Oort cloud

[ awrt-kloud, ohrt ]
/ ˈɔrt ˌklaʊd, oʊrt /
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noun Astronomy.
a region of our solar system far beyond the orbit of Pluto, in which billions of comets move in nearly circular orbits unless one is pulled into a highly eccentric elliptical orbit by a passing star.


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Compare Kuiper belt.

Origin of Oort cloud

First recorded in 1975–80; after Dutch astronomer Jan Hendrik Oort (1900–1992), who proposed its existence

Words nearby Oort cloud

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

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Scientific definitions for Oort cloud

Oort cloud
[ ôrt ]

A sphere-shaped mass of more than 100 billion comets that makes up the outer edge of the solar system, surrounding the Kuiper belt and the planets. Some comets from this area are drawn into the inner solar system by passing stars and other forces and take more than 200 years to make one complete orbit of the Sun. Compare Kuiper belt.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.