Oort cloud definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a moving mass of icy cosmic debris thought to exist in the vast region beyond Pluto and to be the source of the comets that orbit the sun
Origin: after J. Oort (1900-92), Dutch astronomer
Oort cloud definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A swarm of comets orbiting the sun at a distance of one to two light-years, proposed as a source of comets that pass near the sun.
Origin: After Jan Hendrix Oort (1900-1992), Dutch astronomer.
oort cloud - Science Definition
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.