A radio telescope is a specialized antenna and radio receiver used to receive radio waves from astronomical radio sources in the sky. 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 man-made electronic devices.
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.
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or space. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.
Onsala Space Observatory (OSO), the Swedish National Facility for Radio Astronomy, provides scientists with equipment to study the Earth and the rest of the Universe. The observatory operates two radio telescopes in Onsala, 45 km south of Gothenburg, and takes part in several international projects. Examples of activities:
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.
The European VLBI Network (EVN) is a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa and Puerto Rico, which performs very high angular resolution observations of cosmic radio sources using very-long-baseline interferometry (VLBI). The EVN is the most sensitive VLBI array in the world, and the only one capable of real-time observations. The Joint Institute for VLBI ERIC (JIVE) acts as the central organisation in the EVN, providing both scientific user support and a correlator facility. Very Long Baseline Interferometry (VLBI) achieves ultra-high angular resolution and is a multi-disciplinary technique used in astronomy, geodesy and astrometry.
The Mount Pleasant Radio Observatory is a radio astronomy based observatory owned and operated by University of Tasmania, located 20 km east of Hobart in Cambridge, Tasmania. It is home to three radio astronomy antennas and the Grote Reber Museum.
ASTRON is the Netherlands Institute for Radio Astronomy. Its main office is in Dwingeloo in the Dwingelderveld National Park in the province of Drenthe. ASTRON is part of Netherlands Organisation for Scientific Research (NWO).
Haystack Observatory is an astronomical observatory owned by Massachusetts Institute of Technology (MIT). It is located in Westford, Massachusetts (US), approximately 45 kilometers (28 mi) northwest of Boston. Haystack was initially built by MIT's Lincoln Laboratory for the United States Air Force and was known as Haystack Microwave Research Facility. Construction began in 1960, and the antenna began operating in 1964. In 1970 the facility was transferred to MIT, which then formed the Northeast Radio Observatory Corporation (NEROC) with a number of other universities to operate the site as the Haystack Observatory. As of January 2012, a total of nine institutions participated in NEROC.
The Hartebeesthoek Radio Astronomy Observatory (HartRAO) is a radio astronomy observatory, located in a natural bowl of hills at Hartebeesthoek just south of the Magaliesberg mountain range, Gauteng, South Africa, about 50 km west of Johannesburg. It is a National Research Facility run by South Africa's National Research Foundation. HartRAO was the only major radio astronomy observatory in Africa until the construction of the KAT-7 test bed for the future MeerKAT array.
The Dominion Radio Astrophysical Observatory is a research facility founded in 1960 and located at Kaleden, British Columbia, Canada. The site houses four radio telescopes: an interferometric radio telescope, a 26-m single-dish antenna, a solar flux monitor, and the Canadian Hydrogen Intensity Mapping Experiment (CHIME) — as well as support engineering laboratories. The DRAO is operated by the Herzberg Institute of Astrophysics of the National Research Council of the Government of Canada. The observatory was named an IEEE Milestone for first radio astronomical observations using VLBI.
The Institute of Astronomy of Nicolaus Copernicus University in Toruń, known prior to 1 October 2019 in scientific publications as the Toruń Centre for Astronomy, is an optical and radio observatory located at in Piwnice, about 15 km north of Toruń, Poland. It houses two single-dish antenna telescopes, 32 metres and 15 metres in diameter, as well as the largest Polish optical telescope – 90 cm Schmidt-Cassegrain camera. The facility is operated by the Nicolaus Copernicus University. Also, photometry using 60 cm Cassegrain telescope is made and radio measurements of the Sun at 127 MHz frequency have been recorded on a daily basis since 1958 using a 23 m interferometer.
The Metsähovi Radio Observatory is an astronomical observatory in Finland, affiliated with the Aalto University. Its main premises are in Metsähovi, Kirkkonummi, 35 kilometers west of the university's Otaniemi campus.
Spektr-R was a Russian scientific satellite with a 10 m (33 ft) radio telescope on board. It was launched on 18 July 2011, by Zenit-3F launcher, from Baikonur Cosmodrome to perform research on the structure and dynamics of radio sources within and beyond our galaxy. Together with some of the largest ground-based radio telescopes, this telescope formed interferometric baselines extending up to 350,000 km (220,000 mi).
This enclave of scientific research is officially known as Astro Space Center of PN Lebedev Physics Institute, and is under the purview of the Russian Academy of Sciences. Generally speaking, the space center's mission focuses on astrophysics, which includes cosmology. The emphasis is on accomplishing basic research in this science. The research leads into exploring the composition, and structure of astronomical objects, interstellar and interplanetary space along with exploring how these evolved.
The Warkworth 12m Radio Telescope at the Warkworth Radio Astronomical Observatory is operated by the Institute of Radio Astronomy and Space Research of Auckland University of Technology. It was constructed in 2008 and is located just south of Warkworth off SH1 about 50 km north of Auckland, New Zealand.
The Warkworth Radio Astronomical Observatory is located just south of Warkworth, New Zealand, off State Highway 1, about 50 km north of Auckland. It is operated by the Institute for Radio Astronomy and Space Research, Auckland University of Technology. The WARK12M 12m Radio Telescope was constructed in 2008. In 2010, a licence to operate the New Zealand Telecom 30m dish was granted, which led to the construction of the WARK30M 30m Radio Telescope. First observations with the Australian Long Baseline Array took place in 2011.
The Event Horizon Telescope (EHT) is a large telescope array consisting of a global network of radio telescopes. The EHT project combines data from several very-long-baseline interferometry (VLBI) stations around Earth with angular resolution sufficient to observe objects the size of a supermassive black hole's event horizon. The project's observational targets include the two black holes with the largest angular diameter as observed from Earth: the black hole at the center of the supergiant elliptical galaxy Messier 87 (M87), and Sagittarius A* at the center of the Milky Way.
The Korean VLBI Network (KVN) is a radio astronomy observatory located in South Korea. It comprises three 21-meter radio telescopes that function as an interferometer, using the technique of very-long-baseline interferometry (VLBI).
Johann Anton Zensus is a German radio astronomer. He is director at the Max Planck Institute for Radio Astronomy (MPIfR) and honorary professor at the University of Cologne. He is chairman of the collaboration board of the Event Horizon Telescope (EHT). The collaboration announced the first image of a black hole in April 2019.
