a bright diffuse nebula that emits light as a result of ionization of its gas atoms by ultraviolet radiation, as the Orion Nebula, planetary nebulae, and supernova remnants, as the Crab Nebula.
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British Dictionary definitions for emission nebula
a type of nebula that emits visible radiation: See nebula
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 emission nebula
A nebula that absorbs ionizing ultraviolet radiation from nearby hot stars or star remnants and reemits it as visible light. HII regions, planetary nebulae, and nebulae created by the explosion of supernovae are different kinds of emission nebulae. See more at nebula.
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