(687170) 2011 QF99
Uranus trojan
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(687170) 2011 QF99 is a minor planet from the outer Solar System and the first known Uranus trojan to be discovered. It measures approximately 60 kilometers (37 miles) in diameter, assuming an albedo of 0.05.[3][4] It was first observed 29 August 2011 during a deep survey of trans-Neptunian objects conducted with the Canada–France–Hawaii Telescope, but its identification as a Uranian trojan was not announced until 2013.[3][5]
Animation of 2011 QF99 relative to Sun and Uranus 1600–2500 2011 QF99 · Uranus · Sun | |
| Discovery | |
|---|---|
| Discovered by | M. Alexandersen[1] |
| Discovery site | Mauna Kea Obs. |
| Discovery date | 29 August 2011[2] (first observation only) |
| Designations | |
| 2011 QF99 | |
| Uranus trojan[3] centaur[2] · distant[1] | |
| Orbital characteristics[2] | |
| Epoch 4 September 2017 (JD 2458000.5) | |
| Uncertainty parameter 3 | |
| Observation arc | 3.97 yr (1,449 days) |
| Aphelion | 22.422 AU |
| Perihelion | 15.659 AU |
| 19.040 AU | |
| Eccentricity | 0.1776 |
| 83.08 yr (30,346 days) | |
| 283.84° | |
| 0° 0m 42.84s / day | |
| Inclination | 10.833° |
| 222.52° | |
| 288.25° | |
| Physical characteristics | |
| 60 km (calculated)[3] | |
| 0.05 (assumed)[3] | |
| 9.6 (R-band)[3] 9.7[2] | |
2011 QF99 temporarily orbits near Uranus's L4 Lagrangian 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. 2011 QF99 is thus a temporary Uranus trojan—a centaur captured some time ago.[3][6]
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).[3] A second Uranian trojan, (636872) 2014 YX49, was announced in 2017.[7]
