Nuller#Interferometry
{{Short description|Scientific Electronic Device}}
A nuller is an optical tool used to block a strong source so that fainter signals near that source can be observed. An example of a nuller is being employed on the Keck Interferometer. This causes the light from a star to destructively interfere, effectively cancelling the star's image. As a result, the faint light from a ring of dust orbiting the star can then be detected. This project is part of a scientific effort to detect and observe nearby planets.
Interferometry
Nulling interferometry is a type of interferometry in which two or more 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 planets around other stars.
{{Citation
| last = Bracewell
| first = Ronald N.
| author-link = Ronald N. Bracewell
| publication-date = 1978-08-24
| title = Detecting nonsolar planets by spinning infrared interferometer
| volume = 274
| pages = 780–781
| issn = 0028-0836
| doi = 10.1038/274780a0
| year = 1978
| journal = Nature
|bibcode = 1978Natur.274..780B
| issue=5673| s2cid = 4210058
}}
{{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
| volume = 38
| issue = 1
| pages = 136–147
| issn = 0019-1035
| doi = 10.1016/0019-1035(79)90093-9
| year = 1979
| journal = Icarus
| bibcode=1979Icar...38..136B
}}
This technique was considered for use by both the Terrestrial Planet Finder (a canceled NASA mission) and Darwin (a canceled ESA mission). It is being used on the Keck Interferometer.
A different technique is called a coronagraph, using a physical obstacle to block the unwanted signals.
Experimental nullers
There has been a nuller built by the Jet Propulsion Laboratory that has flown on a NASA sounding rocket twice, once in 2011 and a second time in 2015. There is also a laboratory nuller at NASA Goddard Space Flight Center known as the Visible Nulling Coronagraph (VNC) that is actively conducting experiments.{{citation needed|date=August 2016}}
See also
References
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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]
- [https://web.archive.org/web/20060905142258/http://astro1.panet.utoledo.edu/%7Endm/Visuals/baglunchsep03.pdf Tutorial on nulling interferometry]
- [https://web.archive.org/web/20030622174600/http://planetquest.jpl.nasa.gov/TPF/tpf_book/Chapter_10c.pdf Progress Toward Astronomical Nulling] (Criteria governing efficacy of nulling interferometry), Chapter 10 of the Terrestrial Planet Finder (TPF): A NASA Origins Program to Search for Habitable Planets - JPL Publication 99-003, May 1999
- [https://web.archive.org/web/20070630043107/http://planetquest.jpl.nasa.gov/SIM/Demo/index.cfm Interactive "virtual" interferometer]