Gas Disks to Gas Giants: Simulating the Birth of Planetary Systems

Abstract

The ensemble of now more than 250 discovered planetary systems displays a wide range of masses, orbits and in multiple systems, dynamical interactions.These represent the endpoint of a complex sequence of events, wherein an entire protostellar disk converts itself into a small number of planetary bodies.Here we present self-consistent numerical simulations of this process, which produce results in agreement with some of the key trends observed in the properties of the exoplanets. Analogues to our own Solar System do not appear to be common, originating from disks near the boundary between barren and (giant) planet-forming.Gas giant planets form within 1-10 million years (Myrs), during the time that their parent star possesses a gas disk (1). Two-and three-dimensional hydrodynamic simulations of planets embedded in protostellar disks are, due to their computational cost, limited to following a maximum of 10 3 − 10 4 orbits; even for a planet as far out as Jupiter (orbital period 11 years), this amounts to at most a tenth of a protostellar disk's total lifetime. For this reason, 1

Extrasolar planet population synthesis

“…The only difference that is probably significant occurs for the mass distribution, with the more eccentric planets being more massive. Such a correlation among the known extrasolar planets was already pointed out some time ago by Marcy et al (2005), and can indeed be explained by planet-planet interactions: More massive disks produce more massive planets, and in higher numbers, leading to stronger scattering and therefore higher eccentricities, a behavior that is seen in the simulations of Thommes et al (2008). This effect is even strengthened by the fact that in planet-planet interactions, the less massive bodies tend to be ejected.…”

“…(1) The evolution of a planet may be significantly altered by the presence of another (massive) planet (Alibert et al 2005b(Alibert et al , 2006Thommes et al 2008). In contrast, we follow the evolution of just one embryo per disk (Paper I), and therefore do not use any exoplanet that is a member of a known extrasolar planetary system.…”

“…Our selection criteria in particular exclude planets which probably underwent strong planet-planet interactions (criteria 1 and 5). Thommes et al (2008) have shown that disks which lead to the formation of just one giant gaseous planet might only represent a very specific class of all planet-forming disks, namely those near the threshold for giant planet formation. When the mass of the disk is well above the threshold, prolific giant planet formation could, in contrast, occur.…”

Trapping in three-planet resonances during gas-driven migration

“…In order to be able to evaluate the probability of capture in a given triple resonance, its stability time (compared to the discevaporation time scale) and its efficiency in exciting the inclinations, we need to resort to more advanced models of migration -e.g. the one used in Thommes et al (2008) -that take into account variations in the gas surface density induced by the relative motion of the planets, as well as gas dissipation. We hope to be able to report on these issues in a forthcoming paper.…”

“…Only a few works investigated the combined action of disc torques and planet-planet scattering (e.g. Adams & Laughlin 2003, Moorhead & Adams 2005, Thommes, Matsumura & Rasio 2008, Matsumura et al 2010. However, an unstable crowded system -the starting point of typical planet-planet scattering simulations -is not the unique result of formation in a gas-disc, since resonant interactions during the gas phase should lead to stable resonant systems, such as the ones observed (e.g.…”