scholarly journals Flux-limited Diffusion Approximation Models of Giant Planet Formation by Disk Instability. II. Quadrupled Spatial Resolution

2021 ◽  
Vol 923 (1) ◽  
pp. 93
Author(s):  
Alan P. Boss
Keyword(s):  
Spatial Resolution ◽  
Planet Formation ◽  
Gravitational Instability ◽  
Three Dimensional ◽  
Giant Planet ◽  
3D Models ◽  
New Models ◽  
Gas Giant ◽  
Limited Diffusion ◽  
Approximation Models

Abstract While collisional accumulation is nearly universally accepted as the formation mechanism of rock and ice worlds, the situation regarding gas giant planet formation is more nuanced. Gas accretion by solid cores formed by collisional accumulation is the generally favored mechanism, but observations increasingly suggest that gas disk gravitational instability might explain the formation of at least the massive or wide-orbit gas giant exoplanets. This paper continues a series aimed at refining three-dimensional (3D) hydrodynamical models of disk instabilities, where the handling of the gas thermodynamics is a crucial factor. Boss (2017, 2021) used the β cooling approximation to calculate 3D models of disks with initial masses of 0.091 M ⊙ extending from 4 to 20 au around 1 M ⊙ protostars. Here we employ 3D flux-limited diffusion (FLD) approximation models of the same disks, in order to provide a superior treatment of disk gas thermodynamics. The new models have quadrupled spatial resolution compared to previous 3D FLD models, in both the radial and azimuthal spherical coordinates, resulting in the highest spatial resolution 3D FLD models to date. The new models continue to support the hypothesis that such disks can form self-gravitating, dense clumps capable of contracting to form gas giant protoplanets, and suggest that the FLD models yield similar numbers of clumps as β cooling models with β ∼ 1 to ∼10, including the critical value of β = 3 for fragmentation proposed by Gammie.

scholarly journals Modes of Gaseous Planet Formation

2004 ◽  
Vol 202 ◽  
pp. 141-148 ◽  
Author(s):  
Alan P. Boss
Keyword(s):  
Planet Formation ◽  
Gravitational Instability ◽  
Giant Planet ◽  
Solid Core ◽  
New Era ◽  
Advantages And Disadvantages ◽  
Nearby Stars ◽  
Formation And Evolution ◽  
Gas Giant ◽  
Core Accretion

The discovery of gas giant planets around nearby stars has launched a new era in our understanding of the formation and evolution of planetary systems. However, none of the over four dozen companions detected to date strongly resembles Jupiter or Saturn: their inferred masses range from sub-Saturn-mass to 10 Jupiter-masses or more, while their orbits extend from periods of a few days to a few years. Given this situation, it seems prudent to re-examine mechanisms for gas giant planet formation. The two extreme cases are top-down or bottom-up. The latter is the core accretion mechanism, long favored for our Solar System, where a roughly 10 Earth-mass solid core forms by collisional accumulation of planetesimals, followed by hydrodynamic accretion of a gaseous envelope. The former is the long-discarded disk instability mechanism, where the protoplanetary disk forms self-gravitating, gaseous protoplanets through a gravitational instability of the gas, accompanied by settling and coagulation of dust grains to form solid cores. Both of these mechanisms have a number of advantages and disadvantages, making a purely theoretical choice between them difficult at present. Observations should be able to decide the dominant mechanism by dating the epoch of gas giant planet formation: core accretion requires more than a million years to form a Jupiter-mass planet, whereas disk instability is much more rapid.

scholarly journals ELEMENTAL ABUNDANCE DIFFERENCES IN THE 16 CYGNI BINARY SYSTEM: A SIGNATURE OF GAS GIANT PLANET FORMATION?

2011 ◽  
Vol 740 (2) ◽  
pp. 76 ◽  
Author(s):  
I. Ramírez ◽  
J. Meléndez ◽  
D. Cornejo ◽  
I. U. Roederer ◽  
J. R. Fish
Keyword(s):  
Binary System ◽  
Planet Formation ◽  
Giant Planet ◽  
Elemental Abundance ◽  
System A ◽  
Gas Giant

Planet Formation

2018 ◽  
Author(s):  
Morris Podolak
Keyword(s):  
Planet Formation ◽  
Giant Planet ◽  
Terrestrial Planet ◽  
Interstellar Space ◽  
Normal Density ◽  
Main Question ◽  
Primitive Form ◽  
The Core ◽  
Gas Giant ◽  
Time Required

Modern observational techniques are still not powerful enough to directly view planet formation, and so it is necessary to rely on theory. However, observations do give two important clues to the formation process. The first is that the most primitive form of material in interstellar space exists as a dilute gas. Some of this gas is unstable against gravitational collapse, and begins to contract. Because the angular momentum of the gas is not zero, it contracts along the spin axis, but remains extended in the plane perpendicular to that axis, so that a disk is formed. Viscous processes in the disk carry most of the mass into the center where a star eventually forms. In the process, almost as a by-product, a planetary system is formed as well. The second clue is the time required. Young stars are indeed observed to have gas disks, composed mostly of hydrogen and helium, surrounding them, and observations tell us that these disks dissipate after about 5 to 10 million years. If planets like Jupiter and Saturn, which are very rich in hydrogen and helium, are to form in such a disk, they must accrete their gas within 5 million years of the time of the formation of the disk. Any formation scenario one proposes must produce Jupiter in that time, although the terrestrial planets, which don’t contain significant amounts of hydrogen and helium, could have taken longer to build. Modern estimates for the formation time of the Earth are of the order of 100 million years. To date there are two main candidate theories for producing Jupiter-like planets. The core accretion (CA) scenario supposes that any solid materials in the disk slowly coagulate into protoplanetary cores with progressively larger masses. If the core remains small enough it won’t have a strong enough gravitational force to attract gas from the surrounding disk, and the result will be a terrestrial planet. If the core grows large enough (of the order of ten Earth masses), and the disk has not yet dissipated, then the planetary embryo can attract gas from the surrounding disk and grow to be a gas giant. If the disk dissipates before the process is complete, the result will be an object like Uranus or Neptune, which has a small, but significant, complement of hydrogen and helium. The main question is whether the protoplanetary core can grow large enough before the disk dissipates. A second scenario is the disk instability (DI) scenario. This scenario posits that the disk itself is unstable and tends to develop regions of higher than normal density. Such regions collapse under their own gravity to form Jupiter-mass protoplanets. In the DI scenario a Jupiter-mass clump of gas can form—in several hundred years which will eventually contract into a gas giant planet. The difficulty here is to bring the disk to a condition where such instabilities will form. Now that we have discovered nearly 3000 planetary systems, there will be numerous examples against which to test these scenarios.

scholarly journals THE LAST GASP OF GAS GIANT PLANET FORMATION: ASPITZERSTUDY OF THE 5 Myr OLD CLUSTER NGC 2362

2009 ◽  
Vol 698 (1) ◽  
pp. 1-27 ◽  
Author(s):  
Thayne Currie ◽  
Charles J. Lada ◽  
Peter Plavchan ◽  
Thomas P. Robitaille ◽  
Jonathan Irwin ◽  
...  
Keyword(s):  
Planet Formation ◽  
Giant Planet ◽  
Gas Giant

A hybrid scenario for gas giant planet formation in rings

Icarus ◽  
2005 ◽  
Vol 173 (2) ◽  
pp. 417-424 ◽  
Author(s):  
R DURISEN ◽  
K CAI ◽  
A MEJIA ◽  
M PICKETT
Keyword(s):  
Planet Formation ◽  
Giant Planet ◽  
Gas Giant

scholarly journals TW Hya: an old protoplanetary disc revived by its planet

2020 ◽  
Author(s):  
Sergei Nayakshin ◽  
Takashi Tsukagoshi ◽  
Cassandra Hall ◽  
Allona Vazan ◽  
Ravit Helled ◽  
...  
Keyword(s):  
Planet Formation ◽  
Gravitational Instability ◽  
Giant Planet ◽  
Emission Feature ◽  
Time Dependent ◽  
Dust Particles ◽  
Dark Ring ◽  
Build Time ◽  
Core Accretion ◽  
Protoplanetary Discs

Abstract Dark rings with bright rims are the indirect signposts of planets embedded in protoplanetary discs. In a recent first, an azimuthally elongated AU-scale blob, possibly a planet, was resolved with ALMA in TW Hya. The blob is at the edge of a cliff-like rollover in the dust disc rather than inside a dark ring. Here we build time-dependent models of TW Hya disc. We find that the classical paradigm cannot account for the morphology of the disc and the blob. We propose that ALMA-discovered blob hides a Neptune mass planet losing gas and dust. We show that radial drift of mm-sized dust particles naturally explains why the blob is located on the edge of the dust disc. Dust particles leaving the planet perform a characteristic U-turn relative to it, producing an azimuthally elongated blob-like emission feature. This scenario also explains why a 10 Myr old disc is so bright in dust continuum. Two scenarios for the dust-losing planet are presented. In the first, a dusty pre-runaway gas envelope of a ∼40 M⊕ Core Accretion planet is disrupted, e.g., as a result of a catastrophic encounter. In the second, a massive dusty pre-collapse gas giant planet formed by Gravitational Instability is disrupted by the energy released in its massive core. Future modelling may discriminate between these scenarios and allow us to study planet formation in an entirely new way – by analysing the flows of dust and gas recently belonging to planets, informing us about the structure of pre-disruption planetary envelopes.

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