This article is about the trans-Neptunian object. For the Tongva god, see Quaoar (deity).

50000 Quaoar

Discovery
Discoverer	Chadwick A. Trujillo, Michael E. Brown
Discovery Date	June 4, 2002
Alternate Designations	2002 LM60
Category	Kuiper belt
Orbital Elements Epoch October 22, 2004 (JD 2453300.5)
Eccentricity (e)	0.034
Semi-Major Axis (a)	6493.296 Gm (43.405 AU)
Perihelion (q)	6270.316 Gm (41.914 AU)
Aphelion (Q)	6716.275 Gm (44.896 AU)
Orbital Period (P)	104449.918 d (285.97 a)
Mean Orbital Speed	4.52 km/s
Inclination (i)	7.983°
Longitude of the Ascending Node (Ω)	188.791°
Argument of Perihelion (ω)	154.850°
Mean Anomaly (M)	273.737°
Physical Characteristics
Dimensions	989 - 1346 km
Mass	1.0-2.6×1021 kg
Density	2.0? g/cm³
Surface Gravity	0.276-0.376 m/s²
Escape Velocity	0.523-0.712 km/s
Rotation Period	? d
Spectral Class	?
Absolute Magnitude	2.6
Albedo	0.10
Mean Surface Temperature	~58 K

50000 Quaoar (pronounced KWA-o-ar, /"kwA o Ar/) [1] http://www.gps.caltech.edu/~chad/quaoar is a Trans-Neptunian object orbiting the Sun in the Edgeworth-Kuiper belt. It was discovered on June 4, 2002 by astronomers Chadwick A. Trujillo and Michael E. Brown at the California Institute of Technology in Pasadena, California from images acquired by Palomar Observatory using the JPL Near Earth Asteroid Tracking program. This discovery was announced on October 7, 2002, at a meeting of the American Astronomical Society. The earliest precovery turned out to be a July 17, 1982 plate from the Siding Spring Observatory 1.2 m telescope.

Quaoar is estimated to have a diameter of about 1,200 kilometres, which at the time of discovery made it the largest object found in the solar system since Pluto and, indeed, then the largest known minor planet (although the newly discovered 90377 Sedna has now surplanted it). More massive than all of 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 286 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. The IAU approved the name Quaoar, making it the official name; it also has the systematic name 2002 LM₆₀.

The discovery weakens Pluto's case to be classed as a planet, since astronomers expect that there may be as many as a dozen Kuiper Belt objects the size of Quaoar. Or it may require a change to the definition of planet to include Pluto, Quaoar, and Sedna. Some expect to find planetoids larger than Pluto. In some ways, Quaoar has more claim to be a planet than Pluto does: it has a more typical planetary orbit (a near-circular orbit with a radius of somewhat over 40 AU rather than a highly eccentric one like Pluto's). Like Neptune, Quaoar's orbit lies between Pluto's perihelion and aphelion, so that Pluto is closer to the Sun than Quaoar at some times of its year, and farther at others.

Quaoar is believed to be a mixture of rock and ice, like other Kuiper Belt Objects; however its extremely low albedo (estimated at 0.1) indicates that the ice has disappeared from its outer layers. After the New Horizons mission visits Pluto (in 2015) and goes on to visit several Kuiper Belt Objects our knowledge of such things should greatly improve.

In 2004, scientists were surprised to find signs of crystaline ice on Quaoar, indicating that the temperature rose to at least -260 degrees Fahrenheit sometime in the last ten million years. Speculation began as to what could have caused Quaoar to heat up from its natural temperature of -360 degrees. Some have theorized that a barrage of mini-meteors may have raised the temperature, but the most discussed theory speculates that volcanic activity may be occurring, spurred by the decay of radioactive elements within Quaoar's core.

External links

• Quaoar discoverers' webpage http://www.gps.caltech.edu/~chad/quaoar/
• Astronomers Contemplate Icy Volcanoes in Far Places http://www.nytimes.com/2004/12/09/science/09ice.html?ex=1260334800&en=9326ec
  dbb6f20b0a&ei=5090&partner=rssuserland* - New York Times article
• An article in an Australian science magazine http://www.theage.com.au/articles/2002/10/07/1033538894512.html
• An article in National Geographic http://news.nationalgeographic.com/news/2002/10/1003_021007_quaoar.html
• Volcanoes oon Quaoar CNN.com http://www.cnn.com/2004/TECH/space/12/08/volcano.neptune/index.html