November 5, 1998 CfA Colloquium


Title: Disk-planet Interactions: Secular Resonance Damping

Speaker: Bill Ward

Abstract: Resonant interactions between a disk and an embedded or nearby secondary have played an important role in the shaping of disk structures and in evolving secondary orbits in both planetary and satellite systems. The role of satellite resonances in sculpting circumplanetary rings is well established, and disk torques exerted between a protoplanet by its precursor nebula have been suggested as responsible for the migration of some extrasolar planets into observed tight circumstellar orbits. This talk will examine another consequence of disk torques: the eccentricity evolution of a secondary. Of particular interest is the interaction at a secular resonance, where the apsidal precession rates of the secondary and the disk material match. The disk's collective response is to launch a one-armed spiral wave (apsidal wave) that is very open and couples well to the satellite potential. The resulting torque is greatly enhanced over that generated at mean motion resonances, and under certain conditions can quickly damp the secondary's orbital eccentricity. Applications to Neptune's interaction with the Kuiper belt, and to the orbital eccentricities of extrasolar planets will be discussed.

Reference for students: (Lunch on Friday at 1pm)