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supernova remnant(SNR) The expanding shell of gas from a supernova explosion, consisting of the supernova ejecta and ‘swept-up’ interstellar gas. Young (< 1000 year old) supernova remnants are generally optically faint but are fairly strong radio and X-ray sources; the Crab nebula is exceptionally bright because it is energized by a central pulsar. Older supernova remnants appear as rings of bright filaments, again with associated radio and X-ray emission. Supernova remnants that have been observed at sufficiently high resolution can be loosely classified into two types. In shell SNRs, which constitute about 90% of all SNRs (including Tycho and Kepler), most of the observed radiation comes from a filamentary, often spherical shell; they seem to have no central power source and their luminosity is exclusively derived from the interaction of the supernova shell with the external medium. Plerions (or filled or filled-center SNRs) are now widely thought to be powered by a central pulsar – the Crab nebula is the archetypal example – and the observed radiation originates from the whole of the remnant. Compression by an expanding supernova remnant can trigger star formation in interstellar clouds. See also emission nebula.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
supernova remnant[¦sü·pər′nō·və ′rem·nənt]
A nebula consisting of an expanding shell of gas that has been ejected by a supernova. Abbreviated SNR.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.