American radio engineer Karl Jansky (1905–1950) constructed the first radio telescope and founded the field of radio astronomy almost by accident. An employee of Bell Laboratories in New Jersey, Jansky was assigned the task of locating the source of radio interference that was disrupting radio-calls across the Atlantic Ocean. Jansky constructed a radio antenna from wood and brass to detect radio signals at a specific frequency. He found signals coming from three sources: two were thunderstorms, but the third was a mystery that produced a steady hiss. Jansky eventually realized that the signal was being produced by interstellar gas and dust in the Milky Way galaxy. He also observed that the signal was strongest in the direction of the constellation Sagittarius, where we now know the center of the galaxy is located.

In 1932 Jansky’s discovery of radio waves from space was announced. The news inspired another American radio engineer, Grote Reber (1911–2002), who proceeded to build his own radio telescope in 1937. For the next decade, Reber studied the radio waves coming from space, creating a map of the radio signals coming from our galaxy. His work showed that most of the radio waves in our galaxy are produced not by stars, but by clouds of hydrogen-rich interstellar gas. Reber’s findings, published under the title “Cosmic Static” in The Astrophysical Journal, paved the way for a great boom in radio astronomy following the end of World War II in 1945.