2011 HM102

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2011 HM102
Discovery date April 29, 2011
Trojan asteroid
Orbital characteristics[1][2]
Epoch 2012-Sep-30.0 (JD 2456200.5)
Aphelion 32.41 AU
Perihelion 27.69 AU
30.05 AU
Eccentricity 0.0785
164.73 yr (60,168.7 d)
Inclination 29.42°
Physical characteristics
Dimensions 90–180 km

2011 HM102, also written 2011 HM102, is the ninth Neptune trojan discovered. It was first observed on April 29, 2011 by the New Horizons KBO Search Survey.[3] It has the same orbital period as Neptune and orbits at the L5 Lagrangian point about 60 degrees backwards of Neptune.[4]


2011 HM102 follows a low-eccentricity (0.08) orbit, and its semi-major axis (30.05 AU) is very similar to Neptune's (30.10 AU), orbiting in a 1:1 mean-motion resonance with it. It has a high orbital inclination of 29.42°.[1][4] This large value makes 2011 HM102, as of July 2013, the highest-inclination Neptune trojan known.[4] 2011 HM102 has been observed 145 times, over two oppositions.[1]

Physical properties[edit]

With an absolute magnitude of 8.1,[1][4] it has a diameter somewhere between 90 kilometres (56 mi) and 180 kilometres (110 mi).[5] This makes 2011 HM102, as of October 2012, the brightest L5 trojan in the entire Solar System.

2013 New Horizons flyby[edit]

In October 2012, 2011 HM102 was the closest known object of any kind to the New Horizons spacecraft.[6] In mid- to late-2013, New Horizons was scheduled to pass within 1.2 AU of 2011 HM102, where it would be detectable with one of the onboard instruments.[3] An observation from New Horizons would measure the phase curve of 2011 HM102 at phase angles unobtainable from the Earth. The New Horizons team eventually decided that they would not target 2011 HM102 for observations (as the preparations for the Pluto approach took precedence).[7]


  1. ^ a b c d e "JPL Small-Body Database Browser: 2011 HM102". Retrieved 2012-10-11. 
  2. ^ "AstDys-2 about 2011 HM102". 
  3. ^ a b Parker, Alex H. et al. (2013). "2011 HM102: Discovery of a High-inclination L5 Neptune Trojan in the Search for a Post-Pluto New Horizons Target". The Astronomical Journal 145 (4): 96, 6 pp. arXiv:1210.4549v2. Bibcode:2013AJ....145...96P. doi:10.1088/0004-6256/145/4/96. 
  4. ^ a b c d "List Of Neptune Trojans". Minor Planet Center. Archived from the original on 11 October 2012. Retrieved 2012-10-11. 
  5. ^ "Absolute Magnitude (H)". Archived from the original on 11 October 2012. Retrieved 2012-10-11. 
  6. ^ "Citizen "Ice Hunters" help find a Neptune Trojan target for New Horizons". Retrieved 2012-10-31. 
  7. ^ "2011 HM102: A new companion for Neptune". 

External links[edit]