http://arxiv.org/abs/1503.06805
We consider the formation of satellites around the Pluto-Charon binary. An early collision between the two partners likely produced the binary and a narrow ring of debris, out of which arose the moons — Styx, Nix, Kerberos and Hydra. Yet how the satellites emerged from the compact ring is uncertain. Here we show that a particle ring can spread from physical collisions and collective gravitational scattering, similar to migration. Around a binary, these processes take place in the reference frames of `most circular’ orbits, akin to circular ones in a Keplerian potential. Ring particles can damp to these orbits, avoiding destructive collisions. Damping and diffusion can also help particles survive dynamical instabilities driven by resonances with the binary. In some situations, particles get trapped near resonances that sweep outward with the tidal evolution of the Pluto-Charon binary. With simple models and numerical experiments, we show how the Pluto-Charon impact ring may have expanded into a broad disk, out of which grew the circumbinary moons. In some scenarios, the ring can spread well beyond the orbit of Hydra, the most distant moon, to form a handful of smaller satellites. If these small moons exist, New Horizons will find them.
B. Bromley and S. Kenyon
Wed, 25 Mar 15
18/38
Comments: 39 pages of text, 9 figures, submitted to ApJ
You must be logged in to post a comment.