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2011 UN63, also written as 2011 UN63, is a Mars trojan, an asteroid orbiting near the L5 point of Mars (60 degrees behind Mars on its orbit).[2][3]

2011 UN63
Discovered byMt. Lemmon Survey
Discovery dateOctober 21, 2011
MPC designation2011 UN63
Martian L5 Martian L5
Orbital characteristics[1]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 1
Observation arc1587 days (4.34 yr)
Aphelion1.6222522 AU (242.68547 Gm)
Perihelion1.4253677 AU (213.23197 Gm)
1.5238099 AU (227.95872 Gm)
1.88 yr (687.06 d)
0° 31m 26.298s /day
Earth MOID0.434823 AU (65.0486 Gm)
Jupiter MOID3.54877 AU (530.888 Gm)
Physical characteristics
Dimensions560 m
0.5-0.05 (assumed)

Discovery, orbit and physical propertiesEdit

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.[4] 2011 UN63 follows a low eccentricity orbit (0.064) with a semi-major axis of 1.52 AU.[4] This object has moderate orbital inclination (20.4°).[4] 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.[1] This asteroid has an absolute magnitude of 19.7 which gives a characteristic diameter of 560 m.[1]

Mars trojan and orbital evolutionEdit

Recent calculations [2][3] indicate that it is a stable L5 Mars trojan asteroid with a libration period of 1350 yr and an amplitude of 14°. 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.[2]

See alsoEdit


  1. ^ a b c "JPL Small-Body Database Browser: (2011 UN63)". Jet Propulsion Laboratory. Retrieved 31 March 2016.
  2. ^ a b c 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.
  3. ^ a b 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.
  4. ^ a b c MPC data on 2011 UN63
Further reading

External linksEdit