 2015 RR245 imaged by theHubble Space Telescope in October 2020 | |
| Discovery[1] | |
|---|---|
| Discovered by | OSSOS Michele T. Bannister et al.[2][3] |
| Discovery site | Mauna Kea Obs. |
| Discovery date | 9 September 2015 |
| Designations | |
| (523794)2015 RR245 | |
| TNO[4] · SDO · resonant(2:9)[3][5] p-DP[6] · distant[1] | |
| Orbital characteristics[4] | |
| Epoch 27 April 2019 (JD 2458600.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 13.10yr (4,786 d) |
| Earliestprecovery date | 15 October 2004 |
| Aphelion | 128.80AU |
| Perihelion | 33.943 AU |
| 81.373 AU | |
| Eccentricity | 0.5829 |
| 734.05 yr (268,113 d) | |
| 323.86° | |
| 0° 0m 4.68s / day | |
| Inclination | 7.5755° |
| 211.68° | |
| ≈ 21 August 2092[7] ±3 days | |
| 261.02° | |
| Knownsatellites | 0 |
| Physical characteristics | |
| ≈500 km[5] ≈630 km[6] 500–870 km assuming a single object[3] | |
| 0.12(assumed)[3] 0.11(assumed)[6] 0.135(assumed)[5] | |
| neutral g–r=0.59±0.11[3] | |
| 21.2 (perihelic)[8] | |
| 3.6±0.1(Hr)[3] 3.81[4] | |
(523794) 2015 RR245 is a largetrans-Neptunian object of theKuiper belt in the outermost regions of theSolar System. It was discovered on 9 September 2015, by theOuter Solar System Origins Survey atMauna Kea Observatories on the Big island of Hawaii, in the United States.[1] The object is in a rare2:9 resonance withNeptune and measures approximately 600 kilometers in diameter.
A firstprecovery of2015 RR245 was taken at theCerro Tololo Observatory in Chile on 15 October 2004.[1][4] It was first observed by a research team led byMichele Bannister while poring over images that theCanada–France–Hawaii Telescope inHawaii took in September 2015 as part of theOuter Solar System Origins Survey (OSSOS),[1][9][10] and later identified in images taken atSloan Digital Sky Survey andPan-STARRS between 2008 and 2016.[8] The discovery was formally announced in aMinor Planet Electronic Circular on 10 July 2016.[2]
Thisminor planet wasnumbered by theMinor Planet Center on 25 September 2018 (M.P.C. 111779).[11] As of 2025, it has not beennamed.[1]
As of 2018,2015 RR245 has a reasonably well defined orbit with anuncertainty of 3. It orbits theSun at a distance of 33.8–128.6 AU once every 731 years and 6 months (for reference,Neptune's orbit is at 30 AU). Its orbit has aneccentricity of 0.58 and aninclination of 8° with respect to theecliptic.[4]
2015 RR245 is among the most distant known Solar System objects. As of 2018, it is 63 AU from the Sun. It will make its closest approach to the Sun in 2093, when it will reach anapparent magnitude of 21.2.[4][8]
Additional precovery astrometry from the Sloan Digital Sky Survey and the Pan-STARRS1 survey shows that2015 RR245 is aresonant trans-Neptunian object, securely trapped in a 2:9mean motion resonance withNeptune, meaning that this minor planet orbits the Sun twice in the same amount of time it takes Neptune to complete 9 orbits.[3] The object is unlikely to have been trapped in the 2:9 resonance for the age of Solar System. It is much more likely that it has been hopping between various resonances and got trapped in the 2:9 resonance in the last 100 million years.[3]
Its exact size is uncertain, but the best estimate is around 670 km (420 mi) in diameter, assuming analbedo of 0.12 (within a wider range of 500 to 870 km, based on albedos of 0.21 to 0.07).[3] For comparison, Pluto, the largest object in the Kuiper belt, is about 2,374 km (1,475 mi) in diameter.[9][10] AstronomerMichael Brown assumes an albedo of 0.11 and calculates a diameter of 626 km,[6] whileJohnston's Archive gives a diameter of 500 kilometers for the primary and 275 km for the satellite, based on an assumed equal albedo of 0.135.[5]
Observations by theGemini North andCanada–France–Hawaii Telescope appeared to suggest the existence of anatural satellite or moon orbiting2015 RR245.[12][13] However, follow-up observations by the Gemini North andHubble Space Telescope in 2019 and 2020 did not detect the putative moon.[14]
| Consensus | _(cropped).jpg)  | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Candidate (for TNOs, D+1σ ≥ 700 km or H ≤ 4.0) |
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