emission nebula

noun

, Astronomy.

1. 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.

emission nebula

noun

1. See nebula
   a type of nebula that emits visible radiation See nebula

emission nebula

/ ĭ-mĭsh′ən /

1. 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.
2. See more at nebula