On the existence of a comet belt beyond Neptune

An analysis of the possible existence of a comet belt in connection with the origin of the short-period comets is presented. It is predicted that solid conglomerates up to about 10 to the 18th g were formed by gravitational instabilities in the belt region; a subsequent fragmentation-accretion process led to a power-law mass distribution similar to that observed in the asteroids. Close encounters between members of the belt have provoked the diffusion of some of them so that they became subject to the strong perturbations of Neptune. The influence of close encounters between belt comets is studied in relation to the diffusion of their orbits using a Monte Carlo method. It is concluded that if such a belt contains members with masses equal to or greater than that of Ceres, the orbital diffusion could proceed rapidly enough to maintain the number of observed short-period comets in a steady state.