| Discovery[1] | |
|---|---|
| Discovered by | 30 October 1999 byLINEAR |
| Discovery site | Socorro |
| Discovery date | 30 October 1999 |
| Designations | |
| 2002 AC180[1] | |
Martian L4 | |
| Orbital characteristics[1] | |
| Epoch 13 January 2016 (JD 2457400.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 21861 days (59.85 yr) |
| Aphelion | 1.5843517 AU (237.01564 Gm) |
| Perihelion | 1.4644704 AU (219.08165 Gm) |
| 1.5244110 AU (228.04864 Gm) | |
| Eccentricity | 0.0393206 |
| 1.88yr (687.47d) | |
| 229.9277° | |
| 0° 31m 25.183s / day | |
| Inclination | 16.75044° |
| 347.37714° | |
| 48.35771° | |
| Earth MOID | 0.47372 AU (70.868 Gm) |
| Jupiter MOID | 3.49473 AU (522.804 Gm) |
| Physical characteristics | |
| Dimensions | ~1 km[2] |
| X[3] | |
| 16.9[1] | |
(121514) 1999 UJ7 is a smallasteroid orbiting near theL4 point ofMars (60 degrees ahead Mars on its orbit).[2] As of April 2024, it is one of only two known asteroids to orbit the leadingL4 point of Mars—the other being2023 FW14[4]—although at least 15 other asteroids orbit Mars's trailingL5 point: The largest being5261 Eureka,(101429) 1998 VF31, and2007 NS2.[2] Not only does(121514) 1999 UJ7 orbit on the other side of Mars from other similar asteroids, itsspectrum is different as well, which is puzzling because all of theMartiantrojans seem to be in very stable orbits.[3]
(121514) 1999 UJ7 orbits around theL4 point of Mars. Its orbit is very stable and is large enough that theYarkovsky effect will not affect its orbit.[2]
Due to similarity in the measured brightness of(121514) 1999 UJ7 with other Martian trojans, it is thought to be a small asteroid with an effective diameter on the order of 1 kilometer (0.62 mi).[2] Its spectrum suggests that it is anX-type asteroid, which is different from 5261 Eureka and1998 VF31,[3] and is somewhat puzzling since different mineral compositions suggest different origins for the two groups of asteroids. The long lifetime of the orbits for these asteroids makes the possibility of one or more of them being interlopers unlikely, however. This suggests that either one or more of the Martian trojans was captured in such a way as to give it a long-term stable orbit (and it is therefore not a primordial Martian asteroid), or that some fusion or combination of previous asteroids resulted in the presently observed ones.[3] The Yarkovsky effect may provide a potential capture mechanism but not enough is known about the shapes of these objects to provide a useful Yarkovsky model.[3]
