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.

scholarly journals Rapid Formation of Gas-giant Planets via Collisional Coagulation from Dust Grains to Planetary Cores

2021 ◽  
Vol 922 (1) ◽  
pp. 16
Author(s):  
Hiroshi Kobayashi ◽  
Hidekazu Tanaka
Keyword(s):  
Protoplanetary Disks ◽  
Central Star ◽  
Giant Planets ◽  
Solar Systems ◽  
Evolution Path ◽  
Planetary Cores ◽  
Rapid Formation ◽  
Gas Giant ◽  
Planetary Migration ◽  
Gas Accretion

Abstract Gas-giant planets, such as Jupiter, Saturn, and massive exoplanets, were formed via the gas accretion onto the solid cores, each with a mass of roughly 10 Earth masses. However, rapid radial migration due to disk–planet interaction prevents the formation of such massive cores via planetesimal accretion. Comparably rapid core growth via pebble accretion requires very massive protoplanetary disks because most pebbles fall into the central star. Although planetesimal formation, planetary migration, and gas-giant core formation have been studied with a lot of effort, the full evolution path from dust to planets is still uncertain. Here we report the result of full simulations for collisional evolution from dust to planets in a whole disk. Dust growth with realistic porosity allows the formation of icy planetesimals in the inner disk (≲10 au), while pebbles formed in the outer disk drift to the inner disk and there grow to planetesimals. The growth of those pebbles to planetesimals suppresses their radial drift and supplies small planetesimals sustainably in the vicinity of cores. This enables rapid formation of sufficiently massive planetary cores within 0.2–0.4 million years, prior to the planetary migration. Our models shows the first gas giants form at 2–7 au in rather common protoplanetary disks, in agreement with the exoplanet and solar systems.

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 Evolusi Bintang pada Pembentukan Tata Surya dan Sistem Keplanetan

2016 ◽  
Vol 5 (2) ◽  
pp. 245
Author(s):  
Khilyatul Khoiriyah
Keyword(s):  
Star Formation ◽  
Solar System ◽  
Planetary Systems ◽  
Protoplanetary Disks ◽  
Early Evolution ◽  
Giant Planets

This research is the literature studies that provide an introduction to the theory of the formation and early evolution of solar system and planetary systems. Theories that discussed are limit on the theory which has been closed to the truth of observation result. Topics include the structure of solar system, star formation, the structure of evolution and dispersal of protoplanetary disks, planetesimals formation, terrestrial and giant planets formation, the formation of the smaller objects in the solar system and planet migration.Penelitian ini merupakan studi literatur yang membahas tentang masalah pembentukan dan evolusi awal tata surya dan sistem keplanetan dengan memberikan konsep dasar yang ringkas. Teori-teori yang dikaji secara khusus dibatasi pada teori yang telah mendekati kebenaran dari hasil pengamatan. Topik yang dibahas adalah struktur tata surya, pembentukan bintang, struktur evolusi dan pembubaran cakram protoplanet, pembentukan planetesimal, planet terestrial dan planet raksasa, pembentukan benda-benda kecil dalam tata surya dan migrasi planet.

scholarly journals Observational tests of planet formation models

2007 ◽  
Vol 3 (S249) ◽  
pp. 261-262
Author(s):  
A. Sozzetti ◽  
D. W. Latham ◽  
G. Torres ◽  
B. W. Carney ◽  
J. B. Laird ◽  
...  
Keyword(s):  
Planet Formation ◽  
Giant Planets ◽  
Evolutionary Models ◽  
Gas Giant

AbstractWe summarize the results of two experiments to address important issues related to the correlation between planet frequencies and properties and the metallicity of the hosts. Our results can usefully inform formation, structural, and evolutionary models of gas giant planets.

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.

scholarly journals Giant planet formation — a theoretical timeline

2004 ◽  
Vol 202 ◽  
pp. 167-174 ◽  
Author(s):  
Günther Wuchterl
Keyword(s):  
Star Formation ◽  
Solar System ◽  
Formation Process ◽  
Planet Formation ◽  
Giant Planet ◽  
Circumstellar Disks ◽  
Giant Planets ◽  
Low Mass ◽  
Star Formation Regions ◽  
Observational Techniques

Low mass circumstellar disks are a result of the star formation process. The growth of dust and solid planets in such pre-planetary disks determines many properties of our solar system. Models of the Solar System giant planets indicate an enrichment of heavy elements and imply heavy element cores. Detailed models therefore describe giant planet formation as a consequence of the formation of solid planets that have grown sufficiently large to permanently bind gas from the protoplanetary nebula. The diversity of Solar System and extrasolar giant planets is explained by variations in the core growth rates caused by a coupling of the dynamics of planetesimals and the contraction of the massive envelopes they dive into, as well as by changes in the hydrodynamical accretion behavior of the envelopes resulting from differences in nebula density, temperature and orbital distance. Detailed formation models are able to determine observables as luminosities, radii and effective temperatures of young giant planets. Present observational techniques do now allow to probe star formation regions at ages covering all evolutionary stages of the giant planet formation process.

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 Effect of pebble flux-regulated planetesimal formation on giant planet formation

2020 ◽  
Vol 642 ◽  
pp. A75 ◽  
Author(s):  
Oliver Voelkel ◽  
Hubert Klahr ◽  
Christoph Mordasini ◽  
Alexandre Emsenhuber ◽  
Christian Lenz
Keyword(s):  
Ad Hoc ◽  
Planet Formation ◽  
Giant Planet ◽  
Circumstellar Disks ◽  
Giant Planets ◽  
Radial Density ◽  
Density Distributions ◽  
Gas Giant ◽  
Self Gravity ◽  
Dust Evolution

Context. The formation of gas giant planets by the accretion of 100 km diameter planetesimals is often thought to be inefficient. A diameter of this size is typical for planetesimals and results from self-gravity. Many models therefore use small kilometer-sized planetesimals, or invoke the accretion of pebbles. Furthermore, models based on planetesimal accretion often use the ad hoc assumption of planetesimals that are distributed radially in a minimum-mass solar-nebula way. Aims. We use a dynamical model for planetesimal formation to investigate the effect of various initial radial density distributions on the resulting planet population. In doing so, we highlight the directive role of the early stages of dust evolution into pebbles and planetesimals in the circumstellar disk on the subsequent planet formation. Methods. We implemented a two-population model for solid evolution and a pebble flux-regulated model for planetesimal formation in our global model for planet population synthesis. This framework was used to study the global effect of planetesimal formation on planet formation. As reference, we compared our dynamically formed planetesimal surface densities with ad hoc set distributions of different radial density slopes of planetesimals. Results. Even though required, it is not the total planetesimal disk mass alone, but the planetesimal surface density slope and subsequently the formation mechanism of planetesimals that enables planetary growth through planetesimal accretion. Highly condensed regions of only 100 km sized planetesimals in the inner regions of circumstellar disks can lead to gas giant growth. Conclusions. Pebble flux-regulated planetesimal formation strongly boosts planet formation even when the planetesimals to be accreted are 100 km in size because it is a highly effective mechanism for creating a steep planetesimal density profile. We find that this leads to the formation of giant planets inside 1 au already by pure 100 km planetesimal accretion. Eventually, adding pebble accretion regulated by pebble flux and planetesimal-based embryo formation as well will further complement this picture.

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