Belts & Clouds

11.5 - Understand the location and nature of the Kuiper Belt, Oort Cloud and the heliosphere

The Kuiper Belt is a region of the Solar System outside the orbit of Neptune. It is thought to extend several times the orbit of Pluto, possibly between 100 to 1000 AU.

The region was first suggested by Gerard Kuiper as a region where large bodies such as Pluto reside temporarily as well as short period comets that orbit the Sun over hundreds of years.

The Oort Cloud was suggested as a source of long period comets by Jan Oort. It was thought that comets orbiting the Sun since the creation of the Solar System (over 4,500 million years ago) would have exhausted their supply of ices and other material.

There is no direct evidence for its existence but studies of long period orbits suggest a spherical region at between 10,000 to 20,000 AU that consists of comets that occasionally get disturbed by a passing star and consequently may send comets towards the Sun.

The Heliosphere is not a region occupied by temporal comets but an extended feature of the Sun's influence. It is a 'bubble' surrounding the solar system, created by the solar wind. It is thought to be 'cigar-shaped' as it is shaped by the Sun's movement. The Sun is moving at a speed of 700,000 km as it orbits the galactic centre. It is thought to be between 80 and 100 AU distance to the Sun.


  • Explain the position of the Kuiper Belt and Oort Cloud
  • Explain the type of bodies thought to originate in the Kuiper Belt and Oort Cloud.