The Upcoming Mutual Event Season for the Patroclus - Menoetius Trojan Binary

Published in 2016: Icarus 305, 198-202.

W.M. Grundy1, K.S. Noll2, M.W. Buie3, and H.F. Levison3.

(1) Lowell Observatory, Flagstaff AZ 86001.

(2) NASA Goddard Space Flight Center, Greenbelt MD 20771.

(3) Southwest Research Institute, Boulder CO 80302.


We present new Hubble Space Telescope and ground-based Keck observations and new Keplerian orbit solutions for the mutual orbit of binary Jupiter Trojan asteroid (617) Patroclus and Menoetius, targets of NASA's Lucy mission. We predict event times for the upcoming mutual event season, which is anticipated to run from late 2017 through mid 2019.

Fig. 1. Schematic diagram of selected Patroclus - Menoetius mutual events. Patroclus is the larger body and Menoetius is the smaller one with the arrow indicating its motion relative to Patroclus over 6 hours. The hatched region is the shadow of the foreground object at the distance of the background object. The top row shows examples of "inferior" events, when Menoetius occults (blocks the view of) or eclipses (casts its shadow onto) Patroclus. The bottom row shows "superior" events, when Patroclus occults or eclipses Menoetius. The 2018 March and 2019 April events coincide with dark time near opposition, making them convenient to observe from a single observatory, if it is located at a suitable longitude. But more information can be derived from a sample of events covering as much of the season as possible. Examples of especially rich events include those of 2018 June, where occultation and eclipse components are well-separated in time and distinct in depth, resulting in highly asymmetric event lightcurves.

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