(225088) 2007 OR10

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(225088) 2007 OR10
1880-CT MBrown SPOTLIGHT medium.jpg
Artist's impression of (225088) 2007 OR10
Discovered by M. E. Schwamb
Michael Brown
David Rabinowitz
Palomar Observatory (675)
Discovery date 2007-07-17
announced: 2009-01-07
MPC designation (225088) 2007 OR10


3:10 resonance (DES)[3]
Orbital characteristics[4]
Epoch JD 2457000.5 (9 December 2014)
Aphelion 100.66 AU
Perihelion 33.033 AU
66.85 AU
Eccentricity 0.5058
546.6 yr
103.85° (M)
Inclination 30.9376°
Physical characteristics
Dimensions 1280±210 km[5]
(fit to volatile-retention model)[6]
Albedo 0.185+0.076
Temperature 31 K[7]
Spectral type

(225088) 2007 OR10 is a very large planetoid located in the scattered disc. It is the largest known body in the Solar System without a name.[9] It is approximately the size of Haumea, and appears to be a dwarf planet.

Discovery and nickname[edit]

2007 OR10 was discovered by California Institute of Technology astronomers as part of the PhD thesis of Meg Schwamb, who was at the time a graduate student of Michael E. Brown.[10] Brown nicknamed the object "Snow White" for its presumed white color,[10] as it would have to be very large or very bright to be detected by their survey.[9] It was also the "seventh dwarf" discovered by Brown's team, after Quaoar in 2002, Sedna in 2003, Haumea and Orcus in 2004, and Makemake and Eris in 2005. However, "Snow White" 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.[10] However, as of 2015, Brown had yet to propose a name, though he notes that in 2017 anyone will be able to make a proposal.[11]


2007 OR10 came to perihelion around 1857.[4] It is currently 87.0 AU from the Sun.[8][12] This makes it the second-farthest known large body in the Solar System, after Eris (97 AU), and farther out than Sedna (86.3 AU).[9] It has been farther from the Sun than Sedna since 2013.[12] 2007 OR10 will be farther than both Sedna and Eris by 2045,[13] and it will reach aphelion in 2130.[12]

Absolute magnitude[edit]

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,[4] which makes it the fifth-brightest TNO known,[14] a little less bright than Sedna (H=1.6; D=1,000 km)[15] and brighter than Orcus (H=2.3; D≈800 km).[16]

2007 OR10 is among the reddest objects known.[6] This is probably in part due to methane frosts, which turn red when bombarded by sunlight and cosmic rays.[6]

Surface composition and atmosphere[edit]

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.[6] The presence of water ice on the surface of 2007 OR10 implies a brief period of cryovolcanism in its distant past.[17]


The Deep Ecliptic Survey (DES) shows the orbit to be in a 3:10 resonance with Neptune.[3] The MPC lists it as a scattered-disc object.[2] 2007 OR10 was discovered when searching for objects in the region of Sedna.[18]

2007 OR10 has been observed 46 times over seven oppositions with a precovery image from 1985.[4]

Earth Dysnomia Eris Charon Nix Hydra S/2011 (134340) 1 Pluto Makemake Namaka Hi'iaka Haumea Sedna 2007 OR10 Weywot Quaoar Vanth Orcus File:EightTNOs.png
Artistic comparison of Eris, Pluto, Makemake, Haumea, Sedna, 2007 OR10, Quaoar, Orcus, and Earth. ( )

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

The orbit of 2007 OR10 compared to the orbit of Eris, Pluto, and the outer planets.
The motion of 2007 OR10 librating in a 3:10 resonance with Neptune.[3] Neptune is held stationary.

Dwarf-planet status[edit]

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",[19] and Scott Sheppard et al. believe it is "likely" to be a dwarf planet,[20] based on its minimum possible diameter (552 km)[21] and what is understood of the conditions for hydrostatic equilibrium in cold icy–rocky bodies. 2007 OR10 is too distant to resolve its diameter directly; Brown's estimate of 1,000–1,500 km is based on calculating the albedo that is the best fit in his model,[6] and this agrees with the 1280±210 km determined from observations by the Herschel space observatory.[5] 2007 OR10 has no known satellite, and without a satellite with a well-determined orbit, its mass cannot be calculated directly (see three-body problem); mass is also a factor in hydrostatic equilibrium.


  1. ^ a b "MPEC 2009-A42 : 2007 OR10". Minor Planet Center. 2009-01-07. Retrieved 2009-01-20. 
  2. ^ a b "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 2009-01-20. 
  3. ^ a b c Marc Buie (2011-10-24). "Orbit Fit and Astrometric record for 225088". SwRI (Space Science Department). Retrieved 2014-11-14. 
  4. ^ a b c d e "JPL Small-Body Database Browser: 225088 (2007 OR10)" (2011-10-24 last obs; arc: 26.18 years). Retrieved 2014-11-11. 
  5. ^ a b c Santos-Sanz, P., Lellouch, E., Fornasier, S., Kiss, C., Pal, A., Müller, T. G., Vilenius, E., Stansberry, J., Mommert, M., Delsanti, A., Mueller, M., Peixinho, N., Henry, F., Ortiz, J. L., Thirouin, A., Protopapa, S., Duffard, R., Szalai, N., Lim, T., Ejeta, C., Hartogh, P., Harris, A. W., & Rengel, M. (2012). “TNOs are Cool”: A Survey of the Transneptunian Region IV - Size/albedo characterization of 15 scattered disk and detached objects observed with Herschel Space Observatory-PACS
  6. ^ a b c d e f Michael E. Brown; Burgasser, A.J.; Fraser W.C. (2011). "The Surface Composition of Large Kuiper Belt Object 2007 OR10". Mike Brown's Website. arXiv:1108.1418. Retrieved 2011-08-08. 
  7. ^ "HEC: Exoplanets Calculator". Planetary Habitability Laboratory. University of Puerto Rico at Arecibo. Retrieved 17 October 2014. 
  8. ^ a b "AstDys 2007OR10 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 2009-05-17. Retrieved 2009-03-16. 
  9. ^ a b c Michael E. Brown (2009-03-10). "Snow White needs a bailout". Mike Brown's Planets (blog). Archived from the original on 2009-05-17. Retrieved 2010-02-17. 
  10. ^ a b c "Astronomers Find Ice and Possibly Methane On Snow White, a Distant Dwarf Planet". Science Daily. August 22, 2011. Retrieved 2011-08-22. 
  11. ^ [1]
  12. ^ a b c "Horizon Online Ephemeris System". California Institute of Technology, Jet Propulsion Laboratory. Retrieved 2012-01-31. 
  13. ^ JPL Horizons On-Line Ephemeris System (2011-02-17). "Horizons Output for Sedna 2076/2114". Retrieved 2011-02-17. 
  14. ^ Mike Brown (2011). "The Redemption of Snow White (Part 2 of 3)". Mike Brown's Planets. Retrieved 2012-02-08. 
  15. ^ "JPL Small-Body Database Browser: 90377 Sedna (2003 VB12)" (2008-10-23 last obs). Retrieved 2009-01-21. 
  16. ^ "JPL Small-Body Database Browser: 90482 Orcus (2004 DW)" (2008-12-04 last obs). Retrieved 2009-02-05. 
  17. ^ Mike Brown (2011). "The Redemption of Snow White (Part 3 of 3)". Mike Brown's Planets. Retrieved 2011-08-23. 
  18. ^ Schwamb, Megan E.; Michael E. Brown, David L. Rabinowitz (2009). "A Search for Distant Solar System Bodies in the Region of Sedna". Astrophysical Journal Letters. arXiv:0901.4173. Bibcode:2009ApJ...694L..45S. doi:10.1088/0004-637X/694/1/L45. 
  19. ^ Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 2011-09-23. 
  20. ^ Sheppard, Scott S.; Trujillo, C.; Udalski, A,; et al. (2011). "A Southern Sky and Galactic Plane Survey for Bright Kuiper Belt Objects". Astronomical Journal 142 (4). arXiv:1107.5309. Bibcode:2011AJ....142...98S. doi:10.1088/0004-6256/142/4/98. 
  21. ^ 1329×10(−H/5)

External links[edit]