Image by G. Bacon of STScI - NASA
|Orbit type||Kuiper belt|
|Semimajor axis||43.37 AU|
|Orbital period||288 Years|
|Discoverer||C. Trujillo & M. Brown, 2002|
Quaoar ("kwah-oh-ahr", /kwA o Ar/) is a Trans-Neptunian object circling the Sun in the Kuiper belt, discovered in 2002 by astronomers Chad Trujillo and Mike Brown at the California Institute of Technology in Pasadena, California.
Quaoar is estimated to have a diameter of about 1,280 kilometres, which would make it the largest Solar System object discovered since Pluto and, indeed, the largest known minor planet. Larger than all the asteroids put together, it is about one tenth the diameter of Earth or one third the diameter of the Moon. It orbits at about 6 billion kilometres from the Sun with an orbital period of 288 years.
The planetoid's name follows International Astronomical Union rules by naming all planetoids after creation deities (see planetary nomenclature). "Quaoar" is the name of a creation deity of the Native American Tongva people, native to the area around Los Angeles, where the discovery was named (see Quaoar (deity)).
The IAU has voted and approved the name Quaoar, which is now its official name; there is also the systematic name "2002 LM60".
The discovery weakens Pluto's case to be counted as a planet, since astronomers expect that there may be as many as a dozen Kuiper Belt objects the size of Quaoar. Some expect to find other planetoids there as large or larger than Pluto. In some ways, Quaoar has more claim to be a planet than Pluto does: it has a more planetary orbit (a near-circular orbit with a radius of somewhat over 40 AU rather than a highly eccentric one like Pluto) and doesn't belong to a binary system with mass ratio more akin to a binary asteroid, of which many are known.
Quaoar belongs to the Kuiper belt, a class of comet like icy objects orbitting beyond Neptune, pristine remnants from the solar nebula with much knowledge to yield. It is believed to be a mixture of rock and ice, like the other Kuiper Belt objects; however its extremely low albedo (estimated at 0.1) indicates that the ice has disappeared from its outer layers. Until the Pluto Express or a similar mission is approved, our knowledge of these worlds will remain vague.