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Planetary body

About: Planetary body is a(n) research topic. Over the lifetime, 251 publication(s) have been published within this topic receiving 5548 citation(s).
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Journal ArticleDOI
Abstract: Aims. We examine the uncertainties in current planetary models and quantify their impact on the planet cooling histories and massradius relationships. Methods. These uncertainties include (i) the differences between the various equations of state used to characterize the heavy material thermodynamical properties, (ii) the distribution of heavy elements within planetary interiors, (iii) their chemical composition, and (iv) their thermal contribution to the planet evolution. Our models, which include a gaseous H/He envelope, are compared with models of solid, gasless Earth-like planets in order to examine the impact of a gaseous envelope on the cooling and the resulting radius. Results. We find that, for a fraction of heavy material larger than 20% of the planet mass, the distribution of the heavy elements in the planet’s interior substantially affects the evolution and thus the radius at a given age. For planets with large core mass fractions (>50%), such as the Neptune-mass transiting planet GJ 436b, the contribution of the gravitational and thermal energy from the core to the planet cooling history is not negligible, yielding a ∼10% effect on the radius after 1 Gyr. We show that the present mass and radius determinations of the massive planet Hat-P-2b require at least 200 M⊕ of heavy material in the interior, at the edge of what is currently predicted by the core-accretion model for planet formation. As an alternative avenue for massive planet formation, we suggest that this planet, and similarly HD 17156b, may have formed from collisions between one or several other massive planets. This would explain these planets unusually high density and high eccentricity. We show that if planets as massive as ∼25 MJ can form, as predicted by improved core-accretion models, deuterium is able to burn in the H/He layers above the core, even for core masses as high as ∼100 M⊕. Such a result highlights the confusion provided by a definition of a planet based on the deuterium-burning limit. Conclusions. We provide extensive grids of planetary evolution models from 10 M⊕ to 10 MJup, with various fractions of heavy elements. These models provide a reference for analyzing the transit discoveries expected from the CoRoT and Kepler missions and for inferring the internal composition of these objects.

357 citations

18 Jan 2010
Abstract: Preface 1. Observations of planetary systems 2. Protoplanetary disk structure 3. Protoplanetary disk evolution 4. Planetesimal formation 5. Terrestrial planet formation 6. Giant planet formation 7. Early evolution of planetary systems Appendixes References Index.

323 citations

Journal ArticleDOI
Abstract: Infrared studies have revealed debris likely related to planet formation in orbit around ~30% of youthful, intermediate mass, main-sequence stars. We present evidence, based on atmospheric pollution by various elements heavier than helium, that a comparable fraction of the white dwarf descendants of such main-sequence stars are orbited by planetary systems. These systems have survived, at least in part, through all stages of stellar evolution that precede the white dwarf. During the time interval (~200 million years) that a typical polluted white dwarf in our sample has been cooling it has accreted from its planetary system the mass of one of the largest asteroids in our solar system (e.g., Vesta or Ceres). Usually, this accreted mass will be only a fraction of the total mass of rocky material that orbits these white dwarfs; for plausible planetary system configurations we estimate that this total mass is likely to be at least equal to that of the Sun's asteroid belt, and perhaps much larger. We report abundances of a suite of eight elements detected in the little studied star G241-6 that we find to be among the most heavily polluted of all moderately bright white dwarfs.

306 citations

Journal ArticleDOI
Abstract: The bulk composition of an exoplanet is commonly inferred from its average density. For small planets, however, the average density is not unique within the range of compositions. Variations of a number of important planetary parameters—whicharedifficultorimpossibletoconstrainfrommeasurementsalone—produceplanetswiththesame averagedensitiesbutwidelyvaryingbulkcompositions.Wefindthataddingagasenvelopeequivalentto0.1%Y10% of the mass of a solid planet causes the radius to increase 5%Y60% above its gas-free value. A planet with a given mass and radius might have substantial water ice content (a so-called ocean planet), or alternatively alarge rocky iron coreandsomeHand/orHe.Forexample,awidevarietyof compositionscanexplaintheobservedradiusof GJ436b, althoughallmodelsrequiresomeH/He.Weconcludethattheidentificationof waterworldsbasedonthemass-radius relationship alone is impossible unless a significant gas layer can be ruled out by other means. Subject headingg planets and satellites: general — planetary systems — stars: individual (GJ 436) Online material: color figures

202 citations

Journal ArticleDOI
Abstract: Beyond the Earth, the Moon is the only planetary body for which we have samples from known locations. The analysis of these samples gives us “ground-truth” for numerous remote sensing studies of the physical and chemical properties of the Moon and they are invaluable for our fundamental understanding of lunar origin and evolution. Prior to the return of the Apollo 11 samples, the Moon was thought by many to be a primitive undifferentiated body (e.g., Urey 1966), a concept shattered by the data returned from the Apollo and Luna missions. Ever since, new data have helped to address some of our questions, but of course, they also produced new questions. In this chapter we provide a summary of knowledge about lunar geologic processes and we describe major scientific advancements of the last decade that are mainly related to the most recent lunar missions such as Galileo, Clementine, and Lunar Prospector. ### 1.1. The Moon in the planetary context Compared to terrestrial planets, the Moon is unique in terms of its bulk density, its size, and its origin (Fig. 1.1a–c⇓), all of which have profound effects on its thermal evolution and the formation of a secondary crust (Fig. 1.1d⇓). Numerous planetary scientists considered the Moon as an endmember among the planetary bodies in our solar system because its lithosphere has been relatively cool, rigid, and intact throughout most of geological time (a “one-plate” planet), and its surface has not been affected by plate recycling, an atmosphere, water, or life. Therefore the Moon recorded and preserved evidence for geologic processes that were active over the last 4–4.5 b.y. and offers us the unique opportunity to look back into geologic times for which evidence on Earth has long been erased (Fig. 1.1c,d⇓). Impact cratering, an exterior process, is considered the most important surface process on the Moon. Internal …

174 citations

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