planetary nebula

nounAstronomy.

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 of planetary nebula

First recorded in 1850–55; so named for its resemblance to the planets Uranus and Neptune

Words Nearby planetary nebula

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

How to use planetary nebula in a sentence

While about half its mass will flood out, the rest will crush together at the very center of the planetary nebula.
What happens when the sun burns out? | Rahul Rao | October 7, 2021 | Popular-Science
A star has actually, under our eyes, become a planetary nebula, and the cycle of which he gave the first terms is complete.
Sir William Herschel: His Life and Works | Edward Singleton Holden
Its visual appearance in the great telescope was now also that of a planetary nebula.
Pleasures of the telescope | Garrett Serviss
For a glance at a planetary nebula we may turn with the five-inch to No. 4234.
Pleasures of the telescope | Garrett Serviss

British Dictionary definitions for planetary nebula

planetary nebula

noun

an expanding shell of gas surrounding a dying star, formed from matter ejected from the star's outer layers; the gas is ionized by the remaining hot stellar core, emitting light in the process

Origin of planetary nebula

C18: named from its (occasional) resemblance to a planetary disc

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for planetary nebula

planetary nebula

[ plăn′ĭ-tĕr′ē ]

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.

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