Editing Karl Guthe Jansky

{{short description|American physicist and radio engineer (1905–1950)}}
{{Use mdy dates|date=July 2019}}
{{Infobox scientist
| name              = Karl Guthe Jansky
| image             = Karl_Jansky.jpg
| image_size        = 225px
| caption           = 
| birth_date        = {{birth date|1905|10|22}}
| birth_place       = [[Norman, Oklahoma|Norman]], [[Territory of Oklahoma|Oklahoma]], U.S.
| death_date        = {{death date and age|1950|2|14|1905|10|22}}
| death_place       = [[Red Bank, New Jersey]], U.S.
| residence         = 
| field             = [[Physics]]<br />[[Radio astronomy]]
| workplaces        = [[Bell Labs]]
| alma_mater        = [[University of Wisconsin]] (BS)
| doctoral_advisor  = 
| doctoral_students = 
| known_for         = [[Radio astronomy]]
| author_abbrev_bot = 
| author_abbrev_zoo = 
| influences        = 
| influenced        = 
| prizes            = 
| footnotes         = 
| signature         = 
}}

'''Karl Guthe Jansky''' (October 22, 1905 – February 14, 1950) was an American [[physicist]] and radio engineer who in April 1933 first announced his discovery of [[radio wave]]s emanating from the [[Milky Way]] in the constellation [[Sagittarius (constellation)|Sagittarius]]. He is considered one of the founding figures of [[radio astronomy]].<ref>{{Citation |first=Simon |last=Singh |author-link=Simon Singh |title=Big Bang: The Origin of the Universe |publisher=Harper Perennial |year=2005 |isbn=978-0-00-716221-5 |pages=402–408 |title-link=Big Bang: The Origin of the Universe |bibcode=2004biba.book.....S }}, p.&nbsp;406</ref>

== 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]] 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 (AM)|WHA]] of [[Wisconsin Public Radio]]) and 9XI in [[Minnesota]] (now [[KUOM]]).<ref>{{cite web | url = http://www.ieeeghn.org/wiki/index.php/Cyril_M._Jansky,_Jr. | title = Cyril M. Jansky, Jr.| date = January 20, 2016}}</ref>

Karl Jansky attended college at the [[University of Wisconsin–Madison|University of Wisconsin]], where he received his [[Bachelor of Science|BS]] in [[physics]] in 1927. He stayed an extra year at Madison, completing all the graduate course work for a master's degree in physics except for the thesis. In July 1928 at age 22, he was able to join the [[Bell Labs|Bell Telephone Laboratories]], 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]].<ref name=50th>[http://library.nrao.edu/public/collection/02000000000280.pdf 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 </ref>{{rp|40}} Bell Labs wanted to investigate [[atmosphere|atmospheric]] and [[ionosphere|ionospheric]] properties using "[[short wave]]s" ([[wavelength]]s 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 (radio)|static]] that might interfere with radio voice transmissions.

== Radio astronomy ==
[[File:JanskyatAntenna hi.tif|thumb|Jansky and his rotating directional radio antenna (early 1930s), the world's first radio telescope.]]
<!-- Deleted image removed: [[File:Karl Guthe Jansky radio telescope.jpeg|thumb|right|Karl Jansky makes adjustments to his antenna, used to identify radio waves from outer space for the first time.]]  -->
At Bell Telephone Laboratories, Jansky built a [[directional antenna]] designed to receive radio waves at a [[frequency]] of 20.5 [[megaHertz|MHz]] (wavelength about 14.6 meters). It had a diameter of approximately 100&nbsp;ft. (30 meters) and stood 20&nbsp;ft. (6 meters) 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).<ref name="50th" />{{rp|vii}}  By rotating the antenna, the direction of a received signal could be pinpointed. The intensity of the signal was recorded by an [[analog signal|analog]] pen-and-paper recording system housed in a small shed to the side of the antenna.<ref name="kraus 1981">{{cite web |last1=Kraus |first1=John |title=The First 50 Years of Radio Astronomy, Part 1: Karl Jansky and His Discovery of Radio Waves from Our Galaxy |url=http://www.bigear.org/CSMO/HTML/CS12/cs12p08.htm |publisher=North American AstroPhysical Observatory (NAAPO). Cosmic Search, Vol. 3, No. 4 |access-date=21 September 2021 |date=Fall 1981 |quote=In 1930 essentially all that we knew about the heavens had come from what we could see or photograph. Karl Jansky changed all that. A universe of radio sounds to which mankind had been deaf since time immemorial now suddenly burst forth in full chorus.}}</ref>

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 surmise initially 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 the astrophysicist Albert Melvin Skellett, who pointed out that the observed time between the signal peaks was the exact length of a [[sidereal time|sidereal day]]; the time it took for "fixed" astronomical objects, such as a star, to pass in front of the antenna every time the Earth rotated.<ref name="bookrags.com">{{cite book | url = http://www.bookrags.com/biography/karl-jansky-wsd/ | title = World of Scientific Discovery on Karl Jansky | access-date = 2010-04-09}}</ref> By comparing his observations with optical astronomical maps, Jansky concluded that the radiation was coming from the [[Milky Way]] and was strongest (7:10 p.m. on September 16, 1932) in the direction of the center of the galaxy, in the [[constellation]] of [[Sagittarius (constellation)|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.<ref>{{Citation |editor-first=W. T. |editor-last=Sullivan |title=The Early Years of Radio Astronomy: Reflections Fifty Years After Jansky's Discovery |publisher=Cambridge University Press |year=1984 |isbn=978-0-521-61602-7 }}</ref> His discovery was widely publicized, appearing in the ''[[New York Times]]'' of May 5, 1933,<ref>{{cite news | author = Smothers, Ronald | title = Commemorating a Discovery in Radio Astronomy |date = June 9, 1998 |work = [[New York Times]] | url = https://query.nytimes.com/gst/fullpage.html?res=9804E3DE153AF93AA35755C0A96E958260 | access-date = 2008-08-14}}</ref> and he was interviewed on a special NBC program on "Radio sounds from among the stars".<ref name="kraus 1981" /> 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]]''.<ref>{{cite journal |last1=Karl Jansky |title=Electrical Disturbances Apparently of Extraterrestrial Origin |journal=Proceedings of the Institute of Radio Engineers |date=Oct 1933 |volume=21 |issue=10 |pages=1387–1398 |doi=10.1109/JRPROC.1933.227458|url=https://ieeexplore.ieee.org/document/681378}} See also {{cite journal |last1=Karl Jansky |title=Radio Waves from Outside the Solar System |journal=Nature |date=Jul 8, 1933 |volume=132 |issue=3323 |page=66 |doi=10.1038/132066a0 |bibcode=1933Natur.132...66J |s2cid=4063838 |url=https://www.nature.com/articles/132066a0.pdf}}</ref>

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 were produced from interstellar gas, in particular, by "thermal agitation of charged particles."<ref name="bookrags.com" /> 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),<ref name="MagL-Jansky">{{cite web |title=Karl Jansky |url=https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/karl-jansky |website=MagLab |publisher=National High Magnetic Field Laboratory. |access-date=17 June 2022}}</ref><ref>{{cite web |title=Jansky, Karl (1905–1950) |url=https://www.encyclopedia.com/people/science-and-technology/electrical-engineering-biographies/karl-jansky |website=Encyclopedia.com |access-date=17 June 2022 |date=17 May 2018}}</ref> but he found little support from either astronomers, for whom it was completely foreign, or Bell Labs, which could not justify, during the [[Great 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, and observatories were wary of taking on any new and potentially risky projects.<ref name="nrao 2003">{{cite web |last1=Ghigo |first1=F |title=Karl Jansky and the Discovery of Cosmic Radio Waves |url=http://legacy.nrao.edu/epo/aoc/puente/jansky/hist_jansky.shtml |website=nrao.edu |publisher=National Radio Astronomy Observatory |access-date=1 October 2021 |date=2003}}</ref>

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.<ref name="nrao 2003" />

{{quote| In 1930 essentially all that we knew about the heavens had come from what we could see or photograph. Karl Jansky changed all that. A universe of radio sounds to which mankind had been deaf since time immemorial now suddenly burst forth in full chorus.  –John D. Krauss <ref name="kraus 1981" /> }}

== Death and legacy ==
[[File:Very Large Array -- New Mexico, U.S.A. -- 2009-08.jpg|thumb|Karl G. Jansky Very Large Array, National Radio Astronomy Observatory, New Mexico]]
[[Image:Janksy Karl radio telescope.jpg|right|thumb|Full-size replica of Jansky's radio telescope, now at the [[Green Bank Observatory]]]] 
[[File:Green Banks - Jansky Antena info.jpg|thumb|Green Bank plaque: Jansky Antenna]]

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.<ref>{{cite news |title=Karl G. Jansky, 44, Authority in Radio; Bell Laboratories Engineer Dies–Discovered Waves of Extraterrestrial Origin |url=https://www.nytimes.com/1950/02/15/archives/karl-g-jansky-44-authority-in-radio-bell-laboratories-engineer.html |newspaper=[[The New York Times]] |date=February 15, 1950 |access-date=May 7, 2010 |quote=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.}}</ref>

{{quote | Had Jansky not died at a very early age, he would undoubtedly have been awarded the Nobel Prize.  His serendipitous discovery gave birth to a new branch of astronomy, radio astronomy. –William A. Imbriale <ref>{{cite journal |last1=Imbriale |first1=William A |title=Introduction to "Electrical Disturbances Apparently of Extraterrestrial Origin" |journal=Proceedings of the IEEE |date=July 1998 |volume=86 |issue=7 |pages=1507–1509 |doi=10.1109/JPROC.1998.681377 |quote=Had Jansky not died at a very early age, he would undoubtedly have been awarded the Nobel Prize. His serendipitous discovery gave birth to a new branch of astronomy, radio astronomy.}}</ref>}}

In honor of Jansky, the unit used by radio astronomers for the [[spectral irradiance]] of radio sources is the [[jansky]] (1&nbsp;Jy = 10<sup>−26</sup>&nbsp;W⋅m<sup>−2</sup>⋅Hz<sup>−1</sup>).  The crater [[Jansky (crater)|Jansky]] on the [[Moon]] is also named after him. The [[National Radio Astronomy Observatory]] (NRAO) [[postdoctoral]] fellowship program is named after Karl Jansky.<ref>{{cite web |url=http://www.nrao.edu/administration/directors_office/jansky-postdocs.shtml |title=Jansky Fellowship}}</ref> NRAO awards the Jansky Prize annually in Jansky's honor.<ref>{{cite web |url=http://www.nrao.edu/jansky/janskyprize.shtml |title=Jansky Prize}}</ref>  On March 31, 2012, the NRAO renamed the [[Very Large Array]] (VLA) radio telescope in Magdalena, New Mexico, as the Karl G. Jansky Very Large Array in honor of Jansky's contribution to radio astronomy.<ref>{{cite web |url=http://www.nrao.edu/pr/2012/jansky/ |title=VLA Rededication}}</ref>

A full-scale replica of Jansky's original rotating telescope is located on the grounds of the [[Green Bank Observatory]] ({{nowrap|{{coord|38|25|53.9|N|79|48|58.5|W|type:landmark_region:US-WV|display=inline}}}}, formerly an [[National Radio Astronomy Observatory|NRAO]] site) in [[Green Bank, West Virginia]], near a reconstructed version of [[Grote Reber]]'s 9-meter dish.

In 1998, the original site of Jansky's antenna {{nowrap|({{coord|40|21|54.5|N|74|09|48.9|W|type:landmark_region:US-NJ|display=inline}})}} at what is now the [[Bell Labs Holmdel Complex]] at 101 Crawfords Corner Road, [[Holmdel, New Jersey]], was determined by [[J. Anthony Tyson|Tony Tyson]] and [[Robert Woodrow Wilson|Robert Wilson]] of [[Lucent Technologies]] (the successor of Bell Telephone Laboratories) and a monument and a plaque were placed there to honor the achievement.<ref>{{cite web
 |url =  http://www.bell-labs.com/radio-astronomy-celebration/
 |title = Detective Work Leads to Monument Honoring the Father of Radio Astronomy
 |date = June 3, 1998
 |publisher = Bell Labs
 |archive-url=https://web.archive.org/web/20200103123745/http://www.bell-labs.com/radio-astronomy-celebration/
 |archive-date=3 January 2020 |url-status=dead}}</ref> The monument is a stylized sculpture of the antenna and is oriented as Jansky's antenna was at 7:10&nbsp;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.<ref>{{Cite web |url=http://www.hmdb.org/marker.asp?marker=17286 |title=Historical Marker Database: Karl Jansky Radio Astronomy Monument |access-date=October 22, 2011 |archive-date=December 1, 2016 |archive-url=https://web.archive.org/web/20161201090414/http://www.hmdb.org/marker.asp?marker=17286 |url-status=dead }}</ref>

''Jansky noise'' is named after Jansky, and refers to [[high frequency]] [[Noise (radio)|static disturbances]] of [[Cosmos|cosmic]] origin, [[cosmic noise]].

Asteroid [[1932 Jansky]] is named after him,<ref>{{cite book|title=Dictionary of Minor Planet Names |pages = 155|publisher=Springer |date=2003 |isbn=978-3-540-29925-7 |doi=10.1007/978-3-540-29925-7_1933 |chapter = (1932) Jansky }}</ref> as is the lunar crater [[Jansky (crater)|Jansky]].

== Selected writings ==
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=December 1932 |title=Directional studies of atmospherics at high frequencies |journal=[[Proc. IRE]] |volume=20 |issue=12 |page=1920|doi=10.1109/JRPROC.1932.227477 |s2cid=51660959 }}
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=8 July 1933 |title=Radio waves from outside the solar system |journal=Nature |volume=132 |issue=3323 |page=66|doi=10.1038/132066a0 |bibcode=1933Natur.132...66J |s2cid=4063838 |doi-access=free }}
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=October 1933 |title=Electrical disturbances apparently of extraterrestrial origin |journal=Proc. IRE |volume=21 |issue=10 |page=1387 |doi=10.1109/JRPROC.1933.227458 }} Reprinted 65 years later as {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |title=Electrical disturbances apparently of extraterrestrial origin |doi=10.1109/JPROC.1998.681378 |journal=[[Proc. IEEE]] |volume=86 |issue=7 |date=July 1998 |pages=1510–1515|s2cid=47549559 }} along with an explanatory preface by W.A. Imbriale, {{doi-inline|10.1109/JPROC.1998.681377|Introduction To "Electrical Disturbances Apparently Of Extraterrestrial Origin"}}.
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=December 1933 |title=Electrical phenomena that apparently are of interstellar origin |journal=Popular Astronomy |volume=41 |page=548 |bibcode=1933PA.....41..548J }}
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=October 1935 |title=A note on the source of interstellar interference |journal=Proc. IRE |volume=23 |issue=10 |page=1158|doi=10.1109/JRPROC.1935.227275 |s2cid=51632813 }}
* {{cite journal |last=Jansky |first=Karl Guthe |author-link=Karl Guthe Jansky |date=December 1937 |title=Minimum noise levels obtained on short-wave radio receiving systems |journal=Proc. IRE |volume=25 |issue=12 |page=1517|doi=10.1109/JRPROC.1937.228780 |s2cid=51660095 }}

==See also==
*[[Reber Radio Telescope]]
*[[Astronomical radio source]]
*[[Radio Astronomy#History|Radio Astronomy]]

== References ==
{{reflist|30em}}

*{{Citation |editor-first=W. T. |editor-last=Sullivan |title=The Early Years of Radio Astronomy: Reflections Fifty Years After Jansky's Discovery |publisher=Cambridge University Press |year=1984 |isbn=978-0-521-61602-7 }}. In particular Chap.1 by Sullivan, "Karl Jansky and the discovery of extraterrestrial radio waves," pp.&nbsp;3–42.
*{{Citation |first=W. T. |last=Sullivan |title=Cosmic Noise: A History of Early Radio Astronomy|publisher=Cambridge University Press |year=2009|bibcode=2009cnhe.book.....S }}. In particular Chap. 2.

== External links ==
{{Commons category}}
*[http://www.bigear.org/vol1no4/jansky.htm My Brother Karl Jansky and His Discovery of Radio Waves from Beyond the Earth]
*{{cite web|last=Ghigo|first=F.|date=February 7, 2006|url=http://www.nrao.edu/whatisra/hist_jansky.shtml|title=Karl Jansky and the Discovery of Cosmic Radio Waves|publisher=[[National Radio Astronomy Observatory]]}}
*[http://library.nrao.edu/public/collection/02000000000280.pdf 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
*{{NHLS url|id=72001291|title=Accompanying 3 photos: from 1962, from c.1960 (with Grote Reber), and one of Karl Jansky, another astronomy pioneer, from c.1930.|photos=y}}
* [https://web.archive.org/web/20110609174230/http://digital.library.okstate.edu/encyclopedia/entries/J/JA011.html Encyclopedia of Oklahoma History and Culture – Jansky, Karl]
*[http://www.bell-labs.com/radio-astronomy-celebration/ ''Detective Work Leads to Monument Honoring the Father of Radio Astronomy''] — Radio Astronomy Celebration at [[Bell Labs|NOKIA Bell Labs]]

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{{Radio-astronomy}}

{{DEFAULTSORT:Jansky, Karl Guthe}}
[[Category:1905 births]]
[[Category:1950 deaths]]
[[Category:Amateur astronomers]]
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[[Category:20th-century American physicists]]
[[Category:American people of Czech descent]]
[[Category:American people of English descent]]
[[Category:American people of French descent]]
[[Category:Czech-American culture in Oklahoma]]
[[Category:People from Little Silver, New Jersey]]
[[Category:People from Norman, Oklahoma]]
[[Category:Scientists at Bell Labs]]
[[Category:Radio astronomers]]
[[Category:American electrical engineers]]
[[Category:Engineers from New Jersey]]
[[Category:20th-century American engineers]]
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