Karl Guthe Jansky

Karl Guthe Jansky 1905-50, American radio engineer; b. Norman, Okla. After graduating (1927) from the Univ. of Wisconson, he joined the Bell Telephone Laboratories. While trying to determine the causes of radio communications static, Jansky discovered (1931) radio waves from extraterrestrial sources—a discovery that prompted the investigations of Gröte Reber and led to the development of the science of radio astronomy . By 1932 Jansky had concluded that the source of the interference was located in the direction of the center of the Milky Way galaxy.

Jansky's discovery was serendipitous. Not only was it by chance that he had chosen a frequency at which the galactic center emits large amounts of radiation and at which the earth's atmosphere is transparent, he also was working at a period of minimum sunspot activity which occurs only every 11 years. At sunspot maximum, the ionosphere would have blocked all extraterrestrial radio waves at the 20 MHz frequency, and signals from the Milky Way would not have been detected.

Jansky, KarlGuthe (1905–50)Americanradio research engineer. In 1931 he began to study atmospheric ‘static’ that interfered with telecommunications. By the end of 1932 he had accounted for all but one persistent signal, which he concluded came from outside the Solar System in the direction of the constellation Sagittarius, towards the centre of our Galaxy. Thus was born radio astronomy, although Jansky himself never followed up his discovery. In radio astronomy, the unit of flux density is now named the jansky in his honour.