For an explanation, see the main splats page
The principles of comets
- Comets are volatile bodies orbiting the Sun. When they get close to the Sun, some parts of the comet boil off, forming a 'tail', which points away from the Sun.
- Comets travel in eccentric orbits. Some travel in elliptical orbits, which means they will return, some only make one pass, as they are on hyperbolic paths.
- The first comet to be predicted for a return was Halley's comet, which returns in its orbit to a point reasonably near the Earth about every 76 years.
- In 1950, Jan Oort suggested the presence of a cometary cloud. Now known as the Oort Cloud, orbiting the Sun, some distance beyond the orbit of Pluto.
- New comets that we see entering our part of the solar system are probably ejected from the Oort Cloud, although the cause of their ejection remains unknown.
- According to many astronomers, comets are probably ejected by the gravitational effects of Kuiper Belt Objects pulling them from their previous stable orbits.
- Jupiter acts as a major 'comet sweeper', dragging down most of the inner comets: without Jupiter, many more comets would collide with the Earth.
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