2011 QF99

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2011 QF99
Discovery date 2011 [1]
Orbital characteristics[2]
Epoch JD 2457000.5 (2014-Dec-09)
Aphelion 22.526 AU
Perihelion 15.707 AU
19.117 AU
Eccentricity 0.17835
83.59 yr (30,530 ± 4 d)
Inclination 10.8119°
Physical characteristics
Dimensions ~ 60 km [2]
Albedo 0.05 (assumed)
9.6 (r-band) [2]
9.7 [1]

2011 QF99 is the first and, as of 2015, the only known Uranus trojan.[2][3] It was discovered in 2011 during a deep survey of trans-Neptunian objects conducted with the Canada–France–Hawaii Telescope.[2][4] It is believed to be roughly 60 km in diameter, assuming an albedo of 0.05.[2]

2011 QF99 temporarily orbits near Uranus's L4 Langrangian point (leading Uranus). It will continue to librate around L4 for at least 70,000 years and will remain a Uranus co-orbital for up to three million years before becoming a centaur. 2011 QF99 is thus a temporary Uranus trojan—a centaur captured some time ago.[2]

Uranus trojans are generally expected to be unstable and none of them are thought to be of primordial origin. A simulation led to the conclusion that at any given time, 0.4% of the centaurs in the scattered population within 34 AU would be Uranus co-orbitals, of which 64% (0.256% of all centaurs) would be in horseshoe orbits, 10% (0.04%) would be quasi-satellites, and 26% (0.104%) would be trojans (evenly split between the L4 and L5 groups).[2]


  1. ^ a b "JPL Small-Body Database Browser: 2011 QF99". Retrieved 2013-03-29. 
  2. ^ a b c d e f g h Alexandersen, M.; Gladman, B.; Greenstreet, S.; Kavelaars, J. J.; Petit, J. -M.; Gwyn, S. (2013). "A Uranian Trojan and the Frequency of Temporary Giant-Planet Co-Orbitals". Science 341 (6149): 994–997. arXiv:1303.5774. doi:10.1126/science.1238072. PMID 23990557. 
  3. ^ Choi, C. Q. (2013-08-29). "First 'Trojan' Asteroid Companion of Uranus Found". Space.com web site. TechMediaNetwork. Retrieved 2013-09-03. 
  4. ^ Alexandersen, M.; Kavelaars, J.; Petit, J.; Gladman, B. (18 March 2013). "MPEC 2013-F19: 2011 QF99". IAU. Retrieved 3 September 2013.