2011 HM102

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2011 HM102
Discovery date April 29, 2011
Minor planet category Trojan asteroid
Orbital characteristics[1][2]
Epoch 2012-Sep-30.0 (JD 2456200.5)
Aphelion 32.41 AU
Perihelion 27.69 AU
Semi-major axis 30.05 AU
Eccentricity 0.0785
Orbital period 164.73 yr (60,168.7 d)
Mean anomaly 22.48°
Inclination 29.42°
Longitude of ascending node 100.989°
Argument of perihelion 152.0°
Physical characteristics
Dimensions 90–180 km
Absolute magnitude (H) 8.1[1]

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 west 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 2 oppositions.[1]

Physical properties[edit]

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

2013 New Horizons flyby[edit]

As of October 2012, 2011 HM102 is the closest known object of any kind to the New Horizons spacecraft.[6] In mid- to late-2013, New Horizons will pass within 1.2 au of 2011 HM102, where it may 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.


  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.; and 21 co-authors. (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. 

External links[edit]