Quaoar, Kuiper Belt object, artwork. Discovered in 2002 and with a diameter of around 1000 kilometres (about half that of Pluto), Quaoar is one of the largest objects yet found in the Kuiper Belt. Other large KBOs include Sedna and 2003 UB313. The Kuiper Belt extends from the orbit of Neptune at 30 AU (30 times the Earth-Sun distance) to 50 AU, and is composed of a huge number of small bodies - there are at least 70,000 with diameters greater than 100 kilometres. It is believed that these Kuiper Belt objects of ice and rock are remnants of the accretions which formed our own planets. Differences in temperature and composition led to planets forming close to the Sun, and Kuiper Belt objects forming further away from the Sun.