(523794) 2015 RR245

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2015 RR245
2015 RR245.gif
Orbit of 2015 RR245
Discovery [1][2][3]
Discovered by OSSOS
Discovery site Mauna Kea Obs.
Discovery date 10 July 2016
MPC designation 2015 RR245
TNO[1] · resonant (2:9)[4][5]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 4
Observation arc 11.65 yr (4,254 days)
Earliest precovery date 15 October 2004
Aphelion 128.60 AU
Perihelion 33.769 AU
81.184 AU
Eccentricity 0.5840
731.50 yr (267,180 days)
0° 0m 4.68s / day
Inclination 7.5808°
Physical characteristics
Dimensions 649 km[6]
670 km[4]
806 km[5]
0.11 (assumed)[6]
0.12 (assumed)[4]
3.6±0.1 (Hr)[4] · 3.7[1] · 4.0[6]

(523794) 2015 RR245 is a trans-Neptunian object and possible dwarf planet from the Kuiper belt in the outermost regions of the Solar System. It 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.


A first precoveries was taken at the Cerro Tololo Observatory in Chile on 15 February 2016.[2] 2015 RR245 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).[2][7][8] The oldest precovery is October 15, 2004.[1]

Physical characteristics[edit]

Diameter and albedo[edit]

Its exact size is uncertain, but the best estimate is around 670 km (420 mi) in diameter, assuming an albedo of 0.21.[4] 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 806 kilometers.[5][6]


2015 RR2015's orbit librating in a 2:9 resonance with Neptune

As of 2017, 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.[1] It will make its closest approach to the Sun in 2096.[7]

2:9 resonant TNO[edit]

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 2015 RR245 orbits the Sun twice in the same amount of time it takes Neptune to complete 9 orbits.[4]

2015 RR245 is unlikely to have been trapped in the 2:9 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.[4]


  1. ^ a b c d e f "JPL Small-Body Database Browser: (2015 RR245)" (2016-06-08 last obs.). Jet Propulsion Laboratory. Retrieved 2 August 2017.
  2. ^ a b c "2015 RR245". Minor Planet Center. Retrieved 2 August 2017.
  3. ^ "MPEC 2016-N67 : 2015 RR245". Minor Planet Center. 10 July 2016. ISSN 1523-6714.
  4. ^ 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. Retrieved 2 August 2017.
  5. ^ a b c "List of Known Trans-Neptunian Objects". Johnston's Archive. 22 July 2017. Retrieved 2 August 2017.
  6. ^ a b c d Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 30 July 2017.
  7. ^ a b c "New Dwarf Planet Discovered Far Beyond Pluto's Orbit". space.com. 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.

External links[edit]