DDA 33rd Meeting, Mt. Hood, OR, April 2002
Session 12. Protoplanetary Disks
Tuesday, April 23, 2002, 4:20-6:00pm

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[12.04] The Effect of Dissipating Gas Disk on Terrestrial Planet Formation

J. Kominami, S. Ida (Tokyo Institute of Technology)

We have performed N-body simulation on final accretion stage of terrestrial planets, including the effect of damping of eccentricity and inclination caused by tidal interaction with a remnant gas disk. About twenty Mars-sized protoplanets would be formed in nearly circular orbits with orbital separation of several to ten Hill radius through runway and oligarchic growth. The orbits of the protoplanets would be eventually destabilized by long term mutual gravity and/or secular resonance of giant gaseous planets. The protoplanets would They eventually start orbital crossing and coalesce with each other to form terrestrial planets. Previous N-body simulations, however, showed that the final eccentricities of planets are around 0.1, which are about 10 times higher than the present eccentricities of Earth and Venus.

In most runs, the damping time scale, which is equivalent to the strength of the drag force, is kept constant throughout each run in order to clarify the effects of the damping.

If the damping time scale is factor times ten million years, which may correspond to a mostly depleted disk (0.01 - 0.1 of surface density of the minimum mass model), some protoplanets can grow to about the size of Earth and Venus, and the eccentricities of such surviving planets can be diminished within the disk lifetime.

We also carried out several runs with time-dependent drag force according to depletion of a gas disk. In these runs, we used exponential decay model with e-folding time of 3 million years. In this disk decay model, a gas disk with 0.1 to 0.01 orbital crossing and accretial events, which is enough to damp the eccentricities of the Earth-sized planets to the order of 0.01. Using these results, we discuss a possible scenario for the last stage of terrestrial planet formation.

The author(s) of this abstract have provided an email address for comments about the abstract: kominami@geo.titech.ac.jp

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Bulletin of the American Astronomical Society, 34, #3
© 2002. The American Astronomical Society.