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Planetary Science

Pluto

Definition

A dwarf planet in the Kuiper Belt, reclassified from planet status by the IAU in 2006. It has five moons, the largest being Charon. NASA's New Horizons flew by in 2015, revealing mountains of water ice and plains of nitrogen ice.

Related Terms

Dwarf Planet

A celestial body orbiting the Sun with enough mass for a nearly round shape but that has not cleared its orbital neighbo...

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...

Near-Earth Object

Any small solar system body whose orbit brings it close to Earth, with a perihelion distance less than 1.3 AU. Includes ...

Explore Related Topics

Dive deeper into pluto and related concepts on Cosmos Observatory.

Solar System Explorer

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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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