The Second Earth Trojan 2020 XL 5

Abstract

The Earth Trojans are coorbitals 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 follow-up 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 fifteenth century, and then it has a likelihood of 99.5% to leave the L 4 region within the next ∼10 kyr. Therefore, it is most likely that 2020 XL 5 is dynamically unstable over this timescale.