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	'''Radio astronomy''' is the ] through measurement of ] emitted by physical processes occurring in space.		'''Radio astronomy''' is the ] through measurement of ] emitted by physical processes occurring in space.

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	== History ==		== History ==
	===Early work===		===Early work===
	In 1899, the ], developed a ].<ref>Eric Brus, Richard Golob (1990). The Almanac of Science and Technology: What's New and What's Known. 530 pages. Page 52.</ref><ref>Margaret Cheney, Robert Uth, Jim Glenn (1999). Tesla, Master of Lightning. 184 pages. Page 95.</ref> and noted repetitive signals that he deduced must be coming from a non-terrestrial source. A 1996 analysis indicated Tesla was observing ] ] signals.		The history of radio astronomy developed from radio communication research, instead of from following out of conventional astronomical research. <ref>Sir Francis Graham-Smith, Bernard F. Burke, ''An Introduction to Radio Astronomy''. 1997. Page x. </ref> ] developed the parabolic dish that is now used widely in radio astronomy. <ref>Gerrit L. Verschuur, ''Hidden Attraction: The History and Mystery of Magnetism''. 1993. 272 pages. Page 140</ref> In 1894, ] put forth the idea that the Sun radiated radio waves. <ref>Ede, Andrew, and Lesley B. Cormack, ''A History of Science in Society: From Philosophy to Utility''. 2004. Page 351</ref> Lodge was unable to detect the presence of such emission though, due to technical limitations of his apparatus. It would not be until 1945 that the scientific community would come to realize that the Sun indeed emitted radio waves.<ref>] would give a talk on the subject of space radio emission in 1944</ref><ref> Advanced Study Institute on Solar System Radio Astronomy, & Aarons, J. (1965). Solar system radio astronomy; lectures presented at the NATO Advanced Study Institute of the National Observatory of Athens, Cape Sounion, August 2-15, 1964. New York: Distributed by Plenum Press. Page 55</ref> In 1899, the ] developed a ].<ref>Eric Brus, Richard Golob (1990). The Almanac of Science and Technology: What's New and What's Known. 530 pages. Page 52.</ref><ref>Margaret Cheney, Robert Uth, Jim Glenn (1999). Tesla, Master of Lightning. 184 pages. Page 95.</ref>, known as the ], and noted repetitive signals that he deduced must be coming from a non-terrestrial source. A 1996 analysis indicated Tesla was observing ] ] signals.

	===Jansky and Reber===		===Jansky and Reber===
	{{Unreferenced\|date=May 2007}}		{{Unreferenced\|section\|date=May 2007}}
	~~Modern~~ radio astronomy ~~started~~ ~~with~~ a ] ~~discovery~~ by ], an engineer with ], ~~in the early 1930s. Jansky~~ was investigating static that interfered with ] voice transmissions using a turntable mounted 100 ft. by 20 ft. ] working at a ] of 20.5 ] (wavelength about 14.6 meters). By rotating the antenna the direction of a received "static" could be pinpointed. A small shed to the side of the antenna housed an ] pen-and-paper recording system. After sorting out signals from nearby and distant thunderstorms, Jansky continued to investigate a faint steady hiss of unknown origin. Jansky finally determined that the signal repeated on a cycle of 23 hours and 56 minutes. This four-minute lag is typical of an astronomical source "fixed" on the ] rotating in sync with ]. By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the ] and was strongest in the direction of the center the galaxy, in the ] of ].		The developement of radio astronomy began in full in the early 1930s when ], an engineer with ], was investigating static that interfered with ] voice transmissions using a turntable mounted 100 ft. by 20 ft. ] working at a ] of 20.5 ] (wavelength about 14.6 meters). By rotating the antenna the direction of a received "static" could be pinpointed. A small shed to the side of the antenna housed an ] pen-and-paper recording system. After sorting out signals from nearby and distant thunderstorms, Jansky continued to investigate a faint steady hiss of unknown origin. Jansky finally determined that the signal repeated on a cycle of 23 hours and 56 minutes. This four-minute lag is typical of an astronomical source "fixed" on the ] rotating in sync with ]. By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the ] and was strongest in the direction of the center the galaxy, in the ] of ].

	] helped pioneer radio astronomy when he built the first parabolic "dish" radio telescope (9m in diameter) in 1937. He was instrumental in repeating Karl Guthe Jansky's pioneering but somewhat simple work, and went on to conduct the first sky survey in the radio frequencies. On ] ], ], a ] research officer, helped progress radio astronomy further, when he discovered that the sun emitted radio waves. After ], substantial improvements in radio astronomy technology were made by astronomers in Europe, Australia and the United States, and the field of radio astronomy began to blossom.		] helped pioneer radio astronomy when he built the first parabolic "dish" radio telescope (9m in diameter) in 1937. He was instrumental in repeating Karl Guthe Jansky's pioneering but somewhat simple work, and went on to conduct the first sky survey in the radio frequencies. On ] ], ], a ] research officer, helped progress radio astronomy further, when he discovered that the sun emitted radio waves. After ], substantial improvements in radio astronomy technology were made by astronomers in Europe, Australia and the United States, and the field of radio astronomy began to blossom.

	===Modern developments===		===Modern developments===
	Modern developments came in 1946 with the introduction of the technique called ] where many radio telescopes are combined in a large array to achieve much higher ]. ]'s ] obtained a ] for this and later ] work<ref>] 158 pp 339 1946</ref>. The ] interferometer was also developed independently in 1946 by ]'s group at the CSIR, (later ]) in Sydney<ref>] 157 pp 158 1946</ref>. In the early 1950s the ] mapped the radio sky to produce the famous ] and ] surveys of radio sources. Two issues, one astronomical and one technical, dominated the research in Cambridge, from the late 1940's for more than thirty years. What was the nature of the discrete radio sources, or `radio stars'? Where were they, what were they, what were their properties, how many were there, how did they work and what was their significance in the Universe? Of parallel importance was the puzzle of how to devise new kinds of radio telescope which would elucidate these astronomical questions.		Modern developments came in 1946 with the introduction of the technique called ] where many radio telescopes are combined in a large array to achieve much higher ]. The technology progressed when ] inaugurate ]. <ref>Ede, Andrew, and Lesley B. Cormack, ''A History of Science in Society: From Philosophy to Utility''. 2004. Page 352.</ref> Ryle's ] obtained a ] for this and later ] work<ref>] 158 pp 339 1946</ref>. The ] interferometer was also developed independently in 1946 by ]'s group at the CSIR, (later ]) in Sydney<ref>] 157 pp 158 1946</ref>.

			In the early 1950s the ] mapped the radio sky to produce the famous ] and ] surveys of radio sources. Two issues, one astronomical and one technical, dominated the research in Cambridge, from the late 1940's for more than thirty years. What was the nature of the discrete radio sources, or `radio stars'? Where were they, what were they, what were their properties, how many were there, how did they work and what was their significance in the Universe? Of parallel importance was the puzzle of how to devise new kinds of radio telescope which would elucidate these astronomical questions.

			In 1956, the ] was formed to build and operate large radio telescopes.<ref>André Heck, ''Information Handling in Astronomy: Historical Vistas''. 2003. 312 pages. Page 109.</ref> On October 11, ], one of the largest radio telescope of the time went into operation at ] for ].<ref>Herbert Charles Barratt, L. Mary Barker, ''Pears Cyclopaedia''. Pelham Books. Page 9.</ref> By the ], radio astronomy was recognized as a useful field by mainstream science and accompanied optical astronomy in the observation of the phenomenon of the universe.<ref> Frank Durham, Robert D. Purrington ''Frame of the Universe: A History of Physical Cosmology''. Columbia University Press, 1983. 284 pages. Page 218. ISBN 0231053932</ref>

	==See also==		==See also==
	;General: ], ]		;General: ], ]
			;History:]

	== External articles and references ==		== External articles and references ==
	===Citations and notes===		===Citations and notes===
			<div style="font-size:87.5%; -moz-column-count:2; column-count:2;">
	<references />		<references />
			</div>

	===Further reading===		===Further reading===
			===Journals===
			<div style="font-size:87.5%; -moz-column-count:2; column-count:2;">
			* Hendrik Christoffel van de Hulst, ''The Origin of Radio Waves From Space''.
			* Karl G. Jansky, ''Directional studies of atmospherics at high frequencies''. Proc. IRE 20 (1932) 1920
			* Karl G. Jansky, ''Radio waves from outside the solar system''. Nature 132 (1933) 6
			* Karl G. Jansky, ''Electrical disturbances apparently of extraterrestrial origin''. Proc. IRE 21 (1933) 1387.
			* Karl G. Jansky, '' "Electrical phenomena that apparently are of interstellar origin". Popular Astronomy 41 (1933) 548.
			* G. Westerhout, ''The early history of radio astronomy''. Ann. New York Acad. Sci. 189 (1972) 211-218
	* ''History of High-Resolution Radio Astronomy''. Annual Review of Astronomy and Astrophysics, September 2001		* ''History of High-Resolution Radio Astronomy''. Annual Review of Astronomy and Astrophysics, September 2001
			</div>

			===Books===
			<div style="font-size:87.5%; -moz-column-count:2; column-count:2;">
			* Woodruff T. Sullivan, III, ''The early years of radio astronomy''. 1984.
			* Woodruff T. Sullivan, III, ''Classics in Radio Astronomy''. Reidel Publishing Company, Dordrecht, 1982.
			* Kristen Rohlfs, Thomas L Wilson, ''Tools of Radio Astronomy''. Springer 2003. 461 pages. ISBN 3540403876
			* Raymond Haynes, Roslynn Haynes, and Richard McGee, ''Explorers of the Southern Sky: A History of Australian Astronomy''. Cambridge University Press 1996. 541 pages. ISBN 0521365759
			* Shigeru Nakayama, ''A Social History of Science and Technology in Contemporary Japan: Transformation Period 1970-1979''. Trans Pacific Press 2006. 580 pages. ISBN 1876843462
			* David L. Jauncey, ''Radio Astronomy and Cosmology''. Springer 1977. 420 pages. ISBN 9027708398
			* Allan A. Needell, ''Science, Cold War and American State: Lloyd V. Berkner and the Balance of Professional Ideals''. Routledge 2000. ISBN 905702621X (ed., see Chapter 10, Expanding Federal Support of Private Research: The Case of Radio Astronomy (Pages 259 - 596))
			* Bruno Bertotti, ''Modern Cosmology in Retrospect''. Cambridge University Press 1990. 446 pages. ISBN 0521372135 (ed., see essays by Robert Wilson, ''Discovery of the cosmic microwave background'' and Woodruff T. Sullivan, III, ''The entry of radio astronomy into cosmology: radio stars and 309 Martin Ryle's 2C survey''.))
			* J. S. Hey, ''The Evolution of Radio Astronomy''. Neale Watson Academic, 1973.
			* D. T. Wilkinson and P. J. E. Peebles, ''Serendipitous Discoveries in Radio Astronomy''. National Radio Astronomy Observatory, Green Bank, WV, 1983.
			*Joseph Lade Pawsey and Ronald Newbold Bracewell, ''Radio Astronomy''. Clarendon Press, 1955. 361 pages.
			*J. C.Kapteyn, P. C. v. d. Kruit, & K. v. Berkel,'' The legacy of J.C. Kapteyn: studies on Kapteyn and the development of modern astronomy''. Astrophysics and space science library, v. 246. Dordrecht: Kluwer Academic Publishers 2000.
			* Roger Clifton Jennison, ''Introduction to Radio Astronomy''. 1967. 160 pages.
			* Robin Michael Green, ''Spherical Astronomy''. Cambridge University Press 1985. 546 pages. ISBN 0521317797
			</div>

	===Websites===		===Websites===
	;French ~~Hisory~~		;French History
	* - a history of ] radio astronomy		* - a history of ] radio astronomy

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	* - National Park Services		* - National Park Services
	* - a brief history from ] ]		* - a brief history from ] ]

			; Other history
			*Tesla, Nikola, "''''". Collier's Weekly, February 19, 1901. (EarlyRadioHistory.us)
			*Corum, K. L., J. F. Corum, "''''

Revision as of 16:45, 19 May 2007

Radio astronomy is the study of celestial phenomena through measurement of radio waves emitted by physical processes occurring in space.

Description

Radio waves have a much greater wavelength than light waves. In order to receive signals with large signal-to-noise ratio, radio astronomy requires a large antenna or an array of smaller antennas working together (for example, the Very Large Array). Some of these radio telescopes use a parabolic dish to reflect the waves to a receiver which detects and amplifies the signal into usable data. This allows astronomers to see a region of the radio sky. If they take multiple scans of overlapping strips of the sky they can piece together an image ('mosaicing'). Radio astronomy is a relatively new field of astronomical research that still has much more to be discovered.

Astronomical sources

Radio astronomy has led to substantial increases in astronomical knowledge, particularly with the discovery of several classes of new objects, including pulsars, quasars and radio galaxies. This is because radio astronomy allows us to see things that are not detectable in optical astronomy. Such objects represent some of the most extreme and energetic physical processes in the universe.

Radio astronomy is also partly responsible for the idea that dark matter is an important component of our universe; radio measurements of the rotation of galaxies suggest that there is much more mass in galaxies than has been directly observed (see Vera Rubin). The cosmic microwave background radiation was also first detected using radio telescopes. However, radio telescopes have also been used to investigate objects much closer to home, including observations of the Sun and solar activity, and radar mapping of the planets.

Other sources include:

Active galactic nuclei and pulsars have jets of charged particles which emit synchrotron radiation
Merging galaxy clusters often show diffuse radio emission
Supernova remnants can also show diffuse radio emission
The Cosmic microwave background is blackbody radio emission

Observational techniques

Radio telescopes can now be found all over the world (see List of radio telescopes). Most are designed for microwave radiation. Widely separated telescopes are often combined using a technique called interferometry in order to obtain observations with much higher resolution than could be obtained using a single receiver. Initially telescopes within a few kilometers of each other were combined (see, for example, the Mullard Radio Astronomy Observatory), but since the 1970s telescopes from all over the world (and even in Earth orbit) have been combined to perform Very Long Baseline Interferometry.

The United States government has established an institution to conduct radio astronomy research in the US, titled the National Radio Astronomy Observatory (commonly abbreviated as NRAO). This institution controls various radio telescopes around the United States included the world's largest fully mobile radio telescope, the Green Bank Telescope. The United States government has also set aside a national radio quiet zone for radio astronomy research centered around Green Bank, West Virginia. As a result, Green Bank is now the home of NRAO's primary facility.

History

Early work

The history of radio astronomy developed from radio communication research, instead of from following out of conventional astronomical research. Heinrich Hertz developed the parabolic dish that is now used widely in radio astronomy. In 1894, Oliver Lodge put forth the idea that the Sun radiated radio waves. Lodge was unable to detect the presence of such emission though, due to technical limitations of his apparatus. It would not be until 1945 that the scientific community would come to realize that the Sun indeed emitted radio waves. In 1899, the Nikola Tesla developed a radio telescope., known as the Teslascope, and noted repetitive signals that he deduced must be coming from a non-terrestrial source. A 1996 analysis indicated Tesla was observing Jovian plasma torus signals.

Jansky and Reber

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The developement of radio astronomy began in full in the early 1930s when Karl Guthe Jansky, an engineer with Bell Telephone Laboratories, was investigating static that interfered with short wave voice transmissions using a turntable mounted 100 ft. by 20 ft. directional antenna working at a frequency of 20.5 MHz (wavelength about 14.6 meters). By rotating the antenna the direction of a received "static" could be pinpointed. A small shed to the side of the antenna housed an analog pen-and-paper recording system. After sorting out signals from nearby and distant thunderstorms, Jansky continued to investigate a faint steady hiss of unknown origin. Jansky finally determined that the signal repeated on a cycle of 23 hours and 56 minutes. This four-minute lag is typical of an astronomical source "fixed" on the celestial sphere rotating in sync with sidereal time. By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the Milky Way and was strongest in the direction of the center the galaxy, in the constellation of Sagittarius.

Grote Reber helped pioneer radio astronomy when he built the first parabolic "dish" radio telescope (9m in diameter) in 1937. He was instrumental in repeating Karl Guthe Jansky's pioneering but somewhat simple work, and went on to conduct the first sky survey in the radio frequencies. On February 27 1942, J.S. Hey, a British Army research officer, helped progress radio astronomy further, when he discovered that the sun emitted radio waves. After World War II, substantial improvements in radio astronomy technology were made by astronomers in Europe, Australia and the United States, and the field of radio astronomy began to blossom.

Modern developments

Modern developments came in 1946 with the introduction of the technique called astronomical interferometry where many radio telescopes are combined in a large array to achieve much higher resolutions. The technology progressed when Martin Ryle inaugurate radio interferometer. Ryle's group in Cambridge obtained a Nobel Prize for this and later aperture synthesis work. The Lloyd's mirror interferometer was also developed independently in 1946 by Joseph Pawsey's group at the CSIR, (later CSIRO) in Sydney.

In the early 1950s the Cambridge Interferometer mapped the radio sky to produce the famous 2C and 3C surveys of radio sources. Two issues, one astronomical and one technical, dominated the research in Cambridge, from the late 1940's for more than thirty years. What was the nature of the discrete radio sources, or `radio stars'? Where were they, what were they, what were their properties, how many were there, how did they work and what was their significance in the Universe? Of parallel importance was the puzzle of how to devise new kinds of radio telescope which would elucidate these astronomical questions.

In 1956, the National Radio Astronomy Observatory was formed to build and operate large radio telescopes. On October 11, 1957, one of the largest radio telescope of the time went into operation at Jodrell Bank for Manchester University. By the 1960s, radio astronomy was recognized as a useful field by mainstream science and accompanied optical astronomy in the observation of the phenomenon of the universe.

External articles and references

Citations and notes

Sir Francis Graham-Smith, Bernard F. Burke, An Introduction to Radio Astronomy. 1997. Page x.
Gerrit L. Verschuur, Hidden Attraction: The History and Mystery of Magnetism. 1993. 272 pages. Page 140
Ede, Andrew, and Lesley B. Cormack, A History of Science in Society: From Philosophy to Utility. 2004. Page 351
Hendrik Christoffel van de Hulst would give a talk on the subject of space radio emission in 1944
Advanced Study Institute on Solar System Radio Astronomy, & Aarons, J. (1965). Solar system radio astronomy; lectures presented at the NATO Advanced Study Institute of the National Observatory of Athens, Cape Sounion, August 2-15, 1964. New York: Distributed by Plenum Press. Page 55
Eric Brus, Richard Golob (1990). The Almanac of Science and Technology: What's New and What's Known. 530 pages. Page 52.
Margaret Cheney, Robert Uth, Jim Glenn (1999). Tesla, Master of Lightning. 184 pages. Page 95.
Ede, Andrew, and Lesley B. Cormack, A History of Science in Society: From Philosophy to Utility. 2004. Page 352.
Nature 158 pp 339 1946
Nature 157 pp 158 1946
André Heck, Information Handling in Astronomy: Historical Vistas. 2003. 312 pages. Page 109.
Herbert Charles Barratt, L. Mary Barker, Pears Cyclopaedia. Pelham Books. Page 9.
Frank Durham, Robert D. Purrington Frame of the Universe: A History of Physical Cosmology. Columbia University Press, 1983. 284 pages. Page 218. ISBN 0231053932

Journals

Hendrik Christoffel van de Hulst, The Origin of Radio Waves From Space.
Karl G. Jansky, Directional studies of atmospherics at high frequencies. Proc. IRE 20 (1932) 1920
Karl G. Jansky, Radio waves from outside the solar system. Nature 132 (1933) 6
Karl G. Jansky, Electrical disturbances apparently of extraterrestrial origin. Proc. IRE 21 (1933) 1387.
Karl G. Jansky, "Electrical phenomena that apparently are of interstellar origin". Popular Astronomy 41 (1933) 548.
G. Westerhout, The early history of radio astronomy. Ann. New York Acad. Sci. 189 (1972) 211-218
History of High-Resolution Radio Astronomy. Annual Review of Astronomy and Astrophysics, September 2001

Books

Woodruff T. Sullivan, III, The early years of radio astronomy. 1984.
Woodruff T. Sullivan, III, Classics in Radio Astronomy. Reidel Publishing Company, Dordrecht, 1982.
Kristen Rohlfs, Thomas L Wilson, Tools of Radio Astronomy. Springer 2003. 461 pages. ISBN 3540403876
Raymond Haynes, Roslynn Haynes, and Richard McGee, Explorers of the Southern Sky: A History of Australian Astronomy. Cambridge University Press 1996. 541 pages. ISBN 0521365759
Shigeru Nakayama, A Social History of Science and Technology in Contemporary Japan: Transformation Period 1970-1979. Trans Pacific Press 2006. 580 pages. ISBN 1876843462
David L. Jauncey, Radio Astronomy and Cosmology. Springer 1977. 420 pages. ISBN 9027708398
Allan A. Needell, Science, Cold War and American State: Lloyd V. Berkner and the Balance of Professional Ideals. Routledge 2000. ISBN 905702621X (ed., see Chapter 10, Expanding Federal Support of Private Research: The Case of Radio Astronomy (Pages 259 - 596))
Bruno Bertotti, Modern Cosmology in Retrospect. Cambridge University Press 1990. 446 pages. ISBN 0521372135 (ed., see essays by Robert Wilson, Discovery of the cosmic microwave background and Woodruff T. Sullivan, III, The entry of radio astronomy into cosmology: radio stars and 309 Martin Ryle's 2C survey.))
J. S. Hey, The Evolution of Radio Astronomy. Neale Watson Academic, 1973.
D. T. Wilkinson and P. J. E. Peebles, Serendipitous Discoveries in Radio Astronomy. National Radio Astronomy Observatory, Green Bank, WV, 1983.
Joseph Lade Pawsey and Ronald Newbold Bracewell, Radio Astronomy. Clarendon Press, 1955. 361 pages.
J. C.Kapteyn, P. C. v. d. Kruit, & K. v. Berkel, The legacy of J.C. Kapteyn: studies on Kapteyn and the development of modern astronomy. Astrophysics and space science library, v. 246. Dordrecht: Kluwer Academic Publishers 2000.
Roger Clifton Jennison, Introduction to Radio Astronomy. 1967. 160 pages.
Robin Michael Green, Spherical Astronomy. Cambridge University Press 1985. 546 pages. ISBN 0521317797

Websites

French History

The History of the Nancay Radio Observatory - a history of French radio astronomy

History (America, Post 1930s)

History of Radio Astronomy, National Radio Astronomy Observatory
The History of Radio Astronomy - Haystack Observatory, MIT
Hanes, Dave, "Physics 014: The Course Notes, Radio Astronomy". Astronomy Group and Department of Physics, Queen's University. 2000-2001.
Reber Radio Telescope - National Park Services
Radio Telescope Developed - a brief history from NASA Goddard Space Flight Center

Other history

Tesla, Nikola, "Talking with Planets". Collier's Weekly, February 19, 1901. (EarlyRadioHistory.us)
Corum, K. L., J. F. Corum, "Nikola Tesla and the Planetary Radio Signals

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