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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 1933, when Karl Jansky at Bell Telephone Laboratories reported 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.
The jansky is a non-SI unit of spectral flux density, or spectral irradiance, used especially in radio astronomy. It is equivalent to 10−26 watts per square metre per hertz.
3C 273 is a quasar located at the center of a giant elliptical galaxy in the constellation of Virgo. It was the first quasar ever to be identified and is the visually brightest quasar in the sky as seen from Earth, with an apparent visual magnitude of 12.9. The derived distance to this object is 749 megaparsecs. The mass of its central supermassive black hole is approximately 886 million times the mass of the Sun.
A BL Lacertae object or BL Lac object is a type of active galactic nucleus (AGN) or a galaxy with such an AGN, named after its prototype, BL Lacertae. In contrast to other types of active galactic nuclei, BL Lacs are characterized by rapid and large-amplitude flux variability and significant optical polarization. Because of these properties, the prototype of the class was originally thought to be a variable star. When compared to the more luminous active nuclei (quasars) with strong emission lines, BL Lac objects have spectra dominated by a relatively featureless non-thermal emission continuum over the entire electromagnetic range. This lack of spectral lines historically hindered identification of the nature and distance of such objects.
The Multi-Element Radio Linked Interferometer Network (MERLIN) is an interferometer array of radio telescopes spread across England. The array is run from Jodrell Bank Observatory in Cheshire by the University of Manchester on behalf of UK Research and Innovation.
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. For example, the Event Horizon Telescope project derived the first image of a black hole using aperture synthesis.
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 Fourth Cambridge Survey (4C) is an astronomical catalogue of celestial radio sources as measured at 178 MHz using the 4C Array. It was published in two parts, in 1965 and 1967, by the Radio Astronomy Group of the University of Cambridge. References to entries in this catalogue use the prefix 4C followed by the declination in degrees, followed by a period, and then followed by the source number on that declination strip, e.g. 4C-06.23.
The 8C Survey (8C) or Rees 38 MHz survey is an astronomical catalogue of celestial radio sources as measured at 38 MHz. It was published in 1990 by the Radio Astronomy Group of the University of Cambridge. Sources are labelled 8C HHMM+DDd where HHMM is the Right Ascension in hours and minutes, and DDd is the Declination in degrees and tenths of a degree, e.g. 8C 0014+861 for a source at Right Ascension 00 14 and 86.1 degrees Declination in 1950 coordinates.
The Mauritius Radio Telescope (MRT) is a synthesis radio telescope in Mauritius that is used to make images of the sky at a frequency of 151.5 MHz. The MRT was primarily designed to make a survey with a point source sensitivity of 150 mJy. Its resolution is about 4 arc min.
The Cambridge Interferometer was a radio telescope interferometer built by Martin Ryle and Antony Hewish in the early 1950s to the west of Cambridge. The interferometer consisted of an array of 4 fixed elements to survey the sky. It produced the two Cambridge catalogues of radio sources, discovering some of the most interesting astronomical objects known. The telescope was operated by the Radio Astronomy Group of Cambridge University.
The source counts distribution of radio-sources from a radio-astronomical survey is the cumulative distribution of the number of sources (N) brighter than a given flux density (S). As it is usually plotted on a log-log scale its distribution is known as the log N – log S plot. It is one of several cosmological tests that were conceived in the 1930s to check the viability of and compare new cosmological models.
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 Ukrainian T-shaped Radio telescope, second modification is the world's largest low-frequency radio telescope at decametre wavelengths. It was completed in 1972 near the village of Hrakovo, 15 km west-south-west from Shevchenkove, Ukraine. The telescope is operated by the Institute of Radio Astronomy of the Ukrainian Academy of Sciences.
The Ohio Sky Survey was an astronomical survey of extragalactic radio sources. Data were taken between 1965 and 1971 using the Big Ear radio telescope at the Ohio State University Radio Observatory (OSURO), also known as the "Big Ear Radio Observatory (BERO)".
3C 286, also known by its position as 1328+307 or 1331+305, is a quasar at redshift 0.8493 with a radial velocity of 164,137 km/s. It is part of the Third Cambridge Catalogue of Radio Sources.
The Unwin Radar is a scientific radar array at Awarua, near Invercargill, New Zealand 46.51°S 168.38°E.
Hercules A is a bright astronomical radio source in the constellation Hercules corresponding to the galaxy 3C 348.
The 40-foot radio telescope at Green Bank Observatory in the U.S. state of West Virginia was constructed in 1961, and started observing a selection of variable radio sources in the same year, completing its observations in 1968. It became the first automated telescope in 1962. It was subsequently used during summer schools, and in 1987 it was repurposed as an educational telescope, as well as continuing to observe radio sources. In 2021 the telescope celebrated its sixtieth anniversary, having been in continuous use since its 1987 restoration, and used by more than 1,500 students.
References
- Shakeshaft, JR; Ryle, M; Baldwin, JE; Elsmore, B; Thomson, JH (1955). "A survey of radio sources between declinations −38° and +83°". Memoirs of the Royal Astronomical Society . 67: 106. Bibcode:1955MmRAS..67..106S.
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