Simulating the Formation of Giant Planet Cores
Ironically, the most massive planets in the Solar System probably formed in the least amount of time. Jupiter and Saturn must have accreted their main constituents, hydrogen and helium, from the solar nebula before it dispersed in the first few million years.
In the widely accepted core accretion model of giant planet formation, a large solid planetary embryo of roughly 10 Earth masses had to form first, mainly by accretion of much smaller bodies called planetesimals. This was then followed by a period of inflow of nebular gas directly onto the growing core. Assembling such a large solid body so quickly, it turns out, offers some serious challenges to the current theory of planet formation.
We (Levison, Thommes, Capobianco and I) are undertaking the most comprehensive study of this problem to date, using numerical integrations of the orbits of a number of Earth mass planetary embryos embedded in a massive swarm of planetesimals. In these experiments we have included simplified models of several physical processes that have been suggested to solve the core accretion problem. We find that in most of the simulations, gravitational scattering leads to a wholesale redistribution of material and gap formation around embryos, limiting their growth. Almost all cases of large embryo growth were associated with self-sustaining outward planetesimal-driven migration. Implications for giant planet formation (including exoplanets) will be discussed.
Date: Thursday, 10 September 2009 Time: 11:30 Where: Université de Montréal Pavillon Roger-Gaudry, Local D-460 Contact: René Doyon