Nuller 3484688 196533923 2008-03-07T14:18:24Z 62.56.86.107 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] {{astronomy-stub}} {{optics-stub}} [[Category:Observational astronomy]] [[Category:Optical devices]] [[de:Nulling-Interferometer]]