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planetary nebula
4 dictionary results for: planetary nebula
Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This
planetary nebula
–noun Astronomy.
| an expanding shell of thin ionized gas that is ejected from and surrounds a hot, dying star of about the same mass as the sun; the gas absorbs ultraviolet radiation from the central star and reemits it as visible light by the process of fluorescence. |
Origin:
1850–55; so named for its resemblance to the planets Uranus and Neptune
1850–55; so named for its resemblance to the planets Uranus and Neptune
Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
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Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.
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American Heritage Dictionary - Cite This Source - Share This
| planetary nebula
n. A nebula, such as the Ring Nebula, consisting of a hot, blue-white, central star surrounded by an envelope of expanding gas. |
The American Heritage® Dictionary of the English Language, Fourth Edition
Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Copyright © 2006 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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WordNet - Cite This Source - Share This
| planetary nebula | |
noun | |
| a nebula that was once thought to be a star with its planets but is now thought to be a very hot star surrounded by an expanding envelope of ionized gases that emit a fluorescent glow because of intense radiation from the star |
WordNet® 3.0, © 2006 by Princeton University.
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The American Heritage Science Dictionary - Cite This Source - Share This
planetary nebula
 (plān'ĭ-těr'ē) Pronunciation Key
A nebula consisting of a rapidly expanding shell of glowing gas, mostly hydrogen, ejected from a red giant upon its collapse into a white dwarf. Ultraviolet radiation from the hot, luminous white dwarf ionizes the expanding gas and causes it to glow. The nebula disappears once the cooling dwarf can no longer ionize it, and its material eventually returns to the interstellar medium. See more at white dwarf. |
The American Heritage® Science Dictionary
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Copyright © 2002 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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