2011 QF99 is the first and, as of 2015, the only known Uranustrojan.[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 thought to be roughly 60 km in diameter, assuming an albedo of 0.05.[2]
2011 QF99 temporarily orbits near Uranus's L4Lagrangian 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]
. Bibcode:2013Sci...341..994A. doi:10.1126/science.1238072. PMID 23990557.
