ORBITAL RESONANCES AND POYNTING-ROBERTSON DRAG

Grains orbiting a star experience orbital decay due to Poynting-Robertson drag and can become trapped in commensurability resonances with a planet. We examine conditions for trapping in the circular restricted three-body problem, and derive criteria for trapping in terms of the radiation pressure factor β, planetary mass, resonance location, and the grain's orbital eccentricity. These analytic criteria show good agreement with results of three-body orbital integrations and more elaborate multiplanet simulations by other researchers. We show that resonances under Poynting-Robertson drag are "metastable" because trapped grains inevitably acquire eccentricities large enough to cause their orbits to cross that of the planet. © 1993 by Academic Press, Inc.