2011 HM102 is an L5 Neptune Trojan, trailing Neptune by approximately 60 degrees. This object was discovered in the search for a New Horizons post-Pluto encounter object in the Kuiper Belt.
This object is the first known Trans-Neptunian Object that New Horizons will fly by. It is currently the closest known object of any kind to New Horizons (within about 4 AU today) and at the end of 2013 they will fly by each other at a range of 1.2 AU, where 2011 HM102 will be just bright enough for one of the cameras on New Horizons to detect.
2011 HM102 is the most inclined Neptune Trojan known, with an inclination of 29.4 degrees, but based on numerical simulations it is stable for at least 1 billion years. It is also intrinsically brighter than any other L5 object known in the solar system, and has a diameter in the range of 90-180 km (depending on its unknown albedo). If roughly spherical, it has a land area up to that of the state of California.
In this animation, 2011 HM102 is represented by the white point, and the four giant planets are represented by colored points. The left panel rotates at the rate of Neptune, effectively freezing Neptune in place and showing 2011 HM102's resonant libration around the L5 point. Lines are drawn when 2011 HM102 passes through pericenter, and the extrema are left as persistent lines to demarcate the approximate extent of libration.
This animation is based off of a full numerical integration of 2011 HM102 and the four giant planets.
The discovery paper has been submitted to the Astronomical Journal.
Along with the New Horizons search team, the citizen scientists of Ice Hunters assisted in identifying 2011 HM102 in recovery images. The names of those that detected 2011 HM102 are listed below:
A. Agbedor, A. Assioli, E. Baeten, T. D. Beer, P. Bel, M. C. Blanaru, M. Bovingdon, P. Brayshaw, T. Brydon, D. Cameron, J. Campos, M. Cotton, C. Cripps, A. Crouthamel, J. Dadesky, J. M. Dawey, T. Demko, L. Dinsdale, G. Dungworth, A. Duvall, C. Emmanuel, A. Erena, R. Evans, P. Fitch, R. Frasier, R. Gagliano, B. Gilbert, A. Gillis, V. Gonano, F. Helk, F. Henriquez, M. Herrenbruck, J. Herridge, D. Herron, T. Hodge, S. Ivanchenko, M. Kelp, C. Kindel, J. Koopmans, H. Krawczyk, A. Lamperti, D. V. Lessen, S. Li, N. Macklem, M. H. Massuda, A. Maya, M. T. Mazzucato, K. McCoy, P. A. McDonald, R. Mideke, G. Mitchell, V. Mottino, D. O'Connor, M. Olga, N. N. Paklin, A. Pandey, C. Panek, E. R. Pearsall, K. Pidgley, S. Pogrebenko, B. Replogle, J. Riley, K. Roovers, C. Schlesinger, T. Sieben, P. D. Stewart, S. R. Taylor, J. Thebarge, H. Turner, R. H.B. Velthuis, P. Verdelis, E. Walravens, B. Way, B. Wyatt, A. Zane, M. Zehner, D. R. Zeigler