The orbit and density of the Jupiter Trojan satellite system Eurybates-Queta

TL;DR

This study uses Hubble observations to determine the orbit, mass, and density of the Jupiter Trojan asteroid Eurybates and its satellite Queta, providing insights into the composition and collisional history of Trojan asteroids.

Contribution

First detailed orbital and density measurements of the Eurybates-Queta system, revealing its low density and implications for Trojan asteroid composition.

Findings

Queta orbits Eurybates at 2350 km with an 82.46-day period.

Eurybates density estimated at 1.1 g/cm^3, similar to other Trojans.

Eurybates is part of a collisional family, indicating typical Trojan composition.

Abstract

We report observations of the Jupiter Trojan asteroid (3548) Eurybates and its satellite Queta with the Hubble Space Telescope and use these observations to perform an orbital fit to the system. Queta orbits Eurybates with a semimajor axis of $2350\pm11$ km at a period of $82.46\pm0.06$ days and an eccentricity of $0.125\pm0.009$. From this orbit we derive a mass of Eurybates of $1.51\pm0.03 \times 10^{17}$ kg, corresponding to an estimated density of $1.1\pm0.3$ g cm$^{-3}$, broadly consistent with densities measured for other Trojans, C-type asteroids in the outer main asteroid belt, and small icy objects from the Kuiper belt. Eurybates is the parent body of the only major collisional family among the Jupiter Trojans; its low density suggests that it is a typical member of the Trojan population. Detailed study of this system in 2027 with the Lucy spacecraft flyby should allow significant insight into collisional processes among what appear to be the icy bodies of the Trojan belt.