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. 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.
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