Gonggong (dwarf planet)

Gonggong is a distant dwarf planet located in the scattered disc. This is a region of space found far beyond the planet Neptune.

It is currently the sixth-farthest known object in our Solar System. Gonggong is quite large, with a diameter of approximately 1,930 kilometers. This size makes it similar to Charon, which is Pluto's moon. Because of its large mass, it may be in hydrostatic equilibrium. This means it has enough gravity to pull itself into a spherical shape.

The orbit of Gonggong is very extreme compared to most planets. It has a high orbital inclination of 30.9 degrees. This means its path is tilted significantly relative to the ecliptic plane. Its orbit is also highly eccentric, with a measured value of 0.50. This eccentricity causes its distance from the Sun to change greatly. At aphelion, its furthest point, it is very far away. At perihelion, its closest point, it is much nearer. Gonggong last reached perihelion in 1857 and will reach aphelion by 2134.

Gonggong exists in a 3:10 orbital resonance with Neptune. This means Gonggong completes exactly three orbits for every ten orbits Neptune completes.

A single trip around the Sun takes Gonggong about 547 years. This orbital period is the third-longest among likely dwarf planets. It is longer than the periods of Haumea and Makemake. However, it is much shorter than the 11,400-year period of Eris. This complex relationship with Neptune helps define its place in the scattered disc.

American astronomers discovered Gonggong in July 2007. Megan Schwamb, Michael Brown, and David Rabinowitz found it at the Palomar Observatory.

They used the Samuel Oschin telescope as part of a larger survey. Schwamb identified the object using a technique called blinking. This involved comparing different images to find moving objects. The discovery was part of Schwamb's doctoral thesis. The team officially announced the find in January 2009. At first, Brown nicknamed the object "Snow White." He thought it might be white like the icy Haumea family. However, observations later showed the object was actually very red.

The surface of Gonggong is notably red in color. This color likely comes from organic compounds called tholins. These tholins form when solar radiation and cosmic rays hit methane on the surface. This process is known as photolysis. Scientists also found water ice on the surface. This suggests that cryovolcanism occurred in the distant past. Cryovolcanism is when water erupts from the interior and freezes on the surface. Gonggong is also large enough to potentially hold a tenuous atmosphere of methane. It may even retain other volatiles like ammonia or nitrogen.

Naming the dwarf planet involved the general public. In 2019, the discoverers held an online poll with three choices. The options were Gonggong, Holle, and Vili. These names were related to water, ice, and red colors. The name Gonggong won with 46 percent of the 280,000 votes.

It is named after a Chinese water god. In mythology, Gonggong was a figure associated with floods and chaos. The name was officially accepted in early 2020. The object also has a natural satellite named Xiangliu. The tidal forces from Xiangliu may cause Gonggong to rotate slowly. It takes about 22 hours to complete one rotation.

Gonggong is a significant object for studying the outer Solar System. Its brightness is ranked as the seventh-brightest trans-Neptunian object. It has an absolute magnitude of 2.34. Because it is 88 AU from the Sun, it is too dim for the naked eye. Its study helps astronomers understand how objects in the scattered disc behave. The presence of methanol and water ice provides clues about its history. By studying Gonggong, scientists learn more about the chemical building blocks of our solar system.