Karl Guthe Jansky was an American physicist and radio engineer.
Background
Jansky was born on October 22, 1905, in Norman, Oklahoma, the third of four sons and third of the six children of Cyril Methodius Jansky and Nellie (Moreau) Jansky. His mother was descended from a Franco-English family that had settled in the United States early in the eighteenth century; his paternal grandfather, a stonemason, had emigrated from Bohemia (later Czechoslovakia) in 1866 and had taken up a homestead in Richland County, Wis. Karl's father, an electrical engineer, was head of the school of applied sciences at the University of Oklahoma until 1908, when he moved to the University of Wisconsin. The children grew up in a comfortably situated family, in an atmosphere that was both warm and competitive. Their mother was gentle; their vigorous father taught them to argue and criticize, to enjoy winter sports, to play games such as chess and bridge, and to respect knowledge.
Education
Karl developed an interest in radio and built an early crystal set. He entered the University of Wisconsin, where he majored in physics and received the B. S. degree in 1927 and the M. S. in 1936. He remained at the university for a year as instructor.
Career
In 1928 Jansky began work at the Cliffwood, New Jersey, laboratory of the Bell Telephone Company. Two years later the laboratory was moved to Holmdel, New Jersey, where in 1931 he made the first of the observations that led to his discovery of radio emissions from space. Jansky had been assigned the practical problem of tracing the source of the atmospherics, or natural static, that sometimes interfered with transoceanic radiotelephone communication. To determine the intensity of the static, the directions from which it arrived, and the time pattern of its appearance, he used a shortwave receiving system. By the end of 1932 he had found three major types of interference: local thunderstorms, distant major storms, and a "very steady hiss type static the origin of which is not yet known. " Although it was stronger than a similar electrical noise generated by the receiver, it corresponded to a very weak signal. Jansky refused to dismiss the puzzle and persisted in trying to find an explanation. In analyzing his data, he found that the source of the background noise changed direction, going completely around the compass in a period of twenty-four hours. The noise was strongest when the antenna reception cone pointed south at noon in December 1931; it came from the west at night and from the east in the morning. He therefore theorized that the noise might have its origin in the sun. But after several false starts he made the extraordinary discovery that as the seasons progressed and the sun moved past the stars, the signal was fixed with respect to the stars, not to the sun. Thus, in June 1932 the strongest signal received when the antenna pointed south came at midnight, not noon. By the end of the year he had determined that the hiss static, which he later called star-noise, came from a direction that was fixed in space. In three papers published in 1933 he suggested the strong probability that the unidentified static originated in the center of the Milky Way, in the constellation Sagittarius, which has long been recognized as the center of our galaxy. Two years later, in 1935, he suggested that the radiation arose in interstellar space from the thermal motion of charged particles or, less probably, in stars in the crowded galactic center. Jansky's discovery attracted little attention from astronomers, and the few who did suspect its importance could find no theoretical mechanism that would account for his observations. Jansky himself recognized that further research would require larger, more expensive, highly directional antennas and receivers than those extant. Jansky ended this type of observation in 1936, and Bell Laboratories set him to work on other problems. He turned to studying the effects of man-made sources of radio interference and helped determine the best sites for receiving transatlantic radio transmissions. With his colleague C. F. Edwards, he studied the angle of arrival and the practical usefulness of radio waves and their echoes at various locations and for antennas of various sizes and carried out experiments in radio propagation. During World War II Jansky did research on radio direction finders, for which he received an army-navy citation. Soon after the war, the advent of high-frequency radio and telephone-line transmission involved him in the technical development of sensitive and reliable amplifiers. After 1945 declining health resulting from hypertensive cardiovascular disease required him to take extended leaves from work. Jansky died at the age of forty-four, on February 14, 1950, in Riverview Medical Center in Red Bank, New Jersey, of a cerebral thrombosis. His remains were cremated.
Achievements
Jansky's detection of radio waves from the center of our galaxy, a distance of 30, 000 light-years, was a revolutionary event in the history of astronomy. It opened the way to exploring the universe at wavelengths a million times longer than those constituting the narrow, visible spectrum of light.
Interests
Although Jansky was often ill, because of a chronic kidney infection acquired during his college days, he enjoyed playing golf, softball, and games that involved problem-solving, such as chess.
Connections
On August 3, 1929, Jansky married Alice La Rue Knapp. Their children were Anne Moreau and David Burdick Jansky. The family lived in Little Silver, New Jersey.
