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Cygnus Rift

Northern Coalsack

Proper NamesCygnus Rift, Northern Coalsack
Messier NumberNone
NGC/IC NumberNone
ConstellationCygnus
Right Ascension20h 20m 54s (approximate centre)
Declination+36° 27' 30" (approximate centre)
Distancec.300 light years
c.90 parsecs
MagnitudeN/A
DimensionsApparent: 318' x 480'
Actual: 28 x 42 light years
Optimum VisibilityAugust
NotesA dark cloud that marks the northern extent of the Great Rift, a band of obscuring dust that runs along a significant length of the band of the Milky Way.

A dark mass in the central regions of Cygnus, directly southward of the star Deneb in the middle of the band of the Milky Way. The Cygnus Rift is approximately circular in shape, with an angular diameter of about 6° (or about twelve times the apparent diameter of the Moon's disc).

The Cygnus Rift is not in fact a 'rift' at all, but a dark cloud of dust that obscures the light from the stars and nebulae behind it (for this reason it is sometimes called the Northern Coalsack, after a similar structure in the southern sky). It forms the eastern extent of a long trail of obscuring dust, the Great Rift, that runs westward from Cygnus and stretches along about a third of the Milky Way's length.

The dark mass of the Cygnus Rift is about three hundred light years from the Solar System, and far behind it - at least a thousand light years further away - lie vast clouds of ionising hyndrogen creating a field of emission nebulae. These bright nebulae are almost entirely obscured by the darkness of the Rift, but their fringes can be seen, etched into elaborate shapes by the intervening dust. The North America Nebula is part of this fringe, stencilled by the edges of the Rift to give it a remarkable resemblance to the continent of North America on Earth. The nearby Pelican Nebula belongs to the same field, and on the opposite side of the Cygnus Rift part of another H II region can be glimpsed, known as the Sadr Region or the Gamma Cygni Nebula.

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