The Kuiper belt is a region of space that lies beyond Neptune that contains objects that are left over from the formation of the Solar System.

Unlike the asteroid belt that lies between Mars and Jupiter, most of the objects in the Kuiper belt are made of frozen volatile materials such as methane and ammonia.

The Kuiper belt stretches from roughly 30 to 55 AU away from the Sun (1 AU is the distance from Earth to the Sun).

The number of known Kuiper belt objects (KBOs) is well over 1000, but it is believed that there are over 70,000 that are at least 100km in diameter.

The largest KBO is Pluto. Once thought to be a planet, Pluto is now one of several dwarf planets in the Kuiper belt.