Comparison of the physical properties of the L4 and L5 Trojan asteroids from ATLAS data

TL;DR

This study compares the physical properties of L4 and L5 Jupiter Trojan asteroids using ATLAS data, revealing shape differences likely caused by varying collision rates.

Contribution

It provides the first detailed comparison of shape distributions and color properties of L4 and L5 Trojans based on a large photometric dataset.

Findings

L4 Trojans are more elongated than L5 Trojans.

Shape differences are attributed to higher collision rates in L4.

Presented phase functions and colors for 266 objects.

Abstract

Jupiter has nearly 8000~known co-orbital asteroids orbiting in the L4 and L5 Lagrange points called Jupiter Trojan asteroids. Aside from the greater number density of the L4 cloud the two clouds are in many ways considered to be identical. Using sparse photometric data taken by the Asteroid Terrestrial-impact Last Alert System (ATLAS) for 863 L4 Trojans and 380 L5 Trojans we derive the shape distribution for each of the clouds and find that, on average, the L4 asteroids are more elongated than the L5 asteroids. This shape difference is most likely due to the greater collision rate in the L4 cloud that results from its larger population. We additionally present the phase functions and $c-o$ colours of 266~objects.