Barnard's Loop
| Barnard's Loop | |
|---|---|
 Barnard's Loop can be seen on this image as a diffuse red semicircle. |
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| Observation data: J2000.0 epoch | |
| Type | Emission |
| Right ascension | 05h 31m |
| Declination | -04° 54′ |
| Distance | 1,600 ly |
| Apparent magnitude (V) | 5 |
| Apparent dimensions (V) | 10° |
| Constellation | Orion |
| Physical characteristics | |
| Radius | 150 ly |
| Absolute magnitude (V) | - |
| Notable features | - |
| Other designations | Sh 2-276 |
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See also: Diffuse nebula, Lists of nebulae |
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Barnard's Loop (catalogue designation Sh 2-276) is an emission nebula in the constellation of Orion. It is part of the Orion Molecular Cloud Complex which also contains the bright Horsehead and Orion nebulae. The loop takes the form of a large arc centred approximately on the Orion Nebula. The stars within the Orion Nebula are believed to be responsible for ionizing the loop.
The loop extends over about 600 arcminutes as seen from Earth, covering much of Orion. It is well seen in long-exposure photographs, although observers under very dark skies may be able to see it with the naked eye.
It is estimated to lie at a distance of approximately 1600 light years, giving it actual dimensions of about 300 light years across. It is thought to have originated in a supernova explosion about 2 million years ago, which may have also created several known runaway stars, including AE Aurigae, Mu Columbae and 53 Arietis, which are believed to have been part of a multiple star system in which one component exploded as a supernova.[1]
Although this faint nebula was certainly observed by earlier astronomers, it is named after the pioneering astrophotographer E. E. Barnard who photographed it and published a description in 1894.[2]
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Above photo of Barnard's Loop nebula in inverted black and white of the red channel; the loop can now be seen better.
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Barnard's Loop imaged with a combination of white light and hydrogen alpha light bringing out the color and detail of this vast structure. Messier 42 and the Horsehead Nebula can be seen as well. Courtesy of Hunter Wilson.
References [edit]
- ^ "The Internet Encyclopedia of Science: Barnard's Loop (Sh 2-276)". David Darling. Archived from the original on 12 March 2008. Retrieved 2008-04-22.
- ^ Barnard, E. E. (1894). "The great photographic nebula of Orion, encircling the belt and theta nebula". Popular Astronomy 2: 151–154. Bibcode:1894PA......2..151B.
- Gaylard M.J. (1984), Detection of the H 142-alpha line from the Barnard Loop, Monthly Notices of the Royal Astronomical Society, v. 211, p.149
- Reynolds R.J., Ogden P.M. (1979), Optical evidence for a very large, expanding shell associated with the I Orion OB association, Barnard's loop, and the high galactic latitude H-alpha filaments in Eridanus, Astrophysical Journal, v. 229, p.942
External links [edit]
- Photograph identifying several nebulae in Orion
- Encyclopaedia of Astrobiology, Astronomy, and Spaceflight entry
- The Scale of the Universe (Astronomy Picture of the Day 12 March 2012)
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