DPS 2001 meeting, November 2001
Session 25. Solar System Origins II
Oral, Chairs: M. Drake, H. Levison, Wednesday, November 28, 2001, 5:00-6:30pm, Regency GH

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[25.05] Gas-Assisted Capture of the Irregular Satellites of Jupiter

M. Cuk, J.A. Burns (Cornell U.)

Recent discoveries of ``irregular'' satellites about the giant planets have dramatically increased their number such that systematic studies of their origin can begin. Since irregulars move along large, inclined and eccentric orbits, capture from circumsolar orbit is usually suspected (Franklin and Colombo 1971, Heppenheimer and Porco 1977). Because permanent capture is not possible in a strictly gravitational three-body problem, a dissipative mechanism is needed. Many assume that gas drag by protojovian nebula led to their capture (cf. Pollack et al. 1979).

We numerically simulate the gas-aided capture of a planetesimal by Jupiter. The distribution and velocity of gas come from hydrocode simulations (Lubow et al. 1999). In our simple replication of their model, gas is assumed to follow gravitational trajectories, except at the shockwave fronts (taken from Lubow et al.) which the gas is forbidden to cross.

The planetesimal's motion is integrated using a mixture of modern and traditional techniques. We employ a symplectic integration algorithm (Malhotra 1994) within the circumsolar and circumjovian disks. In the transitional region we used a fourth-order Runge-Kutta integrator expressed in rotating coordinates. The method's timesteps are independent of the presence of the gas. Subsequent orbital evolution is handled in a symplectic way, thus avoiding ``fake captures'' due to energy leakage owing to integration errors.

By incorporating more sophisticated models of protoJupiter's environs, we hope to refine the nebular models and/or to elucidate the capture process. Preliminary results indicate that the parent body of the prograde cluster of Jovian irregulars (Himalia's group) may have originated from the Hilda region, at around 4 AU from the Sun. This is consistent with the taxonomical types of the cluster members (Sykes et al. 2000) being similar to those of Hildas that are close in size to Himalia (Dahlgren and Lagerkvist 1995).

The author(s) of this abstract have provided an email address for comments about the abstract: cuk@astro.cornell.edu

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