Karl Guthe Jansky

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Karl Guthe Jansky
Karl Jansky.jpg
Born(1905-10-22)October 22, 1905
DiedFebruary 14, 1950(1950-02-14) (aged 44)
Known for Radio astronomy
Scientific career
Fields Physics
Radio astronomy

Karl Guthe Jansky (October 22, 1905 – February 14, 1950) was an American physicist and radio engineer who in August 1931 first discovered radio waves emanating from the Milky Way. He is considered one of the founding figures of radio astronomy. [1]


Early life

Karl Guthe Jansky was born 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 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 (now WHA of Wisconsin Public Radio) and 9XI in Minnesota (now KUOM). [2]

Karl Jansky attended college at the University of Wisconsin where he received his BS in physics in 1927. In 1928 he joined the Bell Telephone Laboratories site in Holmdel, New Jersey. Bell Labs wanted to investigate atmospheric and ionospheric properties using "short waves" (wavelengths of about 10–20 meters) for use in trans-Atlantic radio telephone service. As a radio engineer, Jansky was assigned the job of investigating sources of static that might interfere with radio voice transmissions.

Radio astronomy

At Bell Telephone Laboratories Jansky built an antenna designed to receive radio waves at a frequency of 20.5 MHz (wavelength about 14.6 meters). It was mounted on a turntable that allowed it to be rotated in any direction, earning it the name "Jansky's merry-go-round". It had a diameter of approximately 100 ft. and stood 20 ft. tall. By rotating the antenna on a set of four Ford Model-T tires, the direction of a received signal could be pinpointed. A small shed to the side of the antenna housed an analog pen-and-paper recording system.

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 steady 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 brightest point moved away from the position of the Sun. Jansky also determined that the signal repeated on a cycle of 23 hours and 56 minutes, the period of the Earth's rotation relative to the stars (sidereal day), instead of relative to the sun (solar day). 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 of the galaxy, in the constellation of Sagittarius.

His discovery was widely publicized, appearing in the New York Times of May 5, 1933. [3] In 1933, he published a paper entitled "Electrical disturbances apparently of extraterrestrial origin". Jansky wanted to further investigate the Milky Way radio waves after 1935 (he called the radiation "star noise"), but he found little support from either astronomers, for whom it was completely foreign, or Bell Labs, which could not justify the cost of research on a phenomenon that did not significantly affect trans-Atlantic communications systems.


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, and observatories were wary of taking on any new and potentially risky projects.[ original research? ]

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, a radio engineer who singlehandedly built a radio telescope in his Illinois 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 and wrote a textbook on radio astronomy, long considered a standard by radio astronomers.

Legacy and death

Full-size replica of Jansky's radio telescope, now at the Green Bank Observatory Janksy Karl radio telescope.jpg
Full-size replica of Jansky's radio telescope, now at the Green Bank Observatory

In honor of Jansky, the unit used by radio astronomers for the strength (or flux density) of radio sources is the jansky (1 Jy = 10−26 W m−2 Hz−1). The crater Jansky on the Moon is also named after him. The National Radio Astronomy Observatory (NRAO) postdoctoral fellowship program is named after Karl Jansky. [4] Additionally, NRAO awards the Jansky Prize annually in Jansky's honor. [5] On January 10, 2012, the NRAO announced the Very Large Array (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. [6]

A full-scale replica of Jansky's original rotating telescope is located on the grounds of the Green Bank Observatory ( 38°25′53.9″N79°48′58.5″W / 38.431639°N 79.816250°W / 38.431639; -79.816250 , formerly an NRAO site) in Green Bank, West Virginia, near a reconstructed version of Grote Reber's 9-meter dish.

The original site of Jansky's antenna ( 40°21′54.5″N74°09′48.9″W / 40.365139°N 74.163583°W / 40.365139; -74.163583 ) at what is now the Bell Labs Holmdel Complex at 101 Crawfords Corner Road, Holmdel, New Jersey, was determined by Tony Tyson and Robert Wilson of Lucent Technologies (the successor of Bell Telephone Laboratories) in 1998, and a monument and plaque were placed there to honor the achievement. [7] 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. [8]

Jansky noise is named after Jansky, and refers to high frequency static disturbances of cosmic origin.

Jansky was a resident of Little Silver, New Jersey, and died at age 44 in a Red Bank, New Jersey, hospital (now called Riverview Medical Center) due to a heart condition. [9]

Asteroid 1932 Jansky is named after him. [10]

Selected writings

See also

Related Research Articles

Radio telescope form of directional radio antenna used in radio astronomy

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 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.

Very Large Array radio astronomy observatory located on the Plains of San Agustin

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, ~50 miles (64 km) west of Socorro. The VLA comprises twenty-eight 25-meter radio telescopes deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Each of the massive telescopes is mounted on double parallel railroad tracks, so the radius and density of the array can be transformed to adjust the balance between its angular resolution and its surface brightness sensitivity. Astronomers using the VLA have made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission.

National Radio Astronomy Observatory research and development center

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 astronomy. NRAO designs, builds, and operates its own high sensitivity radio telescopes for use by scientists around the world.

Grote Reber American astronomer

Grote Reber 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 work, and conducted the first sky survey in the radio frequencies.

Holmdel Horn Antenna

The Holmdel Horn Antenna is a large microwave horn antenna that was used as a satellite communication antenna and radio telescope during the 1960s at Bell Telephone Laboratories in Holmdel Township, New Jersey, United States. It was designated a National Historic Landmark in 1988 because of its association with the research work of two radio astronomers, Arno Penzias and Robert Wilson. In 1965 while using this antenna, Penzias and Wilson discovered the cosmic microwave background radiation (CMBR) that permeates the universe. This was one of the most important discoveries in physical cosmology since Edwin Hubble demonstrated in the 1920s that the universe was expanding. It provided the evidence that confirmed George Gamow's and Georges Lemaître's "Big Bang" theory of the creation of the universe. This helped change the science of cosmology, the study of the history of the universe, from a field for unlimited theoretical speculation into a discipline of direct observation. In 1978 Penzias and Wilson received the Nobel Prize for Physics for their discovery.

Astropulse citizen science project

Astropulse is a distributed computing project that uses volunteers around the globe to lend their unused computing power to search for primordial black holes, pulsars, and extraterrestrial intelligence (ETI). Volunteer resources are harnessed through Berkeley Open Infrastructure for Network Computing (BOINC) platform. In 1999, the Space Sciences Laboratory launched SETI@home, which would rely on massively parallel computation on desktop computers scattered around the world. SETI@home utilizes recorded data from the Arecibo radio telescope and searches for narrow-bandwidth radio signals from space, signifying the presence of extraterrestrial technology. It was soon recognized that this same data might be scoured for other signals of value to the astronomy and physics community.

Associated Universities, Inc. organization

Associated Universities, Inc. (AUI) is a research management corporation that builds and operates facilities for the research community. AUI is a not-for-profit 501(c)(3) corporation, headquartered in Washington, DC. The President is Dr. Adam Cohen. AUI's major current operating unit is the National Radio Astronomy Observatory (NRAO), which it operates under a Cooperative Agreement with the National Science Foundation.

Dale A. Frail is an astronomer working at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. He was born in Canada, spent much of his childhood in Europe, and his professional career has been based in the United States.

John Daniel Kraus was an American physicist known for his contributions to electromagnetics, radio astronomy, and antenna theory. His inventions included the helical antenna, the corner reflector antenna, and several other types of antennas. He designed the Big Ear radio telescope at Ohio State University, which was constructed mostly by a team of OSU students and was used to carry out the Ohio Sky Survey. Kraus held a number of patents and published widely.

Harald Trap Friis, who published as H. T. Friis, was a Danish-American radio engineer whose work at Bell Laboratories included pioneering contributions to radio propagation, radio astronomy, and radar. His two Friis formulas remain widely used.

George Clark Southworth American radio pioneer

George Clark Southworth, who published as G. C. Southworth, was a prominent American radio engineer best known for his role in the development of waveguides in the early 1930s.

Reber Radio Telescope United States historic place

The Reber Radio Telescope is a historic radio telescope, located at the Green Bank Observatory near Green Bank, West Virginia. Built in 1937 in Illinois by astronomer Grote Reber, it is the first purpose-built parabolic radio telescope. It was designated a National Historic Landmark in 1989.

Edmond Bruce was an American radio pioneer best known for creating the rhombic antenna and Bruce array.

Gennady Vasilyevich Potapenko was an American radio astronomer of Russian origin.

Bell Labs Holmdel Complex

The Bell Labs Holmdel Complex, in Holmdel Township, New Jersey, United States, functioned for forty-four years as a research and development facility, initially for the Bell System and later Bell Labs. The centerpiece of the campus is an Eero Saarinen designed structure that served as the home to over 6,000 engineers and researchers. This modernist building, dubbed "The Biggest Mirror Ever" by Architectural Forum, due to its mirror box exterior, was the site of at least one Nobel Prize discovery, the laser cooling work of Steven Chu. The building has undergone renovations into a multi-purpose living and working space, dubbed Bell Works by its redevelopers. Since 2013 it has been operated by Somerset Development, who redeveloped the building into a mixed-use office for high-tech startup companies. The complex was listed on the National Register of Historic Places in 2017.

Donald C. Backer American astronomer

Donald C. Backer was an American astrophysicist who primarily worked in radio astronomy. Backer made important contributions to the understanding and study of pulsars, black holes, and the epoch of reionization.

Semion Yakovlevich Braude was a Ukrainian physicist and radio astronomer.

Bell Telephone Laboratories may refer to:

Winston E. Kock American electrical engineer

Winston Kock (1909–1982) was the first Director of NASA Electronics Research Center in Cambridge, Massachusetts, from September 1, 1964, to October 1, 1966. The Center was created for multidisciplinary scientific research, its proximity to certain colleges, its proximity to a local U.S. Air Force research facility, and was perceived as part of the nation's cold war effort.


  1. Singh, Simon (2005), Big Bang: The Origin of the Universe, Harper Perennial, pp. 402–408, Bibcode:2004biba.book.....S, ISBN   978-0-00-716221-5 , p. 406
  2. "Cyril M. Jansky, Jr".
  3. Smothers, Ronald (June 9, 1998). "Commemorating a Discovery in Radio Astronomy". New York Times . Retrieved August 14, 2008.
  4. "Jansky Fellowship".
  5. "Jansky Prize".
  6. "VLA Rededication".
  7. "Detective Work Leads to Monument Honoring the Father of Radio Astronomy". Bell Labs. June 3, 1998.
  8. Historical Marker Database: Karl Jansky Radio Astronomy Monument
  9. "Karl G. Jansky, 44, Authority in Radio; Bell Laboratories Engineer Dies--Discovered Waves of Extraterrestrial Origin". The New York Times . February 15, 1950. Retrieved May 7, 2010. Karl Guthe Jansky of 57 Silverton Avenue, Little Silver, N.J., radio research engineer with the Bell Telephone Laboratories since 1928, who discovered radio waves of extraterrestrial origin in 1933 died yesterday in the Riverside [ sic ] Hospital, Red Bank, N.J., of a heart malady.
  10. "(1932) Jansky". Dictionary of Minor Planet Names. Springer. 2003. p. 155. doi:10.1007/978-3-540-29925-7_1933. ISBN   978-3-540-29925-7.