Evolution of Primordial Kuiper Belt Binaries Through a Giant Planet Instability

Abstract

The non-resonant Kuiper belt objects (KBOs) between the 3:2 and 2:1 Neptunian mean motion resonances can be largely divided between a cold classical belt (CCB) and a hot classical belt (HCB). A notable difference between these two subpopulations is the prevalence of widely spaced, equal-mass binaries in the CCB and a much smaller but non-zero number in the HCB. The primary reason for this difference in binary rate remains unclear. Here using N-body simulations we examine whether close encounters with the giant planets during an early outer solar system instability may have disrupted primordial Kuiper Belt binaries that existed within the primordial Kuiper belt before they attained HCB orbits. We find that such encounters are very effective at disrupting binaries down to separations of ~1% of their Hill radius (as measured in the modern Kuiper belt), potentially explaining the paucity of widely spaced, equal mass binaries in the modern HCB. Moreover, we find that the widest binaries observed in the modern HCB are quite unlikely to survive planetary encounters, but these same planetary encounters can widen a small subset of tighter binaries to give rise to the small population of very wide binaries seen in today's HCB.

arXiv commentAccepted 2021 April 28. Received 2021 April 26; in original form 2021 February 22. 5 pages, 3 figures, 2 tables

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Cited by in corpus (3)

• Dynamical Implantation of Blue Binaries in the Cold Classical Kuiper Belt
• A Non-Primordial Origin for the Widest Binaries in the Kuiper Belt
• Considering contact forces during the formation of planetesimals by gravitational collapse: mutual orbits, spin states, and shapes