IC 5146

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IC 5146
Reflection nebula
emission nebula
Optical image of IC 5146
Observation data: J2000 epoch
Right ascension 21h 53m 28.7s
Declination +47° 16′ 01″
Distance 3300 ly   (1000 pc)
Apparent magnitude (V) +7.2
Apparent dimensions (V) 12′
Constellation Cygnus
Designations Cocoon Nebula, Caldwell 19, Sh 2-125
See also: Lists of nebulae

IC 5146 (also Caldwell 19, Sh 2-125, 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 21h 53.5m, dec+47° 16′. 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.

View of the IC 5146 star-forming region from ESA's Herschel Space Telescope

Young Stellar Objects[edit]

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". 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]



  1. ^ a b Eicher, David J. (1988). The Universe from Your Backyard: A Guide to Deep-Sky Objects from Astronomy Magazine. AstroMedia (Kalmbach Publishing Company). ISBN 0-521-36299-7. 
  2. ^ a b Sanqunetti, Doug (2007). "IC 5146 - Cocoon Nebula". dougsastro.net. Retrieved 2008-08-06. [permanent dead link]
  3. ^ O'Meara, Stephen James: The Caldwell Objects, Sky Publishing Corporation ISBN 0-933346-97-2 page 80
  4. ^ a b Pasachoff, Jay M. (2000). "Atlas of the Sky". Stars and Planets. New York, NY: Peterson Field Guides. p. 578. ISBN 0-395-93432-X. 
  5. ^ a b Cannistra, Steve (2004). "Cocoon Nebula". starrywonders.com. Retrieved 2008-08-06. 
  6. ^ Nemiroff, R.; Bonnell, J., eds. (2002-10-14). "IC 5146: The Cocoon Nebula". Astronomy Picture of the Day. NASA. Retrieved 2008-08-06. 
  7. ^ Harvey, Paul M.; Huard, Tracy L.; Jørgensen, Jes K.; Gutermuth, Robert A.; Mamajek, Eric E.; Bourke, Tyler L.; Merín, Bruno; Cieza, Lucas; Brooke, Tim; Chapman, Nicholas; Alcalá, Juan M.; Allen, Lori E.; Evans II, Neal J.; Di Francesco, James; Kirk, Jason M. (2008). "TheSpitzerSurvey of Interstellar Clouds in the Gould Belt. I. IC 5146 Observed With IRAC and MIPS". The Astrophysical Journal. 680 (1): 495–516. Bibcode:2008ApJ...680..495H. doi:10.1086/587687. ISSN 0004-637X. 
  8. ^ Getman, Konstantin V.; Broos, Patrick S.; Kuhn, Michael A.; Feigelson, Eric D.; Richert, Alexander J. W.; Ota, Yosuke; Bate, Matthew R.; Garmire, Gordon P. (2017). "Star Formation In Nearby Clouds (SFiNCs): X-Ray and Infrared Source Catalogs and Membership". The Astrophysical Journal Supplement Series. 229 (2): 28. arXiv:1612.05282Freely accessible. Bibcode:2017ApJS..229...28G. doi:10.3847/1538-4365/229/2/28. ISSN 1538-4365. 
  9. ^ Weidner, Carsten; Kroupa, Pavel (2005). "The maximum stellar mass, star-cluster formation and composite stellar populations". Monthly Notices of the Royal Astronomical Society. 365 (4): 1333–1347. arXiv:astro-ph/0511331Freely accessible. Bibcode:2006MNRAS.365.1333W. doi:10.1111/j.1365-2966.2005.09824.x. ISSN 0035-8711. 
  10. ^ Reipurth, Bo (2008). Handbook of star forming regions. San Francisco: Astronomical Society of the Pacific. ISBN 978-1-58381-670-7. 

External links[edit]

Coordinates: Sky map 21h 53m 32s, +47° 16′ 06″