Constraints on the Orbital Evolution of Triton

TL;DR

This paper investigates Triton's orbital evolution, emphasizing the role of Kozai oscillations, and suggests a rapid evolution scenario involving debris from satellite collisions, contrasting with traditional tidal models.

Contribution

It introduces a new orbital evolution model for Triton that accounts for Kozai oscillations and satellite debris interactions, challenging previous long timescale tidal theories.

Findings

Kozai oscillations significantly affect Triton's orbit.

Triton's orbital evolution likely occurred in less than 10^5 years.

Satellite debris interactions can explain the rapid orbital evolution.

Abstract

We present simulations of Triton's post-capture orbit that confirm the importance of Kozai-type oscillations in its orbital elements. In the context of the tidal orbital evolution model, these variations require average pericenter distances much higher than previously published, and the timescale for the tidal orbital evolution of Triton becomes longer than the age of the Solar System. Recently-discovered irregular satellites present a new constraint on Triton's orbital history. Our numerical integrations of test particles indicate a timescale for Triton's orbital evolution to be less than $10^5$ yrs for a reasonable number of distant satellites to survive Triton's passage. This timescale is inconsistent with the exclusively tidal evolution (time scale of $>10^8$ yrs), but consistent with the interestion with the debris from satellite-satellite collisions. Any major regular satellites will quickly collide among themselves after being perturbed by Triton, and the resulting debris disk would eventually be swept up by Triton; given that the total mass of the Uranian satellite system is 40% of that of Triton, large scale evolution is possible. This scenario could have followed either collisional or the recently-discussed three-body-interaction-based capture.