A NEW DYNAMICAL CLASS OF OBJECT IN THE OUTER SOLAR-SYSTEM

Some three dozen objects have now been discovered(1-5) beyond the orbi t of Neptune and classified as members of the Kuiper belt-a remnant po pulation of icy planetesimals that failed to be incorporated into plan ets. At still greater distances is believed to Lie the Oort cloud-a ma ssive population of cometary objects distributed approximately in a sp here of characteristic dimension 50,000 AU (ref. 6). Here we report th e discovery of an object, 1996TL(66), that appears to be representativ e of a population of scattered bodies located between the Kuiper belt and the Oort cloud. 1996TL(66) has an orbital semimajor axis of 84 Au, and is in an extremely eccentric and highly inclined orbit (e = 0.58, i = 24 degrees). With a red magnitude similar to 20.9, it is the brig htest trans-neptunian object yet found since Pluto and Charon. Its dis covery suggests that the Kuiper belt extends substantially beyond the 30-50 AU region sampled by previous surveys, and may contain much more mass than previously suspected.