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Lagoon Nebula,bright, diffuse 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. in the southern constellation Sagittarius; cataloged as M8 or NGC 6526. It is visible to the naked eye and has an angular area larger than that of the full moon. The central parts are extremely bright, and some stars can be seen embedded in the nebulosity. Because of the nebula's large size, light from its stars cannot illuminate all of the associated interstellar gas and dust. Thus, parts of it appear blacker than the surrounding sky.
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Lagoon nebula(M8; NGC 6523) An emission nebula in the form of an H II region that lies about 1 kiloparsec away in the direction of Sagittarius. It contains the open cluster NGC 6530. Its total apparent magnitude (5.8) makes it easily visible with binoculars.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006
Lagoon Nebula[lə′gün ′neb·yə·lə]
A patchy, luminous gaseous nebula that appears to be surrounded by a much larger region of cold, neutral hydrogen.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.