The Oort Cloud

The Oort cloud is a body of comets orbiting the Sun at great distances away. Comets are large balls of rock and ice, often called 'dirty snowballs'.

The Oort cloud was first hypothesised be a Dutch Astronomer called Jan Hendrik Oort. The Oort cloud might even contain 10 trillion comets, and their mass could be up to 10 Earth masses.

Comets are brought into the Oort cloud when they venture too close to Uranus or Neptune, and are flung far out of the solar system. Some comets leave the solar system for ever, others orbit the Sun in the Oort Cloud.

There is also a disk-shaped region past the orbit of neptune roughly 30 to 100 AU from the Sun, and is considered to be the source of the short-period comets. It seems that comets in the Oort cloud were formed closer to the Sun than comets in the Kupier belt, despite the Kupier belt being nearer the Sun.Some astronemers believe that Pluto, Charon and Triton are considered to be large Kupier belt objects, although it will not affect Pluto's official status as a planet for historical reasons.

A new comet, called Quaoar, half composed of rock and half composed of ice has been recently discovered within the Kupier Belt. It orbits the Sun at a distance of 6.3 billion kilometers and has a diameter of 1250 kilometers, roughly half the diameter of Pluto