Karl Jansky
Karl Guthe Jansky (October 22nd 1905 - February 14th 1950), was a physicist and Engineer radio American which discovered in 1932 that our Galaxy emitted waves radio; he did not study this phenomenon ahead, but its discovery marked the birth of the Radioastronomie.
Jansky was born in Normand, in the Oklahoma, and with studied at the university of the Wisconsin where it received its license of physics in 1927.
In 1928, it joined the laboratories of Bell Telephone in the New Jersey. The Bell laboratories wanted to study the possibility of using the short waves (approximately 10-20 Mètre S of Wavelength) for the transatlantic radiotelephonic service. Jansky was charged to study the parasitic sources being able to interfere with these vocal transmissions by radio.
Jansky built a antenna conceived to collect the radio waves at a frequency of 20,5 Méga hertz (approximately 14,5 meters wavelength).
Cette antenna was installed on a rotary table, thus gaining the name of the horse-gear of Jansky .
En turning the antenna, one could find the direction of the radio signals which were collected.
After having recorded signals in all the directions during several months, Jansky identified three types of parasites: close storms, storms moved away, and a weak but regular whistle of unknown origin. Jansky spent the following year to study this third type of parasites. The signals started and stopped once per day. Jansky believed initially that it collected signals coming from the Sun. But while following the signal during a few months, he realized that the origin of the signal moved away from the position of the Sun. He notices whereas the signal was not repeated every 24 hours, but every 23 hours and 56 minutes. It is the period characteristic of the fixed star S and other objects distant from our solar system: duration of a sidereal day. Thereafter, it establishes that this signal came from the Milky Way and was most intense in the direction of its center, in the Constellation of the Sagittarius.
The discovery was made public, in particular in the NewYork Times of the May 5th 1933.
Jansky wanted to continue on the impetus of this discovery and to study more in detail the radio waves of the Milky Way.
Il proposed at the Bell laboratories to build a parabolic Aerial 30 meters in diameter.
Mais the laboratories of Beautiful had the answer to their question: the parasites were not a problem for the transatlantic communication by radio.
Jansky was assigned with another project and did not make any more radioastronomy.
Many scientists was fascinated by the discovery Jansky, but nobody continued research on this subject during several years; it was then the Grande Depression, and the observatories could not be allowed to engage on new projects.
Two men having learned the discovery from Jansky into 1933 had later a great influence on the development of radioastronomy. The first was Grote Reber; in 1937, it built only a radio telescope in its back-yard and made the first systematic outline of the sky by radio waves. The second was John Kraus; after the Second world war, it founded the first radio observatory at the university of the State of the Ohio and wrote a handbook of radioastronomy which is always the “bible” of the radioastronomers.
In the honor of Jansky, the unit employed by the radioastronomers for the intensity (or more exactly the Density flux) of the radio sources is the Jansky (symbol: Jy). One also named a Astéroïde in his honor: (1932) Jansky.
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