Kuiper Belt

Kuiper belt binary object

Kuiper belt, also called Edgeworth-Kuiper belt, flat ring of icy small bodies that revolve around the Sun beyond the orbit of the planet Neptune. It was named for the Dutch American astronomer Gerard P. Kuiper and comprises hundreds of millions of objects—presumed to be leftovers from the formation of the outer planets—whose orbits lie close to the plane of the solar system. The Kuiper belt is thought to be the source of most of the observed short-period comets, particularly those that orbit the Sun in less than 20 years, and for the icy Centaur objects, which have orbits in the region of the giant planets. (Some of the Centaurs may represent the transition from Kuiper belt objects [KBOs] to short-period comets.) Although its existence had been assumed for decades, the Kuiper belt remained undetected until the 1990s, when the prerequisite large telescopes and sensitive light detectors became available.

Pluto

KBOs orbit at a mean distance from the Sun larger than the mean orbital distance of Neptune (about 30 astronomical units [AU]; 4.5 billion km [2.8 billion miles]). The outer edge of the Kuiper belt is more poorly defined but nominally excludes objects that never go closer to the Sun than 47.2 AU (7.1 billion km [4.4 billion miles]), the location of the 2:1 Neptune resonance, where an object makes one orbit for every two of Neptune’s. The Kuiper belt contains the large objects Eris, Pluto, Makemake, Haumea, Quaoar, and many, likely millions, of other smaller bodies.