Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p43b1433d&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P43B-1433
Physics
[6200] Planetary Sciences: Solar System Objects
Scientific paper
Gennaro D'Angelo (gennaro.dangelo@nasa.gov) NASA Ames Research Center and University of California, Santa Cruz Planetesimal Accretion during Runaway Gas Growth of Giant Planets The presence of regular and irregular satellites around Jupiter and Saturn likely involved accretion of planetesimals from a dissipating Solar Nebula. A gas giant planet undergoes a phase of rapid gas accretion once its envelope has outgrown its solid core. During this phase, gas accretion rates are dictated by the ability of the surrounding disk to supply gas to the planet's vicinity rather than by the thermodynamics of the planet's envelope. The rapid planet's growth is accompanied by an expansion of the planet's feeding zone, from which planetesimals may continue to be captured. The presence of gas in the disk aids the capture process by dissipating kinetic energy and removing orbital angular momentum from planetesimals. We perform 3D hydrodynamical simulations of a giant planet undergoing runaway gas accretion in a disk whose unperturbed gas surface density and temperature at ≈ 5 AU are ≈ 100 g cm-2 and ≈ 100 K, respectively. The simulations resolve the gas flow within the planet Roche lobe over length scales of ˜ 0.01 Hill radii (RH) and follow the growth of the planet from ≈ 50 Earth masses to about one Jupiter mass. Tidal interactions between a disk and an embedded planet of a few tenths of a Jupiter's mass perturb the disk's gas and produces an annular gap in the surface density distribution. We integrate the trajectories of 106 planetesimals that interact with the disk via gas drag. The planetesimal radii range from 100 m to 100 km. A significant fraction of the initial planetesimals' population tends be in or close to mean-motion resonances with the growing planet. The coorbital regions around Lagrangian points L4 and L5 are mostly populated with planetesimals of size larger than ˜ 1 km. Smaller, ˜ 100 m-size planetesimals are more strongly affected by gas drag, and tend to be more easily captured within the planet's Roche lobe that do larger planetesimals. However, these smaller bodies are also efficiently accreted by the planet. Similar fractions of the planetesimal population residing within ˜ RH/2 of the planet are of bodies with radii ˜ 10 km and ˜ 100 km. Orbital inclinations of these captured planetesimals are smaller than ˜ 70o.
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