dark nebula


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Related to dark nebula: emission nebula

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.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
magdalena@mweb.co.za Object Type RA (J2000.0) Dec NGC 6631 Open Cluster 18h27m2 -12[degrees]02' IC 1287 Diffuse Nebula 18 31 6 -10 47 NGC 6649 Open Cluster 18 33 5 -10 24 NGC 6664 Open Cluster 18 36 6 -07 49 NGC 6694 Open Cluster 18 45 2 -09 24 BARNARD 104 Dark Nebula 18 47 3 -04 34 NGC 6704 Open Cluster 18 50 9 -05 12 NGC 6705 Open Cluster 18 51 1 -06 16 NGC 6712 Globular Cluster 18 53 4 -08 42 IC 1295 Open Cluster 18 54 6 -08 50 Object Type Mag.
The dark nebula B64 is situated a few arc-minutes away towards the western field of view.
The whole area is covered in smoke-like gas and dust, with small parts of the dark nebula quite well defined against the very dense star-field (see combine sketch with NGC 6139).
His 16 minute guided exposure shows just how complex this whole area is, with the nebulosity extending out to mu Cephei (the Garnet Star) along with several intruding dark lanes, many of which have Barnard dark nebula designations.
The easiest way to find this dark nebula is to head east-northeast from Deneb about 7[degrees] about one binocular field) to the pretty open cluster M39, and then move the cluster off to the western edge of your field of view.
Caption: The diffuse emission nebulae Sh 2-120 and Sh 2-121 are subtle glows ensconced in the dust clouds at the periphery of the Le Gentil 3 dark nebula complex in northeastern Cygnus.
Immediately west of eta Carinae is a keyhole-shaped dark nebula, the remnants of a molecular cloud from which some of the surrounding stars were formed.
Object Type RA (J2000.0) Dec eta Chamaeleontis Open Cluster 08h41.3 -78[degrees]58' Streicher 21 Asterism 08 51.0 -80 10 E3 Globular 09 21.0 -77 17 NGC 2915 Galaxy 09 26.2 -76 38 NGC 3149 Galaxy 10 03.8 -80 25 NGC 3195 Planetary Nebula 10 09.5 -80 52 IC 2631 Reflection Nebula 11 09.8 -76 37 NGC 3620 Galaxy 11 16.1 -76 13 Sa 159 Dark Nebula 12 59.0 -77 10 Object Mag Size eta Chamaeleontis 5.4 8' Streicher 21 11.0 22' E3 11.3 5' NGC 2915 12.4 2.4' x 1.3' NGC 3149 12.8 2.0' x 1.9' NGC 3195 10.6 40" x 30" IC 2631 12.0 8.0' x 7.0' NGC 3620 12.7 2.8' x 1.1' Sa 159 -- 3[degrees] x 2[degrees] 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.
Newcomers to deep-sky observing are warmly invited to observe the "Big 5 of the African Sky", a new observing project highlighting the most splendid example of each type of deep-sky object: a galaxy, a bright nebula, a dark nebula, an open cluster, and a globular cluster.
To accompany this dark nebula to the NE is vdBH 63, also indicated as GN 14.45.2, which is only a faint wisp of light seen with averted vision, reflected by the light of the magnitude 10.4 star HD 130079.
The dark nebula designated Barnard 143 makes the top two branches of the E, while bar-shaped Barnard 142 forms the bottom of the E.
If I star-hop to the correct location for a Barnard dark nebula, and note a marked decrease in the density of faint stars precisely where the atlas says that I should, then I consider that I have detected something that obscures the more distant stars--that is, a dust cloud absorbing the light of stars located behind it.