Pluto in Glory: Discovery of its Huge Opposition Surge

Observations of the Pluto Charon system were captured with the Palomar High Angular Resolution Observer (PHARO) adaptive optics system on the 200-inch Hale telescope during the historically small solar phase angles in 2018-2019. Both objects exhibit large opposition surges of ~30-35% in the last half degree of solar phase angle, which is larger than that observed for icy moons and other Kuiper Belt Objects. The size of the surge may be due to a unique surface texture caused by ongoing geologic processes or active volatile transport. These observations enable accurate determination of Pluto’s geometric albedo in the JHK filter system, which we find to be 0.84±0.04, 0.59±0.05, and 0.40±0.04 for Pluto, respectively, and 0.68±0.03 for Charon in the J-filter.