Xiangliu (moon)

Xiangliu, full designation 225088 Gonggong I Xiangliu, is the only known moon of the scattered-disc likely dwarf planet 225088 Gonggong. It was discovered by a team of astronomers led by Csaba Kiss during an analysis of archival Hubble Space Telescope images of Gonggong. The discovery team had suspected that the slow rotation of Gonggong was caused by tidal forces exerted by an orbiting satellite. Xiangliu was first identified in archival Hubble images taken with Hubble's Wide Field Camera 3 on 18 September 2010. Its discovery was reported and announced by Gábor Marton, Csaba Kiss, and Thomas Müller at the 48th Meeting of the Division for Planetary Sciences on 17 October 2016. The satellite is named after Xiangliu, a nine-headed venomous snake monster in Chinese mythology that attended the water god Gonggong as his chief minister. Following the March 2016 discovery that Gonggong was an unusually slow rotator, the possibility was raised that a satellite may have slowed it down via tidal forces. The indications of a possible satellite orbiting Gonggong led Csaba Kiss and his team to analyze archival Hubble observations of Gonggong. Their analysis of Hubble images taken on 18 September 2010 revealed a faint satellite orbiting Gonggong at a distance of at least . The discovery was announced on 17 October 2016, though the satellite was not given a proper provisional designation. The discovery team later also identified the satellite in earlier archival Hubble images taken on 9 November 2009. From follow-up Hubble observations in 2017, the absolute magnitude of the satellite is estimated to be at least 4.59 magnitudes dimmer than Gonggong, or 6.93 given Gonggong's estimated absolute magnitude of 2.34. Based on Hubble images of Gonggong and Xiangliu taken in 2009 and 2010, the discovery team constrained Xiangliu's orbital period to between 20 and 100 days. They better determined the orbit with additional Hubble observations in 2017. Xiangliu is believed to be tidally locked to Gonggong.