List of comets
Encyclopedia
Non-periodic comet
Comet
A comet is an icy small Solar System body that, when close enough to the Sun, displays a visible coma and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet...

s are seen only once. They are usually on near-parabolic orbits that will not return to the vicinity of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 for thousands of years, if ever.

Periodic comets usually have elongated elliptical orbits, and usually return to the vicinity of the Sun after a number of decades.

The official names of non-periodic comets begin with a "C"; the names of periodic comets begin with "P" or a number followed by "P". Comets that have been lost or disappeared have names with a "D".

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