20461 Dioretsa
20461 Dioretsa is a centaur and damocloid on a retrograde, cometary-like orbit from the outer Solar System. It was discovered on 8 June 1999, by members of the LINEAR team at the Lincoln Laboratory Experimental Test Site near Socorro, New Mexico, United States. The highly eccentric unusual object measures approximately in diameter. It was named "Dioretsa", the word "asteroid" spelled backwards. Classification and orbit. "Dioretsa" is a member of the damocloids, with a retrograde orbit and a negative T of −1.547. It is also a centaur, as its orbit has a semi-major axis in between that  of Jupiter (5.5 AU) Neptune (30.1 AU). The Minor Planet Center lists it as a critical object and (other) unusual minor planet due to an orbital eccentricity of more than 0.5. It orbits the Sun at a distance of 2.4–45.4 AU once every 116 years and 10 months (42,686 days; semi-major axis of 23.9 AU). Its orbit has an eccentricity of 0.90 and an inclination of 160° with respect to the ecliptic. Its observation arc begins 12 months prior to its official discovery observation, with a precovery taken by Spacewatch at Steward Observatory in June 1998. , it was  last observed in 2000 and its orbit still has an uncertainty of 2. Retrograde orbit. An inclination of greater than 90° means that a body moves in a retrograde orbit. "Dioretsa"s orbit is otherwise similar to that of a comet. This has led to speculation that "Dioretsa" was originally an object from the Oort cloud. Naming. The minor planet's name "Dioretsa" is the word "asteroid" spelled backwards, and is the first numbered of currently 99 known minor planets with a retrograde motion in the Solar System. The approved naming citation was published by the Minor Planet Center on  1 May 2003 (). Physical characteristics. According to observations made with the 10-meter Keck Telescope, "Dioretsa" measures 14 kilometers in diameter and its surface has a low albedo of 0.03. It has an absolute magnitude of 13.8. As of 2018, "Dioretsa"s spectral type as well as its rotation period and shape remain unknown.