Quote:
Originally posted by ivan_2068
Well Yesspaz, the orbit of a comet is absolutely different to the orbit of a planet, it's not heliocentic because it crosses the orbits of other planets, the orbit of a planet is almost perfectly heliocentric and independant to other plamets, unless something really catastrophic happens).
Of course the comets have other features that planets don't have like tail, nucleus, coma, etc.
Iván
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The orbits of most comets are most DEFINATELY heliocentric (they orbit the sun). The fact that their perihelion (closest approach to the sun) is inside the orbits of the other planets doesn't mean anything. Long period comets are in highly elliptical orbits, their periods being measured in many decades - some in millenia. Some comets eventually break up completely after repeated trips to the inner solar system, if they come in that far.
Some planets have very circular orbits like the earth, others are more elliptical, like Pluto (and certinaly Sedna).
More information about Chiron and the Centaur objects can be found
here.