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Horsehead Nebula,dark nebulanebula
[Lat.,=mist], in astronomy, observed manifestation of a collection of highly rarefied gas and dust in interstellar space. Prior to the 1960s this term was also applied to bodies later discovered to be galaxies, e.g.
..... Click the link for more information. located in the constellation Orion; designated IC 434 or B 33. It consists of a cloud of nonluminous interstellar matterinterstellar matter,
matter in a galaxy between the stars, known also as the interstellar medium. Distribution of Interstellar Matter
Compared to the size of an entire galaxy, stars are virtually points, so that the region occupied by the interstellar matter
..... Click the link for more information. resembling the outline of a horse's head and appears against the background of a bright emission nebula. The Horsehead Nebula measures about 4 min of arc at its greatest width. It is located near the belt of Orion at a distance of about 1,600 light-years from the earth.
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Horsehead nebula(IC 434) A dark nebula in Orion located near the star Zeta (ζ) Orionis. It is seen as a dark distinctively shaped region silhouetted against the bright background of an emission (H II) nebula.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Horsehead Nebula[′hȯrs‚hed ′neb·yə·lə]
A cloud of obscuring particles between the earth and a gaseous emission nebula in the constellation Orion.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.