Trans-Neptunian object · Dwarf-planet candidate (scattered disc) · orbits Sun
Gonggong is a deep-red world of the scattered disc and one of the largest Solar System bodies never visited by a spacecraft. Known for over a decade only as 2007 OR10, it was finally named in 2019 after a public vote, for a Chinese water god with a serpent’s tail who was blamed for floods and for tilting the Earth.
Its moon Xiangliu is named for the nine-headed serpent minister of the water god Gonggong.
It is among the reddest large objects known, with methane frost on a tholin-stained icy surface.
Its eccentric orbit swings from ~33 AU, inside Pluto’s mean distance, out to just over 100 AU.
A moon that slowed a world down
Most bodies of Gonggong’s size spin in well under half a day, but Gonggong turns once in about 22 hours - one of the slowest rotations measured in the Kuiper belt region. The likely brake is its small moon Xiangliu: over billions of years, tides raised between the pair drained away spin, the same process that long ago locked our own Moon to Earth.
Physical characteristics
Diameter
1,230 km
Mass
1.750e+21 kg
Rotation period
22.4 h
Geometric albedo
0.14
Known moons
1
Atmosphere and composition
Atmosphere
None detected.
Composition
Water ice with methane frost, coloured deep red by radiation-processed organics (tholins).
Discovery
Discovered by
Megan Schwamb, Mike Brown & David Rabinowitz
Year
2007
How
Palomar Distant Solar System Survey (designated 2007 OR10)