A Uranian Trojan and the frequency of temporary giant-planet co-orbitals

TL;DR

This paper reports the discovery of a Uranian Trojan, analyzes its orbital stability, and estimates the frequency and duration of temporary co-orbital captures among giant planets based on a Centaur model.

Contribution

It presents the first confirmed Uranian Trojan and provides a statistical estimate of temporary co-orbital objects among giant planets.

Findings

A Uranian Trojan was detected and remains stable for over 70 kyr.

Approximately 0.4% of the Centaur population are Uranian co-orbitals at any time.

The co-orbital fraction among Centaurs aligns with predictions from transneptunian source models.

Abstract

Trojan objects share a planet's orbit, never straying far from the triangular Lagrangian points, 60 degrees ahead of (L4) or behind (L5) the planet. We report the detection of a Uranian Trojan; in our numerical integrations, 2011 QF99 oscillates around the Uranian L4 Lagrange point for >70 kyr and remains co-orbital for ~1 Myr before becoming a Centaur. We constructed a Centaur model, supplied from the transneptunian region, to estimate temporary co-orbital capture frequency and duration (to factor of two accuracy), finding that at any time 0.4% and 2.8% of the population will be Uranian and Neptunian co-orbitals, respectively. The co-orbital fraction (~2.4%) among Centaurs in the IAU Minor Planet Centre database is thus as expected under transneptunian supply.