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(523794) 2015 RR245

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(523794) 2015 RR245, provisional designation 2015 RR245, is a trans-Neptunian object and possible dwarf planet from the Kuiper belt in the outermost regions of the Solar System. It was discovered on 14 September 2010, by Pan-STARRS at Haleakala Observatory on the island of Maui, Hawaii, in the United States.[1] The object stays in a rare 2:9 resonance with Neptune and measures approximately 700 kilometers in diameter, which likely makes it large enough to be round.

(523794) 2015 RR245
2015 RR245.gif
Orbital diagram of 2015 RR245
Discovery [1]
Discovered byPan-STARRS 1
Discovery siteHaleakala Obs.
Discovery date15 June 2010
MPC designation(523794) 2015 RR245
TNO[2] · resonant (2:9)[3][4]
p-DP[5] · distant[1]
Orbital characteristics[2]
Epoch 27 April 2019 (JD 2458600.5)
Uncertainty parameter 3
Observation arc13.10 yr (4,786 d)
Earliest precovery date15 October 2004
Aphelion128.80 AU
Perihelion33.943 AU
81.373 AU
734.05 yr (268,113 d)
0° 0m 4.68s / day
Physical characteristics
Mean diameter
649 km[5]
670 km[3]
770 km[4]
0.11 (assumed)[5]
0.12 (assumed)[3]
0.09 (assumed)[4]
21.2 (perihelic)[6]
3.6±0.1 (Hr)[3]



A first precovery of 2015 RR245 was taken at the Cerro Tololo Observatory in Chile on 15 October 2004.[1][2] It was first observed by a research team while poring over images that the Canada–France–Hawaii Telescope in Hawaii took in September 2015 as part of the Outer Solar System Origins Survey (OSSOS),[1][7][8] and later identified in images taken at Sloan Digital Sky Survey and Pan-STARRS between 2008 and 2016.[6]

Numbering and namingEdit

This minor planet was numbered by the Minor Planet Center on 25 September 2018 (M.P.C. 111779).[9] As of 2018, it has not been named.[1]

Orbit and classificationEdit

(523794) 2015 RR245's orbit librating in a 2:9 resonance with Neptune

As of 2018, 2015 RR245 has a reasonably well defined orbit with an uncertainty of 4. It orbits the Sun 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 an eccentricity of 0.58 and an inclination of 8° with respect to the ecliptic.[2]

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 an apparent magnitude of 21.2.[2][6]

2:9 resonanceEdit

Additional precovery astrometry from the Sloan Digital Sky Survey and the Pan-STARRS1 survey shows that 2015 RR245 is a resonant trans-Neptunian object, securely trapped in a 2:9 mean motion resonance with Neptune, 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]

Distribution of trans-Neptunian objects. Objects occupying the stronger resonances are in red.

Physical characteristicsEdit

Diameter and albedoEdit

Its exact size is uncertain, but the best estimate is around 670 km (420 mi) in diameter, assuming an albedo of 0.21.[3] For comparison, Pluto, the largest object in the Kuiper belt, is about 2,374 km (1,475 mi) in diameter.[7][8] Astronomer Michael Brown assumes an albedo of 0.11 and calculates at diameter of 649 kilometers, while the Johnston's Archive gives a diameter of 770 kilometers, based on an assumed albedo of 0.09.[4][5]


  1. ^ a b c d e f g "523794 (2015 RR245)". Minor Planet Center. Retrieved 9 October 2018.
  2. ^ a b c d e f "JPL Small-Body Database Browser: 523794 (2015 RR245)" (2017-11-22 last obs.). Jet Propulsion Laboratory. Retrieved 9 October 2018.
  3. ^ a b c d e f g Bannister, Michele T.; Alexandersen, Mike; Benecchi, Susan D.; Chen, Ying-Tung; Delsanti, Audrey; Fraser, Wesley C.; et al. (December 2016). "OSSOS. IV. Discovery of a Dwarf Planet Candidate in the 9:2 Resonance with Neptune". The Astronomical Journal. 152 (6): 8. arXiv:1607.06970v2. Bibcode:2016AJ....152..212B. doi:10.3847/0004-6256/152/6/212.
  4. ^ a b c d "List of Known Trans-Neptunian Objects". Johnston's Archive. 30 September 2018. Retrieved 2 October 2018.
  5. ^ a b c d e Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 30 July 2017.
  6. ^ a b c Weryk, R.J.; Lilly, E.; Chastel, S.; Denneau, L.; Jedicke, R.; Magnier, E.; Wainscoat, R.J.; Chambers, K.; Flewelling, H.; Huber, M.E.; Waters, C. (17 July 2016). "Distant Solar System Objects identified in the Pan-STARRS1 survey". arXiv:1607.04895 [astro-ph.EP].
  7. ^ a b "New Dwarf Planet Discovered Far Beyond Pluto's Orbit". 11 July 2016.
  8. ^ a b Chang, Kenneth (13 July 2016). "Astronomers Discover New Likely Dwarf Planet, the Latest of Many". New York Times. Retrieved 14 July 2016.
  9. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 9 October 2018.

External linksEdit