Intense bursts of solar radio emission were first recognized by Second World War British and Australian coastal radar systems as well as by German and Japanese radar systems. Due to wartime security, these discoveries were not declassified until after the end of hostilities but, before declassification, Grote Reber, working alone in his mother’s backyard, reported receiving surprising strong radio emission from the Sun, well in excess of the expected emission from the 5,000 K solar surface. In 1946, while demonstrating his equipment to government representatives, Reber rediscovered solar radio storms when his chart recorder went off scale. Following World War II, with rapidly improving instrumentation, the Sun became a major target in the emerging field of radio astronomy. Observations with instruments of increasing sophistication have traced the complex time, frequency, and spatial dependence of the solar radio emission which corresponded to a wide variety of emission mechanisms. Later, following a false start due to using incorrect positions, radio emission was also detected from a variety of stars in our Galaxy, opening up the new field of stellar radio astronomy.

Karl Jansky’s illness led to his being assigned to a remote New Jersey Bell Telephone Labs site to investigate interference to transatlantic telephone circuits. In a series of personal letters written to his father, Jansky documented his two-year investigation leading to the discovery of radio emission from the center of the Milky Way. Pressure to work on defense-related projects and the growing tensions between Jansky and his supervisor Harold Friis led to a long-standing controversy about why Jansky did not continue his study of “star noise.” Although the astronomical community showed little interest in Jansky’s discovery, Grote Reber, a young engineer and avid radio amateur, built the world’s first radio telescope using his own private funds. After negative results because he was misled by the then prevailing theories of cosmic radio emission, Reber finally confirmed Jansky’s discovery and demonstrated that, unlike all previously known cosmic radiation, galactic radio emission was nonthermal. The work of Jansky and Reber set the stage for the later series of remarkable radio astronomy discoveries made possible by the wartime developments in radio and radar technology.