Orion molecular cloud complex

The constellation Orion with part of the Orion molecular cloud complex. The entire complex is larger than the image section.

The Orion Molecular Cloud Complex (also known as the Orion Complex for short ) is a huge complex of molecular clouds . He is in the night sky in the constellation Orion . It is between about 1000 and 1500 light years away from our solar system - a distance from the literature is about 414 parsecs , that is 1350 light years - and is several hundred light years in size. Its total mass is estimated to be around 300,000 solar masses .

The Orion Molecular Cloud Complex is also considered part of the Orion Monoceros (Molecular Cloud) complex . This also includes the giant molecular cloud Monoceros R2 in the neighboring constellation Unicorn . The entire complex is - like the solar system - in the Orion arm of the Milky Way .

observation

Most of the areas of the Orion molecular cloud complex can hardly be detected in the visible light range. It glows primarily in infrared wavelengths and can be examined astronomically by infrared astronomy as well as by measuring accompanying trace gases such as carbon monoxide . However, it also contains dark nebulae , emission nebulae , and reflection nebulae that can be observed with binoculars and small telescopes , and some zones such as the Orion Nebula are even visible to the naked eye.

Regions and Objects

This map shows the location of Orion A with the Orion Nebula, Orion B, Barnard's Loop, the Northern Filament and the Lambda Orionis Ring, as well as Monoceros R2. For this image, images from the IRAS space telescope (1983) were combined with those from other telescopes that recorded interstellar carbon monoxide .

The Orion molecular cloud complex is a structure of gravitationally bound giant molecular clouds (English abbreviation: GMC), a so-called "GMC Complex". He is the closest of the solar system "GMC Complex" and contains, among other things, the two GMCs Orion A and Orion B . Each of these is about 100 light years in size and about 100,000 solar masses. They are among the most active nearby star formation regions in the night sky. They host protoplanetary disks and young stars that are 12 million years old and younger. There is also a population of young stars around the star Meissa (λ Orionis), which marks Orion's head.

In the Orion molecular cloud complex there are also comparatively older stars, which, however, are no longer associated with the molecular clouds. These include the three stars of the Orion Belt (in the Orion OB1b area ) and the star group northwest of it (Orion OB1a).

The regions and objects of the complex include the following:

• The giant molecular cloud Orion A
  • The Orion Molecular Cloud 1 (OMC-1)
    • The H-II area Orion Nebula (M 42, part of Orion's Sword)
      • The Kleinmann Low Nebula , the center of the Orion Nebula
      • HH1 and HH2 , the first Herbig-Haro objects recognized
    • The H-II area M 43 , which borders the Orion Nebula
    • The Becklin-Neugebauer object discovered in 1967 , probably a protostar
  • The Orion Molecular Cloud 2 (OMC-2)
  • The Orion Molecular Cloud 3 (OMC-3)
  • The Orion Molecular Cloud 4 (OMC-4)
  • The H-II area Sh2-279 (with the reflection nebula "The Running Man Nebula", part of the sword of Orion)
  • The open star cluster with gas nebula NGC 1980 (part of the sword of Orion)
  • The open star cluster NGC 1981
  • The Reflection Nebula NGC 1999 (Keyhole Nebula)
  • The Dark Nebula LDN 1641
  • HH34 , a Herbig-Haro object with symmetrical bow shock waves
• The giant molecular cloud Orion B
  • The Flame Nebula (NGC 2024)
  • The emission nebula IC 434 , which illuminates the Horsehead Nebula and makes it visible
  • The Horsehead Nebula (Barnard 33), part of a dark cloud
  • The reflection nebula M 78 (NGC 2068)
  • McNeil's Nebula , a variable nebula discovered in 2004 near M78
  • The Orion East Cloud ( LDN 1621 and LDN 1622 )
  • HH24 , HH25 and HH26 , three Herbig-Haro objects
  • HH111 , one of the most famous Herbig Haro objects
• The Northern Filament
• The star association ( OB association ) Orion OB1
  • The Orion Belt (three very bright stars in a row of stars )
  • The Sigma Orionis system of five stars
  • The system 25 Orionis
• The O-shaped ring Sh2-264 around the head of Orion (Sharpless 264, Lambda Orionis ring)
  • The open star cluster Collinder 69 from about 40 stars, including Meissa (also called the λ-Orionis cluster)
  • The Barnard Dark Cloud 30
  • The Barnard Dark Cloud 35
• The Orion-Eridanus super-bubble
  • The large, O-shaped emission nebula Barnard's Loop (Sh2-276)
  • Eridanus Loop (Sh2-245)

A more complete list can be found, for example, in Maddalena et al. (1986) Table 1.

Possible origin

The predecessor of the Orion-Monoceros complex could have formed when a huge gas cloud coming from the direction of the southern galactic hemisphere hit the Milky Way at high speed and was shattered into fragments. Tidal forces force the fragments to oscillate relative to the galactic disk. After one pass, the fragments are again about 150 parsecs (about 9 °) below the plane of the Milky Way. This origin hypothesis coincides, among other things, with certain measured velocity patterns of the complex. However, the speed patterns show strong turbulence and are also subject to other influencing factors such as stellar winds , so that they are correspondingly complicated to interpret.

Individual evidence

1. ↑ ^{a b} Bruce T. Draine: Physics of the Interstellar and Intergalactic Medium . Princeton University Press, 2011, ISBN 978-0-691-12214-4 , pp. 358 ( limited preview in Google Book Search).
2. ↑ Linda K. Glover: The Great National Geographic Encyclopedia Universe . National Geographic De, 2005, ISBN 978-3-937606-26-2 , pp. 58 ( limited preview in Google Book search).
3. ↑ John Bally, Steve Heathcote, Bo Reipurth, Jon Morse, Patrick Hartigan, Richard Schwartz: Hubble Space Telescope Observations of Proper Motions in Herbig-Haro Objects 1 and 2 . In: AJ . 123, No. 5, May 2002, ISSN  0004-6256 , pp. 2627-2657. bibcode : 2002AJ .... 123.2627B . doi : 10.1086 / 339837 .
4. ↑ Orion's Big Head Revealed in Infrared . NASA . Retrieved February 24, 2015.
5. ^ RJ Maddalena, M. Morris, J. Moscowitz, P. Thaddeus: The Large System of Molecular Clouds in Orion and Monoceros . In: Astrophysical Journal . 303, April 1986, ISSN  0004-637X , p. 375. bibcode : 1986ApJ ... 303..375M . doi : 10.1086 / 164083 .
6. ^ Norbert S. Schulz: The Formation and Early Evolution of Stars: From Dust to Stars and Planets . Springer Science & Business Media, 2012, ISBN 978-3-642-23926-7 , pp. 309 ( limited preview in Google Book search).

Web links

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