MEGASIM: Distribution and Detection of Earth Trojan Asteroids

TL;DR

This study uses high-resolution N-body simulations to map Earth Trojan Asteroids, evaluate their detectability in upcoming surveys, and conclude that stable ETAs are rare and unlikely to be detected on billion-year timescales.

Contribution

The paper provides the first high-resolution spatial distribution maps of Earth Trojan Asteroids and assesses their detectability in current and future astronomical surveys.

Findings

Stable ETAs are unlikely on billion-year timescales due to the Yarkovsky Effect.

Null detections from ZTF and LSST will significantly limit the estimated ETA population.

A twilight ETA survey could increase observations but not detection likelihood.

Abstract

Using N-body simulation results from the MEGASIM dataset, we present spatial distributions of Earth Trojan Asteroids and assess the detectability of the population in current and next-generation ground-based astronomical surveys (Yeager & Golovich 2022). Our high-fidelity Earth Trojan Asteroid (ETA) distribution maps show never-before-seen high-resolution spatial features that evolve over timescales up to 1 Gyr. The simulation was synchronized to start times and timelines of two observational astronomy surveys, 1) the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST) and 2) the Zwicky Transient Facility (ZTF). We calculate upper limits for the number of ETAs potentially observable with both the ZTF and LSST surveys. Due to the Yarkovsky Effect, we find no stable ETAs on billion year timescales likely to be detected by any ETA survey, as no C-type or S-type ETAs (with $H<22$ and $H<24$, respectively) are likely to be stable on billion year timescales, and ETAs large enough to remain stable on billion year timescales are very rare relative to the rest of the ETA population. We find that a twilight ETA survey will not drastically increase the likelihood of individual ETA detection, but would provide orders of magnitude more observations of select ETA populations. The null detection to date from ZTF restricts the potential ETA population to hundreds of objects larger than 100 meters (at $H\approx22$, Lifset et al. 2021), while a null detection by LSST will further restrict the ETA population to tens of objects larger than 100 meters.