Nongravitational Forces in Planetary Systems

Abstract Nongravitational forces play surprising and, sometimes, centrally important roles in shaping the motions and properties of small planetary bodies. In the solar system, the morphologies of comets, the delivery of meteorites, and the shapes and dynamics of asteroids and binaries are all affected by nongravitational forces. In exoplanetary systems and debris disks, nongravitational forces affect the lifetimes of circumstellar particles and feed refractory debris to the photospheres of the central stars. Unlike the gravitational force, which is a simple function of the well-known separations and masses of bodies, the nongravitational forces are frequently functions of poorly known or even unmeasurable physical properties. Here, we present order-of-magnitude descriptions of nongravitational forces, with examples of their application.