Main-belt comet
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Main-belt comets are bodies orbiting within the (main) asteroid belt which show cometary activity during a part of their orbit.
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[edit] Orbits
Unlike most comets which spend most of their orbit at Jupiter-like or greater distances from the Sun, main-belt comets follow near-circular orbits within the asteroid belt that are undistinguishable from the orbits of many standard asteroids. While quite a few short period comets have semimajor axes well within Jupiter's orbit, main-belt comets differ in having small eccentricities and inclinations just like main-belt asteroids. The three known main-belt comets all orbit within the outer part of the main belt [1].
It is not known how an outer solar system body like the other comets could have made its way into a low-eccentricity orbit typical of the asteroid belt which is only weakly perturbed by the planets. Hence, it is assumed that unlike other comets, the main-belt comets formed in an inner solar system orbit close to their present positions [2].
[edit] Cometary activity
Main belt comets display a cometary dust tail only for a part of their orbit near perihelion. The activity persists for a month or several [2]out of each 5-6 year orbit.
[edit] Composition
It has been hypothesised that they may have been the source of Earth's water[3].
[edit] Members
Presently there are three identified members:
- 133P/Elst-Pizarro
- 176P/LINEAR
- P/2005 U1 (Read)
[edit] External links
- Henry Hsieh's Main-Belt Comets page has extensive details on Main-belt comets
- Planetary Society article on MBCs
- Discussion of possible differences in characteristics of the water in MBCs and other comets
[edit] References
- ^ Diagram from Henry Hsieh's Main Belt Comets webpage.
- ^ a b Main Belt Comets, webpage written by Henry Hsieh.
- ^ Main-Belt Comets May Have Been Source Of Earths Water, Space Daily, Mar 23, (2006).
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