Dark Nebulae

Sometimes known as absorption nebulae these are dark concentrations of gas and dust which often have stars forming inside them. Dark nebulae can be seen if they obscure part of a bright nebula (eg. the Horsehead nebula) or if they block out background stars (eg. the Coalsack).

Digitized Sky Survey image
The Horsehead Nebula

Here is a map showing many of the dark nebula regions within 2000 light years plotted onto the galactic plane. The map shows the positions of 742 dark nebulae listed by Dutra and Bica. A few bright nebulae are also marked. These dark nebulae are the important regions of star formation in our local part of the Orion Arm. For example, the famous Pleiades star cluster consists of hot young stars that formed among the dark clouds of Taurus.

A map of dark nebulae
          Major Dark Nebula Regions
        -----------------------------
Name          Equatorial    Galactic  Distance
              Coordinates  Coordinates  (ly)
               RA   Dec      l  b
Aries         03 00 +19.5   160 -34      330
Perseus       03 52 +33.2   161 -16     1150
Taurus        04 37 +27.7   172 -13      460
Orion         05 52 +02.3   204 -12     1500
Puppis        07 39 -44.9   258 -11     1500
Puppis        08 21 -36.6   255   0     1400
Vela          08 27 -50.4   267  -7     1000
Coalsack      12 25 -63.7   300  -1      520
Musca         12 28 -70.8   301  -8      490
Chamaeleon    12 34 -77.8   302 -15      590
Lupus         15 45 -34.5   339 +16      460
Lupus         16 01 -39.7   338 +10      470
Ophiuchus     16 31 -22.9   355 +17      520
Ophiuchus     16 50 -14.2     5 +19      520
Scorpius      17 11 -39.8   347   0      490
Ophiuchus     17 22 -24.3     1  +7      520
Scutum        18 33 -06.6    25  +1      650
Corona Austr. 19 14 -36.7     1 -20      520
Aquila        19 19 +11.1    46  -1     1000
Vulpecula     19 22 +23.2    57  +4      650
Cepheus       20 42 +58.6    95 +10     1400
Cepheus       20 56 +67.2   103 +14     1000
References: Dutra C, Bica E, (2002), A catalogue of dust clouds in the Galaxy, Astron Astrophys, 383, 631.

This diagram below shows where the major molecular clouds can be found along the plane of the Milky Way:

Dark nebulae in the Milky Way
References: Dame T, Hartmann D, Thaddeus P, (2001), The Milky Way in Molecular Clouds: A New Complete CO Survey, Astrophys J, 547, 792.

Below is a list of the most famous dark nebulae. These are all supposed to be easily visible with a small telescope, although I have no idea if they are or not. :)

  1            2              3      4       5     6       7       8      9
Barnard     Common           Equatorial     Galactic     Size   Distance Con
Number       Name           Coordinates    Coordinates  arcmins   (ly)
                             RA      Dec     l    b
B33      Horsehead         05 40.9 -02 28  207.0 -16.8    6'x4'   1400   Ori
 -       Coalsack          12 53.0 -63 00  303.1  -0.1  400'x300'  500   Cru
B42      Rho Ophiuchi      16 25.5 -23 26  353.7 +17.7   30'x30'   500   Oph
B65/6/7  Pipe (stem)       17 20.0 -26 54  358.6  +5.9  300'x60'   500   Oph
B72      Snake             17 23.6 -23 37    1.8  +7.0   30'x30'   600   Oph
B78      Pipe (bowl)       17 32.7 -25 36    1.3  +4.2  200'x140'  500   Oph
B86      Ink Spot          18 03.0 -27 52    2.9  -2.8    5'x3'     ?    Sgr
B87      Parrot's Head     18 04.2 -32 30  358.9  -5.2   12'x12'  1000   Sgr
B92                        18 15.6 -18 14   12.7  -0.6   15'x15'   650   Sgr
B133                       19 06.2 -06 54   28.5  -6.4   10'x5'   1000   Aql
B143                       19 41.4 +11 00   48.5  -5.9   30'x30'    ?    Aql
B348/9   Northern Coalsack 20 34.4 +42 06   81.0  +1.1  240'x240'   ?    Cyg
B352                       20 57.2 +45 54   86.5  +0.3   15'x3'   1900   Cyg
B168                       21 53.4 +47 16   94.4  -5.5  100'x10'    ?    Cyg
Column 1: The Barnard classification number of the dark nebula.
Column 2: The common name of the dark nebula.
Column 3: Right Ascension in hours and minutes for epoch 2000.
Column 4: Declination in degrees and minutes for epoch 2000.
Column 5: Galactic longitude of the nebula.
Column 6: Galactic latitude of the nebula.
Column 7: Angular size of the dark nebula in arcminutes.
Column 8: Distance to the dark nebula in light years (very approximate).
Column 9: Constellation in which the dark nebula lies.

References:
Barnard E, (1927), A photographic Atlas of selected regions of the Milky Way,
            Carnegie Inst. Washington.
Hilton J, Lahulla J, (1995), Distance measurements of Lynds galactic dark
            nebulae, Astron Astrophys Supp, 113, 325.
Dutra C, Bica E, (2002), A catalogue of dust clouds in the Galaxy, Astron 
            Astrophys, 383, 631.
Digitized Sky Survey image
The Pipe Nebula. A long dark nebula visible in the star clouds of Ophiuchus.
The Orion arm Back to the Orion Arm page