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bipolar nebulaA small emission or reflection nebula that appears hourglass-shaped and that represents outflow of gas in opposite directions from a central star that is often obscured by dust. Many have been detected as infrared or radio sources. A bipolar nebula can occur at two very different stages of a star's evolution. It can represent the early stages of a star's life, when it is the visible sign of the bipolar outflow of T Tauri wind from a young star. It can also result from the directional loss of matter from an evolved giant star as it begins to eject mass to become a planetary nebula.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
bipolar nebula[bī‚pōl·ər ′neb·yə·lə]
A nebula consisting of two relatively symmetrical bright lobes with a star between them.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.