How many comets are there?
There are thousands of millions of them. Most of them are located in one of the following two regions. One is the ‘Oort cloud’, at the edge of the Solar System. It is 100 000 times more distant from the Sun than the Earth and astronomers estimate it contains about 12 000 million comets. The second region is the ‘Kuiper belt’ formed by thousands of millions of comets just beyond Neptune’s orbit. The Kuiper belt is 30 to 50 times more distant than the Earth from the Sun. Some comets escape from these regions and come to the inner Solar System. Scientists do not know how many comets come towards the Sun. About 880 of them have been catalogued so far, of which around 150 are periodic, meaning their orbits will repeat. In 2002 over 150 new comets were discovered (mostly ‘sun grazers’) by the ESA/NASA SOHO spacecraft.
