2004 XR190

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2004 XR190
Discovered by Lynne Jones,
Brett Gladman,
John J. Kavelaars,
Jean-Marc Petit,
Joel Parker,
Phil Nicholson
Discovery date December 11, 2004
MPC designation 2004 XR190
Alternative names none
Minor planet category cubewano[2]
detached object
Orbital characteristics[3]
Epoch 2456800.5 (2014-May-23.0)
Aphelion 64.00 ± 0.02 AU
Perihelion 51.49 ± 0.10 AU
Semi-major axis 57.74 ± 0.02 AU
Eccentricity 0.1083 ± 0.0019
Orbital period 438.8 ± 0.2 a (160,267 ± 84 d)
Mean anomaly 277.38 ± 0.31°
Inclination 46.566 ±0.002°
Longitude of ascending node 252.3583° (Ω)
Argument of perihelion 281.31 ± 0.14° (ω)
Physical characteristics

425–850 km (albedo 0.16–0.04)[4]

335–530 km (albedo 0.25–0.10)[5]
Albedo <0.25?[citation needed]
Apparent magnitude 22.04[6]
Absolute magnitude (H) 4.4[3]

2004 XR190 (also written 2004 XR190) is a possible dwarf planet[7] located in the scattered disc. Astronomers led by Lynne Jones of the University of British Columbia made the discovery as part of the Canada–France Ecliptic Plane Survey (CFEPS) using the Canada–France–Hawaii Telescope (CFHT). The discovery team nicknamed the object "Buffy", after the fictional vampire slayer,[8] and proposed a different official name to the IAU.


Considered a detached object,[9][10] 2004 XR190 is particularly unusual for two reasons. With an inclination of 47 degrees, it is the largest minor planet that has an inclination larger than 45 degrees,[11] traveling further "up and down" than "left to right" around the Sun when viewed edge-on along the ecliptic. Second, it has an unusually circular orbit for a scattered-disc object (SDO). Although it is thought that traditional scattered-disc objects have been ejected into their current orbits by gravitational interactions with Neptune, the low eccentricity of its orbit and the distance of its perihelion (SDOs generally have highly eccentric orbits and perihelia less than 38 AU) seems hard to reconcile with such celestial mechanics. This has led to some uncertainty as to the current theoretical understanding of the outer Solar System. The theories include close stellar passages, rogue planets/planetary embryos in the early Kuiper belt, and resonance interaction with an outward-migrating Neptune. The Kozai mechanism is capable of transferring the orbital eccentricity into an elevated inclination.[4]

2004 XR190 came to aphelion around 1901.[12] Other than long-period comets, it is currently about the twelfth-most-distant known large body (57.6 AU) in the Solar System with a well known orbit, after Eris and Dysnomia (both 96.4 AU), 2007 OR10 (87.0 AU), Sedna (86.3 AU), 2012 VP113 (~83 AU), 2006 QH181 (83.0 AU), 2013 FY27 (80.4 AU), 2010 GB174 (69.8 AU), 2003 QX113 (59.7 AU), 2000 CR105 (59.5 AU), and 2008 ST291 (59.0 AU).[13]


The object has a diameter estimated at around 500 kilometres, roughly a quarter the size of Pluto, and orbits between 51 and 64 AU (7.7 and 9.5 billion km) from the Sun.


  1. ^ "MPEC 2005-X72 : 2004 XR190". IAU Minor Planet Center. 2005-12-12. Retrieved 2014-04-06.  (K04XJ0R)
  2. ^ "2004 XR190 Orbit" (arc=2221 days over 5 oppositions). IAU Minor Planet Center. Retrieved 2014-04-06. 
  3. ^ a b "JPL Small-Body Database Browser: (2004 XR190)". 2011-01-10 last obs. Retrieved 2014-03-30. 
  4. ^ a b R. L. Allen, B. Gladman (2006). "Discovery of a low-eccentricity, high-inclination Kuiper Belt object at 58 AU". The Astrophysical Journal 640: L83. arXiv:astro-ph/0512430. Bibcode:2006ApJ...640L..83A. doi:10.1086/503098.  Discovery paper. Preprint
  5. ^ E. L. Schaller and M. E. Brown (2007). "Volatile loss and retention on Kuiper belt objects". Astrophysical Journal 659: I.61–I.64. Bibcode:2007ApJ...659L..61S. doi:10.1086/516709. Retrieved 2008-04-02. 
  6. ^ "AstDys 2004 XR190 Ephemerides". Department of Mathematics, University of Pisa, Italy. Archived from the original on 26 May 2011. Retrieved 2011-05-16. 
  7. ^ Michael E. Brown. "How many dwarf planets are there in the outer solar system? (updates daily)". California Institute of Technology. Retrieved 2014-03-28. 
  8. ^ Maggie McKee. "Strange new object found at edge of Solar System". New Scientist. Retrieved 2014-04-05. 
  9. ^ Jewitt, David, Morbidelli, Alessandro, & Rauer, Heike. (2007). Trans-Neptunian Objects and Comets: Saas-Fee Advanced Course 35. Swiss Society for Astrophysics and Astronomy. Berlin: Springer. ISBN 3-540-71957-1.
  10. ^ Lykawka, Patryk Sofia & Mukai, Tadashi. (2007). Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation. Icarus Volume 189, Issue 1, July , Pages 213-232. doi:10.1016/j.icarus.2007.01.001.
  11. ^ "JPL Small-Body Database Search Engine: H < 6.5 (mag)". JPL Solar System Dynamics. Retrieved 2014-03-27. 
  12. ^ "Horizon Online Ephemeris System". California Institute of Technology, Jet Propulsion Laboratory. Retrieved 2009-03-23. 
  13. ^ AstDyS-2 list of minor planets more than 57.5AU from the Sun

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