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Karl Guthe Jansky (October 22, 1905 – February 14, 1950) was an American
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate caus ...
and radio engineer who in April 1933 first announced his discovery of
radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shor ...
s emanating from the
Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
in the constellation Sagittarius. He is considered one of the founding figures of
radio astronomy 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 ...
.


Early life

Karl Guthe Jansky was born 1905 in what was then the Territory of Oklahoma where his father, Cyril M. Jansky, was Dean of the College of Engineering at the
University of Oklahoma , mottoeng = "For the benefit of the Citizen and the State" , type = Public research university , established = , academic_affiliations = , endowment = $2.7billion (2021) , p ...
at Norman. Cyril M. Jansky, born in Wisconsin of Czech immigrants, had started teaching at the age of sixteen. He was a teacher throughout his active life, retiring as Professor of Electrical Engineering at the University of Wisconsin. He was an engineer with a strong interest in physics, a trait passed on to his sons. Karl Jansky was named after Dr. Karl Eugen Guthe, a Professor of Physics at the University of Michigan who had been an important mentor to Cyril M. Jansky. Karl Jansky's mother, born Nellie Moreau, was of French and English descent. Karl's brother Cyril Jansky Jr., who was ten years older, helped build some of the earliest radio transmitters in the country, including 9XM in
Wisconsin Wisconsin () is a state in the upper Midwestern United States. Wisconsin is the 25th-largest state by total area and the 20th-most populous. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michi ...
(now WHA of
Wisconsin Public Radio Wisconsin Public Radio (WPR) is a network of 34 public radio stations in the state of Wisconsin. WPR's network is divided into two distinct analog services, the ''Ideas Network'' and the ''NPR News & Music Network,'' as well as the ''All Classica ...
) and 9XI in
Minnesota Minnesota () is a state in the upper midwestern region of the United States. It is the 12th largest U.S. state in area and the 22nd most populous, with over 5.75 million residents. Minnesota is home to western prairies, now given over to ...
(now KUOM). Karl Jansky attended college at the
University of Wisconsin A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, t ...
where he received his BS in
physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which re ...
in 1927. He stayed an extra year at Madison, completing all the graduate course work for a Masters degree in physics except for the thesis. In July 1928 at age 22, he was able to join the
Bell Telephone Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...
, and because of a kidney condition he had since college (which eventually led to his early death), he was sent to the healthier environs of the field station in
Holmdel, New Jersey Holmdel Township (usually shortened to Holmdel) is a township in Monmouth County, New Jersey, United States. The township is centrally located in the Raritan Valley region, being within the regional and cultural influence of the Raritan Bays ...
.Serendipitous Discoveries in Radio Astronomy: Proceedings of a Workshop held at the National Radio Astronomy Observatory, Green Bank, West Virginia on May 4, 5, 6, 1983; Honoring the 50th Anniversary Announcing the Discovery of Cosmic Radio Waves by Karl G. Jansky on May 5, 1933.
Edited by K. Kellermann and B. Sheets (1983) 321pp
Bell Labs wanted to investigate
atmospheric An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...
and
ionospheric The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an im ...
properties using "
short wave Shortwave radio is radio transmission using shortwave (SW) radio frequencies. There is no official definition of the band, but the range always includes all of the high frequency band (HF), which extends from 3 to 30 MHz (100 to 10 me ...
s" (
wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tr ...
s of about 10–20 meters) for use in trans-Atlantic
radio telephone Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmit ...
service. As a radio engineer, Jansky was assigned the job of investigating sources of
static Static may refer to: Places *Static Nunatak, a nunatak in Antarctica United States * Static, Kentucky and Tennessee * Static Peak, a mountain in Wyoming ** Static Peak Divide, a mountain pass near the peak Science and technology Physics *Static ...
that might interfere with radio voice transmissions.


Radio astronomy

At Bell Telephone Laboratories, Jansky built a
directional antenna A directional antenna or beam antenna is an antenna which radiates or receives greater power in specific directions allowing increased performance and reduced interference from unwanted sources. Directional antennas provide increased performan ...
designed to receive radio waves at a
frequency Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is e ...
of 20.5 MHz (wavelength about 14.6 meters). It had a diameter of approximately 100 ft. (30 meter) and stood 20 ft. (6 meter) tall. It was mounted on top of a turntable on a set of four Ford Model-T wheels, which allowed it to be rotated in the azimuthal direction, earning it the nickname "''Jansky's merry-go-round''" (the cost of which was later estimated to be less than $1000). By rotating the antenna, the direction of a received signal could be pinpointed. The intensity of the signal was recorded by an analog pen-and-paper recording system housed in a small shed to the side of the antenna. After recording signals from all directions for several months, Jansky eventually categorized them into three types of static: nearby thunderstorms, distant thunderstorms, and a faint static or "hiss" of unknown origin. He spent over a year investigating the source of the third type of static. The location of maximum intensity rose and fell once a day, leading Jansky to initially surmise that he was detecting radiation from the Sun. After a few months of following the signal, however, the point of maximum static moved away from the position of the Sun. Jansky also determined that the signal repeated on a cycle of 23 hours and 56 minutes. Jansky discussed the puzzling phenomena with his friend, astrophysicist Albert Melvin Skellett, who pointed out that the observed time between the signal peaks was the exact length of a
sidereal day Sidereal time (as a unit also sidereal day or sidereal rotation period) (sidereal ) is a timekeeping system that astronomers use to locate celestial objects. Using sidereal time, it is possible to easily point a telescope to the proper coo ...
; the time it took for "fixed" astronomical objects, such as a star, to pass in front of the antenna every time the Earth rotated. By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the
Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye ...
and was strongest (7:10 p.m. on September 16, 1932) in the direction of the center of the galaxy, in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the earliest constellation ...
of Sagittarius. Jansky announced his discovery at a meeting in Washington D.C. in April 1933 to a small audience who could not comprehend its significance. His discovery was widely publicized, appearing in the ''
New York Times ''The New York Times'' (''the Times'', ''NYT'', or the Gray Lady) is a daily newspaper based in New York City with a worldwide readership reported in 2020 to comprise a declining 840,000 paid print subscribers, and a growing 6 million paid ...
'' of May 5, 1933, and he was interviewed on a special NBC program on "Radio sounds from among the stars". In October 1933, his discovery was published in a journal article entitled "Electrical disturbances apparently of extraterrestrial origin" in the '' Proceedings of the Institute of Radio Engineers''. If the radio sources were from the stars, the Sun should also be producing radio noise, but Jansky found that it did not. In the early 1930s, the Sun was at an inactive phase in its sunspot cycle. In 1935 Jansky made the suggestion that the strange radio signals may be produced from interstellar gas, in particular, by "thermal agitation of charged particles." Jansky accomplished these investigations while still in his twenties with a bachelor's degree in physics. Jansky wanted to further investigate the Milky Way radio waves after 1935 (he called the radiation "Star Noise" in the thesis he submitted to earn his 1936 University of Wisconsin Masters degree), but he found little support from either astronomers, for whom it was completely foreign, or Bell Labs, which could not justify, during the depression, the cost of research on a phenomenon that did not significantly affect trans-Atlantic communications systems.


Follow-up

Several scientists were interested in Jansky's discovery, but radio astronomy remained a dormant field for several years, due in part to Jansky's lack of formal training as an astronomer. His discovery had come in the midst of the
Great Depression The Great Depression (19291939) was an economic shock that impacted most countries across the world. It was a period of economic depression that became evident after a major fall in stock prices in the United States. The Financial contagion, ...
, and observatories were wary of taking on any new and potentially risky projects. Two men who learned of Jansky's 1933 discovery were of great influence on the later development of the new study of radio astronomy: one was
Grote Reber Grote Reber (December 22, 1911 – December 20, 2002) was an American pioneer of radio astronomy, which combined his interests in amateur radio and amateur astronomy. He was instrumental in investigating and extending Karl Jansky's pioneering wo ...
, a radio engineer who singlehandedly built a
radio telescope A radio telescope is a specialized antenna and radio receiver used to detect 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 ...
in his
Illinois Illinois ( ) is a state in the Midwestern United States. Its largest metropolitan areas include the Chicago metropolitan area, and the Metro East section, of Greater St. Louis. Other smaller metropolitan areas include, Peoria and Rockf ...
back yard in 1937 and did the first systematic survey of astronomical radio waves. The second was John D. Kraus, who, after World War II, started a radio observatory at
Ohio State University The Ohio State University, commonly called Ohio State or OSU, is a public land-grant research university in Columbus, Ohio. A member of the University System of Ohio, it has been ranked by major institutional rankings among the best publi ...
and wrote a textbook on radio astronomy, long considered a standard by radio astronomers.


Death and legacy

Jansky was a resident of Little Silver, New Jersey, and died at age 44 in a
Red Bank, New Jersey Red Bank is a borough in Monmouth County, New Jersey, United States. Incorporated in 1908, the community is on the Navesink River, the area's original transportation route to the ocean and other ports. Red Bank is in the New York Metropolitan ...
, hospital (now called Riverview Medical Center) due to a heart condition. In honor of Jansky, the unit used by radio astronomers for the
spectral irradiance In radiometry, irradiance is the radiant flux ''received'' by a ''surface'' per unit area. The SI unit of irradiance is the watt per square metre (W⋅m−2). The CGS unit erg per square centimetre per second (erg⋅cm−2⋅s−1) is often used ...
of radio sources is the
jansky The jansky (symbol Jy, plural ''janskys'') 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. The ''flux density'' or ''mono ...
(1 Jy = 10−26 W⋅m−2⋅Hz−1). The crater
Jansky The jansky (symbol Jy, plural ''janskys'') 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. The ''flux density'' or ''mono ...
on the
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
is also named after him. The
National Radio Astronomy Observatory The National Radio Astronomy Observatory (NRAO) is a federally funded research and development center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc. for the purpose of radio a ...
(NRAO)
postdoctoral A postdoctoral fellow, postdoctoral researcher, or simply postdoc, is a person professionally conducting research after the completion of their doctoral studies (typically a PhD). The ultimate goal of a postdoctoral research position is to p ...
fellowship program is named after Karl Jansky. Additionally, NRAO awards the Jansky Prize annually in Jansky's honor. On January 10, 2012, the NRAO announced the
Very Large Array The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory located in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, ~ west of Socorro. The VLA comprises twen ...
(VLA), the radio telescope in Magdalena, New Mexico, would be renamed the Karl G. Jansky Very Large Array in honor of Karl Jansky's contribution to radio astronomy. A full-scale replica of Jansky's original rotating telescope is located on the grounds of the
Green Bank Observatory The Green Bank Observatory (previously National Radio Astronomy Observatory, Green Bank) is an astronomical observatory located in the National Radio Quiet Zone in Green Bank, West Virginia, U.S. It is the operator of the Robert C. Byrd Green ...
(, formerly an NRAO site) in
Green Bank, West Virginia Green Bank is a census-designated place in Pocahontas County in West Virginia's Potomac Highlands inside the Allegheny Mountain Range. Green Bank is located along WV 28. Green Bank is home to the Green Bank Observatory and is also close to the ...
, near a reconstructed version of
Grote Reber Grote Reber (December 22, 1911 – December 20, 2002) was an American pioneer of radio astronomy, which combined his interests in amateur radio and amateur astronomy. He was instrumental in investigating and extending Karl Jansky's pioneering wo ...
's 9-meter dish. The original site of Jansky's antenna at what is now the
Bell Labs Holmdel Complex The Bell Labs Holmdel Complex, in Holmdel Township, Monmouth County, New Jersey, United States, functioned for 44 years as a research and development facility, initially for the Bell System and later Bell Labs. The centerpiece of the campus i ...
at 101 Crawfords Corner Road,
Holmdel, New Jersey Holmdel Township (usually shortened to Holmdel) is a township in Monmouth County, New Jersey, United States. The township is centrally located in the Raritan Valley region, being within the regional and cultural influence of the Raritan Bays ...
, was determined by Tony Tyson and Robert Wilson of
Lucent Technologies Lucent Technologies, Inc. was an American Multinational corporation, multinational telecommunications equipment company headquartered in Murray Hill, New Jersey, Murray Hill, New Jersey. It was established on September 30, 1996, through the dives ...
(the successor of Bell Telephone Laboratories) in 1998, and a monument and plaque were placed there to honor the achievement. The monument is a stylized sculpture of the antenna and is oriented as Jansky's antenna was at 7:10 p.m. on September 16, 1932, at a moment of maximum signal caused by alignment with the center of our galaxy in the direction of the constellation Sagittarius. ''Jansky noise'' is named after Jansky, and refers to
high frequency High frequency (HF) is the ITU designation for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten ...
static disturbances of cosmic origin. ( Cosmic noise). Asteroid 1932 Jansky is named after him, as is the lunar crater
Jansky The jansky (symbol Jy, plural ''janskys'') 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. The ''flux density'' or ''mono ...
.


Selected writings

* * * Reprinted 65 years later as along with an explanatory preface by W.A. Imbriale, . * * *


See also

* Reber Radio Telescope *
Astronomical radio source An astronomical radio source is an object in outer space that emits strong radio waves. Radio emission comes from a wide variety of sources. Such objects are among the most extreme and energetic physical processes in the universe. History In 1932, ...
*
Radio Astronomy 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 ...


References

*. In particular Chap.1 by Sullivan, "Karl Jansky and the discovery of extraterrestrial radio waves," pp. 3–42. *. In particular Chap. 2.


External links


My Brother Karl Jansky and His Discovery of Radio Waves from Beyond the Earth
*
Serendipitous Discoveries in Radio Astronomy: Proceedings of a Workshop held at the National Radio Astronomy Observatory, Green Bank, West Virginia on May 4, 5, 6,1983; Honoring the 50th Anniversary Announcing the Discovery of Cosmic Radio Waves by Karl G. Jansky on May 5, 1933.
Edited by K. Kellermann and B. Sheets (1983) 321pp *

* ttp://www.bell-labs.com/radio-astronomy-celebration/ ''Detective Work Leads to Monument Honoring the Father of Radio Astronomy''— Radio Astronomy Celebration at NOKIA Bell Labs {{DEFAULTSORT:Jansky, Karl Guthe 1905 births 1950 deaths Amateur astronomers American astronomers 20th-century American physicists American people of Czech descent American people of English descent American people of French descent Czech-American culture in Oklahoma People from Little Silver, New Jersey People from Norman, Oklahoma Scientists at Bell Labs Radio astronomers American electrical engineers Engineers from New Jersey 20th-century American engineers