Jump to content

Dark nebula: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
Undid revision 824825507 by Alo18 (talk) Removed sentence containing grammatical and spelling errors and an incorrectly formatted reference.
Undid good-faith revision 824152142 by Dinucretu (talk) Information on size of rho Oph is not consistent with wiki article on this object. Also, citation is a non-accessible paywalled source.
Line 2: Line 2:
{{for|the video game|Dark Nebula (video game)}}
{{for|the video game|Dark Nebula (video game)}}
{{Star formation}}
{{Star formation}}
A '''dark nebula''' or '''absorption nebula''' is a type of [[interstellar cloud]] that is so dense that it obscures the light from objects behind it, such as background stars and [[emission nebula|emission]] or [[reflection nebula|reflection]] nebulae. Dark nebulae range in size from minute, more or less spherical Bok Globules , usually seen in photographs against the bright glow of [[Emission nebula|emission nebulae]] , through larger features like the [[Horsehead Nebula|horsehead nebula]] to the naked-eye clouds of the southern coalsack and the gigantic RHO Ophiuchi Dark Cloud , which affects 1000 square degrees (2%) of the [[Bok globule|sky]]<ref>{{Cite web|url=https://search.credoreference.com/content/entry/philipsastronomy/dark_nebula/0|title=dark nebula {{!}} Astronomy Encyclopedia - Credo Reference|website=search.credoreference.com|language=en|access-date=2018-02-05}}</ref>[[Bok globule|.The]] [[extinction (astronomy)|extinction]] of the light is caused by [[cosmic dust|interstellar dust]] grains located in the coldest, densest parts of larger{{clarify|date=February 2009|what size is larger? Over 3 solar masses maybe? Do dust grains also cause extinction in smaller, Bok globule-size, clouds?}} [[molecular cloud]]s. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called [[Bok globule]]s. Like other interstellar dust or material, things it obscures are only visible using [[radio waves]] in [[radio astronomy]] or [[infrared]] in [[infrared astronomy]].
A '''dark nebula''' or '''absorption nebula''' is a type of [[interstellar cloud]] that is so dense that it obscures the light from objects behind it, such as background stars and [[emission nebula|emission]] or [[reflection nebula|reflection]] nebulae. The [[extinction (astronomy)|extinction]] of the light is caused by [[cosmic dust|interstellar dust]] grains located in the coldest, densest parts of larger{{clarify|date=February 2009|what size is larger? Over 3 solar masses maybe? Do dust grains also cause extinction in smaller, Bok globule-size, clouds?}} [[molecular cloud]]s. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called [[Bok globule]]s. Like other interstellar dust or material, things it obscures are only visible using [[radio waves]] in [[radio astronomy]] or [[infrared]] in [[infrared astronomy]].


Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C<sup>18</sup>O (CO with [[oxygen]] as the [[Oxygen-18|<sup>18</sup>O isotope]]), CS, NH<sub>3</sub> ([[ammonia]]), H<sub>2</sub>CO ([[formaldehyde]]), c-C<sub>3</sub>H<sub>2</sub> ([[cyclopropenylidene]]) and a molecular ion N<sub>2</sub>H<sup>+</sup> ([[diazenylium]]), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding [[star formation]].<ref>[http://iopscience.iop.org/1538-3881/124/5/2749 James Di Francesco ''et al.'', 2002, "Abundances of Molecular Species in Barnard 68", ''The Astronomical Journal'', 124, 2749]</ref><ref>[http://www.eso.org/public/outreach/press-rel/pr-1999/phot-29-99.html ESO - eso9934 - Secrets of a Dark Cloud] {{webarchive|url=https://web.archive.org/web/20090204200348/http://eso.org/public/outreach/press-rel/pr-1999/phot-29-99.html |date=2009-02-04 }}</ref>
Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C<sup>18</sup>O (CO with [[oxygen]] as the [[Oxygen-18|<sup>18</sup>O isotope]]), CS, NH<sub>3</sub> ([[ammonia]]), H<sub>2</sub>CO ([[formaldehyde]]), c-C<sub>3</sub>H<sub>2</sub> ([[cyclopropenylidene]]) and a molecular ion N<sub>2</sub>H<sup>+</sup> ([[diazenylium]]), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding [[star formation]].<ref>[http://iopscience.iop.org/1538-3881/124/5/2749 James Di Francesco ''et al.'', 2002, "Abundances of Molecular Species in Barnard 68", ''The Astronomical Journal'', 124, 2749]</ref><ref>[http://www.eso.org/public/outreach/press-rel/pr-1999/phot-29-99.html ESO - eso9934 - Secrets of a Dark Cloud] {{webarchive|url=https://web.archive.org/web/20090204200348/http://eso.org/public/outreach/press-rel/pr-1999/phot-29-99.html |date=2009-02-04 }}</ref>

Revision as of 17:13, 12 February 2018

See also: Dark Cloud (disambiguation)
For the video game, see Dark Nebula (video game).
Star formation
Object classes
Theoretical concepts

A dark nebula or absorption nebula is a type of interstellar cloud that is so dense that it obscures the light from objects behind it, such as background stars and emission or reflection nebulae. The extinction of the light is caused by interstellar dust grains located in the coldest, densest parts of larger[clarification needed] molecular clouds. Clusters and large complexes of dark nebulae are associated with Giant Molecular Clouds. Isolated small dark nebulae are called Bok globules. Like other interstellar dust or material, things it obscures are only visible using radio waves in radio astronomy or infrared in infrared astronomy.

Dark clouds appear so because of sub-micrometre-sized dust particles, coated with frozen carbon monoxide and nitrogen, which effectively block the passage of light at visible wavelengths. Also present are molecular hydrogen, atomic helium, C18O (CO with oxygen as the 18O isotope), CS, NH3 (ammonia), H2CO (formaldehyde), c-C3H2 (cyclopropenylidene) and a molecular ion N2H+ (diazenylium), all of which are relatively transparent. These clouds are the spawning grounds of stars and planets, and understanding their development is essential to understanding star formation.[1][2]

The form of such dark clouds is very irregular: they have no clearly defined outer boundaries and sometimes take on convoluted serpentine shapes. The largest dark nebulae are visible to the naked eye, appearing as dark patches against the brighter background of the Milky Way like the Coalsack Nebula and the Great Rift. These naked-eye objects are sometimes known as dark cloud constellations and take on a variety of names.

In the inner outer molecular regions of dark nebulae, important events take place, such as the formation of stars and masers.

  • Dark nebula LDN 1768 contains protostars.[3]
    Dark nebula LDN 1768 contains protostars.[3]
  • Dark nebula called LDN1774, taken by the Wide Field Imager, an instrument mounted on ESO’s 2.2-meter MPG/ESO telescope at La Silla.[4]
    Dark nebula called LDN1774, taken by the Wide Field Imager, an instrument mounted on ESO’s 2.2-meter MPG/ESO telescope at La Silla.[4]
  • Dark nebula LDN 483 is located about 700 light-years away in the constellation of Serpens (The Serpent).[5]
    Dark nebula LDN 483 is located about 700 light-years away in the constellation of Serpens (The Serpent).[5]
  • Lupus 4 is a dense pocket of gas and dust where new stars are expected to form.[6]
    Lupus 4 is a dense pocket of gas and dust where new stars are expected to form.[6]

See also

Notes

  1. ^ James Di Francesco et al., 2002, "Abundances of Molecular Species in Barnard 68", The Astronomical Journal, 124, 2749
  2. ^ ESO - eso9934 - Secrets of a Dark Cloud Archived 2009-02-04 at the Wayback Machine
  3. ^ "All Quiet in the Nursery?". Retrieved 23 March 2016.
  4. ^ "A Hole in the Sky". Retrieved 14 June 2015.
  5. ^ "The dark nebula LDN 483". www.eso.org. European Southern Observatory. Retrieved 14 January 2015.
  6. ^ "Cosmic Forecast: Dark Clouds Will Give Way to Sunshine". www.eso.org. European Southern Observatory. Retrieved 8 September 2014.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Dark_nebula&oldid=825304235"