Dynamical environment in the triple asteroid system 87 Sylvia

Abstract

We investigate the dynamical environment in the first announced triple asteroid system 87 Sylvia. The 3D shape of the primary is rebuilt from shape data using the polyhedral model method. The dynamical characteristics of the primary, such as the surface height, the surface effective potential, the surface gravitational acceleration, the structure of the zero-velocity surfaces, and the locations and stability of the equilibrium points, have been investigated. Five equilibrium points are in the potential of 87 Sylvia. Both unstable periodic orbits and stable periodic orbits coexist near the surface of the primary of the triple asteroid system 87 Sylvia. Under the full perturbation force of two moonlets, the semi-major axis, the eccentricity, the inclination, and the mechanical energy vary periodically and have no secular terms. Among them, the semi-major axis, the eccentricity, and the mechanical energy have two period terms, namely, a long period term and a short period term; the inclination has three period terms, i.e., a long period term, a short period term, and an intermediate period term. Unlike these orbital parameters, the argument of the pericenter and the longitude of the ascending node have a secular term, a long period term and a short period term. A simulation of the trajectories of 1000 grains generated in the system considering the gravity of the irregular shape and two moonlets of the primary has been presented. The grains may impact on the surface of the primary, escape the system, or move in the system.