Physics 901 Colloquium (Internal to Department)

Sleeping in on the Third Day: Oligarchic Chaos in the Terrestrial Region During the Mid to Late Transition

Doug McNeil
Dept. of Physics, Queen's University

Time
Tue. March 25, 2003     11:30 AM     Stirling A

Abstract

A standard model for terrestrial planet formation has emerged, divided into several phases. The middle phase begins with planetary embryos (~100-1000 km in radius) embedded in a field of smaller planetesimals. Gravitational focusing and dynamical friction combine to create a runaway growth mode where the growth of the largest body is much greater than that of the second largest. As the planetesimal field is accreted, the system moves to an oligarchic phase, where the evolution is of the system is dominated by a handful of large bodies. Dynamical friction decreases and the random velocity of the embryos increases, turning off runaway growth. The embryos then perturb each other into crossing orbits and merge to form terrestrial planets. The models, both semianalytic-statistical and N-body, produce systems like our own, but often with fewer planets, too widely spaced, too massive, and with too large random velocities. We have developed a parallel close-encountering mixed-variable symplectic integrator based upon Swift-SyMBA (Duncan, Levison, and Lee 1998) to bridge the gap between studies of the middle phase (which poorly resolve close encounters, and often neglect distant interactions) and late phase (which typically ignore the remnant planetesimal disc). Preliminary results will be discussed.

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