|This article needs additional citations for verification. (July 2010)|
|Observation data (Epoch J2000.0)|
|Type||dark nebula/diffuse nebulae|
|Right ascension||05h 40m 59.0s|
|Declination||−02° 27′ 30.0"|
|Distance (ly)||1,500 ly|
|Apparent dimensions (V)||8 × 6 arcmins|
|Notable features||Resembles a horse's head|
|Other designations||IC 434, Barnard 33,
LDN 1630, M3T 31,
|See also: Dark nebula, Lists of nebulae|
The Horsehead Nebula (also known as Barnard 33 in emission nebula IC 434) is a dark nebula in the constellation Orion. the nebula is located just to the south of the star Alnitak, which is farthest east on Orion's Belt, and is part of the much larger Orion Molecular Cloud Complex. The nebula was first recorded in 1888 by Scottish astronomer Williamina Fleming on photographic plate B2312 taken at the Harvard College Observatory. The Horsehead Nebula is approximately 1500 light years from Earth. It is one of the most identifiable nebulae because of the shape of its swirling cloud of dark dust and gases, which bears some resemblance to a horse's head when viewed from Earth.
The red or pinkish glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funnelled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.
The nebula exhibits a noticeable change in the density of the stars which indicates that a red ribbon of radiant red hydrogen gas at the precipice of a sizable dark cloud. The underside of the horse's visible 'neck' reflects this concept of shade and density because it casts a great shadow across the field of view just below the horse's 'muzzle'. The visible heart of the nebula emerges from the gaseous complex to serve as an active site of the formation of "low-mass" stars. A glowing strip of hydrogen gas marks the edge of the massive cloud and noticeable densities of stars are present on either side.
The dark cloud of dust and gas is a region in the Orion Nebula where star formation is taking place right now. A complex housing forming stars, known as a stellar nursery, can contain over 100 known organic and inorganic gases as well as dust consisting of large and complex organic molecules. The region of the Orion Nebula containing the Horsehead is a stellar nursery. The darkness of the massive nebula is not explained by this dust and gas, but by the complex blocking the light of stars behind it. The heavy concentrations of dust in the Horsehead Nebula region and neighbouring Orion Nebula are localized, resulting in alternating sections of nearly complete opacity and transparency.
From the European Southern Observatory, 2002
- Arnett, Bill. http://astro.nineplanets.org/twn/b33x.html. Horsehead Nebula, 2000
- Sharp, Nigel/NOAO. http://www.noao.edu/image_gallery/html/im0057.html.
- Mayo Greenberg, J (2002). "Cosmic dust and our origins". Surface Science 500 (1-3): 793–822. Bibcode:2002SurSc.500..793M. doi:10.1016/S0039-6028(01)01555-2. ISSN 0039-6028.
- Morgan, W.W.; Lodén, Kerstin (1966). "Some Characteristics of the Orion Association". Vistas in Astronomy 8: 83–88. Bibcode:1966VA......8...83M. doi:10.1016/0083-6656(66)90023-7. ISSN 0083-6656.
Media related to Horsehead Nebula at Wikimedia Commons
- The Horsehead Nebula @ The Electronic Sky
- Hubble Observes the Horsehead Nebula
- The discovery of early photographs of the Horsehead nebula, by Waldee and Hazen
- The Horsehead Nebula in the 19th Century, by Waldee
- Detection of new nebulae by photography, by Pickering
- Horsehead Nebula at ESA/Hubble
- The Horsehead Nebula at the Astro-Photography site of Mr. T. Yoshida.
- The Horsehead-Nebula and neighboring structures in a classical view
- The Horsehead Nebula on interactive astro-photography survey at Wikisky.org
- The Horsehead Nebula at Constellation Guide