Nuller
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196533923
2008-03-07T14:18:24Z
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rewrote links using ref tag and Citation template
A '''nuller''' is a tool used to block out a strong source so that fainter nearby signals can be observed. An example of a nuller is being employed on the [[Keck Interferometer]]. This causes the [[light]] from a [[star]] to destructively [[interference|interfere]], effectively cancelling out the star's [[image]]. The faint light from an [[orbiting]] ring of dust can then be detected. This project is part of a scientific effort to detect and observe nearby [[planet]]s.
==Interferometry==
[[Image:Nulling_Interferance.png|frame|right|Nulling interference pattern, Courtesy NASA/JPL-Caltech]]
Nulling interferometry is a type of [[interferometry]] in which two or more [[Wiktionary:signal|signals]] are mixed to produce observational regions in which the incoming signals cancel themselves out. This creates a set of virtual "blind spots" which prevent unwanted signals from those areas from interfering with weaker nearby signals.
In 1978 Australian-American astronomer [[Ronald N. Bracewell]] suggested using nulling interferometry to search for [[Extrasolar planet | planets around other stars]] <ref>
{{Citation
| last = Bracewell
| first = Ronald N.
| author-link = Ronald N. Bracewell
| publication-date = 1978-08-24
| title = Detecting nonsolar planets by spinning infrared interferometer
| periodical = Nature
| volume = 274
| pages = 780-781
| issn = 0028-0836
| doi = 10.1038/274780a0
}}
</ref><ref>
{{Citation
| last1 = Bracewell
| first1 = Ronald N.
| author1-link = Ronald N. Bracewell
| last2 = MacPhie
| first2 = Robert H.
| publication-date = 1979-04-01
| title = Searching for nonsolar planets
| periodical = Icarus
| volume = 38
| issue = 1
| pages = 136-147
| issn = 0019-1035
| doi = 10.1016/0019-1035(79)90093-9
}}
</ref>. This technique is being considered for use by the [[Terrestrial Planet Finder]], a [[NASA]] mission. Also the [[ESA]] [[Darwin_(ESA)|Darwin]] mission is considering the use of it. It is being used on the [[Keck Interferometer]].
This technique is similar to a [[coronagraph]] but uses multiple sources rather than a physical obstacle to block out the unwanted signals.
==See also==
* [[Coronagraph]]
== References ==
{{reflist}}
==External links==
*[http://www.tno.nl/content.cfm?&context=markten&content=case&laag1=191&item_id=600&Taal=2 Interferometric Nulling at TNO]
*[http://www.daviddarling.info/encyclopedia/N/nulling.html Nulling interferometer basics]
*[http://astro1.panet.utoledo.edu/~ndm/Visuals/baglunchsep03.pdf Tutorial on nulling interferometry]
*[http://planetquest.jpl.nasa.gov/TPF/tpf_book/Chapter_10c.pdf Criteria governing efficacy of nulling interferometry]
*[http://planetquest.jpl.nasa.gov/SIM/Demo/index.cfm Interactive "virtual" interferometer]
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[[Category:Observational astronomy]]
[[Category:Optical devices]]
[[de:Nulling-Interferometer]]