The Second Earth Trojan 2020 XL$_{5}$

TL;DR

This paper reports the discovery and dynamical analysis of asteroid 2020 XL5 as a new Earth Trojan, revealing its recent capture and likely short-term stability, with implications for understanding Earth Trojan populations.

Contribution

The study provides the first confirmed dynamical characterization of asteroid 2020 XL5 as an Earth Trojan, including its capture history and stability assessment through N-body simulations.

Findings

2020 XL5 confirmed as a new Earth Trojan.

Likely captured in the 15th century.

Has a 99.5% chance to leave the L4 region within 10 kyr.

Abstract

The Earth Trojans are co-orbitals librating around the Lagrange points $L_4$ or $L_5$ of the Sun-Earth system. Although many numerical studies suggest that they can maintain their dynamical status and be stable on timescales up to a few tens of thousands of years or even longer, they remain an elusive population. Thus far only one transient member (2010 TK$_7$) has been discovered serendipitously. Here, we present a dynamical study of asteroid 2020 XL$_5$. With our meticulous followup astrometric observations of the object, we confirmed that it is a new Earth Trojan. However, its eccentric orbit brings it close encounters with Venus on a frequent basis. Based on our N-body integration, we found that the asteroid was captured into the current Earth Trojan status in the 15th century, and then it has a likelihood of 99.5% to leave the $L_4$ region within the next $\sim$10 kyr. Therefore, it is most likely that 2020 XL$_5$ is dynamically unstable over this timescale.