Archive of Astronomy Questions and Answers

Have any new asteroids or other objects been found outside the orbit of Neptune?

There are currently 28 large bodies between 35 and 46 Astronomical Units which have been discovered, mostly since 1992 by astronomers Jane Luu at Harvard, and David Jewett at MIT. One of them, QB1, is nicknames 'Smiley' and is located 44 AU or 6.5 billion kilometers away. It is 280 kilometers across, about 1/8 the size of Pluto. Including Pluto and its moon Charon, and Kowal's Object ( Chiron ) just outside the orbit of Saturn, these Trans- Neptunian Objects are believed to be members of the inner edge of the Kuiper belt: a vast system of billions of icy bodies, many destined to become comets. A class of objects called the Centaurs have orbits that cross the orbits of the giant planets are believed to be the missing link between the Kuiper Belt population and short-period comets.

For more information, see the web sites at Harvard's Center for Astrophysics which list the Centaurs and the Trans-neptunian Objects. Also, have a look at the February 1996 issue of Astronomy magazine for more information.