20461 Dioretsa

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20461 Dioretsa
Discovery [1]
Discovered by LINEAR
Discovery site Lincoln Lab ETS
Discovery date 8 June 1999
MPC designation (20461) Dioretsa
Pronunciation /d.əˈrɛtsə/
Named after
(spelled backwards)[2]
1999 LD31
centaur[1] · damocloid[citation needed]
Orbital characteristics[1]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 2
Observation arc 2.54 yr (927 days)
Aphelion 45.283 AU
Perihelion 2.4105 AU
23.847 AU
Eccentricity 0.8989
116.45 yr (42,535 days)
0° 0m 30.6s / day
Inclination 160.42°
Jupiter MOID 0.1849 AU
Jupiter Tisserand parameter -1.5490
Physical characteristics
Dimensions 14±3 km[3]

20461 Dioretsa (dy-ə-RET-sə), 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.[3][4]

The centaur orbits the Sun at a distance of 2.4–45.3 AU once every 116 years and 5 months (42,535 days). Its orbit has an eccentricity of 0.90 and an inclination of 160° with respect to the ecliptic.[1] An inclination greater than 90° means that a body moves in a retrograde orbit. Currently, its orbit has an uncertainty parameter value of 2.[1] The first precovery was taken at Steward Observatory (Kitt Peak–Spacewatch) in 1998, extending Dioretsa's observation arc by 1 year prior to its discovery.[4] 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.[2] Naming citation was published on 1 May 2003 (M.P.C. 48396).[5]


  1. ^ a b c d e f "JPL Small-Body Database Browser: 20461 Dioretsa (1999 LD31)" (2000-12-29 last obs.). Jet Propulsion Laboratory. Retrieved 3 December 2016. 
  2. ^ a b 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 4 April 2016. 
  3. ^ a b c 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 4 April 2016. 
  4. ^ a b "20461 Dioretsa (1999 LD31)". Minor Planet Center. Retrieved 4 April 2016. 
  5. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 20 May 2016. 

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