Capture of irregular satellites via binary planetesimal exchange reactions in migrating planetary systems

Abstract

By logging encounters between planetesimals and planets, we compute the distribution of encounters in a numerically integrated two‐planet system that is migrating due to interactions with an exterior planetesimal belt. Capture of an irregular satellite in orbit about a planet through an exchange reaction with a binary planetesimal is only likely when the binary planetesimal undergoes a slow and close encounter with the planet. Taking care to consider where a planet‐orbit‐crossing binary planetesimal would first be tidally disrupted, we estimate the probability of both tidal disruption and irregular satellite capture. We estimate that the probability that the secondary of a binary planetesimal is captured and becomes an irregular satellite about a Neptune mass outer planet is about 1/100 for binaries with masses and separations similar to transneptunian planetesimal binaries. Scaling functions are given allowing probabilities to be estimated for satellite capture from binary planetesimals with other masses, mass ratios and separations. This capture probability is only weakly dependent upon the binary's tidal disruption radius. We find that the probability that a satellite is captured by the inner planet is one to two orders of magnitude lower than by the outer planet. If young exoplanetary debris discs contain a population of binary planetesimals, then an outwards migrating outer planet should host a recently captured irregular satellite population.

COLLISIONAL CASCADE CALCULATIONS FOR IRREGULAR SATELLITE SWARMS IN FOMALHAUT b

“…Despite its broad success, the model does not address several interesting issues in the time evolution of irregular satellites. In current theory, planets capture material from a circumstellar disk to supply the circumplanetary swarm (e.g., Koch & Hansen 2011;Quillen et al 2012;Gaspar et al 2013;Nesvorný et al 2014). If some captured objects have r > r max , these objects may accrete material from the swarm and reduce the lifetime of smaller particles considerably.…”

Satellite capture mechanism in a sun-planet-binary four-body system

“…The capture probability of the minor member of the binary is much greater than that of the major member (Gaspar et al 2011). The distribution of the encounters two-planet system that is migrating due to interactions with an exterior planetesimal belt was numerically integrated (Quillen et al 2012). They focused on the different performances between the inner planet and outer planet on the probability that a satellite is captured, and the probability of the irregular satellites are captured due to binary exchange is predicted, and the planetesimal binaries similar to those in the Kuiper belt would have a probability of 1/100 captured by an outer migrating planet.…”