scholarly journals A Theoretical Framework for the Mass Distribution of Gas Giant Planets Forming through the Core Accretion Paradigm

2021 ◽  
Vol 909 (1) ◽  
pp. 1
Author(s):  
Fred C. Adams ◽  
Michael R. Meyer ◽  
Arthur D. Adams
Keyword(s):  
Mass Distribution ◽  
Theoretical Framework ◽  
Giant Planets ◽  
The Core ◽  
Gas Giant ◽  
Core Accretion

Planetesimal Capture by an Evolving Giant Gaseous Protoplanet

2012 ◽  
Vol 8 (S293) ◽  
pp. 263-269
Author(s):  
Morris Podolak ◽  
Nader Haghighipour
Keyword(s):  
Mass Distribution ◽  
Total Mass ◽  
Size Composition ◽  
Giant Planets ◽  
The Core ◽  
Last Stage ◽  
Core Accretion ◽  
Gaseous Envelope ◽  
Gas Drag ◽  
Probability Of Capture

AbstractBoth the core-accretion and disk-instability models suggest that at the last stage of the formation of a gas-giant, the core of this object is surrounded by an extended gaseous envelope. At this stage, while the envelope is contracting, planetesimals from the protoplanetary disk may be scattered into the protoplanets atmosphere and deposit some or all of their materials as they interact with the gas. We have carried out extensive simulations of approximately 104 planetesimals interacting with a envelope of a Jupiter-mass protoplanet including effects of gas drag, heating, and the effect of the protoplanets extended mass distribution. Simulations have been carried out for different radii and compositions of planetesimals so that all three processes occur to different degrees. We present the results of our simulations and discuss their implications for the enrichment of ices in giant planets. We also present statistics for the probability of capture (i.e. total mass-deposition) of planetesimals as a function of their size, composition, and closest approach to the center of the protoplanetary body.

The formation of a gas giant planet in a viscously evolved protoplanetary disk within the core accretion model

2018 ◽  
Vol 363 (9) ◽  
Author(s):  
Chunjian Liu ◽  
Qing Ai ◽  
Zhen Yao ◽  
Hualian Tian ◽  
Jiayun Shen ◽  
...  
Keyword(s):  
Giant Planet ◽  
Protoplanetary Disk ◽  
The Core ◽  
Accretion Model ◽  
Gas Giant ◽  
Core Accretion

scholarly journals Dynamical stability of giant planets: the critical adiabatic index in the presence of a solid core

2021 ◽  
Vol 507 (4) ◽  
pp. 6215-6224
Author(s):  
Suman Kumar Kundu ◽  
Eric R Coughlin ◽  
Andrew N Youdin ◽  
Philip J Armitage
Keyword(s):  
Incompressible Fluid ◽  
Giant Planets ◽  
Adiabatic Index ◽  
Dynamical Instability ◽  
Solid Core ◽  
Dominant Effect ◽  
Instability Strip ◽  
The Core ◽  
Core Accretion ◽  
Upper Boundary

ABSTRACT The dissociation and ionization of hydrogen, during the formation of giant planets via core accretion, reduce the effective adiabatic index γ of the gas and could trigger dynamical instability. We generalize the analysis of Chandrasekhar, who determined that the threshold for instability of a self-gravitating hydrostatic body lies at γ = 4/3, to account for the presence of a planetary core, which we model as an incompressible fluid. We show that the dominant effect of the core is to stabilize the envelope to radial perturbations, in some cases completely (i.e. for all γ > 1). When instability is possible, unstable planetary configurations occupy a strip of γ values whose upper boundary falls below γ = 4/3. Fiducial evolutionary tracks of giant planets forming through core accretion appear unlikely to cross the dynamical instability strip that we define.

scholarly journals Evolutionary models of cold and low-mass planets: cooling curves, magnitudes, and detectability

2019 ◽  
Vol 623 ◽  
pp. A85 ◽  
Author(s):  
Esther F. Linder ◽  
Christoph Mordasini ◽  
Paul Mollière ◽  
Gabriel-Dominique Marleau ◽  
Matej Malik ◽  
...  
Keyword(s):  
Effective Temperature ◽  
Initial Conditions ◽  
Giant Planets ◽  
Evolutionary Models ◽  
Cooling Curves ◽  
Mid Infrared ◽  
The Core ◽  
Low Mass ◽  
Core Accretion ◽  
The Impact

Context. Future instruments like the Near Infrared Camera (NIRCam) and the Mid Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST) or the Mid-Infrared E-ELT Imager and Spectrograph (METIS) at the European Extremely Large Telescope (E-ELT) will be able to image exoplanets that are too faint (because they have a low mass, and hence a small size or low effective temperature) for current direct imaging instruments. On the theoretical side, core accretion formation models predict a significant population of low-mass and/or cool planets at orbital distances of ~10–100 au. Aims. Evolutionary models predicting the planetary intrinsic luminosity as a function of time have traditionally concentrated on gas-dominated giant planets. We extend these cooling curves to Saturnian and Neptunian planets. Methods. We simulated the cooling of isolated core-dominated and gas giant planets with masses of 5 M⊕–2 M♃. The planets consist of a core made of iron, silicates, and ices surrounded by a H/He envelope, similar to the ice giants in the solar system. The luminosity includes the contribution from the cooling and contraction of the core and of the H/He envelope, as well as radiogenic decay. For the atmosphere we used grey, AMES-Cond, petitCODE, and HELIOS models. We considered solar and non-solar metallicities as well as cloud-free and cloudy atmospheres. The most important initial conditions, namely the core-to-envelope-mass ratio and the initial (i.e. post formation) luminosity are taken from planet formation simulations based on the core accretion paradigm. Results. We first compare our cooling curves for Uranus, Neptune, Jupiter, Saturn, GJ 436b, and a 5 M⊕ planet with a 1% H/He envelope with other evolutionary models. We then present the temporal evolution of planets with masses between 5 M⊕ and 2 M♃ in terms of their luminosity, effective temperature, radius, and entropy. We discuss the impact of different post formation entropies. For the different atmosphere types and initial conditions, magnitudes in various filter bands between 0.9 and 30 micrometer wavelength are provided. Conclusions. Using blackbody fluxes and non-grey spectra, we estimate the detectability of such planets with JWST. We found that a 20 (100) M⊕ planet can be detected with JWST in the background limit up to an age of about 10 (100) Myr with NIRCam and MIRI, respectively.

scholarly journals Composition of massive giant planets

2010 ◽  
Vol 6 (S276) ◽  
pp. 95-100
Author(s):  
Ravit Helled ◽  
Peter Bodenheimer ◽  
Jack J. Lissauer
Keyword(s):  
Large Range ◽  
Giant Planet ◽  
Giant Planets ◽  
Heavy Elements ◽  
Formation Model ◽  
The Core ◽  
Accretion Model ◽  
Low Mass ◽  
Core Accretion ◽  
Host Stars

AbstractThe two current models for giant planet formation are core accretion and disk instability. We discuss the core masses and overall planetary enrichment in heavy elements predicted by the two formation models, and show that both models could lead to a large range of final compositions. For example, both can form giant planets with nearly stellar compositions. However, low-mass giant planets, enriched in heavy elements compared to their host stars, are more easily explained by the core accretion model. The final structure of the planets, i.e., the distribution of heavy elements, is not firmly constrained in either formation model.

scholarly journals How planetary growth outperforms migration

2019 ◽  
Vol 622 ◽  
pp. A202 ◽  
Author(s):  
Anders Johansen ◽  
Shigeru Ida ◽  
Ramon Brasser
Keyword(s):  
Flux Ratio ◽  
Stokes Number ◽  
Giant Planets ◽  
Type I ◽  
Initial Size ◽  
Horizontal Migration ◽  
Gas Giant ◽  
Planetary Migration ◽  
Gas Accretion ◽  
Core Accretion

Planetary migration is a major challenge for planet-formation theories. The speed of type-I migration is proportional to the mass of a protoplanet, while the final decade of growth of a pebble-accreting planetary core takes place at a rate that scales with the mass to the two-thirds power. This results in planetary growth tracks (i.e., the evolution of the mass of a protoplanet versus its distance from the star) that become increasingly horizontal (migration dominated) with the rising mass of the protoplanet. It has been shown recently that the migration torque on a protoplanet is reduced proportional to the relative height of the gas gap carved by the growing planet. Here we show from 1D simulations of planet–disc interaction that the mass at which a planet carves a 50% gap is approximately 2.3 times the pebble isolation mass. Our measurements of the pebble isolation mass from 1D simulations match published 3D results relatively well, except at very low viscosities (α < 10−3) where the 3D pebble isolation mass is significantly higher, possibly due to gap edge instabilities that are not captured in 1D. The pebble isolation mass demarks the transition from pebble accretion to gas accretion. Gas accretion to form gas-giant planets therefore takes place over a few astronomical units of migration after reaching first the pebble isolation mass and, shortly after, the 50% gap mass. Our results demonstrate how planetary growth can outperform migration both during core accretion and during gas accretion, even when the Stokes number of the pebbles is small, St ~ 0.01, and the pebble-to-gas flux ratio in the protoplanetary disc is in the nominal range of 0.01–0.02. We find that planetary growth is very rapid in the first million years of the protoplanetary disc and that the probability for forming gas-giant planets increases with the initial size of the protoplanetary disc and with decreasing turbulent diffusion.

Formation of gas giant planets: core accretion models with fragmentation and planetary envelope

Icarus ◽  
2003 ◽  
Vol 166 (1) ◽  
pp. 46-62 ◽  
Author(s):  
S. Inaba ◽  
G.W. Wetherill ◽  
M. Ikoma
Keyword(s):  
Giant Planets ◽  
Gas Giant ◽  
Core Accretion

scholarly journals Unveiling the planet population at birth

2021 ◽  
Vol 503 (1) ◽  
pp. 1526-1542 ◽  
Author(s):  
James G Rogers ◽  
James E Owen
Keyword(s):  
Mass Distribution ◽  
Mass Fraction ◽  
Additional Mass ◽  
Core Mass ◽  
Water Ice ◽  
The Core ◽  
Core Composition ◽  
Peak Mass ◽  
Core Accretion ◽  
Atmospheric Mass

ABSTRACT The radius distribution of small, close-in exoplanets has recently been shown to be bimodal. The photoevaporation model predicted this bimodality. In the photoevaporation scenario, some planets are completely stripped of their primordial H/He atmospheres, whereas others retain them. Comparisons between the photoevaporation model and observed planetary populations have the power to unveil details of the planet population inaccessible by standard observations, such as the core mass distribution and core composition. In this work, we present a hierarchical inference analysis on the distribution of close-in exoplanets using forward models of photoevaporation evolution. We use this model to constrain the planetary distributions for core composition, core mass, and initial atmospheric mass fraction. We find that the core-mass distribution is peaked, with a peak-mass of ∼4M⊕. The bulk core-composition is consistent with a rock/iron mixture that is ice-poor and ‘Earth-like’; the spread in core-composition is found to be narrow ($\lesssim 16{{\ \rm per\ cent}}$ variation in iron-mass fraction at the 2σ level) and consistent with zero. This result favours core formation in a water/ice poor environment. We find the majority of planets accreted a H/He envelope with a typical mass fraction of $\sim 4{{\ \rm per\ cent}}$; only a small fraction did not accrete large amounts of H/He and were ‘born-rocky’. We find four times as many super-Earths were formed through photoevaporation, as formed without a large H/He atmosphere. Finally, we find core-accretion theory overpredicts the amount of H/He cores would have accreted by a factor of ∼5, pointing to additional mass-loss mechanisms (e.g. ‘boil-off’) or modifications to core-accretion theory.

scholarly journals Metallicity and Planet Formation: Models

2009 ◽  
Vol 5 (S265) ◽  
pp. 391-398
Author(s):  
Alan P. Boss
Keyword(s):  
Star Formation ◽  
Strong Correlation ◽  
Planet Formation ◽  
Protoplanetary Disks ◽  
Giant Planets ◽  
Heavy Elements ◽  
Doppler Spectroscopy ◽  
Gas Giant ◽  
Core Accretion ◽  
Gaseous Envelopes

AbstractPlanets typically are considerably more metal-rich than even the most metal-rich stars, one indication that planet formation must differ greatly from star formation. There is general agreement that terrestrial planets form by the collisional accumulation of solids composed of heavy elements in the inner regions of protoplanetary disks. Two competing mechanisms exist for the formation of giant planets, core accretion and disk instability, though hybrid combinations are possible as well. In core accretion, a higher metallicity in the protoplanetary disk leads directly to larger core masses and hence to more gas giant planets. Given the strong correlation of gas giant planets detected by Doppler spectroscopy with stellar metallicity, this has often been taken as proof that core accretion is the mechanism that forms giant planets. Recent work, however, implies that the formation of gas giants by disk instability can be enhanced by higher metallicities, though not as dramatically as for core accretion. In both scenarios, the ongoing accretion of planetesimals by gas giant protoplanets leads to strong enrichments of heavy elements in their gaseous envelopes. Both scenarios also imply that gas giant planets should have significant solid cores, raising questions for gas giant interior models without cores. Exoplanets with large inferred core masses seem likely to have formed by core accretion, while gas giants at distances beyond 20 AU seem more likely to have formed by disk instability. Given the wide variety of exoplanets found to date, it appears that both mechanisms are needed to explain the formation of the known population of giant planets.

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