(225088) 2007 OR10

This page was last edited on 29 January 2018, at 22:48.

(225088) 2007 OR10 is a trans-Neptunian object (TNO) orbiting the Sun in the scattered disc, approximately 1500 kilometers in diameter. It is the fourth-largest known body in the Solar System beyond the orbit of Neptune,[6][7][13] and continues to be the largest known body in the Solar System without a name.[14] According to estimates as of May 2016, it is slightly larger than Makemake, and is hence almost certainly a dwarf planet. It has one known moon.[5]

(225088) 2007 OR10
2007 OR10 and its moon
2007 OR10 and its moon seen by the Hubble Space Telescope in 2010
Discovery [1]
Discovered by M. E. Schwamb
M. E. Brown
D. L. Rabinowitz
Discovery site Palomar Obs.
Discovery date 17 July 2007 [a]
MPC designation (225088) 2007 OR10
TNO[2] · SDO[3] · 3:10 res.[4]
Orbital characteristics[2]
Epoch 16 February 2017 (JD 2457800.5)
Uncertainty parameter 4
Observation arc 30.09 yr (10,989 days)
Earliest precovery date 19 August 1985
Aphelion 101.02 AU
Perihelion 33.102 AU
67.059 AU
Eccentricity 0.5064
549.16 yr (200,579 days)
0° 0m 6.48s / day
Inclination 30.904°
Known satellites 1[5]
Physical characteristics
Dimensions 1535+75
Mass ~1.3–6 × 1021 kg (est.)
44.81±0.37 h[6][7]
Temperature 31 K[9]
1.8[2][12] · 2.34[6]



(225088) 2007 OR10 was discovered by California Institute of Technology astronomers as part of the PhD thesis of Megan E. Schwamb, then a graduate student of Michael E. Brown.[15]


Brown nicknamed the object "Snow White" for its presumed white color,[15] because it would have to be very large or very bright to be detected by their survey.[14] By that time, Brown's team had already discovered "seven dwarves": Quaoar in 2002, Sedna in 2003, Haumea, Salacia and Orcus in 2004, and Makemake and Eris in 2005. However, 2007 OR10 turned out to be one of the reddest objects in the Kuiper belt, comparable only to Quaoar, so the nickname was dropped.

2007 OR10 is currently the largest known object in the Solar System without an official name. In 2011 Brown decided he finally had enough information to justify giving it one, because the discovery of water ice and the possibility of methane makes it noteworthy enough to warrant further study.[15] However, as of 2017, Brown had yet to propose a name, though he notes that in November 2019 anyone will be able to make a proposal.[16]


(225088) 2007 OR10 came to perihelion around 1857.[2] As of February 2016 it is located 87.5 AU from the Sun[17] and moving at 2.7 kilometers per second (6,000 miles per hour) with respect to the Sun.[18] This makes it the fourth-farthest known large body in the Solar System, after V774104 (103 AU), Eris (96.3 AU), 2014 UZ224 (91.4 AU), and farther out than Sedna (85.7 AU) as of 4 February 2017.[14] It has been farther from the Sun than Sedna since 2013.[18] 2007 OR10 will be farther than both Sedna and Eris by 2045,[19] and it will reach aphelion in 2130.[18]

Absolute magnitude

The size of an object can be calculated from its absolute magnitude (H) and the albedo (the amount of light it reflects). 2007 OR10 has an absolute magnitude (H) of 1.92,[2] which makes it the fifth-brightest TNO known,[20] a little less bright than Sedna (H=1.5; D≈1,000 km)[21] and brighter than Orcus (H=2.2; D≈800 km).[22]

2007 OR10 is among the reddest objects known.[10] This is probably in part due to methane frosts, which turn red when bombarded by sunlight and cosmic rays.[10]

Surface composition and atmosphere

The spectrum of 2007 OR10 shows signatures for both water ice and methane, which makes it similar in composition to Quaoar. The presence of red methane frost on the surfaces of both 2007 OR10 and Quaoar implies the existence of a tenuous methane atmosphere on both objects, slowly evaporating into space. Although 2007 OR10 comes closer to the Sun than Quaoar, and is thus warm enough that a methane atmosphere should evaporate, its larger mass makes retention of an atmosphere just possible.[10] In particular, 2007 OR10's large size means that it is likely to retain even nitrogen, which almost all TNOs lose over the course of their existence.[23] The presence of water ice on the surface of 2007 OR10 implies a brief period of cryovolcanism in its distant past.[24]


Earth Moon Dysnomia Dysnomia Eris Eris Charon Charon Nix Nix Kerberos Kerberos Styx Styx Hydra Pluto Pluto Makemake Makemake Namaka Namaka Hi'iaka Hi'iaka Haumea Haumea Salacia Salacia Actaea 2002 MS4 2002 MS4 Sedna Sedna 2007 OR10 2007 OR10 Weywot Weywot Quaoar Quaoar Vanth Vanth Orcus Orcus File:EightTNOs.png
Artistic comparison of Pluto, Eris, Makemake, Haumea, Sedna, 2002 MS4, 2007 OR10, Quaoar, Salacia, Orcus, and Earth along with the Moon.

The Deep Ecliptic Survey (DES) shows the orbit to be in a 3:10 resonance with Neptune.[4] The MPC lists it as a scattered-disc object.[3] 2007 OR10 was discovered when searching for objects in the region of Sedna.[25]

2007 OR10 has been observed 46 times over seven oppositions with a precovery image from 19 August 1985.[2]

It was formally announced on 7 January 2009.[1]

2007 OR10 orbit Jan2018
The orbit of 2007 OR10 compared to the orbit of Eris, Pluto, and the outer planets
2007 OR10 orbit Jan2018-side
Side view of 2007 OR10 and Eris
Resonance. A preliminary motion analysis of 2007 OR10 librating in a 3:10 resonance with Neptune. The animated GIF consists of 16 frames covering 26,000 years.[4] Neptune is held stationary.

Dwarf-planet status

Based on the most recent size estimates as of May 2016,[7] 2007 OR10 would be the third-largest dwarf planet, after Pluto, Eris, and before Makemake, Haumea, and Ceres, though the error bars overlap with those of Makemake. The IAU has not addressed the possibility of accepting additional dwarf planets since before the discovery of 2007 OR10 was announced. Brown states that it "must be a dwarf planet even if predominantly rocky",[26] and Scott Sheppard and colleagues think that it is "likely" to be a dwarf planet,[27] based on its minimum possible diameter (552 km)[28] and what is understood of the conditions for hydrostatic equilibrium in cold icy–rocky bodies. 2007 OR10 is too distant for its diameter to be resolved directly; Brown's estimate of 1,000–1,500 km is based on calculating the albedo that is the best fit in his model,[10] which agrees with the 1280±210 km determined from observations by the Herschel space observatory.[8] Updated thermal modeling put the size into the 1500 km range with a comparatively low albedo of 8%.[6] If the orbit of 2007 OR10's small satellite (see below) can be well determined, its mass could be calculated directly; mass is also a factor in hydrostatic equilibrium.


Moon Around the Dwarf Planet 2007 OR10
Moon around dwarf planet 2007 OR10.[29]

The slow rotation rate of 2007 OR10, compared to the other TNOs, raised the possibility of a satellite that slowed down the rotation via tidal dissipation. In 2016, analysis of Hubble images of 2007 OR10 taken in 2010 revealed a satellite around 300 km in diameter and orbiting at a distance of at least 15,000 km. It was announced at the DPS48 meeting on 17 October 2016.[5][30] The satellite is probably too small and dark to affect size estimates for 2007 OR10.[5] Further analysis from May 2017 confirms this orbiting moon.[31][32]

See also


  1. ^ Discovery was announced two years later on 7 January 2009


  1. ^ a b "MPEC 2009-A42 : 2007 OR10". Minor Planet Center. 7 January 2009. Archived from the original on 11 March 2012.
  2. ^ a b c d e f "JPL Small-Body Database Browser: 225088 (2007 OR10)" (2015-09-20 last obs.). Jet Propulsion Laboratory. Retrieved 28 February 2017.
  3. ^ a b "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 20 January 2009.
  4. ^ a b c Buie, M. (24 October 2011). "Orbit Fit and Astrometric record for 225088". SwRI (Space Science Department). Retrieved 14 November 2014.
  5. ^ a b c d Lakdawalla, E. (19 October 2016). "DPS/EPSC update: 2007 OR10 has a moon!". The Planetary Society. Retrieved 2016-10-19.
  6. ^ a b c d e f Pál, A.; et al. (2016). "Large size and slow rotation of the trans-Neptunian object (225088) 2007 OR10 discovered from Herschel and K2 observations". The Astronomical Journal. 151 (5): 117. arXiv:1603.03090Freely accessible. Bibcode:2016AJ....151..117P. doi:10.3847/0004-6256/151/5/117.
  7. ^ a b c d e Szabó, Róbert (4 November 2015). "Pushing the Limits of K2:Observing Trans-Neptunian Objects S3K2: Solar System Studies with K2" (PDF). Retrieved 19 January 2018.
  8. ^ a b c Santos-Sanz, P.; et al. (2012). ""TNOs are Cool": A survey of the trans-Neptunian region. IV. Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel-PACS". Astronomy & Astrophysics. 541: A92. arXiv:1202.1481Freely accessible. Bibcode:2012A&A...541A..92S. doi:10.1051/0004-6361/201118541.
  9. ^ "HEC: Exoplanets Calculator". Planetary Habitability Laboratory. University of Puerto Rico at Arecibo. Retrieved 17 October 2014.
  10. ^ a b c d e Brown, M. E.; Burgasser, A. J.; Fraser, W. C. (2011). "The Surface Composition of Large Kuiper Belt Object 2007 OR10" (PDF). The Astrophysical Journal Letters. 738 (2): L26. arXiv:1108.1418Freely accessible. Bibcode:2011ApJ...738L..26B. doi:10.1088/2041-8205/738/2/L26.
  11. ^ "AstDys 2007OR10 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 17 May 2009. Retrieved 16 March 2009.
  12. ^ "225088 (2007 OR10)". Minor Planet Center. Retrieved 17 September 2016.
  13. ^ Dyches, P. (2016-05-11). "2007 OR10: Largest Unnamed World in the Solar System". Jet Propulsion Lab. Retrieved 2016-05-12.
  14. ^ a b c Michael E. Brown (10 March 2009). "Snow White needs a bailout". Mike Brown's Planets (blog). Archived from the original on 17 May 2009. Retrieved 17 February 2010.
  15. ^ a b c "Astronomers Find Ice and Possibly Methane On Snow White, a Distant Dwarf Planet". Science Daily. 22 August 2011. Retrieved 22 August 2011.
  16. ^ Brown, Mike. "Mike Brown on Twitter". Twitter. Retrieved 11 April 2017.
  17. ^ "AstDyS-2, Asteroids - Dynamic Site". 2016-02-26. Retrieved 2016-02-29. Objects with distance from Sun over 59 AU
  18. ^ a b c "Horizon Online Ephemeris System". Jet Propulsion Laboratory. Retrieved 31 January 2012.
  19. ^ "Horizons Output for Sedna 2076/2114". JPL Horizons On-Line Ephemeris System. 17 February 2011. Archived from the original on 25 February 2012. Retrieved 17 February 2011.
  20. ^ Brown, Mike Brown (11 August 2011). "The Redemption of Snow White (Part 2 of 3)". Mike Brown's Planets. Archived from the original on 25 July 2014.
  21. ^ "JPL Small-Body Database Browser: 90377 Sedna (2003 VB12)" (2008-10-23 last obs). Retrieved 21 January 2009.
  22. ^ "JPL Small-Body Database Browser: 90482 Orcus (2004 DW)" (2008-12-04 last obs). Retrieved 5 February 2009.
  23. ^ "2007 OR10: Largest Unnamed World in the Solar System". nasa.gov.
  24. ^ Brown, Mike (20 August 2011). "The Redemption of Snow White (Part 3 of 3)". Mike Brown's Planets. Archived from the original on 25 July 2014.
  25. ^ Schwamb, Megan E.; Brown, Michael E.; Rabinowitz, David L. (2009). "A Search for Distant Solar System Bodies in the Region of Sedna". Astrophysical Journal Letters. 694: L45. arXiv:0901.4173Freely accessible. Bibcode:2009ApJ...694L..45S. doi:10.1088/0004-637X/694/1/L45.
  26. ^ Brown, Michael E. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 12 November 2016.
  27. ^ Sheppard, Scott S.; Udalski, Andrzej; Trujillo, Chadwick; Kubiak, Marcin; Pietrzynski, Grzegorz; Poleski, Radoslaw; et al. (October 2011). "A Southern Sky and Galactic Plane Survey for Bright Kuiper Belt Objects". The Astronomical Journal. 142 (4): 10. arXiv:1107.5309Freely accessible. Bibcode:2011AJ....142...98S. doi:10.1088/0004-6256/142/4/98. Retrieved 11 December 2017.
  28. ^ 1329×10(−H/5)
  29. ^ "Moon Around the Dwarf Planet 2007 OR10". www.spacetelescope.org. Retrieved 22 May 2017.
  30. ^ "The moon of the large Kuiper-belt object 2007 OR10" (PDF). DPS48 120.22. Retrieved 17 October 2016.
  31. ^ NASA/Goddard Space Flight Center. (2017, May 18). Moon orbits third largest dwarf planet in our solar system. ScienceDaily. Retrieved May 19, 2017 from www.sciencedaily.com/releases/2017/05/170518140249.htm
  32. ^ Kiss, C. et al., 2017, "Discovery of a Satellite of the Large Trans-Neptunian Object (225088) 2007 OR10", The Astrophysical Journal Letters, Volume 838, Issue 1, article id. L1 http://adsabs.harvard.edu/abs/2017ApJ...838L...1K

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