| Discovery[1] | |
|---|---|
| Discovered by | LINEAR |
| Discovery site | Lincoln Lab ETS |
| Discovery date | 8 June 1999 |
| Designations | |
| (20461) Dioretsa | |
| Pronunciation | /daɪ.əˈrɛtsə/ |
Named after | Asteroid[2] (spelled backwards) |
| 1999 LD31 | |
| centaur[3] · damocloid[4] unusual[5] · distant[1] | |
| Symbol | .svg) (astrological) |
| Orbital characteristics[3] | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 2.54yr (927 d) |
| Aphelion | 45.404AU |
| Perihelion | 2.4021 AU |
| 23.903 AU | |
| Eccentricity | 0.8995 |
| 116.87 yr (42,686 d) | |
| 59.873° | |
| 0° 0m 30.24s / day | |
| Inclination | 160.43° |
| 297.77° | |
| 103.13° | |
| Jupiter MOID | 0.1907 AU |
| TJupiter | -1.5470 |
| Physical characteristics | |
| 14±3 km[4][6] | |
| 0.03±0.01[4][6] | |
| 13.8[1][3] | |
20461 Dioretsa/daɪ.əˈrɛtsə/ is acentaur anddamocloid on aretrograde,cometary-like orbit from theouter Solar System. It was discovered on 8 June 1999, by members of theLINEAR team at theLincoln Laboratory Experimental Test Site nearSocorro, New Mexico, United States.[1] The highly eccentricunusual object measures approximately 14 kilometers (8.7 miles) in diameter.[4][6] It was nameddioretsa, ananadrome of "asteroid".[1]
Dioretsa is a member of thedamocloids,[4] with aretrograde orbit and a negativeTJupiter of −1.547. It is also acentaur, as its orbit has asemi-major axis in between that ofJupiter (5.5 AU)Neptune (30.1 AU).[3] TheMinor Planet Center lists it as a critical object and (other)unusual minor planet due to anorbital eccentricity of more than 0.5.[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 aninclination of 160° with respect to theecliptic.[3] Itsobservation arc begins 12 months prior to its official discovery observation, with aprecovery image taken bySpacewatch atSteward Observatory in June 1998.[1] As of 2021[update], it was last observed in 2000 and its orbit still has anuncertainty of 2.[3]
Dioretsa is the firstdistant object with a retrograde orbit to be discovered, with1999 LE31. An inclination of greater than 90° means that a body moves in aretrograde orbit. Dioretsa's orbit is otherwise similar to that of acomet. This has led to speculation that Dioretsa was originally an object from theOort cloud.[7]
The minor planet's name "Dioretsa" is the word "asteroid" spelled backwards (ananadrome), and is the first numbered of currently 136 known (see Data Base Search of the Minor Planet Center)minor planets with a retrograde motion in theSolar System.[2] The approved naming citation was published by theMinor Planet Center on 1 May 2003 (M.P.C. 48396).[8]
According to observations made with the 10-meterKeck Telescope, Dioretsa measures 14 kilometers in diameter and its surface has a lowalbedo of 0.03.[6] It has anabsolute magnitude of 13.8.[3] As of 2018, Dioretsa'sspectral type as well as itsrotation period and shape remain unknown.[3][9]
