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Karl Guthe Jansky was born in Norman Oklahoma October 22, 1905 (d.Feb.14, 1950), graduated with a degree in physics from the University of Wisconsin, and joined the staff of the Bell Telephone Laboratories in Holmdel, NJ, in 1928.
Bell Labs wanted to investigate using "short waves" (wavelengths of about 10-20 meters) for transatlantic radio telephone service. Jansky was assigned the job of investigating the sources of static that might interfere with radio voice transmissions.
He built an antenna, pictured here, designed to receive radio waves at a frequency of 20.5 MHz (wavelength about 14.5 meters). It was mounted on a turntable that allowed it to rotate in any direction, earning it the name "Jansky's merry-go-round". By rotating the antenna, one could find what the direction was to any radio signal.
After recording signals from all directions for several months, Jansky identified three types of static:
1. nearby thunderstorms, 2. distant thunderstorms, and 3. a faint steady hiss of unknown origin. Jansky spent over a year investigating the third type of static. It rose and fell once a day, leading Jansky to think at first that he was seeing radiation from the Sun.
But after a few months of following the signal, the brightest point moved away from the position of the Sun. The signal repeated not every 24 hours, but every 23 hours and 56 minutes. This is characteristic of the fixed stars, and other objects far from our solar system. He eventually figured out that the radiation was coming from the Milky Way and was strongest in the direction of the center of our Milky Way galaxy, in the constellation of Sagittarius.
Jansky wanted to follow up on this discovery and investigate the radio waves from the Milky Way Galaxy in more detail. He proposed to Bell Labs to build a 100 foot (30 meter) diameter dish antenna. But Bell Labs had the answer they wanted about static: the static was not a problem for transatlantic radio communication. Jansky was assigned to another project and did no more radio astronomy.
Two men who learned of Jansky's discovery in 1933 were of great influence on the later development of the new study of radio astronomy: one was Grote Reber, who singlehandedly built a radio telescope in his back yard in 1937 and did the first systematic survey of radio waves from the sky. The second was John Kraus, who, after World War II, started a radio observatory at Ohio State University and wrote a textbook on radio astronomy, which is still the "bible" for radio astronomers.
Jansky's role as the "Father of Radio Astronomy" is commemorated in various ways:
Publications by Karl G. Jansky
Note: many of these early papers have been re-printed in "Classics in Radio Astronomy", by W.T.Sullivan, published by Cambridge University Press, 1982
by C. M. Jansky, Jr. (Karl's brother)
Modified on Tuesday, 07-Feb-2006 13:13:48 EST