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Planetary Science

Comet

Definition

An icy small body that, when passing close to the Sun, releases gases in outgassing, producing a visible coma and sometimes a tail. Comets originate from the Kuiper Belt and the Oort Cloud at the edges of the solar system.

Related Terms

Kuiper Belt

A circumstellar disc in the outer solar system from Neptune's orbit (30 AU) to about 50 AU. Home to Pluto and many icy b...

Oort Cloud

A theoretical spherical cloud of icy objects surrounding the Sun at 2,000-100,000 AU. Thought to be the source of most l...

Orbit

The curved path of a celestial object around a star, planet, or moon under gravity's influence. Orbits can be circular, ...

Explore Related Topics

Dive deeper into comet and related concepts on Cosmos Observatory.

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Surface imagery from Curiosity and Perseverance.

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Monitor near-Earth objects in real time.

Full Glossary

Browse all 66+ space and astronomy terms.

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