Asteroid 2015 DB216: a recurring co-orbital companion to Uranus

TL;DR

This paper investigates asteroid 2015 DB216, revealing it as a temporary, recurring co-orbital companion to Uranus with complex dynamical behavior and implications for a larger population of similar objects.

Contribution

It is the first detailed dynamical study of asteroid 2015 DB216, demonstrating its status as a recurring co-orbital with Uranus and highlighting its unique secular behavior.

Findings

2015 DB216 is a transient co-orbital of Uranus.

It follows an asymmetric horseshoe orbit for at least 10 kyr.

The asteroid may remain in Uranus' co-orbital zone for millions of years.

Abstract

Minor bodies trapped in 1:1 co-orbital resonances with a host planet could be relevant to explain the origin of captured satellites. Among the giant planets, Uranus has one of the smallest known populations of co-orbitals, three objects, and all of them are short-lived. Asteroid 2015 DB216 has an orbital period that matches well that of Uranus, and here we investigate its dynamical state. Direct N-body calculations are used to assess the current status of this object, reconstruct its immediate dynamical past, and explore its future orbital evolution. A covariance matrix-based Monte Carlo scheme is presented and applied to study its short-term stability. We find that 2015 DB216 is trapped in a temporary co-orbital resonance with Uranus, the fourth known minor body to do so. A detailed analysis of its dynamical evolution shows that it is an unstable but recurring co-orbital companion to Uranus. It currently follows an asymmetric horseshoe trajectory that will last for at least 10 kyr, but it may remain inside Uranus' co-orbital zone for millions of years. As in the case of other transient Uranian co-orbitals, complex multibody ephemeral mean motion resonances trigger the switching between the various resonant co-orbital states. The new Uranian co-orbital exhibits a secular behaviour markedly different from that of the other known Uranian co-orbitals because of its higher inclination, nearly 38 degrees. Given its rather unusual discovery circumstances, the presence of 2015 DB216 hints at the existence of a relatively large population of objects moving in similar orbits.