Nuller

A nuller is a tool used to block out a strong source so that fainter signals near the 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 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.

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.[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.

A different technique is called a coronagraph, using a physical obstacle to block out 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.

The Visible Nulling Coronagraph (VNC) experimental breadboard at NASA Goddard Space Flight Center.

See also

References

  1. ↑ Bracewell, Ronald N. (1978), "Detecting nonsolar planets by spinning infrared interferometer", Nature (1978-08-24) 274 (5673): 780–781, Bibcode:1978Natur.274..780B, doi:10.1038/274780a0, ISSN 0028-0836
  2. ↑ Bracewell, Ronald N.; MacPhie, Robert H. (1979), "Searching for nonsolar planets", Icarus (1979-04-01) 38 (1): 136–147, Bibcode:1979Icar...38..136B, doi:10.1016/0019-1035(79)90093-9, ISSN 0019-1035

External links


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