On March 27, 2022, three UVA teams traveled to North Carolina to observe asteroid (15904) Polymele. Polymele is a Jupiter trojan asteroid and one of the targets of the NASA Lucy mission. Occultations by these mission target asteroids are extremely useful for pinpointing their locations and determining their shapes and sizes ahead of time. The more that we know about an asteroid before Lucy arrives, the better the Lucy team can plan Lucy’s flyby to target any interesting features an asteroid might have.

The three UVA teams joined 23 additional teams throughout the US to observe Polymele occulting a distant star. Mike Skrutskie took one telescope, Matt Nelson another, and student team Liam Walters and Becky Williams a third. The three teams loaded up the telescopes and drove from Charlottesville, Virginia to Rockingham, North Carolina, close to the border with South Carolina. The night was clear, and all three telescopes were lucky enough to observe a positive! Liam and Becky observed a “double hit” (meaning the star blinked out twice), suggesting that Polymele looks more like a peanut than a simple round ellipsoid. Together, the three UVA cords helped constrain the northern edge of the asteroid.

Over the next few days, analysis of all 23 teams’ data revealed an additional exciting find: two of the non-UVA teams had caught an occultation by a small satellite asteroid located about 200 km from Polymele! This satellite is too small and too close to Polymele to be observed with any method other than occultations, and the discovery prompted ongoing follow-up occultations to observe the satellite a second time. The goal is that Lucy will be able to visit both Polymele and its satellite when it flies by in 2027.