Nuller

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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 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 planets.

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[edit] Interferometry

Nulling interference pattern, Courtesy NASA/JPL-Caltech
Nulling interference pattern, Courtesy NASA/JPL-Caltech

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 [1][2]. This technique is being considered for use by the Terrestrial Planet Finder, a NASA mission. Also the 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.

[edit] See also

[edit] References

  1. ^ Bracewell, Ronald N. (1978-08-24), “Detecting nonsolar planets by spinning infrared interferometer”, Nature 274: 780-781, ISSN 0028-0836, DOI 10.1038/274780a0 
  2. ^ Bracewell, Ronald N. & MacPhie, Robert H. (1979-04-01), “Searching for nonsolar planets”, Icarus 38 (1): 136-147, ISSN 0019-1035, DOI 10.1016/0019-1035(79)90093-9 

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