|Discovered by||Mt. Lemmon Survey|
|Discovery date||October 21, 2011|
|MPC designation||2011 UN63|
|Minor planet category||Martian L5|
|Epoch April 18, 2013 (JD 2456400.5)|
|Semi-major axis||1.5237401 AU|
|Orbital period||1.88 yr|
|Longitude of ascending node||223.57140°|
|Argument of perihelion||165.29805°|
|Absolute magnitude (H)||19.7|
Discovery, orbit and physical properties
2011 UN63 was first observed on September 27, 2009 by the Mt. Lemmon Survey and given the provisional designation 2009 SA170. Lost, it was re-discovered on October 21, 2011 again by the Mt. Lemmon Survey. 2011 UN63 follows a low eccentricity orbit (0.064) with a semi-major axis of 1.52 AU. This object has moderate orbital inclination (20.4º). It was classified as Mars-crosser by the Minor Planet Center upon discovery. Its orbit is relatively well determined as it is currently (March 2013) based on 64 observations with a data-arc span of 793 days. This asteroid has an absolute magnitude of 19.7 which gives a characteristic diameter of 560 m.
Mars trojan and orbital evolution
Recent calculations  indicate that it is a stable L5 Mars trojan asteroid with a libration period of 1350 yr and an amplitude of 14º. These values as well as its short-term orbital evolution are similar to those of 5261 Eureka or 2011 SC191.
Long-term numerical integrations show that its orbit is very stable on Gyr time-scales (1 Gyr = 1 billion years). As in the case of Eureka, calculations in both directions of time (4.5 Gyr into the past and 4.5 Gyr into the future) indicate that 2011 UN63 may be a primordial object, perhaps a survivor of the planetesimal population that formed in the terrestrial planets region early in the history of the Solar System.
- de la Fuente Marcos, C.; de la Fuente Marcos, R. (April 2013). "Three new stable L5 Mars Trojans". Monthly Notices of the Royal Astronomical Society: Letters 432 (1): L31–L35. arXiv:1303.0124. Bibcode:2013MNRAS.432L..31D. doi:10.1093/mnrasl/slt028.
- Christou, A. A. (2013). "Orbital clustering of Martian Trojans: An asteroid family in the inner solar system?". Icarus 224 (1): 144–153. arXiv:1303.0420. Bibcode:2013Icar..224..144C. doi:10.1016/j.icarus.2013.02.013.
- MPC data on 2011 UN63
- JPL's Solar System Dynamics data on 2011 UN63
- Further reading
- Three new stable L5 Mars Trojans de la Fuente Marcos, C., de la Fuente Marcos, R. 2013, Monthly Notices of the Royal Astronomical Society: Letters, Vol. 432, Issue 1, pp. 31–35.
- Orbital clustering of Martian Trojans: An asteroid family in the inner solar system? Christou, A. A. 2013, Icarus, Vol. 224, Issue 1, pp. 144–153.