Giacconi, Riccardo, 1931–, Italian-American astrophysicist, b. Milan, Italy, Ph.D. Univ. of Milan 1954. He was a researcher at American Science and Engineering Corporation (1959–73), professor at Harvard (1973–81), director of the Space Telescope Science Institute, Johns Hopkins (1981–92), director general of the European Southern Observatory in Germany (1992–99), and president of Associated Universities, Inc. (1999–2004). In 2004, he was appointed professor at Johns Hopkins. Giacconi was co-recipient, with Masatoshi Koshiba and Raymond Davis, of the 2002 Nobel Prize in Physics for pioneering contributions to astrophysics. Giacconi discovered X-ray sources outside the solar system, including background X-radiation and black holes; his discoveres and work on instruments that identified those discoveries laid the foundations for the field of X-ray astronomy.