Gonggong was discovered in July 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory, and the discovery was announced in January 2009.

Gonggong was discovered by American astronomers Megan Schwamb, Michael Brown and David Rabinowitz on 17 July 2007.

[22] Gonggong is often accompanied by his minister, Xiangliu, a nine-headed poisonous snake monster who was also responsible for causing flooding and destruction.

[24][25] The nickname also fit because, by that time, Brown's team had discovered seven other large trans-Neptunian objects which were collectively referred to as the "seven dwarfs":[26] Quaoar in 2002, Sedna in 2003, Haumea, Salacia and Orcus in 2004, and Makemake and Eris in 2005.

[25][27] In 2011, he declared that he now had enough information to justify naming it, because of the discovery of water ice and the possibility of methane on its surface, which made it noteworthy enough to warrant further study.

[28][29] The three options were chosen because they were associated with water, ice, snow, and the color red—all characteristics of Gonggong—and because they had associated figures that could later provide a name for Gonggong's satellite.

[33] The symbol was designed by Denis Moskowitz, a software engineer in Massachusetts; it combines the Chinese character 共 gòng with a snake's tail.

[14] The period, inclination and eccentricity of Gonggong's orbit are all rather extreme compared to other large bodies in the Solar System.

[42] The Minor Planet Center and the Jet Propulsion Laboratory Small-Body Database assume a brighter absolute magnitude of 1.6 and 1.8, respectively,[1][3] which would make it the fifth brightest trans-Neptunian object.

[9] The surface composition and spectrum of Gonggong is expected to be similar to that of Quaoar, as both objects are red in color and display signs of water ice and possibly methane in their spectra.

[48][46] The reflectance spectrum of Gonggong was first measured in 2011 at near-infrared wavelengths, with the Folded port InfraRed Echellette (FIRE) spectrograph on the Magellan Baade Telescope at the Las Campanas Observatory in Chile.

[49] Additional photometric measurements from the Hubble Space Telescope's Wide Field Camera 3 instrument display similar absorption bands at 1.5 μm,[49] which are characteristic features of water ice, a substance often found on large Kuiper belt objects.

[49][10] Observations of Gonggong's near-infrared spectrum in 2015 revealed an absorption feature at 2.27 μm, indicating the presence of methanol along with its irradiation products on its surface.

[52] Gonggong is large enough to be able to retain trace amounts of volatile methane on its surface,[49] even when at its closest distance to the Sun (33.7 AU),[3] where temperatures are higher than that of Quaoar.

[49] In particular, the large size of Gonggong means that it is likely to retain trace amounts of other volatiles, including ammonia, carbon monoxide, and possibly nitrogen, which almost all trans-Neptunian objects lose over the course of their existence.

[53] The presence of tholins on the surface of Gonggong implies the possible existence of a tenuous methane atmosphere, analogous to Quaoar.

[55][59][7] Brown states that Gonggong "must be a dwarf planet even if predominantly rocky", based on the 2013 radiometric measurement of 1,290 km (800 mi).

[7] Scott Sheppard and colleagues think that it is likely to be a dwarf planet,[59] based on its minimum possible diameter—580 km (360 mi) under the assumption of a completely reflective surface with an albedo of 1[c]—and what was at the time the expected lower size limit of around 200 km (120 mi) for hydrostatic equilibrium in cold icy-rocky bodies.

[61] In 2010, astronomer Gonzalo Tancredi initially estimated Gonggong to have a very large diameter of 1,752 km (1,089 mi), though its dwarf planet status was unclear as there was no lightcurve data or other information to ascertain its size.

[55] Gonggong is too distant to be resolved directly; Brown placed a rough estimate of its diameter ranging from 1,000–1,500 km (620–930 mi), based on an albedo of 0.18 which was the best fit in his model.

Later observations in 2013 using combined thermal emission data from Herschel and the Spitzer Space Telescope suggested a smaller size of 1142+647−467 km (710+402−290 mi), though this estimate had a larger range of uncertainty.

[11][23] These observations of Gonggong were part of the Kepler spacecraft's K2 mission which includes studying small Solar System bodies.

[10] The small light curve amplitude of Gonggong indicates that it is being viewed at a pole-on configuration, further evidenced by the observed inclined orbit of its satellite.

[64] Their analysis of Hubble images taken on 18 September 2010 revealed a faint satellite orbiting Gonggong at a distance of at least 15,000 km (9,300 mi).

[64] On 5 February 2020 the satellite was officially named Xiangliu, after the nine-headed poisonous snake monster that accompanied Gonggong in Chinese mythology.

[1] It was calculated by planetary scientist Amanda Zangari that a flyby mission to Gonggong would take a minimum of over 20 years with current rocket capabilities.