Allan Rex Sandage

1926-

American astronomer who was a pioneer in radio astronomy and who, in 1961, discovered quasars (quasi-stellar radio sources).

Located billions of light-years away, quasars are sources of radio waves, the first radio source discovered beyond the solar system. Quasars are thought to be early stages in the formation of galaxies. He also helped refine the method of measuring astronomical distances, studied the evolution of stars, and related the age of stars to their color.