The Horsehead Nebula (also known as Barnard 33) is a small dark nebula in the constellation Orion.[2] The nebula is located just to the south of Alnitak, the easternmost star of Orion's Belt, and is part of the much larger Orion molecular cloud complex. It appears within the southern region of the dense dust cloud known as Lynds 1630, along the edge of the much larger, active star-forming H II region called IC 434.[3]

Horsehead Nebula
Dark nebula
The Horsehead Nebula. The reflection nebula NGC 2023 is in the bottom left corner and the nebula itself near the centre, in the shape of the head of a horse. Photo taken in 2011
Observation data: J2000.0 epoch
Right ascension05h 40m 59.0s
Declination−02° 27′ 30.0"
Distance1,375±54[1][note 1] ly   (422±17[1] pc)
Apparent magnitude (V)6.8
Apparent dimensions (V)8 × 6 arcmins
Physical characteristics
Radius3.5 ly
DesignationsBarnard 33, LDN 1630, IC 434
See also: Lists of nebulae

The Horsehead Nebula is approximately 422 parsecs or 1,375 light-years from Earth.[1][3] It is one of the most identifiable nebulae because of its resemblance to a horse's head.[4]

History Edit

The nebula was discovered by Scottish astronomer Williamina Fleming in 1888 on a photographic plate taken at the Harvard College Observatory.[5][6] One of the first descriptions was made by E. E. Barnard, describing it as: "Dark mass, diam. 4′, on nebulous strip extending south from ζ Orionis", cataloguing the dark nebula as Barnard 33.[7]

Structure Edit

The dark cloud of dust and gas is a region in the Orion molecular cloud complex, where star formation is taking place. It is located in the constellation of Orion, which is prominent in the winter evening sky in the Northern Hemisphere and the summer evening sky in the Southern Hemisphere.

Colour images reveal a deep-red colour that originates from ionised hydrogen gas () predominantly behind the nebula, and caused by the nearby bright star Sigma Orionis. Magnetic fields channel the gases, leaving the nebula into streams, shown as foreground streaks against the background glow.[8] A glowing strip of hydrogen gas marks the edge of the enormous cloud, and the densities of nearby stars are noticeably different on either side.

Heavy concentrations of dust in the Horsehead Nebula region and neighbouring Orion Nebula are localized into interstellar clouds, resulting in alternating sections of nearly complete opacity and transparency.[9] The darkness of the Horsehead is caused mostly by thick dust blocking the light of stars behind it.[10] The lower part of the Horsehead's neck casts a shadow to the left.[11] The visible dark nebula emerging from the gaseous complex is an active site of the formation of "low-mass" stars. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming.

In popular culture Edit

The Horsehead Nebula has been featured frequently in popular culture.

The Nebula Kingdoms in Isaac Asimov's Galactic Empire series are a group of planetary systems located near the Horsehead Nebula.

The nebula is featured in the 1990s children's animated series, Widget where the main setting is on a planet located in the Horsehead Nebula. It features in the opening credits of the show.

The British sci-fi series, Doctor Who features the Horsehead Nebula throughout the first series of the revived show where it is mentioned and seen throughout the series in "World War Three" and "Bad Wolf". The Ood, a species featured on the show, live on the Ood Sphere which is located in the Horsehead Nebula.

The nebula is mentioned in the second series of Good Omens, where it is revealed that Crowley (played by David Tennant) helped create it as an angel.

The Horsehead Nebula has also been featured in documentaries of its discoverer, Williamina Fleming.

Image gallery Edit

See also Edit

Notes Edit

  1. ^ Based on the parallax of 2MASS J05405172-0226489, a young stellar object embedded in the 'head' of the nebula.

References Edit

  1. ^ a b c Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
  2. ^ Arnett, Bill (2000). "Horsehead Nebula". Retrieved July 21, 2014.
  3. ^ a b "VLT Images the Horsehead Nebula". European Southern Observatory. 25 January 2002. Retrieved 1 March 2019.
  4. ^ Sharp, Nigel (2014). "The Horsehead Nebula". National Optical Astronomy Observatory. Association of Universities for Research in Astronomy. Archived from the original on March 13, 2020. Retrieved July 21, 2014.
  5. ^ Alex Newman (28 August 2017). "Unearthing the legacy of Harvard's female 'computers'". BBC News. Retrieved 28 August 2017.
  6. ^ Cannon, Annie J. (June 1911). "Williamina Paton Fleming". Science (published June 30, 1911). 33 (861): 987–988. Bibcode:1911Sci....33..987C. doi:10.1126/science.33.861.987. PMID 17799863.
  7. ^ Barnard, E. E. (1919). "On the dark markings of the sky, with a catalogue of 182 such objects". Astrophysical Journal. 49: 1–24. Bibcode:1919ApJ....49....1B. doi:10.1086/142439.
  8. ^ "The Horsehead Nebula/IC434". National Optical Astronomy Observatory. NOAO. Retrieved 23 October 2020.
  9. ^ Morgan, W.W.; Lodén, Kerstin (1966). "Some Characteristics of the Orion Association". Vistas in Astronomy. 8 (1): 83–88. Bibcode:1966VA......8...83M. doi:10.1016/0083-6656(66)90023-7. ISSN 0083-6656.
  10. ^ 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.
  11. ^ Nemiroff, R.; Bonnell, J., eds. (21 July 2009). "The Horsehead Nebula". Astronomy Picture of the Day. NASA. Retrieved 12 May 2014.

External links Edit