title: Migrating planets
abstract: A planet orbiting in a disk of planetesimals can experience an instability in which it migrates to smaller orbital radii. Resonant interactions between the planet and planetesimals remove angular momentum from the planetesimals, increasing their eccentricities. Subsequently, the planetesimals either collide with or are ejected by the planet, reducing the semimajor axis of the planet. If the surface density of the planetesimals exceeds a critical value, corresponding to approximately 0.03 solar mass of gas inside the orbit of Jupiter, the planet will migrate inward a large distance. This instability may explain the presence of Jupiter-mass objects in small orbits around nearby stars.
authors.affiliation: N. Murray, B. Hansen, M. Holman, Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8, Canada. S. Tremaine, Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3.
authors.initials: N
authors.lastname: Murray
authors.initials: B
authors.lastname: Hansen
authors.initials: M
authors.lastname: Holman
authors.initials: S
authors.lastname: Tremaine