B. Gladman et al 2009 ApJ 697 L91 doi:10.1088/0004-637X/697/2/L91
DISCOVERY OF THE FIRST RETROGRADE TRANSNEPTUNIAN OBJECT
FREE ISSUEB. Gladman1, J. Kavelaars2,7, J.-M. Petit1,3,7, M. L. N. Ashby4, J. Parker5, J. Coffey1, R. L. Jones6, P. Rousselot3 and O. Mousis3
Show affiliationsWe report the discovery of the first transneptunian object known to be on a retrograde orbit. The discovery was made during an outer solar system survey using the Canada-France-Hawaii Telescope (CFHT). After recovery observations on the MMT, CTIO-Blanco, Gemini-South, and CFHT telescopes, we can state with certainty that the object is both transneptunian and orbits the Sun in a retrograde sense, with an orbital inclination i = 104 deg. The object has IAU Minor Planet Center provisional designation 2008 KV42 and temporary nickname "Drac." Numerical integration of a set of initial states consistent with the astrometry shows that the semimajor axis is a 
42 AU, the perihelion distance is q~21 AU, and that the object's orbit evolves on ~30 million year timescales via gravitational encounters with Uranus and Neptune. The object is unlikely to be primordial and thus needs a supply mechanism from a long-lived source. We outline several scenarios which could have emplaced the object on its current orbit, including a currently unobserved reservoir of large-inclination orbits beyond Neptune which may also supply the Halley-type comets.
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Issue 2 (2009 June 1)
Received 2009 January 11, accepted for publication 2009 April 3
Published 2009 May 4
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Discovery of the First Retrograde Transneptunian Object
B. Gladman et al 2009 ApJ 697 L91