IC 5146
Template:Short description Template:Infobox nebula IC 5146 (also Caldwell 19, Sh 2-125, Barnard 168, and the Cocoon Nebula) is a reflection[1]/emission[2] nebula and Caldwell object in the constellation Cygnus. The NGC description refers to IC 5146 as a cluster of 9.5 mag stars involved in a bright and dark nebula. The cluster is also known as Collinder 470.[3] It shines at magnitude +10.0[4]/+9.3[2]/+7.2.[5] Its celestial coordinates are RA Template:RA, dec Template:DEC. It is located near the naked-eye star Pi Cygni, the open cluster NGC 7209 in Lacerta, and the bright open cluster M39.[1][4] The cluster is about 4,000 ly away, and the central star that lights it formed about 100,000 years ago;[6] the nebula is about 12 arcmins across, which is equivalent to a span of 15 light years.[5]
When viewing IC 5146, dark nebula Barnard 168 (B168) is an inseparable part of the experience, forming a dark lane that surrounds the cluster and projects westward forming the appearance of a trail behind the Cocoon.
Young Stellar Objects
IC 5146 is a stellar nursery where star-formation is ongoing. Observations by both the Spitzer Space Telescope and the Chandra X-ray Observatory have collectively identified hundreds of young stellar objects.[7][8] Young stars are seen in both the emission nebula, where gas has been ionized by massive young stars, and in the infrared-dark molecular cloud that forms the "tail". One of the most massive stars in the region is BD +46 3474, a star of class B1 that is an estimated 14±4 times the mass of the sun.[9]
Another interesting star in the nebula is BD +46 3471, which is an example of a HAeBe star, an intermediate mass star with strong emission lines in its spectrum.[10]
References
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- ↑ O'Meara, Stephen James: The Caldwell Objects, Sky Publishing Corporation Template:ISBN page 80
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External links
- Template:Cite simbad
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