Karl Guthe Jansky 180079 224463957 2008-07-08T23:16:52Z Astrochemist 1252182 Added a photograph to an article lacking pictures {{Infobox Scientist |name = {{PAGENAME}} |box_width = |image =Replace_this_image_male.svg |image_size =150px |caption = {{PAGENAME}} |birth_date = [[October 22]], [[1905]] |birth_place = [[Territory of Oklahoma]] |death_date = [[February 14]], [[1950]] |death_place = [[Red Bank, New Jersey]] |residence = |citizenship = |nationality = [[United States|American]] |ethnicity = |field = [[physics]]<br/>[[radio astronomy]] |work_institutions = |alma_mater = |doctoral_advisor = |doctoral_students = |known_for = [[radio astronomy]] |author_abbrev_bot = |author_abbrev_zoo = |influences = |influenced = |prizes = |religion = |footnotes = |signature = }}'''Karl Guthe Jansky''' ([[October 22]], [[1905]] &ndash; [[February 14]], [[1950]]), was an [[United States|American]] [[physicist]] and [[radio]] [[engineer]] who in August [[1931]] first discovered [[radio wave]]s emanating from the [[Milky Way]]. He is considered one of the founding figures of [[radio astronomy]]. == 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|University of Oklahoma at Norman]]. Dean 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. Karl Jansky's mother, née Nellie Moreau, was of French and English descent. He was named after Dr. Karl Guthe, who had been an important mentor to Karl's father, C. M. Jansky, who was an engineer with a strong interest in physics, a trait passed on to his sons. 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]]). == Education and engineering == Jansky attended college at the [[University of Wisconsin-Madison]] where he received his [[bachelor of science|BS]] in [[physics]] in [[1927]]. In [[1928]] he joined the [[Bell Labs | Bell Telephone Laboratories]] site in [[Holmdel, New Jersey]]. Bell Labs wanted to investigate [[atmosphere|atmospheric]] and [[ionosphere|ionospheric]] properties using "[[short wave]]s" ([[wavelength]]s of about 10-20 [[metre|meters]]) for use in transatlantic [[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 == Jansky built an [[antenna (electronics)|antenna]] designed to receive radio waves at a [[frequency]] of 20.5 [[megaHertz|MHz]] (wavelength about 14.6 meters). It was mounted on a turntable that allowed it to rotate 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 signal|analog]] pen-and-paper recording system. (A photograph of Jansky with his antenna in Holmdel appears in the documentation of a related device, the [[Reber Radio Telescope]].<ref name="nrhpinv2">{{citation|title={{PDFlink|[http://pdfhost.focus.nps.gov/docs/NHLS/Text/72001291.pdf National Register of Historic Places Inventory-Nomination: Reber Radio Telescope]|475&nbsp;[[Kibibyte|KiB]]<!-- application/pdf, 486897 bytes -->}}|date=May 1, 1989 |author=Harry Butowsky |publisher=National Park Service}} and {{PDFlink|[http://pdfhost.focus.nps.gov/docs/NHLS/Photos/72001291.pdf Accompanying 3 photos: from 1962, from c.1960 (with Grote Reber), and one of Karl Jansky, another astronomy pioneer, from c.1930.]|738&nbsp;[[Kibibyte|KiB]]<!-- application/pdf, 755817 bytes -->}}</ref>) [[Image:Janksy Karl radio telescope.jpg|right|200px|thumb|Full-size replica of Jansky's radio telescope, now at the National Radio Astronomical Observatory]] 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. This four-minute lag is a typical astronomical characteristic of any "fixed" object located far from our solar system (see [[sidereal 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 the galaxy, in the [[constellation]] of [[Sagittarius (constellation)|Sagittarius]]. His discovery was widely publicized, appearing in the ''[[New York Times]]'' of [[May 5]] [[1933]]. <ref>[http://query.nytimes.com/gst/fullpage.html?res=9804E3DE153AF93AA35755C0A96E958260 1998 NYTimes article]</ref> He published his classic paper "Electrical disturbances apparently of extraterrestrial origin" in Proc. IRE in 1933. This paper was re-printed in Proc. IEEE in 1984 (for their centennial issue, where they note the research most likely would have won a Nobel prize, had not the author died young) and again in 1998, for the first centennial of radio. Jansky wanted to follow up on this discovery and investigate the radio waves from the Milky Way in further detail. He submitted a proposal to Bell Labs to build a 30 meter diameter [[dish antenna]] with greater sensitivity that would allow more careful measurements of the structure and strength of the radio emission. Bell Labs, however, rejected his request for funding on the grounds that the detected emission would not significantly affect their planned transatlantic communications system. Jansky was re-assigned to another project and did no further work in the field of astronomy. == Follow-up == Several scientists were interested by 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. 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 Prof. [[John D. Kraus]], who, after [[World War II]], started a radio observatory at [[Ohio State University]] and wrote a textbook on radio astronomy, still considered a standard by many radio astronomers. == Legacy == 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<sup>-26</sup> W m<sup>-2</sup> Hz<sup>-1</sup>). [[Jansky (crater)|Jansky crater]] on the [[Moon]] is also named after him. The [[National Radio Astronomy Observatory|NRAO]] [[postdoctoral]] [http://www.nrao.edu/administration/directors_office/jansky-postdocs.shtml fellowship program] is named after Karl Jansky. A full-scale replica of Jansky's original rotating telescope is located on the grounds of the [[National Radio Astronomy Observatory|NRAO]] site in [[Green Bank, West Virginia]], near a reconstructed version of Grote Reber's 9m dish. The original site of Jansky's antenna (40.365175 deg. N, 74.163705 deg. W) was determined by [[Lucent Technologies]] (the successor of Bell Telephone Laboratories) in the 1990's, and a plaque was placed there honoring the achievement. The original site is located at 101 Crawfords Corner Road, [[Holmdel, New Jersey]]. As mentioned above, a photograph of Jansky with his antennas appears in documentation of [[Reber Radio Telescope]]. ''Jansky noise'' is named after Jansky, and refers to [[high frequency]] [[noise (radio)|static disturbance]]s of [[cosmic]] origin. Jansky was a resident of [[Little Silver, New Jersey]], and died at age 44 in a [[Red Bank, New Jersey]] hospital due to a heart condition.<ref>http://select.nytimes.com/gst/abstract.html?res=F60A1EF73F5B12718DDDAC0994DA405B8089F1D3 "KARL G. JANSKY, 44, AUTHORITY IN RADIO; Bell Laboratories Engineer Dies--Discovered Waves of Extraterrestrial Origin"], ''[[The New York Times]]'', [[February 15]], [[1950]]. Accessed [[June 3]], [[2008]]. "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 Hospital, Red Bank, N.J., of a heart malady."</ref> == References == {{reflist}} Publications by Karl G. Jansky: *1932: [http://ieeexplore.ieee.org/search/wrapper.jsp?arnumber=1685061 Directional studies of atmospherics at high frequencies], Proc.IRE, 20, p.1920. *1933: [http://ieeexplore.ieee.org/search/wrapper.jsp?arnumber=1685232 Electrical disturbances apparently of extraterrestrial origin], Proc.IRE, 21, p.1387. ({{doi-inline|10.1109/JPROC.1998.681378|Re-printed}} in Proc. IEEE, vol. 86, no. 7 (July 1998), pp. 1510-1515.) Published with the reprint is an explanatory article {{doi-inline|10.1109/JPROC.1998.681377|Introduction To "Electrical Disturbances Apparently Of Extraterrestrial Origin"}}. *1933: "Radio waves from outside the solar system", Nature, 132, p.66. *1933: "Electrical phenomena that apparently are of interstellar origin", Popular Astronomy, 41, p.548, Dec.1933. *1935: [http://ieeexplore.ieee.org/search/wrapper.jsp?arnumber=1685771 A note on the source of interstellar interference], Proc.IRE, 23, p.1158. *1937: [http://ieeexplore.ieee.org/search/wrapper.jsp?arnumber=1686314 Minimum noise levels obtained on short-wave radio receiving systems], Proc.IRE, 25, p.1517. *[http://www.bigear.org/vol1no4/jansky.htm My Brother Karl Jansky and His Discovery of Radio Waves from Beyond the Earth] *[http://www.lsst.org/jansky.shtml The Jansky Monument] *{{cite web | author=F. Ghigo | date = 2006-02-07 | url = http://www.nrao.edu/whatisra/hist_jansky.shtml | title = Karl Jansky and the Discovery of Cosmic Radio Waves | publisher = National Radio Astronomy Observatory | language = English | accessdate = 2006-08-24 }} ==See also== *[[Reber Radio Telescope]] {{DEFAULTSORT:Jansky, Karl Guthe}} [[Category:1905 births]] [[Category:1950 deaths]] [[Category:Amateur astronomers]] [[Category:American astronomers]] [[Category:American engineers]] [[Category:American physicists]] [[Category:Czech-Americans]] [[Category:People from Monmouth County, New Jersey]] [[Category:People from Norman, Oklahoma]] [[Category:Scientists at Bell Labs]] [[bn:কার্ল গাথ জান্‌স্কি]] [[da:Karl Guthe Jansky]] [[de:Karl Guthe Jansky]] [[es:Karl Guthe Jansky]] [[fr:Karl Jansky]] [[it:Karl Guthe Jansky]] [[nl:Karl Jansky]] [[ja:カール・ジャンスキー]] [[pl:Karl Guthe Jansky]] [[fi:Karl Jansky]] [[sv:Karl Guthe Jansky]] [[th:คาร์ล แจนสกี]] [[zh:卡尔·央斯基]]