Editing Zone of Avoidance

{{Short description|Area of sky obscured by the Milky Way}}
[[File:Milky_Way_infrared.jpg|thumb|300x300px|The Milky Way creates a Zone of Avoidance for local observers.]]
The '''Zone of Avoidance''' ('''ZOA''', '''ZoA'''), or '''Zone of Galactic Obscuration''' ('''ZGO'''),<ref name="VC-20221103">{{cite news |last=Ferreira |first=Becky |title=Scientists Discover Huge 'Extragalactic Structure' in Hidden Region of Space - The obscured "zone of avoidance" in space is a place of mystery, and scientists are peering at what's inside it. |url=https://www.vice.com/en/article/scie-discover-huge-extragalactic-structure-in-zone-of-avoidance/ |date=3 November 2022 |work=[[Vice (magazine)|Vice]] |access-date=3 November 2022 }}</ref><ref name="SA-20200714">{{cite news |last=Starr |first=Michelle |title=A Giant 'Wall' of Galaxies Has Been Found Stretching Across The Universe |url=https://www.sciencealert.com/a-giant-wall-of-galaxies-has-been-found-stretching-across-the-universe |date=14 July 2020 |work=ScienceAlert.com |access-date=19 July 2020 }}</ref> is the area of the sky that is obscured by the [[Milky Way]].<ref>{{Cite book|title=Astronomy encyclopedia|last1=Robinson|first1=L. J.|last2=Tirion|first2=W.|last3=Moore|first3=P.|publisher=Philip's|year=2002|location=London, UK|via=Credo Reference}}</ref>

The Zone of Avoidance was originally called the '''Zone of Few Nebulae''' in an 1878 paper by English astronomer [[Richard Proctor]] that referred to the distribution of "[[nebula]]e" in [[John Herschel]]'s ''[[Catalogue of Nebulae and Clusters of Stars|General Catalogue of Nebulae]]''.<ref name="Kraan-Korteweg">Kraan-Korteweg & Lahav. 2000, p. 2</ref>

==Background==
When viewing space from Earth, the [[attenuation]], [[interstellar dust]] and [[star]]s in the plane of the Milky Way (the [[galactic plane]]) obstruct the view of around 20% of the extragalactic sky at [[visible wavelength]]s. As a result, optical galaxy catalogues are usually incomplete close to the galactic plane.

==Modern developments==
[[File:Galaxymap.com, map 12000 parsecs (2022).png|thumb|300x300px|The limits of observation as visualized by the Milky Way's star density map. Source: [[Gaia (spacecraft)|''Gaia'' spacecraft]]'s 2021 data release]]
Many projects have attempted to bridge the gap in knowledge caused by the Zone of Avoidance. The dust and gas in the Milky Way cause [[Extinction (astronomy)|extinction]] at optical wavelengths, and foreground stars can be confused with background galaxies. However, the effect of extinction drops at longer wavelengths, such as the [[infrared]], and the Milky Way is effectively transparent at radio wavelengths. Surveys in the infrared, such as [[IRAS]] and [[2MASS]], have given a more complete picture of the extragalactic sky. Two very large nearby galaxies, [[Maffei 1]] and [[Maffei 2]], were discovered in the Zone of Avoidance by [[Paolo Maffei]] by their infrared emission in 1968. Even so, approximately 10% of the sky remains difficult to survey as extragalactic objects can be confused with stars in the Milky Way.

Projects to survey the Zone of Avoidance at radio wavelengths, particularly using the [[21 cm line|21&nbsp;cm spin-flip emission line]] of neutral atomic [[hydrogen]] (known in astronomical parlance as [[Hydrogen line|H I line]]), have detected many galaxies that could not be detected in the infrared. Examples of galaxies detected from their HI emission include [[Dwingeloo 1]] and [[Dwingeloo 2]], discovered in 1994 and 1996, respectively.

Recent astronomical studies revealed a supercluster of galaxies, termed the [[Vela Supercluster]], in the [[Great Attractor|Great Attractor's]] theorized location.<ref name="Kraan-Korteweg-2">{{cite Q|Q55892376}}</ref>

==See also==
* [[Extragalactic background light]]
* [[Galactic plane]]
* [[Great Attractor]]

==References==
{{reflist}}

==Sources==
{{wiktionary}}
* {{cite journal |last1=Kraan-Korteweg |first1=Renée C. |last2=Lahav |first2=Ofer |title=The Universe behind the Milky Way |journal=The Astronomy and Astrophysics Review |date=May 24, 2000 |volume=10 |issue=3 |pages=211–261 |arxiv=astro-ph/0005501 |doi=10.1007/s001590000011 |bibcode=2000A&ARv..10..211K |s2cid=14760994}}
* {{cite conference |first1=R. C. |last1=Kraan-Korteweg |first2=L. |last2=Staveley-Smith |first3=J. |last3=Donley |first4=P. A. |last4=Henning |title=The Universe behind the Southern Milky Way |conference=ASP Conference |book-title=Maps of the Cosmos – ASP Conference Series |publisher=[[International Astronomical Union]] |date=November 5, 2003 |arxiv=astro-ph/0311129 |bibcode=2003astro.ph.11129K}}

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