Sun’s Radio Emissions Discovered

Sun’s Radio Emissions Discovered

Pioneering British physicist and radio astronomer James Stanley Hey discovered radio emissions coming from the Sun, almost by accident, in the course of his work for the United Kingdom’s Army Operational Research Group during World War II.

Hey was the third son of a Lancashire cotton manufacturer, and was interested in science from an early age. He studied physics at Manchester University followed by a master’s degree in X-ray Crystallography, which he completed in 1931. After graduating he began work as a physics teacher in a grammar school, but his comfortable way of life changed dramatically with the outbreak of World War II in 1939. In 1942 he undertook a 6-week course at the Army Radio School, and immediately afterwards he enlisted in the Army Operational Research Group and commenced work on ways of preventing the jamming of radars.

The German jamming of British and Allied radars—usually from the French coast—had become a serious problem in 1941, when it allowed a couple of German warships, the Scharnhorst and the Gneisenau, to escape unharmed through the English Channel. In early 1942, Hey received reports of severe noise jamming of anti-aircraft radars. After some investigation he realised that the direction of this interference appeared to be following the Sun, and so he suspected that it might be a result of unusual stellar activity rather than Nazi ingenuity.

Hey consulted London’s Royal Observatory and was informed about a very active sunspot (a temporary phenomena of intense magnetic activity, and often dark spots, on the surface of the Sun) traversing the solar disc, emitting powerful streams of energetic ions and electrons. He concluded, correctly, that the Sun was producing metre-wave radiation emissions—and so interfering with the army’s four to eight metre-wave radars.

Hey’s discovery was an important stride forward in the field of radio astronomy—the study of celestial objects at radio frequencies—that had started in the 1930s when Karl Jansky discovered radiation coming from the Milky Way while working for Bell Telephone Laboratories. Now we know that all sorts of objects in space produce radio emissions: from stars to galaxies, from quasars to pulsars. Furthermore, some of the most compelling evidence in favour of Big Bang theory also comes from radio astronomy.

After 1942, Hey was not intentionally involved any further in radio astronomy, however he did continue to use his knowledge of radars to assist in the war effort. In 1945 he used radar to track the approaches of German V2 rockets approaching London, and through studying their echoes he realised that radar could also be used to track meteor streams. After the war, in 1949, he was appointed the head of the Army Operational Research Group.

Photo Credit: TRACE Project, NASA
Photo Caption: Coronal loops burst over a solar active region on the Sun’s surface.