|Discovery site||Lincoln Lab ETS|
|Discovery date||8 June 1999|
|MPC designation||20461 Dioretsa|
|centaur · damocloid|
|Orbital characteristics |
|Epoch 31 July 2016 (JD 2457600.5)|
|Uncertainty parameter 2|
|Observation arc||2.54 yr (927 days)|
|116.32 yr (42,485 days)|
|0° 0m 30.6s / day|
|Jupiter MOID||0.1801 AU|
|Jupiter Tisserand parameter||-1.548|
|Dimensions||±3 km 14|
20461 Dioretsa, provisional designation 1999 LD31, is a distant minor planet classified as centaur, with a highly eccentric and retrograde orbit, approximately 14 kilometers in diameter. It was discovered 8 June 1999, by members of the Lincoln Near-Earth Asteroid Research (LINEAR) team at the U.S. Lincoln Laboratory Experimental Test Site, Socorro, New Mexico.
The centaur orbits the Sun at a distance of 2.4–45.2 AU once every 116 years and 4 months (42,485 days). Its orbit has an exceptional eccentricity of 0.90 and an outstanding inclination of 160° with respect to the plane of the ecliptic (greater than 90° means retrograde). Currently, its orbit has an uncertainty parameter value of 2. The first precovery was taken at Steward Observatory (Kitt Peak–Spacewatch) in 1998, extending the asteroid's observation arc by 1 year prior to its discovery. 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.
The minor planet's name "Dioretsa" is the word "asteroid" spelled backwards, and is the first numbered of currently more than 20 known minor planets with a retrograde motion in the Solar System. Naming citation was published on 1 May 2003 (M.P.C. 48396).
- "JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 12 April 2016.
- Schmadel, Lutz D. (2006). Dictionary of Minor Planet Names – (20461) Dioretsa, Addendum to Fifth Edition: 2003–2005. Springer Berlin Heidelberg. p. 152. ISBN 978-3-540-34360-8. Retrieved April 2016.
- Harris, Alan W.; Delbó, Marco; Binzel, Richard P.; Davies, John K.; Roberts, Julie; Tholen, David J.; et al. (October 2001). "Visible to Thermal-Infrared Spectrophotometry of a Possible Inactive Cometary Nucleus". Icarus 153 (2): 332–337. Bibcode:2001Icar..153..332H. doi:10.1006/icar.2001.6687. Retrieved April 2016.
- "20461 Dioretsa (1999 LD31)". Minor Planet Center. Retrieved April 2016.
- "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved May 2016.
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Asteroids and comets rotation curves, CdR – Observatoire de Genève, Raoul Behrend
- Discovery Circumstances: Numbered Minor Planets (20001)-(25000) – Minor Planet Center
- 20461 Dioretsa at the JPL Small-Body Database