dark nebula

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Related to Dark nebulae: Emission nebulae, Reflection nebulae

dark nebula

(dark cloud; absorption nebula) A cloud of interstellar gas and dust that is sufficiently dense to obscure partially or completely the light from stars and other objects lying behind it and sufficiently large and suitably located to produce a noticeable effect. These nebulae can be observed as dark extrusions in front of bright (emission or reflection) nebulae or as blank regions or regions with a greatly diminished number of stars in an otherwise bright area of sky. In external galaxies they are often observed against the bright spiral arms, where they appear as dark dust lanes. In our own Galaxy the dark clouds in Taurus are the nearest sites of star formation to the Sun. Although the absorption is caused by cosmic dust, the dark nebulae are composed predominantly of molecular hydrogen. Small dark nebulae, called Bok globules, can sometimes be seen in large numbers superimposed on bright nebulae. Although having no optical features dark nebulae can be studied through their radio and infrared emissions. The Coalsack, Horsehead nebula, and the Great Rift are dark nebulae.

dark nebula

[¦därk ‚neb·yə·lə]
(astronomy)
A cloud of solid particles which absorbs or scatters away radiation directed toward an observer and becomes apparent when silhouetted against a bright nebula or rich star field. Also known as absorption nebula.
References in periodicals archive ?
Dark nebulae consist of clouds of gas and dust that are not so illuminated, giving the cloud the appearance of a region devoid of stars.
Of course when looking at objects in the Milky Way, these are mostly fairly close, and there are a wide range of objects to be seen with a telescope--planetary nebulae, bright nebulae, dark nebulae and supernova remnants, and here are just a few suggestions of objects to look at in these categories.
The constellation Chamaeleon is also home to a dark nebula which has been listed as Sa 156 in Sandqvist's Catalogue of Dark Nebulae, published in 1977.
More correctly known as vdB 142, after the Dutch astronomer Sidney van den Bergh who catalogued it in 1966, the Elephant Trunk is a mixture of emission, reflection and dark nebulae.
Bernes, the Sweden Astronomer, was consulted in 1971 to determine physical associations between bright and dark nebulae (Sky Catalogue 2000.