Great Rift (astronomy)

The Milky Way near Cygnus showing the dark lane of the Great Rift.

In astronomy, the Great Rift (sometimes called the Dark Rift or, less commonly, Dark River) is a series of overlapping, non-luminous, molecular dust clouds that are located between the Solar System and the Sagittarius Arm of the Milky Way Galaxy at a distance of about 100 parsecs or about 300 light years (2×10¹⁵ miles or 3×10¹⁵ kilometers) from Earth. The clouds are estimated to contain about 1 million solar masses of plasma and dust.^[1]

To the naked eye, the Great Rift appears as a dark lane that divides the bright band of the Milky Way lengthwise, through about one-third of its extent, and is flanked by lanes of numerous stars.^[1]

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 the Earth. A similar dark band can be seen in edge-on distant galaxies, such as NGC 891 in Andromeda.^[2]

See also

• Dark-cloud constellations

Notes

1. ^ ^{a b} Great Rift: Dark area in the Milky Way 2010 EarthSky Communications. Accessed June 2010
2. ^ Pitts, Sam. "NGC 891 Edge on Galaxy (HV19)". Sams Astro. http://samsastro.com/images/deepsky/NGC0891b.htm. Retrieved 2009-04-25. 

References

• "The Great Rift". Encyclopedia Britannica Online. 2009. http://www.britannica.com/EBchecked/topic/243658/Great-Rift. Retrieved 2009-04-25. 
• "Great Rift". Sci-Tech Dictionary:. http://www.answers.com/topic/great-rift. Retrieved 2009-04-25. 
• Kaler, Jim. "The Milky Way - From STARS". University of Illinois at Urbana-Champaign. Department of Astronomy. pp. Maps 2 and 5. http://stars.astro.illinois.edu/sow/mw.html. Retrieved 2009-04-25. 
• Dark River, Wide Field by Rogelio Bernal Andreo, at APOD