produce the most easily measurable signals on short timescales.For this reason, microlensing surveys for exoplanets have something new to add to the field.Search for a LensIn gravitational microlensing, we observe a background star as it is briefly magnified by a passing foreground star acting as a lens. If that foreground star hosts a planet, we observe a characteristic shape in the observed brightening of the background star, and the properties of that shape can reveal information about the foreground planet.A diagram of how planets are detected via gravitational microlensing. The detectable planet is in orbit around the foreground lens star. [NASA]This technique for planet detection is unique in its ability to explore untapped regions of exoplanet parameter space with microlensing, we can survey for planets around all different types of stars (rather than primarily small, dim ones), planets of all masses near the further-out snowlines where gas and ice giants are likely to form, and even free-floating planets.In a new study led by a Yossi Shvartzvald, a NASA postdoctoral