Great Rift (astronomy)
In astronomy, the Great Rift (sometimes called the Dark Rift, or less commonly the Dark River), is an aggregation of overlapping, non-luminous, molecular dust clouds that lie between the Solar System and the Sagittarius Arm of the Milky Way galaxy. They form a dark lane through the starry path of the Milky Way which, seen from Earth, is a hazy band of white light, some 30° wide, arching across the night sky. These clouds are located about 800–1,000 parsecs (2,600–3,300 ly) from Earth. The clouds are estimated to contain about 1 million solar masses of plasma and dust.
Starting at the constellation of Cygnus, where it is known as the Cygnus Rift or Northern Coalsack, the Great Rift stretches to Aquila; to Ophiuchus, where it broadens out; to Sagittarius, where it obscures the Galactic Center; and finally to Centaurus. One of the most important regions it obscures is the Cygnus OB2 association, a large cluster of young stars and one of the largest regions of star formation near Earth. Similar dark rifts can be seen in many edge-on galaxies, such as NGC 891 in Andromeda and NGC 4565 (the Needle Galaxy) in Coma Berenices.
This image shows a mysterious ring composed of very dense and cold gas and dust around the Galactic Center.
- Green, Gregory M; Schlafly, Edward F; Finkbeiner, Douglas P; Rix, Hans-Walter; Martin, Nicolas; Burgett, William; Draper, Peter W; Flewelling, Heather; Hodapp, Klaus; Kaiser, Nicholas; Kudritzki, Rolf Peter; Magnier, Eugene; Metcalfe, Nigel; Price, Paul; Tonry, John; Wainscoat, Richard (2015). "A Three-Dimensional Map of Milky Way Dust". The Astrophysical Journal. 810: 25. arXiv:1507.01005. Bibcode:2015ApJ...810...25G. doi:10.1088/0004-637X/810/1/25.
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