planetary nebula
noun Date: 1785 a usually compact luminous ring-shaped nebula that is composed of matter which has been ejected from a hot star at its center

New Collegiate Dictionary. 2001.

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  • Planetary nebula — Planetary Plan et*a*ry, a. [Cf. L. planetarius an astrologer, F. plan[ e]taire planetary. See {Planet}.] 1. Of or pertaining to the planets; as, planetary inhabitants; planetary motions; planetary year. [1913 Webster] 2. Consisting of planets; as …   The Collaborative International Dictionary of English

  • planetary nebula — n. [from its resemblance, when viewed through a telescope, to a PLANET] a glowing, expanding nebula that forms around a collapsing star …   English World dictionary

  • Planetary nebula — A planetary nebula is an emission nebula consisting of a glowing shell of gas and plasma formed by certain types of stars when they die. The name originated in the 18th century because of their similarity in appearance to giant planets when… …   Wikipedia

  • planetary nebula — Astron. 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… …   Universalium

  • 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 • Hypernyms:… …   Useful english dictionary

  • planetary nebula — noun Astronomy a ring shaped nebula formed by an expanding shell of gas round an ageing star …   English new terms dictionary

  • planetary nebula — noun A nebulosity surrounding a dying star, consisting of material expelled by the star. Syn: PN …   Wiktionary

  • planetary nebula — plan′etary neb′ula n. astron. an expanding shell of thin ionized gas that is ejected from and surrounds a hot, dying star • Etymology: 1775–85 …   From formal English to slang

  • planetary nebula — /plænətri ˈnɛbjələ/ (say planuhtree nebyuhluh) noun shells of gas ejected from certain very hot stars …   Australian English dictionary

  • Planetary nebula luminosity function — (PNLF) is a secondary distance indicator used in astronomy. It makes use of the [O III| [O III] λ5007 forbidden line found in all planetary nebula which are members of the old stellar populations (Population… …   Wikipedia

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