Sample records for circumstellar habitable zones

  1. Detectability of Earth-like Planets in Circumstellar Habitable Zones of Binary Star Systems with Sun-like Components

    E-print Network

    Eggl, Siegfried; Pilat-Lohinger, Elke

    2012-01-01

    Given the considerable percentage of stars that are members of binaries or stellar multiples in the Solar neighborhood, it is expected that many of these binaries host planets, possibly even habitable ones. The discovery of a terrestrial planet in the alpha Centauri system supports this notion. Due to the potentially strong gravitational interaction that an Earth-like planet may experience in such systems, classical approaches to determining habitable zones, especially in close S-Type binary systems, can be rather inaccurate. Recent progress in this field, however, allows to identify regions around the star permitting permanent habitability. While the discovery of alpha Cen Bb has shown that terrestrial planets can be detected in solar-type binary stars using current observational facilities, it remains to be shown whether this is also the case for Earth analogues in habitable zones. We provide analytical expressions for the maximum and RMS values of radial velocity and astrometric signals, as well as transit...

  2. The habitable zone and extreme planetary orbits.

    PubMed

    Kane, Stephen R; Gelino, Dawn M

    2012-10-01

    The habitable zone for a given star describes the range of circumstellar distances from the star within which a planet could have liquid water on its surface, which depends upon the stellar properties. Here we describe the development of the habitable zone concept, its application to our own solar system, and its subsequent application to exoplanetary systems. We further apply this to planets in extreme eccentric orbits and show how they may still retain life-bearing properties depending upon the percentage of the total orbit which is spent within the habitable zone. Key Words: Extrasolar planets-Habitable zone-Astrobiology. PMID:23035897

  3. The Habitable Zone and Extreme Planetary Orbits

    E-print Network

    Kane, Stephen R

    2012-01-01

    The Habitable Zone for a given star describes the range of circumstellar distances from the star within which a planet could have liquid water on its surface, which depends upon the stellar properties. Here we describe the development of the Habitable Zone concept, its application to our own Solar System, and its subsequent application to exoplanetary systems. We further apply this to planets in extreme eccentric orbits and show how they may still retain lifebearing properties depending upon the percentage of the total orbit which is spent within the Habitable Zone.

  4. The Habitable Zone

    NSDL National Science Digital Library

    2008-03-26

    This illustration is an approximate representation of the planets in our solar system and their relation to what scientists call The Habitable Zone. The planet distances from the sun are measured in Astronomical Units (AU) and are not to scale.

  5. Habitable zone limits for dry planets.

    PubMed

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

    2011-06-01

    Most discussion of habitable planets has focused on Earth-like planets with globally abundant liquid water. For an "aqua planet" like Earth, the surface freezes if far from its sun, and the water vapor greenhouse effect runs away if too close. Here we show that "land planets" (desert worlds with limited surface water) have wider habitable zones than aqua planets. For planets at the inner edge of the habitable zone, a land planet has two advantages over an aqua planet: (i) the tropics can emit longwave radiation at rates above the traditional runaway limit because the air is unsaturated and (ii) the dry air creates a dry stratosphere that limits hydrogen escape. At the outer limits of the habitable zone, the land planet better resists global freezing because there is less water for clouds, snow, and ice. Here we describe a series of numerical experiments using a simple three-dimensional global climate model for Earth-sized planets. Other things (CO(2), rotation rate, surface pressure) unchanged, we found that liquid water remains stable at the poles of a low-obliquity land planet until net insolation exceeds 415 W/m(2) (170% that of modern Earth), compared to 330 W/m(2) (135%) for the aqua planet. At the outer limits, we found that a low-obliquity land planet freezes at 77%, while the aqua planet freezes at 90%. High-obliquity land and aqua planets freeze at 58% and 72%, respectively, with the poles offering the last refuge. We show that it is possible that, as the Sun brightens, an aqua planet like Earth can lose most of its hydrogen and become a land planet without first passing through a sterilizing runaway greenhouse. It is possible that Venus was a habitable land planet as recently as 1 billion years ago. PMID:21707386

  6. Radiative habitable zones in martian polar environments

    NASA Astrophysics Data System (ADS)

    Córdoba-Jabonero, Carmen; Zorzano, María-Paz; Selsis, Franck; Patel, Manish R.; Cockell, Charles S.

    2005-06-01

    The biologically damaging solar ultraviolet (UV) radiation (quantified by the DNA-weighted dose) reaches the martian surface in extremely high levels. Searching for potentially habitable UV-protected environments on Mars, we considered the polar ice caps that consist of a seasonally varying CO 2 ice cover and a permanent H 2O ice layer. It was found that, though the CO 2 ice is insufficient by itself to screen the UV radiation, at ˜1 m depth within the perennial H 2O ice the DNA-weighted dose is reduced to terrestrial levels. This depth depends strongly on the optical properties of the H 2O ice layers (for instance snow-like layers). The Earth-like DNA-weighted dose and Photosynthetically Active Radiation (PAR) requirements were used to define the upper and lower limits of the northern and southern polar Radiative Habitable Zone (RHZ) for which a temporal and spatial mapping was performed. Based on these studies we conclude that photosynthetic life might be possible within the ice layers of the polar regions. The thickness varies along each martian polar spring and summer between ˜1.5 and 2.4 m for H 2O ice-like layers, and a few centimeters for snow-like covers. These martian Earth-like radiative habitable environments may be primary targets for future martian astrobiological missions. Special attention should be paid to planetary protection, since the polar RHZ may also be subject to terrestrial contamination by probes.

  7. Extrasolar Trojan Planets close to Habitable Zones

    E-print Network

    R. Dvorak; E. Pilat-Lohinger; R. Schwarz; F. Freistetter

    2004-08-04

    We investigate the stability regions of hypothetical terrestrial planets around the Lagrangian equilibrium points L4 and L5 in some specific extrasolar planetary systems. The problem of their stability can be treated in the framework of the restricted three body problem where the host star and a massive Jupiter-like planet are the primary bodies and the terrestrial planet is regarded as being massless. From these theoretical investigations one cannot determine the extension of the stable zones around the equilibrium points. Using numerical experiments we determined their largeness for three test systems chosen from the table of the know extrasolar planets, where a giant planet is moving close to the so-called habitable zone around the host star in low eccentric orbits. The results show the dependence of the size and structure of this region, which shrinks significantly with the eccentricity of the known gas giant.

  8. Stabilizing Cloud Feedback Dramatically Expands the Habitable Zone of Tidally Locked Planets

    E-print Network

    Yang, Jun; Abbot, Dorian S

    2013-01-01

    The habitable zone (HZ) is the circumstellar region where a planet can sustain surface liquid water. Searching for terrestrial planets in the HZ of nearby stars is the stated goal of ongoing and planned extrasolar planet surveys. Previous estimates of the inner edge of the HZ were based on one-dimensional radiative-convective models. The most serious limitation of these models is the inability to predict cloud behavior. Here we use global climate models with sophisticated cloud schemes to show that due to a stabilizing cloud feedback, tidally locked planets can be habitable at twice the stellar flux found by previous studies. This dramatically expands the HZ and roughly doubles the frequency of habitable planets orbiting red dwarf stars. At high stellar flux, strong convection produces thick water clouds near the substellar location that greatly increase the planetary albedo and reduce surface temperatures. Higher insolation produces stronger substellar convection and therefore higher albedo, making this phen...

  9. 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.

  10. What Can The Habitable Zone Gallery Do for You?

    NASA Astrophysics Data System (ADS)

    Gelino, Dawn M.; Kane, Stephen R.

    2014-06-01

    The Habitable Zone Gallery (www.hzgallery.org) has been online since August 2011 as a service to the exoplanet community to provide Habitable Zone (HZ) information for each of the exoplanetary systems with known planetary orbital parameters. The service includes a sortable table, a plot with the period and eccentricity of each of the planets with respect to their time spent in the HZ, a gallery of known systems which plots the orbits and the location of the HZ with respect to those orbits, and orbital movies. Recently, we have added new features including: implementation of both conservative and optimistic HZs, more user-friendly table and movies, movies for circumbinary planets, and a count of planets whose orbits lie entirely within the system’s HZ. Here we discuss various educational and scientific applications of the site such as target selection, exploring planets with eccentric or circumbinary orbits, and investigating habitability.

  11. Comparable Habitable Zones of Stars - Duration: 25 seconds.

    NASA Video Gallery

    The habitable zone is the distance from a star where one can have liquid water on the surface of a planet. If a planet is too close to its parent star, it will be too hot and water would have evapo...

  12. CANDIDATE PLANETS IN THE HABITABLE ZONES OF KEPLER STARS

    SciTech Connect

    Gaidos, Eric, E-mail: gaidos@hawaii.edu [Department of Geology and Geophysics, University of Hawai'i at Manoa, Honolulu, HI 96822 (United States)

    2013-06-20

    A key goal of the Kepler mission is the discovery of Earth-size transiting planets in ''habitable zones'' where stellar irradiance maintains a temperate climate on an Earth-like planet. Robust estimates of planet radius and irradiance require accurate stellar parameters, but most Kepler systems are faint, making spectroscopy difficult and prioritization of targets desirable. The parameters of 2035 host stars were estimated by Bayesian analysis and the probabilities p{sub HZ} that 2738 candidate or confirmed planets orbit in the habitable zone were calculated. Dartmouth Stellar Evolution Program models were compared to photometry from the Kepler Input Catalog, priors for stellar mass, age, metallicity and distance, and planet transit duration. The analysis yielded probability density functions for calculating confidence intervals of planet radius and stellar irradiance, as well as p{sub HZ}. Sixty-two planets have p{sub HZ} > 0.5 and a most probable stellar irradiance within habitable zone limits. Fourteen of these have radii less than twice the Earth; the objects most resembling Earth in terms of radius and irradiance are KOIs 2626.01 and 3010.01, which orbit late K/M-type dwarf stars. The fraction of Kepler dwarf stars with Earth-size planets in the habitable zone ({eta}{sub Circled-Plus }) is 0.46, with a 95% confidence interval of 0.31-0.64. Parallaxes from the Gaia mission will reduce uncertainties by more than a factor of five and permit definitive assignments of transiting planets to the habitable zones of Kepler stars.

  13. Stellar activity mimics a habitable-zone planet around Kapteyn's star

    E-print Network

    Robertson, Paul; Mahadevan, Suvrath

    2015-01-01

    Kapteyn's star is an old M subdwarf believed to be a member of the Galactic halo population of stars. A recent study has claimed the existence of two super-Earth planets around the star based on radial velocity (RV) observations. The innermost of these candidate planets--Kapteyn b (P = 48 days)--resides within the circumstellar habitable zone. Given recent progress in understanding the impact of stellar activity in detecting planetary signals, we have analyzed the observed HARPS data for signatures of stellar activity. We find that while Kapteyn's star is photometrically very stable, a suite of spectral activity indices reveals a large-amplitude rotation signal, and we determine the stellar rotation period to be 143 days. The spectral activity tracers are strongly correlated with the purported RV signal of "planet b," and the 48-day period is an integer fraction (1/3) of the stellar rotation period. We conclude that Kapteyn b is not a planet in the Habitable Zone, but an artifact of stellar activity.

  14. The Habitable Zones of Pre-main-sequence Stars

    NASA Astrophysics Data System (ADS)

    Ramirez, Ramses M.; Kaltenegger, Lisa

    2014-12-01

    We calculate the pre-main-sequence habitable zone (HZ) for stars of spectral classes F-M. The spatial distribution of liquid water and its change during the pre-main-sequence phase of protoplanetary systems is important for understanding how planets become habitable. Such worlds are interesting targets for future missions because the coolest stars could provide habitable conditions for up to 2.5 billion years post-accretion. Moreover, for a given star type, planetary systems are more easily resolved because of higher pre-main-sequence stellar luminosities, resulting in larger planet-star separation for cool stars than is the case for the traditional main-sequence (MS) HZ. We use one-dimensional radiative-convective climate and stellar evolutionary models to calculate pre-main-sequence HZ distances for F1-M8 stellar types. We also show that accreting planets that are later located in the traditional MS HZ orbiting stars cooler than a K5 (including the full range of M stars) receive stellar fluxes that exceed the runaway greenhouse threshold, and thus may lose substantial amounts of water initially delivered to them. We predict that M-star planets need to initially accrete more water than Earth did, or, alternatively, have additional water delivered later during the long pre-MS phase to remain habitable. Our findings are also consistent with recent claims that Venus lost its water during accretion.

  15. Toward the minimum inner edge distance of the habitable zone

    SciTech Connect

    Zsom, Andras; Seager, Sara; De Wit, Julien; Stamenkovi?, Vlada, E-mail: zsom@mit.edu [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2013-12-01

    We explore the minimum distance from a host star where an exoplanet could potentially be habitable in order not to discard close-in rocky exoplanets for follow-up observations. We find that the inner edge of the Habitable Zone for hot desert worlds can be as close as 0.38 AU around a solar-like star, if the greenhouse effect is reduced (?1% relative humidity) and the surface albedo is increased. We consider a wide range of atmospheric and planetary parameters such as the mixing ratios of greenhouse gases (water vapor and CO{sub 2}), surface albedo, pressure, and gravity. Intermediate surface pressure (?1-10 bars) is necessary to limit water loss and to simultaneously sustain an active water cycle. We additionally find that the water loss timescale is influenced by the atmospheric CO{sub 2} level, because it indirectly influences the stratospheric water mixing ratio. If the CO{sub 2} mixing ratio of dry planets at the inner edge is smaller than 10{sup –4}, the water loss timescale is ?1 billion years, which is considered here too short for life to evolve. We also show that the expected transmission spectra of hot desert worlds are similar to an Earth-like planet. Therefore, an instrument designed to identify biosignature gases in an Earth-like atmosphere can also identify similarly abundant gases in the atmospheres of dry planets. Our inner edge limit is closer to the host star than previous estimates. As a consequence, the occurrence rate of potentially habitable planets is larger than previously thought.

  16. Stellar Activity Mimics a Habitable-zone Planet around Kapteyn's Star

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Roy, Arpita; Mahadevan, Suvrath

    2015-06-01

    Kapteyn’s star is an old M subdwarf believed to be a member of the Galactic halo population of stars. A recent study has claimed the existence of two super-Earth planets around the star based on radial velocity (RV) observations. The innermost of these candidate planets—Kapteyn b (P = 48 days)—resides within the circumstellar habitable zone (HZ). Given recent progress in understanding the impact of stellar activity in detecting planetary signals, we have analyzed the observed HARPS data for signatures of stellar activity. We find that while Kapteyn’s star is photometrically very stable, a suite of spectral activity indices reveal a large-amplitude rotation signal, and we determine the stellar rotation period to be 143 days. The spectral activity tracers are strongly correlated with the purported RV signal of “planet b,” and the 48-day period is an integer fraction (1/3) of the stellar rotation period. We conclude that Kapteyn b is not a planet in the HZ, but an artifact of stellar activity.

  17. Habitable Zones around Main-sequence Stars: New Estimates

    NASA Astrophysics Data System (ADS)

    Kopparapu, Ravi Kumar; Ramirez, Ramses; Kasting, James F.; Eymet, Vincent; Robinson, Tyler D.; Mahadevan, Suvrath; Terrien, Ryan C.; Domagal-Goldman, Shawn; Meadows, Victoria; Deshpande, Rohit

    2013-03-01

    Identifying terrestrial planets in the habitable zones (HZs) of other stars is one of the primary goals of ongoing radial velocity (RV) and transit exoplanet surveys and proposed future space missions. Most current estimates of the boundaries of the HZ are based on one-dimensional (1D), cloud-free, climate model calculations by Kasting et al. However, this model used band models that were based on older HITRAN and HITEMP line-by-line databases. The inner edge of the HZ in the Kasting et al. model was determined by loss of water, and the outer edge was determined by the maximum greenhouse provided by a CO2 atmosphere. A conservative estimate for the width of the HZ from this model in our solar system is 0.95-1.67 AU. Here an updated 1D radiative-convective, cloud-free climate model is used to obtain new estimates for HZ widths around F, G, K, and M stars. New H2O and CO2 absorption coefficients, derived from the HITRAN 2008 and HITEMP 2010 line-by-line databases, are important improvements to the climate model. According to the new model, the water-loss (inner HZ) and maximum greenhouse (outer HZ) limits for our solar system are at 0.99 and 1.70 AU, respectively, suggesting that the present Earth lies near the inner edge. Additional calculations are performed for stars with effective temperatures between 2600 and 7200 K, and the results are presented in parametric form, making them easy to apply to actual stars. The new model indicates that, near the inner edge of the HZ, there is no clear distinction between runaway greenhouse and water-loss limits for stars with T eff <~ 5000 K, which has implications for ongoing planet searches around K and M stars. To assess the potential habitability of extrasolar terrestrial planets, we propose using stellar flux incident on a planet rather than equilibrium temperature. This removes the dependence on planetary (Bond) albedo, which varies depending on the host star's spectral type. We suggest that conservative estimates of the HZ (water-loss and maximum greenhouse limits) should be used for current RV surveys and Kepler mission to obtain a lower limit on ??, so that future flagship missions like TPF-C and Darwin are not undersized. Our model does not include the radiative effects of clouds; thus, the actual HZ boundaries may extend further in both directions than the estimates just given.

  18. TERRESTRIAL, HABITABLE-ZONE EXOPLANET FREQUENCY FROM KEPLER

    SciTech Connect

    Traub, Wesley A., E-mail: wtraub@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-01-20

    Data from Kepler's first 136 days of operation are analyzed to determine the distribution of exoplanets with respect to radius, period, and host-star spectral type. The analysis is extrapolated to estimate the percentage of terrestrial, habitable-zone (HZ) exoplanets. The Kepler census is assumed to be complete for bright stars (magnitude <14.0) having transiting planets >0.5 Earth radius and periods <42 days. It is also assumed that the size distribution of planets is independent of orbital period and that there are no hidden biases in the data. Six significant statistical results are found: there is a paucity of small planet detections around faint target stars, probably an instrumental effect; the frequency of mid-size planet detections is independent of whether the host star is bright or faint; there are significantly fewer planets detected with periods <3 days, compared to longer periods, almost certainly an astrophysical effect; the frequency of all planets in the population with periods <42 days is 29%, broken down as terrestrials 9%, ice giants 18%, and gas giants 3%; the population has a planet frequency with respect to period which follows a power-law relation dN/dP {approx} P{sup {beta}-1}, with {beta} {approx_equal} 0.71 {+-} 0.08; and an extrapolation to longer periods gives the frequency of terrestrial planets in the HZs of FGK stars as {eta}{sub Circled-Plus} {approx_equal} (34 {+-} 14)%. Thus about one-third of FGK stars are predicted to have at least one terrestrial, HZ planet.

  19. Habitability of P-type Planet-Hosting Binary Star Systems: Calculating Habitable Zone for Known Circumbinary Planets

    NASA Astrophysics Data System (ADS)

    Haghighipour, Nader; Kaltenegger, L.

    2012-10-01

    We have developed a detailed approach to determine the location of the habitable zone around a planet-hosting binary star system (P-type). Our approach takes into account the interaction between the incoming radiation from a star and the atmosphere of an Earth-like planet, and accounts for the fraction of the insolation from each star of the binary that contributes to the total flux received at the top of the planet’s atmosphere. Since these interactions depend on the spectral energy distribution of each star, we have considered different stellar spectral types for the primary and secondary of the binary, and included different cloud fractions for the atmosphere of the planet. By combining dynamical simulations with the influence of the additional flux, we have derived the binary’s habitable zone as a function of its semimajor axis, eccentricity, and stellar energy distribution. Our results suggest that in most cases in circumbinary (P-type) planetary systems, the flux of the two stars at the location of the planet can be added, and the system can be regarded as a more luminous single star. However, if the stellar separation of the binary is small, the eccentricities of the binary and planet can play an important role in the locations of the system’s habitable zone. We have applied our model to the currently known planet-hosting circumbinary systems detected by Kepler and have determined the possibility of the existence and detection of Earth-like planets in their habitable zones. We present the details of our model and discuss its applications to different binary-planetary systems.

  20. Habitable Evaporated Cores: Converting Mini-Neptunes into Super- Earths in the Habitable Zone of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Luger, R.; Barnes, R.; Lopez, E.; Fortney, J.; Jackson, B.; Meadows, V.

    2014-03-01

    The low masses and luminosities of M dwarfs make them ideal targets for thedetection of terrestrial planets in the habitable zone (HZ). However, studies suggest that planets formed only from material in the HZs of these stars are likely to be small and dry (e.g., Raymond et al. 2007). As a result, many of the planets that will be detected in the HZ by upcoming missions are probably the result of migration from beyond the snow line, and may have formed with large H/He envelopes (so-called mini-Neptunes). Here we show that photoevaporation and Roche lobe overflow of these planets can lead to the complete loss of their gaseous envelopes, transforming them into potentially habitable worlds, which we call “habitable evaporated cores”. We couple the planet structure models of Lopez et al. (2012) with a simple Roche lobe overflow scheme and the X-ray/extreme ultraviolet (XUV)-induced mass loss model of Erkaev et al. (2007). We also couple the orbital effects of anisotropic mass loss with tidal evolution and show that this coupling can lead to orbital changes that significantly enhance the mass loss rate.Habitable evaporated cores are most likely to form from small mini-Neptunes (?4 M?) with large (?50%) initial hydrogen fractions orbiting M4 stars and later. Given the steep decrease in stellar XUV flux with time (Ribas et al. 2005), mass loss is negligible after ~1 Gyr, at which point a habitable evaporated core is capable of degassing and maintaining a secondary atmosphere. This process may be the dominant formation mechanism for habitable planets around M dwarfs, and may be discovered by missions such as TESS and PLATO.

  1. Moon Radius Limits for a Habitable Zone Kepler Transiting Planet Candidate

    NASA Astrophysics Data System (ADS)

    Lewis, K.

    2014-04-01

    In addition to planets being potentially habitable bodies, moons, both inside and beyond the habitable zones of their host star may also be suitable sites for life. One promising method to detect such habitable moons is the through the transit technique, in particular using the high quality, long baseline Kepler dataset. Planets in the habitable zone of Sun-like stars tend to have long orbital periods and thus exhibit few transits within the 3.5 year Kepler mission. In addition, candidate planets are more likely to be confirmed if they are in multiple systems where planetary perturbations may make moon detection through transit timing very challenging. As a result we focus on the direct detection moon technique first described by Sartoretti and Schneider (1999), which involves searching and fitting the extra dip due to a moon in each transit light curve directly. To test this method in the presence of realistic photometric noise, we developed a Kepler light curve simulator that generates noisy light curves corresponding to physically consistent planet-moon systems. Using this program we calculate sets of unique light curve realisations for a Kepler candidate (KOI3681.01) in the habitable zone of a Sun-like star, for a grid of physically realistic moon radii and semi-major axes, and process them using our detection code. This allows us to robustly place constraints on potentially habitable terrestrial moons thus demonstrating the power of this approach.

  2. INDICATION OF INSENSITIVITY OF PLANETARY WEATHERING BEHAVIOR AND HABITABLE ZONE TO SURFACE LAND FRACTION

    SciTech Connect

    Abbot, Dorian S.; Ciesla, Fred J. [Department of the Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637 (United States); Cowan, Nicolas B., E-mail: abbot@uchicago.edu [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2131 Tech Drive, Evanston, IL 60208 (United States)

    2012-09-10

    It is likely that unambiguous habitable zone terrestrial planets of unknown water content will soon be discovered. Water content helps determine surface land fraction, which influences planetary weathering behavior. This is important because the silicate-weathering feedback determines the width of the habitable zone in space and time. Here a low-order model of weathering and climate, useful for gaining qualitative understanding, is developed to examine climate evolution for planets of various land-ocean fractions. It is pointed out that, if seafloor weathering does not depend directly on surface temperature, there can be no weathering-climate feedback on a waterworld. This would dramatically narrow the habitable zone of a waterworld. Results from our model indicate that weathering behavior does not depend strongly on land fraction for partially ocean-covered planets. This is powerful because it suggests that previous habitable zone theory is robust to changes in land fraction, as long as there is some land. Finally, a mechanism is proposed for a waterworld to prevent complete water loss during a moist greenhouse through rapid weathering of exposed continents. This process is named a 'waterworld self-arrest', and it implies that waterworlds can go through a moist greenhouse stage and end up as planets like Earth with partial ocean coverage. This work stresses the importance of surface and geologic effects, in addition to the usual incident stellar flux, for habitability.

  3. Habitable evaporated cores: transforming mini-Neptunes into super-Earths in the habitable zones of M dwarfs.

    PubMed

    Luger, R; Barnes, R; Lopez, E; Fortney, J; Jackson, B; Meadows, V

    2015-01-01

    We show that photoevaporation of small gaseous exoplanets ("mini-Neptunes") in the habitable zones of M dwarfs can remove several Earth masses of hydrogen and helium from these planets and transform them into potentially habitable worlds. We couple X-ray/extreme ultraviolet (XUV)-driven escape, thermal evolution, tidal evolution, and orbital migration to explore the types of systems that may harbor such "habitable evaporated cores" (HECs). We find that HECs are most likely to form from planets with ?1 M? solid cores with up to about 50% H/He by mass, though whether or not a given mini-Neptune forms a HEC is highly dependent on the early XUV evolution of the host star. As terrestrial planet formation around M dwarfs by accumulation of local material is likely to form planets that are small and dry, evaporation of small migrating mini-Neptunes could be one of the dominant formation mechanisms for volatile-rich Earths around these stars. PMID:25590532

  4. Habitable Evaporated Cores: Transforming Mini-Neptunes into Super-Earths in the Habitable Zones of M Dwarfs

    NASA Astrophysics Data System (ADS)

    Luger, R.; Barnes, R.; Lopez, E.; Fortney, J.; Jackson, B.; Meadows, V.

    2015-01-01

    We show that photoevaporation of small gaseous exoplanets ("mini-Neptunes") in the habitable zones of M dwarfs can remove several Earth masses of hydrogen and helium from these planets and transform them into potentially habitable worlds. We couple X-ray/extreme ultraviolet (XUV)-driven escape, thermal evolution, tidal evolution and orbital migration to explore the types of systems that may harbor such "habitable evaporated cores" (HECs). We find that HECs are most likely to form from planets with $\\sim 1 M_\\oplus$ solid cores with up to about 50% H/He by mass, though whether or not a given mini-Neptune forms a HEC is highly dependent on the early XUV evolution of the host star. As terrestrial planet formation around M dwarfs by accumulation of local material is likely to form planets that are small and dry, evaporation of small migrating mini-Neptunes could be one of the dominant formation mechanisms for volatile-rich Earths around these stars.

  5. Stability of Earth-Mass Planets in the Habitable Zones of Extrasolar Planetary Systems

    E-print Network

    Bjørnstad, Ottar Nordal

    Stability of Earth-Mass Planets in the Habitable Zones of Extrasolar Planetary Systems Dr. Ravi Kumar Kopparapu Dept. of Geosciences, College of Earth and Mineral Science Over 500 planets orbiting and Saturn but in the last couple of years several "super-earths", planets with mass less than 10 times Earth

  6. Exomoon habitability constrained by illumination and tidal heating

    E-print Network

    Heller, René

    2012-01-01

    The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet, and hence experience days much shorter than their orbital period around the star, and have seasons - all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circum-planetary "habit...

  7. TERRESTRIAL PLANET FORMATION AROUND THE CIRCUMBINARY HABITABLE ZONE: INWARD MIGRATION IN THE PLANETESIMAL SWARM

    SciTech Connect

    Gong Yanxiang; Zhou Jilin; Xie Jiwei, E-mail: yxgong@nju.edu.cn, E-mail: zhoujl@nju.edu.cn [Department of Astronomy and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210093 (China)

    2013-01-20

    According to the core accretion theory, circumbinary embryos can form only beyond a critical semimajor axis (CSMA). However, due to the relatively high density of solid materials in the inner disk, a significant amount of small planetesimals must exist in the inner zone when embryos form outside this CSMA. Thus, embryo migration induced by the planetesimal swarm is possible after gas disk depletion. Through numerical simulations, we found that (1) the scattering-driven inward migration of embryos is robust and planets can form in the habitable zone if we adopt a mass distribution of an MMSN-like disk; (2) the total mass of the planetesimals in the inner region and continuous embryo-embryo scattering are two key factors that cause significant embryo migrations; and (3) the scattering-driven migration of embryos is a natural water-delivery mechanism. We propose that planet detections should focus on the close binary with its habitable zone near CSMA.

  8. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars

    NASA Astrophysics Data System (ADS)

    Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

    2015-02-01

    Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets’ rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere.

  9. Asynchronous rotation of Earth-like planets in the habitable zone of lower-mass stars

    E-print Network

    Leconte, Jérémy; Menou, Kristen; Murray, Norman

    2015-01-01

    Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets' rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than 0.5-0.7Msun. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere.

  10. TRANSIT SURVEYS FOR EARTHS IN THE HABITABLE ZONES OF WHITE DWARFS

    SciTech Connect

    Agol, Eric, E-mail: agol@uw.edu [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States)] [Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106 (United States)

    2011-04-20

    To date the search for habitable Earth-like planets has primarily focused on nuclear burning stars. I propose that this search should be expanded to cool white dwarf stars that have expended their nuclear fuel. I define the continuously habitable zone of white dwarfs and show that it extends from {approx}0.005 to 0.02 AU for white dwarfs with masses from 0.4 to 0.9 M{sub sun}, temperatures less than {approx}10{sup 4} K, and habitable durations of at least 3 Gyr. As they are similar in size to Earth, white dwarfs may be deeply eclipsed by terrestrial planets that orbit edge-on, which can easily be detected with ground-based telescopes. If planets can migrate inward or reform near white dwarfs, I show that a global robotic telescope network could carry out a transit survey of nearby white dwarfs placing interesting constraints on the presence of habitable Earths. If planets were detected, I show that the survey would favor detection of planets similar to Earth: similar size, temperature, and rotation period, and host star temperatures similar to the Sun. The Large Synoptic Survey Telescope could place even tighter constraints on the frequency of habitable Earths around white dwarfs. The confirmation and characterization of these planets might be carried out with large ground and space telescopes.

  11. Water Planets in the Habitable Zone: Atmospheric Chemistry, Observable Features, and the case of Kepler-62e and -62f

    E-print Network

    Kaltenegger, L; Rugheimer, S

    2013-01-01

    Water planets in the habitable zone are expected to have distinct geophysics and geochemistry of their surfaces and atmospheres. We explore these properties motivated by two key questions: whether such planets could provide habitable conditions and whether they exhibit discernable spectral features that distinguish a water planet from a rocky Earth-like planet. We show that the recently discovered planets Kepler-62e and -62f are the first viable candidates for habitable zone water planet. We use these planets as test cases for discussing those differences in detail. We generate atmospheric spectral models and find that potentially habitable water planets show a distinctive spectral fingerprint in transit depending on their position in the habitable zone.

  12. Exomoon Habitability Constrained by Illumination and Tidal Heating

    PubMed Central

    2013-01-01

    Abstract The detection of moons orbiting extrasolar planets (“exomoons”) has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary “habitable edge.” We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than 10 planetary radii, then this could indicate the presence of a habitable moon. Key Words: Astrobiology—Extrasolar planets—Habitability—Habitable zone—Tides. Astrobiology 13, 18–46. PMID:23305357

  13. MOA-2011-BLG-293LB: First microlensing planet possibly in the habitable zone

    SciTech Connect

    Batista, V.; Gould, A.; Yee, J. C.; Gaudi, B. S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Beaulieu, J.-P. [Institut d'Astrophysique de Paris, 98 Bis Boulevard Arago, F-75014 Paris (France); Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556-5670 (United States); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Sumi, T. [Department of Earth and Space Science, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Udalski, A., E-mail: virginie@astronomy.ohio-state.edu, E-mail: gould@astronomy.ohio-state.edu, E-mail: jyee@astronomy.ohio-state.edu, E-mail: beaulieu@iap.fr, E-mail: bennett@nd.edu, E-mail: afukui@oao.nao.ac.jp, E-mail: sumi@ess.sci.osaka-u.ac.jp, E-mail: udalski@astrouw.edu.pl [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

    2014-01-01

    We used Keck adaptive optics observations to identify the first planet discovered by microlensing to lie in or near the habitable zone, i.e., at projected separation r = 1.1 ± 0.1 AU from its M{sub L} = 0.86 ± 0.06 M {sub ?} host, being the highest microlensing mass definitely identified. The planet has a mass m{sub p} = 4.8 ± 0.3 M {sub Jup}, and could in principle have habitable moons. This is also the first planet to be identified as being in the Galactic bulge with good confidence: D{sub L} = 7.72 ± 0.44 kpc. The planet/host masses and distance were previously not known, but only estimated using Bayesian priors based on a Galactic model. These estimates had suggested that the planet might be a super-Jupiter orbiting an M dwarf, a very rare class of planets. We obtained high-resolution JHK images using Keck adaptive optics to detect the lens and so test this hypothesis. We clearly detect light from a G dwarf at the position of the event, and exclude all interpretations other than that this is the lens with high confidence (95%), using a new astrometric technique. The calibrated magnitude of the planet host star is H{sub L} = 19.16 ± 0.13. We infer the following probabilities for the three possible orbital configurations of the gas giant planet: 53% to be in the habitable zone, 35% to be near the habitable zone, and 12% to be beyond the snow line, depending on the atmospherical conditions and the uncertainties on the semimajor axis.

  14. Impact flux of asteroids and water transport to the habitable zone in binary star systems

    E-print Network

    Bancelin, D; Eggl, S; Dvorak, R

    2015-01-01

    By now, observations of exoplanets have found more than 50 binary star systems hosting 71 planets. We expect these numbers to increase as more than 70% of the main sequence stars in the solar neighborhood are members of binary or multiple systems. The planetary motion in such systems depends strongly on both the parameters of the stellar system (stellar separation and eccentricity) and the architecture of the planetary system (number of planets and their orbital behaviour). In case a terrestrial planet moves in the so-called habitable zone (HZ) of its host star, the habitability of this planet depends on many parameters. A crucial factor is certainly the amount of water. We investigate in this work the transport of water from beyond the snow-line to the HZ in a binary star system and compare it to a single star system.

  15. THERMAL EVOLUTION AND LIFETIME OF INTRINSIC MAGNETIC FIELDS OF SUPER-EARTHS IN HABITABLE ZONES

    SciTech Connect

    Tachinami, C.; Ida, S. [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro, Tokyo 1528551 (Japan); Senshu, H., E-mail: ctchnm@geo.titech.ac.jp [Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Chiba 2750016 (Japan)

    2011-01-10

    We have numerically studied the thermal evolution of different-mass terrestrial planets in habitable zones, focusing on the duration of dynamo activity to generate their intrinsic magnetic fields, which may be one of the key factors in habitability of the planets. In particular, we are concerned with super-Earths, observations of which are rapidly developing. We calculated the evolution of temperature distributions in the planetary interior using Vinet equations of state, the Arrhenius-type formula for mantle viscosity, and the astrophysical mixing-length theory for convective heat transfer modified for mantle convection. After calibrating the model with terrestrial planets in the solar system, we apply it for 0.1-10 M{sub +} rocky planets with a surface temperature of 300 K (in habitable zones) and Earth-like compositions. With the criterion of heat flux at the core-mantle boundary (CMB), the lifetime of the magnetic fields is evaluated from the calculated thermal evolution. We found that the lifetime slowly increases with planetary mass (M{sub p} ), independent of the initial temperature gap at the CMB ({Delta}T{sub CMB}), but beyond the critical value M{sub c,p} ({approx}O(1) M{sub +}) it abruptly declines from the mantle viscosity enhancement due to the pressure effect. We derived M{sub c,p} as a function of {Delta}T{sub CMB} and a rheological parameter (activation volume, V*). Thus, the magnetic field lifetime of super-Earths with M{sub p} >M{sub p,c} sensitively depends on {Delta}T{sub CMB}, which reflects planetary accretion, and V*, which has uncertainty at very high pressure. More advanced high-pressure experiments and first-principle simulation, as well as planetary accretion simulation, are needed to discuss the habitability of super-Earths.

  16. The Instellation Habitable Zone: Liquid Water Stability on a Single Axis

    NASA Astrophysics Data System (ADS)

    Domagal-Goldman, S. D.; Virtual Planetary Laboratory

    2011-12-01

    The habitable zone is the region around a star for which liquid water might be stable at the surface of a planet. This is roughly defined as orbital distances greater than those for which runaway greenhouses are triggered or water loss via H escape becomes rapid, yet less than those for which snowball Earth conditions are unavoidable. Both of these limits are inherently tied to surface temperature of the planet. Exoplanet observers have often defined habitable zones based on estimates of the equilibrium temperature for a planet, using that as a proxy for surface. However, the calculation of equilibrium temperature requires knowledge of the planet's albedo, which is usually not known. Furthermore, translating a planet's equilibrium temperature into a surface temperature requires estimations of greenhouse and anti-greenhouse effects that are also unknown. Venus presents both of these problems: it has a much-higher albedo than the value commonly assumed for Earth-like exoplanets, and yet its surface temperature is hundreds of degrees higher than its equilibrium temperature. Without knowledge of the albedo of a planet or the magnitude of the greenhouse effect, equilibrium temperature is an unknown quantity that provides unreliable estimates of the surface temperature of a planet. For these reasons, atmospheric modelers have incorporated the effects of albedo and of greenhouse effects into definitions of the habitable zone. Historically, these definitions have been based on the luminosity of the host star and the semi-major axis of the planet's orbit. This has served the community well, as planets are treated and analyzed on a case-by-base basis. However, the presence of two criteria for habitability (semi-major axis and stellar luminosity) presents an impediment to plotting planets in 2-dimensional diagrams that also include geophysical parameters such as planetary radius, mass, or density. While such plots were not previously warranted for ~Earth-sized planets because very few were known, the large number of ~Earth-sized planets currently being discovered by exoplanet surveys such as NASA's Kepler mission increase the need for a single metric that represents the possibility for liquid water to be stable at the surface of a planet. In this presentation, we propose the use of installation - the amount of energy reaching the top of a planet's atmosphere - as a metric for habitability that can be calculated strictly from measured properties and that also allows for display of "surface water stability" on the same chart as other geophysical parameters. The habitable zone presented here is primarily derived from information on planets in our solar system, including knowledge of the history of those planets. We compare this new definition of the habitable zone to traditional ones, and apply it to the February 2011 release of data from the Kepler data set and the database of confirmed extrasolar planets.

  17. A New Paradigm for Habitability in Planetary Systems: the Extremophilic Zone

    NASA Astrophysics Data System (ADS)

    Janot-Pacheco, E., Bernardes, L., Lage, C. A. S.

    2014-03-01

    More than a thousand exoplanets have been discovered so far. Planetary surface temperature may strongly depends on its albedo and geodynamic conditions. We have fed exoplanets from the Encyclopedia database with a comprehensive model of Earth's atmosphere and plate tectonics. As CO2 is the main agent responsible for the greenhouse effect, its partial pressure has been taken as a free parameter to estimate the surface temperature of some known planets. We also investigated the possible presence of "exomoons" belonging to giant planets in the Habitable Zone capable of harbour dynamic stability, to retain an atmosphere and to keep geodynamic activity for long time spans. Biological data on earthly micro-organisms classified as "extremophiles" indicate that such kind of microbial species could dwell on the surface of many exoplanets and exomoons. We thus propose an extension of the mainly astronomically defined "Habitable Zone" concept into the more astrobiologically one, the "Extremophililic Zone", that takes into account other parameters allowing survival of more robust life forms. This contribution comes from an ongoing project developed by a French-Brazilian colaboration in Astrophysics and Biophysics to search for living fingerprints in astrobiologically promising exoplanets.

  18. Planets Formed in Habitable Zones of M Dwarf Stars Probably are Deficient in Volatiles

    E-print Network

    Jack J. Lissauer

    2007-03-22

    Dynamical considerations, presented herein via analytic scalings and numerical experiments, imply that Earth-mass planets accreting in regions that become habitable zones of M dwarf stars form within several million years. Temperatures in these regions during planetary accretion are higher than those encountered by the material that formed the Earth. Collision velocities during and after the prime accretionary epoch are larger than for Earth. These factors suggest that planets orbiting low mass main sequence stars are likely to be either too distant (and thus too cold) for carbon/water based life on their surfaces or have abundances of the required volatiles that are substantially less than on Earth.

  19. GJ 832c: A super-earth in the habitable zone

    E-print Network

    Wittenmyer, R A; Butler, R P; Jones, H R A; Anglada-Escude, Guillem; Horner, Jonathan; Tinney, C G; Marshall, J P; Carter, B D; Bailey, J; Salter, G S; O'Toole, S J; Wright, D; Crane, J D; Schectman, S A; Arriagada, P; Thompson, I; Minniti, D; Jenkins, J S; Diaz, M

    2014-01-01

    We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly-circular 9.4-year orbit. The combination of precise radial-velocity measurements from three telescopes reveals the presence of a planet with a period of 35.68+/-0.03 days and minimum mass (m sin i) of 5.4+/-1.0 Earth masses. GJ 832c moves on a low-eccentricity orbit (e=0.18+/-0.13) towards the inner edge of the habitable zone. However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. Indeed, it is perhaps more likely that GJ 832c is a "super-Venus," featuring significant greenhouse forcing. With an outer giant planet and an interior, potentially rocky planet, the GJ 832 planetary system can be thought of as a miniature version of our own Solar system.

  20. Gj 832c: A super-Earth in the habitable zone

    SciTech Connect

    Wittenmyer, Robert A.; Horner, Jonathan; Tinney, C. G.; Marshall, J. P.; Bailey, J.; Salter, G. S.; Wright, D. [School of Physics, UNSW Australia, Sydney, NSW 2052 (Australia); Tuomi, Mikko; Jones, H. R. A. [Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Butler, R. P.; Arriagada, P. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States); Anglada-Escudé, Guillem [Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, London (United Kingdom); Carter, B. D. [Computational Engineering and Science Research Centre, University of Southern Queensland, Toowoomba, Queensland 4350 (Australia); O'Toole, S. J. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Crane, J. D.; Schectman, S. A.; Thompson, I. [The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Minniti, D. [Institute of Astrophysics, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Jenkins, J. S.; Diaz, M., E-mail: rob@phys.unsw.edu.au [Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Casilla 36-D, Las Condes, Santiago (Chile)

    2014-08-20

    We report the detection of GJ 832c, a super-Earth orbiting near the inner edge of the habitable zone of GJ 832, an M dwarf previously known to host a Jupiter analog in a nearly circular 9.4 yr orbit. The combination of precise radial-velocity measurements from three telescopes reveals the presence of a planet with a period of 35.68 ± 0.03 days and minimum mass (m sin i) of 5.4 ± 1.0 Earth masses. GJ 832c moves on a low-eccentricity orbit (e = 0.18 ± 0.13) toward the inner edge of the habitable zone. However, given the large mass of the planet, it seems likely that it would possess a massive atmosphere, which may well render the planet inhospitable. Indeed, it is perhaps more likely that GJ 832c is a 'super-Venus', featuring significant greenhouse forcing. With an outer giant planet and an interior, potentially rocky planet, the GJ 832 planetary system can be thought of as a miniature version of our own solar system.

  1. A METHOD FOR COUPLING DYNAMICAL AND COLLISIONAL EVOLUTION OF DUST IN CIRCUMSTELLAR DISKS: THE EFFECT OF A DEAD ZONE

    SciTech Connect

    Charnoz, Sebastien; Taillifet, Esther, E-mail: charnoz@cea.fr [Laboratoire AIM, Universite Paris Diderot/CEA/CNRS, 91191 Gif-sur-Yvette Cedex (France)

    2012-07-10

    Dust is a major component of protoplanetary and debris disks as it is the main observable signature of planetary formation. However, since dust dynamics are size-dependent (because of gas drag or radiation pressure) any attempt to understand the full dynamical evolution of circumstellar dusty disks that neglect the coupling of collisional evolution with dynamical evolution is thwarted because of the feedback between these two processes. Here, a new hybrid Lagrangian/Eulerian code is presented that overcomes some of these difficulties. The particles representing 'dust clouds' are tracked individually in a Lagrangian way. This system is then mapped on an Eulerian spatial grid, inside the cells of which the local collisional evolutions are computed. Finally, the system is remapped back in a collection of discrete Lagrangian particles, keeping their number constant. An application example of dust growth in a turbulent protoplanetary disk at 1 AU is presented. First, the growth of dust is considered in the absence of a dead zone and the vertical distribution of dust is self-consistently computed. It is found that the mass is rapidly dominated by particles about a fraction of a millimeter in size. Then the same case with an embedded dead zone is investigated and it is found that coagulation is much more efficient and produces, in a short timescale, 1-10 cm dust pebbles that dominate the mass. These pebbles may then be accumulated into embryo-sized objects inside large-scale turbulent structures as shown recently.

  2. Gliese 581d is the first discovered terrestrial-mass exoplanet in the habitable zone

    E-print Network

    Wordsworth, Robin; Selsis, Franck; Millour, Ehouarn; Charnay, Benjamin; Madeleine, Jean-Baptiste

    2011-01-01

    It has been suggested that the recently discovered exoplanet GJ581d might be able to support liquid water due to its relatively low mass and orbital distance. However, GJ581d receives 35% less stellar energy than Mars and is probably locked in tidal resonance, with extremely low insolation at the poles and possibly a permanent night side. Under such conditions, it is unknown whether any habitable climate on the planet would be able to withstand global glaciation and / or atmospheric collapse. Here we present three-dimensional climate simulations that demonstrate GJ581d will have a stable atmosphere and surface liquid water for a wide range of plausible cases, making it the first confirmed super-Earth (exoplanet of 2-10 Earth masses) in the habitable zone. We find that atmospheres with over 10 bar CO2 and varying amounts of background gas (e.g., N2) yield global mean temperatures above 0 degrees Celsius for both land and ocean-covered surfaces. Based on the emitted IR radiation calculated by the model, we prop...

  3. An Earth-sized planet in the habitable zone of a cool star.

    PubMed

    Quintana, Elisa V; Barclay, Thomas; Raymond, Sean N; Rowe, Jason F; Bolmont, Emeline; Caldwell, Douglas A; Howell, Steve B; Kane, Stephen R; Huber, Daniel; Crepp, Justin R; Lissauer, Jack J; Ciardi, David R; Coughlin, Jeffrey L; Everett, Mark E; Henze, Christopher E; Horch, Elliott; Isaacson, Howard; Ford, Eric B; Adams, Fred C; Still, Martin; Hunter, Roger C; Quarles, Billy; Selsis, Franck

    2014-04-18

    The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star's radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form. PMID:24744370

  4. The galactic habitable zone and the age distribution of complex life in the Milky Way.

    PubMed

    Lineweaver, Charles H; Fenner, Yeshe; Gibson, Brad K

    2004-01-01

    We modeled the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun. PMID:14704421

  5. 55 CANCRI: STELLAR ASTROPHYSICAL PARAMETERS, A PLANET IN THE HABITABLE ZONE, AND IMPLICATIONS FOR THE RADIUS OF A TRANSITING SUPER-EARTH

    SciTech Connect

    Von Braun, Kaspar; Kane, Stephen R.; Ciardi, David R. [NASA Exoplanet Science Institute, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States); Tabetha, S. Boyajian; McAlister, Harold A.; White, Russel [Center for High Angular Resolution Astronomy and Department of Physics and Astronomy, Georgia State University, P. O. Box 4106, Atlanta, GA 30302-4106 (United States); Ten Brummelaar, Theo A.; Schaefer, Gail; Sturmann, Laszlo; Sturmann, Judit; Turner, Nils H.; Farrington, Chris; Goldfinger, P. J. [The CHARA Array, Mount Wilson Observatory, Mount Wilson, CA 91023 (United States); Van Belle, Gerard T. [European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching (Germany); Raymond, Sean N. [Universite de Bordeaux, Observatoire Aquitain des Sciences de l'Univers, 2 rue de l'Observatoire, BP 89, F-33271 Floirac Cedex (France); Lopez-Morales, Mercedes [Institut de Ciencies de L'Espai (CSIC-IEEC), Campus UAB, Facultat Ciencies, Torre C5 parell 2, 08193 Bellaterra, Barcelona (Spain); Ridgway, Stephen T., E-mail: kaspar@caltech.edu [National Optical Astronomy Observatory, P. O. Box 26732, Tucson, AZ 85726-6732 (United States)

    2011-10-10

    The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. The study presented here yields directly determined values for 55 Cnc's stellar astrophysical parameters based on improved interferometry: R = 0.943 {+-} 0.010 R{sub sun}, T{sub EFF} = 5196 {+-} 24 K. We use isochrone fitting to determine 55 Cnc's age to be 10.2 {+-} 2.5 Gyr, implying a stellar mass of 0.905 {+-} 0.015 M{sub sun}. Our analysis of the location and extent of the system's habitable zone (HZ; 0.67-1.32 AU) shows that planet f, with period {approx}260 days and Msin i = 0.155 M{sub Jupiter}, spends the majority of the duration of its elliptical orbit in the circumstellar HZ. Though planet f is too massive to harbor liquid water on any planetary surface, we elaborate on the potential of alternative low-mass objects in planet f's vicinity: a large moon and a low-mass planet on a dynamically stable orbit within the HZ. Finally, our direct value for 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e ({approx}2.05 {+-} 0.15 R{sub +}), which, depending on the planetary mass assumed, implies a bulk density of 0.76 {rho}{sub +} or 1.07 {rho}{sub +}.

  6. Exomoon habitability constrained by illumination and tidal heating.

    PubMed

    Heller, René; Barnes, Rory

    2013-01-01

    The detection of moons orbiting extrasolar planets ("exomoons") has now become feasible. Once they are discovered in the circumstellar habitable zone, questions about their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days much shorter than their orbital period around the star and have seasons, all of which works in favor of habitability. These satellites can receive more illumination per area than their host planets, as the planet reflects stellar light and emits thermal photons. On the contrary, eclipses can significantly alter local climates on exomoons by reducing stellar illumination. In addition to radiative heating, tidal heating can be very large on exomoons, possibly even large enough for sterilization. We identify combinations of physical and orbital parameters for which radiative and tidal heating are strong enough to trigger a runaway greenhouse. By analogy with the circumstellar habitable zone, these constraints define a circumplanetary "habitable edge." We apply our model to hypothetical moons around the recently discovered exoplanet Kepler-22b and the giant planet candidate KOI211.01 and describe, for the first time, the orbits of habitable exomoons. If either planet hosted a satellite at a distance greater than 10 planetary radii, then this could indicate the presence of a habitable moon. PMID:23305357

  7. WISE Detections of Dust in the Habitable Zones of Planet-bearing Stars

    NASA Astrophysics Data System (ADS)

    Morales, Farisa Y.; Padgett, D. L.; Bryden, G.; Werner, M. W.; Furlan, E.

    2012-09-01

    We use data from the Wide-field Infrared Survey Explorer (WISE) all-sky release to explore the incidence of warm dust in the habitable zones around exoplanet-host stars. Dust emission at 12 and/or 22 ?m (T dust ~ 300 and/or ~150 K) traces events in the terrestrial planet zones; its existence implies replenishment by evaporation of comets or collisions of asteroids, possibly stirred by larger planets. Of the 591 planetary systems (728 extrasolar planets) in the Exoplanet Encyclopaedia as of 2012 January 31, 350 are robustly detected by WISE at >=5? level. We perform detailed photosphere subtraction using tools developed for Spitzer data and visually inspect all the WISE images to confirm bona fide point sources. We find nine planet-bearing stars show dust excess emission at 12 and/or 22 ?m at >=3? level around young, main-sequence, or evolved giant stars. Overall, our results yield an excess incidence of ~2.6% for stars of all evolutionary stages, but ~1% for planetary debris disks around main-sequence stars. Besides recovering previously known warm systems, we identify one new excess candidate around the young star UScoCTIO 108.

  8. WISE DETECTIONS OF DUST IN THE HABITABLE ZONES OF PLANET-BEARING STARS

    SciTech Connect

    Morales, Farisa Y.; Bryden, G.; Werner, M. W. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Padgett, D. L. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Furlan, E., E-mail: Farisa@jpl.nasa.gov [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

    2012-09-20

    We use data from the Wide-field Infrared Survey Explorer (WISE) all-sky release to explore the incidence of warm dust in the habitable zones around exoplanet-host stars. Dust emission at 12 and/or 22 {mu}m (T{sub dust} {approx} 300 and/or {approx}150 K) traces events in the terrestrial planet zones; its existence implies replenishment by evaporation of comets or collisions of asteroids, possibly stirred by larger planets. Of the 591 planetary systems (728 extrasolar planets) in the Exoplanet Encyclopaedia as of 2012 January 31, 350 are robustly detected by WISE at {>=}5{sigma} level. We perform detailed photosphere subtraction using tools developed for Spitzer data and visually inspect all the WISE images to confirm bona fide point sources. We find nine planet-bearing stars show dust excess emission at 12 and/or 22 {mu}m at {>=}3{sigma} level around young, main-sequence, or evolved giant stars. Overall, our results yield an excess incidence of {approx}2.6% for stars of all evolutionary stages, but {approx}1% for planetary debris disks around main-sequence stars. Besides recovering previously known warm systems, we identify one new excess candidate around the young star UScoCTIO 108.

  9. The Mt John University Observatory search for Earth-mass planets in the habitable zone of ? Centauri

    NASA Astrophysics Data System (ADS)

    Endl, Michael; Bergmann, Christoph; Hearnshaw, John; Barnes, Stuart I.; Wittenmyer, Robert A.; Ramm, David; Kilmartin, Pam; Gunn, Fraser; Brogt, Erik

    2015-04-01

    The `holy grail' in planet hunting is the detection of an Earth-analogue: a planet with similar mass as the Earth and an orbit inside the habitable zone. If we can find such an Earth-analogue around one of the stars in the immediate solar neighbourhood, we could potentially even study it in such great detail to address the question of its potential habitability. Several groups have focused their planet detection efforts on the nearest stars. Our team is currently performing an intensive observing campaign on the ? Centauri system using the High Efficiency and Resolution Canterbury University Large Échelle Spectrograph (Hercules) at the 1 m McLellan telescope at Mt John University Observatory in New Zealand. The goal of our project is to obtain such a large number of radial velocity (RV) measurements with sufficiently high temporal sampling to become sensitive to signals of Earth-mass planets in the habitable zones of the two stars in this binary system. Over the past few years, we have collected more than 45 000 spectra for both stars combined. These data are currently processed by an advanced version of our RV reduction pipeline, which eliminates the effect of spectral cross-contamination. Here we present simulations of the expected detection sensitivity to low-mass planets in the habitable zone by the Hercules programme for various noise levels. We also discuss our expected sensitivity to the purported Earth-mass planet in a 3.24-day orbit announced by Dumusque et al. (2012).

  10. Exoplanet dynamics. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars.

    PubMed

    Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

    2015-02-01

    Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets' rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere. PMID:25592420

  11. RESEARCH PAPER: The dynamical architecture and habitable zones of the quintuplet planetary system 55 Cancri

    NASA Astrophysics Data System (ADS)

    Ji, Jiang-Hui; Kinoshita, Hiroshi; Liu, Lin; Li, Guang-Yu

    2009-06-01

    We perform numerical simulations to study the secular orbital evolution and dynamical structure of the quintuplet planetary system 55 Cancri with the self-consistent orbital solutions by Fischer and coworkers. In the simulations, we show that this system can be stable for at least 108 yr. In addition, we extensively investigate the planetary configuration of four outer companions with one terrestrial planet in the wide region of 0.790 AU <= a <= 5.900 AU to examine the existence of potential asteroid structure and Habitable Zones (HZs). We show that there are unstable regions for orbits about 4:1, 3:1 and 5:2 mean motion resonances (MMRs) of the outermost planet in the system, and several stable orbits can remain at 3:2 and 1:1 MMRs, which resembles the asteroid belt in the solar system. From a dynamical viewpoint, proper HZ candidates for the existence of more potential terrestrial planets reside in the wide area between 1.0 AU and 2.3 AU with relatively low eccentricities.

  12. Asteroid flux towards circumprimary habitable zones in binary star systems: I. Statistical Overview

    E-print Network

    Bancelin, D; Eggl, S; Maindl, T I; Schäfer, C; Speith, R; Dvorak, R

    2015-01-01

    So far, multiple stellar systems harbor more than 130 extra solar planets. Dynamical simulations show that the outcome of planetary formation process can lead to various planetary architecture (i.e. location, size, mass and water content) when the star system is single or double. In the late phase of planetary formation, when embryo-sized objects dominate the inner region of the system, asteroids are also present and can provide additional material for objects inside the habitable zone (hereafter HZ). In this study, we make a comparison of several binary star systems and their efficiency to move icy asteroids from beyond the snow-line into orbits crossing the HZ. We modeled a belt of 10000 asteroids (remnants from the late phase of planetary formation process) beyond the snow-line. The planetesimals are placed randomly around the primary star and move under the gravitational influence of the two stars and a gas giant. As the planetesimals do not interact with each other, we divided the belt into 100 subrings ...

  13. Calculating the habitable zones of multiple star systems with a new interactive Web site

    SciTech Connect

    Müller, Tobias W. A.; Haghighipour, Nader [Institute for Astronomy and Astrophysics, University of Tübingen, Auf der Morgenstelle 10, D-72076 Tübingen (Germany)

    2014-02-10

    We have developed a comprehensive methodology and an interactive Web site for calculating the habitable zone (HZ) of multiple star systems. Using the concept of spectral weight factor, as introduced in our previous studies of the calculations of HZ in and around binary star systems, we calculate the contribution of each star (based on its spectral energy distribution) to the total flux received at the top of the atmosphere of an Earth-like planet, and use the models of the HZ of the Sun to determine the boundaries of the HZ in multiple star systems. Our interactive Web site for carrying out these calculations is publicly available at http://astro.twam.info/hz. We discuss the details of our methodology and present its application to some of the multiple star systems detected by the Kepler space telescope. We also present the instructions for using our interactive Web site, and demonstrate its capabilities by calculating the HZ for two interesting analytical solutions of the three-body problem.

  14. Can there be additional rocky planets in the Habitable Zone of tight binary stars with a known gas giant?

    E-print Network

    Funk, Barbara; Eggl, Siegfried

    2015-01-01

    Locating planets in HabitableZones (HZs) around other stars is a growing field in contemporary astronomy. Since a large percentage of all G-M stars in the solar neighbourhood are expected to be part of binary or multiple stellar systems, investigations of whether habitable planets are likely to be discovered in such environments are of prime interest to the scientific community. As current exoplanet statistics predicts that the chances are higher to find new worlds in systems that are already known to have planets, we examine four known extrasolar planetary systems in tight binaries in order to determine their capacity to host additional habitable terrestrial planets. Those systems are Gliese 86, gamma Cephei, HD 41004 and HD 196885. In the case of gamma Cephei, our results suggest that only the M dwarf companion could host additional potentially habitable worlds. Neither could we identify stable, potentially habitable regions around HD 196885 A. HD 196885 B can be considered a slightly more promising target ...

  15. THE HUNT FOR EXOMOONS WITH KEPLER (HEK). III. THE FIRST SEARCH FOR AN EXOMOON AROUND A HABITABLE-ZONE PLANET

    SciTech Connect

    Kipping, D. M. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Forgan, D. [Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); Hartman, J.; Bakos, G. Á. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 05844 (United States); Nesvorný, D. [Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States); Schmitt, A.; Buchhave, L., E-mail: dkipping@cfa.harvard.edu [Niels Bohr Institute, Copenhagen University (Denmark)

    2013-11-10

    Kepler-22b is the first transiting planet to have been detected in the habitable zone of its host star. At 2.4 R{sub ?}, Kepler-22b is too large to be considered an Earth analog, but should the planet host a moon large enough to maintain an atmosphere, then the Kepler-22 system may yet possess a telluric world. Aside from being within the habitable zone, the target is attractive due to the availability of previously measured precise radial velocities and low intrinsic photometric noise, which has also enabled asteroseismology studies of the star. For these reasons, Kepler-22b was selected as a target-of-opportunity by the 'Hunt for Exomoons with Kepler' (HEK) project. In this work, we conduct a photodynamical search for an exomoon around Kepler-22b leveraging the transits, radial velocities, and asteroseismology plus several new tools developed by the HEK project to improve exomoon searches. We find no evidence for an exomoon around the planet and exclude moons of mass M{sub S} > 0.5 M{sub ?} to 95% confidence. By signal injection and blind retrieval, we demonstrate that an Earth-like moon is easily detected for this planet even when the time-correlated noise of the data set is taken into account. We provide updated parameters for the planet Kepler-22b, including a revised mass of M{sub P} < 53 M{sub ?} to 95% confidence and an eccentricity of 0.13{sub -0.13}{sup +0.36} by exploiting Single-body Asterodensity Profiling. Finally, we show that Kepler-22b has a >95% probability of being within the empirical habitable zone but a <5% probability of being within the conservative habitable zone.

  16. Observations of Interstellar Formamide: Availability of a Prebiotic Precursor in the Galactic Habitable Zone

    PubMed Central

    Adande, Gilles R.; Woolf, Neville J.

    2013-01-01

    Abstract We conducted a study on interstellar formamide, NH2CHO, toward star-forming regions of dense molecular clouds, using the telescopes of the Arizona Radio Observatory (ARO). The Kitt Peak 12?m antenna and the Submillimeter Telescope (SMT) were used to measure multiple rotational transitions of this molecule between 100 and 250?GHz. Four new sources of formamide were found [W51M, M17 SW, G34.3, and DR21(OH)], and complementary data were obtained toward Orion-KL, W3(OH), and NGC 7538. From these observations, column densities for formamide were determined to be in the range of 1.1×1012 to 9.1×1013 cm?2, with rotational temperatures of 70–177?K. The molecule is thus present in warm gas, with abundances relative to H2 of 1×10?11 to 1×10?10. It appears to be a common constituent of star-forming regions that foster planetary systems within the galactic habitable zone, with abundances comparable to that found in comet Hale-Bopp. Formamide's presence in comets and molecular clouds suggests that the compound could have been brought to Earth by exogenous delivery, perhaps with an infall flux as high as ?0.1?mol/km2/yr or 0.18?mmol/m2 in a single impact. Formamide has recently been proposed as a single-carbon, prebiotic source of nucleobases and nucleic acids. This study suggests that a sufficient amount of NH2CHO could have been available for such chemistry. Key Words: Formamide—Astrobiology—Radioastronomy—ISM—Comets—Meteorites. Astrobiology 13, 439–453. PMID:23654214

  17. Observations of interstellar formamide: availability of a prebiotic precursor in the galactic habitable zone.

    PubMed

    Adande, Gilles R; Woolf, Neville J; Ziurys, Lucy M

    2013-05-01

    We conducted a study on interstellar formamide, NH2CHO, toward star-forming regions of dense molecular clouds, using the telescopes of the Arizona Radio Observatory (ARO). The Kitt Peak 12 m antenna and the Submillimeter Telescope (SMT) were used to measure multiple rotational transitions of this molecule between 100 and 250 GHz. Four new sources of formamide were found [W51M, M17 SW, G34.3, and DR21(OH)], and complementary data were obtained toward Orion-KL, W3(OH), and NGC 7538. From these observations, column densities for formamide were determined to be in the range of 1.1×10(12) to 9.1×10(13) cm(-2), with rotational temperatures of 70-177 K. The molecule is thus present in warm gas, with abundances relative to H2 of 1×10(-11) to 1×10(-10). It appears to be a common constituent of star-forming regions that foster planetary systems within the galactic habitable zone, with abundances comparable to that found in comet Hale-Bopp. Formamide's presence in comets and molecular clouds suggests that the compound could have been brought to Earth by exogenous delivery, perhaps with an infall flux as high as ~0.1 mol/km(2)/yr or 0.18 mmol/m(2) in a single impact. Formamide has recently been proposed as a single-carbon, prebiotic source of nucleobases and nucleic acids. This study suggests that a sufficient amount of NH2CHO could have been available for such chemistry. PMID:23654214

  18. EFFECT OF METALLICITY ON THE EVOLUTION OF THE HABITABLE ZONE FROM THE PRE-MAIN SEQUENCE TO THE ASYMPTOTIC GIANT BRANCH AND THE SEARCH FOR LIFE

    SciTech Connect

    Danchi, William C. [Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771 (United States); Lopez, Bruno, E-mail: william.c.danchi@nasa.gov, E-mail: bruno.lopez@oca.eu [Observatoire de la Cote d'Azur, Laboratoire Lagrange UMR 7293, BP 4229, F-06034 Nice Cedex 4 (France)

    2013-05-20

    During the course of stellar evolution, the location and width of the habitable zone changes as the luminosity and radius of the star evolves. The duration of habitability for a planet located at a given distance from a star is greatly affected by the characteristics of the host star. A quantification of these effects can be used observationally in the search for life around nearby stars. The longer the duration of habitability, the more likely it is that life has evolved. The preparation of observational techniques aimed at detecting life would benefit from the scientific requirements deduced from the evolution of the habitable zone. We present a study of the evolution of the habitable zone around stars of 1.0, 1.5, and 2.0 M{sub Sun} for metallicities ranging from Z = 0.0001 to Z = 0.070. We also consider the evolution of the habitable zone from the pre-main sequence until the asymptotic giant branch is reached. We find that metallicity strongly affects the duration of the habitable zone for a planet as well as the distance from the host star where the duration is maximized. For a 1.0 M{sub Sun} star with near solar metallicity, Z = 0.017, the duration of the habitable zone is >10 Gyr at distances 1.2-2.0 AU from the star, whereas the duration is >20 Gyr for high-metallicity stars (Z = 0.070) at distances of 0.7-1.8 AU, and {approx}4 Gyr at distances of 1.8-3.3 AU for low-metallicity stars (Z = 0.0001). Corresponding results have been obtained for stars of 1.5 and 2.0 solar masses.

  19. Direct Detection of Nearby Habitable Zone Planets Using Slicer Based Integral Field Spectrographs and EPICS on the E-ELT

    NASA Astrophysics Data System (ADS)

    Salter, Graeme S.; Thatte, Niranjan A.; Tecza, Matthias; Clarke, Fraser; Kasper, Markus E.

    2014-04-01

    Early design studies for the future Exo-Planet Imaging Camera and Specrotgraph (EPICS) on the European Extremely Large Telescope (E-ELT) show the ability to probe the region of super-Earths in the habitable zone of stars within 5pc (including Gilese 581d). However, these planets will be lost to us if the correct choice of integral field spectrograph (IFS) technology is not selected for such an instrument the ability to fit and remove the speckle noise that remains is crucial to reaching these contrasts. We conclusively demonstrate, though the use of an experimental setup producing an artificial speckle, that slicer based IFSs and post-processing using spectral deconvolution can achieve speckle rejection factors exceeding 103. Contrary to popular belief, we do not find any evidence that this choice of IFS technology limits the achievable contrast. Coupled with extreme adaptive optics and high performance coronographs, a slicer based integral field spectrograph could achieve contrasts exceeding 109, enabling these super-Earths to be detected in the habitable zone of nearby stars, making it an attractive option for the next generation of instruments being designed for the direct detection of extra solar planets.

  20. Formation, Habitability, and Detection of Extrasolar Moons

    E-print Network

    Heller, René; Kipping, David; Limbach, Mary Anne; Turner, Edwin; Greenberg, Richard; Sasaki, Takanori; Bolmont, Émeline; Grasset, Olivier; Lewis, Karen; Barnes, Rory; Zuluaga, Jorge I

    2014-01-01

    The diversity and quantity of moons in the Solar System suggest a manifold population of natural satellites exist around extrasolar planets. Of peculiar interest from an astrobiological perspective, the number of sizable moons in the stellar habitable zones may outnumber planets in these circumstellar regions. With technological and theoretical methods now allowing for the detection of sub-Earth-sized extrasolar planets, the first detection of an extrasolar moon appears feasible. In this review, we summarize formation channels of massive exomoons that are potentially detectable with current or near-future instruments. We discuss the orbital effects that govern exomoon evolution, we present a framework to characterize an exomoon's stellar plus planetary illumination as well as its tidal heating, and we address the techniques that have been proposed to search for exomoons. Most notably, we show that natural satellites in the range of 0.1 - 0.5 Earth mass (i) are potentially habitable, (ii) can form within the c...

  1. Coronal Mass Ejection (CME) Activity of Low Mass M Stars as An Important Factor for The Habitability of Terrestrial Exoplanets. II. CME-Induced Ion Pick Up of Earth-like Exoplanets in Close-In Habitable Zones

    Microsoft Academic Search

    Helmut Lammer; Herbert I. M. Lichtenegger; Yuri N. Kulikov; Jean-Mathias Grießmeier; N. Terada; Nikolai V. Erkaev; Helfried K. Biernat; Maxim L. Khodachenko; Ignasi Ribas; Thomas Penz; Franck Selsis

    2007-01-01

    Atmospheric erosion of CO2 -rich Earth-size exoplanets due to coronal mass ejection (CME)-induced ion pick up within close-in habitable zones of active M-type dwarf stars is investigated. Since M stars are active at the X-ray and extreme ultraviolet radiation (XUV) wave-lengths over long periods of time, we have applied a thermal balance model at various XUV flux input values for

  2. The effect of planets beyond the ice line on the accretion of volatiles by habitable-zone rocky planets

    SciTech Connect

    Quintana, Elisa V. [SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Lissauer, Jack J., E-mail: elisa.quintana@nasa.gov [Space Science and Astrobiology Division 245-3, NASA Ames Research Center, Moffett Field, CA 94035 (United States)

    2014-05-01

    Models of planet formation have shown that giant planets have a large impact on the number, masses, and orbits of terrestrial planets that form. In addition, they play an important role in delivering volatiles from material that formed exterior to the snow line (the region in the disk beyond which water ice can condense) to the inner region of the disk where terrestrial planets can maintain liquid water on their surfaces. We present simulations of the late stages of terrestrial planet formation from a disk of protoplanets around a solar-type star and we include a massive planet (from 1 M {sub ?} to 1 M {sub J}) in Jupiter's orbit at ?5.2 AU in all but one set of simulations. Two initial disk models are examined with the same mass distribution and total initial water content, but with different distributions of water content. We compare the accretion rates and final water mass fraction of the planets that form. Remarkably, all of the planets that formed in our simulations without giant planets were water-rich, showing that giant planet companions are not required to deliver volatiles to terrestrial planets in the habitable zone. In contrast, an outer planet at least several times the mass of Earth may be needed to clear distant regions of debris truncating the epoch of frequent large impacts. Observations of exoplanets from radial velocity surveys suggest that outer Jupiter-like planets may be scarce, therefore, the results presented here suggest that there may be more habitable planets residing in our galaxy than previously thought.

  3. The Habitable-Zone Planet Finder: A Stabilized Fiber-Fed NIR Spectrograph for the Hobby-Eberly Telescope

    E-print Network

    Mahadevan, Suvrath; Bender, Chad; Terrien, Ryan; Wright, Jason T; Halverson, Sam; Hearty, Fred; Nelson, Matt; Burton, Adam; Redman, Stephen; Osterman, Steven; Diddams, Scott; Kasting, James; Endl, Michael; Deshpande, Rohit

    2012-01-01

    We present the scientific motivation and conceptual design for the recently funded Habitable-zone Planet Finder (HPF), a stabilized fiber-fed near-infrared (NIR) spectrograph for the 10 meter class Hobby-Eberly Telescope (HET) that will be capable of discovering low mass planets around M dwarfs. The HPF will cover the NIR Y & J bands to enable precise radial velocities to be obtained on mid M dwarfs, and enable the detection of low mass planets around these stars. The conceptual design is comprised of a cryostat cooled to 200K, a dual fiber-feed with a science and calibration fiber, a gold coated mosaic echelle grating, and a Teledyne Hawaii-2RG (H2RG) NIR detector with a 1.7$\\mu$m cutoff. A uranium-neon hollow-cathode lamp is the baseline wavelength calibration source, and we are actively testing laser frequency combs to enable even higher radial velocity precision. We will present the overall instrument system design and integration with the HET, and discuss major system challenges, key choices, and ong...

  4. Remote Life Detection Criteria, Habitable Zone Boundaries, and the Frequency of Earthlike Planets around M and Late-K Stars

    E-print Network

    Kasting, James F; Ramirez, Ramses R; Harman, Chester

    2013-01-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. Historically, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, 'Dune' planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future spa...

  5. The Snow Line in Viscous Disks around Low-mass Stars: Implications for Water Delivery to Terrestrial Planets in the Habitable Zone

    NASA Astrophysics Data System (ADS)

    Mulders, Gijs D.; Ciesla, Fred J.; Min, Michiel; Pascucci, Ilaria

    2015-07-01

    The water-ice or snow line is one of the key properties of protoplanetary disks that determines the water content of terrestrial planets in the habitable zone. Its location is determined by the properties of the star, the mass accretion rate through the disk, and the size distribution of dust suspended in the disk. We calculate the snow-line location from recent observations of mass accretion rates and as a function of stellar mass. By taking the observed dispersion in mass accretion rates as a measure of the dispersion in initial disk mass, we find that stars of a given mass will exhibit a range of snow-line locations. At a given age and stellar mass, the observed dispersion in mass accretion rates of 0.4 dex naturally leads to a dispersion in snow-line locations of ?0.2 dex. For ISM-like dust sizes, the 1? snow-line location among solar-mass stars of the same age ranges from ?2 to ?5 AU. For more realistic dust opacities that include larger grains, the snow line is located up to two times closer to the star. We use these locations and the outcome of N-body simulations to predict the amount of water delivered to terrestrial planets that formed in situ in the habitable zone. We find that the dispersion in snow-line locations leads to a large range in water content. For ISM-like dust sizes, a significant fraction of habitable-zone terrestrial planets around Sun-like stars remain dry, and no water is delivered to the habitable zones of low-mass M stars (\\lt 0.5 {M}? ) as in previous works. The closer-in snow line in disks with larger grains enables water delivery to the habitable zone for a significant fraction of M stars and all FGK stars. Considering their larger numbers and higher planet occurrence, M stars may host most of the water-rich terrestrial planets in the galaxy if these planets are able to hold on to their water in their subsequent evolution.

  6. A REVISED ESTIMATE OF THE OCCURRENCE RATE OF TERRESTRIAL PLANETS IN THE HABITABLE ZONES AROUND KEPLER M-DWARFS

    SciTech Connect

    Kopparapu, Ravi Kumar [Department of Geosciences, Penn State University, 443 Deike Building, University Park, PA 16802 (United States)

    2013-04-10

    Because of their large numbers, low-mass stars may be the most abundant planet hosts in our Galaxy. Furthermore, terrestrial planets in the habitable zones (HZs) around M-dwarfs can potentially be characterized in the near future and hence may be the first such planets to be studied. Recently, Dressing and Charbonneau used Kepler data and calculated the frequency of terrestrial planets in the HZ of cool stars to be 0.15{sup +0.13}{sub -0.06} per star for Earth-size planets (0.5-1.4 R{sub Circled-Plus }). However, this estimate was derived using the Kasting et al. HZ limits, which were not valid for stars with effective temperatures lower than 3700 K. Here we update their result using new HZ limits from Kopparapu et al. for stars with effective temperatures between 2600 K and 7200 K, which includes the cool M stars in the Kepler target list. The new HZ boundaries increase the number of planet candidates in the HZ. Assuming Earth-size planets as 0.5-1.4 R{sub Circled-Plus }, when we reanalyze their results, we obtain a terrestrial planet frequency of 0.48{sup +0.12}{sub -0.24} and 0.53{sup +0.08}{sub -0.17} planets per M-dwarf star for conservative and optimistic limits of the HZ boundaries, respectively. Assuming Earth-size planets as 0.5-2 R{sub Circled-Plus }, the frequency increases to 0.51{sup +0.10}{sub -0.20} per star for the conservative estimate and to 0.61{sup +0.07}{sub -0.15} per star for the optimistic estimate. Within uncertainties, our optimistic estimates are in agreement with a similar optimistic estimate from the radial velocity survey of M-dwarfs (0.41{sup +0.54}{sub -0.13}). So, the potential for finding Earth-like planets around M stars may be higher than previously reported.

  7. Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. I. CME impact on expected magnetospheres of Earth-like exoplanets in close-in habitable zones.

    PubMed

    Khodachenko, Maxim L; Ribas, Ignasi; Lammer, Helmut; Griessmeier, Jean-Mathias; Leitner, Martin; Selsis, Franck; Eiroa, Carlos; Hanslmeier, Arnold; Biernat, Helfried K; Farrugia, Charles J; Rucker, Helmut O

    2007-02-01

    Low mass M- and K-type stars are much more numerous in the solar neighborhood than solar-like G-type stars. Therefore, some of them may appear as interesting candidates for the target star lists of terrestrial exoplanet (i.e., planets with mass, radius, and internal parameters identical to Earth) search programs like Darwin (ESA) or the Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The higher level of stellar activity of low mass M stars, as compared to solar-like G stars, as well as the closer orbital distances of their habitable zones (HZs), means that terrestrial-type exoplanets within HZs of these stars are more influenced by stellar activity than one would expect for a planet in an HZ of a solar-like star. Here we examine the influences of stellar coronal mass ejection (CME) activity on planetary environments and the role CMEs may play in the definition of habitability criterion for the terrestrial type exoplanets near M stars. We pay attention to the fact that exoplanets within HZs that are in close proximity to low mass M stars may become tidally locked, which, in turn, can result in relatively weak intrinsic planetary magnetic moments. Taking into account existing observational data and models that involve the Sun and related hypothetical parameters of extrasolar CMEs (density, velocity, size, and occurrence rate), we show that Earth-like exoplanets within close-in HZs should experience a continuous CME exposure over long periods of time. This fact, together with small magnetic moments of tidally locked exoplanets, may result in little or no magnetospheric protection of planetary atmospheres from a dense flow of CME plasma. Magnetospheric standoff distances of weakly magnetized Earth-like exoplanets at orbital distances

  8. Circumstellar Dust Created by Terrestrial Planet Formation in HD 113766

    E-print Network

    C. M. Lisse; C. H. Chen; M. C. Wyatt; A. Morlok

    2007-10-03

    We present an analysis of the gas-poor circumstellar material in the HD 113766 binary system (F3/F5, 10 - 16 Myr), recently observed by the Spitzer Space Telescope. For our study we have used the infrared mineralogical model derived from observations of the Deep Impact experiment. We find the dust dominated by warm, fine (~1 um) particles, abundant in Mg-rich olivine, crystalline pyroxenes, amorphous silicates, Fe-rich sulfides, amorphous carbon, and colder water-ice. The warm dust material mix is akin to an inner main belt asteroid of S-type composition. The ~440 K effective temperature of the warm dust implies that the bulk of the observed material is in a narrow belt ~1.8 AU from the 4.4 L_solar central source, in the terrestrial planet-forming region and habitable zone of the system (equivalent to 0.9 AU in the solar system). The icy dust lies in 2 belts, located at 4-9 AU and at 30 - 80 AU. The lower bound of warm dust mass in 0.1 - 20 um, dn/da ~ a^-3.5 particles is very large, at least 3 x 10^20 kg, equivalent to a 320 km radius asteroid of 2.5 g cm^-3 density. Assuming 10m largest particles present, the lower bound of warm dust mass is at least 0.5 M_Mars The dust around HD 113766A originates from catastrophic disruption of terrestrial planet embryo(s) and subsequent grinding of the fragments, or from collisions in a young, extremely dense asteroid belt undergoing aggregation. The persistence of the strong IR excess over the last two decades argues for a mechanism to provide replenishment of the circumstellar material on yearly timescales.

  9. EXOPLANET CHARACTERIZATION BY PROXY: A TRANSITING 2.15 R{sub Circled-Plus} PLANET NEAR THE HABITABLE ZONE OF THE LATE K DWARF KEPLER-61

    SciTech Connect

    Ballard, Sarah; Charbonneau, David; Fressin, Francois; Torres, Guillermo; Irwin, Jonathan; Newton, Elisabeth [University of Washington, Seattle, WA 98195 (United States); Desert, Jean-Michel; Crepp, Justin R.; Shporer, Avi [California Institute of Technology, Pasadena, CA 91125 (United States); Mann, Andrew W. [Institute for Astronomy, University of Hawai'i, Honolulu, HI 96822 (United States); Ciardi, David R. [NASA Exoplanet Science Institute/Caltech, Pasadena, CA 91125 (United States); Henze, Christopher E.; Bryson, Stephen T.; Howell, Steven B. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Horch, Elliott P. [Southern Connecticut State University, New Haven, CT 06515 (United States); Everett, Mark E., E-mail: sarahba@uw.edu [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)

    2013-08-20

    We present the validation and characterization of Kepler-61b: a 2.15 R{sub Circled-Plus} planet orbiting near the inner edge of the habitable zone of a low-mass star. Our characterization of the host star Kepler-61 is based upon a comparison with a set of spectroscopically similar stars with directly measured radii and temperatures. We apply a stellar prior drawn from the weighted mean of these properties, in tandem with the Kepler photometry, to infer a planetary radius for Kepler-61b of 2.15 {+-} 0.13 R{sub Circled-Plus} and an equilibrium temperature of 273 {+-} 13 K (given its period of 59.87756 {+-} 0.00020 days and assuming a planetary albedo of 0.3). The technique of leveraging the physical properties of nearby ''proxy'' stars allows for an independent check on stellar characterization via the traditional measurements with stellar spectra and evolutionary models. In this case, such a check had implications for the putative habitability of Kepler-61b: the planet is 10% warmer and larger than inferred from K-band spectral characterization. From the Kepler photometry, we estimate a stellar rotation period of 36 days, which implies a stellar age of >1 Gyr. We summarize the evidence for the planetary nature of the Kepler-61 transit signal, which we conclude is 30,000 times more likely to be due to a planet than a blend scenario. Finally, we discuss possible compositions for Kepler-61b with a comparison to theoretical models as well as to known exoplanets with similar radii and dynamically measured masses.

  10. Embryos grown in the dead zone: Assembling the first protoplanetary cores in low mass self-gravitating circumstellar disks of gas and solids

    E-print Network

    W. Lyra; A. Johansen; H. Klahr; N. Piskunov

    2008-10-14

    In the borders of the dead zones of protoplanetary disks, the inflow of gas produces a local density maximum that triggers the Rossby wave instability. The vortices that form are efficient in trapping solids. We aim to assess the possibility of gravitational collapse of the solids within the Rossby vortices. We perform global simulations of the dynamics of gas and solids in a low mass non-magnetized self-gravitating thin protoplanetary disk with the Pencil code. We use multiple particle species of radius 1, 10, 30, and 100 cm. The dead zone is modeled as a region of low viscosity. The Rossby vortices excited in the edges of the dead zone are very efficient particle traps. Within 5 orbits after their appearance, the solids achieve critical density and undergo gravitational collapse into Mars sized objects. The velocity dispersions are of the order of 10 m/s for newly formed embryos, later lowering to less than 1 m/s by drag force cooling. After 200 orbits, 38 gravitationally bound embryos were formed inside the vortices, half of them being more massive than Mars. The embryos are composed primarily of same-sized particles. We conclude that the presence of a dead zone naturally gives rise to a population of protoplanetary cores in the mass range of 0.1-0.6 Earth masses, on very short timescales.

  11. Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

    SciTech Connect

    Kadoya, S. [Department of Earth and Planetary Science, The University of Tokyo, Kiban Bldg. 408, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, Kiban Bldg. 409, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

    2014-08-01

    Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

  12. CHARACTERIZING HABITABLE EXOMOONS

    SciTech Connect

    Kaltenegger, L. [Harvard University, 60 Garden Street, 02138 MA, Cambridge (United States)], E-mail: lkaltene@cfa.harvard.edu

    2010-04-01

    We discuss the possibility of screening the atmosphere of exomoons for habitability. We concentrate on Earth-like satellites of extrasolar giant planets (EGPs) that orbit in the Habitable Zone (HZ) of their host stars. The detectability of exomoons for EGPs in the HZ has recently been shown to be feasible with the Kepler Mission or equivalent photometry using transit duration observations. Transmission spectroscopy of exomoons is a unique potential tool to screen them for habitability in the near future, especially around low mass stars. Using the Earth itself as a proxy we show the potential and limits of spectroscopy to detect biomarkers on an Earth-like exomoon and discuss effects of tidal locking for such potential habitats.

  13. The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs

    NASA Astrophysics Data System (ADS)

    Zechmeister, M.; Kürster, M.; Endl, M.

    2009-10-01

    We present radial velocity (RV) measurements of our sample of 40 M dwarfs from our planet search programme with VLT+UVES begun in 2000. Although with our RV precision down to 2-2.5 m/s and timebase line of up to 7 years, we are capable of finding planets of a few Earth masses in the close-in habitable zones of M dwarfs, there is no detection of a planetary companion. To demonstrate this we present mass detection limits allowing us to exclude Jupiter-mass planets up to 1 AU for most of our sample stars. We identified 6 M dwarfs that host a brown dwarf or low-mass stellar companion. With the exception of these, all other sample stars show low RV variability with an rms <20 m/s. Some high proper motion stars exhibit a linear RV trend consistent with their secular acceleration. Furthermore, we examine our data sets for a possible correlation between RVs and stellar activity as seen in variations of the H? line strength. For Barnard's star we found a significant anticorrelation, but most of the sample stars do not show such a correlation. Based on observations collected at the European Southern Observatory, Paranal Chile, ESO programmes 65.L-0428, 66.C-0446, 267.C-5700, 68.C-0415, 69.C-0722, 70.C-0044, 71.C-0498, 072.C-0495, 173.C-0606, 078.C-0829. Radial velocity data are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/859

  14. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars.

    PubMed

    Kasting, James F; Kopparapu, Ravikumar; Ramirez, Ramses M; Harman, Chester E

    2014-09-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet's atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, "Dune" planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, S(eff), the recently recalculated HZ boundaries are: recent Venus--1.78; runaway greenhouse--1.04; moist greenhouse--1.01; maximum greenhouse--0.35; and early Mars--0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4-0.5. PMID:24277805

  15. Remote life-detection criteria, habitable zone boundaries, and the frequency of Earth-like planets around M and late K stars

    PubMed Central

    Kasting, James F.; Kopparapu, Ravikumar; Ramirez, Ramses M.; Harman, Chester E.

    2014-01-01

    The habitable zone (HZ) around a star is typically defined as the region where a rocky planet can maintain liquid water on its surface. That definition is appropriate, because this allows for the possibility that carbon-based, photosynthetic life exists on the planet in sufficient abundance to modify the planet’s atmosphere in a way that might be remotely detected. Exactly what conditions are needed, however, to maintain liquid water remains a topic for debate. In the past, modelers have restricted themselves to water-rich planets with CO2 and H2O as the only important greenhouse gases. More recently, some researchers have suggested broadening the definition to include arid, “Dune” planets on the inner edge and planets with captured H2 atmospheres on the outer edge, thereby greatly increasing the HZ width. Such planets could exist, but we demonstrate that an inner edge limit of 0.59 AU or less is physically unrealistic. We further argue that conservative HZ definitions should be used for designing future space-based telescopes, but that optimistic definitions may be useful in interpreting the data from such missions. In terms of effective solar flux, Seff, the recently recalculated HZ boundaries are: recent Venus—1.78; runaway greenhouse—1.04; moist greenhouse—1.01; maximum greenhouse—0.35; and early Mars—0.32. Based on a combination of different HZ definitions, the frequency of potentially Earth-like planets around late K and M stars observed by Kepler is in the range of 0.4–0.5. PMID:24277805

  16. Habitable Trinity

    NASA Astrophysics Data System (ADS)

    Dohm, J. M.; Maruyama, S.

    2013-12-01

    We propose a new concept of a habitable environment in the search for life beyond Earth that goes beyond the follow-the-water paradigm, newly named Habitable Trinity. Habitable Trinity is the coexistence of an atmosphere (consisting largely of C and N), an ocean (H and O), and a landmass (supplier of nutrients). It is the minimum requirement for the beginning of life to satisfy (1) formation of membrane, (2) metabolism, and (3) self-replication as we know it. A habitable planet, which has largely been defined as having an adequate climate, a sufficient atmosphere, and the presence of liquid water on its surface, is insufficient to meet the requirements to bear life. Also, material circulation driven by the Sun must be maintained with Habitable Trinity to continue the supply of elements necessary to sustain organic radical reactions that is the basis of life. The Sun is the major engine that links the three components primarily through hydrological cycling, including weathering, erosion, and transport of nutrient-enriched landmass materials to the ocean via far-reaching river systems. Habitable Trinity can be applied to other planets and moons to discuss the presence of extraterrestrial life. Mars is considered to be the best target to test the hypothesis of whether life exists elsewhere in our solar system, as it records an ancient Habitable Trinity (i.e., lakes and oceans which interacted with a landmass (cratered southern highlands) and an atmosphere). Other terrestrial planets, as well as satellites of the gaseous giants such as Europa and Titan, have little chance to harbor life as we know it because they lack Habitable Trinity. Going beyond 'the-follow-the-water-approach', the Habitable-Trinity concept provides an index in the quest for life-containing planetary bodies beyond our solar system as the reconnaissance systems become increasingly autonomous and at higher resolution, affording greater perspective during this golden age of international and interdisciplinary exploration and discovery.

  17. Tides and Habitability

    NASA Astrophysics Data System (ADS)

    Barnes, R.

    2014-04-01

    The relatively low luminosities of M dwarfs, white dwarfs, and brown dwarfs result in habitable zones that are close enough in for strong tidal processes between the planet and its host to occur. As is well known, tidal despinning can result in slow or synchronous rotation for close-in planets, but recent investigations have revealed that tides impact habitability in other ways. Tides can drive planetary obliquity to 0, eliminating seasons and creating strong cold traps at the poles. Tides can force a migration of the semi-major axis, possibly removing planets from the habitable zone. Tidal despinning and orbital evolution produces internal heating that can alter both the interior and the atmosphere. For modest eccentricities, tidal heating can be comparable to the modern Earth's (non-tidal) energy sources, changing the thermal profile in the planet and possibly quenching dynamo generation. For larger eccentricities tidal heating can be orders of magnitude larger, suggesting some super-Earths are actually "super-Ios." In extreme cases tidal heating could trigger a runaway greenhouse for hundreds of millions of years, threatening permanent sterilization. Tides damp eccentricity, which lowers the heating rate, but companion planets can perturb orbits and maintain non-zero eccentricities. In some cases, tidal heating sustained by companions could power geochemical cycles that permit habitability for trillions of years.

  18. Astrophysical Conditions for Planetary Habitability

    E-print Network

    Guedel, M; Erkaev, N; Kasting, J; Khodachenko, M; Lammer, H; Pilat-Lohinger, E; Rauer, H; Ribas, I; Wood, B E

    2014-01-01

    With the discovery of hundreds of exoplanets and a potentially huge number of Earth-like planets waiting to be discovered, the conditions for their habitability have become a focal point in exoplanetary research. The classical picture of habitable zones primarily relies on the stellar flux allowing liquid water to exist on the surface of an Earth-like planet with a suitable atmosphere. However, numerous further stellar and planetary properties constrain habitability. Apart from "geophysical" processes depending on the internal structure and composition of a planet, a complex array of astrophysical factors additionally determine habitability. Among these, variable stellar UV, EUV, and X-ray radiation, stellar and interplanetary magnetic fields, ionized winds, and energetic particles control the constitution of upper planetary atmospheres and their physical and chemical evolution. Short- and long-term stellar variability necessitates full time-dependent studies to understand planetary habitability at any point ...

  19. Exoplanet Habitability: Effects of Planetesimal Carbon Chemistry

    NASA Astrophysics Data System (ADS)

    Johnson, Torrence; Mousis, Olivier; Lunine, Jonathan; Madhusudhan, Nikku

    2014-05-01

    We explore the effects of reported differences in C/O values for exoplanet host stars on the composition of planetesimals formed beyond the snow line in these systems. Since the value of C/O in a planet forming nebula has a strong effect on amount of oxygen available for water ice in an oxidizing nebula, exoplanet systems for host stars with C/O greater than the solar value may have planetesimals with very little or no water ice. We have estimated the composition of volatile and refractory material in extrasolar planetesimals using a set of stars with a wide range of measured C/O abundances (Johnson et al. ApJ. 757(2), 192, 2012). The volatile ice content of planetesimals in these systems varies significantly with C/O, controlled primarily by the availability of O for H2O ice condensation. Systems with C/O less than the solar value (C/O = 0.55) should have very water ice rich planetesimals, while water ice mass fraction decreases rapidly with increasing C/O until only ices of CO and CO2 are left in significant proportions. If a significant fraction of C is in the form of refractory CHON particles, C and O are removed from the gas phase and the condensates for super-solar C/O values will be water-poor mixtures of silicates and metal, carbon, and carbon-bearing volatile ices, depending on temperature. For very carbon-rich systems, oxidizing conditions cannot be sustained beyond about C/O=1, due to the oxygen sequestered in solid silicates, oxides and CHON, for refractory C fractions within the Pollack et al. range of 0.4 - 0.7 (ApJ. 421, 615, 1994). These results have implications for assessing the habitability of exoplanets since they constrain the amount of water available beyond the snow line for dynamical delivery to inner planets, depending on the host star's C/O in the circumstellar nebula. Thus one the key chemical ingredients for habitability may be in short supply in carbon-rich, oxygen-poor systems even if planets exist in the 'habitable zone'. TVJ acknowledges government support at JPL/Caltech, under a contract with NASA. NM acknowledges support from Yale University. JIL was supported by the JWST Project through NASA. O.M. acknowledges support from CNES.

  20. Constraints on the habitability of extrasolar moons

    E-print Network

    Heller, René

    2012-01-01

    Detections of massive extrasolar moons are shown feasible with the Kepler space telescope. Kepler's findings of about 50 exoplanets in the stellar habitable zone naturally make us wonder about the habitability of their hypothetical moons. Illumination from the planet, eclipses, tidal heating, and tidal locking distinguish remote characterization of exomoons from that of exoplanets. We show how evaluation of an exomoon's habitability is possible based on the parameters accessible by current and near-future technology.

  1. Habitable exoplanets statistics in the Milky Way

    NASA Astrophysics Data System (ADS)

    Anagnos, Th.

    2013-09-01

    We present an exoplanet statistical analysis into the Milky Way. We use the Becanson galactic synthetic model to simulate the Milky Way and the galactic and stellar habitable zones to calculate habitable planets. To assess habitability on the Galactic scale, we model supernova rates and planet formation. Our study, models the SNII and SNIa sterilizations by selecting them from within this preexisting stellar population. Furthermore, we consider habitability on tidally locked and non-tidally locked planets separately, and study habitability as a function of height above and below the Galactic mid-plane. The number of total habitable planets makes Milky Way practically empty of habitable planets. Our results, from these simulations, agree very well with Kepler's discoveries. Finally, we apply our results to the PLATO future space mission.

  2. UV Habitability of Possible Exomoons in Observed F-star Planetary Systems

    E-print Network

    Sato, Satoko

    2015-01-01

    In the present study we explore the astrobiological significance of F-type stars of spectral type between F5 V and F9.5 V, which possess Jupiter-type planets within or close to their climatological habitable zones. These planets, or at least a subset of them, may also possess rocky exomoons, which potentially offer habitable environments. Our work considers eight selected systems. The Jupiter-type planets in these systems are in notably different orbits with eccentricities ranging from 0.08 to 0.72. Particularly, we consider the stellar UV environments provided by the photospheric stellar radiation in regard to the circumstellar habitability of the system. According to previous studies, DNA is taken as a proxy for carbon-based macromolecules following the paradigm that extraterrestrial biology might be based on hydrocarbons. Thus, the DNA action spectrum is utilized to represent the impact of the stellar UV radiation. Atmospheric attenuation is taken into account based on parameterized attenuation functions. ...

  3. Habitability of Planets Orbiting Cool Stars

    Microsoft Academic Search

    Rory Barnes; Victoria S. Meadows; Shawn D. Domagal-Goldman; Rene Heller; Brian Jackson; Mercedes Lopez-Morales; Angelle Tanner; Natalia Gomez-Perez; Thomas Ruedas

    2010-01-01

    Terrestrial planets are more likely to be detected if they orbit M dwarfs due to the favorable planet\\/star size and mass ratios. However, M dwarf habitable zones are significantly closer to the star than the one around our Sun, which leads to different requirements for planetary habitability and its detection. We review 1) the current limits to detection, 2) the

  4. Vortices In Circumstellar Disks

    E-print Network

    Fred Adams; Richard Watkins

    1995-01-12

    We discuss the physics of vortices in the circumstellar disks associated with young stellar objects. We elucidate the basic physical properties of these localized storm systems. In particular, we consider point vortices, linear vortices, the effects of self-gravity, magnetic fields, and nonlinear aspects of the problem. We find that these vortices can exist in many different forms in the disks of young stellar objects and may play a role in the formation of binary companions and/or giant planets. Vortices may enhance giant planet formation via gravitational instability by allowing dust grains (heavy elements) to settle to the center on a short timescale; the gravitational instability itself is also enhanced because the vortices also create a larger local surface density in the disk. In addition, vortices can enhance energy dissipation in disks and thereby affect disk accretion. Finally, we consider the possibility that vortices of this type exist in molecular clouds and in the disk of the galaxy itself. On all of these size scales, vortices can produce long-lived structures which may correspond to observed structures in these systems.

  5. Sleep Habits and Diabetes

    MedlinePLUS Videos and Cool Tools

    ... news/Sleep_Habits_040215.html Sleep Habits and Diabetes HealthDay News Video - April 2, 2015 To use ... please enable JavaScript. Play video: Sleep Habits and Diabetes For closed captioning, click the CC button on ...

  6. Response of Atmospheric Biomarkers to NOx-induced Photochemistry Generated by Stellar Cosmic Rays for Earth-like Planets in the Habitable Zone of M-Dwarf Stars

    E-print Network

    Grenfell, John Lee; von Paris, Philip; Patzer, Beate; Lammer, Helmut; Stracke, Barbara; Gebauer, Stefanie; Schreier, Franz; Rauer, Heike

    2015-01-01

    Understanding whether M-dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M-dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N2), which leads to production of nitrogen oxides in the planetary atmosphere, hence affecting biomarkers such as ozone. We apply a stationary model, that is, without a time-dependence, hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by t...

  7. FOR RELEASE: 9:20 AM EST, January 7, 2002 ORBITAL STABILITY OF EARTH-LIKE PLANETS IN STELLAR HABITABLE

    E-print Network

    Texas at Arlington, University of

    FOR RELEASE: 9:20 AM EST, January 7, 2002 ORBITAL STABILITY OF EARTH-LIKE PLANETS IN STELLAR HABITABLE ZONES Long-term orbital stability of Earth-like planets in stellar habitable zones is nec- essary of terrestrial planets inside the habitable zones of three selected stellar systems with newly discovered giant

  8. Circumbinary habitability niches

    NASA Astrophysics Data System (ADS)

    Mason, Paul A.; Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A.; Clark, Joni M.

    2015-07-01

    Binaries could provide the best niches for life in the Galaxy. Although counterintuitive, this assertion follows directly from stellar tidal interaction theory and the evolution of lower mass stars. There is strong evidence that chromospheric activity of rapidly rotating young stars may be high enough to cause mass loss from atmospheres of potentially habitable planets. The removal of atmospheric water is most critical. Tidal breaking in binaries could help reduce magnetic dynamo action and thereby chromospheric activity in favour of life. We call this the Binary Habitability Mechanism (BHM) that we suggest allows for water retention at levels comparable to or better than the Earth. We discuss novel advantages that life may exploit, in these cases, and suggest that life may even thrive on some circumbinary planets. We find that while many binaries do not benefit from BHM, high-quality niches do exist for various combinations of stars between 0.55 and 1.0 solar masses. For a given pair of stellar masses, BHM operates only for certain combinations of period and eccentricity. Binaries having a solar-type primary seem to be quite well-suited niches having wide and distant habitable zones with plentiful water and sufficient light for photosynthetic life. We speculate that, as a direct result of BHM, conditions may be suitable for life on several planets and possibly even moons of giant planets orbiting some binaries. Lower mass combinations, while more restrictive in parameter space, provide niches lasting many billions of years and are rich suppliers of photosynthetic photons. We provide a publicly available web-site (http://bit.ly/BHM-calculator or http://bit.ly/BHM-calculator-mirror), which calculates the BHM effects presented in this paper.

  9. Habitability of Planets Orbiting Cool Stars

    E-print Network

    Barnes, Rory; Domagal-Goldman, Shawn D; Heller, Rene; Jackson, Brian; Lopez-Morales, Mercedes; Tanner, Angelle; Gomez-Perez, Natalia; Ruedas, Thomas

    2010-01-01

    Terrestrial planets are more likely to be detected if they orbit M dwarfs due to the favorable planet/star size and mass ratios. However, M dwarf habitable zones are significantly closer to the star than the one around our Sun, which leads to different requirements for planetary habitability and its detection. We review 1) the current limits to detection, 2) the role of M dwarf spectral energy distributions on atmospheric chemistry, 3) tidal effects, stressing that tidal locking is not synonymous with synchronous rotation, 4) the role of atmospheric mass loss and propose that some habitable worlds may be the volatile-rich, evaporated cores of giant planets, and 5) the role of planetary rotation and magnetic field generation, emphasizing that slow rotation does not preclude strong magnetic fields and their shielding of the surface from stellar activity. Finally we present preliminary findings of the NASA Astrobiology Institute's workshop "Revisiting the Habitable Zone." We assess the recently-announced planet ...

  10. Habitable planet finder

    NASA Astrophysics Data System (ADS)

    Ditto, Thomas D.

    2012-09-01

    A notional space telescope configuration is presented that addresses issues of angular resolution, spectral bandwidth and rejection of host star glare by means of a double dispersion architecture. The telescope resolves angle by wavelength. In an earlier embodiment for surveys, a primary objective grating telescope architecture was shown to acquire millions of objects in one observation cycle, one wave length at a time. The proposed HPF can detect exquisite spectral signatures out of millions of wavelengths in albedos - one exoplanetary system at a time. Like its predecessor, the new HPF telescope has a ribbon-shaped flat gossamer membrane primary objective that lends itself to space deployment, but the preferred embodiment uses a holographic optical element rather than a plane grating. The HOE provides an improvement in efficiency at select wavelength bands. The considerable length of the membrane can be in the 100 meter class providing angular resolution sufficient to resolve planets in the habitable zone and also spectral resolution sufficient to earmark habitability. A novel interferometric secondary spectrograph rejects host star glare. However, the architecture cannot disambiguate multiple stellar sources and may require unprecedented focal lengths in the primary objective to isolate one system at a time.

  11. Internal morphology, habit and U-Th-Pb microanalysis of amphibolite-to-granulite facies zircons: geochronology of the Ivrea Zone (Southern Alps)

    Microsoft Academic Search

    Gerhard Vavra; Rolf Schmid; Dieter Gebauer

    1999-01-01

    Several types of growth morphologies and alteration mechanisms of zircon crystals in the high-grade metamorphic Ivrea Zone\\u000a (IZ) are distinguished and attributed to magmatic, metamorphic and fluid-related events. Anatexis of pelitic metasediments\\u000a in the IZ produced prograde zircon overgrowths on detrital cores in the restites and new crystallization of magmatic zircons\\u000a in the associated leucosomes. The primary morphology and Th-U

  12. Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone

    E-print Network

    Joshi, M

    2012-01-01

    M-stars comprise 80% of main-sequence stars, and so their planetary systems provide the best chance for finding habitable planets, i.e.: those with surface liquid water. We have modelled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M-stars) using spectrally resolved data of the Earth's cryosphere. The gradual reduction of the albedos of snow and ice at wavelengths greater than 1 ?m, combined with M-stars emitting a significant fraction of their radiation at these same longer wavelengths, mean that the albedos of ice and snow on planets orbiting M-stars are much lower than their values on Earth. Our results imply that the ice/snow albedo climate feedback is significantly weaker for planets orbiting M-stars than for planets orbiting G-type stars such as the Sun. In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of c...

  13. Living with an Old Red Dwarf: X-ray-UV Emissions of Kapteyn’s Star - Effects of X-UV radiation on Habitable Zone Planets hosted by old Red Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Guinan, Edward F.; Durbin, Allyn J.; Engle, Scott G.

    2015-01-01

    Red dwarfs (dM) stars make up over 75% of the local stellar population and a significant fraction (~40-50%) are older than the Sun. Because of the high frequency of red dwarfs and their longevity (> 50 Gyr), there is a greater possibility of more advanced life in red dwarf-exoplanet systems. MEarths, UVES, SDSS-III, and the upcoming TESS mission are some surveys that are targeting red dwarfs in the search for hosted potentially habitalble planets. As part of Villanova's 'Living with a Red Dwarf' program, we have obtained HST-COS Ultraviolet spectra (1150-3000A) and Chandra X-ray observations of Kapteyn's star (GJ 191; M1 V, V = 8.85 mag , d = 12.76 +/- 0.05 ly). Kapyteyn's Star is important for the study of old red dwarfs because it is the nearest (Pop II) halo star with a radial velocity of +245.2 km/s and an estimated age of 11.2 +/-0.9 Gyrs. Recently Kapteyn's Star was found to host two super-Earth mass planets - one of these is orbiting inside the star's Habitable Zone (Anglada-Escude' 2014: MNRAS 443, L89). In our program, Kapteyn's star is the oldest red dwarf and as such serves as an anchor for our age, rotation, and activity relations. The spectra obtained from HST/COS provide one of the cleanest measurements of the important HI Lyman-alpha 1215.6 A emission flux for red dwarfs. This is due to the large Doppler shift from the high radial velocity, separating the stellar Ly-alpha emission from by the Ly-alpha ISM and local geo-coronal sources. These observations further provide calibrations at the old age/low rotation/low activity extremes for our relations. As the nearest and brightest old red dwarf star, Kapteyn's Star also provides insights into its magnetic properties to investigae coronal x-ray and UV emission for the large population of old, slowly rotating red dwarf stars. Kapteyn's star also serves as a proxy for the numerous metal-poor old disk - Pop II M dwarfs by providing information about X-UV emissions. This information is crucial for determining X-ray-UV irradiances for habitable zone planets hosted by these old numerous, cool low luminosity stars.We gratefully acknowledge the support from NSF/RUI Grant AST-1009903, NASA/Chandra Grants GO2-13020X, and HST-GO-13020

  14. Effects of Exoplanet Planetesimal Carbon Chemistry on Habitability

    NASA Astrophysics Data System (ADS)

    Johnson, Torrence V.; Mousis, O.; Lunine, J. I.; Madhusudhan, N.

    2013-10-01

    We explore the effects of reported differences in C/O values for exoplanet host stars on the composition of planetesimals formed beyond the snow line in these systems. Since the value of C/O in a planet forming nebula has a strong effect on amount of oxygen available for water ice in an oxidizing nebula, exoplanet systems for host stars with C/O greater than the solar value may have planetesimals with very little or no water ice. We have estimated the composition of volatile and refractory material in extrasolar planetesimals using a set of stars with a wide range of measured C/O abundances (Johnson et al. ApJ. 757(2), 192, 2012). The volatile ice content of planetesimals in these systems varies significantly with C/O, controlled primarily by the availability of O for H2 O ice condensation. Systems with C/O less than the solar value (C/O = 0.55) should have very water ice rich planetesimals, while water ice mass fraction decreases rapidly with increasing C/O until only ices of CO and CO2 are left in significant proportions. If a significant fraction of C is in the form of refractory CHON particles, C and O are removed from the gas phase and the condensates for super-solar C/O values will be water-poor mixtures of silicates and metal, carbon, and carbon-bearing volatile ices, depending on temperature. For very carbon-rich systems, oxidizing conditions cannot be sustained beyond about C/O=1, due to the oxygen sequestered in solid silicates, oxides and CHON, for refractory C fractions within the Pollack et al. range of 0.4 - 0.7 (ApJ. 421, 615, 1994). These results have implications for assessing the habitability of exoplanets since they constrain the amount of water available beyond the snow line for dynamical delivery to inner planets, depending on the host star’s C/O in the circumstellar nebula. Thus one the key chemical ingredients for habitability may be in short supply in carbon-rich, oxygen-poor systems even if planets exist in the ‘habitable zone’. TVJ acknowledges government support at JPL/Caltech, under a contract with NASA. NM acknowledges support from Yale University. JIL was supported by the JWST Project through NASA. O.M. acknowledges support from CNES.

  15. Effects of Exoplanet Planetesimal Carbon Chemistry on Habitability

    NASA Astrophysics Data System (ADS)

    Johnson, T. V.; Mousis, O.; Lunine, J. I.; Madhusudhan, N.

    2013-12-01

    We explore the effects of reported differences in C/O values for exoplanet host stars on the composition of planetesimals formed beyond the snow line in these systems. Since the value of C/O in a planet forming nebula has a strong effect on amount of oxygen available for water ice in an oxidizing nebula, exoplanet systems for host stars with C/O greater than the solar value may have planetesimals with very little or no water ice. We have estimated the composition of volatile and refractory material in extrasolar planetesimals using a set of stars with a wide range of measured C/O abundances (Johnson et al. ApJ. 757(2), 192, 2012). The volatile ice content of planetesimals in these systems varies significantly with C/O, controlled primarily by the availability of O for H2O ice condensation. Systems with C/O less than the solar value (C/O = 0.55) should have very water ice rich planetesimals, while water ice mass fraction decreases rapidly with increasing C/O until only ices of CO and CO2 are left in significant proportions. If a significant fraction of C is in the form of refractory CHON particles, C and O are removed from the gas phase and the condensates for super-solar C/O values will be water-poor mixtures of silicates and metal, carbon, and carbon-bearing volatile ices, depending on temperature. For very carbon-rich systems, oxidizing conditions cannot be sustained beyond about C/O=1, due to the oxygen sequestered in solid silicates, oxides and CHON, for refractory C fractions within the Pollack et al. range of 0.4 - 0.7 (ApJ. 421, 615, 1994). These results have implications for assessing the habitability of exoplanets since they constrain the amount of water available beyond the snow line for dynamical delivery to inner planets, depending on the host star's C/O in the circumstellar nebula. Thus one the key chemical ingredients for habitability may be in short supply in carbon-rich, oxygen-poor systems even if planets exist in the ';habitable zone'. TVJ acknowledges government support at JPL/Caltech, under a contract with NASA. NM acknowledges support from Yale University. JIL was supported by the JWST Project through NASA. O.M. acknowledges support from CNES.Planetesimal compositions for several stellar systems with a fraction, Csolid, of C in solid CHON particles

  16. Response of Atmospheric Biomarkers to NOx-Induced Photochemistry Generated by Stellar Cosmic Rays for Earth-like Planets in the Habitable Zone of M Dwarf Stars

    PubMed Central

    Grießmeier, Jean-Mathias; von Paris, Philip; Patzer, A. Beate C.; Lammer, Helmut; Stracke, Barbara; Gebauer, Stefanie; Schreier, Franz; Rauer, Heike

    2012-01-01

    Abstract Understanding whether M dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N2), which leads to production of nitrogen oxides (NOx) in the planetary atmosphere, hence affecting biomarkers such as ozone (O3). We apply a stationary model, that is, without a time dependence; hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by the impinging stellar flares. This point should be further explored in future work with time-dependent models. We estimate the NOx production using an air shower approach and evaluate the implications using a climate-chemical model of the planetary atmosphere. O3 formation proceeds via the reaction O+O2+M?O3+M. At high NOx abundances, the O atoms arise mainly from NO2 photolysis, whereas on Earth this occurs via the photolysis of molecular oxygen (O2). For the flaring case, O3 is mainly destroyed via direct titration, NO+O3?NO2+O2, and not via the familiar catalytic cycle photochemistry, which occurs on Earth. For scenarios with low O3, Rayleigh scattering by the main atmospheric gases (O2, N2, and CO2) became more important for shielding the planetary surface from UV radiation. A major result of this work is that the biomarker O3 survived all the stellar-activity scenarios considered except for the strong case, whereas the biomarker nitrous oxide (N2O) could survive in the planetary atmosphere under all conditions of stellar activity considered here, which clearly has important implications for missions that aim to detect spectroscopic biomarkers. Key Words: M dwarf—Atmosphere—Earth-like—Biomarkers—Stellar cosmic rays. Astrobiology 12, 1109–1122. PMID:23215581

  17. Response of atmospheric biomarkers to NO(x)-induced photochemistry generated by stellar cosmic rays for earth-like planets in the habitable zone of M dwarf stars.

    PubMed

    Grenfell, John Lee; Grießmeier, Jean-Mathias; von Paris, Philip; Patzer, A Beate C; Lammer, Helmut; Stracke, Barbara; Gebauer, Stefanie; Schreier, Franz; Rauer, Heike

    2012-12-01

    Understanding whether M dwarf stars may host habitable planets with Earth-like atmospheres and biospheres is a major goal in exoplanet research. If such planets exist, the question remains as to whether they could be identified via spectral signatures of biomarkers. Such planets may be exposed to extreme intensities of cosmic rays that could perturb their atmospheric photochemistry. Here, we consider stellar activity of M dwarfs ranging from quiet up to strong flaring conditions and investigate one particular effect upon biomarkers, namely, the ability of secondary electrons caused by stellar cosmic rays to break up atmospheric molecular nitrogen (N(2)), which leads to production of nitrogen oxides (NO(x)) in the planetary atmosphere, hence affecting biomarkers such as ozone (O(3)). We apply a stationary model, that is, without a time dependence; hence we are calculating the limiting case where the atmospheric chemistry response time of the biomarkers is assumed to be slow and remains constant compared with rapid forcing by the impinging stellar flares. This point should be further explored in future work with time-dependent models. We estimate the NO(x) production using an air shower approach and evaluate the implications using a climate-chemical model of the planetary atmosphere. O(3) formation proceeds via the reaction O+O(2)+M?O(3)+M. At high NO(x) abundances, the O atoms arise mainly from NO(2) photolysis, whereas on Earth this occurs via the photolysis of molecular oxygen (O(2)). For the flaring case, O(3) is mainly destroyed via direct titration, NO+O(3)?NO(2)+O(2), and not via the familiar catalytic cycle photochemistry, which occurs on Earth. For scenarios with low O(3), Rayleigh scattering by the main atmospheric gases (O(2), N(2), and CO(2)) became more important for shielding the planetary surface from UV radiation. A major result of this work is that the biomarker O(3) survived all the stellar-activity scenarios considered except for the strong case, whereas the biomarker nitrous oxide (N(2)O) could survive in the planetary atmosphere under all conditions of stellar activity considered here, which clearly has important implications for missions that aim to detect spectroscopic biomarkers. PMID:23215581

  18. Al-26 and circumstellar envelopes

    NASA Technical Reports Server (NTRS)

    Glassgold, A. E.

    1995-01-01

    The effects of the radioactive decay of Al-26 on the circumstellar envelopes of asymptotic giant branch stars are analyzed. The gamma-rays emitted by the product nucleus Mg-26 escape most envelopes, but the beta-decay positrons are stopped and can ionize and heat the gas. The ionization may produce observable effects in C-rich circumstellar envelopes, particularly if the photospheric Al-26 abundance is as large as inferred from measurements of live Al-26 in the primitive solar nebula or the observations of interstellar 1.8 MeV gamma-rays. For the nearby carbon star IRC +10216, the measured abundance of the molecular ion HCO(+) provides an upper limit of about 4 x 10(exp -3) for the photospheric Al-26/Al-27 ratio, consistent with presolar SiC grains with about the same C-12/C-13 ratio.

  19. Geophysical and atmospheric evolution of habitable planets.

    PubMed

    Lammer, Helmut; Selsis, Frank; Chassefière, Eric; Breuer, Doris; Griessmeier, Jean-Mathias; Kulikov, Yuri N; Erkaev, Nikolai V; Khodachenko, Maxim L; Biernat, Helfried K; Leblanc, Francois; Kallio, Esa; Lundin, Richard; Westall, Frances; Bauer, Siegfried J; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Gröller, Hannes; Hanslmeier, Arnold; Hausleitner, Walter; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Léger, Alain; Leitzinger, Martin; Lichtenegger, Herbert I M; Liseau, René; Lunine, Jonathan; Motschmann, Uwe; Odert, Petra; Paresce, Francesco; Parnell, John; Penny, Alan; Quirrenbach, Andreas; Rauer, Heike; Röttgering, Huub; Schneider, Jean; Spohn, Tilman; Stadelmann, Anja; Stangl, Günter; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

    2010-01-01

    The evolution of Earth-like habitable planets is a complex process that depends on the geodynamical and geophysical environments. In particular, it is necessary that plate tectonics remain active over billions of years. These geophysically active environments are strongly coupled to a planet's host star parameters, such as mass, luminosity and activity, orbit location of the habitable zone, and the planet's initial water inventory. Depending on the host star's radiation and particle flux evolution, the composition in the thermosphere, and the availability of an active magnetic dynamo, the atmospheres of Earth-like planets within their habitable zones are differently affected due to thermal and nonthermal escape processes. For some planets, strong atmospheric escape could even effect the stability of the atmosphere. PMID:20307182

  20. Dynamical habitability of planetary systems.

    PubMed

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

    2010-01-01

    The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries). PMID:20307181

  1. TIDAL LIMITS TO PLANETARY HABITABILITY

    SciTech Connect

    Barnes, Rory [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Jackson, Brian; Greenberg, Richard [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Raymond, Sean N. [Virtual Planetary Laboratory (United States)

    2009-07-20

    The habitable zones (HZs) of main-sequence stars have traditionally been defined as the range of orbits that intercept the appropriate amount of stellar flux to permit surface water on a planet. Terrestrial exoplanets discovered to orbit M stars in these zones, which are close-in due to decreased stellar luminosity, may also undergo significant tidal heating. Tidal heating may span a wide range for terrestrial exoplanets and may significantly affect conditions near the surface. For example, if heating rates on an exoplanet are near or greater than that on Io (where tides drive volcanism that resurfaces the planet at least every 1 Myr) and produce similar surface conditions, then the development of life seems unlikely. On the other hand, if the tidal heating rate is less than the minimum to initiate plate tectonics, then CO{sub 2} may not be recycled through subduction, leading to a runaway greenhouse that sterilizes the planet. These two cases represent potential boundaries to habitability and are presented along with the range of the traditional HZ for main-sequence, low-mass stars. We propose a revised HZ that incorporates both stellar insolation and tidal heating. We apply these criteria to GJ 581 d and find that it is in the traditional HZ, but its tidal heating alone may be insufficient for plate tectonics.

  2. On the Habitability of Aquaplanets

    NASA Astrophysics Data System (ADS)

    Cardenas, Rolando; Perez, Noel; Martinez-Frias, Jesus; Martin, Osmel

    2014-08-01

    An Aquatic Habitability Index is proposed, based on Quantitative Habitability Theory, and considering a very general model for life. It is a primary habitability index, measuring habitability for phytoplankton in the first place. The index is applied to some case studies, such as the habitability changes in Earth due to environmental perturbations caused by asteroid impacts.

  3. Teenagers Media Habits.

    ERIC Educational Resources Information Center

    Campbell, Laurence R.

    This study attempted to determine what media most effectively communicated to teenagers, how the media habits of Florida teenagers compared with those in other states, and how the media habits of journalism students compared with those not in journalism. A total of 430 students from Florida high schools and 457 from high schools in other states…

  4. Changing circumstances, disrupting habits.

    PubMed

    Wood, Wendy; Witt, Melissa Guerrero; Tam, Leona

    2005-06-01

    The present research investigated the mechanisms guiding habitual behavior, specifically, the stimulus cues that trigger habit performance. When usual contexts for performance change, habits cannot be cued by recurring stimuli, and performance should be disrupted. Thus, the exercising, newspaper reading, and TV watching habits of students transferring to a new university were found to survive the transfer only when aspects of the performance context did not change (e.g., participants continued to read the paper with others). In some cases, the disruption in habits also placed behavior under intentional control so that participants acted on their current intentions. Changes in circumstances also affected the favorability of intentions, but changes in intentions alone could not explain the disruption of habits. Furthermore, regardless of whether contexts changed, nonhabitual behavior was guided by intentions. PMID:15982113

  5. X-ray and Hubble/COS UV Measures of Kapteyn's Star: A Crucial Proxy of X-UV Irradiances for Old Red Dwarf Stars that May Host Habitable Zone Planets

    NASA Astrophysics Data System (ADS)

    Durbin, Allyn J.; Guinan, E. F.; Engle, S. G.

    2014-01-01

    Red dwarfs (dM) stars make up over 80% of the local stellar population and a significant fraction of them are old (age > 4 Gyr). Because of the high frequency of red dwarfs and their longevity, there is a greater possibility of more advanced life in red dwarf planet systems. MEarths, UVES, SDSS-III, and the upcoming TESS mission are some surveys that are targeting these objects. As part of Villanova’s Living with a Red Dwarf program, we have obtained HST/COS spectra and Chandra X-ray observations of Kapteyn's star (M1V, V = 8.853, d = 12.76 +/- 0.05 ly, P_rot = 195 days). This star is crucial to the study of old red dwarfs as it is the nearest halo star with a radial velocity of +245.2 km/s and an estimated age of 10-12 Gyr. In our program, Kapteyn's star is the oldest red dwarf and as such serves as an anchor for our age, rotation, and activity relations. The spectra obtained from HST/COS provide one of the cleanest measurements of Lyman-alpha emission for red dwarfs. This is due to Doppler shift from the high radial velocity, separating the Lyman-alpha line from emission produced by the ISM and geocoronal sources. These observations further provide calibration at the old age/low rotation/low activity extremes for our relations. They also provide insights into the magnetic properties as investigating coronal x-ray and UV emission in very old, slowly rotating dM stars. Kapteyn’s star also serves as a proxy for metal-poor old disk/Pop II M dwarfs by providing information about X-UV emissions. This information is crucial for determining X-UV irradiances of possible habitable zone planets hosted by old red dwarfs. We gratefully acknowledge the support from NSF/RUI Grant AST-1009903, NASA/Chandra Grants GO1-12124X and GO2-13020X, and HST-GO-13020.

  6. WHERE TO FIND HABITABLE ''EARTHS'' IN CIRCUMBINARY SYSTEMS

    SciTech Connect

    Liu Huigen; Zhang Hui; Zhou Jilin, E-mail: huigen@nju.edu.cn [School of Astronomy and Space Science and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210093 (China)

    2013-04-20

    Six P-type planets have been found thus far around five binary systems, i.e., Kepler-16b, 34b, 35b, 38b, and 47b and c, which are all Neptune- or Jupiter-like planets. The stability of planets and the habitable zones are influenced by the gravitational and radiative perturbations of binary companions. In this Letter, we check the stability of an additional habitable Earth-mass planet in each system. Based on our simulations in 10 Myr, a habitable ''Earth'' is hardly stable in Kepler-16, while a stable ''Earth'' in Kepler-47 close to the boundaries of the habitable zone is possible. In contrast, Kepler-34, 35, and 38 seem to have high probabilities of being able to tolerante a stable ''Earth'' in their habitable zones. The affects of transit time variations are quite small due to the small mass of an undetected ''Earth,'' except that of Kepler-16b. With a time precision of 10{sup -3} day ({approx}88 s), an ''Earth'' in the corotational resonance with Kepler-16b can be detected in three years, while habitable ''Earths'' in the Kepler-34 and 38 systems can be detected in 10 yr. Habitable ''Earths'' in Kepler-35 and 47 are not likely to be detected in 10 yr under this precision.

  7. The Role of Planetary System Architecture in Planetary Habitability

    NASA Astrophysics Data System (ADS)

    Barnes, R.; Jackson, B.; Raymond, S.; Greenberg, R.

    2009-12-01

    Traditionally, the habitable zone is defined as the region around a star in which liquid water can be stable on a planetary surface. At first these calculations considered planets on circular orbits [1]. More recent investigations into nonzero orbital eccentricities found that the limits of the habitable zone should reflect the orbit-averaged flux a planet receives [2]. However, those studies assumed the potentially habitable planet is isolated. If additional planets are in the system, gravitational interactions between planets can cause eccentricity oscillations on timescales of 103 - 106 years. Furthermore, the known multi-planet systems (generally consisting of giant planets) appear to undergo large amplitude eccentricity oscillations [3]. If rocky exoplanets also experience such large variations, then the orbit-averaged flux may change significantly, impacting habitability. We show that plausible architectures of rocky planet systems can indeed lead to orbits with large eccentricity cycles. Moreover, some planets could cross either the inner or outer habitable zone boundaries due to these oscillations. We therefore suggest that the shape of actual habitable zones depends critically on the configuration (orbits and masses) of the entire planetary system. [1] Kasting, J.F. et al. 1993, Icarus, 101, 108. [2] Williams, D.M. & Pollard, D. 2002, I. J. AsBio, 2, 1. [3] Barnes, R., & Greenberg, R. 2006, Astrophys. J., 652, L53.

  8. A Review of Habit Reversal with Childhood Habit Disorders.

    ERIC Educational Resources Information Center

    Woods, Douglas W.; Miltenberger, Raymond G.

    1996-01-01

    This paper first reviews four classes of habit disorders in children: motor and vocal tics, nervous habits, stuttering, and Tourette's disorder. It then describes the habit reversal procedure and reviews the literature on its use and variations to treat each of the four classes of habit disorders. Emphasis is on simplified versions of the original…

  9. Damaging Oral Habits

    PubMed Central

    Kamdar, Rajesh J; Al-Shahrani, Ibrahim

    2015-01-01

    Oral habits, if persist beyond certain developmental age, can pose great harm to the developing teeth, occlusion, and surrounding oral tissues. In the formative years, almost all children engage in some non-nutritive sucking habits. Clinicians, by proper differential diagnosis and thorough understanding of natural growth and developmental processes, should take a decision for intervening. This article describes case series reports of thumb sucking, finger sucking, and tongue thrusting habits, which have been successfully treated by both removable and fixed orthodontic appliances. The cases shown are ranging from the age group of 9-19 years presenting combination of both mixed and permanent dentition development. All cases show satisfactory correction of habits and stable results. PMID:25954079

  10. Damaging oral habits.

    PubMed

    Kamdar, Rajesh J; Al-Shahrani, Ibrahim

    2015-04-01

    Oral habits, if persist beyond certain developmental age, can pose great harm to the developing teeth, occlusion, and surrounding oral tissues. In the formative years, almost all children engage in some non-nutritive sucking habits. Clinicians, by proper differential diagnosis and thorough understanding of natural growth and developmental processes, should take a decision for intervening. This article describes case series reports of thumb sucking, finger sucking, and tongue thrusting habits, which have been successfully treated by both removable and fixed orthodontic appliances. The cases shown are ranging from the age group of 9-19 years presenting combination of both mixed and permanent dentition development. All cases show satisfactory correction of habits and stable results. PMID:25954079

  11. Habitability: CAMELOT 4

    NASA Technical Reports Server (NTRS)

    Alequin, W.; Barragan, A.; Carro, M.; Garcia, F.; Gonzalez, I.; Mercado, J. A.; Negron, N.; Lopez, D.; Rivera, L. A.; Rivera, M.

    1990-01-01

    During 1988 to 1989 the NASA/USRA Advanced Design Program sponsored research and design efforts aimed at developing habitability criteria and at defining a habitability concept as a useful tool in understanding and evaluating dwellings for prolonged stays in extraterrestrial space. The Circulating Auto sufficient Mars-Earth Luxurious Orbital Transport (CAMELOT) was studied as a case in which the students would try to enhance the quality of life of the inhabitants by applying architectural design methodology. The study proposed 14 habitability criteria considered necessary to fulfill the defined habitability concept, which is that state of equilibrium that results from the interaction between components of the Individual Architecture Mission Complex, which allows a person to sustain physiological homeostatis, adequate performance, and acceptable social relationships. Architecture, design development, refinements and revisions to improve the quality of life, new insights on artificial gravity, form and constitution problems, and the final design concept are covered.

  12. Habitability study shuttle orbiter

    NASA Technical Reports Server (NTRS)

    1972-01-01

    Studies of the habitability of the space shuttle orbiter are briefly summarized. Selected illustrations and descriptions are presented for: crew compartment, hygiene facilities, food system and galley, and storage systems.

  13. Habitability design for spacecraft

    NASA Technical Reports Server (NTRS)

    Franklin, G. C.

    1978-01-01

    Habitability is understood to mean those spacecraft design elements that involve a degree of comfort, quality or necessities to support man in space. These elements are environment, architecture, mobility, clothing, housekeeping, food and drink, personal hygiene, off-duty activities, each of which plays a substantial part in the success of a mission. Habitability design for past space flights is discussed relative to the Mercury, Gemini, Apollo, and Skylab spacecraft, with special emphasis on an examination of the Shuttle Orbiter cabin design from a habitability standpoint. Future projects must consider the duration and mission objectives to meet their habitability requirements. Larger ward rooms, improved sleeping quarters and more complete hygiene facilities must be provided for future prolonged space flights

  14. NASA: Habitable Worlds

    NSDL National Science Digital Library

    NASA's Habitable Worlds website encourages visitors to "search the solar system for signs of life," by selecting a "World to Explore." This creatively designed website smartly displays our solar system's colorful planets or worlds amidst the dark background of space. In order to gain in-depth information specific to each planet, users simply click on the world of their choosing. Each planet page provides beautiful images and information about habitability, moons, and more.

  15. Habitable Planets with High Obliquities

    NASA Astrophysics Data System (ADS)

    Williams, D. M.; Kasting, J. F.

    1996-03-01

    The obliquities of the terrestrial planets have been shown to vary chaotically and by large amounts in times less than 10 Myr, thus inviting the possibility for Earth to occasionally reach high obliquity where it might experience climatic conditions unfavorable for life. Although Earth escapes this fate by having its rotation axis stabilized by the Moon, many extrasolar Earth-like planets without large satellites should be subjected to periods of high obliquity. The number of worlds supporting life outside the Solar System, then, may be far fewer than has been suggested if high obliquities render moon-less Earths uninhabitable. Climates at high obliquity are particularly harsh on middle and high latitude continents that warm and cool rapidly in response to large insolation swings. These areas exhibit a wide range of temperatures over a seasonal cycle, with extremes reaching well above or below 273 Kelvin, making them seasonally unsuitable for water-dependent life. We demonstrate here that Earth-like planets will have their temperature extremes mitigated at high obliquity if they possess dense CO2 atmospheres, as is likely for many planets situated in the outer habitable zone (HZ) of a Sun-like star. The climate stabilizing mechanism governing atmospheric CO2 on Earth-like planets is carbonate-silicate weathering. Planets with atmospheres rich in CO2 demonstrate small latitudinal temperature gradients and seasonal temperature cycles, and thus remain habitable at high obliquities.

  16. Habitability of Planets Orbiting Binaries Consisting of Solar Mass Twins

    NASA Astrophysics Data System (ADS)

    Mason, Paul A.; Zuluaga, Jorge I.; Zhilkin, Andrey G.; Bisikalo, Dmitry V.

    2015-01-01

    An important problem in astrobiology is the study of the potential habitability of planets orbiting binary stars. Theoretical and observational studies of circumbinary planets indicate that it is not uncommon for circumbinary planets to be located in the habitable zones surrounding main sequence binaries. However, it is also clear that the time evolution of stellar activity of the individual stars in close binaries is of primary concern for the habitability of planets. For example, planets orbiting active stars may lose the entirety of their water budget due to atmospheric mass loss; despite being in the standard radiative habitable zone. Alternatively, stars in some binaries may undergo a reduction in stellar activity due to tidal effects that cause the rotation of the stars to slow faster than single stars. Thereby, magneto-coronal activity is reduced to less aggressive levels, allowing circumbinary planets to maintain surface water. We summarize these effects, which we call the Binary Habitability Mechanism (BHM). We performed orbital integrations of circumbinary, Earth-like, planets and find that resonances play a particularly important role in the stability of habitable zone planets orbiting solar twin binaries in the 20-60 day period range, allowing for the possibility of several habitable planets orbiting some binaries. We present numerical simulations of the effects of colliding winds in binaries containing solar mass twins. We used stellar wind parameters based on solar like conditions for our 3D hydrodynamic simulations. We find devastating effects for close in planets, yet relatively mild stellar wind conditions exist within the circumbinary habitable zone.

  17. ABUNDANT CIRCUMSTELLAR SILICA DUST AND SiO GAS CREATED BY A GIANT HYPERVELOCITY COLLISION IN THE {approx}12 MYR HD172555 SYSTEM

    SciTech Connect

    Lisse, C. M. [JHU-APL, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Chen, C. H. [STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Wyatt, M. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Morlok, A. [Open University, Milton Keynes, MK7 6AA (United Kingdom); Song, I. [Department of Physics and Astronomy, University of Georgia, Athens, GA 30602 (United States); Bryden, G. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Sheehan, P. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States)], E-mail: carey.lisse@jhuapl.edu, E-mail: cchen@stsci.edu, E-mail: wyatt@ast.cam.ac.uk, E-mail: A.Morlok@open.ac.uk, E-mail: song@uga.edu, E-mail: Geoffrey.Bryden@jpl.nasa.gov, E-mail: psheeha2@mail.rochester.edu

    2009-08-20

    The fine dust detected by infrared (IR) emission around the nearby {beta} Pic analog star HD172555 is very peculiar. The dust mineralogy is composed primarily of highly refractory, nonequilibrium materials, with approximately three quarters of the Si atoms in silica (SiO{sub 2}) species. Tektite and obsidian lab thermal emission spectra (nonequilibrium glassy silicas found in impact and magmatic systems) are required to fit the data. The best-fit model size distribution for the observed fine dust is dn/da = a {sup -3.95{+-}}{sup 0.10}. While IR photometry of the system has stayed stable since the 1983 IRAS mission, this steep a size distribution, with abundant micron-sized particles, argues for a fresh source of material within the last 0.1 Myr. The location of the dust with respect to the star is at 5.8 {+-} 0.6 AU (equivalent to 1.9 {+-} 0.2 AU from the Sun), within the terrestrial planet formation region but at the outer edge of any possible terrestrial habitability zone. The mass of fine dust is 4 x 10{sup 19}-2 x 10{sup 20} kg, equivalent to a 150-200 km radius asteroid. Significant emission features centered at 4 and 8 {mu}m due to fluorescing SiO gas are also found. Roughly 10{sup 22} kg of SiO gas, formed by vaporizing silicate rock, is also present in the system, and a separate population of very large, cool grains, massing 10{sup 21}-10{sup 22} kg and equivalent to the largest sized asteroid currently found in the solar system's main asteroid belt, dominates the solid circumstellar material by mass. The makeup of the observed dust and gas, and the noted lack of a dense circumstellar gas disk, strong stellar X-ray activity, and an extended disk of {beta} meteoroids argues that the source of the observed circumstellar materials is a giant hypervelocity (>10 km s{sup -1}) impact between large rocky planetesimals, similar to the ones which formed the Moon and which stripped the surface crustal material off of Mercury's surface.

  18. A Quick Study of Science Return from Direct Imaging Exoplanet Missions: Detection and Characterization of Circumstellar Material with an AFTA or EXO-C/S CGI

    E-print Network

    Schneider, Glenn

    2014-01-01

    The capabilities of a high (~ 10^-9 resel^-1) contrast, narrow-field, coronagraphic instrument (CGI) on a space-based AFTA-C or probe-class EXO-C/S mission, conceived to study the diversity of exoplanets now known to exist into stellar habitable zones, are particularly and importantly germane to symbiotic studies of the systems of circumstellar (CS) material from which planets have emerged and interact with throughout their lifetimes. The small particle populations in "disks" of co-orbiting materials can trace the presence of planets through dynamical interactions that perturb the spatial distribution of the light-scattering debris, detectable at optical wavelengths and resolvable with an AFTA-C or EXO-S/C CGI. Herein we: (1) present the science case to study the formation, evolution, architectures, diversity, and properties of the material in the planet-hosting regions of nearby stars, (2) discuss how a CGI under current conception can uniquely inform and contribute to those investigations, (3) consider the ...

  19. Trajectories of Martian Habitability

    PubMed Central

    2014-01-01

    Abstract Beginning from two plausible starting points—an uninhabited or inhabited Mars—this paper discusses the possible trajectories of martian habitability over time. On an uninhabited Mars, the trajectories follow paths determined by the abundance of uninhabitable environments and uninhabited habitats. On an inhabited Mars, the addition of a third environment type, inhabited habitats, results in other trajectories, including ones where the planet remains inhabited today or others where planetary-scale life extinction occurs. By identifying different trajectories of habitability, corresponding hypotheses can be described that allow for the various trajectories to be disentangled and ultimately a determination of which trajectory Mars has taken and the changing relative abundance of its constituent environments. Key Words: Mars—Habitability—Liquid water—Planetary science. Astrobiology 14, 182–203. PMID:24506485

  20. Small carbon chains in circumstellar envelopes

    NASA Astrophysics Data System (ADS)

    Hargreaves, R. J.; Hinkle, K.; Bernath, P. F.

    2014-11-01

    Observations of carbon-rich circumstellar envelopes were made using the Phoenix spectrograph on the Gemini South telescope to determine the abundance of small carbon chain molecules. Vibration-rotation lines of the ?3 antisymmetric stretch of C3 near 2040 cm-1 (4.902 ?m) have been used to determine the column density for four carbon-rich circumstellar envelopes: CRL 865, CRL 1922, CRL 2023 and IRC +10216. We additionally calculate the column density of C5 for IRC +10216, and provide an upper limit for five more objects. An upper limit estimate for the C7 column density is also provided for IRC+10216. A comparison of these column densities suggests a revision to current circumstellar chemical models may be needed.

  1. Habitable Niches In Single and Binary Star Systems

    NASA Astrophysics Data System (ADS)

    Clark, Joni; Mason, P. A.

    2013-01-01

    We investigate habitable niches, defined as locations with optimum conditions for complex life to exist. The recent discovery of planets in several binaries motivates this study to examine favorable habitability circumstances in both single and binary star systems. Stellar evolution calculations are used to model time dependent stellar luminosity, UV flux, photo-synthetic flux and atmospheric water photolysis. Tidal interactions such as synchronization timescales, heat generation, and forcing frequency are also investigated. An Earth-analogue planet in the habitable zone of a 0.8 solar mass star is well suited for complex life. Several high quality niches are available to planets in habitable zones of binaries. For example, orbiting a pair of twin stars each 0.75 solar masses with a binary period of ten days will provide ample photo-synthetic radiation without an overdose of UV radiation, and tidal effects mimicking the Earth-Moon. A solar like star with a close red dwarf companion, like the recently discovered Kepler 47, provides a high quality niche because both stars are relatively long lived and the habitable zone has abundant photo-synthetic light while avoiding harmful UV light. A similar niche exists with a sun like star, which in turn is orbited by a distant red dwarf, providing a roughly annual enhanced red photo-synthetic flux. Also, moons orbiting Jupiter mass planets may exist within habitable zones of both single and binary stars. Such moons might be synchronized to the planet rather than the star. Due to the abundance of binary systems and the presence of high quality niches; binaries may harbor a significant fraction of inhabited planets within the universe. The present study allows for selection of the best habitability follow up targets for large telescopes.

  2. HABITABILITY OF EXOMOONS AT THE HILL OR TIDAL LOCKING RADIUS

    SciTech Connect

    Hinkel, Natalie R.; Kane, Stephen R., E-mail: natalie.hinkel@gmail.com [NASA Exoplanet Science Institute, Caltech, MS 100-22, 770 South Wilson Avenue, Pasadena, CA 91125 (United States)

    2013-09-01

    Moons orbiting extrasolar planets are the next class of object to be observed and characterized for possible habitability. Like the host-planets to their host-star, exomoons have a limiting radius at which they may be gravitationally bound, or the Hill radius. In addition, they also have a distance at which they will become tidally locked and therefore in synchronous rotation with the planet. We have examined the flux phase profile of a simulated, hypothetical moon orbiting at a distant radius around the confirmed exoplanets {mu} Ara b, HD 28185 b, BD +14 4559 b, and HD 73534 b. The irradiated flux on a moon at its furthest, stable distance from the planet achieves its largest flux gradient, which places a limit on the flux ranges expected for subsequent (observed) moons closer in orbit to the planet. We have also analyzed the effect of planetary eccentricity on the flux on the moon, examining planets that traverse the habitable zone either fully or partially during their orbit. Looking solely at the stellar contributions, we find that moons around planets that are totally within the habitable zone experience thermal equilibrium temperatures above the runaway greenhouse limit, requiring a small heat redistribution efficiency. In contrast, exomoons orbiting planets that only spend a fraction of their time within the habitable zone require a heat redistribution efficiency near 100% in order to achieve temperatures suitable for habitability. This means that a planet does not need to spend its entire orbit within the habitable zone in order for the exomoon to be habitable. Because the applied systems comprise giant planets around bright stars, we believe that the transit detection method is most likely to yield an exomoon discovery.

  3. Effects of extreme obliquity variations on the habitability of exoplanets.

    PubMed

    Armstrong, J C; Barnes, R; Domagal-Goldman, S; Breiner, J; Quinn, T R; Meadows, V S

    2014-04-01

    We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large-amplitude, high-frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, increasing the outer edge of the habitable zone. We restricted our exploration to hypothetical systems consisting of a solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We verified that these systems are stable for 10(8) years with N-body simulations and calculated the obliquity variations induced by the orbital evolution of the Earth-mass planet and a torque from the host star. We ran a simplified energy balance model on the terrestrial planet to assess surface temperature and ice coverage on the planet's surface, and we calculated differences in the outer edge of the habitable zone for planets with rapid obliquity variations. For each hypothetical system, we calculated the outer edge of habitability for two conditions: (1) the full evolution of the planetary spin and orbit and (2) the eccentricity and obliquity fixed at their average values. We recovered previous results that higher values of fixed obliquity and eccentricity expand the habitable zone, but we also found that obliquity oscillations further expand habitable orbits in all cases. Terrestrial planets near the outer edge of the habitable zone may be more likely to support life in systems that induce rapid obliquity oscillations as opposed to fixed-spin planets. Such planets may be the easiest to directly characterize with space-borne telescopes. PMID:24611714

  4. Habitable extrasolar planets: from theory to observations

    NASA Astrophysics Data System (ADS)

    Haghighipour, N.

    The discovery of planets around other stars is undoubtedly one of the most significant achievements of modern astronomy. The detection of more than 700 extrasolar planets combined with more than 2300 planetary candidates identified by the Kepler space telescope has proven the fact that our solar system is not unique and many planets, in particular those similar to our Earth, may exist elsewhere in the universe. Although the detection of an Earth-sized planet in the habitable zone of a Sun-like star is still a chal- lenging task, astronomers have been able to identify slightly larger objects known as super-Earths in the habitable zones of M stars. These objects, with their capability in retaining a moderate atmosphere, a possible dynam- ics interior, and a magnetic field, present promising venues for searching for habitable planets. This paper presents a short review of the current state of research on the formation of Earth-sized planets and super-Earths, and their detection around low-mass stars.

  5. Temperature Variations and Habitability

    NSDL National Science Digital Library

    These are the student pages for a two part lesson plan that will teach students about observing, describing, and adapting to temperature variations and relating factors that influence planetary temperature and habitability. The class will decide upon a plan for describing indoor and outdoor environments and compare them with the data on environmental conditions at other Earth locales and planets in our solar system. These will be used to discuss temperature ranges, their relation to habitability, and ways to adapt to these conditions. In the second activity, students will give three examples of how humans modify the environment to improve livability, identify three factors that may determine the average temperature of a planet, identify a minimum of five factors that may determine the habitability of a planet, state the importance of maintaining habitable temperature on a planet, and briefly describe the links between two sets of factors of their choosing. The site provides a list of materials, objectives, and worksheets. Teachers' notes are also included.

  6. What makes a planet habitable?

    NASA Astrophysics Data System (ADS)

    Lammer, H.; Bredehöft, J. H.; Coustenis, A.; Khodachenko, M. L.; Kaltenegger, L.; Grasset, O.; Prieur, D.; Raulin, F.; Ehrenfreund, P.; Yamauchi, M.; Wahlund, J.-E.; Grießmeier, J.-M.; Stangl, G.; Cockell, C. S.; Kulikov, Yu. N.; Grenfell, J. L.; Rauer, H.

    2009-06-01

    This work reviews factors which are important for the evolution of habitable Earth-like planets such as the effects of the host star dependent radiation and particle fluxes on the evolution of atmospheres and initial water inventories. We discuss the geodynamical and geophysical environments which are necessary for planets where plate tectonics remain active over geological time scales and for planets which evolve to one-plate planets. The discoveries of methane-ethane surface lakes on Saturn’s large moon Titan, subsurface water oceans or reservoirs inside the moons of Solar System gas giants such as Europa, Ganymede, Titan and Enceladus and more than 335 exoplanets, indicate that the classical definition of the habitable zone concept neglects more exotic habitats and may fail to be adequate for stars which are different from our Sun. A classification of four habitat types is proposed. Class I habitats represent bodies on which stellar and geophysical conditions allow Earth-analog planets to evolve so that complex multi-cellular life forms may originate. Class II habitats includes bodies on which life may evolve but due to stellar and geophysical conditions that are different from the class I habitats, the planets rather evolve toward Venus- or Mars-type worlds where complex life-forms may not develop. Class III habitats are planetary bodies where subsurface water oceans exist which interact directly with a silicate-rich core, while class IV habitats have liquid water layers between two ice layers, or liquids above ice. Furthermore, we discuss from the present viewpoint how life may have originated on early Earth, the possibilities that life may evolve on such Earth-like bodies and how future space missions may discover manifestations of extraterrestrial life.

  7. Habitable planets with high obliquities.

    PubMed

    Williams, D M; Kasting, J F

    1997-01-01

    Earth's obliquity would vary chaotically from 0 degrees to 85 degrees were it not for the presence of the Moon (J. Laskar, F. Joutel, and P. Robutel, 1993, Nature 361, 615-617). The Moon itself is thought to be an accident of accretion, formed by a glancing blow from a Mars-sized planetesimal. Hence, planets with similar moons and stable obliquities may be extremely rare. This has lead Laskar and colleagues to suggest that the number of Earth-like planets with high obliquities and temperate, life-supporting climates may be small. To test this proposition, we have used an energy-balance climate model to simulate Earth's climate at obliquities up to 90 degrees. We show that Earth's climate would become regionally severe in such circumstances, with large seasonal cycles and accompanying temperature extremes on middle- and high-latitude continents which might be damaging to many forms of life. The response of other, hypothetical, Earth-like planets to large obliquity fluctuations depends on their land-sea distribution and on their position within the habitable zone (HZ) around their star. Planets with several modest-sized continents or equatorial supercontinents are more climatically stable than those with polar supercontinents. Planets farther out in the HZ are less affected by high obliquities because their atmospheres should accumulate CO2 in response to the carbonate-silicate cycle. Dense, CO2-rich atmospheres transport heat very effectively and therefore limit the magnitude of both seasonal cycles and latitudinal temperature gradients. We conclude that a significant fraction of extrasolar Earth-like planets may still be habitable, even if they are subject to large obliquity fluctuations. PMID:11541242

  8. Spectral Fingerprints of Habitability

    NASA Astrophysics Data System (ADS)

    Kaltenegger, L.; Selsis, F.

    2010-01-01

    The emerging field of extrasolar planet search has shown an extraordinary ability to combine research by astrophysics, chemistry, biology and geophysics into a new and exciting interdisciplinary approach to understand our place in the universe. Are there other worlds like ours? How can we characterize those planets and assess if they are habitable? After a decade rich in giant exoplanet detections, observation techniques have now reached the ability to find planets of less than 10 M_Earth (so called Super-Earths) that may potentially be habitable. The detection and characterization of Earth-like planet is approaching rapidly with dedicated space observatories already in operation (Corot) or in development phase (Kepler, James Webb Space Telescope, Extremely Large Telescope (ELT), Darwin/TPF). Space missions like CoRoT (CNES, Rouan et al. 1998) and Kepler (NASA, Borucki et al. 1997) will give us statistics on the number, size, period and orbital distance of planets, extending to terrestrial planets on the lower mass range end as a first step, while missions like Darwin/TPF are designed to characterize their atmospheres. In this chapter we discuss how we can read a planet's spectral fingerprint and characterize if it is potentially habitable. We discuss the first steps to detect a habitable planet and set biomarker detection in context in Section 1. In Section 2 we focus on biomarkers, their signatures at different wavelengths, abiotic sources and cryptic photosynthesis - using Earth as our primary example - the only habitable planet we know of so far. Section 3 concentrates on planets around different stars, and Section 4 summarizes the chapter.

  9. Radiological Habits Survey: Sizewell, 2010

    E-print Network

    Radiological Habits Survey: Sizewell, 2010 2011 Environment Report RL 12/11 Cefas contract report C Radiological Habits Survey: Sizewell, 2010 C.J. Garrod, F.J. Clyne, P. Rumney, J. Elliott, C.A. Smedley and V, J., Smedley, C., and Ly, V.E., 2011. Radiological Habits Survey: Sizewell, 2010. RL 12/11. Cefas

  10. Radiological Habits Survey: Wylfa, 2013

    E-print Network

    Radiological Habits Survey: Wylfa, 2013 2014 Environment Report RL 03/14 Cefas contract report C6028 #12;This page has been intentionally left blank #12;Cefas Document Control Radiological Habits blank #12;Environment Report RL 03/14 Final report Radiological Habits Survey: Wylfa, 2013 C.J. Garrod

  11. Radiological Habits Survey: Wylfa, 2009

    E-print Network

    Radiological Habits Survey: Wylfa, 2009 2010 Environment Report RL 03/10 Cefas contract report C Radiological Habits Survey: Wylfa, 2009 C.J. Garrod, F.J. Clyne, J. Elliott and J.R. Tipple Peer reviewed by G, C. J., Clyne, F. C., Elliott, J., and Tipple, J.R., 2010. Radiological Habits Survey: Wylfa, 2009

  12. Radiological Habits Survey: Dungeness, 2010

    E-print Network

    Radiological Habits Survey: Dungeness, 2010 2011 Environment Report RL 11/11 Cefas contract report Radiological Habits Survey: Dungeness, 2010 F.J. Clyne, C.J. Garrod, V.E. Ly, P. Rumney and J. Elliott Peer: Clyne, F.C., Garrod, C.J., Ly, V.E., Rumney, P., and Elliott, J., 2011. Radiological Habits Survey

  13. Radiological Habits Survey: Derby, 2009

    E-print Network

    Radiological Habits Survey: Derby, 2009 2010 Environment Report RL 05/10 Cefas contract report C Radiological Habits Survey: Derby, 2009 J. Elliott, F.J. Clyne and C.J. Garrod Peer reviewed by G.J. Hunt., Clyne, F.C. and Garrod, C.J., 2010. Radiological Habits Survey: Derby, 2009. RL 05/10. Cefas, Lowestoft

  14. Radiological Habits Survey: Heysham, 2011

    E-print Network

    Radiological Habits Survey: Heysham, 2011 2012 Environment Report RL 02/12 Cefas contract report C Radiological Habits Survey: Heysham, 2011 C.J. Garrod, F.J. Clyne, V.E. Ly and P. Rumney Peer reviewed by G, C.J., Clyne, F.J., Ly, V.E. and Rumney, P., 2012. Radiological Habits Survey: Heysham, 2011. RL 02

  15. Radiological Habits Survey: Devonport, 2011

    E-print Network

    Radiological Habits Survey: Devonport, 2011 2012 Environment Report RL 01/12 Cefas contract report Radiological Habits Survey: Devonport, 2011 F.J. Clyne, C.J. Garrod, V.E. Ly and P. Rumney Peer reviewed by G.J., Garrod, C.J., Ly, V.E. and Rumney, P., 2012. Radiological Habits Survey: Devonport, 2011. RL 01/12. Cefas

  16. Radiological Habits Survey: Amersham, 2009

    E-print Network

    Radiological Habits Survey: Amersham, 2009 2010 Environment Report RL 04/10 Cefas contract report C Radiological Habits Survey: Amersham, 2009 F.J. Clyne, C.J. Garrod and J. Elliott Peer reviewed by G.J. Hunt.C., Garrod, C.J. and Elliott, J., 2010. Radiological Habits Survey: Amersham, 2009. RL 04/10. Cefas

  17. Polytype distribution of circumstellar silicon carbide

    Microsoft Academic Search

    T. L. Daulton; T. J. Bernatowicz; R. S. Lewis; S. Messenger; F. J. Stadermann; S. Amari

    2003-01-01

    Silicon carbide (SiC) is a particularly interesting species of presolar grain because it is known to form on the order of a hundred different polytypes in the laboratory, and the formation of a particular polytype is sensitive to growth conditions. Astronomical evidence for the formation of SiC in expanding circumstellar atmospheres of asymptotic giant branch (AGB) carbon stars is provided

  18. Small Carbon Chains in Circumstellar Envelopes

    NASA Astrophysics Data System (ADS)

    Hargreaves, Robert J.; Hinkle, Kenneth; Bernath, Peter F.

    2014-06-01

    Observations were made of a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the presence of small carbon chain molecules. The circumstellar envelope of IRC+10216 (CRL 1381) has been extensively studied, due to its brightness in the infrared, and C_3 and C_5 have previously been observed. Vibration-rotation lines of the ?b{3} antisymmetric stretch of C_3 near 2040 wn have been used to determine the column density of C_3 in three new circumstellar envelopes: CRL 865, CRL 1922 and CRL 2023. Our new observations support the column density determined from CRL 1381 and also demonstrate that C_3 is common in carbon-rich circumstellar shells. We additionally determine upper limits for the small carbon chains, C_5 and C_7. Hinkle, K.W., Keady, J.J., & Bernath, P.F. 1988, Science, 241, 1319 Bernath, P.F., Hinkle, K.H., & Keady, J.J. 1989, Science, 244, 562

  19. astroph/9810261 Infrared interferometry of circumstellar envelopes

    E-print Network

    Monnier, John D.

    with spectral line observations, high angular resolution studies can directly measure gas densities, velocitiesastro­ph/9810261 17 Oct 1998 Infrared interferometry of circumstellar envelopes John D. Monnier with the new generation of separate­ element, interferometric arrays. 1. Introduction Infrared interferometry

  20. Isothermal Circumstellar Dust Shell Model for Teaching

    ERIC Educational Resources Information Center

    Robinson, G.; Towers, I. N.; Jovanoski, Z.

    2009-01-01

    We introduce a model of radiative transfer in circumstellar dust shells. By assuming that the shell is both isothermal and its thickness is small compared to its radius, the model is simple enough for students to grasp and yet still provides a quantitative description of the relevant physical features. The isothermal model can be used in a…

  1. POST-CAPTURE EVOLUTION OF POTENTIALLY HABITABLE EXOMOONS

    SciTech Connect

    Porter, Simon B.; Grundy, William M., E-mail: porter@lowell.edu [Lowell Observatory, 1400 W. Mars Hill Rd., Flagstaff, AZ 86001 (United States)

    2011-07-20

    The satellites of extrasolar planets (exomoons) have been recently proposed as astrobiological targets. Since giant planets in the habitable zone are thought to have migrated there, it is possible that they may have captured a former terrestrial planet or planetesimal. We therefore attempt to model the dynamical evolution of a terrestrial planet captured into orbit around a giant planet in the habitable zone of a star. We find that approximately half of loose elliptical orbits result in stable circular orbits over timescales of less than a few million years. We also find that those orbits are mostly at low inclination, but have no prograde/retrograde preference. In addition, we calculate the transit timing and duration variations for the resulting systems, and find that potentially habitable Earth-mass exomoons should be detectable.

  2. Delivery of Volatiles to Habitable Planets in Extrasolar Planetary Systems

    NASA Technical Reports Server (NTRS)

    Chambers, John E.; Kress, Monika E.; Bell, K. Robbins; Cash, Michele; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The Earth can support life because: (1) its orbit lies in the Sun's habitable zone', and (2) it contains enough volatile material (e.g. water and organics) for life to flourish. However, it seems likely that the Earth was drier when it formed because it accreted in a part of the Sun's protoplanetary nebula that was too hot for volatiles to condense. If this is correct, water and organics must have been delivered to the habitable zone, after dissipation of the solar nebula, from a 'wet zone' in the asteroid belt or the outer solar system, where the nebula was cool enough for volatiles to condense. Material from the wet zone would have been delivered to the Earth by Jupiter and Saturn. Gravitational perturbations from these giant planets made much of the wet zone unstable, scattering volatile-rich planetesimals and protoplanets across the Solar System. Some of these objects ultimately collided with the inner Planets which themselves lie in a stable part of the Solar System. Giant planets are now being discovered orbiting other sunlike stars. To date, these planets have orbits and masses very different from Jupiter and Saturn, such that few if any of these systems is likely to have terrestrial planets in the star's habitable zone. However, new discoveries are anticipated due to improved detector sensitivity and the increase in the timespan of observations. Here we present numerical experiments examining the range of giant-planet characteristics that: (1) allow stable terrestrial Planets to exist in a star's habitable zone, and (2) make a large part of the star's wet zone weakly unstable, thus delivering volatiles to the terrestrial planets over an extended period of time after the dissipation of the solar nebula.

  3. A Model of Habitability Within the Milky Way Galaxy

    Microsoft Academic Search

    M. G. Gowanlock; D. R. Patton; S. M. McConnell

    2011-01-01

    We present a model of the Galactic Habitable Zone (GHZ), described in terms of the spatial and temporal dimensions of the Galaxy that may favour the development of complex life. The Milky Way galaxy is modelled using a computational approach by populating stars and their planetary systems on an individual basis using Monte-Carlo methods. We begin with well-established properties of

  4. Habitability and Life - an Overview

    NASA Astrophysics Data System (ADS)

    Bredehöft, J. H.

    2008-09-01

    Abstract The search for habitable planets has seen a significant boost, since much effort was invested into development of newer and more powerful techniques of detecting such planetary bodies. This search is fuelled by the interest that is sparked by its help in answering the bigger question of the origin of life on Earth and its abundance in the universe. Traditionally a planetary body has been deemed habitable when it provides conditions under which water is liquid. This led to the formulation of a habitable zone across stars, in which liquid water can exist. [1] Liquid water remains to this day the single most important feature in the search for life. There have been various suggestions of life being present in waterless environments like liquid hydrocarbons or even liquid ammonia, but how exactly a living system under such conditions might work, no one can satisfactorily explain. [2] A very important point in this context that is not often raised is that while water might be a favourable medium in which to live and certainly a major constituent of all living organism we know of, water alone is not alive and it will not spontaneously evolve into life. It would thus seem that apart from the presence of liquid water there a number of other, minor, necessary ingredients to life that determine whether a planet is habitable (meaning capable of sustaining life) or whether it is also capable of providing the starting grounds for the evolution of living systems. These other ingredients are determined by the minimum requirements of life itself. They include the molecular components of the most primitive encasing of an organism, the most primitive molecules needed for something like a metabolism and the most primitive way of storing information. [3] In addition to these molecular components, life must be able to utilise a source of energy to drive chemical reactions. Observations of various extremophiles on Earth utilising all kinds disequilibria suggest that these can be very diverse. The exact nature of these other ingredients, their possible presence and history of formation and their impact for the formation and evolution of life will be discussed for several different types of habitats all across the regime in which liquid water can be found, such as very dry and cold bodies like Mars, hot bodies like Venus, bodies covered completely in water or bodies with subsurface oceans. References [1] Kasting J.F., Whitmire D.P., Reynolds R.T., (1993) Icarus 101(1), 108-128 [2] Benner S.A., Ricardo A., Carrigan M.A. (2004) Curr Opin Chem Biol 8(6), 672-689 [3] Ruiz-Mirazo K., Peretó J., Moreno A., (2004) OLEB 34(3), 323-346 EPSC Abstracts, Vol. 3, EPSC2008-A-00039, 2008 European Planetary Science Congress, Author(s) 2008

  5. Astrophysical radiation environments of habitable worlds

    NASA Astrophysics Data System (ADS)

    Smith, David Samuel

    Numerous astrophysical sources of radiation affect the environment of planets orbiting within the liquid-water habitable zone of main-sequence stars. This dissertation reaches a number of conclusions about the ionizing radiation environment of the habitable zone with respect to X-rays and gamma-rays from stellar flares and background Galactic cosmic rays. Gamma-rays and X-rays incident on terrestrial-like exoplanet atmospheres can be efficiently reprocessed into diffuse UV emission that, depending on the presence of atmospheric UV absorbers, can reach the surface. Extreme solar X-ray flares over the last 4.6 Gyr could have delivered large enough radiation doses to the Martian surface to sterilize any unprotected organisms, depending on the largest energy releases possible. These flares also pose a significant hazard to manned space missions, since a large flare can occur with little or no warning during an extravehicular activity. A flare as large as the largest observed could deliver radiation doses exceeding safety limits to an astronaut protected by only a spacesuit. With respect to particle radiation, the nature of Galactic cosmic-ray modulation by astrospheres means that habitable-zone cosmic-ray fluxes change by much larger magnitudes when passing through low- densities regions of the interstellar medium. In contrast to the popular idea that passages through dense molecular clouds are required to significantly enhance Galactic cosmic-ray fluxes and affect planets' electrical circuits, background mutation rates, and climates, we find that densities of only 0.1-10 cm -3 , the densities of most interstellar clouds, are sufficient to bring fluxes close to the full, interstellar level. Finally, passages through dense molecular clouds are necessary to shrink astrospheres to within the habitable zone, but such events produce even higher interstellar hydrogen and dust accretion rates than have been estimated because of the combination of enhanced charge-exchange rates between stellar-wind ions and interstellar neutrals and the growing importance of the central star's gravity on particle trajectories as the astrosphere shrinks.

  6. The circumstellar envelope of AFGL 4106

    E-print Network

    Jacco Th. van Loon; F. J. Molster; Hans van Winckel; L. B. F. M. Waters

    1999-07-14

    We present new imaging and spectroscopy of the post-red supergiant binary AFGL 4106. Coronographic imaging in H-alpha reveals the shape and extent of the ionized region in the circumstellar envelope (CSE). Echelle spectroscopy with the slit covering almost the entire extent of the CSE is used to derive the physical conditions in the ionized region and the optical depth of the dust contained within the CSE. The dust shell around AFGL 4106 is clumpy and mixed with ionized gas. H-alpha and [N II] emission is brightest from a thin bow-shaped layer just outside of the detached dust shell. On-going mass loss is traced by [Ca II] emission and blue-shifted absorption in lines of low-ionization species. A simple model is used to interpret the spatial distribution of the circumstellar extinction and the dust emission in a consistent way.

  7. Computer codes for evaluation of control room habitability (HABIT)

    SciTech Connect

    Stage, S.A. [Pacific Northwest Lab., Richland, WA (United States)

    1996-06-01

    This report describes the Computer Codes for Evaluation of Control Room Habitability (HABIT). HABIT is a package of computer codes designed to be used for the evaluation of control room habitability in the event of an accidental release of toxic chemicals or radioactive materials. Given information about the design of a nuclear power plant, a scenario for the release of toxic chemicals or radionuclides, and information about the air flows and protection systems of the control room, HABIT can be used to estimate the chemical exposure or radiological dose to control room personnel. HABIT is an integrated package of several programs that previously needed to be run separately and required considerable user intervention. This report discusses the theoretical basis and physical assumptions made by each of the modules in HABIT and gives detailed information about the data entry windows. Sample runs are given for each of the modules. A brief section of programming notes is included. A set of computer disks will accompany this report if the report is ordered from the Energy Science and Technology Software Center. The disks contain the files needed to run HABIT on a personal computer running DOS. Source codes for the various HABIT routines are on the disks. Also included are input and output files for three demonstration runs.

  8. HL Tauri and its circumstellar disk

    Microsoft Academic Search

    M. Cohen

    1983-01-01

    New far infrared observations of HL Tau which support the identification of an edge-on disk surrounding the star are presented. A bolometric luminosity for the star of 7.2 solar luminosities and a ratio of infrared to optical luminosity of 630 are indicated. A circumstellar A(V) of about 7.0 mag is produced, consistent with the silicate optical depth to the star.

  9. Stellar masers, circumstellar envelopes, and supernova remnants

    E-print Network

    Athol J. Kemball

    2007-05-15

    This paper reviews recent advances in the study or circumstellar masers and masers found toward supernova remnants. The review is organized by science focus area, including the astrophysics of extended stellar atmospheres, stellar mass-loss processes and outflows, late-type evolved stellar evolution, stellar maser excitation and chemistry, and the use of stellar masers as independent distance estimators. Masers toward supernova remnants are covered separately. Recent advances and open future questions in this field are explored.

  10. On the probability of habitable planets

    E-print Network

    Forget, Francois

    2012-01-01

    In the past 15 years, astronomers have revealed that a significant fraction of the stars should harbor planets and that it is likely that terrestrial planets are abundant in our galaxy. Among these planets, how many are habitable, i.e. suitable for life and its evolution? These questions have been discussed for years and we are slowly making progress. Liquid water remains the key criterion for habitability. It can exist in the interior of a variety of planetary bodies, but it is usually assumed that liquid water at the surface interacting with rocks and light is necessary for the emergence of a life able to modify its environment and evolve. A first key issue is thus to understand the climatic conditions allowing surface liquid water assuming a suitable atmosphere. This have been studied with global mean 1D models which has defined the "classical habitable zone", the range of orbital distances within which worlds can maintain liquid water on their surfaces (Kasting et al. 1993). A new generation of 3D climate...

  11. HABITABLE PLANETS ECLIPSING BROWN DWARFS: STRATEGIES FOR DETECTION AND CHARACTERIZATION

    SciTech Connect

    Belu, Adrian R.; Selsis, Franck; Raymond, Sean N.; Bolmont, Emeline [Universite de Bordeaux, LAB, UMR 5804, F-33270, Floirac (France); Palle, Enric [Instituto de Astrofisica de Canarias, E-38205 La Laguna (Spain); Street, Rachel [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Sahu, D. K.; Anupama, G. C. [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Von Braun, Kaspar [NASA Exoplanet Science Institute, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States); Figueira, Pedro [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Ribas, Ignasi, E-mail: belu@obs.u-bordeaux1.fr [Institut de Ciencies de l'Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5, parell, 2a pl., E-08193 Bellaterra (Spain)

    2013-05-10

    Given the very close proximity of their habitable zones, brown dwarfs (BDs) represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper, we develop search strategies to find habitable planets transiting BDs depending on their maximum habitable orbital period (P{sub HZ{sub out}}). Habitable planets with P{sub HZ{sub out}} shorter than the useful duration of a night (e.g., 8-10 hr) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous BDs require continuous monitoring for longer duration, e.g., from space or from a longitude-distributed network (one test scheduling achieved three telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known BDs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5{sup +5.6}{sub -1.4}% and 56{sup +31}{sub -13}%, depending on our assumptions. We calculate that BDs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using {approx}1% of a five-year mission's lifetime spread over a contiguous segment only one-fifth to one-tenth of this duration.

  12. Radio spectroscopy of circumstellar molecular masers

    NASA Astrophysics Data System (ADS)

    Rudnitskij, G. M.; Colom, P.; Lekht, E. E.; Pashchenko, M. I.; Samodurov, V. A.; Subaev, I. A. Alexander M. Tolmachev,

    2011-05-01

    Results of observations of circumstellar maser sources in long-period variable stars are reported. We have monitored a sample of Mira-type and semiregular variables in the H_2O (wavelength 1.35 cm) and OH (wavelength 18 cm) radio lines. A comparison with data of optical photometry and spectroscopy have been done. The observations in the H_2O line at 1.35 cm were carried out on the RT-22 radio telescope of the Pushchino Radio Astronomy Observatory in 1980--2011. The sample included sixty late-type variable stars with circumstellar envelopes. For most stars twenty to thirty variability cycles (lasting about a year). There is a correlation of the H_2O line flux density with the light variations: in general, the maser intensity follows the optical variability with a certain phase lag. Figure 1 illustrates variations in the H_2O maser emission versus the optical light curve for the Mira-type star U Her. A model, in which the maser variability is caused by the joint influence of a shock wave propagating in the circumstellar envelope and of the variable radio continuum of the stellar photosphere, is considered. There are indications to a quasiperiodic character of the variations of the integrated H_2O line flux and mean radial velocity of the maser emission at a timescale of 14--15 years. Polarimetry of the OH maser emission has allowed us to draw conclusions about circumstellar magnetic field. Results of observations of circumstellar OH masers in the lines at a wavelength of 18 cm are reported. The observations were carried out on the radio telescope of the Nançay Radio Astronomy Observatory (France). In 2007--2011 seventy late-type stars (including Mira-type and semiregular variables) were observed. For 53 of them the emission in at least one of three OH lines (1612, 1665, or 1667 MHz) was detected. Circular and linear polarization of the maser emission was measured; this yielded all four Stokes parameters. The results obtained for the stars T Lep, R LMi, and R Crt are discussed. The emission of T Lep in the 1665 and 1667 MHz OH lines was observed for the first time. In the OH line profiles of all three stars features probably due to Zeeman splitting were detected. Estimates of the magnetic intensity in the maser sources (0.46--2.32 mG) were obtained.

  13. Radiological Habits Survey, Torness 2001

    E-print Network

    #12;Radiological Habits Survey, Torness 2001 The Centre for Environment, Fisheries and Aquaculture........................................................................................... 7 1.3 Dose limits and constraints

  14. Developing Mathematical Habits of Mind

    ERIC Educational Resources Information Center

    Mark, June; Cuoco, Al; Goldenberg, E. Paul; Sword, Sarah

    2010-01-01

    "Mathematical habits of mind" include reasoning by continuity, looking at extreme cases, performing thought experiments, and using abstraction that mathematicians use in their work. Current recommendations emphasize the critical nature of developing these habits of mind: "Once this kind of thinking is established, students can apply it in the…

  15. Radiological Habits Survey: Sellafield, 2013

    E-print Network

    Radiological Habits Survey: Sellafield, 2013 2014 Environment Report RL 02/14 Cefas contract report C6028 #12;This page has been intentionally left blank #12; Cefas Document Control Radiological #12;This page has been intentionally left blank #12;Environment Report RL 02/14 Radiological Habits

  16. What makes a planet habitable ?

    E-print Network

    Guyon, Olivier

    , but WILL "freeze away" with time When is a planet habitable ? #12;Water... Mars & Venus lost their oceans H2OWhat makes a planet habitable ? #12;#12;How to detect planets ? #12;Radial velocity #12;Transits Planet moves in front of star -> star gets dimmer · Planet size · Planet orbit · Large atmosphere ? #12

  17. Confirming the Newspaper Reading Habit.

    ERIC Educational Resources Information Center

    Stone, Gerald C.; Wetherington, Roger V., Jr.

    1979-01-01

    Data from a study of the newspaper reading habits of 18- to 34-year-olds suggest that reading a daily newspaper is a habitual practice involving certain repetitive actions and that the newspaper habit is dependent on the tradition of newspaper reading in the home when the individual was growing up. (GT)

  18. Infrared heterodyne spectroscopy of circumstellar molecules

    NASA Technical Reports Server (NTRS)

    Betz, A. L.; Mclaren, R. A.

    1980-01-01

    Ammonia has been detected in the circumstellar envelopes of IRC+10216, VY CMa, VX Sgr, and IRC+10420. A number of absorption lines of (N-14)H3 in the nu sub 2 vibration-rotation band around 28 THz (950 per cm) have been observed at a velocity resolution of 0.2 km/s. Typical linewidths are 1 to 4 km/s, and the details of the line profiles provide additional insights on the process of mass loss in these stars.

  19. ROTATIONAL SYNCHRONIZATION MAY ENHANCE HABITABILITY FOR CIRCUMBINARY PLANETS: KEPLER BINARY CASE STUDIES

    SciTech Connect

    Mason, Paul A. [Department of Physics, University of Texas at El Paso, El Paso, TX 79968 (United States); Zuluaga, Jorge I.; Cuartas-Restrepo, Pablo A. [FACom-Instituto de Fisica-FCEN, Universidad de Antioquia, Calle 70 No. 52-21, Medellin (Colombia); Clark, Joni M. [Department of Mathematics and Physical Sciences, New Mexico State University-DACC, Las Cruces, NM 88003 (United States)

    2013-09-10

    We report a mechanism capable of reducing (or increasing) stellar activity in binary stars, thereby potentially enhancing (or destroying) circumbinary habitability. In single stars, stellar aggression toward planetary atmospheres causes mass-loss, which is especially detrimental for late-type stars, because habitable zones are very close and activity is long lasting. In binaries, tidal rotational breaking reduces magnetic activity, thus reducing harmful levels of X-ray and ultraviolet (XUV) radiation and stellar mass-loss that are able to erode planetary atmospheres. We study this mechanism for all confirmed circumbinary (p-type) planets. We find that main sequence twins provide minimal flux variation and in some cases improved environments if the stars rotationally synchronize within the first Gyr. Solar-like twins, like Kepler 34 and Kepler 35, provide low habitable zone XUV fluxes and stellar wind pressures. These wide, moist, habitable zones may potentially support multiple habitable planets. Solar-type stars with lower mass companions, like Kepler 47, allow for protected planets over a wide range of secondary masses and binary periods. Kepler 38 and related binaries are marginal cases. Kepler 64 and analogs have dramatically reduced stellar aggression due to synchronization of the primary, but are limited by the short lifetime. Kepler 16 appears to be inhospitable to planets due to extreme XUV flux. These results have important implications for estimates of the number of stellar systems containing habitable planets in the Galaxy and allow for the selection of binaries suitable for follow-up searches for habitable planets.

  20. Assessing Habitability: Lessons from the Phoenix Mission

    NASA Technical Reports Server (NTRS)

    Stoker, Carol R.

    2013-01-01

    The Phoenix mission's key objective was to search for a habitable zone. The Phoenix lander carried a robotic arm with digging scoop to collect soil and icy material for analysis with an instrument payload that included volatile mineral and organic analysis(3) and soil ionic chemistry analysis (4). Results from Phoenix along with theoretical modeling and other previous mission results were used to evaluate the habitability of the landing site by considering four factors that characterize the environments ability to support life as we know it: the presence of liquid water, the presence of an energy source to support metabolism, the presence of nutrients containing the fundamental building blocks of life, and the absence of environmental conditions that are toxic to or preclude life. Phoenix observational evidence for the presence of liquid water (past or present) includes clean segregated ice, chemical etching of soil grains, calcite minerals in the soil and variable concentrations of soluble salts5. The maximum surface temperature measured was 260K so unfrozen water can form only in adsorbed films or saline brines but warmer climates occur cyclically on geologically short time scales due to variations in orbital parameters. During high obliquity periods, temperatures allowing metabolism extend nearly a meter into the subsurface. Phoenix discovered 1%w/w perchlorate salt in the soil, a chemical energy source utilized by a wide range of microbes. Nutrient sources including C, H, N, O, P and S compounds are supplied by known atmospheric sources or global dust. Environmental conditions are within growth tolerance for terrestrial microbes. Summer daytime temperatures are sufficient for metabolic activity, the pH is 7.8 and is well buffered and the projected water activity of a wet soil will allow growth. In summary, martian permafrost in the north polar region is a viable location for modern life. Stoker et al. presented a formalism for comparing the habitability of various regions visited to date on Mars that involved computing a habitability probability, defined as the product of probabilities for the presence of liquid water (P(sub lw)), energy (P(sub e)), nutrients (P(sub ch)), and a benign environment (P(sub b)). Using this formalism, they argued that the Phoenix site was the most habitable of any site visited to date by landed missions and warranted a follow up mission to search for modern evidence of life. This paper will review that conclusion in view of more recent information from the Mars Exploration Rovers and Mars Science Lander missions.

  1. Imaging and Spectroscopy of Dusty Circumstellar Disks

    NASA Astrophysics Data System (ADS)

    Weinberger, Alycia

    2000-07-01

    Understanding the properties and evolution of dusty disks in the circumstellar environments of young stars is a key element in furthering our concepts of the formation mechanisms of extra-solar planetary systems. In the past year, the advent of NICMOS and STIS coronagraphy has given rise to the first reflected light imaging, other than for Beta Pic, of dusty circumstellar disks with spatially resolved morphological structures. NICMOS has taken a first step in imaging these new disks, elucidating their geometries, morphologies, and bulk photometric properties, while increasing the number of such known systems from one to half a dozen. These dusty disks vary in physical size by over two orders of magnitude and exhibit radial anisotropies in their brightness distributions which may be indicative of dynamical confinement or sculpting of the disk particles by unseen planetary bodies. STIS follow-on imaging and spectroscopy are needed to provide further insight into the nature of the disk particles. With spectra, we will measure the albedo of the disk dust and search for complex molecules and water ice. With coronagraphic images, we will investigate the scattering phase function and hence the composition of the disk dust as well as measure the disk sizes and shapes with high precision. Such observations are of fundamental importance in establishing the physical basis for emergent theories of disk evolution and planet-building.

  2. A 'dry' condensation origin for circumstellar carbonates.

    PubMed

    Toppani, Alice; Robert, François; Libourel, Guy; de Donato, Philippe; Barres, Odile; d'Hendecourt, Louis; Ghanbaja, Jaafar

    2005-10-20

    The signature of carbonate minerals has long been suspected in the mid-infrared spectra of various astrophysical environments such as protostars. Abiogenic carbonates are considered as indicators of aqueous mineral alteration in the presence of CO2-rich liquid water. The recent claimed detection of calcite associated with amorphous silicates in two planetary nebulae and protostars devoid of planetary bodies questions the relevance of this indicator; but in the absence of an alternative mode of formation under circumstellar conditions, this detection remains controversial. The main dust component observed in circumstellar envelopes is amorphous silicates, which are thought to have formed by non-equilibrium condensation. Here we report experiments demonstrating that carbonates can be formed with amorphous silicates during the non-equilibrium condensation of a silicate gas in a H2O-CO2-rich vapour. We propose that the observed astrophysical carbonates have condensed in H2O(g)-CO2(g)-rich, high-temperature and high-density regions such as evolved stellar winds, or those induced by grain sputtering upon shocks in protostellar outflows. PMID:16237436

  3. Circumstellar Disks in the Orion Nebula Cluster

    NASA Astrophysics Data System (ADS)

    Hillenbrand, Lynne A.; Strom, Stephen E.; Calvet, Nuria; Merrill, K. Michael; Gatley, Ian; Makidon, Russell B.; Meyer, Michael R.; Skrutskie, Michael F.

    1998-10-01

    We combine our previous optical spectroscopic and photometric analysis of ~1600 stars located in the Orion Nebula Cluster (ONC) with our own and published near-infrared photometric surveys of the region in order to investigate the evidence for and properties of circumstellar disks. We use the near-infrared continuum excess as our primary disk diagnostic, although we also study sources with Ca ii triplet emission and those designated as ``proplyds.'' The measured near-infrared excess is influenced by (1) the presence or absence of a circumstellar disk, (2) the relative importance of disk accretion and inner disk holes, (3) the relative contrast between photospheric and disk emission, and (4) system inclination. After attempting to understand the effects of these influences, we estimate the frequency of circumstellar disks and discuss the evidence for trends in the disk frequency with stellar mass (over the mass range <0.1-50 M_?), stellar age (over the age range <0.1-2 Myr), and projected cluster radius (over the radial range 0-3 pc). We find that the fraction of stars retaining their inner (<0.1 AU) circumstellar disks to the present time is at least 55% and probably no more than 90%, averaged over the entire range in stellar mass and stellar age represented in the ONC and over the entire area of our survey. We find no trend in the disk fraction with stellar age, at least not over the limited age range of the cluster. We find that more massive stars are less likely to have disks, consistent with a scenario in which the evolutionary timescales are more rapid for disks surrounding more massive stars than for disks surrounding less massive stars. We also find that the disk frequency begins to decrease toward the lowest masses, although objects of all masses (including those that appear to be substellar) can have disks. We find that the disk frequency increases toward the cluster center. We then argue, using several lines of evidence, that a large fraction of the disks associated with stars in the ONC are accretion disks. The observed trends with stellar age, stellar mass, and projected cluster radius in the disk frequency may, in fact, be driven primarily by trends in the disk accretion properties. From the magnitude of the near-infrared excess above that expected from pure irradiation disks, we find an accretion disk fraction among the stars identified as having disks of 61%-88%. In addition, approximately 20% of the stars in our optical spectroscopic sample show broad (several hundred km s^-1 FWHM) Ca ii emission lines, which are features often associated with accretion disk/wind phenomena; another 50% of the sample have Ca ii lines that (at our spectral resolution) are ``filled in,'' indicating an independently derived accretion disk frequency of ~70%. Finally, we discuss the near-infrared and optical emission-line properties of that portion of our sample identified from Hubble Space Telescope imaging as having a dark silhouette or an externally ionized structure. This sample, proposed in the literature to have accretion disks, appears to be no different in terms of its stellar or circumstellar properties from the rest of the ONC population. The only feature distinguishing these objects from their ONC siblings thus may be their current (but short-lived) proximity to the massive stars near the cluster center.

  4. Effects of Extreme Obliquity Variations on the Habitability of Exoplanets

    E-print Network

    Armstrong, J C; Domagal-Goldman, S; Breiner, J; Quinn, T R; Meadows, V S

    2014-01-01

    We explore the impact of obliquity variations on planetary habitability in hypothetical systems with high mutual inclination. We show that large amplitude, high frequency obliquity oscillations on Earth-like exoplanets can suppress the ice-albedo feedback, increasing the outer edge of the habitable zone. We restrict our exploration to hypothetical systems consisting of a solar-mass star, an Earth-mass planet at 1 AU, and 1 or 2 larger planets. We verify that these systems are stable for $10^8$ years with N-body simulations, and calculate the obliquity variations induced by the orbital evolution of the Earth-mass planet and a torque from the host star. We run a simplified energy balance model on the terrestrial planet to assess surface temperature and ice coverage on the planet's surface, and we calculate differences in the outer edge of the habitable zone for planets with rapid obliquity variations. For each hypothetical system, we calculate the outer edge of habitability for two conditions: 1) the full evolu...

  5. Habitability Of Europa's Crust

    NASA Astrophysics Data System (ADS)

    Greenberg, R.; Tufts, B. R.; Geissler, P.; Hoppa, G.

    Physical characterization of Europa's crust shows it to be rich in potentially habitable niches, with several timescales for change that would allow stability for organisms to prosper and still require and drive evolution and adaptation. Studies of tectonics on Europa indicate that tidal stress causes much of the surface cracking, that cracks pen- etrate through to liquid water (so the ice must be thin), and that cracks continue to be worked by tidal stress. Thus a global ocean is (or was until recently) well linked to the surface. Daily tidal flow (period~days) transports substances up and down through the active cracks, mixing surface oxidants and fuels (cometary material) with the oceanic reservoir of endogenic and exogenic substances. Organisms moving with the flow or anchored to the walls could exploit the disequilibrium chemistry, and those within a few meters of the surface could photosynthesize. Cracks remain active for at least ~10,000 yr, but deactivate as nonsynchronous rotation moves them to different stress regimes in less than a million yr. Thus, to survive, organisms squeezed into the ocean must migrate to new cracks, and those frozen in place must hibernate. Most sites remelt and would release captive organisms within about a million yr based on the prevalence of chaotic terrain, which covers nearly half of Europa. Linkage of the ocean to the surface also could help sustain life in the ocean by delivering oxidants and fuels. Suboceanic volcanism (if any) could provide additional sites and support for life, but is not necessary. Recent results support this model. We further constrain the non-synchronous rotation rate, demonstrate the plausibility of episodic melt-through, show that characteristics of pits and uplift features do not imply thick ice, and demonstrate polar wander, i.e. that the ice crust is detached from the solid interior and has slipped as a unit relative to the spin axis. Thus Europa's biosphere (habitable if not inhabited) likely extends from within the ocean up to the surface, with important implications for exploration strategies: Life or its products may be relatively easy to reach, but Europa may be highly susceptible to biological contamination.

  6. Constraints on planetary habitability from interior modelling

    NASA Astrophysics Data System (ADS)

    Noack, Lena; Godolt, Mareike; von Paris, Philip; Plesa, Ana-Catalina; Stracke, Barbara; Breuer, Doris; Rauer, Heike

    2013-04-01

    The most interesting planetary bodies outside the Solar System regarding the search for life are potentially rocky extrasolar planets. Some of them may feature surface conditions that allow for liquid water, which is the elementary prerequisite for life as we know it. The amount of greenhouse gases, like e.g. carbon dioxide (CO2), plays an important role for the determination of the surface temperature, hence the habitability of an extrasolar planet. The amount of greenhouse gases is strongly influenced by their outgassing from the interior. In this study, we investigate under which conditions the planetary interior structure and dynamics allow for the build-up of planetary atmospheres which may lead to habitable surface conditions. We investigate the evolution of a secondary atmosphere for Earth-sized planets with different interior structures (i.e. iron-silicate mixing ratios) by applying a two-dimensional model of interior dynamics [1], which allows for the calculation of the production of partial melt [2]. From this, we estimate the amount of CO2 outgassing for Earth-sized planets with different core and mantle radii after adapting the total CO2 outgassing in 4.5 Gyr for a Venus reference simulation to the present-day atmosphere of Venus. We furthermore investigate the possible influence of plate tectonics on outgassing and the likelihood of plate tectonics depending on the interior structure of the planet. We find that the size of the iron core has a large impact on the production of partial melt, hence on the possible outgassing of CO2, which is due to the pressure-dependence of the melting temperature of silicate rocks: for planets with a large core the planetary mass is larger than for a planet with a small iron core, leading to larger melting temperatures in the upper mantle. Therefore only little outgassing from the interior can be expected. However, for the determination of the outer edge of the habitable zone it is typically assumed that enough greenhouse gas CO2 is available in the atmosphere to lead to liquid water at the surface - independent of the interior of the planet [3]. Our results on the other hand suggest that the outer boundary of the habitable zone may be constrained by the production of partial melt in the interior for planets with a large iron core and a thin silicate mantle. However, if plate tectonics initiates, several tens of bars of CO2 can be outgassed in a short time also for planets with a large iron core. In this case the outer boundary of the habitable zone would not be limited by outgassing as is the case for stagnant-lid planets. It is, however, questionable if planets with a very thin mantle are able to initiate plate tectonics. References [1] Hüttig, C. and Stemmer, K. (2008), PEPI, 171(1-4):137-146. [2] Plesa, A.-C. and Spohn, T. (2012), Transactions of the HLRS 2011, Springer, 551-565. [3] Kasting, J., Whitmire, D.P. and Reynolds, R.T. (1993), Icarus, 101:108-128.

  7. Healthy habits for weight loss

    MedlinePLUS

    ... habits if your shelves are lined with sugary snacks. Rearrange the kitchen to make diet-boosting foods ... you feel hungry, you'll have a healthy snack close at hand. Reduce temptation. If you know ...

  8. Ceres: A Habitable Small Body?

    NASA Astrophysics Data System (ADS)

    Neveu, M.; Desch, S. J.; Castillo-Rogez, J. C.

    2015-01-01

    Ceres seems shaped by abundant volatiles, in a way analogous to that suspected on icy moons. Imminent exploration by Dawn may assess Ceres' potential habitability. To inform future investigations, we will present our latest models of Ceres' interior.

  9. Exozodiacal Dust: Noise Source and Signpost for Habitable Planets

    NASA Astrophysics Data System (ADS)

    Hinz, P.

    2014-03-01

    Exozodiacal light, from debris material in other planetary systems, is both a noise source for future exoplanet imaging missions and a signpost of rocky material in, or near, the habitable zone. The LBT Interferometer has been designed to discover and characterize faint exozodiacal dust around nearby stars. This talk will summarize what we currently know about exozodiacal dust and what we aim to learn with the LBTI's survey, the Hunt for Observable Signatures of Terrestrial Planets (HOSTS).

  10. Twenty Five Habits To Encourage Reading.

    ERIC Educational Resources Information Center

    Shaughnessy, Michael F.

    The development of reading is connected to the development of several habits, habits which once developed, will remain. Some of the habits that will get children reading and instill the habit of reading are: (1) use a book mark; (2) allow kids to read the same book twice; (3) have a dictionary handy and explain its use; (4) have magazines,…

  11. Habitable moons around extrasolar giant planets

    NASA Technical Reports Server (NTRS)

    Williams, D. M.; Kasting, J. F.; Wade, R. A.

    1997-01-01

    Possible planetary objects have now been discovered orbiting nine different main-sequence stars. These companion objects (some of which might actually be brown dwarfs) all have a mass at least half that of Jupiter, and are therefore unlikely to be hospitable to Earth-like life: jovian planets and brown dwarfs support neither a solid nor a liquid surface near which organisms might dwell. Here we argue that rocky moons orbiting these companions could be habitable if the planet-moon system orbits the parent star within the so-called 'habitable zone', where life-supporting liquid water could be present. The companions to the stars 16 Cygni B and 47 Ursae Majoris might satisfy this criterion. Such a moon would, however, need to be large enough (>0.12 Earth masses) to retain a substantial and long-lived atmosphere, and would also need to possess a strong magnetic field in order to prevent its atmosphere from being sputtered away by the constant bombardment of energetic ions from the planet's magnetosphere.

  12. Habitable moons around extrasolar giant planets.

    PubMed

    Williams, D M; Kasting, J F; Wade, R A

    1997-01-16

    Possible planetary objects have now been discovered orbiting nine different main-sequence stars. These companion objects (some of which might actually be brown dwarfs) all have a mass at least half that of Jupiter, and are therefore unlikely to be hospitable to Earth-like life: jovian planets and brown dwarfs support neither a solid nor a liquid surface near which organisms might dwell. Here we argue that rocky moons orbiting these companions could be habitable if the planet-moon system orbits the parent star within the so-called 'habitable zone', where life-supporting liquid water could be present. The companions to the stars 16 Cygni B and 47 Ursae Majoris might satisfy this criterion. Such a moon would, however, need to be large enough (>0.12 Earth masses) to retain a substantial and long-lived atmosphere, and would also need to possess a strong magnetic field in order to prevent its atmosphere from being sputtered away by the constant bombardment of energetic ions from the planet's magnetosphere. PMID:9000072

  13. The Circumstellar Extinction of Planetary Nebulae

    E-print Network

    Robin Ciardullo; George H. Jacoby

    1998-12-09

    We analyze the dependence of circumstellar extinction on core mass for the brightest planetary nebulae (PNe) in the Magellanic Clouds and M31. We show that in all three galaxies, a statistically significant correlation exists between the two quantities, such that high core mass objects have greater extinction. We model this behavior, and show that the relation is a simple consequence of the greater mass loss and faster evolution times of high mass stars. The relation is important because it provides a natural explanation for the invariance of the [O III] 5007 planetary nebula luminosity function (PNLF) with population age: bright Population I PNe are extinguished below the cutoff of the PNLF. It also explains the counter-intuitive observation that intrinsically luminous Population I PNe often appear fainter than PNe from older, low-mass progenitors.

  14. Dust Stratification in Young Circumstellar Disks

    E-print Network

    T. Rettig; S. Brittain; Theodore Simon; E. Gibb; D. S. Balsara; D. A. Tilley; C. Kulesa

    2006-03-01

    We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O as well as broad emission lines of gas phase12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line of sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas to dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling and grain growth to explain the results. The techniques presented here allow us to provide some observationally-motivated bounds on accretion disk alpha in protostellar systems.

  15. Dust Stratification in Young Circumstellar Disks

    E-print Network

    Rettig, T; Simon, T; Gibb, E; Balsara, D S; Tilley, D A; Kulesa, C; Simon, Theodore

    2006-01-01

    We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O as well as broad emission lines of gas phase12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line of sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas to dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling and grain growth to explain the results. The techniques presented here allow us to provide some observationally-motivated bounds on accretion disk alpha in protostellar systems.

  16. HL Tauri and its circumstellar disk

    NASA Technical Reports Server (NTRS)

    Cohen, M.

    1983-01-01

    New far infrared observations of HL Tau which support the identification of an edge-on disk surrounding the star are presented. A bolometric luminosity for the star of 7.2 solar luminosities and a ratio of infrared to optical luminosity of 630 are indicated. A circumstellar A(V) of about 7.0 mag is produced, consistent with the silicate optical depth to the star. Data on HL Tau's effective temperature and radius and its position on the HR diagram suggest that the star has recently completed its accretion phase and is only 100,000 yr old. The column masses of ice and silicates are combined with the disk dimensions to build a simple model of the disk for comparison with the primitive solar nebula. Estimates of the far-infrared emitting mass provide independent probes of the mass in larger grains around HL Tau.

  17. Gemini/Hokupa`a Adaptive Optics Observations of Circumstellar Disks

    NASA Astrophysics Data System (ADS)

    Potter, D.; Baudoz, P.; Brandner, W.; Close, L.; Graves, B.; Guyon, O.; Northcott, M.

    2000-12-01

    We present broad- and narrowband imaging and polarimetric data of young stellar objects with spatially resolved circumstellar disks. The data have been obtained with the University of Hawaii Curvature Sensing Adaptive Optics System Hokupa`a at the Northern Gemini 8m telescope. The objects studied include the edge-on circumstellar disk sources HV Tau C and HK Tau/C, the circumbinary disk source GG Tau, and the massive outflow source MWC 1080. Polarimetric maps combined with model simulations provide insights into the geometrical structure of the circumstellar material. In particular, our observations of HK Tau/C show evidence that the inner region of the disk is largely void of circumstellar material. Estimates of the physical parameters of HV Tau C and GG Tau disks will be presented as well. This research acknowledges support by the National Science Foundation.

  18. CIRCUMSTELLAR SHELL FORMATION IN SYMBIOTIC RECURRENT NOVAE

    SciTech Connect

    Moore, Kevin; Bildsten, Lars [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)

    2012-12-20

    We present models of spherically symmetric recurrent nova shells interacting with circumstellar material (CSM) in a symbiotic system composed of a red giant (RG) expelling a wind and a white dwarf accreting from this material. Recurrent nova eruptions periodically eject material at high velocities ({approx}> 10{sup 3} km s{sup -1}) into the RG wind profile, creating a decelerating shock wave as CSM is swept up. High CSM densities cause the shocked wind and ejecta to have very short cooling times of days to weeks. Thus, the late-time evolution of the shell is determined by momentum conservation instead of energy conservation. We compute and show evolutionary tracks of shell deceleration, as well as post-shock structure. After sweeping up all the RG wind, the shell coasts at a velocity {approx}100 km s{sup -1}, depending on system parameters. These velocities are similar to those measured in blueshifted CSM from the symbiotic nova RS Oph, as well as a few Type Ia supernovae that show evidence of CSM, such as 2006X, 2007le, and PTF 11kx. Supernovae occurring in such systems may not show CSM interaction until the inner nova shell gets hit by the supernova ejecta, days to months after the explosion.

  19. Type Ia supernovae in dense circumstellar gas

    E-print Network

    N. N. Chugai; L. R. Yungelson

    2003-08-18

    We propose a simple model for the bolometric light curve of type Ia supernova exploding in a dense circumstellar (CS) envelope to describe the light curves of supernovae 2002ic and 1997cy. The modeling shows that at the radius $\\sim7\\times10^{15}$ cm the density of CS envelopes around both supernovae is similar. The mass of the CS envelope around SN 1997cy is close to $5 M_{\\odot}$, while the characteristic time of the ejection of this envelope does not exceed 600 yr. We analyze two possible evolutionary scenarios which might lead to the explosion of type Ia supernova inside a dense CS envelope: accretion on CO white dwarf in the symbiotic binary and evolution of a single star with the initial mass of about $8 M_{\\odot}$. If the conjecture about the explosion of type Ia supernova in a dense CS envelope is correct in the case of SN 2002ic and SN 1997cy then the rapid loss of the red supergiant envelope and the subsequent explosion of the CO white dwarf are synchronized by certain mechanism. This mechanism might be related to the contraction of the white dwarf as it approaches the Chandrasekhar limit. We show that formation of a (super)Chandrasekhar mass due to the merger of a CO white dwarf and CO core of a red supergiant with consequent explosion is unlikely, since it does not provide the required synchronization of the rapid mass loss and explosion.

  20. Breastfeeding FAQs: Your Eating and Drinking Habits

    MedlinePLUS

    ... Sports: Keeping Kids Safe Concussions: What to Know Breastfeeding FAQs: Your Eating and Drinking Habits KidsHealth > Parents > Growth & Development > Feeding & Eating > Breastfeeding FAQs: Your Eating and Drinking Habits Print A ...

  1. Habitability potential of icy moons: a comparative study

    NASA Astrophysics Data System (ADS)

    Solomonidou, Anezina; Coustenis, Athena; Encrenaz, Thérèse; Sohl, Frank; Hussmann, Hauke; Bampasidis, Georgios; Wagner, Frank; Raulin, François; Schulze-Makuch, Dirk; Lopes, Rosaly

    2014-05-01

    Looking for habitable conditions in the outer solar system our research focuses on the natural satellites rather than the planets themselves. Indeed, the habitable zone as traditionally defined may be larger than originally con-ceived. The strong gravitational pull caused by the giant planets may produce enough energy to sufficiently heat the interiors of orbiting icy moons. The outer solar system satellites then provide a conceptual basis within which new theories for understanding habitability can be constructed. Measurements from the ground but also by the Voyager, Galileo and the Cassini spacecrafts revealed the potential of these satellites in this context, and our understanding of habitability in the solar system and beyond can be greatly enhanced by investigating several of these bodies together [1]. Their environments seem to satisfy many of the "classical" criteria for habitability (liquid water, energy sources to sustain metabolism and chemical compounds that can be used as nutrients over a period of time long enough to allow the development of life). Indeed, several of the moons show promising conditions for habitability and the de-velopment and/or maintenance of life. Europa, Callisto and Ganymede may be hiding, under their icy crust, putative undersurface liquid water oceans [3] which, in the case of Europa [2], may be in direct contact with a silicate mantle floor and kept warm by tidally generated heat [4]. Titan and Enceladus, Saturn's satellites, were found by the Cassini-Huygens mission to possess active organic chemistries with seasonal variations, unique geological features and possibly internal liquid water oceans. Titan's rigid crust and the probable existence of a subsurface ocean create an analogy with terrestrial-type plate tectonics, at least surficial [5], while Enceladus' plumes find an analogue in gey-sers. As revealed by Cassini the liquid hydrocarbon lakes [6] distributed mainly at polar latitudes on Titan are ideal isolated environments to look for biomarkers. Currently, for Titan and Enceladus, geophysical models try to explain the possible existence of an oceanic layer that decouples the mantle from the icy crust. If the silicate mantles of Eu-ropa and Ganymede and the liquid sources of Titan and Enceladus are geologically active as on Earth, giving rise to the equivalent of hydrothermal systems, the simultaneous presence of water, geodynamic interactions, chemical en-ergy sources and a diversity of key chemical elements may fulfill the basic conditions for habitability. Titan has been suggested to be a possible cryovolcanic world due to the presence of local complex volcanic-like geomorphol-ogy and the indications of surface albedo changes with time [7,8]. Such dynamic activity that would most probably include tidal heating, possible internal convection, and ice tectonics, is believed to be a pre-requisite of a habitable planetary body as it allows the recycling of minerals and potential nutrients and provides localized energy sources. In a recent study by Sohl et al. [2013], we have shown that tidal forces are a constant and significant source of inter-nal deformation on Titan and the interior liquid water ocean can be relatively warm for reasonable amounts of am-monia concentrations, thus completing the set of parameters needed for a truly habitable planetary body. Such habi-tability indications from bodies at distances of 10 AU, are essential discoveries brought to us by space exploration and which have recently revolutionized our perception of habitability in the solar system. In the solar system's neighborhood, such potential habitats can only be investigated with appropriate designed space missions, like JUICE-Laplace (JUpiter ICy moon Explorer) for Ganymede and Europa [9]. JUICE is an ESA mission to Jupiter and its icy moons, recently selected to launch in 2022. References: [1] Coustenis, A., Encrenaz, Th., in "Life Beyond Earth : the search for habitable worlds in the Universe", Cambridge Univ. Press, 2013. [2] Patterson, G.W., et al.: AGU P41F-09, 2011. [3]

  2. Radiological Habits Survey: Trawsfynydd, 2005

    E-print Network

    to a conflict with the Data Protection Act has been black lined) The Centre for Environment, Fisheries areas 16 2.4 Conduct of the survey 17 3. METHODS FOR DATA ANALYSIS 20 3.1 Data recording 20 3.2 Data) survey areas TABLES Table 1 Survey coverage Table 2 Typical food groups used in habits surveys Table 3

  3. Radiological Habits Survey: Sizewell, 2005

    E-print Network

    to a conflict with the Data Protection Act has been black lined) The Centre for Environment, Fisheries.4 Conduct of the survey 17 3. METHODS FOR DATA ANALYSIS 20 3.1 Data recording 20 3.2 Data analysis 22 4 TABLES Table 1 Survey coverage Table 2 Typical food groups used in habits surveys Table 3 Adults

  4. Habitability of extrasolar planets and tidal spin evolution.

    PubMed

    Heller, René; Barnes, Rory; Leconte, Jérémy

    2011-12-01

    Stellar radiation has conservatively been used as the key constraint to planetary habitability. We review here the effects of tides, exerted by the host star on the planet, on the evolution of the planetary spin. Tides initially drive the rotation period and the orientation of the rotation axis into an equilibrium state but do not necessarily lead to synchronous rotation. As tides also circularize the orbit, eventually the rotation period does equal the orbital period and one hemisphere will be permanently irradiated by the star. Furthermore, the rotational axis will become perpendicular to the orbit, i.e. the planetary surface will not experience seasonal variations of the insolation. We illustrate here how tides alter the spins of planets in the traditional habitable zone. As an example, we show that, neglecting perturbations due to other companions, the Super-Earth Gl581d performs two rotations per orbit and that any primordial obliquity has been eroded. PMID:22139513

  5. Radiological Habits Survey: Sellafield Review, 2011

    E-print Network

    Radiological Habits Survey: Sellafield Review, 2011 2012 Environment Report RL 05/12 Cefas contract Radiological Habits Survey: Sellafield Review, 2011 Shellfish consumption and intertidal occupancy review F., 2012. Radiological Habits Survey: Sellafield Review, 2011. RL 05/12. Cefas, Lowestoft A copy can

  6. Radiological Habits Survey: Sellafield Review, 2012

    E-print Network

    Radiological Habits Survey: Sellafield Review, 2012 2013 Environment Report RL 04a/13 Cefas Final report Radiological Habits Survey: Sellafield Review, 2012 Aquatic pathways review G.P. Papworth, C.J., Ly, V.E., and Dewar, A., 2013. Radiological Habits Survey: Sellafield Review, 2012. RL 04a/13

  7. Radiological Habits Survey: Sellafield Review, 2010

    E-print Network

    Radiological Habits Survey: Sellafield Review, 2010 2011 Environment Report RL 13/11 Cefas contract Radiological Habits Survey: Sellafield Review, 2010 Shellfish consumption and intertidal occupancy review F, P., Smedley, C.A., and Ly, V.E., 2011. Radiological Habits Survey: Sellafield Review, 2010. RL 13

  8. Radiological Habits Survey: Sellafield Review, 2009

    E-print Network

    Radiological Habits Survey: Sellafield Review, 2009 2010 Environment Report RL 07/10 #12;This page has been intentionally left blank #12;1 Environment Report RL 07/10 Final report Radiological Habits ).................................15 7. USE OF HABITS DATA FOR DOSE ASSESSMENTS

  9. Research Articles Exomoon Habitability Constrained by Illumination

    E-print Network

    Barnes, Rory

    Research Articles Exomoon Habitability Constrained by Illumination and Tidal Heating Rene´ Heller1 their habitability will emerge. Exomoons are likely to be tidally locked to their planet and hence experience days evolved outside Earth has prompted scientists to consider habitability of the terres- trial planets

  10. Collisional Evolution of a Circumstellar Debris Disk

    NASA Astrophysics Data System (ADS)

    Hahn, Joseph M.

    2010-01-01

    A simple and fast model for a circumstellar debris disk has been developed. These disks are of considerable interest because they may be sites of ongoing planet formation. Collisions among unseen planetesimals are thought to be the source of these small dust grains, which upon their creation are launched into very wide orbits due to stellar radiation pressure (Strubbe and Chiang 2006). Collisions among dust grains also depletes the disk of its dust. However inspecting all pairs of intersecting dust orbits allows one to assess the collision probabilities, which then leads to a rate equation that accounts for dust production by unseen planetesimals minus losses due to collisions. This results in a system of coupled nonlinear differential equations, with one equation for the dust in each size bin, that is easily solved numerically for the dust abundance over time. The model's principal parameters are the dust production rate, and nature of the source planetesimals, namely, whether they reside in a narrow ring or a broad disk. The model is also sensitive to whether the planetesimal disk experiences `inside-out' erosion, with dust production being more rapid in the inner part of the planetesimal disk, versus `outside-in' erosion. The simulated disks' surface brightness are then compared to HST observations of beta Pictoris (acquired by Golimowski et al 2006), as well as the solar analog HD 107146 (by Ardila et al 2004, 2005). Preliminary results indicate that, for both systems, the source planetesimals reside in a broad disk, and that the planetesimal erosion there is `outside-in', with dust production being more vigorous in the outer parts of the planetesimal disk. Lastly, the inferred dust production rates are prodigious, possibly resulting in the loss of tens of earth-masses during the life of the planetesimal disk, due to collisional grinding and blowout by radiation pressure.

  11. First Circumstellar Disk around a Massive Star

    NASA Astrophysics Data System (ADS)

    1998-06-01

    Observations with an infrared-sensitive instrument at the ESO 3.6-m telescope at La Silla have for the first time shown the presence of a disk around a hot and massive star, known as G339.88-1.26 . Until now, disks have only been found around less massive stars. Planets are formed in such disks. The new discovery may thus have important implications for our understanding of the formation of planetary systems around stars. TIMMI observations Observations at mid-infrared wavelengths were carried out in July 1997 by Bringfried Stecklum (Landessternwarte Thüringen, Tautenburg, Germany) and Hans-Ulrich Käufl (ESO), using the TIMMI instrument at the ESO 3.6-m telescope. Additional measurements were carried out in March 1998. TIMMI ( T hermal I nfrared M ulti M ode I nstrument) is a general-purpose camera spectrometer operating at a wavelength of 10 µm. To reach sufficient sensitivity, the camera must be cooled to approx. -260 o C, i.e. a few degrees above the absolute minimum, by use of liquid Helium. Astronomical objects whose temperatures are between -120 o C and 300 o C radiate most of their energy at this wavelength. In addition, dust and haze that are absolutely impenetrable for light visible to the human eye, are often found to be nearly transparent at this wavelength. This is why fire-fighters now use similar equipment to look through smoke. G339.88-1.26: A very special object ESO PR Photo 22a/98 ESO PR Photo 22a/98 [JPEG, 800k] This image is a true-color composite of near-infrared observations of the sky region around the radio source G339.88-1.26 with the ESO/MPI 2.2-m telescope at La Silla. In this image, the visible colors red, green and blue have been used to represent the infrared filters J, H and K (at 1.25, 1.63 and 2.2 µm wavelength, respectively). No object is visible at the position of the radio source, even at these near-infrared wavelengths. A dark band of absorbing dust is clearly visible, exactly at the position of the object (indicated by an arrow). Earlier observations with radio telescopes of the object G339.88-1.26 , deeply embedded in an interstellar nebula, had been interpreted in terms of the possible existence of a circumstellar disk around a high-mass star. It was concluded that the star responsible for heating the surrounding gas must be very hot and also that it must be intrinsically very bright. The star, most likely of spectral type O9, would have a luminosity 10,000 times higher than that of the Sun and a mass of about 20 times that of the Sun. From the measured velocity, the likely distance of this object is about 10,000 light-years. The object is associated with several "spots" of very strong radio emission from methanol molecules (methanol masers). Interestingly, they form a chain in the sky and the measured velocities of the individual spots are indicative for orbital motion in a rotating disk around the central star. The circumstellar disk ESO PR Photo 22/98 ESO PR Photo 22b/98 [JPEG, 640k] The TIMMI 10 µm image of the inclined dust disk around a hot O9 star at the G339.88-1.26 radio source. The diameter of the disk is of the order of 5 arcsec, i.e. at the most probable distance to the object (10,000 lightyears) it is 20,000 times larger than the diameter of the Earth's orbit around the Sun. The new TIMMI observations of G339.88-1.26 showed an elliptical object with strong infrared radiation. The peak of this radiation (as seen in the sky) coincides with the peak of the radio emission. Furthermore, the apparent orientation of the disk is well aligned with that of the methanol maser "spots". There is little doubt that this object is indeed the infrared image of a circumstellar disk, viewed at an angle. As far as known, this is the first direct image of a disk around a very massive star. At a wavelength of 10 µm, however, the central star that is responsible for heating the dust disc, cannot be seen in spite of its rather high luminosity. This is because it radiates mostly in the ultra-violet part of the spectrum. Moreover, the dust disk in which the hot star is

  12. Space Physics of Close-in Exoplanets and its Implications for Planet Habitability

    NASA Astrophysics Data System (ADS)

    Cohen, Ofer

    2015-04-01

    The search for habitable exoplanets is currently focused on planets orbiting M-dwarf stars, due to the close proximity of the habitable zone to the star. However, the traditional habitability definition does not account for the physical space environment near the planets, which can be extreme at close-in orbits, and can lead to erosion of te planetary atmosphere. In order to sustain their atmosphers, M-dwarf planets need to have either an intrinsic magnetic field, or a thick atmosphere. Here we present a set of numerical magnetohydrodynamic simulations of the interaction of an Earth-like magnetized planet and a Venus-like non-magnetized planet with the stellar wind of M-dwarf star. We study space physics aspects of these interactions and their implications for planet habitability

  13. Maintenance of permeable habitable subsurface environments by earthquakes and tidal stresses

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2012-10-01

    Life inhabits the subsurface of the Earth down to depths where temperature precludes it. Similar conditions are likely to exist within the traditional habitable zone for objects between 0.1 Earth mass (Mars) and 10 Earth masses (superearth). Long-term cooling and internal radioactivity maintain surface heat flow on the Earth. These heat sources are comparable and likely to be comparable in general within old rocky planets. Surface heat flow scales with mass divided by surface area and hence with surface gravity. The average absolute habitable subsurface thickness scales inversely with heat flow and gravity. Surface gravity varies by only 0.4 g for Mars to 3.15 g for a superearth. This range is less than the regional variation of heat flow on the Earth. Still ocean-boiling asteroid impacts (if they occur) are more likely to sterilize the thin habitable subsurface of large objects than thick habitable subsurface of small ones. Tectonics self-organizes to maintain subsurface permeability and habitability within both stable and active regions on the Earth. Small earthquakes within stable regions allow sudden mixing of water masses. Large earthquakes at plate boundaries allow surface water to descend to great habitable depths. Seismic shaking near major faults cracks shallow rock forming permeable regolith. Strong tidal strains form a similar porous regolith on small bodies such as Enceladus with weak stellar heating. This regolith may be water-saturated within rocky bodies and thus habitable.

  14. THE SOLAR NEIGHBORHOOD XXIX: THE HABITABLE REAL ESTATE OF OUR NEAREST STELLAR NEIGHBORS

    SciTech Connect

    Cantrell, Justin R.; Henry, Todd J.; White, Russel J., E-mail: cantrell@chara.gsu.edu, E-mail: thenry@chara.gsu.edu, E-mail: white@chara.gsu.edu [Georgia State University, Atlanta, GA 30302-4106 (United States)

    2013-10-01

    We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate—defined as locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broadband photometric energy distributions for stars in the sample. Using these values, the locations of the habitable zones are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zone (EHZ). Systems that have dynamically disruptive companions are considered not habitable. We consider companions to be disruptive if the separation ratio of the companion to the habitable zone is less than 5:1. We use the results of these calculations to derive a simple formula for predicting the location of the EHZ for main sequence stars based on V – K color. We consider EHZ widths as more useful measures of the habitable real estate around stars than areas because multiple planets are not expected to orbit stars at identical stellar distances. This EHZ provides a qualitative guide on where to expect the largest population of planets in the habitable zones of main sequence stars. Because of their large numbers and lower frequency of short-period companions, M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9%, and 16.6%, respectively. Our calculations show that three M dwarfs within 10 pc harbor planets in their EHZs—GJ 581 may have two planets (d with msin i = 6.1 M {sub ?}; g with msin i = 3.1 M {sub ?}), GJ 667 C has one (c with msin i = 4.5 M {sub ?}), and GJ 876 has two (b with msin i = 1.89 M {sub Jup} and c with msin i = 0.56 M {sub Jup}). If Earth-like planets are as common around low-mass stars as recent Kepler results suggest, M stars will harbor more Earth-like planets in habitable zones than any other stellar spectral type.

  15. The Solar Neighborhood XXIX: The Habitable Real Estate of Our Nearest Stellar Neighbors

    NASA Astrophysics Data System (ADS)

    Cantrell, Justin R.; Henry, Todd J.; White, Russel J.

    2013-10-01

    We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate—defined as locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broadband photometric energy distributions for stars in the sample. Using these values, the locations of the habitable zones are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zone (EHZ). Systems that have dynamically disruptive companions are considered not habitable. We consider companions to be disruptive if the separation ratio of the companion to the habitable zone is less than 5:1. We use the results of these calculations to derive a simple formula for predicting the location of the EHZ for main sequence stars based on V - K color. We consider EHZ widths as more useful measures of the habitable real estate around stars than areas because multiple planets are not expected to orbit stars at identical stellar distances. This EHZ provides a qualitative guide on where to expect the largest population of planets in the habitable zones of main sequence stars. Because of their large numbers and lower frequency of short-period companions, M stars provide more EHZ real estate than other spectral types, possessing 36.5% of the habitable real estate en masse. K stars are second with 21.5%, while A, F, and G stars offer 18.5%, 6.9%, and 16.6%, respectively. Our calculations show that three M dwarfs within 10 pc harbor planets in their EHZs—GJ 581 may have two planets (d with msin i = 6.1 M ? g with msin i = 3.1 M ?), GJ 667 C has one (c with msin i = 4.5 M ?), and GJ 876 has two (b with msin i = 1.89 M Jup and c with msin i = 0.56 M Jup). If Earth-like planets are as common around low-mass stars as recent Kepler results suggest, M stars will harbor more Earth-like planets in habitable zones than any other stellar spectral type.

  16. Unveiling the Circumstellar Envelope and Disk: A Subarcsecond Survey of Circumstellar Structures

    NASA Astrophysics Data System (ADS)

    Looney, Leslie W.; Mundy, Lee G.; Welch, W. J.

    2000-01-01

    We present the results of a ?=2.7 mm continuum interferometric survey of 24 young stellar objects in 11 fields. The target objects range from deeply embedded class 0 sources to optical T Tauri sources. This is the first subarcsecond survey of the ?=2.7 mm dust continuum emission from young, embedded stellar systems. These multiarray observations, utilizing the high dynamic u-v range of the BIMA array, fully sample spatial scales ranging from 0.4" to 60", thus allowing the first consistent comparison of dust emission structures in a variety of systems. The images show a diversity of structure and complexity. The optically visible T Tauri stars (DG Tauri, HL Tauri, GG Tauri, and GM Aurigae) have continuum emission dominated by compact (<=1") circumstellar disks. In the cases of HL Tauri and DG Tauri, the disks are resolved. The more embedded near-infrared sources (SVS 13 and L1551 IRS 5) have continuum emission that is extended and compact. The embedded sources (L1448 IRS 3, NGC 1333 IRAS 2, NGC 1333 IRAS 4, VLA 1623, and IRAS 16293-2422) have continuum emission dominated by the extended envelope, typically >=85% of the emission at ?=2.7 mm. In many of the deeply embedded systems, it is difficult to uniquely isolate the disk emission component from the envelope extending inward to AU-sized scales. Simple estimates of the circumstellar mass in the optical/infrared and embedded systems are in the ranges 0.01-0.08 Msolar and 0.04-2.88 Msolar, respectively. All of the target embedded objects are in multiple systems with separations on scales of ~30" or less. Based on the system separation, we place the objects in three categories: separate envelope (separation >=6500 AU), common envelope (separation 150-3000 AU), and common disk (separation <=100 AU). These three groups can be linked with fragmentation events during the star formation process: separate envelopes from prompt initial fragmentation and the separate collapse of a loosely condensed cloud, common envelopes from fragmentation of a moderately centrally condensed spherical system, and common disk from fragmentation of a high angular momentum circumstellar disk.

  17. Photochemistry and molecular ions in carbon-rich circumstellar envelopes

    NASA Technical Reports Server (NTRS)

    Glassgold, A. E.; Mamon, G. A.; Omont, A.; Lucas, R.

    1987-01-01

    An earlier theory of ionization of C-rich circumstellar envelopes based on the photochemical model is extended to include the temperature dependence of ion-molecule reactions with polar molecules, particularly HCN, and line self-shielding of CO dissociating radiation. The results are applied to the abundances of HCO(+) and HNC in C-rich circumstellar envelopes. With standard parameters for IRC + 10216, the model is found to be consistent with the new upper limit to the antenna temperature of the J = 1-0 line of HCO(+) obtained with the IRAM 30-m telescope. The photochemical model provides a natural explanation of the relatively large ratio of HCN to HNC observed for C-rich circumstellar envelopes, and good agreement is obtained for the H(C-13)N/HNC antenna temperature ratio measured for IRC + 10216.

  18. Development of a Habitable Planet

    NSDL National Science Digital Library

    2005-01-01

    In this lesson, students investigate the origin of the elements, the process of planet formation, the evolution of life on Earth, and the conditions necessary for life as we know it. Using multimedia resources and a classroom activity, students identify and sequence the major events that caused Earth to develop into the planet we know, understand where the ingredients for Earth originated, including the conditions necessary for life, and consider the likelihood of other habitable worlds.

  19. Widen the belt of habitability!

    PubMed

    Möhlmann, D

    2012-06-01

    Among the key-parameters to characterize habitability are presence or availability of liquid water, an appropriate temperature range, and the time scale of reference. These criteria for habitability are discussed and described from the point of view of water- and ice-physics, and it is shown that liquid water may exist in the sub-surfaces of planetary bodies like Mars, and possibly of inner asteroids and internally heated ice-moons. Water can remain fluid there also at temperatures far below the "canonical" 0 °C. This behaviour is made possible as a consequence of the freezing point depression due to salty solutes in water or "brines", as they can be expected to exist in nature more frequently than pure liquid water. On the other hand, low temperatures cause a slowing down of chemical processes, as can be described by Arrhenius's relation. The resulting smaller reaction rates probably will have the consequence to complicate the detection of low-temperature life processes, if they exist. Furthermore, the adaptation potential of life is to be mentioned in this context as a yet partially unknown process. Resulting recommendations are given to improve the use of criteria to characterize habitable conditions. PMID:22638839

  20. The origin and evolution of dust in interstellar and circumstellar environments

    NASA Technical Reports Server (NTRS)

    Whittet, Douglas C. B.; Leung, Chun M.

    1993-01-01

    This status report covers the period from the commencement of the research program on 1 Jul. 1992 through 30 Apr. 1993. Progress is reported for research in the following areas: (1) grain formation in circumstellar envelopes; (2) photochemistry in circumstellar envelopes; (3) modeling ice features in circumstellar envelopes; (4) episodic dust formation in circumstellar envelopes; (5) grain evolution in the diffuse interstellar medium; and (6) grain evolution in dense molecular clouds.

  1. New Circumstellar Dust Creation in V838 Monocerotis

    E-print Network

    John P. Wisniewski; Mark Clampin; Karen S. Bjorkman; Richard K. Barry; ;

    2008-09-30

    We report high spatial resolution 11.2 and 18.1 micron imaging of the eruptive variable V838 Monocerotis, obtained with Gemini Observatory's Michelle in 2007 March. The 2007 flux density of the unresolved stellar core is roughly 2 times brighter than that observed in 2004. We interpret these data as evidence that V838 Mon has experienced a new circumstellar dust creation event. We also report a gap of spatially extended thermal emission over radial distances of 1860-93000 AU from the central source, which suggests that no prior significant circumstellar dust production events have occurred within the past 900-1500 years.

  2. Heterodyne spatial interferometry of circumstellar dust shells at a wavelength of 11 microns

    Microsoft Academic Search

    E. C. Sutton

    1979-01-01

    The spatial distribution of the 11 micron thermal emission from circumstellar dust envelopes was studied using an infrared heterodyne interferometer. The spatial distribution of silicate grain emission was measured to probe the temperatures and densities of the circumstellar material and thereby to gain an understanding of the structures of circumstellar envelopes. The interferometer used consists of two separate telescopes, each

  3. S-type and P-type habitability in stellar binary systems: A comprehensive approach. I. Method and applications

    SciTech Connect

    Cuntz, M., E-mail: cuntz@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019-0059 (United States)

    2014-01-01

    A comprehensive approach is provided for the study of both S-type and P-type habitability in stellar binary systems, which in principle can also be expanded to systems of higher order. P-type orbits occur when the planet orbits both binary components, whereas in the case of S-type orbits, the planet orbits only one of the binary components with the second component considered a perturbator. The selected approach encapsulates a variety of different aspects, which include: (1) the consideration of a joint constraint, including orbital stability and a habitable region for a putative system planet through the stellar radiative energy fluxes ({sup r}adiative habitable zone{sup ;} RHZ), needs to be met; (2) the treatment of conservative, general, and extended zones of habitability for the various systems as defined for the solar system and beyond; (3) the provision of a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are presented for the kind of system in which S-type and P-type habitability is realized; (4) applications of the attained theoretical approach to standard (theoretical) main-sequence stars. In principle, five different cases of habitability are identified, which are S-type and P-type habitability provided by the full extent of the RHZs; habitability, where the RHZs are truncated by the additional constraint of planetary orbital stability (referred to as ST- and PT-type, respectively); and cases of no habitability at all. Regarding the treatment of planetary orbital stability, we utilize the formulae of Holman and Wiegert as also used in previous studies. In this work, we focus on binary systems in circular orbits. Future applications will also consider binary systems in elliptical orbits and provide thorough comparisons to other methods and results given in the literature.

  4. Sandcastles in the Wind: Frustrated Accretion in Circumstellar Disks

    E-print Network

    Throop, Henry

    (Throop et al 1998) q Timing between the start of coagulation and the onset of photoevaporation, young circumstellar disks in Orion under processes of: Grain Growth q Grain coagulation with collisional q Turn on UV source after delay time tUV #12;Results of Numerical Models q Outer edges are truncated

  5. The connection between binarity, circumstellar disks, and stellar rotation

    Microsoft Academic Search

    Soren Meibom; Sydney Barnes; Robert D. Mathieu; Joel D. Hartman; Matthew J. Holman

    2008-01-01

    We propose to study the effect on stellar rotation of binary companions within the typical circumstellar disk radius (⪅ 100 AU), but beyond the reach of tidal interactions (⪆ 0.2 AU). A first hint of faster rotation among binary primary stars than among single stars has been detected in the ~150 Myr open cluster M35 (tidally synchronized binaries excluded). This

  6. The connections between binarity, circumstellar disks, and stellar rotation

    Microsoft Academic Search

    Soren Meibom; Sydney Barnes; Robert D. Mathieu; Aaron Geller; Joel D. Hartman; Matthew Holman

    2010-01-01

    We propose to study the effect on stellar rotation of binary companions within the typical circumstellar disk radius (⪅ 100 AU), but beyond the reach of tidal interactions (⪆ 0.2 AU). A first hint of faster rotation among binary primary stars than among single stars has been detected in the ~150 Myr open cluster M35 (tidally synchronized binaries excluded). This

  7. The connections between binarity, circumstellar disks, and stellar rotation

    Microsoft Academic Search

    Soren Meibom; Sydney Barnes; Robert D. Mathieu

    2008-01-01

    We propose to study the effect on stellar rotation of binary companions within the typical circumstellar disk radius (⪅ 100 AU), but beyond the reach of tidal interactions (⪆ 0.2 AU). A first hint of faster rotation among binary primary stars than among single stars has been detected in the ~150 Myr open cluster M35 (tidally synchronized binaries excluded). This

  8. Hydrocarbon Anions in Interstellar Clouds and Circumstellar Envelopes

    Microsoft Academic Search

    T. J. Millar; C. Walsh; M. A. Cordiner; R. Ní Chuimín; Eric Herbst

    2007-01-01

    The recent detection of the hydrocarbon anion C6H- in the interstellar medium has led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion\\/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed

  9. Circumstellar Masers in the Galactic center Lor ant Sjouwerman

    E-print Network

    Sjouwerman, Loránt

    Circumstellar Masers in the Galactic center Lor#19;ant Sjouwerman National Radio Astronomy surveys for maser emission (OH, H2O, and SiO) in the central degree (#20; 150 pc) of the Galactic center will be discussed, with the emphasis on masers in OH/IR stars. Using the masers, some recent clues about

  10. On the Classification of Infrared Spectra from Circumstellar Dust Shells

    NASA Technical Reports Server (NTRS)

    Sloan, G. C.; Little-Marenin, I. R.; Price, S. D.

    1996-01-01

    We present results from an ongoing effort to classify the infrared spectra produced by circumstellar dust shells. Earlier efforts concentrated on oxygen-rich dust shells from sources associated with the asymptotic giant branch (AGB). Here, we describe the expansion of our classification to include S stars, supergiants, and carbon stars.

  11. Radiological Habits Survey: Hinkley Point, 2010

    E-print Network

    Radiological Habits Survey: Hinkley Point, 2010 2011 Environment Report RL 01/11 Cefas contract Radiological Habits Survey: Hinkley Point, 2010 F.J. Clyne, C.J. Garrod, P. Rumney, L.M. Hughes and V.E. Ly be cited as: Clyne, F.C., Garrod, C.J., Rumney, P., Hughes, L.M., and Ly, V.E., 2011. Radiological Habits

  12. 7 habits of highly effective.

    PubMed

    McGuinness, Teena M; McElroy, Ellen

    2010-01-01

    There is a pressing need for psychiatric nurse authors to write about their professional image as well as issues they face in clinical practice. In this article, two psychiatric nurses describe how using Covey's The 7 Habits of Highly Effective People: Powerful Lessons in Personal Change can serve as a framework for increasing writing productivity. In addition, the Myers-Briggs Type Indicator can increase awareness of and appreciation for the strengths and differences in each author's writing style. Using these tools, writing can become a process of discovery. PMID:20102131

  13. Space station group activities habitability module study

    NASA Technical Reports Server (NTRS)

    Nixon, David

    1986-01-01

    This study explores and analyzes architectural design approaches for the interior of the Space Station Habitability Module (originally defined as Habitability Module 1 in Space Station Reference Configuration Decription, JSC-19989, August 1984). In the Research Phase, architectural program and habitability design guidelines are specified. In the Schematic Design Phase, a range of alternative concepts is described and illustrated with drawings, scale-model photographs and design analysis evaluations. Recommendations are presented on the internal architectural, configuration of the Space Station Habitability Module for such functions as the wardroom, galley, exercise facility, library and station control work station. The models show full design configurations for on-orbit performance.

  14. The set of habitable planets and astrobiological regulation mechanisms

    NASA Astrophysics Data System (ADS)

    Vukoti?, Branislav

    2010-04-01

    The number of habitable planets in the Milky Way and its temporal variation are major unknowns in the nascent fields of astrobiology and Search for ExtraTerrestrial Intelligence studies. All numerical models developed thus far have suffered from large uncertainties in the input data, in addition to our lack of understanding of the processes of astrobiological dynamics. Here, we argue that at least the input data can now be specified with more confidence, and use a simple Monte Carlo model of the Galactic Habitable Zone (GHZ) as a flexible platform for their elucidation. Previous papers have described some of the major results of this class of models; in this paper we present its mechanics and input parameters, notably the number of the habitable planets in the GHZ and their temporal distribution, based on the results of Lineweaver et al. (Lineweaver, C.H., Fenner, Y. & Gibson, B.K. (2004). Science 303, 59-62.) Regulation mechanisms (such as gamma-ray bursts or supernovae) and their temporal evolution, assumed to be main agents responsible for large-scale correlation effects, are modelled as type ? (which can sterilize part of or the entire GHZ) and type ? (which are of local importance) events with decreasing mean temporal frequency over the cosmological timescale. The considered global risk function implies as an upper limit that about one out of a hundred habitable sites will achieve high astrobiological complexity. The preliminary results of numerical modelling presented here and elsewhere imply that the lack of a sudden change from an essentially dead Galaxy to a Galaxy filled with complex life - the astrobiological phase transition - in our past (a version of Fermi's paradox) may be understood as a consequence of global astrobiological disequilibrium, strongly indicating such a transitional epoch in our future.

  15. Orbital Dynamics and Habitability I: Triggering a Runaway Greenhouse via Tidal Heating

    NASA Astrophysics Data System (ADS)

    Barnes, Rory; Mullins, K.; Goldblatt, C.; Meadows, V. S.; Kasting, J. F.; Heller, R.

    2012-05-01

    The inner edge of the habitable zone is often defined by the tightest orbit which does not initiate a moist or runaway greenhouse. Previously it was believed that only stellar radiation could trigger these phenomena for a long enough duration to desiccate a planet and preclude habitability. We show that for some planets orbiting low-mass stars (<0.3 solar masses), tidal heating can reach levels that induce a runaway greenhouse. We call these planets "Tidal Venuses." As tides circularize the orbit and drive the obliquity to 0 or PI, the heating level drops, but tidal heating can persist long enough to remove all of a planet's water. Therefore, a planet may be discovered in the habitable zone with very low eccentricity (and hence without enough tidal heat to drive a runaway greenhouse), and yet be uninhabitable due to a previous epoch of extreme tidal heating. The range of possible tidal and radiative heating predicts a diversity of planets in and around the habitable zone of low-mass stars. In multi-planet systems, interactions with other companions may maintain non-zero eccentricities and obliquities, increasing the threat of catastrophic tidal heating. As terrestrial planets are discovered around low luminosity primaries, careful consideration of current and past tidal heating will be essential for estimating their likelihoods to be inhabited.

  16. Characteristics of Oral-Digital Habits

    Microsoft Academic Search

    Patrick C. Friman; Michelle R. Byrd; Erin M. Oksol

    This chapter will discuss the two predominant forms of oral-digital habits, thumb\\/finger sucking (finger sucking hereafter) and onychophagia (nail biting hereafter) in terms of their demographics, phenomenology, causes, functions, and clinical associations. The two habits are obviously similar topographically. The extent to which this similarity extends to these other topics will be explored, but only briefly. The differential size and

  17. Habit: Subtle Technology Barrier and Tool.

    ERIC Educational Resources Information Center

    Boettcher, Judith

    2000-01-01

    Discusses the use of information technology, technology diffusion and reinvention, and technology adoption and implementation. Considers the change process in higher education and the need to develop good computer habits and overcome old habits that are based on old teaching and learning methods. (LRW)

  18. Influence of Living Habits on Roommate Compatibility.

    ERIC Educational Resources Information Center

    Beil, Cheryl; Green, Susan K.

    1986-01-01

    Analyzed students' (N=282) responses to questions about personal habits and roommate and residence hall preferences, to explore the influence of habit variables on roommate compatibility. Found that matching roommates on potential causes of conflict had some effect on interaction and compatibility. (ABB)

  19. Genetic Influences on Adolescent Eating Habits

    ERIC Educational Resources Information Center

    Beaver, Kevin M.; Flores, Tori; Boutwell, Brian B.; Gibson, Chris L.

    2012-01-01

    Behavioral genetic research shows that variation in eating habits and food consumption is due to genetic and environmental factors. The current study extends this line of research by examining the genetic contribution to adolescent eating habits. Analysis of sibling pairs drawn from the National Longitudinal Study of Adolescent Health (Add Health)…

  20. Diver's Lung Function: Influence of Smoking Habit

    Microsoft Academic Search

    Shinya SUZUKI

    1997-01-01

    Diver's Lung Function: Influence of Smoking Habit: Shinya SUZUKI. Japan Maritime Self- Defense Force Undersea Medical Center—To assess the influence of smoking habit on divers' lung function, we measured static lung volumes, dynamic lung volumes and flows and diffusing capacity for carbon monoxide (DLco) on 71 healthy, male, JMSDF active-duty uniformed divers (46 smokers and 25 nonsmokers). All measurements were

  1. SETI and SEH (Statistical Equation for Habitables)

    Microsoft Academic Search

    Claudio Maccone

    2011-01-01

    The statistics of habitable planets may be based on a set of ten (and possibly more) astrobiological requirements first pointed out by Stephen H. Dole in his book “Habitable planets for man” (1964). In this paper, we first provide the statistical generalization of the original and by now too simplistic Dole equation. In other words, a product of ten positive

  2. The Online Reading Habits of Malaysian Students

    ERIC Educational Resources Information Center

    Abidin, Mohammad Jafre Bin Zainol; Pourmohammadi, Majid; Varasingam, Nalini A/P; Lean, Ooi Choon

    2014-01-01

    The purpose of this study is to ascertain the differences in online reading habits between genders and investigate the relationship between socio-economic status and online reading habits. Using a questionnaire, a quantitative approach was administered to 240 Form-Four students from four secondary schools in Penang Island, Malaysia. Findings…

  3. Experiences of habit formation: a qualitative study.

    PubMed

    Lally, Phillippa; Wardle, Jane; Gardner, Benjamin

    2011-08-01

    Habit formation is an important goal for behaviour change interventions because habitual behaviours are elicited automatically and are therefore likely to be maintained. This study documented experiences of habit development in 10 participants enrolled on a weight loss intervention explicitly based on habit-formation principles. Thematic analysis revealed three themes: Strategies used to support initial engagement in a novel behaviour; development of behavioural automaticity; and selecting effective cues to support repeated behaviour. Results showed that behaviour change was initially experienced as cognitively effortful but as automaticity increased, enactment became easier. Habits were typically formed in work-based contexts. Weekends and vacations temporarily disrupted performance due to absence of associated cues, but habits were reinstated on return to work. Implications for theory and practice are discussed. PMID:21749245

  4. Cluster headache and lifestyle habits.

    PubMed

    Schürks, Markus; Diener, Hans-Christoph

    2008-04-01

    Cluster headache (CH) has traditionally been associated with certain anthropometric features, personality traits, and lifestyle features. This article focuses on lifestyle features in patients with CH. Especially excessive smoking and alcohol consumption have been ascribed to patients with CH. Despite country-specific habits and a time trend, smoking is much more prevalent among CH patients compared with the general population. Although excessive alcohol consumption was reported in early studies, this was not corroborated more recently. On the contrary, patients with CH seem to avoid alcohol, particularly during active phases, likely due to its ability to trigger attacks. Present studies are purely descriptive. Thus, the associations sketched give no information about the long-term effects of smoking or alcohol consumption on the course of CH. PMID:18474191

  5. The Circumstellar Environments of Young Stars at AU Scales

    E-print Network

    Rafael Millan-Gabet; Fabien Malbet; Rachel Akeson; Christoph Leinert; John Monnier; Rens Waters

    2006-03-21

    We review recent advances in our understanding of the innermost regions of the circumstellar environment around young stars, made possible by the technique of long baseline interferometry at infrared wavelengths. Near-infrared observations directly probe the location of the hottest dust. The characteristic sizes found are much larger than previously thought, and strongly correlate with the luminosity of the central young stars. This relation has motivated in part a new class of models of the inner disk structure. The first mid-infrared observations have probed disk emission over a larger range of scales, and spectrally resolved interferometry has for the first time revealed mineralogy gradients in the disk. These new measurements provide crucial information on the structure and physical properties of young circumstellar disks, as initial conditions for planet formation.

  6. Circumstellar and Circumbinary Disk Evolution in a Binary System

    NASA Astrophysics Data System (ADS)

    Marzari, Francesco; Nelson, A. F.

    2010-10-01

    We simulate the evolution of the circumstellar and circumbinary disks in a system configured to appear similar to that observed for the GG Tau A binary. We find that mass transfer onto the circumstellar disks is episodic with maximal transfer rates which change from orbit to orbit, but which occur following each apoapse passage. Accretion rates onto the stars themselves does not display such periodicities, so the disk masses vary somewhat over the binary orbit. Averaged over time, mass transfer into and out of the disks equilibrates at a disk mass of somewhat less than one Jupiter mass, for both the primary and secondary. The transfer rate of material through the disks is rapid enough to effectively replace the entire disk in less than 10000 yr. We discuss the implications of our results on planet formation in this and similar systems. This is Los Alamos Publication LA-UR 10-04813

  7. CIRCUMSTELLAR SHELLS IN ABSORPTION IN TYPE Ia SUPERNOVAE

    SciTech Connect

    Borkowski, Kazimierz J.; Blondin, John M.; Reynolds, Stephen P. [Physics Department, North Carolina State U., Raleigh, NC 27695-8202 (United States)], E-mail: kborkow@ncsu.edu

    2009-07-10

    Progenitors of Type Ia supernovae (SNe) have been predicted to modify their ambient circumstellar (CSM) and interstellar environments through the action of their powerful winds. While there is X-ray and optical evidence for circumstellar interaction in several remnants of Type Ia SNe, widespread evidence for such interaction in Type Ia SNe themselves has been lacking. We consider prospects for the detection of CSM shells that have been predicted to be common around Type Ia SNe. Such shells are most easily detected in Na I absorption lines. Variable (declining) absorption is expected to occur soon after the explosion, primarily during the SN rise time, for shells located within {approx}1-10 pc of a SN. The distance of the shell from the SN can be determined by measuring the timescale for line variability.

  8. Revising Circumstellar Disk Evolution -- How Binaries Change the Picture

    NASA Astrophysics Data System (ADS)

    Daemgen, Sebastian; Petr-Gotzens, Monika; Meyer, Elliot

    2015-01-01

    We combine new and previously published high-angular resolution near-infrared spectroscopic and photometric observations to measure the presence of accretion and hot circumstellar dust around the individual components of visual multiple stars and confirmed singles with separations between ˜20 and 800 AU in the Orion Nebula Cluster, Chamaeleon I, and Taurus star-forming regions. The data provide evidence for an accelerated disk dispersal in binaries -- in particular of the less massive stellar component -- at a mass accretion rate identical to that of single stars. Our findings have stringent implications on circumstellar disk parameters, which have been traditionally inferred from observations of ``binary-contaminated'' samples. For example, we find an increased single star accretor fraction, i.e., evidence for a longer single star disk lifetime, compared to previous surveys.

  9. Evolution of the Inner Circumstellar Envelope of V838 Monocerotis

    E-print Network

    John P. Wisniewski; Karen S. Bjorkman; Antonio M. Magalhaes

    2003-10-08

    We present imaging polarimetry observations of the eruptive variable V838 Monocerotis and its neighboring field obtained in 2002 October. The polarization of field stars confirms the previously determined interstellar polarization along the line of sight to V838 Mon. While V838 Mon showed intrinsic polarization shortly after its second outburst on 2002 February 8, all subsequent observations only showed a quiescent interstellar polarization component. We find V838 Mon once again showed significant intrinsic polarization in 2002 October, suggesting the presence of an asymmetrical geometry of scattering material close to the star. Furthermore, an observed 90 degree position angle flip in the intrinsic polarization from 2002 February to 2002 October suggests that the distribution of nearby circumstellar material has experienced significant changes. We discuss the opacity changes in the evolving circumstellar cloud around V838 Mon that may explain these observations.

  10. Dust mineralogy in the circumstellar envelope of SVS13

    NASA Astrophysics Data System (ADS)

    Fujiyoshi, T.; Wright, C.; Moore, T.

    It is of great interest to study the mineralogy of circumstellar dust around young stars as it represents the original constituents of planetesimals, hence of the rocky planets like our own Earth. To this end, we have obtained an N-band (8-13 µm) spectrum of a pre-main-sequence star SVS13, using the facility mid-infrared imaging spectrometer COMICS on the Japanese 8.2-m Subaru Telescope atop the summit of Mauna Kea, Hawaii. We have fitted various emissivities/absorption coefficients of dust species to the spectrum to examine dust mineralogy in the circumstellar envelope of this remarkable young star. In this presentation, we outline the modelling and highlight some of our findings.

  11. New Circumstellar Dust Creation in V838 Monocerotis

    Microsoft Academic Search

    John P. Wisniewski; Mark Clampin; Karen S. Bjorkman; Richard K. Barry

    2009-01-01

    We report high spatial resolution 11.2 mum and 18.1 mum imaging of the eruptive variable V838 Monocerotis, obtained with Gemini Observatory's Michelle in 2007 March. The 2007 flux density of the unresolved stellar core is roughly 2 times brighter than that observed in 2004. We interpret these data as evidence that V838 Mon has experienced a new circumstellar dust creation

  12. Circumstellar Disk of HL Tau Revealed by CARMA

    Microsoft Academic Search

    Woojin Kwon; Leslie W. Looney; Lee G. Mundy

    2011-01-01

    The physical properties of circumstellar disks around T Tauri stars - the so-called proto-planetary disks as the natal place of planets - are mainly studied by millimeter\\/submillimeter wavelength continuum, which is sensitive to dust thermal emission. We present high angular resolution (0.13 arc-second) imaging results of the T Tauri star HL Tau in 1.3 and 2.7 mm continua using the

  13. Molecular anion chemistry in interstellar and circumstellar environments

    Microsoft Academic Search

    M. A. Cordiner; T. J. Millar; E. Herbst; R. Ni Chuimin; C. Walsh

    2007-01-01

    The recent detection of C4H-, C6H- and C8H- in TMC-1 and IRC+10216 led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion\\/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed modeling

  14. Hydrocarbon anions in interstellar clouds and circumstellar envelopes

    Microsoft Academic Search

    T. J. Millar; C. Walsh; M. A. Cordiner; R. Ní Chuimín; Eric Herbst

    2007-01-01

    The recent detection of the hydrocarbon anion C6H- in the interstellar medium\\u000ahas led us to investigate the synthesis of hydrocarbon anions in a variety of\\u000ainterstellar and circumstellar environments. We find that the anion\\/neutral\\u000aabundance ratio can be quite large, on the order of at least a few percent,\\u000aonce the neutral has more than five carbon atoms. Detailed

  15. Observations of Circumstellar Thermochemical Equilibrium: The Case of Phosphorus

    NASA Technical Reports Server (NTRS)

    Milam, Stefanie N.; Charnley, Steven B.

    2011-01-01

    We will present observations of phosphorus-bearing species in circumstellar envelopes, including carbon- and oxygen-rich shells 1. New models of thermochemical equilibrium chemistry have been developed to interpret, and constrained by these data. These calculations will also be presented and compared to the numerous P-bearing species already observed in evolved stars. Predictions for other viable species will be made for observations with Herschel and ALMA.

  16. Microwave Emission from Spinning Dust in Circumstellar Disks

    Microsoft Academic Search

    Roman R. Rafikov

    2006-01-01

    In the high-density environments of circumstellar disks dust grains are expected to grow to large sizes by coagulation. Somewhat unexpectedly, recent near-IR observations of PAH features from disks around Herbig Ae\\/Be stars demonstrate that a substantial amount of dust mass in the surface layers of these disks (up to several tens of percent of the local carbon content) can be

  17. Additional constraints on circumstellar disks in the Trapezium Cluster

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.; Prosser, Charles F.; Hartmann, Lee; Mccaughrean, Mark J.

    1994-01-01

    We discuss new constraints on the population of compact ionized sources in the Trapezium Cluster thought to arise from the ionization by the central OB stars of circumstellar disks around low-mass pre-main sequence stars. We present new HST Planetary Camera observations of two of these candidate disk sources, resolving extended nebulosity around them. One source shows a small-scale (greater than 100 AU) bow-shock structure, previously seen on larger scales by O'Dell et al. We show that the circumstellar disk model is the most likely one for the majority of sources, although it remains plausible that some of the larger objects could be equilibrium globules. We combine the most complete censuses of compact radio sources and stars in the core region to derive the fraction of the stellar population that may be associated with a circumstellar disk. Our estimate of 25-75 percent is comparable to that found for PMS stars in the Taurus-Auriga dark clouds, indicating that the dense cluster environment of the Trapezium has not drastically reduced the frequency of disks seen around pre-main sequence stars.

  18. Circumstellar Environments of Southern M Dwarfs in the Solar Neighborhood

    NASA Astrophysics Data System (ADS)

    Silverstein, Michele L.; Henry, Todd J.; Jao, Wei-Chun; Winters, Jennifer G.; Recons Team

    2015-01-01

    We present the first results from SIRENS, the Search for InfraRed Excesses around Nearby Stars. Our goal is to characterize the circumstellar environments of the most common and closest stars in the Universe, the ubiquitous red dwarfs. In this phase of the study, we search 1404 southern M dwarfs within 25 parsecs of the Sun, as reported in Winters et. al 2014, using (Johnson-Kron-Cousins) optical, (2MASS) near-infrared, and (WISE) mid-infrared photometry for circumstellar disks and low-mass companions. Several studies have recently used WISE photometry to detect circumstellar disks and companions --- searches around members of the nearby young moving groups, objects with parallaxes from Hipparcos, and many northern M stars in the SDSS. However, no work has yet been done that focuses on the nearest red dwarfs, which account for at least 75% of all stars. This study, a volume-limited search around M dwarfs in the southern sky, includes statistical conclusions applicable to a majority of the stars in the universe, and opens potential gateways to a better understanding of star and planet formation.

  19. Circumstellar dust shells of hot post-AGB stars

    E-print Network

    G. Sarkar Nee Gauba; M. Parthasarathy

    2004-02-02

    Using a radiative transfer code (DUSTY) parameters of the circumstellar dust shells of 15 hot post-AGB stars have been derived. Combining the optical, near and far-infrared (ISO, IRAS) data of the stars, we have reconstructed their spectral energy distributions (SEDs) and estimated the dust temperatures, mass loss rates, angular radii of the inner boundary of the dust envelopes and the distances to these stars. The mass loss rates (10$^{-6}-10^{-5}$M$_{\\odot}$yr$^{-1}$) are intermediate between stars at the tip of the AGB and the PN phase. We have also studied the ISO spectra of 7 of these stars. Amorphous and crystalline silicate features were observed in IRAS14331-6435 (Hen3-1013), IRAS18062+2410 (SAO85766) and IRAS22023+5249 (LSIII +5224) indicating oxygen-rich circumstellar dust shells. The presence of unidentified infrared (UIR) band at 7.7$\\mu$, SiC emission at 11.5$\\mu$ and the "26$\\mu$" and "main 30$\\mu$" features in the ISO spectrum of IRAS17311-4924 (Hen3-1428) suggest that the central star may be carbon-rich. The ISO spectrum of IRAS17423-1755 (Hen3-1475) shows a broad absorption feature at 3.1$\\mu$ due to C$_{2}$H$_{2}$ and/or HCN which is usually detected in the circumstellar shells of carbon-rich stars.

  20. Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary

    PubMed Central

    Heller, René

    2013-01-01

    Abstract White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10?6. Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 104 K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable. Key Words: Extrasolar terrestrial planets—Habitability—Habitable zone—Tides—Exoplanets. Astrobiology 13, 279–291. PMID:23537137

  1. Morphology of Circumstellar Environment and Some Characterictics of Circumstellar Shells of Stars with the R Coronae Borealis Variability

    E-print Network

    Alexander E. Rosenbush

    2001-04-20

    The well-known light minima of stars with the R Coronae Borealis variability are caused by the formation of an additional circumstellar dust shell, the screening shell, inside the permanent shell. Under the assumption of uniform distribution of matter in the circumstellar environment we estimated the optical thickness of the permanent gas-and-dust shell at 0.2-0.7, and its geometrical thickness is no less than 0.4 of its own radius. The wavelength dependence of extinction is close to neutral. From spectral observations of R CrB itself in the 1985 minimum we traced the transformation of the stellar linear and molecular absorption spectrum to the emission spectrum and established that the fast variation of the U-B colour index by -0.6 in the light decline was caused purely by a change of the spectrum type. The spectrum transformation causes an increase of star brightness in the U, B, and V bands by about 1.4, 0.75, and 0.75 mags, correspondingly. It is suggested that a high-velocity (>200 km/s) matter stream through the circumstellar environment is the cause of the excitation of the emissions observed during light minima when the photospheric flux is weakening.

  2. Habitability design elements for a space station

    NASA Technical Reports Server (NTRS)

    Dalton, M. C.

    1983-01-01

    Habitability in space refers to the components, characteristics, conditions, and design parameters that go beyond but include the basic life sustaining requirements. Elements of habitability covered include internal environment, architecture, mobility and restraint, food, clothing, personal hygiene, housekeeping, communications, and crew activities. All elements are interrelated and need to be treated as an overall discipline. Designing for a space station is similar to designing on earth but with 'space rules' instead of ground rules. It is concluded that some habitability problems require behavioral science solutions.

  3. Diapering habits: a global perspective.

    PubMed

    Thaman, Lauren A; Eichenfield, Lawrence F

    2014-11-01

    There are tremendous variations in diapering practices, reflecting varying cultural practices and regional difference. Around the world, more than 134 million babies are born each year, a rate of 255 births per minute or 4.3 births each second. While global population growth has been steadily declining from its peak in 1963, several regions, including the Middle East and Sub-Saharan Africa, continue to maintain high birth rates. Though the essential needs of infants are largely similar, family habits and practices during early years of life vary dramatically. This article surveys data documenting variations in diaper frequency, types, and duration of use internationally, including age of toilet training. These factors may influence diaper rash and skin health of infants and young children. Much of this data was collected as part of analysis of the international commercial diaper market, evaluated and organized as part of an international initiative on Global Infant Skin Care, and presented to a panel of experts for critique and commentary in a symposium held in December, 2013. PMID:25403934

  4. Food Habits of Young-of-the-Year Walleyes in Okobojo Bay of Lake Oahe, South Dakota

    Microsoft Academic Search

    Jeffrey J. Jackson; David W. Willis; David G. Fielder

    1992-01-01

    Food habits of young-of-the-year walleyes (Stizostedion vitreum) were determined in Okobojo Bay of Lake Oahe, South Dakota from June through September, 1991. Walleyes initially fed on zooplankton but soon became piscivorous. Smallmouth buffalo (Ictiobus bubalus) were initially the most important prey fish, but rainbow smelt (Osmerus mordax) became important as walleyes moved from the littoral zone of the bay to

  5. Setting the Stage for Habitable Planets

    PubMed Central

    Gonzalez, Guillermo

    2014-01-01

    Our understanding of the processes that are relevant to the formation and maintenance of habitable planetary systems is advancing at a rapid pace, both from observation and theory. The present review focuses on recent research that bears on this topic and includes discussions of processes occurring in astrophysical, geophysical and climatic contexts, as well as the temporal evolution of planetary habitability. Special attention is given to recent observations of exoplanets and their host stars and the theories proposed to explain the observed trends. Recent theories about the early evolution of the Solar System and how they relate to its habitability are also summarized. Unresolved issues requiring additional research are pointed out, and a framework is provided for estimating the number of habitable planets in the Universe. PMID:25370028

  6. Habitable piers : an alternative for urban expansion

    E-print Network

    Lin, Chin Yuan, M. Arch. Massachusetts Institute of Technology

    1990-01-01

    This thesis is an investigation into an alternative way of urban expansion for a seaside community. This thesis proposes a habitable urban environment on the water by creating for an exchange between the built urban landscape ...

  7. Development of the Eating Habits Questionnaire 

    E-print Network

    Graham, Erin Collins

    2005-02-17

    The purpose of the studies presented was to develop and examine the psychometric properties of the Eating Habits Questionnaire (EHQ). The author designed the 21-item self-report inventory to assess cognitions, behaviors, and feelings related...

  8. Investigating habits: strategies, technologies and models

    E-print Network

    Smith, Kyle S.

    Understanding habits at a biological level requires a combination of behavioral observations and measures of ongoing neural activity. Theoretical frameworks as well as definitions of habitual behaviors emerging from classic ...

  9. An evaluation of Skylab habitability hardware

    NASA Technical Reports Server (NTRS)

    Stokes, J.

    1974-01-01

    For effective mission performance, participants in space missions lasting 30-60 days or longer must be provided with hardware to accommodate their personal needs. Such habitability hardware was provided on Skylab. Equipment defined as habitability hardware was that equipment composing the food system, water system, sleep system, waste management system, personal hygiene system, trash management system, and entertainment equipment. Equipment not specifically defined as habitability hardware but which served that function were the Wardroom window, the exercise equipment, and the intercom system, which was occasionally used for private communications. All Skylab habitability hardware generally functioned as intended for the three missions, and most items could be considered as adequate concepts for future flights of similar duration. Specific components were criticized for their shortcomings.

  10. Dynamics of exoplanetary systems, links to their habitability

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  11. Habitability of Exomoons at the Hill or Tidal Locking Radius

    E-print Network

    Hinkel, Natalie R

    2013-01-01

    Moons orbiting extrasolar planets are the next class of object to be observed and characterized for possible habitability. Like the host-planets to their host-star, exomoons have a limiting radius at which they may be gravitationally bound, or the Hill radius. In addition, they also have a distance at which they will become tidally locked and therefore in synchronous rotation with the planet. We have examined the flux phase profile of a simulated, hypothetical moon orbiting at a distant radius around the confirmed exoplanets mu Ara b, HD 28185 b, BD +14 4559 b, and HD 73534 b. The irradiated flux on a moon at it's furthest, stable distance from the planet achieves it's largest flux gradient, which places a limit on the flux ranges expected for subsequent (observed) moons closer in orbit to the planet. We have also analyzed the effect of planetary eccentricity on the flux on the moon, examining planets that traverse the habitable zone either fully or partially during their orbit. Looking solely at the stellar ...

  12. A Model of Habitability Within the Milky Way Galaxy

    E-print Network

    Gowanlock, Michael G; McConnell, Sabine M

    2011-01-01

    We present a model of the Galactic Habitable Zone (GHZ), described in terms of the spatial and temporal dimensions of the Galaxy that may favour the development of complex life. The Milky Way galaxy is modelled using a computational approach by populating stars and their planetary systems on an individual basis using Monte-Carlo methods. We begin with well-established properties of the disk of the Milky Way, such as the stellar number density distribution, the initial mass function, the star formation history, and the metallicity gradient as a function of radial position and time. We vary some of these properties, creating four models to test the sensitivity of our assumptions. To assess habitability on the Galactic scale, we model supernova rates, planet formation, and the time required for complex life to evolve. Our study improves on other literature on the GHZ by populating stars on an individual basis and by modelling SNII and SNIa sterilizations by selecting their progenitors from within this preexistin...

  13. Investigating habits: strategies, technologies and models

    PubMed Central

    Smith, Kyle S.; Graybiel, Ann M.

    2014-01-01

    Understanding habits at a biological level requires a combination of behavioral observations and measures of ongoing neural activity. Theoretical frameworks as well as definitions of habitual behaviors emerging from classic behavioral research have been enriched by new approaches taking account of the identification of brain regions and circuits related to habitual behavior. Together, this combination of experimental and theoretical work has provided key insights into how brain circuits underlying action-learning and action-selection are organized, and how a balance between behavioral flexibility and fixity is achieved. New methods to monitor and manipulate neural activity in real time are allowing us to have a first look “under the hood” of a habit as it is formed and expressed. Here we discuss ideas emerging from such approaches. We pay special attention to the unexpected findings that have arisen from our own experiments suggesting that habitual behaviors likely require the simultaneous activity of multiple distinct components, or operators, seen as responsible for the contrasting dynamics of neural activity in both cortico-limbic and sensorimotor circuits recorded concurrently during different stages of habit learning. The neural dynamics identified thus far do not fully meet expectations derived from traditional models of the structure of habits, and the behavioral measures of habits that we have made also are not fully aligned with these models. We explore these new clues as opportunities to refine an understanding of habits. PMID:24574988

  14. Habitable worlds with no signs of life

    PubMed Central

    Cockell, Charles S.

    2014-01-01

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

  15. The peculiar circumstellar environment of NGC2024-IRS2

    E-print Network

    A. Lenorzer; A. Bik; A. de Koter; S. E. Kurtz; L. B. F. M. Waters; L. Kaper; C. E. Jones; T. R. Geballe

    2003-10-09

    We re-examine the nature of NGC2024-IRS2 in light of the recent discovery of the late O-type star, IRS2b, located 5 arcsec from IRS2. Using L-band spectroscopy, we set a lower limit of Av = 27.0 mag on the visual extinction towards IRS2. Arguments based on the nature of the circumstellar material, favor an Av of 31.5 mag. IRS2 is associated with the UCHII region G206.543-16.347 and the infrared source IRAS 05393-0156. We show that much of the mid-infrared emission towards IRS2, as well as the far infrared emission peaking at ~ 100 micron, do not originate in the direct surroundings of IRS2, but instead from an extended molecular cloud. Using new K-, L- and L'-band spectroscopy and a comprehensive set of infrared and radio continuum measurements from the literature, we apply diagnostics based on the radio slope, the strength of the infrared hydrogen recombination lines, and the presence of CO band-heads to constrain the nature and spatial distribution of the circumstellar material of IRS2. Using simple gaseous and/or dust models of prescribed geometry, we find strong indications that the infrared flux originating in the circumstellar material of IRS2 is dominated by emission from a dense gaseous disk with a radius of about 0.6 AU. At radio wavelengths the flux density distribution is best described by a stellar wind recombining at a radius of about 100 AU. Although NGC2024/IRS2 shares many similarities with BN-like objects, we do not find evidence for the presence of a dust shell surrounding this object. Therefore, IRS2 is likely more evolved.

  16. A hydrodynamic study of the circumstellar envelope of ? Scorpii

    NASA Astrophysics Data System (ADS)

    Braun, K.; Baade, R.; Reimers, D.; Hagen, H.-J.

    2012-10-01

    Context. Both the absolute mass-loss rates and the mechanisms that drive the mass loss of late-type supergiants are still not well known. Binaries such as ? Sco provide the most detailed empirical information about the winds of these stars. Aims: Our goal was to improve the binary technique for the determination of the mass-loss rate of ? Sco A by including a realistic density distribution and velocity field from hydrodynamic and plasma simulations. Methods: We performed 3D hydrodynamic simulations of the circumstellar envelope of ? Sco in combination with plasma simulations accounting for the heating, ionization, and excitation of the wind by the radiation of ? Sco B. These simulations served as the basis for an examination of circumstellar absorption lines in the spectrum of ? Sco B as well as of emission lines from the Antares nebula. Results: The present model of the extended envelope of ? Sco reproduces some of the structures that were observed in the circumstellar absorption lines in the spectrum of ? Sco B. Our theoretical density and velocity distributions of the outflow deviate considerably from a spherically expanding model, which was used in previous studies. This results in a higher mass-loss rate of (2 ± 0.5) × 10-6 M? yr-1. The hot H ii region around the secondary star induces an additional acceleration of the wind at large distances from the primary, which is seen in absorption lines of Ti ii and Cr ii at -30 km s-1. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under program ID 076.D-0690(A), and on observations made with the NASA/ESA Hubble Space Telescope (program # 5952), obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  17. Cepheids at high angular resolution: circumstellar envelope and pulsation

    NASA Astrophysics Data System (ADS)

    Gallenne, Alexandre

    2011-12-01

    In 2005, interferometric observations with VLTI/VINCI and CHARA/FLUOR revealed the existence of a circumstellar envelope (CSE) around some Cepheids. This surrounding material is particularly interesting for two reasons: it could have an impact on the distance estimates and could be linked to a past or on-going mass loss. The use of Baade-Wesselink methods for independent distance determinations could be significantly biased by the presence of these envelopes. Although their observations are difficult because of the high contrast between the photosphere of the star and the CSE, several observation techniques have the potential to improve our knowledge about their physical properties. In this thesis, I discuss in particular high angular resolution techniques that I applied to the study of several bright Galactic Cepheids. First, I used adaptive optic observations with NACO of the Cepheid RS Puppis, in order to deduce the flux ratio between the CSE and the photosphere of the star. In addition, I could carry out a statistical study of the speckle noise and inspect a possible asymmetry. Secondly, I analysed VISIR data to study the spectral energy distribution of a sample of Cepheids. These diffraction-limited images enabled me to carry out an accurate photometry in the N band and to detect an IR excess linked to the presence of a circumstellar component. On the other hand, applying a Fourier analysis I showed that some components are resolved. I then explored the K' band with the recombination instrument FLUOR for some bright Cepheids. Thanks to new set of data of Y Oph, I improved the study of its circumstellar envelope, using a ring-like model for the CSE. For two other Cepheids, U Vul and S Sge, I applied the interferometric Baade-Wesselink method in order to estimate their distance.

  18. IR emission from circumstellar envelopes of C-rich stars

    NASA Technical Reports Server (NTRS)

    Blanco, A.; Borghesi, A.; Bussoletti, E.; Colangeli, Luigi; Fonti, Sergio; Orofino, Vincenso

    1989-01-01

    The reliability of a theoretical model that solves the radiative transfer equation in dust clouds surrounding a central star is checked. In particular, it is found that both classical scattering by dust and the back-heating effects are negligible in the radiative transfer when envelopes similar to IRC+10216 are taken into consideration. In addition, new fits of IRC+10216 spectra are presented which were obtained, when the source is in different luminosity phases, under the assumption that amorphous carbon grains are in the circumstellar envelope. The same model is currently used to simulate the emission from carbon-rich sources showing the silicon carbide feature at 11.3 microns.

  19. Photochemistry and molecular ions in oxygen-rich circumstellar envelopes

    NASA Technical Reports Server (NTRS)

    Mamon, G. A.; Glassgold, A. E.; Omont, A.

    1987-01-01

    A theory for the ionization of the circumstellar envelopes around O-rich red giants is developed from the photochemical model. The main source of ionization is photoionization of H2O, OH, and C by the interstellar UV radiation field, supplemented by cosmic-ray ionization of hydrogen. Significant amounts of H3O(+) and HCO(+) are produced, with peak abundances of about 10 to the -7th at intermediate distances from the star. Although H3O(+) may be difficult to detect with current instrumentation, HCO(+) is probably detectable in nearby O-rich envelopes with large millimeter-wave telescopes.

  20. Properties of the circumstellar dust in galactic FS CMa objects

    NASA Astrophysics Data System (ADS)

    Miroshnichenko, Anatoly S.; Gray, Richard O.; Bjorkman, Karen S.; Rudy, Richard J.; Lynch, David K.; Carciofi, Alex C.

    2011-07-01

    FS CMa objects are a group of hot stars that exhibit the B[e] phenomenon. The group was defined a few years ago on the basis of the formerly known unclassified B[e] stars and newly discovered objects. One of their main features is the presence of hot circumstellar dust whose properties were unknown. We present IR spectra of nearly 20 FS CMa objects obtained with the Spitzer Space Telescope. Dusty features, such as broad silicate bands in emission and narrow bands that are usually explained by PAHs, are detected. The IR fluxes are compared to those detected by IRAS and MSX. Main results of the data analysis are briefly discussed.

  1. Early evolution of spherical ejecta expanding into the circumstellar matter at ultra-relativistic speeds

    E-print Network

    Shigeyama, Toshikazu; Nakamura, Ko

    2012-01-01

    We present a new self-similar solution describing early evolution of an ultra-relativistic flow resulting from a collision of homologously expanding spherical ejecta with the circumstellar matter, in which a shock wave propagates in the circumstellar matter while a weak discontinuity propagates in the ejecta at the sound speed

  2. Habitability of the Goldilocks planet Gliese 581g: results from geodynamic models

    NASA Astrophysics Data System (ADS)

    von Bloh, W.; Cuntz, M.; Franck, S.; Bounama, C.

    2011-04-01

    Aims: In 2010, detailed observations have been published that seem to indicate another super-Earth planet in the system of Gliese 581, which is located in the midst of the stellar climatological habitable zone. The mass of the planet, known as Gl 581g, has been estimated to be between 3.1 and 4.3 M?. In this study, we investigate the habitability of Gl 581g based on a previously used concept that explores its long-term possibility of photosynthetic biomass production, which has already been used to gauge the principal possibility of life regarding the super-Earths Gl 581c and Gl 581d. Methods: A thermal evolution model for super-Earths is used to calculate the sources and sinks of atmospheric carbon dioxide. The habitable zone is determined by the limits of photosynthetic biological productivity on the planetary surface. Models with different ratios of land/ocean coverage are pursued. Results: The maximum time span for habitable conditions is attained for water worlds at a position of about 0.14 ± 0.015 AU, which deviates by just a few percent (depending on the adopted stellar luminosity) from the actual position of Gl 581g, an estimate that does however not reflect systematic uncertainties inherent in our model. Therefore, in the framework of our model an almost perfect Goldilock position is realized. The existence of habitability is found to critically depend on the relative planetary continental area, lending a considerable advantage to the possibility of life if Gl 581g's ocean coverage is relatively high. Conclusions: Our results are another step toward identifying the possibility of life beyond the Solar System, especially concerning super-Earth planets, which appear to be more abundant than previously surmised.

  3. A circumstellar molecular gas structure associated with the massive young star Cepheus A-HW 2

    NASA Technical Reports Server (NTRS)

    Torrelles, Jose M.; Rodriguez, Luis F.; Canto, Jorge; Ho, Paul T. P.

    1993-01-01

    We report the detection via VLA-D observations of ammonia of a circumstellar high-density molecular gas structure toward the massive young star related to the object Cepheus A-HW 2, a firm candidate for the powering source of the high-velocity molecular outflow in the region. We suggest that the circumstellar molecular gas structure could be related to the circumstellar disk previously suggested from infrared, H2O, and OH maser observations. We consider as a plausible scenario that the double radio continuum source of HW 2 could represent the ionized inner part of the circumstellar disk, in the same way as proposed to explain the double radio source in L1551. The observed motions in the circumstellar molecular gas can be produced by bound motions (e.g., infall or rotation) around a central mass of about 10-20 solar masses (B0.5 V star or earlier).

  4. The Search for Habitable Worlds

    NASA Astrophysics Data System (ADS)

    Latham, David W.

    2013-06-01

    We live at a very special time in the history of astronomy. We are poised to discover and characterizes exoplanets enough like the Earth that we can imagine life as we know it could arise and be comfortable. We are seeking rocky planets at the right distances from their host stars for water to be liquid on the surface, and with a secondary atmosphere that might even show evidence for biogenic gases. Transiting planets are where the present action is, because they can provide masses and radii for planets, and thus the bulk properties such as density and surface gravity that constrain our models of their interior structure and composition. Are they ice giants like Uranus and Neptune, or rocky worlds like the terrestrial planets, or maybe something in between with lots of water or extended atmospheres of hydrogen and helium? NASA's Kepler mission has provided lots of small planet candidates, but the bottleneck for characterizing them is the ultra-precise radial velocities needed for confirming and characterizing the planets with mass determinations. HARPS-N has recently come into operation at the Telescopio Nazionale Galileo on La Palma and is now contributing to the follow up of Kepler candidates, but we need better ways to correct for astrophysical effects that distort the radial velocities, and still better velocity precision if we hope to reach the level of 9 cm/s induced by a true Earth twin in a one-year orbit around a star like the Sun. Kepler looks at only one four hundreth of the sky. We need all-sky surveys for transiting planets to find the nearest and brightest examples for radial-velocity follow up and studies of planetary atmospheres with missions like the James Webb Space Telescope and G-CLEF spectrograph on the Giant Magellan Telescope. Our long-range goal is to see if the atmospheres of any potentially habitable planets actually show evidence for biogenic gases that have been produced in large enough quantities to impact the biosphere and be detected remotely. If we detect spectroscopic biomarkers that can only be present if they are continually replenished by life, then we can point at that star and speculate that we may not be alone in the universe.

  5. Lycos Zone

    NSDL National Science Digital Library

    In the tradition of Yahooligans (reviewed in the March 22, 1996 Scout Report) and other so-called "green spaces," Lycos has created a new online safe haven for young users which is fairly self-contained, with the exception of the advertisements. (In response to criticisms regarding aggressive marketing to children at similar sites, Lycos claims that the ads are clearly marked and will not collect any personal information.) The site is composed of four sections: the Fun and Games Zone, the Homework Zone, the New and Cool Zone, and an area for parents and teachers. The first two sections are fairly deep, with numerous resources and activities aimed at various age levels. Some links in the Homework Zone lead users outside the site, but they are first presented with a gateway page informing them that they are leaving and offering advice on not divulging personal information.

  6. Far-Infrared Water Line Emissions from Circumstellar Outflows

    NASA Technical Reports Server (NTRS)

    Chen, Wesley; Neufeld, David A.

    1995-01-01

    We have modeled the far-infrared water line emission expected from circumstellar outflows from oxygen-rich late-type stars, as a function of the mass-loss rate and the terminal outflow velocity. For each mass-loss rate and terminal outflow velocity considered, we computed self-consistently the gas density, temperature, outflow velocity, and water abundance as a function of distance from the star. We then used an escape probability method to solve for the equilibrium level populations of 80 rotational states of water and thereby obtained predictions for the luminosity of a large number of far-infrared rotational transitions of water. In common with previous models, our model predicts that water will be copiously produced in the warm circumstellar gas and that water rotational emission will dominate the radiative cooling. However, our use of a realistic radiative cooling function for water leads to a lower gas temperature than that predicted in previous models. Our predictions for the far-infrared water line luminosities are consequently significantly smaller than those obtained in previous studies. Observations to be carried out by the Infrared Space Observatory will provide a crucial test of the models presented here.

  7. THE PROGENITOR OF SN 2011ja: CLUES FROM CIRCUMSTELLAR INTERACTION

    SciTech Connect

    Chakraborti, Sayan [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ray, Alak; Yadav, Naveen [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400 005 (India); Smith, Randall [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ryder, Stuart [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Sutaria, Firoza [Indian Institute of Astrophysics, Koramangala, Bangalore (India); Dwarkadas, Vikram V. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Chandra, Poonam [Department of Physics, Royal Military College of Canada, Kingston, ON K7K 7B4 (Canada); Pooley, David [Department of Physics, Sam Houston State University, Huntsville, TX (United States); Roy, Rupak, E-mail: schakraborti@fas.harvard.edu [Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital (India)

    2013-09-01

    Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until core collapse, produce Type II plateau (IIP) supernovae. The ejecta from these explosions shocks the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray parts of the electromagnetic spectrum. Observed together, they allow us to break the degeneracy between shock acceleration and magnetic field amplification. In this work, we use X-rays observations from the Chandra and radio observations from the Australia Telescope Compact Array to study the relative importance of processes which accelerate particles and those which amplify magnetic fields in producing the non-thermal radiation from SN 2011ja. We use radio observations to constrain the explosion date. Multiple Chandra observations allow us to probe the history of variable mass loss from the progenitor. The ejecta expands into a low-density bubble followed by interaction with a higher density wind from a red supergiant consistent with M{sub ZAMS} {approx}> 12 M{sub Sun }. Our results suggest that a fraction of Type IIP supernovae may interact with circumstellar media set up by non-steady winds.

  8. Archival legacy investigations of circumstellar environments: overview and first results

    NASA Astrophysics Data System (ADS)

    Choquet, Élodie; Pueyo, Laurent; Hagan, J. Brendan; Gofas-Salas, Elena; Rajan, Abhijith; Chen, Christine; Perrin, Marshall D.; Debes, John; Golimowski, David; Hines, Dean C.; N'Diaye, Mamadou; Schneider, Glenn; Mawet, Dimitri; Marois, Christian; Soummer, Rémi

    2014-08-01

    We are currently conducting a comprehensive and consistent re-processing of archival HST-NICMOS coronagraphic surveys using advanced PSF subtraction methods, entitled the Archival Legacy Investigations of Circumstellar Environments program (ALICE, HST/AR 12652). This virtual campaign of about 400 targets has already produced numerous new detections of previously unidentified point sources and circumstellar structures. We present five newly spatially resolved debris disks revealed in scattered light by our analysis of the archival data. These images provide new views of material around young solar-type stars at ages corresponding to the period of terrestrial planet formation in our solar system. We have also detected several new candidate substellar companions, for which there are ongoing followup campaigns (HST/WFC3 and VLT/SINFONI in ADI mode). Since the methods developed as part of ALICE are directly applicable to future missions (JWST, AFTA coronagraph) we emphasize the importance of devising optimal PSF subtraction methods for upcoming coronagraphic imaging missions. We describe efforts in defining direct imaging high-level science products (HLSP) standards that can be applicable to other coronagraphic campaigns, including ground-based (e.g., Gemini Planet Imager), and future space instruments (e.g., JWST). ALICE will deliver a first release of HLSPs to the community through the MAST archive at STScI in 2014.

  9. STIS Imaging of the HR 4796A Circumstellar Debris Ring

    NASA Astrophysics Data System (ADS)

    Schneider, G.; Weinberger, A. J.; Becklin, E. E.; Debes, J. H.; Smith, B. A.

    2009-01-01

    We have obtained high spatial resolution imaging observations of the HR 4796A circumstellar debris dust ring using the broad optical response of the Hubble Space Telescope Imaging Spectrograph (STIS) in coronagraphic mode. We use our visual wavelength observations to improve upon the earlier measured geometrical parameters of the ring-like disk. Two significant flux density asymmetries are noted: (1) preferential forward scattering by the disk grains and (2) an azimuthal surface brightness anisotropy about the morphological minor axis of the disk with corresponding differential ansal brightness. We find the debris ring offset from the location of the star by ~1.4 AU, a shift insufficient to explain the differing brightnesses of the northeast and southwest ansae simply by the 1/r 2 dimmunition of starlight. The STIS data also better quantify the radial confinement of the starlight-scattering circumstellar debris, to a characteristic region less than 14 AU in photometric half-width, with a significantly steeper inner truncation than outward falloff in radial surface brightness. The inferred spatial distribution of the disk grains is consistent with the possibility of one or more unseen co-orbital planetary-mass perturbers, and the colors of the disk grains are consistent with a collisionally evolved population of debris, possibly including ices reddened by radiation exposure to the central star.

  10. Multidimensional Simulations of Pair-Instability Supernovae and Circumstellar Interaction

    NASA Astrophysics Data System (ADS)

    Wheeler, J.

    2012-10-01

    The discovery of Super-Luminous Supernovae and other peculiar transient events imposed challenges to our understanding of the processes involved such as the energy input that powers their light curves and the environments in which their progenitors explode. Besides the high peak luminosity, the light curves of these events have a variety of shapes, rise-times and decline rates and a variety of spectral features that indicate of a variety of physical conditions that dominate their luminous output. Some of these events are thought to be associated with violent ejecta-circumstellar matter interaction causing the release of large amounts of shock-deposited energy. A few others are thought to be the manifestations of pair-instability supernovae producing massive amounts of nickel-56. Others may be powered by neutron star magnetic dipole radiation. So far only one-dimensional simulations of these various mechanisms have been presented. Multi-dimensional effects that will take into account mixing processes in the progenitor {convective and rotationally-induced}and the effects of rotation and hydrodynamic instabilities in the explosions are expected to alter the features observed in these events. We propose to perform multi-dimensional {2-D and 3-D} radiation hydrodynamics simulations for a variety of progenitor characteristics, explosion mechanisms, and circumstellar environments {including those deficient in H and He} in order to study those effects and ultimately better constrain the nature of the progenitors, the explosion mechanisms, and the environments of these spectacular cosmic events.

  11. An energetic stellar outburst accompanied by circumstellar light echoes.

    PubMed

    Bond, Howard E; Henden, Arne; Levay, Zoltan G; Panagia, Nino; Sparks, William B; Starrfield, Sumner; Wagner, R Mark; Corradi, R L M; Munari, U

    2003-03-27

    Some classes of stars, including novae and supernovae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of approximately 10(4). Unlike a supernova or nova, it did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into the surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of those light echoes, which allow us to set direct geometric distance limits to the object. At a distance of >6 kpc, V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way. The presence of the circumstellar dust implies that previous eruptions have occurred, and spectra show it to be a binary system. When combined with the high luminosity and unusual outburst behaviour, these characteristics indicate that V838 Mon represents a hitherto unknown type of stellar outburst, for which we have no completely satisfactory physical explanation. PMID:12660776

  12. Color Gradients Detected in the HD 15115 Circumstellar Disk

    E-print Network

    J. H. Debes; A. J. Weinberger; I. Song

    2008-07-21

    We report HST/NICMOS coronagraphic images of the HD 15115 circumstellar disk at 1.1\\micron. We find a similar morphology to that seen in the visible and at H band--an edge-on disk that is asymmetric in surface brightness. Several aspects of the 1.1\\micron data are different, highlighting the need for multi-wavelength images of each circumstellar disk. We find a flattening to the western surface brightness profile at 1.1\\micron interior to 2\\arcsec (90 AU) and a warp in the western half of the disk. We measure the surface brightness profiles of the two disk lobes and create a measure of the dust scattering efficiency between 0.55-1.65\\micron at 1\\arcsec, 2\\arcsec, and 3\\arcsec. At 2\\arcsec the western lobe has a neutral spectrum up to 1.1\\micron and a strong absorption or blue spectrum $>$1.1\\micron, while a blue trend is seen in the eastern lobe. At 1\\arcsec the disk has a red F110W-H color in both lobes.

  13. Circumstellar dust shells of hot post-AGB stars

    E-print Network

    Gauba, G S N

    2004-01-01

    Using a radiative transfer code (DUSTY) parameters of the circumstellar dust shells of 15 hot post-AGB stars have been derived. Combining the optical, near and far-infrared (ISO, IRAS) data of the stars, we have reconstructed their spectral energy distributions (SEDs) and estimated the dust temperatures, mass loss rates, angular radii of the inner boundary of the dust envelopes and the distances to these stars. The mass loss rates (10$^{-6}-10^{-5}$M$_{\\odot}$yr$^{-1}$) are intermediate between stars at the tip of the AGB and the PN phase. We have also studied the ISO spectra of 7 of these stars. Amorphous and crystalline silicate features were observed in IRAS14331-6435 (Hen3-1013), IRAS18062+2410 (SAO85766) and IRAS22023+5249 (LSIII +5224) indicating oxygen-rich circumstellar dust shells. The presence of unidentified infrared (UIR) band at 7.7$\\mu$, SiC emission at 11.5$\\mu$ and the "26$\\mu$" and "main 30$\\mu$" features in the ISO spectrum of IRAS17311-4924 (Hen3-1428) suggest that the central star may be c...

  14. STIS Imaging of the HR 4796A Circumstellar Debris Ring

    E-print Network

    G. Schneider; A. J. Weinberger; E. E. Becklin; J. H. Debes; B. A. Smith

    2008-10-01

    We have obtained high spatial resolution imaging observations of the HR 4796A circumstellar debris dust ring using the broad optical response of the Hubble Space Telescope Imaging Spectrograph in coronagraphic mode. We use our visual wavelength observations to improve upon the earlier measured geometrical parameters of the ring-like disk. Two significant flux density asymmetries are noted: (1) preferential forward scattering by the disk grains and (2) an azimuthal surface brightness anisotropy about the morphological minor axis of the disk with corresponding differential ansal brightness. We find the debris ring offset from the location of the star by ~1.4 AU, a shift insufficient to explain the differing brightnesses of the NE and SW ansae simply by the 1/$r^2$ dimmunition of starlight. The STIS data also better quantify the radial confinement of the starlight-scattering circumstellar debris, to a characteristic region orbital planetary-mass perturbers, and the colors of the disk grains are consistent with a collisionally evolved population of debris, possibly including ices reddened by radiation exposure to the central star.

  15. Habitability constraints/objectives for a mars manned mission: Internal architecture considerations

    NASA Astrophysics Data System (ADS)

    Winisdoerffer, F.; Soulez-Larivière, C.

    1992-08-01

    It is generally accepted that high quality internal environment shall strongly support crew's adaptation and acceptance to situation of long isolation and confinement. Thus, this paper is an attempt to determine to which extent the resulting stress corresponding to the anticipated duration of a trip to Mars (1 and a half years to 2 and a half years) could be decreased when internal architecture of the spacecraft is properly designed. It is assumed that artificial gravity shall be available on board the Mars spacecraft. This will of course have a strong impact on internal architecture as far as a 1-g oriented design will become mandatory, at least in certain inhabited parts of the spacecraft. The review of usual Habitability functions is performed according to the peculiarities of such an extremely long mission. A particular attention is paid to communications issues and the need for privacy. The second step of the paper addresses internal architecture issues through zoning analyses. Common, Service and Personal zones need to be adapted to the constraints associated with the extremely long duration of the mission. Furthermore, due to the nature of the mission itself (relative autonomy, communication problems, monotony) and the type of selected crew (personalities, group structure) the implementation of a ``fourth zone'', so-called ``recreational'' zone, seems to be needed. This zoning analysis is then translated into some internal architecture proposals, which are discussed and illustrated. This paper is concluded by a reflection on habitability and recommendations on volumetric requirements. Some ideas to validate proposed habitability items through simulation are also discussed.

  16. Habitability constraints/objectives for a Mars manned mission: internal architecture considerations.

    PubMed

    Winisdoerffer, F; Soulez-Larivière, C

    1992-01-01

    It is generally accepted that high quality internal environment shall strongly support crew's adaptation and acceptance to situation of long isolation and confinement. Thus, this paper is an attempt to determine to which extent the resulting stress corresponding to the anticipated duration of a trip to Mars (1 and a half years to 2 and a half years) could be decreased when internal architecture of the spacecraft is properly designed. It is assumed that artificial gravity shall be available on board the Mars spacecraft. This will of course have a strong impact on internal architecture as far as a 1-g oriented design will become mandatory, at least in certain inhabited parts of the spacecraft. The review of usual Habitability functions is performed according to the peculiarities of such an extremely long mission. A particular attention is paid to communications issues and the need for privacy. The second step of the paper addresses internal architecture issues through zoning analyses. Common, Service and Personal zones need to be adapted to the constraints associated with the extremely long duration of the mission. Furthermore, due to the nature of the mission itself (relative autonomy, communication problems, monotony) and the type of selected crew (personalities, group structure) the implementation of a "fourth zone", so-called "recreational" zone, seems to be needed. This zoning analysis is then translated into some internal architecture proposals, which are discussed and illustrated. This paper is concluded by a reflection on habitability and recommendations on volumetric requirements. Some ideas to validate proposed habitability items through simulation are also discussed. PMID:11536973

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    E-print Network

    Kainen, Paul C.

    N O P R I N TI N G Z O N E N O P R I N TI N G Z O N E N O P R I N TI N G Z O N E NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE NO PRINTING ZONE

  18. The Role of Water for Martian Habitability

    NASA Astrophysics Data System (ADS)

    Jaumann, R.; Tirsch, D.; Hauber, E.; Erkeling, G.; Le Deit, L.; Sowe, M.; Adeli, S.; Petau, A.; Reiss, D.

    2013-09-01

    A study in context with the Helmholtz Alliance 'Planetary Evolution and Life' focused on the (temporary) existence of liquid water, and the likelihood that Mars has been or even is a habitable planet. Both geomorphological and mineralogical evidence point to the episodic availability of liquid water at the surface of Mars, and physical modeling and small-scale observations suggest that this is also true for more recent periods. Habitable conditions, however, were not uniform over space and time. Several key properties, such as the availability of standing bodies of water, surface runoff and the transportation of nutrients, were not constant, resulting in an inhomogeneous nature of the parameter space that needs to be considered in any habitability assessment. The planetary evolution of Mars led to environmental changes, which in turn affected its habitability potential. Similarly, considerable environmental and climate variations due to latitudinal or elevation effects combined with a diverse surface geology caused distinctively different local conditions that influenced the planet`s habitable potential.

  19. Environmental Signatures for Habitability: What to Measure and How to Rank the Habitability Potential of Mars

    NASA Technical Reports Server (NTRS)

    Conrad, Pamela G.; Eigenbrode, Jennifer L.; Mahaffy, Paul M.; Steele, Andrew

    2011-01-01

    The environmental signatures for habitability are not necessarily biosignatures, even though on Earth, they are definitive proof of habitability. It is the constant overprint of the chemical signatures of life that makes it difficult to recognize the chemical and physical properties of a potentially habitable environment as distinct from an inhabited one. Mars Science Laboratory (MSL) will soon embark on a mission to Mars to assess its past or present habitability, so it is useful to examine how we measure habitability on Earth and prepare for how that approach may differ for Mars. This exercise includes: (a) articulation of fundamental assumptions about habitability, (b) an inventory of factors that affect habitability, (c) development of metrics, measurement approach and implementation, and (d) a new classification scheme for planetary habitability that goes beyond the binary "yes" or "no." There may be dozens of factors that affect habitability and they can be weighted as a function of specific environment. However a robotic, in situ investigation even on Earth has constraints that prevent the measurement of every environmental factor, so metrics must be reduced to the most relevant subset, given available time, cost, technical feasibility and scientific importance. Many of the factors could be measured with a combination of orbital data and the MSL payload. We propose that, at a minimum, a designation of high habitability potential requires the following conditions be met: (a) thermally stable with respect to extremes and frequency of fluctuation, (b) has more than one energy source, (c) sufficient chemical diversity to make compounds with covalent and hydrogen bonding, (d) can moderate ionizing radiation enough to allow a stable or evolving pool of organic molecules, (e) must have water or other high quality polar solvent, (f) must be able to renew chemical resources (e.g., plate tectonics, volcanism or something else we haven't envisioned). A measurement approach we have taken to measure habitability on Earth is : 1. Study remote sensing data, maps, etc. 2. Decide how big an area to measure. 3. Determine the spatial sampling rate. 4. Determine the temporal sampling rate. 5. Determine the order of measurements 6. Decide where to begin measurements 7. Select locations at field site and proceed While science drives each of the steps, there are additional constraints, e.g., technical, time, cost, safety (risk). This approach is also executable on Mars. Measurement of past habitability is more challenging both for Earth and Mars where access to the past means subsurface access and confrontation with unknowns about preservation of the martian past. Some environments preserve evidence of past habitability better than others, and this is where selection of the landing site to maximize the preservation potential of habitability indicators will be key. Mars presents an opportunity to discover transitional states between habitable or not, and we offer a ranking scale for planetary habitability with Mars as the second test subject: CLASS ONE Uninhabitable and likely has never been so CLASS TWO Has a high potential but no confirmed observation of life (as defined above) CLASS THREE Inhabited (we find life) 3-A Globally inhabited 3-B Primitive life; early in its evolution, but not yet globally established 3-C Exists only in refugia -- planet heading toward class four CLASS FOUR Post-habitable (there once was life, but now it's gone) MSL provides an opportunity to carefully investigate the habitability of at least one site on Mars and it will reveal much about the possible states of planetary habitability

  20. How to Directly Image a Habitable Planet Around Alpha Centauri with a ~30cm Space Telescope

    NASA Astrophysics Data System (ADS)

    Belikov, Ruslan; Acend Team, Acesat Team

    2015-01-01

    Several mission concepts are being studied to directly image planets around nearby stars. Direct imaging enables spectroscopic detection of biomarkers such as atmospheric oxygen and methane, which would be highly suggestive of extraterrestrial life. It is commonly thought that directly imaging a potentially habitable exoplanet requires telescopes with apertures of at least 1m, costing at least 1B, and launching no earlier than the 2020s.A notable exception to this is Alpha Centauri (A and B), which is an extreme outlier among FGKM stars in terms of apparent habitable zone size. Specifically, Alpha Centauri habitable zones span about 0.5-1' in stellocentric angle, ~3x wider than around any other FGKM star. This enables a ~30cm visible light space telescope equipped with a modern high performance coronagraph or starshade to resolve the habitable zone at high contrast and directly image any potentially habitable planet that may exist in the system. Due to the extreme apparent brightness of the stars, exposure times can be as short as minutes with ideal components, or days with realistic ones. This makes it possible to do color photometry on potentially habitable planets sufficient to differentiate Venus-like, Earth-like, and Mars-like planets from each other and establish the presence of Earth-pressure atmosphere through Rayleigh scattering.The raw contrast requirements for such an instrument can be relaxed to 1e-8 if the mission spends 2 years collecting tens of thousands of images on the same target, enabling a factor of 500-1000 speckle suppression in post processing. The light leak from both stars is controllable with a special wavefront control algorithm known as Multi-Star Wavefront Control (MSWC), which independently suppresses diffraction and aberrations from both stars using independent modes on the deformable mirror (see Thomas et al. at this conference).The presentation will describe the general studies and calculations in more detail and briefly present examples of small coronagraphic mission concepts currently being developed to take advantage of this opportunity. (For more detail about one such concept, see Bendek et al. at this conference).

  1. SN 2007od: A TYPE IIP SUPERNOVA WITH CIRCUMSTELLAR INTERACTION

    SciTech Connect

    Andrews, J. E.; Gallagher, J. S.; Clayton, Geoffrey C.; Chatelain, J. P.; Clem, J., E-mail: jandrews@phys.lsu.ed, E-mail: jgallagher@phys.lsu.ed, E-mail: gclayton@fenway.phys.lsu.ed, E-mail: jchate6@tigers.lsu.ed, E-mail: jclem@phys.lsu.ed [Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803 (United States)

    2010-05-20

    SN 2007od exhibits characteristics that have rarely been seen in a Type IIP supernova (SN). Optical V-band photometry reveals a very steep brightness decline between the plateau and nebular phases of {approx}4.5 mag, likely due to SN 2007od containing a low mass of {sup 56}Ni. The optical spectra show an evolution from normal Type IIP with broad H{alpha} emission, to a complex, four-component H{alpha} emission profile exhibiting asymmetries caused by dust extinction after day 232. This is similar to the spectral evolution of the Type IIn SN 1998S, although no early-time narrow ({approx}200 km s{sup -1}) H{alpha} component was present in SN 2007od. In both SNe, the intermediate-width H{alpha} emission components are thought to arise in the interaction between the ejecta and its circumstellar medium (CSM). SN 2007od also shows a mid-infrared excess due to new dust. The evolution of the H{alpha} profile and the presence of the mid-IR excess provide strong evidence that SN 2007od formed new dust before day 232. Late-time observations reveal a flattening of the visible light curve. This flattening is a strong indication of the presence of a light echo, which likely accounts for much of the broad, underlying H{alpha} component seen at late times. We believe that the multi-peaked H{alpha} emission is consistent with the interaction of the ejecta with a circumstellar ring or torus (for the inner components at {+-}1500 km s{sup -1}) and a single blob or cloud of circumstellar material out of the plane of the CSM ring (for the outer component at -5000 km s{sup -1}). The most probable location for the formation of new dust is in the cool dense shell created by the interaction between the expanding ejecta and its CSM. Monte Carlo radiative transfer modeling of the dust emission from SN 2007od implies that up to {approx}4 x 10{sup -4} M{sub sun} of new dust has formed. This is similar to the amounts of dust formed in other core-collapse supernovae such as SNe 1999em, 2004et, and 2006jc.

  2. The Three-dimensional Circumstellar Environment of SN 1987A

    NASA Astrophysics Data System (ADS)

    Sugerman, Ben E. K.; Crotts, Arlin P. S.; Kunkel, William E.; Heathcote, Stephen R.; Lawrence, Stephen S.

    2005-07-01

    Surrounding SN 1987A is a three-ring nebula attributed to interacting stellar winds, yet no model has successfully reproduced this system. Fortunately, the progenitor's mass-loss history can be reconstructed using light echoes, in which scattered light from the supernova traces the three-dimensional morphology of its circumstellar dust. In this paper, we construct and analyze the most complete map to date of the progenitor's circumstellar environment, using ground- and space-based imaging from the past 16 years. PSF-matched difference-imaging analyses of data from 1988 through 1997 reveal material between 1 and 28 lt-yr from the SN. Previously known structures, such as an inner hourglass, Napoleon's Hat, and a contact discontinuity, are probed in greater spatial detail than before. Previously unknown features are also discovered, such as a southern counterpart to Napoleon's Hat. Careful analyses of these echoes allows the reconstruction of the probable circumstellar environment, revealing a richly structured bipolar nebula. An outer, double-lobed ``Peanut,'' which is believed to be the contact discontinuity between red supergiant and main-sequence winds, is a prolate shell extending 28 lt-yr along the poles and 11 lt-yr near the equator. Napoleon's Hat, previously believed to be an independent structure, is the waist of this Peanut, which is pinched to a radius of 6 lt-yr. Interior to this is a cylindrical hourglass, 1 lt-yr in radius and 4 lt-yr long, which connects to the Peanut by a thick equatorial disk. The nebulae are inclined 41° south and 8° east of the line of sight, slightly elliptical in cross section, and marginally offset west of the SN. From the hourglass to the large, bipolar lobes, echo fluxes suggest that the gas density drops from 1-3 to >~0.03 cm-3, while the maximum dust-grain size increases from ~0.2 to 2 ?m, and the silicate:carbonaceous dust ratio decreases. The nebulae have a total mass of ~1.7 Msolar. The geometry of the three rings is studied, suggesting the northern and southern rings are located 1.3 and 1.0 lt-yr from the SN, while the equatorial ring is elliptical (b/a<~0.98), and spatially offset in the same direction as the hourglass.

  3. HABITABILITY OF EARTH-MASS PLANETS AND MOONS IN THE KEPLER-16 SYSTEM

    SciTech Connect

    Quarles, B.; Musielak, Z. E.; Cuntz, M., E-mail: billyq@uta.edu, E-mail: zmusielak@uta.edu, E-mail: cuntz@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019 (United States)

    2012-05-01

    We demonstrate that habitable Earth-mass planets and moons can exist in the Kepler-16 system, known to host a Saturn-mass planet around a stellar binary, by investigating their orbital stability in the standard and extended habitable zone (HZ). We find that Earth-mass planets in satellite-like (S-type) orbits are possible within the standard HZ in direct vicinity of Kepler-16b, thus constituting habitable exomoons. However, Earth-mass planets cannot exist in planetary-like (P-type) orbits around the two stellar components within the standard HZ. Yet, P-type Earth-mass planets can exist superior to the Saturnian planet in the extended HZ pertaining to considerably enhanced back-warming in the planetary atmosphere if facilitated. We briefly discuss the potential detectability of such habitable Earth-mass moons and planets positioned in satellite and planetary orbits, respectively. The range of inferior and superior P-type orbits in the HZ is between 0.657-0.71 AU and 0.95-1.02 AU, respectively.

  4. The Solar Neighborhood XXIX: The Habitable Real Estate of our Nearest Stellar Neighbors

    E-print Network

    Cantrell, Justin R; White, Russel J

    2013-01-01

    We use the sample of known stars and brown dwarfs within 5 pc of the Sun, supplemented with AFGK stars within 10 pc, to determine which stellar spectral types provide the most habitable real estate --- defined to be locations where liquid water could be present on Earth-like planets. Stellar temperatures and radii are determined by fitting model spectra to spatially resolved broad-band photometric energy distributions for stars in the sample. The locations of the HZ's are calculated using an empirical formula for planetary surface temperature and assuming the condition of liquid water, called here the empirical habitable zone, or EHZ. Systems that have dynamically disruptive companions, assuming a 5:1 separation ratios for primary/secondary pairs and either object and a planet, are considered not habitable. We then derive a simple formula to predict the location of the EHZ for main sequence stars based on V-K color. We consider EHZ widths as more useful measures of the habitable real estate around stars than ...

  5. The Habitability and Detection of Earth-like Planets Orbiting Cool White Dwarfs

    NASA Astrophysics Data System (ADS)

    Fossati, L.; Bagnulo, S.; Haswell, C. A.; Patel, M. R.; Busuttil, R.; Kowalski, P. M.; Shulyak, D. V.; Sterzik, M. F.

    2012-09-01

    Since there are several ways planets can survive the giant phase of the host star, we examine the habitability and detection of planets orbiting white dwarfs. As a white dwarf cools from 6000 K to 4000 K, a planet orbiting at 0.01 AU would remain in the continuous habitable zone (CHZ) for ~8 Gyr. We show that photosynthetic processes can be sustained on such planets. The DNA-weighted UV radiation dose for an Earth-like planet in the CHZ is less than the maxima encountered on Earth, and hence non-magnetic white dwarfs are compatible with the persistence of complex life. Polarization due to a terrestrial planet in the CHZ of a cool white dwarf (CWD) is 102 (104) times larger than it would be in the habitable zone of a typical M-dwarf (Sun-like star). Polarimetry is thus a viable way to detect close-in rocky planets around white dwarfs. Multi-band polarimetry would also allow us to reveal the presence of a planet atmosphere, providing a first characterization. Planets in the CHZ of a 0.6 M ? white dwarf will be distorted by Roche geometry, and a Kepler-11d analog would overfill its Roche lobe. With current facilities a super-Earth-sized atmosphereless planet is detectable with polarimetry around the brightest known CWD. Planned future facilities render smaller planets detectable, in particular by increasing the instrumental sensitivity in the blue.

  6. The effects of stellar winds on the magnetospheres and potential habitability of exoplanets

    E-print Network

    See, Victor; Vidotto, Aline A; Petit, Pascal; Marsden, Stephen C; Jeffers, Sandra V; Nascimento, José Dias do

    2014-01-01

    Context: The principle definition of habitability for exoplanets is whether they can sustain liquid water on their surfaces, i.e. that they orbit within the habitable zone. However, the planet's magnetosphere should also be considered, since without it, an exoplanet's atmosphere may be eroded away by stellar winds. Aims: The aim of this paper is to investigate magnetospheric protection of a planet from the effects of stellar winds from solar-mass stars. Methods: We study hypothetical Earth-like exoplanets orbiting in the host star's habitable zone for a sample of 124 solar-mass stars. These are targets that have been observed by the Bcool collaboration. Using two wind models, we calculate the magnetospheric extent of each exoplanet. These wind models are computationally inexpensive and allow the community to quickly estimate the magnetospheric size of magnetised Earth-analogues orbiting cool stars. Results: Most of the simulated planets in our sample can maintain a magnetosphere of ~5 Earth radii or larger. T...

  7. Habitability of waterworlds: runaway greenhouses, atmospheric expansion, and multiple climate States of pure water atmospheres.

    PubMed

    Goldblatt, Colin

    2015-05-01

    There are four different stable climate states for pure water atmospheres, as might exist on so-called "waterworlds." I map these as a function of solar constant for planets ranging in size from Mars-sized to 10 Earth-mass. The states are as follows: globally ice covered (Ts?245?K), cold and damp (270?Ts?290?K), hot and moist (350?Ts?550?K), and very hot and dry (Tsx2A86;900?K). No stable climate exists for 290?Ts ?350?K or 550?Ts?900?K. The union of hot moist and cold damp climates describes the liquid water habitable zone, the width and location of which depends on planet mass. At each solar constant, two or three different climate states are stable. This is a consequence of strong nonlinearities in both thermal emission and the net absorption of sunlight. Across the range of planet sizes, I account for the atmospheres expanding to high altitudes as they warm. The emitting and absorbing surfaces (optical depth of unity) move to high altitude, making their area larger than the planet surface, so more thermal radiation is emitted and more sunlight absorbed (the former dominates). The atmospheres of small planets expand more due to weaker gravity; the effective runaway greenhouse threshold is about 35?W m(-2) higher for Mars, 10?W m(-2) higher for Earth or Venus, but only a few W m(-2) higher for a 10 Earth-mass planet. There is an underlying (expansion-neglected) trend of increasing runaway greenhouse threshold with planetary size (40?W m(-2) higher for a 10 Earth-mass planet than for Mars). Summing these opposing trends means that Venus-sized (or slightly smaller) planets are most susceptible to a runaway greenhouse. The habitable zone for pure water atmospheres is very narrow, with an insolation range of 0.07 times the solar constant. A wider habitable zone requires background gas and greenhouse gas: N2 and CO2 on Earth, which are biologically controlled. Thus, habitability depends on inhabitance. Key Words: Habitable zone-Runaway greenhouse-Waterworld-Climate. Astrobiology 15, 362-370. PMID:25984919

  8. The progenitor of SN 2011ja: Clues from circumstellar interaction

    E-print Network

    Chakraborti, Sayan; Smith, Randall; Ryder, Stuart; Yadav, Naveen; Sutaria, Firoza; Dwarkadas, Vikram V; Chandra, Poonam; Pooley, David; Roy, Rupak

    2013-01-01

    Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until the time of core collapse produce Type IIP (Plateau) supernovae. The ejecta from these explosions shock the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray part of the electromagnetic spectrum. Observed together, they allow us to break the degeneracy between shock acceleration and magnetic field amplification. In this work we use X-rays observations from the Chandra and radio observations from the ATCA to study the relative importance of particle acceleration and magnetic fields in producing the non-thermal radiation from SN 2011ja. We use radio observations to constrain the ...

  9. The composition of circumstellar gas and dust in 51 Oph

    E-print Network

    M. E. van den Ancker; G. Meeus; J. Cami; L. B. F. M. Waters; C. Waelkens

    2001-02-15

    We analyze ISO archive data of the nearby bright emission-line star 51 Oph, previously classified as a proto-planetary system similar to beta Pic. The infrared spectrum reveals the presence of gas-phase emission bands of hot (approx 850 K) CO, CO_2, H_2O and NO. In addition to this, partially crystalline silicate dust is present. The solid-state bands and the energy distribution are indicative of dust that has formed recently, rather than of debris dust. The presence of hot molecular gas and the composition of the circumstellar dust are highly unusual for a young star and are reminiscent of what is found around evolved (AGB) stars, although we exclude the possibility of 51 Oph belonging to this group. We suggest several explanations for the nature of 51 Oph, including a recent episode of mass loss from a Be star, and the recent destruction of a planet-sized body around a young star.

  10. PAH formation in carbon-rich circumstellar envelopes

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.; Frenklach, Michael

    1989-01-01

    While there is growing observational evidence that some fraction of interstellar carbon is in polycyclic aromatic hydrocarbons (PAH's), the mechanisms by which these molecules might be formed have not been extensively studied. A detailed investigation of PAH production in the outflowing molecular envelopes of carbon-rich red giant star is presented. The gasphase kinetics of a chemical reaction mechanism developed to study soot production in hydrocarbon flames is modified to apply in circumstellar environments. It was found that astrophysically significant quantities of PAH's can be formed in carbon star envelopes provided the gas is sufficiently dense and resides for a long time in the temperature range of 900 to 1100 k. The precise yield of PAH's is very sensitive to astronomical parameters of the envelope (e.g., mass loss rate, outflow velocity, and acetylene abundance) and certain poorly determined chemical reaction rates.

  11. Molecular anion chemistry in interstellar and circumstellar environments

    NASA Astrophysics Data System (ADS)

    Cordiner, M. A.; Millar, T. J.; Herbst, E.; Chuimin, R. Ni; Walsh, C.

    2007-12-01

    The recent detection of C4H-, C6H- and C8H- in TMC-1 and IRC+10216 led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed modeling shows that the column densities of C6H- observed in IRC+10216 and TMC-1 can be reproduced. Our calculations also predict that hydrocarbon anions CnH- (for n = 4, 6, 8) are viable candidates for detection in photon-dominated regions such as the Horsehead Nebula and the Orion Bar.

  12. Hydrocarbon Anions in Interstellar Clouds and Circumstellar Envelopes

    NASA Astrophysics Data System (ADS)

    Millar, T. J.; Walsh, C.; Cordiner, M. A.; Ní Chuimín, R.; Herbst, Eric

    2007-06-01

    The recent detection of the hydrocarbon anion C6H- in the interstellar medium has led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed modeling shows that the column densities of C6H- observed in IRC +10 216 and TMC-1 can be reproduced. Our calculations also predict that other hydrocarbon anions, such as C4H- and C8H-, are viable candidates for detection in IRC +10 216, TMC-1, and photon-dominated regions such as the Horsehead Nebula.

  13. Hydrocarbon anions in interstellar clouds and circumstellar envelopes

    E-print Network

    T. J. Millar; C. Walsh; M. A. Cordiner; R. Ní Chuimín; Eric Herbst

    2007-05-07

    The recent detection of the hydrocarbon anion C6H- in the interstellar medium has led us to investigate the synthesis of hydrocarbon anions in a variety of interstellar and circumstellar environments. We find that the anion/neutral abundance ratio can be quite large, on the order of at least a few percent, once the neutral has more than five carbon atoms. Detailed modeling shows that the column densities of C6H- observed in IRC+10216 and TMC-1 can be reproduced. Our calculations also predict that other hydrocarbon anions, such as C4H- and C8H-, are viable candidates for detection in IRC+10216, TMC-1 and photon-dominated regions such as the Horsehead Nebula.

  14. Linear polarization of hydroxyl masers in circumstellar envelope outer regions

    NASA Astrophysics Data System (ADS)

    Wolak, P.; Szymczak, M.; Gérard, E.

    2012-07-01

    A recent polarimetric survey of OH masers in a large sample of AGB and post-AGB stars revealed widespread occurrence of polarized features. We made a statistical analysis of the polarization properties of this large data set. We discuss the alignment of polarization position angles between the extreme blue- and red-shifted parts of the 1612 MHz spectrum. The average polarization angle of OH masers from the opposite sides of the envelope agrees within 20° for 80% of the sources in the sample. For two objects monitored over ~6 years the polarization position angle at 1612 MHz is constant within measurement uncertainties: this suggests a stable and a very regular structure of the circumstellar magnetic fields. Alternatively, this could indicate a galactic origin of the field which may be amplified by the stellar wind in the outermost parts of the envelopes.

  15. 1612 MHz OH maser emission from axisymmetric circumstellar envelopes - Miras

    NASA Technical Reports Server (NTRS)

    Collison, Alan J.; Fix, John D.

    1992-01-01

    Radiative transfer calculations are performed using a modified form of the Sobolev approximation to determine the inversion of the 1612 MHz line of OH in axisymmetric circumstellar envelopes around Miras. The mass loss is assumed to be occurring in the form of a smooth wind. Line profiles and maps are presented for three models of varying degrees of asymmetry and for various orientations of the envelopes. It is concluded that the axisymmetric models can reproduce many of the features of observed profiles and maps which both the standard, spherically symmetric model and the discrete emission model cannot easily explain. The model profiles reproduce all of the general features seen in the line profiles of real sources.

  16. Why all stars should possess circumstellar temperature inversions

    NASA Technical Reports Server (NTRS)

    Scudder, Jack D.

    1992-01-01

    The paper shows that the circumstellar temperature inversions possessed by all stars are the consequence of the 'velocity filtration' process described by Scudder (1992), according to which a stellar envelope is hotter than its underlying layers. The filtration scenario relies on the theoretically predicted and experimentally determined non-Maxwellian velocity distributions of ions and/or electrons in other sampled astrophysical plasmas and the transition region. The most immediate consequence is that the temperature and quasi-neutral plasma density become anticorrelated with increasing radius in a thin transition region, leaving the temperature profile inverted in excess of 10 exp 6 K up into a corona, without depositing a wave of magnetic field energy into the gas above the base of the transition region.

  17. Microwave emission from spinning dust in circumstellar disks

    E-print Network

    Roman R. Rafikov

    2006-02-01

    In the high density environments of circumstellar disks dust grains are expected to grow to large sizes by coagulation. Somewhat unexpectedly, recent near-IR observations of PAH features from disks around Herbig Ae/Be stars demonstrate that substantial amount of dust mass in these disks (up to several tens of per cent of the total carbon content) can be locked up in particles with sizes ranging from several to tens of nanometers. We investigate the possibility of detecting the electric dipole emission produced by these nanoparticles as they spin at thermal rates (tens of GHz) in cold gas. We show that such emission peaks in the microwave range and dominates over the thermal disk emission at \

  18. Circumstellar disks revealed by H/K flux variation gradients

    NASA Astrophysics Data System (ADS)

    Pozo Nuñez, F.; Haas, M.; Chini, R.; Ramolla, M.; Westhues, C.; Hodapp, K.-W.

    2015-06-01

    The variability of young stellar objects (YSO) changes their brightness and color preventing a proper classification in traditional color-color and color magnitude diagrams. We have explored the feasibility of the flux variation gradient (FVG) method for YSOs, using H and K band monitoring data of the star forming region RCW 38 obtained at the University Observatory Bochum in Chile. Simultaneous multi-epoch flux measurements follow a linear relation FH = ? + ?·FK for almost all YSOs with large variability amplitude. The slope ? gives the mean HK color temperature Tvar of the varying component. Because Tvar is hotter than the dust sublimation temperature, we have tentatively assigned it to stellar variations. If the gradient does not meet the origin of the flux-flux diagram, an additional non- or less-varying component may be required. If the variability amplitude is larger at the shorter wavelength, e.g. ?< 0, this component is cooler than the star (e.g. a circumstellar disk); vice versa, if ?> 0, the component is hotter like a scattering halo or even a companion star. We here present examples of two YSOs, where the HK FVG implies the presence of a circumstellar disk; this finding is consistent with additional data at J and L. One YSO shows a clear K-band excess in the JHK color-color diagram, while the significance of a K-excess in the other YSO depends on the measurement epoch. Disentangling the contributions of star and disk it turns out that the two YSOs have huge variability amplitudes (~3-5 mag). The HK FVG analysis is a powerful complementary tool to analyze the varying components of YSOs and worth further exploration of monitoring data at other wavelengths.

  19. TIDALLY INDUCED BROWN DWARF AND PLANET FORMATION IN CIRCUMSTELLAR DISKS

    SciTech Connect

    Thies, Ingo; Kroupa, Pavel [Argelander-Institut fuer Astronomie (Sternwarte), Universitaet Bonn, Auf dem Huegel 71, D-53121 Bonn (Germany); Goodwin, Simon P. [Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH (United Kingdom); Stamatellos, Dimitrios; Whitworth, Anthony P. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom)

    2010-07-01

    Most stars are born in clusters and the resulting gravitational interactions between cluster members may significantly affect the evolution of circumstellar disks and therefore the formation of planets and brown dwarfs (BDs). Recent findings suggest that tidal perturbations of typical circumstellar disks due to close encounters may inhibit rather than trigger disk fragmentation and so would seem to rule out planet formation by external tidal stimuli. However, the disk models in these calculations were restricted to disk radii of 40 AU and disk masses below 0.1 M{sub sun}. Here, we show that even modest encounters can trigger fragmentation around 100 AU in the sorts of massive ({approx}0.5 M{sub sun}), extended ({>=}100 AU) disks that are observed around young stars. Tidal perturbation alone can do this; no disk-disk collision is required. We also show that very low mass binary systems can form through the interaction of objects in the disk. In our computations, otherwise non-fragmenting massive disks, once perturbed, fragment into several objects between about 0.01 and 0.1 M{sub sun}, i.e., over the whole BD mass range. Typically, these orbit on highly eccentric orbits or are even ejected. While probably not suitable for the formation of Jupiter- or Neptune-type planets, our scenario provides a possible formation mechanism for BDs and very massive planets which, interestingly, leads to a mass distribution consistent with the canonical substellar initial mass function. As a minor outcome, a possible explanation for the origin of misaligned extrasolar planetary systems is discussed.

  20. The circumstellar environments of dusty main sequence stars

    NASA Astrophysics Data System (ADS)

    Gebrim, Antonio S. Hales

    Our current understanding of the formation of planetary systems is strongly linked to astronomical observations of gas and dust around young stars. This thesis is dedicated to studying the physical conditions acting in the circumstellar environments of pre-main sequence and early main sequence dusty stars. These early stellar ages correspond to the timescales over which planets are thought to be formed. The first part of this work is dedicated to a search for dusty early A-type stars in the northern galactic plane. Data from the IPHAS Ha survey is first used to select a sample of galactic A-type stars. This sample is then correlated with data from the Spitzer Space Telescope in order to search for 8 microns and 24 microns excesses associated with warm dust orbiting the stars. The improved photometric sensitivities of these new galactic surveys allow the list of known galactic 'Vega-like' sources to be extended to unexplored optical magnitude ranges (13.5 < r < 18.5 mags). Only 1.1% of a sample of 3062 A-type stars with available optical to mid-infrared spectral energy distributions showed detectable excesses at 8 microns. Searching over 1860 stars observed at 24 microns yielded similar statistical results (1.2%). Only 10 stars have both 8 and 24 micron excesses. These results support the idea that warm dust located relatively close to the stars is rare in main sequence systems. Follow-up observations of this new sample of dust-excess stars will provide better insights into the properties of the systems. Resolved images are crucial for understanding the dynamics and evolution of proto-planetary disks. Observing the detailed disk structure requires high-contrast, high-spatial resolution imaging very close to the bright central star. As a consequence, only a handful of these systems have yet been resolved. The second part of this work shows how near-infrared Polarimetric Imaging on the 3.8 meter United Kingdom Infrared Telescope can be used to obtain reflected-light images of dust-disks around dust excess stars. This technique allows one to automatically suppress the unpolarised light from the central star, increasing the dynamic range for detecting polarised light scattered by the dust present in circumstellar discs. The detections of extended disks around the classical T Tauri star TW Hya and the Herbig Ac star HD 169142 are reported, as well as the strong but spatially unresolved polarization signals measured toward two other Herbig Ae stars. Monte Carlo scattering simulations are used to fit the J-, H- and K-band polarization images of the disk around TW Hya, providing new constraints on the geometry of TW Hya's disk. The third part of this thesis is dedicated to studying the gas content and dynamics around dust-excess stars. The evolution of circumstellar gas is thought to be strongly linked to the formation of gaseous giant planets similar to Jupiter, Saturn and most currently known extra-solar planets. However, the timescales over which circumstellar gas discs dissipate remains poorly constrained, mainly due to the observational difficulties associated with detecting small amounts of circumstellar gas. An analysis of high-resolution (R 50 000) optical spectroscopic data of a sample of 'Vega-like' candidates from the catalogue of Mannings & Barlow (1998) is presented. Analysis of the stellar spectra allows one to search for narrow absorption features due to circumstellar gas and possible Falling Evaporating Bodies, similar to the ones seen in the (3 Pictoris system. None of the stars from this sample show emission line activity in either Ha, Ca II or Na I, indicating that accretion of material onto the stars has ceased and suggesting they are true main sequence Vega-like stars. Four stars were found to exhibit narrow absorption features near the cores of the photospheric Ca II and Na I D lines, with HD 110058 being the strongest candidate to host a (3 Pictoris-like gas disk. If confirmed, HD 110058 would represent the Vega-like star with the lowest Lir/L* value (3.7 x 10"4) around which a CS gas disk

  1. Structure and Evolution of Circumstellar Disks Around Young Stars: New Views from ISO

    E-print Network

    Michael R. Meyer; Steven V. W. Beckwith

    2000-01-31

    A question central to understanding the origin of our solar system is: how do planets form in circumstellar disks around young stars? Because of the complex nature of the physical processes involved, multi-wavelength observations of large samples will be required in order to obtain a complete answer to this question. Surveys undertaken with ISO have helped to solve pieces of this puzzle in addition to uncovering new mysteries. We review a variety of studies aimed at understanding; i) the physical structure and composition of circumstellar disks commonly found surrounding young stellar objects; and ii) the evolution of circumstellar disks from the active accretion phase to post-planet building debris disks.

  2. Radiological Habits Survey: Dumfries and Galloway Coast, 2007

    E-print Network

    Radiological Habits Survey: Dumfries and Galloway Coast, 2007 #12;This page has been intentionally left blank #12;Radiological Habits Survey: Dumfries and Galloway Coast, 2007 FINAL REPORT ...........................................................................................8 1.3 Dose limits and constraints

  3. Smoking habits of Greek preschool children's parents

    Microsoft Academic Search

    Constantine I Vardavas; Dimitrios Athanasopoulos; Evaggelia Balomenaki; Dora Niaounaki; Manolis K Linardakis; Anthony G Kafatos

    2007-01-01

    BACKGROUND: Smoking is Greece's largest public health threat. Greece has the highest adult smoking prevalence among all E.U countries, which in turn possibly predisposes Greek children and adolescents to smoke. The purpose of our study was to research into the smoking habits of preschool children's parents since children of that age could be vulnerable to parental negative role modeling and

  4. Nocturnal Habits of Platyedra gossypiella Saunders

    Microsoft Academic Search

    F. A. Squire

    1937-01-01

    IN the course of investigational work on Platyedra gossypiella, the pink bollworm of cotton, in the West Indies, observations were made on its nocturnal habits, concerning which but little is known. On the question of light attraction, for example, there has been a stalemate of opinions. Wilcocks1 in Egypt found that both sexes came to light readily; while Busck2 in

  5. Mushroom bodies regulate habit formation in Drosophila.

    PubMed

    Brembs, Björn

    2009-08-25

    To make good decisions, we evaluate past choices to guide later decisions. In most situations, we have the opportunity to simultaneously learn about both the consequences of our choice (i.e., operantly) and the stimuli associated with correct or incorrect choices (i.e., classically). Interestingly, in many species, including humans, these learning processes occasionally lead to irrational decisions. An extreme case is the habitual drug user consistently administering the drug despite the negative consequences, but we all have experience with our own, less severe habits. The standard animal model employs a combination of operant and classical learning components to bring about habit formation in rodents. After extended training, these animals will press a lever even if the outcome associated with lever-pressing is no longer desired. In this study, experiments with wild-type and transgenic flies revealed that a prominent insect neuropil, the mushroom bodies (MBs), regulates habit formation in flies by inhibiting the operant learning system when a predictive stimulus is present. This inhibition enables generalization of the classical memory and prevents premature habit formation. Extended training in wild-type flies produced a phenocopy of MB-impaired flies, such that generalization was abolished and goal-directed actions were transformed into habitual responses. PMID:19576773

  6. Pedagogical Practices: Nurturing and Maintaining Democratic Habits

    ERIC Educational Resources Information Center

    Hubler-Larimore, Lucretia Marie

    2011-01-01

    This case study examined the pedagogical practices of four teachers of one public elementary school whose mission seeks to nurture and maintain democratic habits for participation in a democratic society. Historically, public schools have been charged with the duty of preparing young minds to live within in a democratic society and as such this…

  7. Student Name ____________________________ THE SEARCH FOR HABITABLE PLANETS

    E-print Network

    Robeson, Scott M.

    Student Name ____________________________ A103 THE SEARCH FOR HABITABLE PLANETS LIFE technological societies of intelligent beings who ask questions about the Universe around them? Although the existence of extraterrestrial life has few practical consequences for our day-to-day lives, people can

  8. Recommendations for a Habitability Data Base.

    ERIC Educational Resources Information Center

    Illinois Univ., Urbana. Library Research Center.

    A prototype Habitability Data Base was developed for the United States Army Corps of Engineers. From a review of selected Army documents, standards in the form of goals or architectural criteria were identified as significant to man-environment relations (MER). A search of appropriate information systems was conducted to retrieve a minimum of 500…

  9. Habitability of planets around red dwarf stars.

    PubMed

    Heath, M J; Doyle, L R; Joshi, M M; Haberle, R M

    1999-08-01

    Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible. PMID:10472629

  10. Listening Habits of iPod Users

    ERIC Educational Resources Information Center

    Epstein, Michael; Marozeau, Jeremy; Cleveland, Sandra

    2010-01-01

    Purpose: To estimate real-environment iPod listening levels for listeners in 4 environments to gain insight into whether average listeners receive dosages exceeding occupational noise exposure guidelines as a result of their listening habits. Method: The earbud outputs of iPods were connected directly into the inputs of a digital recorder to make…

  11. Newspaper Readership Habits in the Black Community.

    ERIC Educational Resources Information Center

    Gibbons, R. Arnold

    This is a report of a survey conducted to determine newspaper readership habits of persons living within the circulation of the "Amsterdam News," a black weekly published in New York City. The survey was conducted with the purpose of increasing advertising revenues and assisting the management of the "Amsterdam News" with changes in the…

  12. Reading Habits of Adults in Egypt.

    ERIC Educational Resources Information Center

    Scales, Alice M.; Zikri, Lawrence B.

    Investigating the reading habits of adults in Egypt, East Africa, a study examined 294 Egyptians (233 males and 61 females) in post-secondary education in Cairo, and in the industrial cities of Shopra El-Khema, and Impapa, El-Giza. Marital status, sex, and occupation were used to group the subjects. Subjects completed a 29-item questionnaire…

  13. Planetary habitability: is Earth commonplace in the Milky Way?

    PubMed

    Franck, S; Block, A; von Bloh, W; Bounama, C; Garrido, I; Schellnhuber, H J

    2001-10-01

    Is there life beyond planet Earth? This is one of the grand enigmas which humankind tries to solve through scientific research. Recent progress in astronomical measurement techniques has confirmed the existence of a multitude of extra-solar planets. On the other hand, enormous efforts are being made to assess the possibility of life on Mars. All these activities have stimulated several investigations about the habitability of cosmic bodies. The habitable zone (HZ) around a given central star is defined as the region within which an Earth-like planet might enjoy the moderate surface temperatures required for advanced life forms. At present, there are several models determining the HZ. One class of models utilises climate constraints for the existence of liquid water on a planetary surface. Another approach is based on an integrated Earth system analysis that relates the boundaries of the HZ to the limits of photosynthetic processes. Within the latter approach, the evolution of the HZ for our solar system over geological time scales is calculated straightforwardly, and a convenient filter can be constructed that picks the candidates for photosynthesis-based life from all the extra-solar planets discovered by novel observational methods. These results can then be used to determine the average number of planets per planetary system that are within the HZ. With the help of a segment of the Drake equation, the number of "Gaias" (i.e. extra-solar terrestrial planets with a globally acting biosphere) is estimated. This leads to the thoroughly educated guess that there should exist half a million Gaias in the Milky Way. PMID:11729808

  14. Formation, Tidal Evolution, and Habitability of the Kepler-186 System

    NASA Astrophysics Data System (ADS)

    Bolmont, Emeline; Raymond, Sean N.; von Paris, Philip; Selsis, Franck; Hersant, Franck; Quintana, Elisa V.; Barclay, Thomas

    2014-09-01

    The Kepler-186 system consists of five planets orbiting an early M dwarf. The planets have physical radii of 1.0-1.50 R ? and orbital periods of 4-130 days. The 1.1 R ? Kepler-186f with a period of 130 days is of particular interest. Its insolation of roughly 0.32 S ? places it within the surface liquid water habitable zone (HZ). We present a multifaceted study of the Kepler-186 system, using two sets of parameters which are consistent with the data and also self-consistent. First, we show that the distribution of planet masses can be roughly reproduced if the planets were accreted from a high surface density disk presumably sculpted by an earlier phase of migration. However, our simulations predict the existence of one to two undetected planets between planets e and f. Next, we present a dynamical analysis of the system including the effect of tides. The timescale for tidal evolution is short enough that the four inner planets must have small obliquities and near-synchronous rotation rates. The tidal evolution of Kepler-186f is slow enough that its current spin state depends on a combination of its initial spin state, its dissipation rate, and the stellar age. Finally, we study the habitability of Kepler-186f with a one-dimensional climate model. The planet's surface temperature can be raised above 273 K with 0.5-5 bars of CO2, depending on the amount of N2 present. Kepler-186f represents a case study of an Earth-sized planet in the cooler regions of the HZ of a cool star.

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

    NASA Astrophysics Data System (ADS)

    Schwarz, Richard; Funk, Barbara; Bazsó, Ákos

    2015-06-01

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

  16. The Erasure of Habit: Tracing the Pedagogic Body

    ERIC Educational Resources Information Center

    Watkins, Megan

    2005-01-01

    While education involves much more than a set of habits, their formation is integral to learning. Within many Western countries, however, habit formation is no longer considered a pedagogic goal. Students may still acquire certain habits of learning as a function of schooling, but the process whereby teachers utilize a form of instruction designed…

  17. Summary of Radiological Habits Surveys in England and Wales,

    E-print Network

    Summary of Radiological Habits Surveys in England and Wales, 2013 Environment Report RL 11/13 Cefas RL 11/13 Final report Summary of Radiological Habits Surveys in England and Wales, 2002 to 2012 G of Radiological Habits Surveys in England and Wales, 2002 to 2012. RL 11/13. Cefas, Lowestoft A copy can

  18. Radiological Habits Survey: Environment Report RL 03/13

    E-print Network

    Radiological Habits Survey: 2013 Environment Report RL 03/13 Cefas contract report C2848 Radiological Habits Survey: Springfields, 2012 V.E. Ly, F.J. Clyne, C.J. Garrod and A. Dewar Peer reviewed by G.E., Clyne, F.J., Garrod, C.J. and Dewar, A., 2013. Radiological Habits Survey: Springfields, 2012. RL 03

  19. Radiological Habits Survey: Environment Report RL 03/12

    E-print Network

    Radiological Habits Survey: 2012 Environment Report RL 03/12 Cefas contract report C2848/12 Final report Radiological Habits Survey: Aldermaston and Burghfield, 2011 V.E. Ly, C.J. Garrod, F should be cited as: Ly, V.E., Garrod, C.J., Clyne, F.J. and Rumney, P., 2012. Radiological Habits Survey

  20. Radiological Habits Survey: Barrow and the south-west

    E-print Network

    Radiological Habits Survey: Barrow and the south-west 2013 Environment Report RL 01/13 Cefas Report RL 01/13 Final report Radiological Habits Survey: Barrow and the south-west Cumbrian coast, 2012 C.E., Rumney, P. and Papworth, G.P., 2013. Radiological Habits Survey: Barrow and the south-west Cumbrian coast

  1. Radiological Habits Survey: Environment Report RL 02a/13

    E-print Network

    Radiological Habits Survey: 2013 Environment Report RL 02a/13 Cefas contract report C2848 Low Level Final report Radiological Habits Survey: Low Level Waste Repository, 2012 F.J. Clyne, C.J. Garrod, V. and Papworth, G.P., 2013. Radiological Habits Survey: Low Level Waste Repository, 2012. RL 02a/13. Cefas

  2. Habitability of Terrestrial Planets in the Early Solar System

    Microsoft Academic Search

    N. H. SLEEP

    2001-01-01

    The Protoearth, Mars, Venus, and the Moon-forming impactor were potentially habitable in the early solar system. The interiors of larger asteroids had habitable circulating water. To see when the inner solar system became continuously habitable, one needs to consider the most dangerous events and the safest refugia from them. Early geochemical and accretionary processes set the subsequent silicate planet reservoirs

  3. Discovery of a Circumstellar Disk in the Lagoon Nebula

    NASA Astrophysics Data System (ADS)

    1997-04-01

    Circumstellar disks of gas and dust play a crucial role in the formation of stars and planets. Until now, high-resolution images of such disks around young stars within the Orion Nebula obtained with the Hubble Space Telescope (HST) constituted the most direct proof of their existence. Now, another circumstellar disk has been detected around a star in the Lagoon Nebula - also known as Messier 8 (M8) , a giant complex of interstellar gas and dust with many young stars in the southern constellation of Sagittarius and four times more distant than the Orion Nebula. The observations were carried out by an international team of scientists led by Bringfried Stecklum (Thüringer Landessternwarte, Tautenburg, Germany) [1] who used telescopes located at the ESO La Silla observatory and also observations from the HST archive. These new results are paving the road towards exciting research programmes on star formation which will become possible with the ESO Very Large Telescope. The harsh environment of circumstellar disks The existence of circumstellar disks has been inferred from indirect measurements of young stellar objects, such as the spectral energy distribution, the analysis of the profiles of individual spectral lines and measurements of the polarisation of the emitted light [2]. Impressive images of such disks in the Orion Nebula, known as proplyds (PROto-PLanetarY DiskS), have been obtained by the HST during the recent years. They have confirmed the interpretation of previous ground-based emission-line observations and mapping by radio telescopes. Moreover, they demonstrated that those disks which are located close to hot and massive stars are subject to heating caused by the intense radiation from these stars. Subsequently, the disks evaporate releasing neutral gas which streams off. During this process, shock fronts (regions with increased density) with tails of ionised gas result at a certain distance between the disk and the hot star. These objects appear on photos as tear-drop shaped, bright-rimmed areas with the cusps of the ionised regions aligned towards the exciting star. Such a region is also a very compact source of radio emission. Clearly, the harsh environment in which these disks reside does not favour planet formation. These findings were facilitated by the fact that, at a distance of `only' 1500 lightyears (about 450 parsec), the Orion Nebula is the closest site of high-mass star formation. Furthermore, many circumstellar disks around stars in this nebula are seen in silhouette against a bright and uniform background and are therefore comparatively easy to detect. The Lagoon Nebula In principle, similar phenomena should occur in any giant molecular cloud that gives rise to the birth of massive stars. However, the detection of such disks in other clouds would be very difficult, first of all because of their much larger distance. The Lagoon Nebula (M8) is located four times further away than the Orion Nebula and it is also a site of recent high-mass star formation. Its brightest part constitutes a conspicuous region of ionised hydrogen gas (an `HII-region') dubbed `The Hourglass' because of the resemblance. The gas in this area is ionised by the action of the nearby, hot star Herschel 36 (Her 36) . High-resolution radio maps show that the emission from the ionised gas peaks at 2.7 arcsec southeast of Her 36. An early explanation was that this emission is due to an unseen, massive star that is deeply embedded in the gas and dust and which is causing an ultra-compact HII-region (UCHR), catalogued as G5.97-1.17 according to its galactic coordinates. High-resolution images from ESO During a detailed investigation of such ultra-compact HII regions, Bringfried Stecklum and his colleagues found that, unlike ordinary UCHRs, this particular object is visible on optical images obtained with the HST Wide-Field Planetary Camera (HST-WFPC). This means that, contrary to the others, it is not deeply embedded in the nebula - its light reaches us directly without suffering a high degree of absorption. They subsequently obtai

  4. PAHs in circumstellar disks around T Tauri stars

    NASA Astrophysics Data System (ADS)

    Geers, Vincent C.; Augereau, Jean-Charles; Pontoppidan, Klaus M.; Dullemond, Cornelis P.; Visser, Ruud; van Dishoeck, Ewine F.; C2d Irs Team

    We have begun to investigate the emission from Polycyclic Aromatic Hydrocarbons seen toward circumstellar disks around young low mass pre-main-sequence (T Tauri) stars, observed as part of our Spitzer Legacy program "From Molecular Cores to Planet-Forming Disks" (Evans et al. 2003). In this poster we will present some of our first Spitzer spectra of PAH features in T Tauri stars and discuss these features in the context of the disk structure and the UV radiation field needed to excite the PAH molecules. Laboratory measurements show that PAH molecules are strongly heated/excited when they absorb a single UV photon, and that they re-radiate the energy through C-H and C-C stretch and C-H bending mode transitions, in the form of infrared photons. These give rise to characteristic PAH features at 3.3, 6.2, 7.7, 8.6, 11.2 and 12.8 microns. These emission features have now been observed toward about 60% of intermediate mass Herbig Ae/Be stars with the ISO satellite (Acke & van den Ancker 2004) and for a few of these sources, ground-based spatially resolved spectroscopy has confirmed that the emission originates from the inner ~100-150 AU region around the star (Geers et al. 2004, van Boekel et al. 2004, Habart et al. 2004), so typically on the scale of circumstellar disks. Our investigation of PAHs in disks around young stars takes two approaches. On the one hand, we address the question how the PAH abundance evolves in these disks during this period of planet formation and how their presence can have an impact on the circumstellar environment. The observed PAH emission is believed to originate from the surface layers of the disk, where the large molecules / small grains are mixed with the gas. The high opacity of PAHs to FUV radiation can significantly reduce the stellar UV field in the inner parts of the disk, while at the same time, through the photo-electric effect, PAHs can provide an important heating mechanism for the gas in the surrounding environment through photo-ionization and thereby influence the temperature and chemistry in the surface layers of the disks. On the other hand, the presence of PAHs can provide observers with important diagnostics for both the structure of the disk as well as the size of dust grains in the disk. Detections of PAH features provide diagnostics of the presence of small grains in the surface layer and can thus be used to address questions such as: do PAHs, as being the smallest "solid" particles, disappear at the same time as the silicate/carbon dust grains or do they have a longer timescale for settling and/or growth? If the timescales are different, how does this relate to the stability of the PAH to the UV field versus the PAH destruction in the inner region? These type of studies have, until recently, been restricted mostly to Herbig Ae/Be stars, which are relatively bright compared to T Tauri stars. With the arrival of the Spitzer Space Telescope we can now extend the studies of PAHs in disks to fainter low mass young stars. A key difference with the previously studied Herbig Ae/Be stars, is that for these sources of spectral type G and later, the stellar UV field is orders of magnitude weaker than for Herbig Ae/Be stars, which will directly affect the PAH excitation and emission. However, for these low mass sources accretion luminosity from the accretion of material onto the surface of the star can contribute significantly to the UV radiation and is expected to dominate the radiation field at wavelengths shorter than 0.55 microns, that is seen by the (inner regions of the) circumstellar disk (van Zadelhoff et al. 2003, Bergin et al. 2003). Our first results from the Spitzer spectra confirm this, since we observe much stronger PAH line fluxes than expected when the central star is assumed to be the main source of UV radiation. For the interpretation of the PAH features in disks around low mass stars, a PAH chemistry and emission model (Visser et al. in preparation) was recently coupled to 3D axi-symmetric radiative transfer models of circumstellar disks (Dulle

  5. Study of variable extinction of hot stars with circumstellar dust shells

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Various projects on the topic of hot stars with circumstellar dust are reported. The surface temperature, wind speed, and interstellar reddening were determined for the variable WC7 star HD 193793. Circumstellar carbon monoxide molecules were detected around a hot star. The dust envelope of the star W90 in the young cluster NGC2264 is discussed, and the spectra of low-redshift and X-ray emitting quasars are mentioned.

  6. Thermal-orbital coupled tidal heating and habitability of Martian-sized extrasolar planets around M stars

    SciTech Connect

    Shoji, D.; Kurita, K. [Earthquake Research Institute, University of Tokyo, Tokyo (Japan)

    2014-07-01

    M-type stars are good targets in the search for habitable extrasolar planets. Due to their low effective temperatures, the habitable zone of M stars is very close to the stars themselves. For planets that are close to their stars, tidal heating plays an important role in thermal and orbital evolutions, especially when the planet's orbit has a relatively large eccentricity. Although tidal heating interacts with the thermal state and the orbit of the planet, such coupled calculations for extrasolar planets around M stars have not been conducted. We perform coupled calculations using simple structural and orbital models and analyze the thermal state and habitability of a terrestrial planet. Considering this planet to be Martian-sized, the tide heats up and partially melts the mantle, maintaining an equilibrium state if the mass of the star is less than 0.2 times the mass of the Sun and the initial eccentricity of the orbit is more than 0.2. The reduction of heat dissipation due to the melted mantle allows the planet to stay in the habitable zone for more than 10 Gyr even though the orbital distance is small. The surface heat flux at the equilibrium state is between that of Mars and Io. The thermal state of the planet mainly depends on the initial value of the eccentricity and the mass of the star.

  7. Creatures of habit: accounting for the role of habit in implementation research on clinical behaviour change

    PubMed Central

    2012-01-01

    Background Social cognitive theories on behaviour change are increasingly being used to understand and predict healthcare professionals’ intentions and clinical behaviours. Although these theories offer important insights into how new behaviours are initiated, they provide an incomplete account of how changes in clinical practice occur by failing to consider the role of cue-contingent habits. This article contributes to better understanding of the role of habits in clinical practice and how improved effectiveness of behavioural strategies in implementation research might be achieved. Discussion Habit is behaviour that has been repeated until it has become more or less automatic, enacted without purposeful thinking, largely without any sense of awareness. The process of forming habits occurs through a gradual shift in cognitive control from intentional to automatic processes. As behaviour is repeated in the same context, the control of behaviour gradually shifts from being internally guided (e.g., beliefs, attitudes, and intention) to being triggered by situational or contextual cues. Much clinical practice occurs in stable healthcare contexts and can be assumed to be habitual. Empirical findings in various fields suggest that behaviours that are repeated in constant contexts are difficult to change. Hence, interventions that focus on changing the context that maintains those habits have a greater probability of success. Some sort of contextual disturbance provides a window of opportunity in which a behaviour is more likely to be deliberately considered. Forming desired habits requires behaviour to be carried out repeatedly in the presence of the same contextual cues. Summary Social cognitive theories provide insight into how humans analytically process information and carefully plan actions, but their utility is more limited when it comes to explaining repeated behaviours that do not require such an ongoing contemplative decisional process. However, despite a growing interest in applying behavioural theory in interventions to change clinical practice, the potential importance of habit has not been explored in implementation research. PMID:22682656

  8. Unveiling the circumstellar environment toward a massive young stellar object

    NASA Astrophysics Data System (ADS)

    Paron, S.; Fariña, C.; Ortega, M. E.

    2013-11-01

    Aims: As a continuation of a previous work, in which we found strong evidence of massive molecular outflows toward a massive star-forming site, we present a new study of this region based on very high angular resolution observations with the aim of discovering the outflow-driven mechanism. Methods: Using near-IR data acquired with Gemini-NIRI at the broad H- and Ks-bands, we studied a region of 22'' × 22'' around the UCHii region G045.47+0.05, a massive-star forming site at a distance of about 8 kpc. To image the source with the highest spatial resolution possible we employed the adaptative optics system ALTAIR, achieving an angular resolution of about 0.15 arcsec. Results: We discovered a cone shaped nebula that has an opening angle of about 90° and extends eastward of the IR source 2MASS J19142564+1109283, which is very likely a massive young stellar object (MYSO). This morphology suggests a cavity that was cleared in the circumstellar material, and its emission may arise from scattered continuum light, warm dust, and probably also from emission lines from shock-excited gas. The nebula, which presents arc-like features, is connected with the IR source through a jet-like structure, which is aligned with the blueshifted CO outflow found in a previous study. The near-IR structure lies ~3'' north of the radio continuum emission, revealing that it is not spatially coincident with the UCHii region. The observed morphology and structure of the near-IR nebula strongly suggest the presence of a precessing jet. We resolved the circumstellar environment (in scale of a thousand AU) of a distant MYSO, indeed one of the farthest currently known. Reduced NIR data (FITS) 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/559/L2

  9. Transition-Metal Oxides in Warm Circumstellar Environments

    NASA Astrophysics Data System (ADS)

    Schmidt, Miros?aw R.; Kaminski, Tomasz; Tylenda, Romuald

    2013-06-01

    We report on detections and simulations of electronic bands of transition-metal oxides, i.e. ScO, TiO, VO, CrO, YO, and of AlO, in spectra of two red novae V838 Mon and V4332 Sgr. These objects experienced a stellar merger event in 2002 and 1994, respectively, and have very rich circumstellar environments abundant in dust and molecules. We analyzed optical spectra of V838 Mon which show a presence of outflowing material. In this object, electronic systems of oxides are observed in absorption against a photospheric spectrum which resembles that of a late-type supergiant. We present simulations of the absorption bands which allowed us to derive the excitation temperatures of 300-500 K and constrain column densities, which turned out to be very high. Among many interesting features discovered, we identified forbidden transitions of TiO in the b^1?-X^3? and c^{1}?-X^{3}? systems, which are seen owing to the high column densities and the relatively low temperatures. In the case of the older red nova V4332 Sgr, the main object is surrounded by a circumstellar disc which is seen almost edge-on and obscures the central star. The molecular spectra are seen in emission in this object, what is very unusual in astrophysical sources observed at optical wavelengths. We show that these emission bands arise owing to the special geometry of the star-disk system and that radiative pumping is responsible for excitation of the molecules. From the shapes of the rotational contours, we derive temperatures of about 120 K in this object. Remarkably, the spectra of V4332 Sgr contain features of CrO, which is the first identified signature of this molecule in an astrophysical object. In addition to the excitation and radiative-transfer analysis of the molecular spectra, we discuss chemical pathways that could lead to the observed variety of metal oxides seen in these enigmatic sources. T. Kaminski, M. Schmidt, R. Tylenda, M. Konacki, and M. Gromadzki ApJSuppl., {182} (33), 2009. T. Kaminski, M. Schmidt and R. Tylenda Astronomy and Astrophysics, {522} (A75), 2010.

  10. STS mission duration enhancement study: (orbiter habitability)

    NASA Technical Reports Server (NTRS)

    Carlson, A. D.

    1979-01-01

    Habitability improvements for early flights that could be implemented with minimum impact were investigated. These included: (1) launching the water dispenser in the on-orbit position instead of in a locker; (2) the sleep pallet concept; and (3) suction cup foot restraints. Past studies that used volumetric terms and requirements for crew size versus mission duration were reviewed and common definitions of key habitability terms were established. An accurately dimensioned drawing of the orbiter mid-deck, locating all of the known major elements was developed. Finally, it was established that orbiter duration and crew size can be increased with minimum modification and impact to the crew module. Preliminary concepts of the aft med-deck, external versions of expanded tunnel adapters (ETA), and interior concepts of ETA-3 were developed and comparison charts showing the various factors of volume, weight, duration, size, impact to orbiter, and number of sleep stations were generated.

  11. Gambling Habits Among Aged African Americans

    Microsoft Academic Search

    Mohsen Bazargan; Shahrzad H. Bazargan; Mahfuja Akanda

    2001-01-01

    In a cross-sectional study we investigated the correlates of gambling habits among a sample of 80 independently living African-American elderly persons. The participants were selected from two Senior Citizen Centers that provide inexpensive or free pleasure trips from Los Angeles, California to gambling sites in Nevada. The data for this study were collected through face-to-face interviews conducted by three trained

  12. Habits of Mind for the Science Laboratory

    NSDL National Science Digital Library

    Charles Eick

    2005-09-01

    Laboratory experience should be an integral part of any high school science program, especially laboratory activities designed so that students gather data, explore concepts, and answer questions through inquiry. So, how can science teachers avoid negligence and minimize the risk of accidents when preparing for, instructing, and supervising students before, during, and after lab? Cultivating the following "habits of mind" at each stage of laboratory work is the first big step toward achieving safety in the laboratory setting.

  13. An energy balance concept for habitability.

    PubMed

    Hoehler, Tori M

    2007-12-01

    Habitability can be formulated as a balance between the biological demand for energy and the corresponding potential for meeting that demand by transduction of energy from the environment into biological process. The biological demand for energy is manifest in two requirements, analogous to the voltage and power requirements of an electrical device, which must both be met if life is to be supported. These requirements exhibit discrete (non-zero) minima whose magnitude is set by the biochemistry in question, and they are increased in quantifiable fashion by (i) deviations from biochemically optimal physical and chemical conditions and (ii) energy-expending solutions to problems of resource limitation. The possible rate of energy transduction is constrained by (i) the availability of usable free energy sources in the environment, (ii) limitations on transport of those sources into the cell, (iii) upper limits on the rate at which energy can be stored, transported, and subsequently liberated by biochemical mechanisms (e.g., enzyme saturation effects), and (iv) upper limits imposed by an inability to use "power" and "voltage" at levels that cause material breakdown. A system is habitable when the realized rate of energy transduction equals or exceeds the biological demand for energy. For systems in which water availability is considered a key aspect of habitability (e.g., Mars), the energy balance construct imposes additional, quantitative constraints that may help to prioritize targets in search-for-life missions. Because the biological need for energy is universal, the energy balance construct also helps to constrain habitability in systems (e.g., those envisioned to use solvents other than water) for which little constraint currently exists. PMID:18163865

  14. Augmenting simplified habit reversal in the treatment of oral-digital habits exhibited by individuals with mental retardation.

    PubMed

    Long, E S; Miltenberger, R G; Ellingson, S A; Ott, S M

    1999-01-01

    We investigated whether a simplified habit reversal treatment eliminates fingernail biting and related oral-digital habits exhibited by individuals with mild to moderate mental retardation. Although simplified habit reversal did little to decrease the target behaviors for 3 of 4 participants, simplified habit reversal plus additional treatment procedures decreased the behavior to near-zero levels for all participants. These procedures included remote prompting, remote contingencies involving differential reinforcement plus response cost, and differential reinforcement of nail growth. Limitations of habit reversal for individuals with mental retardation along with directions for future research involving therapist-mediated treatment procedures, particularly those involving remote prompting and remote contingencies, are discussed. PMID:10513029

  15. Habitability in Different Milky Way Stellar Environments: A Stellar Interaction Dynamical Approach

    PubMed Central

    Pichardo, Bárbara; Lake, George; Segura, Antígona

    2013-01-01

    Abstract Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the solar neighborhood, however, is rather poor; thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of stars in more crowded stellar environments, such as stellar clusters. We found that in open clusters habitable zones are not readily disrupted; this is true if they evaporate in less than 108 yr. For older clusters the results may not be the same. We specifically studied the case of Messier 67, one of the oldest open clusters known, and show the effect of this environment on debris disks. We also considered the conditions in globular clusters, the Galactic nucleus, and the Galactic bulge-bar. We calculated the probability of whether Oort clouds exist in these Galactic environments. Key Words: Stellar interactions—Galactic habitable zone—Oort cloud. Astrobiology 13, 491–509. PMID:23659647

  16. The quantitative modelling of human spatial habitability

    NASA Technical Reports Server (NTRS)

    Wise, James A.

    1988-01-01

    A theoretical model for evaluating human spatial habitability (HuSH) in the proposed U.S. Space Station is developed. Optimizing the fitness of the space station environment for human occupancy will help reduce environmental stress due to long-term isolation and confinement in its small habitable volume. The development of tools that operationalize the behavioral bases of spatial volume for visual kinesthetic, and social logic considerations is suggested. This report further calls for systematic scientific investigations of how much real and how much perceived volume people need in order to function normally and with minimal stress in space-based settings. The theoretical model presented in this report can be applied to any size or shape interior, at any scale of consideration, for the Space Station as a whole to an individual enclosure or work station. Using as a point of departure the Isovist model developed by Dr. Michael Benedikt of the U. of Texas, the report suggests that spatial habitability can become as amenable to careful assessment as engineering and life support concerns.

  17. Using Drained Spacecraft Propellant Tanks for Habitation

    NASA Technical Reports Server (NTRS)

    Thomas, Andrew S. W.

    2009-01-01

    A document proposes that future spacecraft for planetary and space exploration be designed to enable reuse of drained propellant tanks for occupancy by humans. This proposal would enable utilization of volume and mass that would otherwise be unavailable and, in some cases, discarded. Such utilization could enable reductions in cost, initial launch mass, and number of launches needed to build up a habitable outpost in orbit about, or on the surface of, a planet or moon. According to the proposal, the large propellant tanks of a spacecraft would be configured to enable crews to gain access to their interiors. The spacecraft would incorporate hatchways, between a tank and the crew volume, that would remain sealed while the tank contained propellant and could be opened after the tank was purged by venting to outer space and then refilled with air. The interior of the tank would be pre-fitted with some habitation fixtures that were compatible with the propellant environment. Electrical feed-throughs, used originally for gauging propellants, could be reused to supply electric power to equipment installed in the newly occupied space. After a small amount of work, the tank would be ready for long-term use as a habitation module.

  18. Study of television viewing habits in children.

    PubMed

    Mukherjee, Sharmila Banerjee; Gupta, Yogita; Aneja, Satinder

    2014-11-01

    Previous studies from developing countries have reported that Television (TV) viewing, if excessive and of poor quality has a proven negative influence on child health. Indian studies on this subject are few. The present study aimed at determining TV viewing habits of children and their families as well as parental perspectives on the impact of TV on child health using a provider completed indigenously developed questionnaire in Hindi. The study group comprised of 109 children attending a government hospital who belonged predominantly to lower socio-economic strata with poor maternal literacy. It was observed that 100 % children watched excessive TV (> 2 h daily), with majority viewing unsupervised and low quality content. There were minimal parental restrictions and no active discussion regarding contents. Negative impact was found on play, hobbies, sleep hygiene and eating habits in most children. Most parents were unaware of unhealthy viewing and the associated deleterious effects. As pediatricians we need to enquire about TV viewing habits routinely and educate parents about appropriate TV viewing. PMID:24682808

  19. Resolving the Circumstellar Disk of HL Tauri at Millimeter Wavelengths

    E-print Network

    Kwon, Woojin; Mundy, Lee G

    2011-01-01

    We present results of high-resolution imaging toward HL Tau by the Combined Array for Research in Millimeter-wave Astronomy (CARMA). We have obtained 1.3 and 2.7 mm dust continua with an angular resolution down to 0.13 arc second. Through model fitting to the two wavelength data simultaneously in Bayesian inference using a flared viscous accretion disk model, we estimate the physical properties of HL Tau, such as density distribution, dust opacity spectral index, disk mass, disk size, inclination angle, position angle, and disk thickness. HL Tau has a circumstellar disk mass of 0.13 solar mass, a characteristic radius of 79 AU, an inclination of 40 degree, and a position angle of 136 degree. Although a thin disk model is preferred by our two wavelength data, a thick disk model is needed to explain the high mid- and far-infrared emission of the HL Tau spectral energy distribution. This could imply large dust grains settled down on the mid plane with fine dust grains mixed with gas. The HL Tau disk is likely gr...

  20. RESOLVING THE CIRCUMSTELLAR DISK OF HL TAURI AT MILLIMETER WAVELENGTHS

    SciTech Connect

    Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Mundy, Lee G., E-mail: wkwon@illinois.edu [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

    2011-11-01

    We present results of high-resolution imaging toward HL Tau by the Combined Array for Research in Millimeter-wave Astronomy. We have obtained {lambda} = 1.3 mm and 2.7 mm dust continua with an angular resolution down to 0.''13. Through simultaneous model fitting to the two wavelength data sets in Bayesian inference using a flared viscous accretion disk model, we estimate the physical properties of HL Tau, such as density distribution, dust opacity spectral index, disk mass, disk size, inclination angle, position angle, and disk thickness. HL Tau has a circumstellar disk mass of 0.13 M{sub sun}, a characteristic radius of 79 AU, an inclination of 40{sup 0}, and a position angle of 136{sup 0}. Although a thin disk model is preferred by our two wavelength data sets, a thick disk model is needed to explain the high mid- and far-infrared emission of the HL Tau spectral energy distribution. This could imply large dust grains settled down on the midplane with fine dust grains mixed with gas. The HL Tau disk is likely gravitationally unstable and can be fragmented between 50 and 100 AU of radius. However, we did not detect dust thermal continuum supporting the protoplanet candidate claimed by a previous study using observations of the Very Large Array at {lambda} = 1.3 cm.

  1. A Survey for Circumstellar Disks Around Young Substellar Objects

    E-print Network

    Michael C. Liu; Joan Najita; Alan T. Tokunaga

    2002-11-02

    (Abridged) We have completed the first systematic survey for disks around spectroscopically identified young brown dwarfs and very low mass stars. We have obtained L'-band (3.8 um) imaging for 38 very cool objects in IC 348 and Taurus. Our targets span spectral types from M6 to M9.5 (~100 to ~15 Mjup). Using the objects' measured spectral types and extinctions, we find that most of our sample (77%+/-15%) possess intrinsic IR excesses, indicative of disks. Because the excesses are modest, conventional analyses using only IR colors would have missed most of the sources with excesses. The observed IR excesses are correlated with Halpha emission, consistent with a common accretion disk origin. The excesses can be explained by disk reprocessing of starlight alone; the implied accretion rates are at least an order of magnitude below typical values for classical T Tauri stars. The observed distribution of IR excesses suggests the presence of inner disk holes. The disk frequency appears to be independent of the mass and age. In the same star-forming regions, disks around brown dwarfs are at least as long-lived (~3 Myr) as disks around the T Tauri stars. Altogether, the frequency and properties of young circumstellar disks appear to be similar from the stellar regime down to the substellar and planetary-mass regime. This provides prima facie evidence of a common origin for most stars and brown dwarfs.

  2. Rapid disappearance of a warm, dusty circumstellar disk.

    PubMed

    Melis, Carl; Zuckerman, B; Rhee, Joseph H; Song, Inseok; Murphy, Simon J; Bessell, Michael S

    2012-07-01

    Stars form with gaseous and dusty circumstellar envelopes, which rapidly settle into disks that eventually give rise to planetary systems. Understanding the process by which these disks evolve is paramount in developing an accurate theory of planet formation that can account for the variety of planetary systems discovered so far. The formation of Earth-like planets through collisional accumulation of rocky objects within a disk has mainly been explored in theoretical and computational work in which post-collision ejecta evolution typically is ignored, although recent work has considered the fate of such material. Here we report observations of a young, Sun-like star (TYC?8241?2652?1) where infrared flux from post-collisional ejecta has decreased drastically, by a factor of about 30, over a period of less than two years. The star seems to have gone from hosting substantial quantities of dusty ejecta, in a region analogous to where the rocky planets orbit in the Solar System, to retaining at most a meagre amount of cooler dust. Such a phase of rapid ejecta evolution has not been previously predicted or observed, and no currently available physical model satisfactorily explains the observations. PMID:22763553

  3. Numerical models for the circumstellar medium around Betelgeuse

    E-print Network

    Mackey, Jonathan; Neilson, Hilding R; Langer, Norbert; Meyer, Dominique M -A

    2013-01-01

    The nearby red supergiant (RSG) Betelgeuse has a complex circumstellar medium out to at least 0.5 parsecs from its surface, shaped by its mass-loss history within the past 0.1 Myr, its environment, and its motion through the interstellar medium (ISM). In principle its mass-loss history can be constrained by comparing hydrodynamic models with observations. Observations and numerical simulations indicate that Betelgeuse has a very young bow shock, hence the star may have only recently become a RSG. To test this possibility we calculated a stellar evolution model for a single star with properties consistent with Betelgeuse. We incorporated the resulting evolving stellar wind into 2D hydrodynamic simulations to model a runaway blue supergiant (BSG) undergoing the transition to a RSG near the end of its life. The collapsing BSG wind bubble induces a bow shock-shaped inner shell which at least superficially resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow...

  4. Episodic Mass Loss and Pre-SN Circumstellar Envelopes

    E-print Network

    Nathan Smith

    2008-02-13

    I discuss observational clues concerning episodic mass-loss properties of massive stars in the time before the final supernova explosion. In particular, I will focus on the mounting evidence that LBVs and related stars are candidates for supernova progenitors, even though current paradigms place them at the end of core-H burning. Namely, conditions in the immediate circumstellar environment within a few 10$^2$ AU of Type IIn supernovae require very high progenitor mass-loss rates. Those rates are so high that the only known stars that come close are LBVs during rare giant eruptions. I will highlight evidence from observations of some recent extraordinary supernovae suggesting that explosive or episodic mass loss (a.k.a. LBV eruptions like the 19th century eruption of Eta Car) occur in the 5-10 years immediately preceding the SN. Finally, I will discuss some implications for stellar evolution from these SNe, the most important of which is the observational fact that the most massive stars can indeed make it to the ends of their lives with substantial H envelopes intact, even at Solar metallicity.

  5. Molecular catastrophes and circumstellar SiO masers

    NASA Technical Reports Server (NTRS)

    Stencel, Robert E.

    1993-01-01

    Understanding the complex SiO maser regions of highly evolved stars can be improved through multiwavelength studies of 'premaser' stars, such as M0-M4 giants and semiregular variables, which can be placed on normal H-R diagrams unlike most of the OH-IR stars. I argue that SiO masers are a key part of the transformation of hot stellar plasma into cold circumstellar silicate dust, in the outflows from evolved, oxygen rich stars. Evidence for this statement rests on the following: (1) red giant mass loss originates in a stochastic, amsotropic manner; (2) SiO maser maps of Miras and red supergiants show numerous maser spots within a few stellar radii; (3) molecules and dust naturally form in a cooling outflow; (4) the IRAS Low Resolution Spectrometer provided evidence for diverse and variable 10 micron silicate features in Miras, and these shapes correlate well with the proposed maser chronology, suggesting a formation and annealing sequence. The theory for the occurrence of SiO masers involving thermal instability, related 'new' physics, recent calculations and a prediction are discussed.

  6. The Longevity of Circumstellar Disks: The ? Chamaeleontis Cluster

    NASA Astrophysics Data System (ADS)

    Lyo, A.-Ran; Lawson, W. A.

    2005-06-01

    We have analysed near-infrared JHKL observations of the members of the ?9 Myr-old ? Chamaeleontis cluster. Using (J-H)/(K-L) and (H-K)/(K-L) IR colour-colour diagrams for the brightest 15 members of the cluster, we find the fraction of stellar systems with near-IR excess emission was 0.60 ± 0.13 (2?). For the CTT and WTT star population, we also find a strong correlation between the IR excess and H? emission which is also known as an accretion indicator. The (K-L) excess of these stars appears to indicate a wide range of star-disk activity; from a CTT star with high levels of accretion, to CTT,WTT transitional objects with evidence for some on-going accretion, and WTT stars with weak or absent IR excesses. Among the brightest 15 members, four stars (RECX 5, 9, 11 and ECHA J0843.3-7905) with IR excesses ?(K-L) > 0.4 mag and strong or variable optical emission were identified as likely experiencing on-going mass accretion from their circumstellar disks which we confirmed their accretion disks from the optical high-resolution echelle spectroscopic study. The resulting accretion fraction of 0.27 ± 0.13 (2?) suggests that the accretion phase, in addition to the disks themselves, can endure for at least ˜ 10 Myr.

  7. On circumstellar disks: Spitzer identifies two possible evolutionary paths

    NASA Astrophysics Data System (ADS)

    Teixeira, Paula S.; Lada, Charles J.; Marengo, Massimo; Lada, Elizabeth

    Multi-wavelength surveys have vastly improved our understanding of many astrophysical objects, in particular, circumstellar disks. We present our results for the disk population of the young cluster NGC 2264. Our study was based on data obtained with the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer on board the Spitzer Space Telescope combined with previously published optical data. We divide the disk population into 3 classes based on their spectral energy distribution shapes: optically thick disks, homologously depleted anemic disks, and radially depleted transition disks. We find that there are two distinct evolutionary paths for disks: a homologous one, where the disk emission decreases uniformly in NIR and mid-infrared wavelengths (anemic disks) and throughout which most sources pass, and a radially differential one where the emission from the inner region of the disk decreases more rapidly than from the outer region (transition disks). Whether a disk evolves in a homologously or radially depleted fashion is still unknown and may depend on the nature of planet formation in the disk.

  8. Light echo detection of circumstellar disks around flaring stars

    NASA Technical Reports Server (NTRS)

    Gaidos, Eric J.

    1994-01-01

    Light echoes can be used to detect and characterize disks around flaring stars. Such disks are thought to be a hallmark of planet formation but are very difficult to detect by ordinary means. Dwarf emission-line M stars experience flares with luminosities comparable to their quiescent photospheres on time scales of minutes, less than the light travel time across a disk many astronomical units in extent; they are thus ideal candidates for such a search. Bromley (1992) calculated that the detection of Jupiter-sized companions using light echoes requires photometric accuracies better than 1 part in 10(exp 6). However, a disk consisting of grains or small bodies will scatter a much larger fraction of the light than a planet of similar mass. I estimate the light echo amplitutdes from plausible geometries of circumstellar material and present simulation light curves. The light echo amplitudes are typically 1% of the flare and I conclude that such events will be detected best in cases where the flare is eclipsed by the star. An examination of the time scales associated with internal processes in a protoplanetary disks around dM stars indicates that any primordial disks may become undetectable in 10(exp 4) years and will have completely disappeared by 10(exp 8) years, the estimated age of dMe stars in the solar neighborhood. However, searches for light echoes might constrain the amount of material continuing to fall into these young stellar systems in the form of comet-like objects.

  9. Alignment of Protostars and Circumstellar Disks during the Embedded Phase

    NASA Astrophysics Data System (ADS)

    Spalding, Christopher; Batygin, Konstantin; Adams, Fred C.

    2014-12-01

    Star formation proceeds via the collapse of a molecular cloud core over multiple dynamical timescales. Turbulence within cores results in a spatially non-uniform angular momentum of the cloud, causing a stochastic variation in the orientation of the disk forming from the collapsing material. In the absence of star-disk angular momentum coupling, such disk-tilting would provide a natural mechanism for the production of primordial spin-orbit misalignments in the resulting planetary systems. However, owing to high accretion rates in the embedded phase of star formation, the inner edge of the circumstellar disk extends down to the stellar surface, resulting in efficient gravitational and accretional angular momentum transfer between the star and the disk. Here, we demonstrate that the resulting gravitational coupling is sufficient to suppress any significant star-disk misalignment, with accretion playing a secondary role. The joint tilting of the star-disk system leads to a stochastic wandering of star-aligned bipolar outflows. Such wandering widens the effective opening angle of stellar outflows, allowing for more efficient clearing of the remainder of the protostar's gaseous envelope. Accordingly, the processes described in this work provide an additional mechanism responsible for sculpting the stellar initial mass function.

  10. ON THE EXCITATION AND FORMATION OF CIRCUMSTELLAR FULLERENES

    SciTech Connect

    Bernard-Salas, J.; Jones, A. P. [Institut d'Astrophysique Spatiale, CNRS/Universite Paris-Sud 11, F-91405 Orsay (France); Cami, J.; Peeters, E.; Micelotta, E. R. [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Groenewegen, M. A. T., E-mail: jbernard@ias.u-psud.fr [Royal Observatory of Belgium, Ringlaan 3, B-1180 Brussels (Belgium)

    2012-09-20

    We compare and analyze the Spitzer mid-infrared spectrum of three fullerene-rich planetary nebulae in the Milky Way and the Magellanic Clouds: Tc1, SMP SMC 16, and SMP LMC 56. The three planetary nebulae share many spectroscopic similarities. The strongest circumstellar emission bands correspond to the infrared active vibrational modes of the fullerene species C{sub 60} and little or no emission is present from polycyclic aromatic hydrocarbons. The strengths of the fullerene bands in the three planetary nebulae are very similar, while the ratios of the [Ne III]15.5 {mu}m/[Ne II]12.8 {mu}m fine structure lines, an indicator of the strength of the radiation field, are markedly different. This raises questions about their excitation mechanism and we compare the fullerene emission to fluorescent and thermal models. In addition, the spectra show other interesting and common features, most notably in the 6-9 {mu}m region, where a broad plateau with substructure dominates the emission. These features have previously been associated with mixtures of aromatic/aliphatic hydrocarbon solids. We hypothesize on the origin of this band, which is likely related to the fullerene formation mechanism, and compare it with modeled hydrogenated amorphous carbon that present emission in this region.

  11. The formation and structure of circumstellar and interstellar dust

    NASA Technical Reports Server (NTRS)

    Kroto, H. W.

    1990-01-01

    The intriguing abundance of long linear carbon chain molecules in some dark clouds and in circumstellar shells is still not well understood. Recent laboratory studies which have probed this problem indicate that when carbon vapor nucleates to form particles, linear chains and hollow cage molecules (fullerenes) also form at more-or-less the same time. The results have consequences for the formation, structures and spectroscopic properties of the molecular and dust components ejected from cool carbon-rich stars. A most interesting result of the experimental observations relates to the probability that a third character in addition to the chains and grains, the C(sub 60) molecule probably in the form of the ion C(sub 60)(sup +) in the less shielded regions, is present and perhaps responsible for some of the ubiquitously observed interstellar spectroscopic features such as the Diffuse Interstellar Features, the 2170A UV Absorption or perhaps some of the Unidentified Infrared Bands. Further study of small carbon particles which form in the gas phase has resulted in the discovery that they have quasi-icosahedral spiral shell structures. The role that such species may play in the interstellar medium as well as that played by C(sub 60) (or C sub 60 sup +) should soon be accessible to verification by a combination of laboratory experiment and astronomical spectroscopy.

  12. Chemical composition of the circumstellar disk around AB Aurigae

    E-print Network

    Pacheco-Vázquez, S; Agúndez, M; Pinte, C; Alonso-Albi, T; Neri, R; Cernicharo, J; Goicoechea, J R; Berné, O; Wiesenfeld, L; Bachiller, R; Lefloch, B

    2015-01-01

    Aims. Our goal is to determine the molecular composition of the circumstellar disk around AB Aurigae (hereafter, AB Aur). AB Aur is a prototypical Herbig Ae star and the understanding of its disk chemistry is of paramount importance to understand the chemical evolution of the gas in warm disks. Methods. We used the IRAM 30-m telescope to perform a sensitive search for molecular lines in AB Aur as part of the IRAM Large program ASAI (A Chemical Survey of Sun-like Star-forming Regions). These data were complemented with interferometric observations of the HCO+ 1-0 and C17O 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI). Single-dish and interferometric data were used to constrain chemical models. Results. Throughout the survey, several lines of CO and its isotopologues, HCO+, H2CO, HCN, CN and CS, were detected. In addition, we detected the SO 54-33 and 56-45 lines, confirming the previous tentative detection. Comparing to other T Tauri's and Herbig Ae disks, AB Aur presents low HCN 3-2/HCO+ 3-2 ...

  13. Studying Prokaryotic Communities in Iron Depositing Hot Springs (IDHS): Implication for Early Mars Habitability

    NASA Technical Reports Server (NTRS)

    Sarkisova, S. A.; Tringe, S. G.; Thomas-Keprta, K. L.; Allen, C. c.; Garrison, D. H.; McKay, David S.; Brown, I. I.

    2010-01-01

    We speculate that both external and intracellular iron precipitate in iron-tolerant CB might be involved in oxidative stress suppression shown by [9]. Significant differences are apparent between a set of proteins involved in the maintenance of Fe homeostasis and oxidative stress protection in iron-tolerant and fresh-water and marine CB. Correspondingly, these properties may help to make iron-tolerant CB as dominant organisms in IDHS and probably on early Earth and Mars. Further comparative analyses of hot springs metagenomes and the genomes of iron-tolerant microbes versus fresh-water/marine ones may point out to different habitable zones on early Mars.

  14. Origin and Stability of Exomoon Atmospheres - Implications for Habitability

    E-print Network

    Lammer, H; Juvan, I; Odert, P; Erkaev, N V; Weber, C; Kislyakova, K G; Güdel, M; Kirchengast, G; Hanslmeier, A

    2015-01-01

    We study the origin and escape of catastrophically outgassed volatiles (H$_2$O, CO$_2$) from exomoons with Earth-like densities and masses of $0.1M_{\\oplus}$, $0.5M_{\\oplus}$ and $1M_{\\oplus}$ orbiting an extra-solar gas giant inside the habitable zone of a young active solar-like star. We apply a radiation absorption and hydrodynamic upper atmosphere model to the three studied exomoon cases. We model the escape of hydrogen and dragged dissociation products O and C during the activity saturation phase of the young host star. Because the soft X-ray and EUV radiation of the young host star may be up to $\\sim$100 times higher compared to today's solar value during the first 100 Myr after the system's origin, an exomoon with a mass $ 0.5M_{\\oplus}$, however, may evolve to habitats that are a mixture of Mars-like and Earth-analogue habitats, so that life may originate and evolve at the exomoon's surface.

  15. Circumstellar Dust around AGB Stars and Implications for Infrared Emission from Galaxies

    NASA Astrophysics Data System (ADS)

    Villaume, Alexa; Conroy, Charlie; Johnson, Benjamin D.

    2015-06-01

    Stellar population synthesis (SPS) models are used to infer many galactic properties including star formation histories, metallicities, and stellar and dust masses. However, most SPS models neglect the effect of circumstellar dust shells around evolved stars and it is unclear to what extent they impact the analysis of spectral energy distributions (SEDs). To overcome this shortcoming we have created a new set of circumstellar dust models, using the radiative transfer code DUSTY, for asymptotic giant branch (AGB) stars and incorporated them into the Flexible Stellar Population Synthesis code. The circumstellar dust models provide a good fit to individual AGB stars as well as the IR color–magnitude diagrams of the Large and Small Magellanic Clouds. IR luminosity functions from the Large and Small Magellanic Clouds are not well-fit by the 2008 Padova isochrones when coupled to our circumstellar dust models and so we adjusted the lifetimes of AGB stars in the models to provide a match to the data. We show, in agreement with previous work, that circumstellar dust from AGB stars can make a significant contribution to the IR (? 4 ? m) emission from galaxies that contain relatively little diffuse dust, including low-metallicity and/or non-star-forming galaxies. Our models provide a good fit to the mid-IR spectra of early-type galaxies. Circumstellar dust around AGB stars appears to have a small effect on the IR SEDs of metal-rich star-forming galaxies (i.e., when AV ? 0.1). Stellar population models that include circumstellar dust will be needed to accurately interpret data from the James Webb Space Telescope and other IR facilities.

  16. Habitability in Advanced Space Mission Design. Part 2; Evaluation of Habitation Elements

    NASA Technical Reports Server (NTRS)

    Adams, Constance M.; McCurdy, Matthew R.

    2000-01-01

    Habitability is a fundamental component of any long-duration human habitat. Due to the pressures on the crew and the criticality of their performance, this is particularly true of habitats or vehicles proposed for use in any human space mission of duration over 30 days. This paper, the second of three on this subject, will focus on evaluating all the vehicles currently under consideration for the Mars Design Reference Mission through application of metrics for habitability (proposed in a previous paper, see references Adams/McCurdy 1999).

  17. Noise zoning around airports in the Netherlands

    NASA Astrophysics Data System (ADS)

    Evers, F. W. R.

    1980-01-01

    The situation in the Netherlands with respect to noise abatement is dominated by a steadily increasing activity both at the political and the administrative level. A new law with respect to the designation of noise zones around existing and future airports and military airfields was enacted on 1 October 1978. A comprehensive new noise nuisance act was signed by the Queen on 16 February 1979. Both laws were accepted by Parliament unanimously. This article describes the new regulations with respect to noise zoning around airports. To maintain the habitability of the environment around airports, a demarcation will be made between the interest of the people living there and those of aviation. A noise zone will be designated outside which the noise load from aircraft movements may not exceed a fixed maximum. Within this area, where a noise load above the fixed maximum is allowed, planning and building design measures will have to be taken. Although the exclusion of new housing within the noise zone is an essential element, the area will be used for other purposes by exchanging previously intended developments with those from areas outside the zone. The Minister in charge of physical planning will issue directives concerning the contents of local development plans and will indicate how such plans, once amended, should be put into effect. Termination of the use or habitation of existing buildings is possible as well as soundproofing of buildings. The costs of measures taken to prevent undesirable new developments and measures taken to improve the existing state of affairs are borne by the central government. But a charge has to be paid by the users of the airports to defray the costs.

  18. Ultraviolet radiation from F and K stars and implications for planetary habitability

    NASA Technical Reports Server (NTRS)

    Kasting, J. F.; Whittet, D. C.; Sheldon, W. R.

    1997-01-01

    Now that extrasolar planets have been found, it is timely to ask whether some of them might be suitable for life. Climatic constraints on planetary habitability indicate that a reasonably wide habitable zone exists around main sequence stars with spectral types in the early-F to mid-K range. However, it has not been demonstrated that planets orbiting such stars would be habitable when biologically-damaging energetic radiation is also considered. The large amounts of UV radiation emitted by early-type stars have been suggested to pose a problem for evolving life in their vicinity. But one might also argue that the real problem lies with late-type stars, which emit proportionally less radiation at the short wavelengths (lambda < 200 nm) required to split O2 and initiate ozone formation. We show here that neither of these concerns is necessarily fatal to the evolution of advanced life: Earth-like planets orbiting F and K stars may well receive less harmful UV radiation at their surfaces than does the Earth itself.

  19. TRAPPIST-UCDTS: A prototype search for habitable planets transiting ultra-cool stars

    NASA Astrophysics Data System (ADS)

    Gillon, M.; Jehin, E.; Fumel, A.; Magain, P.; Queloz, D.

    2013-04-01

    The ˜1000 nearest ultra-cool stars (spectral type M6 and latter) represent a unique opportunity for the search for life outside solar system. Due to their small luminosity, their habitable zone is 30-100 times closer than for the Sun, the corresponding orbital periods ranging from one to a few days. Thanks to this proximity, the transits of a habitable planet are much more probable and frequent than for an Earth-Sun analog, while their tiny size (˜1 Jupiter radius) leads to transits deep enough for a ground-based detection, even for sub-Earth size planets. Furthermore, a habitable planet transiting one of these nearby ultra-cool star would be amenable for a thorough atmospheric characterization, including the detection of possible biosignatures, notably with the near-to-come JWST. Motivated by these reasons, we have set up the concept of a ground-based survey optimized for detecting planets of Earth-size and below transiting the nearest Southern ultra-cool stars. To assess thoroughly the actual potential of this future survey, we are currently conducting a prototype mini-survey using the TRAPPIST robotic 60cm telescope located at La Silla ESO Observatory (Chile). We summarize here the preliminary results of this mini-survey that fully validate our concept.

  20. Circumstellar medium around rotating massive stars at solar metallicity

    NASA Astrophysics Data System (ADS)

    Georgy, Cyril; Walder, Rolf; Folini, Doris; Bykov, Andrei; Marcowith, Alexandre; Favre, Jean M.

    2013-11-01

    Aims: Observations show nebulae around some massive stars but not around others. If observed, their chemical composition is far from homogeneous. Our goal is to put these observational features into the context of the evolution of massive stars and their circumstellar medium (CSM) and, more generally, to quantify the role of massive stars for the chemical and dynamical evolution of the ISM. Methods: Using the A-MAZE code, we perform 2d-axisymmetric hydrodynamical simulations of the evolution of the CSM, shaped by stellar winds, for a whole grid of massive stellar models from 15 to 120 M? and following the stellar evolution from the zero-age main-sequence to the time of supernova explosion. In addition to the usual quantities, we also follow five chemical species: H, He, C, N, and O. Results: We show how various quantities evolve as a function of time: size of the bubble, position of the wind termination shock, chemical composition of the bubble, etc. The chemical composition of the bubble changes considerably compared to the initial composition, particularly during the red-supergiant (RSG) and Wolf-Rayet (WR) phases. In some extreme cases, the inner region of the bubble can be completely depleted in hydrogen and nitrogen, and is mainly composed of carbon, helium, and oxygen. We argue why the bubble typically expands at a lower rate than predicted by self-similarity theory. In particular, the size of the bubble is very sensitive to the density of the ISM, decreasing by a factor of ~2.5 for each additional dex in ISM density. The bubble size also decreases with the metallicity of the central star, because low-metallicity stars have weaker winds. Our models qualitatively fit the observations of WR ejecta nebulae.

  1. STELLAR AND CIRCUMSTELLAR PROPERTIES OF CLASS I PROTOSTARS

    SciTech Connect

    Prato, L.; Lockhart, K. E. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Johns-Krull, Christopher M. [Department of Physics and Astronomy, Rice University, MS-108, 6100 Main Street, Houston, TX 77005 (United States); Rayner, John T. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)], E-mail: lprato@lowell.edu, E-mail: k.e.lockhart@gmail.com, E-mail: cmj@rice.edu, E-mail: rayner@ifa.hawaii.edu

    2009-04-15

    We present a study of the stellar and circumstellar properties of Class I sources using low-resolution (R {approx} 1000) near-infrared (near-IR) K- and L-band spectroscopy. We measure prominent spectral lines and features in eight objects and use fits to standard star spectra to determine spectral types, visual extinctions, K-band excesses, and water ice optical depths. Four of the seven systems studied are close binary pairs; only one of these systems, Haro 6-10, was angularly resolvable. For certain stars, some properties found in our analysis differ substantially from published values; we analyze the origin of these differences. We determine extinction to each source using three different methods and compare and discuss the resulting values. One hypothesis that we were testing, that extinction dominates over the K-band excess in obscuration of the stellar photospheric absorption lines, appears not to be true. Accretion luminosities and mass accretion rates calculated for our targets are highly uncertain, in part the result of our inexact knowledge of extinction. For the six targets we were able to place on a Hertzsprung-Russell diagram, our age estimates, <2 Myr, are somewhat younger than those from comparable studies. Our results underscore the value of low-resolution spectroscopy in the study of protostars and their environments; however, the optimal approach to the study of Class I sources likely involves a combination of high- and low-resolution near-IR, mid-IR, and millimeter wavelength observations. Accurate and precise measurements of extinction in Class I protostars will be key to improving our understanding of these objects.

  2. Stellar and Circumstellar Properties of Class I Protostars

    NASA Astrophysics Data System (ADS)

    Prato, L.; Lockhart, K. E.; Johns-Krull, Christopher M.; Rayner, John T.

    2009-04-01

    We present a study of the stellar and circumstellar properties of Class I sources using low-resolution (R ~ 1000) near-infrared (near-IR) K- and L-band spectroscopy. We measure prominent spectral lines and features in eight objects and use fits to standard star spectra to determine spectral types, visual extinctions, K-band excesses, and water ice optical depths. Four of the seven systems studied are close binary pairs; only one of these systems, Haro 6-10, was angularly resolvable. For certain stars, some properties found in our analysis differ substantially from published values; we analyze the origin of these differences. We determine extinction to each source using three different methods and compare and discuss the resulting values. One hypothesis that we were testing, that extinction dominates over the K-band excess in obscuration of the stellar photospheric absorption lines, appears not to be true. Accretion luminosities and mass accretion rates calculated for our targets are highly uncertain, in part the result of our inexact knowledge of extinction. For the six targets we were able to place on a Hertzsprung-Russell diagram, our age estimates, <2 Myr, are somewhat younger than those from comparable studies. Our results underscore the value of low-resolution spectroscopy in the study of protostars and their environments; however, the optimal approach to the study of Class I sources likely involves a combination of high- and low-resolution near-IR, mid-IR, and millimeter wavelength observations. Accurate and precise measurements of extinction in Class I protostars will be key to improving our understanding of these objects.

  3. Doppler tomography of the circumstellar disk of ? Aquarii

    NASA Astrophysics Data System (ADS)

    Zharikov, S. V.; Miroshnichenko, A. S.; Pollmann, E.; Danford, S.; Bjorkman, K. S.; Morrison, N. D.; Favaro, A.; Guarro Fló, J.; Terry, J. N.; Desnoux, V.; Garrel, T.; Martineau, G.; Buchet, Y.; Ubaud, S.; Mauclaire, B.; Kalbermatten, H.; Buil, C.; Sawicki, C. J.; Blank, T.; Garde, O.

    2013-12-01

    Aims: The work is aimed at studying the circumstellar disk of the bright classical binary Be star ? Aqr. Methods: We analysed variations of a double-peaked profile of the H? emission line in the spectrum of ? Aqr that was observed in many phases during ~40 orbital cycles in 2004-2013. We applied the discrete Fourier transform (DFT) method to search for periodicity in the peak intensity ratio (V/R). Doppler tomography was used to study the structure of the disk around the primary. Results: The dominant frequency in the power spectrum of the H? V/R ratio is 0.011873 day-1, which corresponds to a period of 84.2(2) days and agrees with the earlier determined orbital period of the system, Porb = 84.1 days. The V/R shows a sinusoidal variation that is phase-locked with the orbital period. Doppler maps of all our spectra show a non-uniform structure of the disk around the primary: a ring with the inner and outer radii at Vin ? 450 km s-1 and Vout ? 200 km s-1, respectively, along with an extended stable region (spot) at Vx ? 225 km s-1 and Vy ? 100 km s-1. The disk radius of ?65 R? = 0.33 AU was estimated by assuming Keplerian motion of a particle on a circular orbit at the disk's outer edge. Table 1 and ? Aquarii spectra in FITS format 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/560/A30 http://www.astrosurf.com/aras/

  4. Investigations of the Formation of Carbon Grains in Circumstellar Outflows

    NASA Technical Reports Server (NTRS)

    Contreras, Cesar; Salama, Farid

    2013-01-01

    The study of formation and destruction processes of cosmic dust is essential to understand and to quantify the budget of extraterrestrial organic molecules. Although dust with all its components plays an important role in the evolution of interstellar chemistry and in the formation of organic molecules, little is known on the formation and destruction processes of carbonaceous dust. PAHs are important chemical building blocks of interstellar dust. They are detected in interplanetary dust particles and in meteoritic samples. Additionally, observational, laboratory, and theoretical studies have shown that PAHs, in their neutral and ionized forms, are an important, ubiquitous component of the interstellar medium. Also, the formation of PAHs from smaller molecules has not been extensively studied. Therefore, it is imperative that laboratory experiments be conducted to study the dynamic processes of carbon grain formation from PAH precursors. Studies of interstellar dust analogs formed from a variety of PAH and hydrocarbon precursors as well as species that include the atoms O, N, and S, have recently been performed in our laboratory under conditions that simulate interstellar and circumstellar environments. The species formed in the pulsed discharge nozzle (PDN) plasma source are detected and characterized with a high-sensitivity cavity ringdown spectrometer (CRDS) coupled to a Reflectron time-of-flight mass spectrometer (ReTOF-MS), thus providing both spectroscopic and ion mass information in-situ. We report the first set of measurements obtained in these experiments and identify the species present in the experiments and the ions that are formed in the plasma process. From these unique measurements, we derive information on the size and the structure of interstellar dust grain particles, the growth and the destruction processes of interstellar dust and the resulting budget of extraterrestrial organic molecules.

  5. Thermal desorption of circumstellar and cometary ice analogs

    NASA Astrophysics Data System (ADS)

    Martín-Doménech, R.; Muñoz Caro, G. M.; Bueno, J.; Goesmann, F.

    2014-04-01

    Context. Thermal annealing of interstellar ices takes place in several stages of star formation. Knowledge of this process comes from a combination of astronomical observations and laboratory simulations under astrophysically relevant conditions. Aims: For the first time we present the results of temperature programmed desorption (TPD) experiments with pre-cometary ice analogs composed of up to five molecular components: H2O, CO, CO2, CH3OH, and NH3. Methods: The experiments were performed with an ultra-high vacuum chamber. A gas line with a novel design allows the controlled preparation of mixtures with up to five molecular components. Volatiles desorbing to the gas phase were monitored using a quadrupole mass spectrometer, while changes in the ice structure and composition were studied by means of infrared spectroscopy. Results: The TPD curves of water ice containing CO, CO2, CH3OH, and NH3 present desorption peaks at temperatures near those observed in pure ice experiments, volcano desorption peaks after water ice crystallization, and co-desorption peaks with water. Desorption peaks of CH3OH and NH3 at temperatures similar to the pure ices takes place when their abundance relative to water is above ~3% in the ice matrix. We found that CO, CO2, and NH3 also present co-desorption peaks with CH3OH, which cannot be reproduced in experiments with binary water-rich ice mixtures. These are extensively used in the study of thermal desorption of interstellar ices. Conclusions: These results reproduce the heating of circumstellar ices in hot cores and can be also applied to the late thermal evolution of comets. In particular, TPD curves represent a benchmark for the analysis of the measurements that mass spectrometers on board the ESA-Rosetta cometary mission will perform on the coma of comet 67P/Churyumov-Gerasimenko, which will be active before the arrival of Rosetta according to our predictions.

  6. Observations of Circumstellar Material Around Evolved Stars With the ISI

    NASA Technical Reports Server (NTRS)

    Danchi, W. C.; Hale, D. S.; Monnier, J. D.; Tuthill, P. G.; Weiner, J.; Townes, C. H.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    The U.C. Berkeley Infrared Spatial Interferometer (ISI) is a stellar interferometer operating in the 9-12 micron region and has been in operation from 1988 until the present. It utilizes heterodyne detection using CO2 laser local oscillators and currently includes two 1.65 m movable telescopes mounted in semi-trailers and baselines up to about 65 m in length. A third telescope is being integrated with the other two and within the next year will operate as an imaging interferometer providing data with three simultaneous baselines and a closure phase, and baselines up to about 75 m. During the past twelve years the ISI has been used extensively for studies of circumstellar material around evolved stars. Multi-epoch observations of a sample of prototypical sources have elucidated the location and time scales for dust formation around these stars. These time scales can be as short as approx.10 years for Mira stars and as long as approx. 100 years for supergiants. For stars like Mira itself there is evidence for departure from spherical symmetry and episodes of dust formation and destruction. For some stars motion of dust has been observed -- IK Tau is one example, and NML Cyg is another. The molecules Silane and Ammonia were observed for the extreme carbon star IRC +10216 and the supergiant VY CMa pinpointing their location relative to the inner radius of the dust shell. Somewhat surprisingly, these molecules were found to form many stellar radii away from the inner radius of the dust shell, implying that they form by interactions with the surfaces of dust grains. Last year observations with the longest baselines lead to new precision diameters of $o$ Ceti and $\\alpha$ Orionis, and are continuing on a somewhat larger set of Mira variable and supergiant stars.

  7. Dynamics of Supernova Remnants with Ejecta and Circumstellar Bubbles

    NASA Astrophysics Data System (ADS)

    Blondin, M. J.; Featherstone, N.; Borkowski, J. K.; Reynolds, P. S.

    2001-09-01

    Progenitors of core-collapse supernovae (SNe) blow bubbles in the ambient medium and sweep it into shells with their powerful stellar winds. After the explosion, SN ejecta initially collide with the stellar wind, then with the wind-blown bubble, and finally with a dense wind-swept shell. This collision is particularly energetic for SNe whose progenitors lost most of their outer envelopes just prior to explosion: the brightest galactic supernova remnant (SNR), Cas A, is a prime example of such an interaction with the circumstellar medium (CSM). The SN ejecta are far from being smooth for such remnants, because of vigorous turbulence and mixing of heavy-element ejecta immediately after the explosion and subsequent growth of Ni-Fe bubbles powered by the radioactive decay. We study the interaction of ``bubbly'' SN ejecta with a CSM bubble and a swept CSM shell, using hydrodynamical simulations in 2 and 3 dimensions with the VH-1 hydrocode. We compare our simulations with analytic self-similar (Chevalier & Liang 1989) solutions and with our previous simulations of interaction of bubbly ejecta with a uniform ambient medium. When compared with these simulations, the impact of bubbly ejecta with the shell results in a more vigorous turbulence and mixing. Dense and cool ejecta at the boundaries of adjacent bubbles may penetrate the shell, leading to plume-like and ring-like features. We examine whether such an interaction is responsible for the observed morphology of Cas A as seen by the Chandra X-ray Observatory and the Hubble Space Telescope, and for the different expansion rates seen at X-ray and radio wavelengths.

  8. A statistical analysis of circumstellar material in Type Ia supernovae

    NASA Astrophysics Data System (ADS)

    Maguire, K.; Sullivan, M.; Patat, F.; Gal-Yam, A.; Hook, I. M.; Dhawan, S.; Howell, D. A.; Mazzali, P.; Nugent, P. E.; Pan, Y.-C.; Podsiadlowski, P.; Simon, J. D.; Sternberg, A.; Valenti, S.; Baltay, C.; Bersier, D.; Blagorodnova, N.; Chen, T.-W.; Ellman, N.; Feindt, U.; Förster, F.; Fraser, M.; González-Gaitán, S.; Graham, M. L.; Gutiérrez, C.; Hachinger, S.; Hadjiyska, E.; Inserra, C.; Knapic, C.; Laher, R. R.; Leloudas, G.; Margheim, S.; McKinnon, R.; Molinaro, M.; Morrell, N.; Ofek, E. O.; Rabinowitz, D.; Rest, A.; Sand, D.; Smareglia, R.; Smartt, S. J.; Taddia, F.; Walker, E. S.; Walton, N. A.; Young, D. R.

    2013-11-01

    A key tracer of the elusive progenitor systems of Type Ia supernovae (SNe Ia) is the detection of narrow blueshifted time-varying Na I D absorption lines, interpreted as evidence of circumstellar material surrounding the progenitor system. The origin of this material is controversial, but the simplest explanation is that it results from previous mass-loss in a system containing a white dwarf and a non-degenerate companion star. We present new single-epoch intermediate-resolution spectra of 17 low-redshift SNe Ia taken with XShooter on the European Southern Observatory Very Large Telescope. Combining this sample with events from the literature, we confirm an excess (˜20 per cent) of SNe Ia displaying blueshifted narrow Na I D absorption features compared to redshifted Na I D features. The host galaxies of SNe Ia displaying blueshifted absorption profiles are skewed towards later-type galaxies, compared to SNe Ia that show no Na I D absorption and SNe Ia displaying blueshifted narrow Na I D absorption features have broader light curves. The strength of the Na I D absorption is stronger in SNe Ia displaying blueshifted Na I D absorption features than those without blueshifted features, and the strength of the blueshifted Na I D is correlated with the B - V colour of the SN at maximum light. This strongly suggests the absorbing material is local to the SN. In the context of the progenitor systems of SNe Ia, we discuss the significance of these findings and other recent observational evidence on the nature of SN Ia progenitors. We present a summary that suggests that there are at least two distinct populations of normal, cosmologically useful SNe Ia.

  9. Evidence of circumstellar matter surrounding the Hercules X-1 system

    NASA Astrophysics Data System (ADS)

    Choi, C. S.; Dotani, T.; Nagase, F.; Makino, F.; Deeter, J. E.; Min, K. W.

    1994-05-01

    We analyze data from two eclipse ingresses of Her X-1 observed with Ginga on 1989 April 30 and May 19. These observations occur, respectively, during the MAIN HIGH and SHORT HIGH states in the 35 day modulation of Her X-1 intensity. We find significant residual X-ray flux during eclipse, with a gradual decrease in flux following the occultation of the neutron star by the atmosphere of HZ Her. During the central part of the eclipse the count rate becomes nearly constant, at 0.5 mCrab in the energy range 1.7-36.8 keV. From a spectral analysis of the residual emission during the total eclipse of the central source in the MAIN HIGH state, we determine the energy spectral index, alpha = 0.8, similar to that before eclipse. A remarkable feature of the eclipse spectrum is that it does not show a significant iron line feature in contrast to massive wind-fed pulsars, such as Vela X-1 and Cen X-3. From a timing analysis of the same eclipse data, we show that there are no pulses. These results imply that the emission comes from the scattering of continuum X-rays by material in a region considerably larger than the companion star. An extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona may be responsible for this scattering. However, partial eclipse of an extended accretion disk corona is insufficient to account for the count rates in mid-eclipse, when known parameters of the binary system are used. Based on the present results, we suggest that scattering occurs not only in the accretion disk corona but also in the circumstellar matter surrounding the system of Her X-1/HZ Her.

  10. Subsurface Controls on Habitability of Hydrothermal Waters

    NASA Astrophysics Data System (ADS)

    Fristad, K. E.; Som, S. M.; Hoehler, T. M.

    2014-12-01

    Liquid water alone does not make an environment habitable. Environmental settings dominated by water-rock reactions such as in hydrothermal vents and springs are natural targets for astrobiological investigation of waterworlds because the rich geochemical diversity at these locales provides abundant energy in solvent to support microbial life. Hydrogen oxidizers are of particular interest because H2-based metabolisms are widespread and deeply rooted throughout the phylogenetic tree of life, implying they may have emerged extremely early in the evolution, and possibly even the origin, of life on Earth and potentially any other rocky bodies bearing liquid water. Dihydrogen (H2) can be lithogenically produced by the hydrolytic oxidation of the ferrous iron component in Fe-bearing minerals as well as by radiolytic cleavage of water by ?, ?, or ? radiation produced during the decay of radioactive isotopes. Lithogenic H2 production mechanisms operate across a range of rock types, but the concentration of dissolved H2 available to life is controlled by a number of subsurface factors such as surface geometry, water to rock ratio, production rate, and fluid flux. These factors are often controlled by the larger geologic and structural context of a particular site. We present results of an ongoing project that surveys H2 concentrations from terrestrial hydrothermal waters in diverse chemical and physical settings. Aqueous H2 concentrations and potential subsurface controls are presented for sites across the western U.S. including Yellowstone National Park, Lassen Volcanic National Park, and Iceland. In coordination with field data, we also investigate the habitability of various sites numerically by coupling a geochemical model of water-rock interaction with that of single-cell methanogenesis and compute a habitability index for the given environment. In particular, we investigate the control that temperature, rock composition, water composition, and water to rock ratio (dilution) has on biological potential.

  11. Obesity and exercise habits of asthmatic patients

    PubMed Central

    Westermann, Heidi; Choi, Tiffany N.; Briggs, William M.; Charlson, Mary E.; Mancuso, Carol A.

    2008-01-01

    Background National guidelines recommend 20 to 30 minutes of exercise 3 to 5 days a week. However, achieving these goals may be challenging for asthmatic patients whose symptoms are exacerbated by exercise. Objective To describe relationships among exercise habits, weight, and asthma severity and control in adults with asthma. Methods Self-reported exercise habits were obtained from 258 stable patients by using the Paffenbarger Physical Activity and Exercise Index. Disease status was measured by using the Asthma Control Questionnaire and the Severity of Asthma Scale. Exercise habits were evaluated in multivariate analyses with age, sex, education, body mass index, and asthma control and severity as independent variables. Results The mean patient age was 42 years; 75% were women, 62% were college graduates, and 40% were obese. Only 44% of patients did any exercise. In bivariate analysis, patients with well-controlled asthma were more likely to exercise; however, in multivariate analysis, asthma control and severity were not associated but male sex (P = .01), having more education (P = .04), and not being obese (P ? .001) were associated. Asthma control and severity also were not associated with type, duration, or frequency of exercise, but not being obese was associated in multivariate analyses. Only 22% of all patients (49% of those who exercised) met national guidelines for weekly exercise. Not being obese was the only variable associated with meeting guidelines in multivariate analysis (P = .02). Conclusions Compared with the general population, a lower proportion of asthmatic patients did any routine exercise and met national exercise guidelines. Physicians need to manage asthma and obesity to help asthmatic patients meet exercise goals. PMID:19055202

  12. Superluminous X-ray emission from the interaction of supernova ejecta with dense circumstellar shells

    NASA Astrophysics Data System (ADS)

    Pan, Tony; Patnaude, Daniel; Loeb, Abraham

    2013-07-01

    For supernova (SN) powered by the conversion of kinetic energy into radiation due to the interactions of the ejecta with a dense circumstellar shell, we show that there could be X-ray analogues of optically superluminous SNe with comparable luminosities and energetics. We consider X-ray emission from the forward shock of SN ejecta colliding into an optically thin circumstellar material (CSM) shell, derive simple expressions for the X-ray luminosity as a function of the circumstellar shell characteristics, and discuss the different regimes in which the shock will be radiative or adiabatic, and whether the emission will be dominated by free-free radiation or line cooling. We find that even with normal SN explosion energies of 1051 erg, there exist CSM shell configurations that can liberate a large fraction of the explosion energy in X-rays, producing unabsorbed X-ray luminosities approaching 1044 erg s-1 events lasting a few months, or even 1045 erg s-1 flashes lasting days. Although the large column density of the circumstellar shell can absorb most of the flux from the initial shock, the most luminous events produce hard X-rays that are less susceptible to photoelectric absorption, and can counteract such losses by completely ionizing the intervening material. Regardless, once the shock traverses the entire circumstellar shell, the full luminosity could be available to observers.

  13. The Circumstellar Imager: Direct detection of extra-solar planetary systems

    NASA Technical Reports Server (NTRS)

    Ftaclas, Christ; Nonnenmacher, Andreas L.; Terrile, Richard J.; Pravdo, Steven H.; Gatewood, George D.; Levy, Eugene

    1994-01-01

    The Astrometric Imaging Telescope (AIT) is designed to probe the circumstellar environment by both direct imaging and indirect astrometric measurements. The Circumstellar Imager (CI) is a coronagraphic camera and is the direct imaging component of the AIT. The CI is designed to obtain high-sensitivity images of the circumstellar region. It provides crucial non-inferential information relating to the frequency, origin, and evolution of planetary systems and all forms of circumstellar matter. Such imaging is usually limited by the scattered and diffracted light halos of the star itself, which are greatly suppressed in the CI by mating a novel high-efficiency coronagraph with a phase-compensated optical system. For faint point sources in the circumstellar region, the CI will have a sensitivity in excess of 5 magnitudes fainter than the as-designed Hubble Space Telescope (HST). Laboratory data are shown for the coronagraph, which, in a diffraction-limited environment, is capable of suppressing the stellar diffraction sidelobes by several orders of magnitude without significant sacrifice of field of view. In order to realize the high rejection levels inherent in the coronagraph design, it is necessary to limit scatter in the optical systems, imposing a mid-spatial frequency figure error requirement an order of magnitude smaller than that of the HST. Experimental data directed toward meeting this requirement are also shown.

  14. Habit Formation: Implications for Alcoholism Research

    PubMed Central

    O’Tousa, David; Grahame, Nicholas

    2014-01-01

    Characteristics of individuals with severe alcohol use disorders include heightened cue sensitivity, compulsive seeking, craving, and continued alcohol use in the face of negative consequences. Animal models are useful for understanding behavioral and neurological mechanisms underlying problematic alcohol use. Seeking of operant reinforcers including alcohol is processed by two mechanisms, commonly referred to as “goal-directed” (action-outcome) and “habitual” (stimulus-response). As substance use disorders are characterized by continued use regardless of unfavorable outcomes, it is plausible that drug use causes an unnatural disruption of these mechanisms. We present a critical analysis of literature pertaining to behavioral neuroscience alcoholism research involving habit formation. Traditionally, when operant behavior is unaffected by a loss of subjective value of a reinforcer (devaluation), the behavior is considered habitual. Acquisition of instrumental behavior requires corticostriatal mechanisms that depend heavily on the prefrontal cortex and ventral striatum, whereas practiced behavior is more predominantly controlled by the dorsal striatum. Dopaminergic signaling is necessary for the neurological adaptations involved in stimulus-response action, and drugs of abuse appear to facilitate habitual behavior through high levels of dopamine release. Evidence suggests that the use of alcohol as a reinforcer expedites habit formation, and that a history of alcohol use produces alterations in striatal morphology, aids habit learning for non-psychoactive reinforcers, and promotes alcohol drinking despite aversive adulterants. In this review, we suggest directions for future alcoholism research that seeks to measure action made despite a devalued outcome, including procedural modifications and genotypic, pharmacological, or neurological manipulations. Most alcoholism models currently in use fail to reach substantial blood ethanol concentrations, a shortcoming that may be alleviated through the use of high-drinking rodent lines. Additionally, satiety, one common mechanism of devaluing reinforcers, is not recommended for alcohol research because the psychoactive effects of alcohol depress response rates, mimicking devaluation effects. Overall, further research of habit formation and potentially related perseverative behaviors could be invaluable in discovering genetic variance, traits that correlate with persistent alcohol seeking, implicated neural structures and processes of alcohol use, and eventually novel pharmacological treatment for alcoholism. PMID:24835007

  15. America's Eating Habits: Changes and Consequences

    NSDL National Science Digital Library

    1999-01-01

    This new book from the US Department of Agriculture Economic Research Service, USDA ERS (last noted in the May 7, 1999 Scout Report) offers a comprehensive review of eating habits and the state of nutrition in America. Downloadable by chapter or in its entirety in .pdf format, the book presents a multi-disciplinary perspective on nutrition issues, addressing topics ranging from "dietary guidelines to food consumption patterns, from the impact of food advertising to the economic costs of unhealthy diets." Other subjects covered include the impact of government programs and regulations, public and private efforts to encourage healthy eating, and the connections between dietary changes and US agriculture.

  16. Dietary Habits of Greek Primary School Children

    NASA Astrophysics Data System (ADS)

    Piperakis, S. M.; Papadimitriou, V.; Zafiropoulou, M.; Piperakis, A. S.; Zisis, P.

    2007-06-01

    The purpose of this study was to assess Greek primary (1st to 6th grade) school children's dietary habits and the factors influencing them. Our results show that children know the value of different foods. The socio-economic status of father has no effect on the attitude of children towards choosing their diet, however, mothers' educational status appears to have an effect on their children's behaviour. Place of residence (urban or semi-rural areas) and gender does not influence their knowledge about different diets. It was, finally, shown that as children grow older they tend to eat less healthy foods.

  17. Family meal traditions. Comparing reported childhood food habits to current food habits among university students.

    PubMed

    De Backer, Charlotte J S

    2013-10-01

    The aim of this study is to investigate if reported childhood food habits predict the food habits of students at present. Questions addressed are: does the memory of childhood family meals promote commensality among students? Does the memory of (grand)parents' cooking influence students' cooking? And, is there still a gender difference in passing on everyday cooking skills? Using a cross-sectional survey, 104 students were asked about their current eating and cooking habits, and their eating habits and the cooking behavior of their (grand)parents during their childhood. Results show that frequencies in reported childhood family meals predict frequencies of students' commensality at present. The effects appear for breakfast and dinner, and stay within the same meal: recalled childhood family breakfasts predict current breakfast commensality, recalled childhood family dinners predict current dinner commensality. In terms of recalled cookery of (grand)parents and the use of family recipes a matrilineal dominance can be observed. Mothers are most influential, and maternal grandmothers outscore paternal grandmothers. Yet, fathers' childhood cooking did not pass unnoticed either. They seem to influence male students' cookery. Overall, in a life-stage of transgression students appear to maintain recalled childhood food rituals. Suggestions are discussed to further validate these results. PMID:23707416

  18. Habitability issues in long duration undersea and space missions

    NASA Technical Reports Server (NTRS)

    Parker, J. F., Jr.; Every, M. G.

    1972-01-01

    The report reviews a number of studies in the area of habitability. Emphasis was placed on extracting from these studies that information most relevant to any long-term mission in confinement. It is concluded that, whereas the basic laws of habitability are known, there is much yet to be learned concerning development of social structures in small groups in relative isolation, planning for necessary hygiene needs, development of proper work spaces, and construction of internal and external communications systems. With respect to testing for habitability and the documentation of habitability principles, the space program was found to be considerably more advanced than was the program for undersea missions.

  19. Habitability and Multistability in Earth-like Planets

    NASA Astrophysics Data System (ADS)

    Lucarini, V.; Pascale, S.; Boschi, R.; Kirk, E.; Iro, N.

    2013-06-01

    In this paper we explore the potential multistability of the climate for a planet around the habitable zone. We focus on conditions reminiscent to those of the Earth system, but our investigation has more general relevance and aims at presenting a general methodology for dealing with exoplanets. We describe a formalism able to provide a thorough analysis of the non-equilibrium thermodynamical properties of the climate system and explore, using a flexible climate model, how such properties depend on the energy input of the parent star, on the infrared atmospheric opacity, and on the rotation rate of the planet. We first show that it is possible to reproduce the multi-stability properties reminiscent of the paleoclimatologically relevant snowball (SB)-warm (W) conditions. We then characterise the thermodynamics of the simulated W and SB states, clarifying the central role of the hydrological cycle in shaping the irreversibility and the efficiency of the W states, and emphasizing the extreme diversity of the SB states, where dry conditions are realized. Thermodynamics provides the clue for studying the tipping points of the system and leads us to constructing empirical parametrizations allowing for expressing the main thermodynamic properties as functions of the emission temperature of the planet only. Such empirical functions are shown to be rather robust with respect to changing the rotation rate of the planet from the current terrestrial one to half of it. Furthermore, we explore the dynamical range where the length of the day and the length of the year are comparable. We clearly find that there is a critical rotation rate below which the multi-stability properties are lost, and the ice-albedo feedback responsible for the presence of SB and W conditions is damped. The bifurcation graph of the system suggests the presence of a phase transition in the planetary system. Such critical rotation rate corresponds roughly to the phase-lock 2:1 condition. Therefore, if an Earth-like planet is 1:1 phase-locked with respect to the parent star, only one climatic state would be compatible with a given set of astronomical and astrophysical parameters. These results have relevance for the general theory of planetary circulation and for the definition of necessary and sufficient conditions for habitability.

  20. Planetary Habitability and Rapid Environmental Change: The Biological Perspective

    NASA Astrophysics Data System (ADS)

    Schulze-Makuch, D.; Fairen, A.; Irwin, L.

    2012-12-01

    Environmental conditions can change drastically and rapidly during the natural history of a planetary body. We have detailed evidence of these dramatic events from Venus, Earth, Mars, and Titan. Most of these occurrences seem to be triggered by astronomical events such as asteroid impacts or supernova explosions; others are triggered by the planet or moon itself (e.g., supervolcano eruptions). The associated question is always how these events affect the habitability of a planet, particularly the origin and presence of life. Under what conditions would such a drastic event be so catastrophic that it would prohibit the origin of life or be so devastating to existing organisms, that life would not be able to recover and be all but extinguished from a planet? Under what conditions would such an event be positive for the evolution of life, for example spurring life via mass extinctions and associated vacant habitats to the invention of new body plans and higher complexity? Here, we provide insights of what we can learn from the natural history of our own planet, which experienced many environmental disasters and abrupt climate changes, from the impact event that created the Moon to the extinction of the dinosaurs. We apply these insights to other planetary bodies and the question about the presence of life. One example is Mars, which underwent drastic environmental changes at the end of the Noachian period. Assuming that microbial life became established on Mars, could it have survived, perhaps by retreating to environmental niches? Life just starting out would have certainly been more vulnerable to extinction. But how far would it have to have evolved to be more resistant to potential extinction events? Would it have to be global in distribution to survive? Another example is Venus. Should Venus be seen as an example where life, which possibly arose in the first few hundred million years when the planet was still in the habitable zone, would have had no chance to survive the upcoming calamities (e.g., the putative meteorite impact that resulted in an opposite spin of the planet, global volcanic eruptions, a run-away greenhouse effect, etc)? Titan may be the most exotic example. Titan may have experienced the transition from a warmer, water-based solvent to a colder, hydrocarbon-based solvent early in its natural history and is still undergoing climate-change cycles. What effects would these transitions have on a possible biosphere? These insights will be also critical for assessing the possibility of life on any "Super-Earth" and other exoplanets, including an assessment of the limits to which life can adapt.

  1. Habitability of Waterworlds: Runaway Greenhouses, Atmospheric Expansion, and Multiple Climate States of Pure Water Atmospheres

    NASA Astrophysics Data System (ADS)

    Goldblatt, Colin

    2015-05-01

    There are four different stable climate states for pure water atmospheres, as might exist on so-called "waterworlds". I map these as a function of solar constant for planets ranging in size from Mars size to 10 Earth-mass. The states are: globally ice covered (Ts< 245K), cold and damp (270 < Ts< 290K), hot and moist (350< Ts< 550K) and very hot and dry (Ts< 900K). No stable climate exists for 290< Ts < 350K or 550 < Ts < 900K. The union of hot moist and cold damp climates describe the liquid water habitable zone, the width and location of which depends on planet mass. At each solar constant, two or three different climate states are stable. This is a consequence of strong non-linearities in both thermal emission and the net absorption of sunlight. Across the range of planet sizes, I account for the atmospheres expanding to high altitudes as they warm. The emitting and absorbing surfaces (optical depth of unity) move to high altitude, making their area larger than the planet surface, so more thermal radiation is emitted and more sunlight absorbed (the former dominates). The atmospheres of small planets expand more due to weaker gravity: the effective runaway greenhouse threshold is about 35Wm-2 higher for Mars, 10Wm-2 higher for Earth or Venus but only a few Wm-2 higher for a 10 Earth-mass planet. There is an underlying (expansion neglected) trend of increasing runaway greenhouse threshold with planetary size (40Wm-2 higher for a 10 Earth-mass planet than for Mars). Summing these opposing trends means that Venus-size (or slightly smaller) planets are most susceptible to a runaway greenhouse. The habitable zone for pure water atmospheres is very narrow, with an insolation range of 0.07 times the solar constant. A wider habitable zone requires background gas and greenhouse gas; N2 and CO2 on Earth, which are biologically controlled. Thus, habitability depends on inhabitance.

  2. Temperate Oceans : Light Zones

    NSDL National Science Digital Library

    2007-12-12

    This reference provides an overview of the three zones into which the ocean can be divided based on the amount of light recieved: the sunlit (or euphotic) zone, the twilight (or disphotic) zone, and the midnight (or aphotic) zone. The descriptions are accompanied by diagrams and a brief listing of the organisms that live in each zone.

  3. How Can We Change Our Habits if We Don't Talk about Them?

    ERIC Educational Resources Information Center

    Mantie, Roger; Talbot, Brent C.

    2015-01-01

    For the late nineteenth century pragmatists, habits were of great interest. Habits, and the habit of changing habits, they believed, reflected if not defined human rationality, leading William James to describe habit as "the enormous fly-wheel of society." What the pragmatists did not adequately address (at least for us) is the role of…

  4. The detection of heavy metals in the circumstellar envelopes of post-AGB stars

    E-print Network

    Klochkova, V G

    2015-01-01

    A new type of peculiarity -- a splitting or asymmetry of strong absorption lines, is found in the optical spectra of selected post-AGB stars with C-rich circumstellar envelopes. The effect is maximal in BaII lines whose profile is split into two-three components. The particular components of the split absorption lines are shown to be formed in a structured circumstellar envelope, suggesting an efficient dredge-up of the heavy metals produced during the preceding evolution of this star into the envelope. We suspect that the splitting (or asymmetry) of the profiles of strongest absorptions with low excitation potential of the low level can be associated with the kinematic and chemical properties of the circumstellar environment and with type of its morphology.

  5. Circumstellar Na I and Ca II lines in type IIP supernovae and SN 1998S

    E-print Network

    N. N. Chugai; V. P. Utrobin

    2008-05-21

    We study a possibility of detection of circumstellar absorption lines of Na I D$_{1,2}$ and Ca II H,K in spectra of type IIP supernovae at the photospheric epoch. The modelling shows that the circumstellar lines of Na I doublet will not be seen in type IIP supernovae for moderate wind density, e.g., characteristic of SN 1999em, whereas rather pronounced Ca II lines with P Cygni profile should be detectable. A similar model is used to describe Na I and Ca II circumstellar lines seen in SN 1998S, type IIL with a dense wind. We show that line intensities in this supernova are reproduced, if one assumes an ultraviolet excess, which is caused primarily by the comptonization of supernova radiation in the shock wave.

  6. Circumstellar discs in Galactic centre clusters: Disc-bearing B-type stars in the Quintuplet and Arches clusters

    E-print Network

    Stolte, Andrea; Olczak, Christoph; Brandner, Wolfgang; Habibi, Maryam; Ghez, Andrea M; Morris, Mark R; Lu, Jessica R; Clarkson, William I; Anderson, Jay

    2015-01-01

    We investigate the circumstellar disc fraction as determined from L-band excess observations of the young, massive Arches and Quintuplet clusters residing in the central molecular zone of the Milky Way. The Quintuplet cluster was searched for L-band excess sources for the first time. We find a total of 26 excess sources in the Quintuplet cluster and 21 in the Arches cluster, of which 13 are new detections. With the aid of proper motion membership samples, the disc fraction of the Quintuplet cluster was derived for the first time to be 4.0 +/- 0.7%. There is no evidence for a radially varying disc fraction in this cluster. In the case of the Arches cluster, a disc fraction of 9.2 +/- 1.2% approximately out to the cluster's predicted tidal radius, r < 1.5 pc, is observed. This excess fraction is consistent with our previously found disc fraction in the cluster in the radial range 0.3 < r < 0.8 pc. In both clusters, the host star mass range covers late A- to early B-type stars, 2 < M < 15 Msun, as...

  7. Polarized Line Profiles as Diagnostics of Circumstellar Geometry in Type IIn Supernovae

    E-print Network

    Jennifer L. Hoffman

    2006-12-10

    Supernovae of type IIn possess spectral signatures that indicate an intense interaction between the supernova ejecta and surrounding dense circumstellar material cast off by the star in pre-explosion mass-loss episodes. Studying this interaction can yield clues to the nature of Type IIn progenitors and their mass loss history. In particular, polarization spectra of Type IIn's show complex line polarization and position angle features that arise from a combination of geometrical and optical effects. I have constructed a Monte Carlo code that simulates the transfer of the H alpha line through circumstellar shells with various geometrical configurations and optical characteristics. The superposition of broad and narrow line components produced in different regions of the circumstellar environment and modified by electron and line scattering, hydrogen absorption, thermal emission, and geometrical and viewing angle effects gives rise to a variety of polarized line shapes in the model spectra. Comparison of these results with recent high-quality spectropolarimetric observations of Type IIn supernovae suggests that a model "shock" region between the supernova photosphere and the circumstellar shell is necessary to produce the narrow polarized emission features at the rest wavelength of H alpha seen in some IIn's. Further model results point toward other features in the polarized line profile that can be used to constrain the characteristics of the circumstellar material in these intriguing objects. The code's usefulness will be extended by the treatment of Doppler effects due to expansion of the circumstellar scattering region, such as those that characterize the polarized H alpha profiles of the Type IIn SN 1997eg.

  8. Direct thermal imaging of circumstellar discs and exo-planets Eric Pantina, Ralf Siebenmorgenb, Celine Cavarroca, Michael F. Sterzikc

    E-print Network

    Liske, Jochen

    Direct thermal imaging of circumstellar discs and exo-planets Eric Pantina, Ralf Siebenmorgenb drivers of METIS are: a) direct thermal imaging of exo­planets and b) characterization of circumstellar window (N band) require a contrast ratio between stellar light and emitted photons from the exo-planet

  9. Nutritional knowledge and dietary habits survey in high school population.

    PubMed

    Milosavljevi?, Dragana; Mandi?, Milena L; Banjari, Ines

    2015-03-01

    During adolescence, young people are in a sensitive transition period when they gradually take over the responsibility for their own eating habits, health attitudes and behaviours and create lifelong habits so it is essential that they adopt healthy habits according to dietary recommendations. Knowledge is one of the factors necessary for the changes in dietary habits. The'objective of this study was to gain insight in nutritional knowledge and dietary habits of adolescents. The sample included 117 adolescents aged 17-19 years. Self-administered, anonymous questionnaire, representing modified version of General Nutrition Knowledge Questionnaire was used to assess general characteristics, nutritional knowledge about nutrients, dietary recommendations, sources of nutrients, diet-disease relationship, and dietary habits. Less than one third of adolescents showed satisfactory knowledge, but boys, adolescents from rural environment and overweight adolescents showed significantly lower knowledge unlike others. Meal skipping was present habit, especially for breakfast consumption. Especially high consumption of meat and meat products was noted for boys, while fruit and vegetables for girls. Fad dieting was quite practiced habit, especially in girls and overweight adolescents. Among girls, high consumption of sweets was confirmed, while boys showed high consumption of soft drinks. Television presents the main source of infor- mation about nutrition for adolescents. Collected data shows similarity with other research in Europe and North America that confirm strong influence of globalization and fast spread of unhealthy habits. The results pointed out weak spots in nutritional knowledge and revealed unhealthy eating habits. This information is necessary for the development of new approaches to modulate their knowledge and consequently act on their behaviour. Behavioral changes would include higher number of meals per day, regular breakfast consumption, higher intake of fish, lower consumption of meat and meat products, sweetened foods and drinks etc. The final outcome would result in longterm positive impact on dietary habits. PMID:26040077

  10. Chemical composition of the circumstellar disk around AB Aurigae

    NASA Astrophysics Data System (ADS)

    Pacheco-Vázquez, S.; Fuente, A.; Agúndez, M.; Pinte, C.; Alonso-Albi, T.; Neri, R.; Cernicharo, J.; Goicoechea, J. R.; Berné, O.; Wiesenfeld, L.; Bachiller, R.; Lefloch, B.

    2015-06-01

    Aims: Our goal is to determine the molecular composition of the circumstellar disk around AB Aurigae (hereafter, AB Aur). AB Aur is a prototypical Herbig Ae star and the understanding of its disk chemistry is paramount for understanding the chemical evolution of the gas in warm disks. Methods: We used the IRAM 30-m telescope to perform a sensitive search for molecular lines in AB Aur as part of the IRAM Large program ASAI (a chemical survey of Sun-like star-forming regions). These data were complemented with interferometric observations of the HCO+ 1?0 and C17O 1?0 lines using the IRAM Plateau de Bure Interferometer (PdBI). Single-dish and interferometric data were used to constrain chemical models. Results: Throughout the survey, several lines of CO and its isotopologues, HCO+, H2CO, HCN, CN, and CS, were detected. In addition, we detected the SO 54?33 and 56?45 lines, confirming the previously tentative detection. Compared to other T Tauri and Herbig Ae disks, AB Aur presents low HCN 3?2/HCO+ 3?2 and CN 2?1/HCN 3?2 line intensity ratios, similar to other transition disks. AB Aur is the only protoplanetary disk detected in SO thus far, and its detection is consistent with interpretation of this disk being younger than those associated with T Tauri stars. Conclusions: We modeled the line profiles using a chemical model and a radiative transfer 3D code. Our model assumes a flared disk in hydrostatic equilibrium. The best agreement with observations was obtained for a disk with a mass of 0.01 M?, Rin = 110 AU, Rout = 550 AU, a surface density radial index of 1.5, and an inclination of 27°. The intensities and line profiles were reproduced within a factor of ˜2 for most lines. This agreement is reasonable considering the simplicity of our model that neglects any structure within the disk. However, the HCN 3?2 and CN 2?1 line intensities were predicted to be more intense by a factor of >10. We discuss several scenarios to explain this discrepancy. Appendix A is available in electronic form at http://www.aanda.org

  11. Asymmetric Circumstellar Matter in Type Ia Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Borkowski, Kazimierz J.; Reynolds, S. P.; Blondin, J. M.

    2013-01-01

    The progenitors of Type Ia supernovae (SNe) are not well understood, but are likely to be of diverse origin, including single- and double-degenerate binary systems. Among single-degenerate progenitors, substantial amounts of circumstellar material (CSM) are expelled prior to the SN explosions by asymptotic giant branch (AGB) companions to the accreting white dwarfs. A subsequent collision of SN ejecta with the dense AGB wind has been detected among several distant SNe such as SN 2002ic, SN 2008J, and more recently PTF11kx. Dense CSM ejected by an AGB companion is present in the remnant of Kepler's SN of 1604, a Type Ia event. Observations of distant SNe hint at strongly asymmetric CSM distributions. A recent study of the CSM in Kepler's SNR by Burkey et al. indicates a large (factor of 10) density contrast between the dense, disk-like equatorial outflow and the more tenuous AGB wind above the orbital plane. A significant fraction of mature Type Ia SNRs in the Large Magellanic Cloud (LMC) shows the presence of dense Fe-rich ejecta in their interiors that cannot be explained by standard models of Type Ia explosions in a uniform ambient interstellar medium. We explore the hypothesis that these remnants originated in Type Ia explosions with strongly asymmetric CSM distributions such as found in Kepler's SNR. We present results of 2-D hydrodynamical simulations of the interaction of SN ejecta with asymmetric, disk-like AGB winds throughout the whole adiabatic stage of SNR evolution. Dense, asymmetric, and highly-ionized Fe-rich ejecta are indeed present in the simulated remnants, while the blast wave assumes a spherical shape shortly after passage through the ambient CSM. We also present simulated X-ray images and spectra and compare them with X-ray observations of selected remnants in the LMC. These remnants include DEM L238 and L249, recently observed by Suzaku, whose X-ray emission is strongly dominated by dense Fe-rich ejecta in their interiors. We contrast these remnants to more typical mature Type Ia SNRs such as 0534-69.9 and 0548-70.4 whose Suzaku spectra can be satisfactorily modeled with standard (without any CSM) X-ray models for Type Ia SNRs.

  12. The light curve and changes in the circumstellar envelope around IRC + 10216

    NASA Technical Reports Server (NTRS)

    Dyck, H. M.; Benson, J. A.; Howell, R. R.; Joyce, R. R.; Leinert, CH.

    1991-01-01

    This paper presents results of NIR photometric observations of IRC + 10216 star during the time interval 1965-1990, which were combined with measurements of the circumstellar shell surrounding IRC + 10216 by IR speckle interferometry. Using these data together with published observations, a very precise light curve was constructed, demonstrating the occurrence of long-term changes in the circumstellar shell surrounding IRC + 10216. The observations are discussed in the framework of two alternatives: (1) the occurrence of dynamical changes in the shell and (2) blocking of the direct light from the star to a portion of the shell by intervening material.

  13. Photoevaporation of Circumstellar Disks Due to External Far-Ultraviolet Radiation in Stellar Aggregates

    Microsoft Academic Search

    Fred C. Adams; David Hollenbach; Gregory Laughlin; Uma Gorti

    2004-01-01

    When stars form within small groups (with N*~100-500 members), their circumstellar disks are exposed to relatively little extreme-ultraviolet (EUV; hnu>13.6 eV) radiation but a great deal of far-ultraviolet (FUV; 6eVcircumstellar disks exposed to

  14. The middle intertidal zone

    NSDL National Science Digital Library

    Katie Hale (California State University, Fullerton; Student, Biological Sciences)

    2007-01-04

    The middle intertidal zone is submerged during high tide and only exposed during low tides. This zone has the most moderate conditions of the zones and has many algae, sea anemones, mollusks, and crustaceans.

  15. The upper intertidal zone

    NSDL National Science Digital Library

    Katie Hale (California State University, Fullerton; Student, Biological Sciences)

    2007-01-04

    The upper intertidal zone is exposed most of the time and will become submerged only during high tide. This zone is least abundant of the intertidal zones but contains some mollusks, barnacles, and other animals adapted to avoid drying out.

  16. The bottom intertidal zone

    NSDL National Science Digital Library

    Katie Hale (California State University, Fullerton; Student, Biological Sciences)

    2007-01-04

    The bottom intertidal area remains under water except during low tides. This zone is most abundant of the intertidal zones and contains seaweeds and other plants, invertebrates, and fishes. The bottom zone is subject to the most intense wave action.

  17. The bottom intertidal zone

    NSDL National Science Digital Library

    Katie Hale (CSUF; Biological Sciences)

    2007-06-08

    The bottom intertidal area remains under water except during low tides. This zone is most abundant of the intertidal zones and contains seaweeds and other plants, invertebrates, and fishes. The bottom zone is subject to the most intense wave action.

  18. The upper intertidal zone

    NSDL National Science Digital Library

    Katie Hale (CSUF; Biological Sciences)

    2007-06-08

    The upper intertidal zone is exposed most of the time and will become submerged only during high tide. This zone is least abundant of the intertidal zones but contains some mollusks, barnacles, and other animals adapted to avoid drying out.

  19. The middle intertidal zone

    NSDL National Science Digital Library

    Katie Hale (CSUF; Biological Sciences)

    2007-06-08

    The middle intertidal zone is submerged during high tide and only exposed during low tides. This zone has the most moderate conditions of the zones and has many algae, sea anemones, mollusks, and crustaceans.

  20. Intergenerational and Urban-Rural Health Habits in Chinese Families

    ERIC Educational Resources Information Center

    Li, Li; Lin, Chunqing; Cao, Haijun; Lieber, Eli

    2009-01-01

    Objective: To explore intergenerational health habits and compare differences between urban and rural families. Methods: A total of 2500 families with children ages 6-18 in China were surveyed regarding their health habits. Results: Urban families reported significantly greater food variety and more time exercising (for fathers and children) than…

  1. Dietary Habits Prone to Lifestyle-Related Disease

    ERIC Educational Resources Information Center

    Nagai, M.; Uyama, O.; Kaji, H.

    2013-01-01

    Objective: To evaluate relations among dietary habits, bone mineral density (BMD), visceral fat area (VFA), and arterial stiffness and recommend better dietary habits. Methods: One hundred and six men and 381 women (aged 18-84) received a health checkup and answered questionnaires, with subsequent measurements of BMD (speed of sound), VFA…

  2. Radiological Habits Survey: Dumfries and Galloway Coast, 2012

    E-print Network

    Radiological Habits Survey: Dumfries and Galloway Coast, 2012 #12;This page has been intentionally left blank #12;Environment Report RL 25/13 Final report Radiological Habits Survey: Dumfries This report should be cited as: Garrod, C.J., Clyne, F.J., Ly, V.E. and Papworth, G.P., 2013. Radiological

  3. 2012 Email Invitation Habits for Healthy Minds & Bodies

    E-print Network

    this unit, we will emphasize balanced strategies for healthy eating, exercising, sleeping, keeping ourselves2012 Email Invitation Habits for Healthy Minds & Bodies As we prepare for our Whole School Unit on HEALTHY MINDS & BODIES, lets discuss how we can help children build healthy habits for a lifetime. CMUs

  4. Skylab Experiment M487 - Habitability/Crew Quarters

    NASA Technical Reports Server (NTRS)

    Johnson, C. C.

    1974-01-01

    It was the purpose of Experiment M487, Habitability/Crew Quarters, to evaluate the effectiveness of the habitability provisions of Skylab for the benefit of designers of future spacecraft. Some of the more interesting findings in the areas of internal environment, architectural arrangements, mobility and restraint aids, food, clothing, personal hygiene, housekeeping, communication between crewmen, and off-duty activities equipment are discussed.

  5. Implications of habit formation for optimal monetary policy

    Microsoft Academic Search

    Jeffery D. Amato; Thomas Laubach

    2002-01-01

    We study the implications for optimal monetary policy of introducing habit formation in consumption into a general equilibrium model with sticky prices. Habit formation affects the model's endogenous dynamics through its effects on both aggregate demand and households' supply of output. We show that the objective of monetary policy consistent with welfare maximisation includes output stablisation, as well as inflation

  6. Circumstellar discs in Galactic centre clusters: Disc-bearing B-type stars in the Quintuplet and Arches clusters

    NASA Astrophysics Data System (ADS)

    Stolte, A.; Hußmann, B.; Olczak, C.; Brandner, W.; Habibi, M.; Ghez, A. M.; Morris, M. R.; Lu, J. R.; Clarkson, W. I.; Anderson, J.

    2015-06-01

    We investigate the circumstellar disc fraction as determined from L-band excess observations of the young, massive Arches and Quintuplet clusters residing in the central molecular zone of the Milky Way. The Quintuplet cluster was searched for L-band excess sources for the first time. We find a total of 26 excess sources in the Quintuplet cluster, and 21 sources with L-band excesses in the Arches cluster, of which 13 are new detections. With the aid of proper motion membership samples, the disc fraction of the Quintuplet cluster could be derived for the first time to be 4.0 ± 0.7%. There is no evidence for a radially varying disc fraction in this cluster. In the case of the Arches cluster, a disc fraction of 9.2 ± 1.2% approximately out to the cluster's predicted tidal radius, r< 1.5 pc, is observed. This excess fraction is consistent with our previously found disc fraction in the cluster in the radial range 0.3 circumstellar discs in these UV intense environments in the context of primordial disc survival and formation scenarios of secondary discs. We consider the possibility that the L-band excess sources in the Arches and Quintuplet clusters could be the high-mass counterparts to T Tauri pre-transitional discs. As such a scenario requires a long pre-transitional disc lifetime in a UV intense environment, we suggest that mass transfer discs in binary systems are a likely formation mechanism for the B-star discs observed in these starburst clusters. Based on data obtained at the ESO VLT under programme IDs 085.D-0446, 089.D-0121 (PI: Stolte), 081.D-0572 (PI: Brandner), 087.D-0720, 089.D-0430 (PI: Olzcak), 071.C-0344 (PI: Eisenhauer), 60.A-9026 (NAOS/CONICA science verification), as well as Hubble Space Telescope observations under programmes 11671 (PI: Ghez).Appendices are available in electronic form at http://www.aanda.orgThe photometric catalogue 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/578/A4

  7. The organism and the habitation atmosphere

    NASA Technical Reports Server (NTRS)

    Agadzhanyan, N. A.

    1978-01-01

    Experimental data is examined on the study of the influence of the different parameters of the atmosphere on the organism for the purpose of making a physiological determination of the permissible oxygen concentrations in inhabited airtight compartments. The application of high oxygen concentrations for respiration and for medical purposes are considered. Data is presented on the evolution of the atmosphere and of the role of O2 in the process of the evolutionary development of living beings; the influence of an organism of an artificial, high and low oxygen concentration atmospheres; the laws of oxygen permeation into fluid media of the organism; the biological role of inert gases; etc. The relationship between the gas medium of habitation and reactivity of the organism is determined.

  8. Did earthquakes keep the early crust habitable?

    PubMed

    Sleep, Norman H; Zoback, Mark D

    2007-12-01

    The shallow habitable region of cratonal crust deforms with a strain rate on the order of approximately 10(19) s(1). This is rapid enough that small seismic events are expected on one-kilometer spatial scales and one-million-year timescales. Rock faulting has the potential to release batches of biological substrate, such as dissolved H(2), permitting transient blooms. In addition, the steady-state deformation of the brittle crust causes numerous small faults to be permeable enough (on the order of approximately 10(15) m(2)) for water to flow on a kilometer scale over relatively short geological times ( approximately 10(5) yr). Hence, active faults act as concentrated niches capable of episodically tapping resources in the bulk volume of the rock. Radiolysis and ferrous iron are potentially bases of sustainable hard-rock niches. PMID:18163876

  9. Mars Habitability, Biosignature Preservation, and Mission Support

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Allen, Carlton C.

    2014-01-01

    Our work has elucidated a new analog for the formation of giant polygons on Mars, involving fluid expulsion in a subaqueous environment. That work is based on three-dimensional (3D) seismic data on Earth that illustrate the mud volcanoes and giant polygons that result from sediment compaction in offshore settings. The description of this process has been published in the journal Icarus, where it will be part of a special volume on Martian analogs. These ideas have been carried further to suggest that giant polygons in the Martian lowlands may be the signature of an ancient ocean and, as such, could mark a region of enhanced habitability. A paper describing this hypothesis has been published in the journal Astrobiology.

  10. A Maximum Radius for Habitable Planets.

    PubMed

    Alibert, Yann

    2015-09-01

    We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope. PMID:26159097

  11. Temperature Variations and Habitability: Activity B Relating Factors that Influence Planetary Temperature and Habitability

    NSDL National Science Digital Library

    In this activity, student teams create a knowledge map of the essential characteristics or factors of a planet with a habitable climate, identifying range of inputs, outputs and variables of a planetary environmental system. Identified characteristics are compared to extreme environments on Earth, such as the Antarctic or the Sahara desert, and are used to consider the real life challenge of searching for life in extreme environments. The resource includes a student data sheet, questions, teacher's guide and scoring rubric. This is Activity B of two activities in the first module, titled "Temperature variations and habitability," of the resource, Earth Climate Course: What Determines a Planet's Climate? The course aims to help students to develop an understanding of our environment as a system of human and natural processes that result in changes that occur over various space and time scales.

  12. Blue Marble: Remote Characterization of Habitable Planets

    NASA Technical Reports Server (NTRS)

    Woolf, Neville; Lewis, Brian; Chartres, James; Genova, Anthony

    2009-01-01

    The study of the nature and distribution of habitable environments beyond the Solar System is a key area for Astrobiology research. At the present time, our Earth is the only habitable planet that can be characterized in the same way that we might characterize planets beyond the Solar System. Due to limitations in our current and near-future technology, it is likely that extra-solar planets will be observed as single-pixel objects. To understand this data, we must develop skills in analyzing and interpreting the radiation obtained from a single pixel. These skills must include the study of the time variation of the radiation, and the range of its photometric, spectroscopic and polarimetric properties. In addition, to understand whether we are properly analyzing the single pixel data, we need to compare it with a ground truth of modest resolution images in key spectral bands. This paper discusses the concept for a mission called Blue Marble that would obtain data of the Earth using a combination of spectropolarimetry, spectrophotometry, and selected band imaging. To obtain imagery of the proper resolution, it is desirable to place the Blue Marble spacecraft no closer than the outer region of cis-lunar space. This paper explores a conceptual mission design that takes advantage of low-cost launchers, bus designs and mission elements to provide a cost effective observing platform located at one of the stable Earth-moon Lagrangian points (L4, L5). The mission design allows for the development and use of novel technologies, such as a spinning moon sensor for attitude control, and leverages lessons-learned from previous low-cost spacecraft such as Lunar Prospector to yield a low-risk mission concept.

  13. Root Apex Transition Zone As Oscillatory Zone

    PubMed Central

    Baluška, František; Mancuso, Stefano

    2013-01-01

    Root apex of higher plants shows very high sensitivity to environmental stimuli. The root cap acts as the most prominent plant sensory organ; sensing diverse physical parameters such as gravity, light, humidity, oxygen, and critical inorganic nutrients. However, the motoric responses to these stimuli are accomplished in the elongation region. This spatial discrepancy was solved when we have discovered and characterized the transition zone which is interpolated between the apical meristem and the subapical elongation zone. Cells of this zone are very active in the cytoskeletal rearrangements, endocytosis and endocytic vesicle recycling, as well as in electric activities. Here we discuss the oscillatory nature of the transition zone which, together with several other features of this zone, suggest that it acts as some kind of command center. In accordance with the early proposal of Charles and Francis Darwin, cells of this root zone receive sensory information from the root cap and instruct the motoric responses of cells in the elongation zone. PMID:24106493

  14. Are persons with nervous habit nervous? A preliminary examination of habit function in a nonreferred population.

    PubMed Central

    Woods, D W; Miltenberger, R G

    1996-01-01

    In this study, 44 individual were exposed to three conditions (anxiety, bored, and neutral) while being covertly videotaped. The videotapes were then scored for the occurrence of five classes of habits including hair, face, and object manipulation; object mouthing; and repetitive movement of the limbs. Results showed that hair and face manipulation increased during the anxiety condition, whereas object manipulation increased in the bored condition. The implications of this research are discussed. PMID:8682744

  15. Investigating Socioscientific Issues via Scientific Habits of Mind: Development and Validation of the Scientific Habits of Mind Survey

    ERIC Educational Resources Information Center

    Calik, Muammer; Coll, Richard Kevin

    2012-01-01

    In this paper, we describe the Scientific Habits of Mind Survey (SHOMS) developed to explore public, science teachers' and scientists' understanding of habits of mind (HoM). The instrument contained 59 items, and captures the seven SHOM identified by Gauld. The SHOM was validated by administration to two cohorts of pre-service science teachers:…

  16. Applying behavior analysis to clinical problems: review and analysis of habit reversal.

    PubMed

    Miltenberger, R G; Fuqua, R W; Woods, D W

    1998-01-01

    This article provides a review and analysis of habit reversal, a multicomponent procedure developed by Azrin and Nunn (1973, 1974) for the treatment of nervous habits, tics, and stuttering. The article starts with a discussion of the behaviors treated with habit reversal, behavioral covariation among habits, and functional analysis and assessment of habits. Research on habit reversal and simplified versions of the procedure is then described. Next the article discusses the limitations of habit reversal and the evidence for its generality. The article concludes with an analysis of the behavioral processes involved in habit reversal and suggestions for future research. PMID:9757583

  17. Refractory metal nuggets within presolar graphite: First condensates from a circumstellar environment

    E-print Network

    Refractory metal nuggets within presolar graphite: First condensates from a circumstellar) Abstract­Transmission electron microscope (TEM) investigations have revealed Os, Ru, Mo-rich refractory that these are direct condensates from the gas, rather than forming later by exsolution. The presolar refractory metal

  18. The compact circumstellar material around OH 231.8+4.2

    E-print Network

    M. Matsuura; O. Chesneau; A. A. Zijlstra; W. Jaffe; L. B. F. M. Waters; J. Yates; E. Lagadec; T. Gledhill; S. Etoka; A. M. S. Richards

    2006-06-23

    We have observed the bipolar post-AGB candidate OH 231.8+4.2, using the mid-infrared interferometer MIDI and the infrared camera with the adaptive optics system NACO on the Very Large Telescope. An unresolved core (<200 mas in FWHM) is found at the center of the OH 231.8+4.2 in the 3.8 micron image. This compact source is resolved with the interferometer. We used two 8-meter telescopes with four different baselines, which cover projected baseline lengths from 62 to 47 meters, and projected position angles from 112 to 131 degrees that are almost perpendicular to the bipolar outflow. Fringes from 8 to 9 micron and from 12 to 13.5 micron were clearly detected, whilst the strong silicate self-absorption allows only marginal detection of visibilities between 9 and 12 micron. The fringes from the four baselines consistently show the presence of a compact circumstellar object with an inner radius of 30-40 mas, which is equivalent to 40-50 AU at 1.3 kpc. This clearly shows that the mid-infrared compact source is not the central star (3 AU) but circumstellar material. The measured size of the circumstellar material is consistent with the size of such disks calculated by hydrodynamic models, implying the circumstellar material may have a disk configuration.

  19. Modelling the H I 21-cm line profile from circumstellar shells around red giants

    NASA Astrophysics Data System (ADS)

    Hoai, D. T.; Nhung, P. T.; Gérard, E.; Matthews, L. D.; Villaver, E.; Le Bertre, T.

    2015-05-01

    We present H I line profiles for various models of circumstellar shells around red giants. In the calculations we take into account the effect of the background at 21 cm, and show that in some circumstances it may have an important effect on the shape and intensity of the observed line profiles. We show that self-absorption should also be considered depending on the mass-loss rate and the temperature reached by circumstellar gas. H I emission from circumstellar shells has been mostly reported from stars with mass-loss rates around 10-7 M? yr-1. We discuss the possible reasons for the non-detection of many sources with larger mass-loss rates that are hallmarks of the end of the asymptotic giant branch (AGB) phase. Although radiative transfer effects may weaken the line emission, they cannot alone account for this effect. Therefore, it seems likely that molecular hydrogen, rather than atomic hydrogen, dominates the composition of matter expelled by stars at the end of their evolution on the AGB. However sensitive H I observations can still yield important information on the kinematics and physical properties of the circumstellar material at large distances from central stars with heavy mass-loss, despite the low abundance of atomic hydrogen.

  20. Probing The Circumstellar Environments Of Be Stars With The Chara Array

    Microsoft Academic Search

    Yamina Touhami; D. R. Gies; G. H. Schaefer; N. D. Richardson; E. D. Grundstrom; G. M. V. Mcswain

    2011-01-01

    We present the first spatially resolved observations of circumstellar envelopes of 25 bright northern Be stars. The survey was performed with the CHARA Array interferometer in the K-band at intermediate and long baselines. The interferometric visibilities are well fitted by a viscous disk model where the gas density steeply decreases with the radius. Physical and geometrical parameters such as the

  1. Circumstellar disk chemistry: 2D UV radiative transfer and effects of stellar UV

    E-print Network

    Zadelhoff, Gerd-Jan van

    Circumstellar disk chemistry: 2D UV radiative transfer and effects of stellar UV G.J. van Zadelhoff interstellar abundances are modified. Photodissociation by UV radiation in the upper layers and freeze radiative transfer for a correct abundance determination If CO can be photodissociated by the stellar UV

  2. The Beta Pictoris circumstellar disk. XV - Highly ionized species near Beta Pictoris

    Microsoft Academic Search

    M. Deleuil; C. Gry; A.-M. Lagrange-Henri; A. Vidal-Madjar; H. Beust; R. Ferlet; H. W. Moos; T. A. Livengood; D. Ziskin; P. D. Feldman

    1993-01-01

    Temporal variations of the Fe II, Mg II, and Al III circumstellar lines towards Beta Pictoris have been detected and monitored since 1985. However, the unusual presence of Al III ions is still puzzling, since the UV stellar flux from an A5V star such as Beta Pic is insufficient to produce such an ion. In order to better define the

  3. Line Forces in Keplerian Circumstellar Disks and Precession of Nearly Circular Orbits

    Microsoft Academic Search

    K. G. Gayley; R. Ignace; S. P. Owocki

    2001-01-01

    We examine the effects of optically thick line forces on orbiting circumstellar disks, such as occur around Be stars. For radially streaming radiation (e.g., as from a point source), line forces are effective only if there is a strong radial velocity gradient, as occurs, for example, in a line-driven stellar wind. However, we emphasize here that, within an orbiting disk,

  4. Water Masers in the Circumstellar Environments of Young Stellar Leb'ee S. G. Meehan

    E-print Network

    Wilking, Bruce A.

    Water Masers in the Circumstellar Environments of Young Stellar Objects Leb'ee S. G. Meehan with known water maser emission: RNO15FIR, Orion A­W, L1157, B361, and L1251A. These objects are cold IRAS their relationship to the water masers and tracers of their stellar winds. Compact radio continuum emission

  5. The Dual-Axis Circumstellar Environment of the Type IIn Supernova 1997eg

    E-print Network

    Jennifer L. Hoffman; Douglas C. Leonard; Ryan Chornock; Alexei V. Filippenko; Aaron J. Barth; Thomas Matheson

    2008-08-10

    We present multi-epoch spectral and spectropolarimetric observations of the Type IIn supernova (SN) 1997eg that indicate the presence of a flattened disk-like concentration of circumstellar material surrounding nonspherical ejecta, with which the disk is misaligned. The polarization across the broad H alpha, H beta, and He I 5876 lines of SN 1997eg forms closed loops when viewed in the Stokes q-u plane. Such loops occur when the geometrical symmetry of one or both of the Stokes parameters across spectral lines is broken, in this case most likely by occultation of the ejecta by the equatorial circumstellar matter concentration. The polarization of the narrow Balmer lines possesses an intrinsic axis that differs by 12 degrees from that of the elongated ejecta and probably indicates the orientation of the disk-like circumstellar material. The existence of two different axes of symmetry in SN 1997eg suggests that neither rotation of the progenitor nor the influence of a companion star can be the sole mechanism creating a preferred axis within the supernova system. Our model supports the emerging hypothesis that the progenitors of some Type IIn supernovae are luminous blue variable stars, whose pre-supernova mass eruptions form the circumstellar shells that physically characterize the SN IIn subclass. These conclusions, which are independent of interstellar polarization effects, would have been unobservable with only a single epoch of spectropolarimetry.

  6. In Search of Future Earths: Assessing the Possibility of Finding Earth Analogues in the Later Stages of Their Habitable Lifetimes

    NASA Astrophysics Data System (ADS)

    O'Malley-James, Jack T.; Greaves, Jane S.; Raven, John A.; Cockell, Charles S.

    2015-05-01

    Earth will become uninhabitable within 2-3 Gyr as a result of the moving boundaries of the habitable zone caused by the increasing luminosity of the Sun. Predictions about the future of habitable conditions on Earth include a decline in species diversity and habitat extent, ocean loss and changes in the magnitudes of geochemical cycles. However, testing these predictions on the present-day Earth is difficult. The discovery of a planet that is a near analogue to the far future Earth could provide a means to test these predictions. Such a planet would need to have an Earth-like biosphere history, requiring it to have been in its system's habitable zone (HZ) for Gyr-long periods during the system's past, and to be approaching the inner-edge of the HZ at present. Here we assess the possibility of finding this very specific type of exoplanet and discuss the benefits of analysing older Earths in terms of improving our understanding of long-term geological and bio-geological processes. As an illustrative example, G stars within 10 parsecs are assessed as potential old-Earth-analogue hosts. Surface temperature estimates for hypothetical inner-HZ Earth analogues are used to determine whether any such planets in these systems would be at the right stage in their late-habitable lifetimes to exhibit detectable biosignatures. Predictions from planet formation studies and biosphere evolution models suggest that only 0.36% of G stars in the solar neighbourhood could host an old-Earth-analogue. However, if the development of an Earth-like biosphere is assumed to be rare, requiring a sequence of low-probability events to occur, then such planets are unlikely to be found in the solar neighbourhood - although 1000s could be present in the galaxy as a whole.

  7. The circumstellar nature of the metallic features in a hot DA white dwarf

    NASA Technical Reports Server (NTRS)

    Holberg, J. B.; Bruhweiler, F. C.; Andersen, J.

    1995-01-01

    A new co-added IUE echelle spectrum of the bright DA white dwarf CD -38 deg 10980, together with a newly determined radial velocity for this star, indicate that the sharp lined Si and C absorption features seen in the UV are clearly circumstellar in origin. Absorption in both excited and ground state transitions occurs at a velocity displaced by -12.1 +/- 2.0 km.s with respect to the photospheric velocity. Weak features due to the Si IV doublet are seen at a velocity intermediate between that of the circumstellar features and the photosphere. First time estimates of column densities for excited and ground states of C II, Si II, and Si III are derived. These quantities are used with electron density estimates derived from these species to determine the location and physical conditions of the circumstellar gas in the vicinity of CD -38 deg 10980. If collisional excitation alone is responsible for the excited levels of Si III observed in CD -38 deg 10980, then electron densities in the circumstellar gas must exceed 10(exp 9)/cu cm. Substantially lower electron densities are possible if the circumstellar gas is located near enough to the star so that photoexcitation is the dominant process responsible for the excited lines seen in the UV. Strong limits are placed on the photospheric abundance of Si and C in the star itself. These limits are in sharp contrast to the theoretical predictions of radiative levitation in which Si, but not C, is expected in the photosphere of a white dwarf such as CD -38 deg 10980. The interstellar line of sight to CD -38 deg 10980 is also investigated.

  8. The Potential Habitability of Dwarf Planet Ceres

    NASA Astrophysics Data System (ADS)

    Li, J.-Y.

    2014-04-01

    As the largest object in the main asteroid belt of the Solar System, Ceres is 940 km in diameter and accounts for ~1/3 of the total mass of the asteroid belt. The recent unequivocal discovery of water vapor associated with localized sources on Ceres by Herschel Space Telescope confirmed enrichment in volatiles in Ceres as suggested by its low density and previous theoretical models. Hence water must have played a significant role in the evolution of Ceres and even affected its current state. Indeed, the shape and size of Ceres measured from Hubble Space Telescope pointed to a differentiated interior with a ~60 km thick outer ice shell. Although no definitive agreement on the compositions of Ceres' surface has been reached, the pervasive signature of hydrated minerals over the surface of Ceres and the albedo and spectral homogeneity across its surface suggest that processes involving liquid-phase activity at the global scale may have occurred in the past. Moreover, the Herschel Space Telescope observations directly pointed us to an active world. The current evolution models of Ceres indicate that liquid water was present following an early differentiation and drove hydrothermal activity for a few tens of My since its formation. Silicate leaching could lead to the concentration of soluble species in the ocean that could play a role in decreasing the freezing temperature of that layer. The likely accretion of low-eutectic species such as ammonia hydrates could have promoted the long-term preservation of a deep liquid layer at the base of an icy shell over extended periods of time (possibly until present). Therefore, models and observations emphasize the importance of Ceres as a potentially habitable object. The Dawn spacecraft is scheduled to arrive at Ceres in March 2015 to perform detailed geological, spectroscopic, compositional, and gravity mapping. In the mean time, we have begun an observing campaign using ground- and space-based facilities that cover wavelengths from UV to sub-mm, aiming to fully characterize the nature of water and hydration features detected at Ceres, and to facilitate theoretical studies. We expect that our knowledge about the history and current status of water on Ceres will be significantly advanced in the coming years, possibly putting Ceres into the category of potentially habitable planets that is by far one of the most accessible to human beings. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

  9. Suffer the little children: fixed intraoral habit appliances for treating childhood thumbsucking habits: a critical review of the literature.

    PubMed

    Moore, Nicholas L

    2002-11-01

    A critical review of the literature is presented covering the treatment of childhood thumbsucking habits using fixed intraoral habit appliances (hayrake, palatal crib). The habit appliances are classified into type and function. Data is tabulated for key references revealing the fragmented and distorted nature of the literature and its lack of consistency. A chronological approach is presented to confirm the confused and idiosyncratic character of the literature. Information is provided on the early work of Massler and Graber and the paradox of Mack, Korner and Reider. Haryett's seminal studies at the University of Alberta regarding aspects of the treatment used are critically reviewed. Reflections are presented on why Larsson's study, casting doubt on the wisdom of using habit appliances, continues to be ignored. The emergence of the Bluegrass Appliance is discussed in terms of its being a more humane appliance and the seeming reluctance of practitioners to apply it as a kinder form of appliance therapy. Information is reported on the pain and serious injuries inflicted on children by habit appliances. A comparison of the use of appliances in the USA is made with the UK, where fixed habit appliances are not popular. Concludes that fixed intraoral habit appliances are cruel and inflict pain and suffering on children out of all proportion to their necessity. Questions why these appliances continue to be used, implying that it could be a combination of financial inducement, professional insularity and the absence of concerted opposition from behavioural therapists. PMID:12572258

  10. Sleep Habits in Mild Cognitive Impairment

    PubMed Central

    Hayes, Tamara L.; Riley, Thomas; Mattek, Nora; Pavel, Misha; Kaye, Jeffrey A.

    2013-01-01

    We explored the relationship between sleep disturbances and mild cognitive impairment (MCI) in community-dwelling seniors. Recent evidence suggests that sleep habits are differentially compromised in different subtypes of MCI, but the relationship between sleep disruption and MCI remains poorly understood. We gathered daily objective measures of sleep disturbance from 45 seniors, including 16 with MCI (mean age 86.9 ± 4.3 years), over a six month period. We also collected self-report measures of sleep disturbance. Although there were no differences between groups in any of our self-report measures, we found that amnestic MCI (aMCI) volunteers had less disturbed sleep than both non-amnestic MCI (naMCI) and cognitively intact volunteers, as measured objectively by movement in bed at night (F2,1078=4.30, p=0.05), wake after sleep onset (F2,1078=41.6, p<0.001), and times up at night (F2,1078=26.7, p<0.001). The groups did not differ in total sleep time. In addition, the aMCI group had less day-to-day variability in these measures than the intact and naMCI volunteers. In general, the naMCI volunteers showed a level of disturbed sleep that was intermediate to that of aMCI and intact volunteers. These differences in sleep disruption between aMCI and naMCI may be related to differences in the pathology underlying these MCI subtypes. PMID:24145694

  11. Follow the plume: the habitability of Enceladus.

    PubMed

    McKay, Christopher P; Anbar, Ariel D; Porco, Carolyn; Tsou, Peter

    2014-04-01

    The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost flyby mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus mission are more advanced than for any other Solar System body. The goals of such a mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved in situ investigations and a sample return. PMID:24684187

  12. The role of dynamics on the habitability of an Earth-like planet

    NASA Astrophysics Data System (ADS)

    Pilat-Lohinger, Elke

    2015-04-01

    From the numerous detected planets outside the Solar System, no terrestrial planet comparable with our Earth has been discovered so far. The search for an Exo-Earth is certainly a big challenge which may require the detections of planetary systems resembling our Solar System in order to find life like on Earth. However, even if we find Solar System analogues, it is not certain that a planet in Earth position will have similar circumstances as those of the Earth. Small changes in the architecture of the giant planets can lead to orbital perturbations which may change the conditions of habitability for a terrestrial planet in the habitable zone (HZ). We present a numerical investigation where we first study the motion of test-planets in a particular Jupiter-Saturn configuration for which we can expect strong gravitational perturbations on the motion at the Earth's position according to a previous work. In this study, we show that these strong perturbations can be reduced significantly by the neighbouring planets of Earth. In the second part of our study, we investigate the motion of test-planets in inclined Jupiter-Saturn systems where we analyse changes in the dynamical behaviour of the inner planetary system. Moderate values of inclination seem to counteract the perturbations in the HZ, while high inclinations induce more chaos in this region. Finally, we carry out a stability study of the actual orbits of Venus, Earth and Mars moving in the inclined Jupiter-Saturn systems for which we used the Solar System parameters. This study shows that the three terrestrial planets will only move in low-eccentric orbits if Saturn's inclination is <=10°. Therefore, it seems that it is advantageous for the habitability of Earth when all planets move nearly in the same plane.

  13. GENERAL INDEX. affinls, Oambusla, habits, morphology. and embryol-

    E-print Network

    to those of other waters. . . . . . . . . . . . . . '46 Embryology, Gambusia affinis 181-190 Embryology.·.·..··.........·....·...····.·...··..·.· " I9J-214 sense of smell, dogfish.....·....···.·...·.............. 63-68 viviparous, Gambusia affinis Gambusia affinis, habits, morphology. and embryology 181-190 heteroclitus, Fundulus

  14. [Habit and control of pests in Santalum album].

    PubMed

    Gao, Zezheng; Wu, Yousheng; Dong, Zhulin; Wu, Weijian

    2004-08-01

    The habit of 5 species pests from South China Botanical Garden was reported in this paper, they are Delias aglaia Linni, Zenzera coffeae Nietner, Parlatoria pergandii Comstock, Scarab (grub), Agrotis ypsilon Rottemberg. Their control methods were presented. PMID:15658811

  15. Habitable Moons and Planets Around Post-Main Sequence Stars

    NASA Astrophysics Data System (ADS)

    Lorenz, R.

    2014-04-01

    Habitability is ephemeral, and arises against the backdrop of stellar evolution. Atmospheric modulation of incoming and outgoing radiative fluxes can restrict or extend the insolation domain in which habitable conditions can persist, and feedbacks (notably, silicate weathering of CO2) may fortuitously adapt that modulation to counteract evolving luminosity. But eventually the star will win. What happens then depends on the histories of stellar luminosity, and of stellar mass loss. While the enhancement of luminosity may render the outer solar system habitable in a classic radiative/convective equilibrium sense, a scenario studied in most detail in connection with Saturn's moon Titan, the enhanced solar wind associated with the latter may strip atmospheres unprotected by magnetic fields. The question of post-main sequence habitability is therefore not a simple one.

  16. Functional Neuroimaging of Avoidance Habits in Obsessive-Compulsive Disorder

    E-print Network

    Gillan, Claire M.; Apergis-Schoute, Annemieke M.; Morein-Zamir, Sharon; Urcelay, Gonzalo P.; Sule, Akeem; Fineberg, Naomi A.; Sahakian, Barbara J.; Robbins, Trevor W.

    Objective: The goal of this study was to determine the neural correlates of excessive habit formation in obsessive-compulsive disorder (OCD). We aimed to (i) test for neurobiological convergence with the known pathophysiology of OCD and (ii) infer...

  17. Reading Habits of Senegalese Adults and College Students.

    ERIC Educational Resources Information Center

    Scales, Alice M.; Burley, JoAnne E.

    1984-01-01

    Discusses factors contributing to high level of illiteracy in Senegal. Reports on study of Senegalese reading habits--participants enjoy reading, read newspapers often, would like to read better, and would take reading improvement courses if they were offered. (CMG)

  18. Reading Habits and Preferences of Secondary School Pupils in Greece.

    ERIC Educational Resources Information Center

    Sikiotis, N.

    1981-01-01

    Presents results of survey conducted to discover the reading habits and preferences of secondary school students in Greece. Results show a high percentage read a newspaper often and the number of books read per month is high. (BK)

  19. The Changing Reading Habits of the American Public.

    ERIC Educational Resources Information Center

    Robinson, John P.

    1980-01-01

    Presents a study of adult reading habits based on time use. Indicates a decline in daily newspaper readership, particularly in the past 10 years, but a revival in magazine and book reading for the same period. (JMF)

  20. Using high-resolution near infrared spectroscopy to probe the interstellar medium and circumstellar disks

    NASA Astrophysics Data System (ADS)

    Brittain, Sean David

    2004-12-01

    High-resolution infrared spectroscopy is a unique tool for probing both the structural and chemical evolution of the interstellar medium and circumstellar disks. We will highlight several examples of how this tool can shed light on chemical processes in the interstellar medium, the formation of planetesimals in circumstellar disks, and the time available for planet formation. In particular, we use high-resolution near infrared spectroscopy to address the following issues: (1)Does H3+ originate in dense molecular clouds? Since the discovery of H 3+ in the ISM, it has been observed through numerous lines of sight including dense and diffuse clouds. There is some controversy surrounding the interpretation of H3+ observations toward dense clouds. Some argue that most of the observed H3 + originates in diffuse material surrounding dense clouds rather than in the dense clouds. With this controversy in mind, we present observations of H3+ toward LkH?101 and discuss the feasibility of the ion originating in dense material. (2)Is there any evidence of gas/dust stratification in circumstellar disks? Gas and dust mixing in the extended disk around a young star is one of the most debated and untested results of theoretical modeling in recent years. Theoretical models of dust/gas mixing in the disk are at odds but the predictions set the stage for observations to guide our ideas of planet formation. The vertical distribution of dust and gas in disks is assessed by simultaneous comparison of infrared CO absorption lines with infrared extinction. We demonstrate that the most straightforward interpretation of the existing data confirms the stratification of dust and gas in circumstellar disks. (3)How long does gas survive in the inner circumstellar disks? We present near infrared high-resolution spectra of CO from the circumstellar protoplanetary region around young stars. The spectra are compared to the spectral energy distribution for each star. The CO observations are used to determine the mass, density and temperature of the gas around the star and the spectral energy distribution is used to gauge the evolutionary status of the dust disk. Implications for the evolution of the disk and subsequent planet formation are discussed.

  1. A high angular resolution survey of circumstellar dust around Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Perrin, Marshall Dimsey

    This thesis presents the development of a sensitive near-infrared differential imaging polarimeter, and its subsequent use, combined with mid infrared imaging, to survey circumstellar dust around 110 Herbig Ae/Be stars. Planets are born in dusty circumstellar disks around young stars. By imaging such disks we can learn about the environment and physical processes that assemble planets from primordial dust and gas. But these observations are challenging on account of the high angular resolution and high dynamic range necessary to detect the disk's faint reflected light against a far brighter background of stellar light. One powerful method for obtaining the necessary contrast is the use of differential polarimetry to separate polarized dust-scattered light from unpolarized starlight. For this reason, I have developed a differential polarimetry mode for IRCAL, the adaptive optics science camera at Lick Observatory, which uses a YLF Wollaston prism beamsplitter to attenuate 98-99% of stellar light. I describe this instrument, summarize the data reduction and image analysis algorithms employed, and discuss lessons learned for future high-contrast imaging systems. A second strategy for high contrast science is to obtain observations at mid-infrared wavelengths, where dust is bright and stellar light is comparatively faint. These two techniques are complementary, respectively probing scattered and thermal light, and their multiwavelength combination can help constrain numerical models of circumstellar disks and envelopes. I have obtained near-IR adaptive optics imaging polarimetry and mid-IR imaging of a large sample of Herbig Ae/Be stars; 110 targets were observed with AO polarimetry and 61 with mid-IR imaging. Of these stars, 40 are found to have extended polarized nebulosity arising from scattered light. The dust geometry is highly variable, ranging from circumstellar disks to envelopes split by bipolar outflow cavities to complex arcs and lanes of dust spiraling around and between stars. I present detailed studies of a subset of these objects, including laser guide star AO observations of disks and envelopes around the stars LkHalpha 198 and LkHalpha 233; the discovery of the first resolved edge-on circumstellar disk around a Herbig Ae/Be star, PDS 144 N; and integral field spectroscopy of a narrowly collimated bipolar outflow from LkHalpha 233. I conclude by discussing future prospects for advances in the studies of circumstellar disks with the coming generation of high contrast instruments.

  2. Sleep patterns and habits in high school students in Iran

    Microsoft Academic Search

    Ahmad Ghanizadeh; Mohsen Kianpoor; Mehdi Rezaei; Hadi Rezaei; Rozita Moini; kamran Aghakhani; Jamshid Ahmadi; Seyed Reza Moeini

    2008-01-01

    BACKGROUND: Sleep patterns and habits in high school students in Iran have not been well studied to date. This paper aims to re-address this balance and analyse sleep patterns and habits in Iranian children of high school age. METHODS: The subjects were 1,420 high school students randomly selected by stratified cluster sampling. This was a self-report study using a questionnaire

  3. Habits: bridging the gap between personhood and personal identity

    PubMed Central

    Wagner, Nils-Frederic; Northoff, Georg

    2014-01-01

    In philosophy, the criteria for personhood (PH) at a specific point in time (synchronic), and the necessary and sufficient conditions of personal identity (PI) over time (diachronic) are traditionally separated. Hence, the transition between both timescales of a person's life remains largely unclear. Personal habits reflect a decision-making (DM) process that binds together synchronic and diachronic timescales. Despite the fact that the actualization of habits takes place synchronically, they presuppose, for the possibility of their generation, time in a diachronic sense. The acquisition of habits therefore rests upon PI over time; that is, the temporal extension of personal decisions is the necessary condition for the possible development of habits. Conceptually, habits can thus be seen as a bridge between synchronic and diachronic timescales of a person's life. In order to investigate the empirical mediation of this temporal linkage, we draw upon the neuronal mechanisms underlying DM; in particular on the distinction between internally and externally guided DM. Externally guided DM relies on external criteria at a specific point in time (synchronic); on a neural level, this has been associated with lateral frontal and parietal brain regions. In contrast, internally guided DM is based on the person's own preferences that involve a more longitudinal and thus diachronic timescale, which has been associated with the brain's intrinsic activity. Habits can be considered to reflect a balance between internally and externally guided DM, which implicates a particular temporal balance between diachronic and synchronic elements, thus linking two different timescales. Based on such evidence, we suggest a habit-based neurophilosophical approach of PH and PI by focusing on the empirically-based linkage between the synchronic and diachronic elements of habits. By doing so, we propose to link together what philosophically has been described and analyzed separately as PH and PI. PMID:24904370

  4. A simplified habit reversal treatment for pica-related chewing.

    PubMed

    Woods, D W; Miltenberger, R G; Lumley, V A

    1996-09-01

    In this study the frequency of chewing behavior in a 6-year-old male diagnosed with pica was reduced using a simplified habit reversal procedure. Data were collected on the frequency of chewing behavior, treatment acceptability, parent satisfaction, and social validity of the behavior change. This study represents the first known application of the habit reversal procedure to treat pica-related chewing in a normally intelligent child. PMID:8959427

  5. Habits: bridging the gap between personhood and personal identity.

    PubMed

    Wagner, Nils-Frederic; Northoff, Georg

    2014-01-01

    In philosophy, the criteria for personhood (PH) at a specific point in time (synchronic), and the necessary and sufficient conditions of personal identity (PI) over time (diachronic) are traditionally separated. Hence, the transition between both timescales of a person's life remains largely unclear. Personal habits reflect a decision-making (DM) process that binds together synchronic and diachronic timescales. Despite the fact that the actualization of habits takes place synchronically, they presuppose, for the possibility of their generation, time in a diachronic sense. The acquisition of habits therefore rests upon PI over time; that is, the temporal extension of personal decisions is the necessary condition for the possible development of habits. Conceptually, habits can thus be seen as a bridge between synchronic and diachronic timescales of a person's life. In order to investigate the empirical mediation of this temporal linkage, we draw upon the neuronal mechanisms underlying DM; in particular on the distinction between internally and externally guided DM. Externally guided DM relies on external criteria at a specific point in time (synchronic); on a neural level, this has been associated with lateral frontal and parietal brain regions. In contrast, internally guided DM is based on the person's own preferences that involve a more longitudinal and thus diachronic timescale, which has been associated with the brain's intrinsic activity. Habits can be considered to reflect a balance between internally and externally guided DM, which implicates a particular temporal balance between diachronic and synchronic elements, thus linking two different timescales. Based on such evidence, we suggest a habit-based neurophilosophical approach of PH and PI by focusing on the empirically-based linkage between the synchronic and diachronic elements of habits. By doing so, we propose to link together what philosophically has been described and analyzed separately as PH and PI. PMID:24904370

  6. Nutritional habits and cognitive performance of older adults.

    PubMed

    Mallidou, Anastasia; Cartie, Mario

    2015-05-01

    Healthy nutritional habits, including drinking plenty of water and maintaining hydration, are fundamental components for sustaining life, health and wellbeing. Evidence has suggested that certain dietary patterns and lifestyles could help delay the ageing process and reduce the risk of Alzheimer's disease. This article explores the potential association between nutritional habits and the cognitive performance of older adults and identifies research gaps that could be filled by future studies on healthy ageing. PMID:26014793

  7. The genetical control of the everbearing habit and three other characters in varieties of fragaria vesca

    Microsoft Academic Search

    T. Brown; P. F. Wareing

    1965-01-01

    A genetical study was made of three diploid varieties of Fragaria vesca, namely, wild type and two cultivated Alpine varieties, “Baron Solemacher” and “Bush White”. The varieties differ in several characters, including flowering habit, runnering habit, branching habit and fruit colour. Wild type is seasonal flowering, produces runners, has a simple branching habit and has red fruit. Both the Alpine

  8. Dynamical habitability in multi-planetary systems resembling the Solar-system

    NASA Astrophysics Data System (ADS)

    Pilat-Lohinger, Elke; Robutel, Philippe; Süli, Aron

    2010-05-01

    The dynamics in our Solar System is certainly dominated by the two giant planets Jupiter and Saturn which are close to the 5:2 MMR (i.e. mean motion resonance). We present a study of different Jupiter-Saturn like configurations - where Saturn's semi-major axis (aS) and mass (mS) was varied: aS between 8 and 11 AU and mS was increased up to 40 times its mass. The selected range of aS scans the region between two important low-order MMRs - the 2:1 and the 3:1 MMRs. Within this range several higher order MMRs characterize the motion. For the different configurations the stability of Earth-like planets in the habitable zone (HZ) was examined. The HZ is a defined area for human life near a Sun-like star. In our solar system the HZ reaches from 0.95 AU to 1.37 AU (according to the work by Kasting et al. 1993). In our study the HZ was extended in order to obtain additional information for the positions of Venus and Mars. We will show that the HZ is visibly influenced by MMRs and secular resonances, which might lead to high eccentric motion so that the terrestrial planet will leave the HZ periodically. Therefore, we are able to exclude configurations, since they do not provide the necessary conditions for dynamical habitability.

  9. Microbial habitability of the Hadean Earth during the late heavy bombardment

    NASA Astrophysics Data System (ADS)

    Abramov, Oleg; Mojzsis, Stephen J.

    2009-05-01

    Lunar rocks and impact melts, lunar and asteroidal meteorites, and an ancient martian meteorite record thermal metamorphic events with ages that group around and/or do not exceed 3.9Gyr. That such a diverse suite of solar system materials share this feature is interpreted to be the result of a post-primary-accretion cataclysmic spike in the number of impacts commonly referred to as the late heavy bombardment (LHB). Despite its obvious significance to the preservation of crust and the survivability of an emergent biosphere, the thermal effects of this bombardment on the young Earth remain poorly constrained. Here we report numerical models constructed to probe the degree of thermal metamorphism in the crust in the effort to recreate the effect of the LHB on the Earth as a whole; outputs were used to assess habitable volumes of crust for a possible near-surface and subsurface primordial microbial biosphere. Our analysis shows that there is no plausible situation in which the habitable zone was fully sterilized on Earth, at least since the termination of primary accretion of the planets and the postulated impact origin of the Moon. Our results explain the root location of hyperthermophilic bacteria in the phylogenetic tree for 16S small-subunit ribosomal RNA, and bode well for the persistence of microbial biospheres even on planetary bodies strongly reworked by impacts.

  10. The role of dynamics on the habitability of an Earth-like planet

    E-print Network

    Pilat-Lohinger, E

    2015-01-01

    From the numerous detected planets outside the Solar system, no terrestrial planet comparable to our Earth has been discovered so far. The search for an Exo-Earth is certainly a big challenge which may require the detections of planetary systems resembling our Solar system in order to find life like on Earth. However, even if we find Solar system analogues, it is not certain that a planet in Earth position will have similar circumstances as those of Earth. Small changes in the architecture of the giant planets can lead to orbital perturbations which may change the conditions of habitability for a terrestrial planet in the habitable zone (HZ). We present a numerical investigation where we first study the motion of test-planets in a particular Jupiter-Saturn configuration for which we can expect strong gravitational perturbations on the motion at Earth position according to a previous work. In this study, we show that these strong perturbations can be reduced significantly by the neighboring planets of Earth. I...

  11. The effects of M dwarf magnetic fields on potentially habitable planets

    E-print Network

    Vidotto, A A; Morin, J; Donati, J -F; Lang, P; Russell, A J B

    2013-01-01

    We investigate the effect on potentially-habitable Earth-like planets of the magnetic fields of M dwarf (dM) stars. Such fields can reduce the size of planetary magnetospheres to such an extent that a significant fraction of the planet's atmosphere may be exposed to erosion by the stellar wind. We use the sample of 15 active dM stars, for which surface magnetic field maps have been reconstructed, to determine the magnetic pressure at the planet's orbit and hence the minimum size of its magnetosphere, which would only be increased by considering the stellar wind. Our method provides a fast means to assess which planets are most affected by the stellar magnetic field. We show that hypothetical Earth-like planets with similar terrestrial magnetisation (1G) orbiting at the inner (outer) edge of the habitable zone of these stars would present magnetospheres that extend at most up to 6 (11.7) planetary radii. With the exception of a couple of cases, to be able to sustain an Earth-sized magnetosphere, the terrestria...

  12. Microbial habitability of the Hadean Earth during the late heavy bombardment.

    PubMed

    Abramov, Oleg; Mojzsis, Stephen J

    2009-05-21

    Lunar rocks and impact melts, lunar and asteroidal meteorites, and an ancient martian meteorite record thermal metamorphic events with ages that group around and/or do not exceed 3.9 Gyr. That such a diverse suite of solar system materials share this feature is interpreted to be the result of a post-primary-accretion cataclysmic spike in the number of impacts commonly referred to as the late heavy bombardment (LHB). Despite its obvious significance to the preservation of crust and the survivability of an emergent biosphere, the thermal effects of this bombardment on the young Earth remain poorly constrained. Here we report numerical models constructed to probe the degree of thermal metamorphism in the crust in the effort to recreate the effect of the LHB on the Earth as a whole; outputs were used to assess habitable volumes of crust for a possible near-surface and subsurface primordial microbial biosphere. Our analysis shows that there is no plausible situation in which the habitable zone was fully sterilized on Earth, at least since the termination of primary accretion of the planets and the postulated impact origin of the Moon. Our results explain the root location of hyperthermophilic bacteria in the phylogenetic tree for 16S small-subunit ribosomal RNA, and bode well for the persistence of microbial biospheres even on planetary bodies strongly reworked by impacts. PMID:19458721

  13. Climate of Earth-like planets with high obliquity and eccentric orbits: Implications for habitability conditions

    NASA Astrophysics Data System (ADS)

    Linsenmeier, Manuel; Pascale, Salvatore; Lucarini, Valerio

    2015-01-01

    We explore the effects of seasonal variability for the climate of Earth-like planets as determined by the two parameters polar obliquity and orbital eccentricity using a general circulation model of intermediate complexity. In the first part of the paper we examine the consequences of different values of obliquity and eccentricity for the spatio-temporal patterns of radiation and surface temperatures as well as for the main characteristics of the atmospheric circulation. In the second part of the paper we analyse the associated implications for the habitability of planets close to the outer edge of the habitable zone (HZ). The second part focuses in particular on the multistability property of climate, i.e. the parallel existence of both an ice-free and an ice-covered climate state. Our results show that seasonal variability affects both the existence of and transitions between the two climate states. Moreover, our experiments reveal that planets with Earth-like atmospheres and high seasonal variability can have ice-free areas at much larger distance from the host star than planets without seasonal variability, which leads to a substantial expansion of the outer edge of the HZ. Sensitivity experiments exploring the role of azimuthal obliquity and surface heat capacity test the robustness of our results. On circular orbits, our findings obtained with a general circulation model agree well with previous studies based on one dimensional energy balance models, whereas significant differences are found on eccentric orbits.

  14. Habitable Environments Include Acidic Zones: Looking Beyond an Alkaline Environment for Signatures of Life on Mars

    NASA Astrophysics Data System (ADS)

    Lane, M. D.

    2014-07-01

    Our objective is to challenge the notion of searching for evidence of life only in a near-neutral pH, mid-range saline, water-rich environments on Mars, and to recommend potential settings that look beyond traditional “Goldilocks” regions.

  15. Habitability in Different Milky Way Stellar Environments: a Stellar Interaction Dynamical Approach

    E-print Network

    Jiménez-Torres, Juan J; Lake, George; Segura, Antígona

    2013-01-01

    Every Galactic environment is characterized by a stellar density and a velocity dispersion. With this information from literature, we simulated flyby encounters for several Galactic regions, numerically calculating stellar trajectories as well as orbits for particles in disks; our aim was to understand the effect of typical stellar flybys on planetary (debris) disks in the Milky Way Galaxy. For the Solar neighborhood, we examined nearby stars with known distance, proper motions, and radial velocities. We found occurrence of a disturbing impact to the Solar planetary disk within the next 8 Myr to be highly unlikely; perturbations to the Oort cloud seem unlikely as well. Current knowledge of the full phase space of stars in the Solar neighborhood, however, is rather poor, and thus we cannot rule out the existence of a star that is more likely to approach than those for which we have complete kinematic information. We studied the effect of stellar encounters on planetary orbits within the habitable zones of star...

  16. Searching for HabitableSearching for Habitable Worlds and Life in theWorlds and Life in the

    E-print Network

    Guyon, Olivier

    of habitable exoplanets: Why is it hard ? #12;#12;Coronagraphy ... Using optics tricks to remove starlight planets around other stars We need a better coronagraph... and a larger eye (telescope) #12;What is light

  17. Images of star-forming regions. II - The circumstellar environment of L1551 IRS 5

    NASA Technical Reports Server (NTRS)

    Campbell, Bel; Persson, S. E.; Strom, Stephen E.; Grasdalen, Gary L.

    1988-01-01

    The circumstellar environment of L 1551 IRS 5 is investigated based on high-resolution 8000 A (i) and 9000 A (z) broadband CCD images. A small conical reflection nebula extending from a bright semistellar knot located near the cusp of the nebula is noted. It is suggested that the point-like structure at lambda of less than about 3.7 microns may represent a bright knot of dust-scattered light located on the inner surface of a flattened circumstellar disk surrounding the radio source. Evidence is found of sharp changes in the position angle of the jet emanating from IRS 5, possibly resulting from precession of the jet nozzle provided by a dense inner disk which has dynamically decoupled from the much larger flattened molecular structure.

  18. Fresnel zone interferometric imaging

    Microsoft Academic Search

    D. J. Brady; D. L. Marks; R. Stack

    1998-01-01

    We describe how Fourier analysis in projective coordinates allows inversion in the Fresnel zone. Since the longitudinal resolution of 3D coherence imaging falls inversely in the square of range in both the Fresnel and Fraunhofer zones, extension to the Fresnel zone dramatically improves longitudinal resolution by removing far-field range constraints in Michelson rotational shear interferometry

  19. Figure This: Time Zones

    NSDL National Science Digital Library

    2004-01-01

    This is an activity featuring a time zone map useful when teaching an interdisciplinary social studies and math unit focusing on geography and the time zones. It underscores the role of the earth's rotation in everyday life, and the need to understand the relationships between earth rotation, day and night, and time zones around the world.

  20. Zone Refining by Laser

    NASA Technical Reports Server (NTRS)

    Griner, D. B.

    1986-01-01

    System developed for studying use of laser beam for zone-refining semiconductors and metals. Specimen scanned with focused CO2 laser beam in such way that thin zone of molten material moves along specimen sweeps impurities with it. Zone-melting system comprises microcomputer, laser, electromechanical and optical components for beam control, vacuum chamber that holds specimen, and sensor for determining specimen temperature.

  1. Circumstellar Structure Properties of Young Stellar Objects: Envelopes, Bipolar Outflows, and Disks

    Microsoft Academic Search

    Woojin Kwon

    2009-01-01

    Physical properties of the three main structures in young stellar objects (YSOs), envelopes, bipolar outflows, and circumstellar disks, have been studied using radio interferometers: the Berkeley-Illinois-Maryland Association (BIMA) array and the Combined Array for Research in Millimeter-wave Astronomy (CARMA). (1) Envelopes. Three Class 0 YSOs (L1448 IRS 2, L1448 IRS 3, and L1157) have been observed by CARMA at lambda

  2. Small-scale structure of the circumstellar gas of HL Tauri and R Monocerotis

    Microsoft Academic Search

    S. Beckwith; A. I. Sargent; N. Z. Scoville; C. R. Masson; B. Zuckerman; T. G. Phillips

    1986-01-01

    Interferometric observations of CO (J = 1-0) emission in HL Tau and R Mon reveal small-scale concentrations of molecular gas coincident with both stars. The line widths are small, less than 3 km\\/s, and centered close to the stellar velocities, indicating that these condensations are bound to the stars. Lower limits to the circumstellar masses are derived from the CO

  3. Exocomets and variable circumstellar gas absorption in the debris disks of nearby A-type stars

    NASA Astrophysics Data System (ADS)

    Montgomery, Sharon Lynn; Welsh, Barry; Bukoski, Benjamin; Strausbaugh, Sarah

    2015-01-01

    Over the past five years, more than a dozen new star systems have been discovered that are similar to the famous and well-described Beta Pictoris system. Like Beta Pictoris, these systems include a young A-type star, a circumstellar gas-poor debris disk, and infalling exocomets. The presence of comets has been inferred from night-to-night changes in the absorption-line characteristics of the circumstellar disk CaII K-line at 3933Å towards these stars. As described by the Falling Evaporated Bodies model of Beust et al (1990, 1998), comet-like planetesimals residing in the outer regions of the dust disk are perturbed into eccentric star-grazing orbits by the action of either mutual collisions or by the gravitational influence of an accompanying massive exoplanet. The plume of gas is liberated at the comet's close approach to the star.We present new high resolution absorption spectra of the CaII K line recorded over several nights towards the nearby and young (< 50 Myr) A-type stars HD 80007 and HD 109573. Both stars exhibit circumstellar absorption variability that is similar to that frequently observed in other `exocomet-systems', such as Beta Pictoris and 49 Ceti. We also present a list of the physical characteristics of ~40 A-type stars with associated debris disks that possess circumstellar absorption spectra of the CaII K-line observed by us over several nights. Using all of these data we comment on which stellar parameter(s) seem to be the most important in determining whether or not exocomets will be detected in a given system.

  4. Physical Conditions in the SN 1987A Inner Circumstellar Ring 12 Years After Outburst

    Microsoft Academic Search

    R. C. Iping; G. Sonneborn; C. S. J. Pun

    1999-01-01

    The inner circumstellar ring around SN 1987A was observed on 14 Nov 1998 with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope. Medium resolution spectra (gratings G430M and G750M, resolution 50-100km\\/s) of several emission lines were obtained with a long, narrow (0.2 arcsec) slit approximately aligned with the inner ring's major axis. Thus the long slit sampled

  5. Circumstellar interaction and a pulsar nebula in the supenova 1986j

    Microsoft Academic Search

    Roger A. Chevalier

    1987-01-01

    The supernova SN 1986j in NGC 891 was first discovered as a radio source in August 1986. The author shows that the circumstellar interaction model for radio supernovae provides an adequate fit to the existing data. A shell-like source structure is expected. The model together with VLBI observations of the radio source, implies a shock velocity of ?104km s-1 and

  6. FORMING HABITABLE PLANETS AROUND DWARF STARS: APPLICATION TO OGLE-06-109L

    SciTech Connect

    Wang Su; Zhou Jilin, E-mail: suwang@nju.edu.cn, E-mail: zhoujl@nju.edu.cn [Department of Astronomy and Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing 210093 (China)

    2011-02-01

    Dwarf stars are believed to have a small protostar disk where planets may grow up. During the planet formation stage, embryos undergoing type I migration are expected to be stalled at an inner edge of the magnetically inactive disk (a{sub crit} {approx} 0.2-0.3 AU). This mechanism makes the location around a{sub crit} a 'sweet spot' for forming planets. In dwarf stars with masses {approx}0.5 M{sub sun}, a{sub crit} is roughly inside the habitable zone of the system. In this paper, we study the formation of habitable planets due to this mechanism using model system OGLE-06-109L, which has a 0.51 M{sub sun} dwarf star with two giant planets in 2.3 and 4.6 AU observed by microlensing. We model the embryos undergoing type I migration in the gas disk with a constant disk-accretion rate ( M-dot ). Giant planets in outside orbits affect the formation of habitable planets through secular perturbations at the early stage and secular resonance at the late stage. We find that the existence and the masses of the habitable planets in the OGLE-06-109L system depend on both M-dot and the speed of type I migration. If planets are formed earlier, so that M-dot is larger ({approx}10{sup -7} M{sub sun} yr{sup -1}), terrestrial planets cannot survive unless the type I migration rate is an order of magnitude less. If planets are formed later, so that M-dot is smaller ({approx}10{sup -8} M{sub sun} yr{sup -1}), single and high-mass terrestrial planets with high water contents ({approx}5%) will be formed by inward migration of outer planet cores. A slower-speed migration will result in several planets via collisions of embryos, and thus their water contents will be low ({approx}2%). Mean motion resonances or apsidal resonances among planets may be observed if multiple planets survive in the inner system.

  7. Search for a habitable terrestrial planet transiting the nearby red dwarf GJ 1214

    NASA Astrophysics Data System (ADS)

    Gillon, M.; Demory, B.-O.; Madhusudhan, N.; Deming, D.; Seager, S.; Zsom, A.; Knutson, H. A.; Lanotte, A. A.; Bonfils, X.; Désert, J.-M.; Delrez, L.; Jehin, E.; Fraine, J. D.; Magain, P.; Triaud, A. H. M. J.

    2014-03-01

    High-precision eclipse spectrophotometry of transiting terrestrial exoplanets represents a promising path for the first atmospheric characterizations of habitable worlds and the search for life outside our solar system. The detection of terrestrial planets transiting nearby late-type M-dwarfs could make this approach applicable within the next decade, with soon-to-come general facilities. In this context, we previously identified GJ 1214 as a high-priority target for a transit search, as the transit probability of a habitable planet orbiting this nearby M4.5 dwarf would be significantly enhanced by the transiting nature of GJ 1214 b, the super-Earth already known to orbit the star. Based on this observation, we have set up an ambitious high-precision photometric monitoring of GJ 1214 with the Spitzer Space Telescope to probe the inner part of its habitable zone in search of a transiting planet as small as Mars. We present here the results of this transit search. Unfortunately, we did not detect any other transiting planets. Assuming that GJ 1214 hosts a habitable planet larger than Mars that has an orbital period smaller than 20.9 days, our global analysis of the whole Spitzer dataset leads to an a posteriori no-transit probability of ~98%. Our analysis allows us to significantly improve the characterization of GJ 1214 b, to measure its occultation depth to be 70 ± 35 ppm at 4.5 ?m, and to constrain it to be smaller than 205 ppm (3? upper limit) at 3.6 ?m. In agreement with the many transmission measurements published so far for GJ 1214 b, these emission measurements are consistent with both a metal-rich and a cloudy hydrogen-rich atmosphere. The photometric time series used in this work 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/563/A21

  8. High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A

    NASA Technical Reports Server (NTRS)

    Serabyn, G.; Grady, C. A.; Currie, T.

    2012-01-01

    We present H-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0.15" (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A which extends to 120 AU, at a spatial resolution of 0.1" (14 AU). It is inclined by 46 degrees plus or minus 2 degrees as the west side is nearest. Although SED modeling and sub-millimeter imagery suggested the presence of a gap in the disk, with the inner edge of the outer disk estimated to be located at 25 - 30 AU, we detect no evidence of a gap at the limit of our inner working angle (23AU) at the near-infrared wavelength. We attribute the observed strong polarization (up to 66 %) to light scattering by dust grains in the disk. However, neither polarization models of the circumstellar disk based on Rayleigh scattering nor Mie scattering approximations were consistent with the observed azimuthal profile of the polarization degrees of the disk. Instead, a geometric optics model of the disk with nonspherical grains with the radii of 30 micrometers is consistent with the observed profile. We suggest that the dust grains have experienced frequent collisional coagulations and have grown in the circumstellar disk of UX Tau A.

  9. Main zones of the intertidal zone

    NSDL National Science Digital Library

    Katie Hale (California State University, Fullerton; Student, Biological Sciences)

    2007-01-04

    The intertidal zone is found where the tides rise and fall daily, alternatively submerging and exposing the shore to ocean water. Organisms must be able to tolerate times of intense sunlight, little moisture, and wave forces.

  10. Main zones of the intertidal zone

    NSDL National Science Digital Library

    Katie Hale (CSUF; Biological Sciences)

    2007-06-08

    The intertidal zone is found where the tides rise and fall daily, alternatively submerging and exposing the shore to ocean water. Organisms must be able to tolerate times of intense sunlight, little moisture, and wave forces.

  11. Habitability of Terrestrial Planets in the Early Solar System

    NASA Astrophysics Data System (ADS)

    SLEEP, N. H.

    2001-12-01

    The Protoearth, Mars, Venus, and the Moon-forming impactor were potentially habitable in the early solar system. The interiors of larger asteroids had habitable circulating water. To see when the inner solar system became continuously habitable, one needs to consider the most dangerous events and the safest refugia from them. Early geochemical and accretionary processes set the subsequent silicate planet reservoirs and hence hydrospheric and atmospheric masses. The moon-forming impact made the Moon and the Earth sterile bodies. Following the impact, the Earth passed through a rock-vapor atmosphere on the scale of 1000s of years and an internally heated steam greenhouse on the scale of 2 m.y. Minerals bearing the principle volatiles (water, Cl, and CO2) were stable at the Earth's surface by the time it cooled to 800K. The mass of reactable shallow material was insufficient to contain the available water and CO2. Habitable conditions were established after CO2 could be deeply subducted into the mantle. Vast quantities of H2 were vented during accretion and after the moon-forming impact and eventually lost to space. It is unknown whether significant amounts of this gas were present when the Earth's surface cooled into the habitable range. The moon remained sterile because its interior is essentially devoid of water. The mantle of the Earth, in contrast, cannot hold the available water, leaving the excess to form oceans. Nitrogen may behave similarly with the excess going into the air. Impacts of large asteroids (and comets) were an ever-present danger on otherwise habitable planets. The safest niche on planets was kilometer or deeper crustal rocks habitable by thermophiles. It is inevitable that several objects, which would have left only thermophile survivors, struck the Earth. Such events were so infrequent that the conditions of such a bottleneck should not be confused with conditions for the origin of life. An alternative refugium involves ejection of life within rock fragments and return of such fragments to the surface of the home planet or transfer to another habitable planet. Mars and the larger asteroids were habitable first and provide likely sources of seed and also testable places to look for preserved evidence. Extant terrestrial life appears to have passed through thermophile bottlenecks. There are subtle hints of space transfer. The need of extant life for Ni may be a vestige of life on a young planet covered with ultramafic rocks.

  12. Life History of the Longnose Dace, Rhinichthys cataractae, in the Surge Zone of Eastern Lake Michigan Near Ludington, Michigan

    Microsoft Academic Search

    Dan C. Brazo; Charles R. Liston; Robert C. Anderson

    1978-01-01

    Longnose dace taken mainly during night hours over gravel-rock substrates in a surge zone of east-central Lake Michigan provided seasonal data on distribution, age, growth, maturity, fecundity, and food habits. Dominated by age-classes II and III, longnose dace entered surge-zone waters in mid-May for spawning and remained in small numbers through November. Peak spawning occurred during late June and early

  13. Shielding requirements for the Space Station habitability modules

    NASA Technical Reports Server (NTRS)

    Avans, Sherman L.; Horn, Jennifer R.; Williamsen, Joel E.

    1990-01-01

    The design, analysis, development, and tests of the total meteoroid/debris protection system for the Space Station Freedom habitability modules, such as the habitation module, the laboratory module, and the node structures, are described. Design requirements are discussed along with development efforts, including a combination of hypervelocity testing and analyses. Computer hydrocode analysis of hypervelocity impact phenomena associated with Space Station habitability structures is covered and the use of optimization techniques, engineering models, and parametric analyses is assessed. Explosive rail gun development efforts and protective capability and damage tolerance of multilayer insulation due to meteoroid/debris impact are considered. It is concluded that anticipated changes in the debris environment definition and requirements will require rescoping the tests and analysis required to develop a protection system.

  14. Spacecraft Habitable Volume: Results of an Interdisciplinary Workshop

    NASA Technical Reports Server (NTRS)

    Fitts, David J.; Connolly, Janis; Howard, Robert

    2011-01-01

    NASA's Human Exploration Framework Team posed the question: "Is 80 cubic meters per person of habitable volume acceptable for a proposed Deep Space Habitat?" The goal of the workshop was to address the "net habitable volume" necessary for long-duration human spaceflight missions and identify design and psychological issues and mitigations. The objectives were: (1) Identify psychological factors -- i.e., "stressors" -- that impact volume and layout specifications for long duration missions (2) Identify mitigation strategies for stressors, especially those that can be written as volume design specifications (3) Identify a forward research roadmap -- i.e., what future work is needed to define and validate objective design metrics? (4) Provide advisories on the human factors consequences of poor net habitable volume allocation and layout design.

  15. Plate tectonics and planetary habitability: current status and future challenges.

    PubMed

    Korenaga, Jun

    2012-07-01

    Plate tectonics is one of the major factors affecting the potential habitability of a terrestrial planet. The physics of plate tectonics is, however, still far from being complete, leading to considerable uncertainty when discussing planetary habitability. Here, I summarize recent developments on the evolution of plate tectonics on Earth, which suggest a radically new view on Earth dynamics: convection in the mantle has been speeding up despite its secular cooling, and the operation of plate tectonics has been facilitated throughout Earth's history by the gradual subduction of water into an initially dry mantle. The role of plate tectonics in planetary habitability through its influence on atmospheric evolution is still difficult to quantify, and, to this end, it will be vital to better understand a coupled core-mantle-atmosphere system in the context of solar system evolution. PMID:22256796

  16. Healthy Habits for Children: Leveraging Existing Evidence to Demonstrate Value.

    PubMed

    Persch, Andrew C; Lamb, Amy J; Metzler, Christina A; Fristad, Mary A

    2015-01-01

    Healthy habits is a psychoeducational construct that refers to the preventive practice of analyzing and then adapting the sleep, physical, and eating routines of children in ways that enhance health and well-being. This approach is based on evidence that demonstrates the positive therapeutic value of engaging in proactive, healthful behaviors. In addressing healthy habits, occupational therapy practitioners have an opportunity to contribute to the Triple Aim of health care reform while demonstrating the value of occupational therapy in educational, medical, community, and other settings. PMID:26114454

  17. Health promoting habits of people who pray for their health.

    PubMed

    Harrigan, John T

    2011-09-01

    To determine the health habits of people who pray for their health, data from the National Health Interview Survey was analyzed for health habits of people who prayed or did not pray for their health. Of the 22,314 respondents, 13,179 (59%) prayed for their health. These individuals saw a physician more frequently, participated more frequently in vigorous exercise and used more relaxation techniques, support groups, meditation and complimentary and alternative medicine therapies. People who pray for their health participate in more health promoting behaviors than people who do not pray for their health. PMID:19859811

  18. Introduction to Ocean Zones

    NSDL National Science Digital Library

    COSEE West

    2012-01-01

    In this activity, learners will create a diagram of the ocean zones and determine what organisms live in each zone. Learners will draw the appropriate scale to demark meters (and conversion to feet) from 0-6000m and draw the zones that correspond to the geological structures of the ocean basin. Finally, learners will use their critical thinking skills to determine where in the ocean each organism lives and place the organism in the habitat that is within the limitations for survival.

  19. Indicator of Exo-Solar Planet(s) in the Circumstellar Disk Around Beta Pictoris

    E-print Network

    Nick Gorkavyi; Sara Heap; Leonid Ozernoy; Tanya Taidakova; John Mather

    2000-12-21

    Our efficient numerical approach has been applied to modeling the asymmetric circumstellar dust disk around Beta Pictoris as observed with the HST/STIS. We present a new model on the origin of the warping of the Beta Pic disk. We suggest that the observed warp is formed by the gravitational influence of a planet with a mass of about 10 masses of Earth, at a distance of 70 AU, and a small inclination ($\\sim 2.5^\\circ$) of the planetary orbit to the main dust disk. Results of our modeling are compared with the STIS observations.

  20. Archival Legacy Investigation of Circumstellar Environments using KLIP algorithm on HST NICMOS coronagraphic data

    NASA Astrophysics Data System (ADS)

    Choquet, Elodie; Hagan, J. Brendan; Pueyo, Laurent; Perrin, Marshall D.; Hines, Dean C.; Chen, Christine; Schneider, Glenn; Debes, John; Golimowski, David; Reid, Neill; Mittal, Tushar; Moerchen, Margaret; N'Diaye, Mamadou; Rajan, Abhijith; Lonsdale, Sean; Soummer, Remi

    2014-01-01

    The Archival Legacy Investigation of Circumstellar Environments (ALICE) project (AR-12652) is currently conducting a comprehensive and consistent reprocessing of HST-NICMOS coronagraphic survey data to search for point sources and disks using advanced PSF subtraction. The KLIP algorithm (Karhunen-Loève Image Projection) was developed for this project, and has proven very effective at processing the hundreds of selected archival images. This project has already been very successful with numerous detections of previously unseen point sources and several resolved debris disks that we are currently following up by multiple avenues. We give an overview of the project including preliminary scientific results with companion candidates and improved images of known disks

  1. Infrared images of Monoceros R2 IRS 3 - Evidence for a circumstellar disk

    NASA Technical Reports Server (NTRS)

    Koresko, C. D.; Beckwith, S.; Ghez, A. M.; Matthews, K.; Herbst, T. M.; Smith, D. A.

    1993-01-01

    Diffraction-limited IR images of the protostellar system Mon R2 IRS 3 reveal a bright conical nebula which extends about 0.5 arcsec south from the southern component of the previously known star pair. The bright nebula is probably dust scattering the starlight which emerges along the polar axis of a large (greater than 500 AU) circumstellar disk. We estimate a lower limit to the disk mass of 3 X 10 exp -2 solar masses. A faint, previously unknown pointlike source lies 0.37 arcsec east of the northern star.

  2. Modeling and Simulation of Circumstellar Disks with the Next Generation of Hydrodynamic Solvers

    NASA Astrophysics Data System (ADS)

    Munoz, Diego Jose

    This thesis is a computational study of circumstellar gas disks, with a special focus on modeling techniques and on numerical methods not only as scientific tools but also as a target of study. In particular, in-depth discussions are included on the main numerical strategy used, namely the moving-mesh method for astrophysical hydrodynamics. In this work, the moving-mesh approach is used to simulate circumstellar disks for the first time. The structure of the thesis follows a natural progression that begins by discussing the role of computational methods in modern astrophysics, followed by a description of the moving-mesh method as a general solver for gas dynamical problems, and concluding with detailed modeling of circumstellar disks in two and three dimensions, both in isolation and in pairs. The thesis structure consists of two parts. Part I --second and third chapters-- focuses on moving-mesh hydrodynamics and Voronoi meshes in general, deriving the discretized equations of the method from first principles and describing the time-stepping technique in detail. This section also includes original work on numerical methods to include diffusion terms to the equations of hydrodynamics, such as physical viscosity. In Part II of the thesis --fourth, fifth and sixth chapters-- the attention is turned to circumstellar disks. In the fourth chapter, two-dimensional disk simulations are carried out as a benchmarking stage, before more complex, three-dimensional models can be pursued. Novel techniques for creating stable, three-dimensional models of self-gravitating disks with finite radius are discussed in the fifth chapter. In this model, the Voronoi discretization of the computational domain allows for a smooth transition between the mesh that discretizes the disk and the mesh that discretized the background space. Details are provided on how stationary models can be created a priori without the need for relaxation procedures as done in previous work. Finally, the sixth chapter includes a set of simulations that, owing to their complexity, require a scheme that combines the features of the method discussed in preceding chapter. Specifically, such a scheme must be capable of treating self-gravitating systems that (1) lack an obvious symmetry, (2) include regions of high-Mach number flow, (3) have a large dynamical range in density and (4) need an adaptive mesh resolution to adequately capture strongly compressed/shocked regions and potentially fragmentation. To this end, a suite of novel simulations of disk-disk interaction is carried out, to conduct an initial study of the tidal effects that massive disks have on the evolution of their host stars' orbits.

  3. Direct imaging of extra-solar planetary systems with the Circumstellar Imaging Telescope (CIT)

    NASA Technical Reports Server (NTRS)

    Terrile, Richard J.

    1988-01-01

    In a joint study conducted by the Jet Propulsion Laboratory and the Perkin-Elmer Corporation it was found that an earth orbital, 1.5 meter diameter low scattered light coronagraphic telescope can achieve a broad range of scientific objectives including the direct detection of Jupiter-sized planets around the nearby stars. Recent major advances in the understanding of coronagraphic performance and in the field of super smooth mirror fabrication allow such an instrument to be designed and built within current technology. Such a project, called the Circumstellar Imaging Telescope (CIT), is currently being proposed.

  4. Strontium Isotopic Composition in Individual Circumstellar Silicon Carbide Grains: A Record of {ital s} -Process Nucleosynthesis

    SciTech Connect

    Nicolussi, G.K.; Lewis, R.S.; Davis, A.M.; Clayton, R.N.; Amari, S. [Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States)] [Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637 (United States); Nicolussi, G.K.; Pellin, M.J. [Materials Science Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439 (United States)] [Materials Science Chemistry Divisions, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Davis, A.M.; Clayton, R.N. [Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637 (United States); Clayton, R.N. [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States)] [Department of Chemistry, University of Chicago, Chicago, Illinois 60637 (United States); Amari, S. [McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130 (United States)] [McDonnell Center for the Space Sciences, Washington University, St. Louis, Missouri 63130 (United States)

    1998-10-01

    Twenty six individual circumstellar SiC grains extracted from the Murchison meteorite were analyzed for their strontium isotopic compositions by resonant ionization mass spectrometry. Large abundance deficits were found for the p -process isotope {sup 84}Sr . The measured grains hadthinsp {sup 87}Sr/{sup 86}Sr ratios indistinguishable from the primordial solar value, but several grains differed in theirthinsp {sup 88}Sr/{sup 86}Sr ratios as a consequence of the branch point atthinsp {sup 85}Kr . The Sr isotopic data are consistent with s -process nucleosynthesis at moderate neutron densities. {copyright} {ital 1998} {ital The American Physical Society}

  5. Radiological Habits Survey: Dounreay, 2008 This page has been intentionally left blank

    E-print Network

    Radiological Habits Survey: Dounreay, 2008 #12;This page has been intentionally left blank #12;Radiological Habits Survey: Dounreay, 2008 Final report The Centre for Environment, Fisheries & Aquaculture.........................................................................................12 1.3 Dose limits and constraints

  6. Radiological Habits Survey: Hunterston, 2007 This page has been intentionally left blank

    E-print Network

    Radiological Habits Survey: Hunterston, 2007 #12;This page has been intentionally left blank #12;Radiological Habits Survey: Hunterston, 2007 FINAL REPORT The Centre for Environment, Fisheries & Aquaculture .........................................................................................11 1.3 Dose limits and constraints

  7. FOOD HABITS AND FEEDING CHRONOLOGY OF RAINBOW SMELT, OSMERUS MORDAX,

    E-print Network

    FOOD HABITS AND FEEDING CHRONOLOGY OF RAINBOW SMELT, OSMERUS MORDAX, IN LAKE MICHIGAN' Rainbow feeding chronology during two representative months. Materials and Methods Rainbow smelt were collected and June 1974 (Table 1). Gill nets were placed on the bottom overnight and 45-min trawl hauls performed

  8. Food Habits of the Yellowstone Whitefish Prosopium Williamsoni Cismontanus (Jordan)

    Microsoft Academic Search

    Martin Laakso

    1951-01-01

    A quantitative analysis of the food habits of 385 whitefish (Prosopium williamsoni cismontanus (Jordan)) and 52 trout from the Yellowstone and Gallatin Rivers was made. Collections were taken over a period of 1 year beginning in September, 1947, on the Yellowstone and on the Gallatin Rivers. Fingerling whitefish used the same food organisms as did adults but consumed smaller numbers

  9. 10 Good Habits for a Sound Financial Future

    E-print Network

    ". Educate yourself about the financial options you have in the future; don't rely solely upon the advice10 Good Habits for a Sound Financial Future Limit your use of credit cards, save them and addresses of your lenders. You should also keep copies of all important financial documents (see handout

  10. 10 Good Habits for a Sound Financial Future

    E-print Network

    " and a "want". Educate yourself about the financial options you have in the future; don't rely solely upon10 Good Habits for a Sound Financial Future Limit your use of credit cards, save them, and the names and addresses of your lenders. You should also keep copies of all important financial documents

  11. Factors affecting the reading habits of secondary school students

    Microsoft Academic Search

    S. A. Ogunrombi; Gboyega Adio

    1995-01-01

    Surveys factors affecting the reading habits of secondary school students in Ogbomoso State in Nigeria and discusses the results. Highlights the following inhibiting factors: the family background of students where few homes are conducive to reading owing to noise and lack of reading materials; the lack of functional libraries in most of the schools surveyed and a similar lack of

  12. Radiological Habits Survey: Chapelcross Liquid Effluent Pipeline, 2002

    E-print Network

    Radiological Habits Survey: Chapelcross Liquid Effluent Pipeline, 2002 Science commissioned Pipeline, 2002 The Centre for Environment, Fisheries and Aquaculture Science Lowestoft Laboratory Pakefield OF SURVEY 5 2.1 Pipeline description 5 2.2 Occupancy 6 2.3 Gamma dose rate measurements 7 3 SURVEY FINDINGS

  13. A Guide to Healthy Habits for Cleaner Water

    E-print Network

    Rainforth, Emma C.

    A Guide to Healthy Habits for Cleaner Water ollution on streets, parking lots and lawns is washed andlakesourchildrenplayin. Fertilizer,oil, pesticides, detergents, pet waste, grass clippings:You name it and it ends up of your property or yard in a natural state with trees and othernativevegetation thatrequireslittleorno

  14. Adjusting Lecture Style to Accommodate Student Reading Habits

    ERIC Educational Resources Information Center

    Socash, Richard R.

    2007-01-01

    The reasons behind the reading habits of undergraduate MIS students were examined to learn from the students' point of view why many don't read the textbook. Willingness to work hard on homework and project assignments and an appreciation of what is expected of them appears to be in place. However, carrots, sticks, ruses and requests all meet with…

  15. ASSESSING NORTHERN ELEPHANT SEAL FEEDING HABITS BY STOMACH LAVAGE

    Microsoft Academic Search

    George A. Antonelis; Mark S. Lowry; Douglas P. DeMaster; Clifford H. Fiscus

    1987-01-01

    Stomach lavaging was used to study the feeding habits of northern elephanr seals (Mirounga angustirostris) found on San hliguel Island, California, during the spring of 1984. Fifty-nine elephant seals were chemically immobilized with an intramuscular injection of ketamine hydrochloride. Once immobilized, an animal's stomach was intubated, filled nith 3-4 liters of water to create a slurry of the undigested food

  16. The Information-Seeking Habits of Engineering Faculty

    ERIC Educational Resources Information Center

    Engel, Debra; Robbins, Sarah; Kulp, Christina

    2011-01-01

    Many studies of information-seeking habits of engineers focus on understanding the similarities and differences between scientists and engineers. This study explores the information-seeking behavior of academic engineering faculty from twenty public research universities. This investigation includes an examination of how frequently engineer- ing…

  17. Coincidence of Nutritional Habits and Esophageal Cancer in Germany

    Microsoft Academic Search

    E. Wolfgarten; U. Rosendahl; T. Nowroth; J. Leers; R. Metzger; A. H. Hölscher; E. Bollschweiler

    2001-01-01

    Summary Introduction: The incidence rates for adenocarcinoma (AC) of the esophagus have risen rapidly in Western nations, whereas the incidence rates for esophageal squamous cell carcinoma (SCC) have remained nearly stable. There are studies about body mass index, smoking, alcohol, and development of AC or SCC. The aim of this study was to evaluate differences in nutritional habits of patients

  18. The Reading Habits of Church Active Mormon Women.

    ERIC Educational Resources Information Center

    Appleton, Marianne; Cranney, A. Garr

    Data from 149 female members of the Church of Jesus Christ of Latter Day Saints (LDS) were used to construct a composite of the reading habits and their relation to other characterisitics of this group. The typical respondent was a married woman between 26 and 40 years old who had attended college but remained at home to care for children under…

  19. A Systematic Procedure for Helping Students Overcome Ineffective Communication Habits

    ERIC Educational Resources Information Center

    Tolhuizen, James H.

    2008-01-01

    This paper discusses a systematic four-step program for eliminating ineffective communication habits and replacing them with more effective new communication behaviors. This program has been used successfully to teach a variety of different communication skills including public speaking skills, small group interaction skills, and interpersonal…

  20. A new conceptual design approach for habitative space modules

    NASA Astrophysics Data System (ADS)

    Burattini, C.; Bisegna, F.; Gugliermetti, F.; Marchetti, M.

    2014-04-01

    Existing Space modules were designed to meet the standards established by NASA, basically oriented to functionality. In future Space environments a high level of habitability in long duration missions will become a priority: besides comfort and ergonomics, these habitats will require the application of criteria to address human needs for living in confined environments.