Gonggong (dwarf planet)

Lore & Background

Gonggong was discovered on 17 July 2007 by American astronomers Megan Schwamb, Michael Brown, and David Rabinowitz at the Palomar Observatory as part of the Palomar Distant Solar System Survey. The discovery was announced in January 2009. Initially nicknamed 'Snow White' by Brown due to an assumption of white color, it was later found to be very red, likely from organic compounds called tholins. The object was the largest unnamed object in the Solar System until 2019, when its discoverers hosted an online poll for the public to choose a name; 'Gonggong' won with 46% of 280,000 votes. The name was accepted by the International Astronomical Union in February 2020.

Reader's Guide

Gonggong is significant as a large trans-Neptunian object that may be in hydrostatic equilibrium, qualifying it as a dwarf planet. Its highly eccentric and inclined orbit (eccentricity 0.50, inclination 30.9°) places it in a 3:10 orbital resonance with Neptune, meaning it completes three orbits for every ten of Neptune's. With a rotation period of about 22 hours—slow compared to similar objects—its spin may have been affected by tidal forces from its satellite, Xiangliu. The presence of water ice and possible methane on its surface suggests past cryovolcanic activity. As of 2026, it is the sixth-farthest known Solar System object, at 89.7 AU from the Sun, and is moving toward aphelion, which it will reach by 2134. Its red color and large size make it a key object for studying the outer Solar System's composition and dynamics.

Did You Know?

• Gonggong is approximately 1,230 km in diameter, similar in size to Pluto's moon Charon.
• It has a rotation period of around 22 hours, which is slow compared to other trans-Neptunian objects that typically rotate in less than 12 hours.
• The name Gonggong was chosen via an online public poll in 2019, beating out Holle and Vili.
• Gonggong is in a 3:10 orbital resonance with Neptune, completing three orbits for every ten of Neptune's.