Cambridge Interferometer

Cambridge Interferometer
Location(s)	United Kingdom
Coordinates	52°13′N0°06′E / 52.21°N 0.1°E Coordinates: 52°13′N0°06′E / 52.21°N 0.1°E
Organization	University of Cambridge
Wavelength	81.5, 159 MHz (3.68, 1.89 m)
Telescope style	radio interferometer
	Location of Cambridge Interferometer
	[ edit on Wikidata]

Last updated March 17, 2019

The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge (between the Grange Road football ground and the current Cavendish Laboratory). The interferometer consisted of an array of 4 fixed elements to survey the sky. It produced the two Cambridge catalogues of radio sources (the 2C catalogue of radio sources at 81.5 MHz, and the 3C catalogue of radio sources at 159 MHz, building on the work of the Preliminary survey of the radio stars in the Northern Hemisphere at 45 MHz - 214 MHz using the 2-element Long Michelson Interferometer), discovering some of the most interesting astronomical objects known. The telescope was operated by the Radio Astronomy Group of Cambridge University.

A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky in radio astronomy. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency portion of the electromagnetic spectrum emitted by astronomical objects, just as optical telescopes are the main observing instrument used in traditional optical astronomy which studies the light wave portion of the spectrum coming from astronomical objects. Radio telescopes are typically large parabolic ("dish") antennas similar to those employed in tracking and communicating with satellites and space probes. They may be used singly or linked together electronically in an array. Unlike optical telescopes, radio telescopes can be used in the daytime as well as at night. Since astronomical radio sources such as planets, stars, nebulas and galaxies are very far away, the radio waves coming from them are extremely weak, so radio telescopes require very large antennas to collect enough radio energy to study them, and extremely sensitive receiving equipment. Radio observatories are preferentially located far from major centers of population to avoid electromagnetic interference (EMI) from radio, television, radar, motor vehicles, and other manmade electronic devices.

An astronomical interferometer is an array of separate telescopes, mirror segments, or radio telescope antennas that work together as a single telescope to provide higher resolution images of astronomical objects such as stars, nebulas and galaxies by means of interferometry. The advantage of this technique is that it can theoretically produce images with the angular resolution of a huge telescope with an aperture equal to the separation between the component telescopes. The main drawback is that it does not collect as much light as the complete instrument's mirror. Thus it is mainly useful for fine resolution of more luminous astronomical objects, such as close binary stars. Another drawback is that the maximum angular size of a detectable emission source is limited by the minimum gap between detectors in the collector array.

Sir Martin Ryle was an English radio astronomer who developed revolutionary radio telescope systems and used them for accurate location and imaging of weak radio sources. In 1946 Ryle and Derek Vonberg were the first people to publish interferometric astronomical measurements at radio wavelengths. With improved equipment, Ryle observed the most distant known galaxies in the universe at that time. He was the first Professor of Radio Astronomy at the University of Cambridge, and founding director of the Mullard Radio Astronomy Observatory. He was Astronomer Royal from 1972 to 1982. Ryle and Antony Hewish shared the Nobel Prize for Physics in 1974, the first Nobel prize awarded in recognition of astronomical research. In the 1970s, Ryle turned the greater part of his attention from astronomy to social and political issues which he considered to be more urgent.

Martin Ryle and Antony Hewish received the Nobel Prize for Physics in 1974 for this and other related work.

Antony Hewish is a British radio astronomer who won the Nobel Prize for Physics in 1974 for his role in the discovery of pulsars. He was also awarded the Eddington Medal of the Royal Astronomical Society in 1969.

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Radio astronomy subfield of astronomy that studies celestial objects at radio frequencies

Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1932, when Karl Jansky at Bell Telephone Laboratories observed radiation coming from the Milky Way. Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies, as well as entirely new classes of objects, such as radio galaxies, quasars, pulsars, and masers. The discovery of the cosmic microwave background radiation, regarded as evidence for the Big Bang theory, was made through radio astronomy.

Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and orientation, the lobe-pattern of the interferometer produces an output which is one component of the Fourier transform of the spatial distribution of the brightness of the observed object. The image of the source is produced from these measurements. Astronomical interferometers are commonly used for high-resolution optical, infrared, submillimetre and radio astronomy observations.

PSR B1919+21 is a pulsar with a period of 1.3373 seconds and a pulse width of 0.04 seconds. Discovered by Jocelyn Bell Burnell and Antony Hewish on November 28, 1967, it is the first discovered radio pulsar. The power and regularity of the signals were briefly thought to resemble an extraterrestrial beacon, leading the source to be nicknamed LGM-1.

The Third Cambridge Catalogue of Radio Sources (3C) is an astronomical catalogue of celestial radio sources detected originally at 159 MHz, and subsequently at 178 MHz.

The Cavendish Astrophysics Group is based at the Cavendish Laboratory at the University of Cambridge. The group operates all of the telescopes at the Mullard Radio Astronomy Observatory except for the 32m MERLIN telescope, which is operated by Jodrell Bank.

The Ryle Telescope was a linear east-west radio telescope array at the Mullard Radio Astronomy Observatory. In 2004, three of the telescopes were moved to create a compact two-dimensional array of telescopes at the east end of the interferometer. The remaining five antennas were switched off on 19 June 2006. The eight antennas have now become the Arcminute Microkelvin Imager Large Array.

The One-Mile Telescope at the Mullard Radio Astronomy Observatory (MRAO), Cambridge, UK is an array of radio telescopes designed to perform aperture synthesis interferometry.

The Westerbork Synthesis Radio Telescope (WSRT) is an aperture synthesis interferometer near World War II Nazi detention and transit camp Westerbork, north of the village of Westerbork, Midden-Drenthe, in the northeastern Netherlands. It consists of a linear array of 14 antennas with a diameter of 25 metres arranged on a 2.7 km East-West line. It has a similar arrangement to other radio telescopes such as the One-Mile Telescope, Australia Telescope Compact Array and the Ryle Telescope. Its Equatorial mount is what sets it apart from most other radio telescopes, most of which have an Altazimuth mount. This makes it specifically useful for specific types of science, like polarized emission research as the detectors maintain a constant orientation on the sky during an observation. Ten of the telescopes are on fixed mountings while the remaining four dishes are movable along two rail tracks. The telescope was completed in 1970 and underwent a major upgrade between 1995-2000.

The 5C Survey of Radio Sources (5C) is an astronomical catalogue of celestial radio sources as measured at 408 MHz and 1407 MHz. It was published in a number of parts between 1975 and 1995 by the Radio Astronomy Group of the University of Cambridge. The One-Mile Telescope used to produce this catalogue had an angular resolutions of 80 arcseconds and 23 arcseconds at 408 MHz and 1407 MHz respectively, and catalogued radio sources as faint as 2 milli-Janskys, considerably fainter than any previously catalogued radio source.

The 9C survey at 15 GHz (9C) is an astronomical catalogue generated from the radio observations of the Ninth Cambridge survey at 15 GHz. It was published in 2003 by the Cavendish Astrophysics Group of the University of Cambridge. The catalogue was originally made in order to locate radio sources which were interfering with observations using the Very Small Array, but the catalogue has also proved useful for other astronomical programs.

The Cambridge Low-Frequency Synthesis Telescope (CLFST) is an east-west aperture synthesis radio telescope currently operating at 151 MHz. It consists of 60 tracking yagis on a 4.6 km baseline, giving 776 simultaneous baselines. These provide a resolution of 70×70 cosec(declination) arcsec², with a sensitivity of about 30 to 50 mJy/beam, and a field of view of about 9°×9°. The telescope is situated at the Mullard Radio Astronomy Observatory.

The 6C Survey of Radio Sources (6C) is an astronomical catalogue of celestial radio sources as measured at 151-MHz. It was published between 1985 and 1993 by the Radio Astronomy Group of the University of Cambridge.

The Interplanetary Scintillation Array is a radio telescope that was built in 1967 at the Mullard Radio Astronomy Observatory, in Cambridge, United Kingdom, and was operated by the Cavendish Astrophysics Group. The instrument originally covered 4 acres. It was enlarged to 9 acres in 1978, and was re-furbished in 1989.

The Second Cambridge Catalogue of Radio Sources (2C) was published in 1955 by John R Shakeshaft and colleagues. It comprised a list of 1936 sources between declinations -38 and +83, giving their right ascension, declination, both in 1950.0 coordinates, and flux density. The observations were made with the Cambridge Interferometer, at 81.5 MHz.

The First Cambridge Catalogue of Radio Sources (1C) refers to the catalogue listed in the article Ryle M, Smith F G & Elsmore B (1950) MNRAS vol 110 pp508-523 "A Preliminary Survey of Radio Stars in the Northern Hemisphere".

The Long Michelson Interferometer was a radio telescope interferometer built by Martin Ryle and co-workers in the late 1940s beside the rifle range to the west of Cambridge, England. The interferometer consisted of 2 fixed elements 440m apart to survey the sky using Earth rotation. It produced the Preliminary survey of the radio stars in the Northern Hemisphere at 45 MHz - 214 MHz. The telescope was operated by the Radio Astronomy Group of Cambridge University.

John Ashworth Ratcliffe CB OBE FRS, "JAR" or "Jack", was an influential British radio physicist.

References

Ryle M, Hewish A. 1955. Mem. R. Astron. Soc. 67:97-105

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