An interstellar origin for Jupiter's retrograde co-orbital asteroid

TL;DR

This paper presents evidence that asteroid (514107) 2015 BZ509 has been in its current retrograde orbit since the Solar System's formation, suggesting an interstellar origin and indicating the presence of more extrasolar asteroids in our Solar System.

Contribution

It demonstrates that asteroid (514107) 2015 BZ509 is a primordial interstellar object captured into the Solar System, a finding not explained by existing planet formation models.

Findings

(514107) 2015 BZ509 has been in its current orbit since Solar System formation.

The asteroid was captured from the interstellar medium 4.5 billion years ago.

More extrasolar asteroids likely exist in the Solar System on nearly-polar orbits.

Abstract

Asteroid (514107) 2015 BZ509 was discovered recently in Jupiter's co-orbital region with a retrograde motion around the Sun. The known chaotic dynamics of the outer Solar System have so far precluded the identification of its origin. Here, we perform a high-resolution statistical search for stable orbits and show that asteroid (514107) 2015 BZ509 has been in its current orbital state since the formation of the Solar System. This result indicates that (514107) 2015 BZ509 was captured from the interstellar medium 4.5 billion years in the past as planet formation models cannot produce such a primordial large-inclination orbit with the planets on nearly-coplanar orbits interacting with a coplanar debris disk that must produce the low-inclination small-body reservoirs of the Solar System such as the asteroid and Kuiper belts. This result also implies that more extrasolar asteroids are currently present in the Solar System on nearly-polar orbits.