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 The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and, when c ...

. This causes the

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

from a

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

to destructively interfere, effectively cancelling the star's

image An image or picture is a visual representation. An image can be Two-dimensional space, two-dimensional, such as a drawing, painting, or photograph, or Three-dimensional space, three-dimensional, such as a carving or sculpture. Images may be di ...

. As a result, the faint light from a ring of dust

orbiting In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an obje ...

the star can then be detected. This project is part of a scientific effort to detect and observe nearby

planet A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...

Interferometry

''Nulling interferometry'' is a type of

interferometry Interferometry is a technique which uses the ''interference (wave propagation), interference'' of Superposition principle, superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important inves ...

in which two or more

signals A signal is both the process and the result of Signal transmission, transmission of data over some transmission media, media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processin ...

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. This technique was considered for use by both the Terrestrial Planet Finder (a canceled

NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...

mission) and Darwin (a canceled ESA mission). It is being used on the

. A different technique is called a

coronagraph A coronagraph is a telescopic attachment designed to block out the direct light from a star or other bright object so that nearby objects – which otherwise would be hidden in the object's bright glare – can be resolved. Most coronagr ...

, 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. VNC at NASA GSFC

References

{{reflist

External links

Interferometric Nulling at TNOTutorial on nulling interferometryProgress 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
Interactive "virtual" interferometer
Observational astronomy Optical components

Interferometry

Experimental nullers

See also

References

External links