A dark nebula or absorption nebula is a type of interstellar cloud , particularly molecular clouds , that is so dense that it obscures the visible wavelengths of light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains in the coldest, densest parts of molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules . Like other interstellar dust or material, the things it obscures are visible only using radio waves in radio astronomy or infrared in infrared astronomy .
6-490: The Dark Doodad Nebula is a dark nebula near the globular cluster NGC 4372 , much closer than the centre of the galaxy and in the galactic plane, having a length of nearly three degrees of arc. Although officially unnamed, this long molecular cloud has come to be known under this name. It can be found in the southern constellation of Musca (the Fly) with strong binoculars. This cloud consists of regions of dense gas and dust, and
12-424: Is essential to understanding star formation . The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take on convoluted serpentine shapes. The closest and largest dark nebulae are visible to the naked eye, since they are the least obscured by stars in between Earth and the nebula, and because they have the largest angular size , appearing as dark patches against
18-753: Is one of the closest star forming regions to the Solar System. It was described in Sky & Telescope as one of the finest dark nebulae—one that is "wonderful, winding, and very definite". Just to the east of the southern end of the Dark Doodad is NGC 4372. It has also been called the Musca nebula and grouped as the Musca-Chamaeleonis Molecular Cloud . The nebula was catalogued by Aage Sandqvist, astronomer at Stockholm Observatory , in 1977. The name Dark Doodad
24-586: The brighter background of the Milky Way like the Coalsack Nebula and the Great Rift . These naked-eye objects are sometimes known as dark cloud constellations and take on a variety of names. In the inner molecular regions of dark nebulae, important events take place, such as the formation of stars and masers . Along with molecular clouds, dark nebula make up molecular cloud complexes . Dark nebula form in
30-413: The passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C O (CO with oxygen as the O isotope ), CS, NH 3 ( ammonia ), H 2 CO ( formaldehyde ), c-C 3 H 2 ( cyclopropenylidene ) and a molecular ion N 2 H ( diazenylium ), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development
36-502: Was given to it by American amateur astronomer and writer Dennis di Cicco in 1986 upon seeing an image he took from Alice Springs in central Australia. Steven Coe gave it the name Sandqvist 149 , because he believed it should be named after the astronomer who found it, though he acknowledges that the popular term prevails. Dark nebula Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block
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