Giacconi, Riccardo (1931-2018), was an Italian-born American physicist. He won a share of the 2002 Nobel Prize in physics for work that led to the discovery of sources of X rays in space. The prize was also awarded to the American physical chemist Raymond Davis, Jr., and the Japanese physicist Masatoshi Koshiba.
Earth’s atmosphere absorbs X rays from space, so X-ray detectors must be carried above the atmosphere. In 1949, scientists used instruments mounted on rockets to detect X rays in space for the first time. Those rays originated on the sun. In the 1960’s, Giacconi and other researchers used rockets to detect X rays from the sun and other stars. The rockets also found a background of X rays evenly distributed across the sky. But, because the rockets did not go into orbit, their observing time was limited to a few minutes per launch.
Experiments with detectors carried into space by balloons lasted longer but did not go as high. Furthermore, those detectors were not highly sensitive. Cosmic sources emit (send out) X rays that have different amounts of energy. Because of their altitude, the balloon-borne detectors were sensitive to energies at which many sources emit relatively few rays.
To overcome limitations of detectors carried by rockets and balloons, Giacconi led in the construction of three X-ray satellites. The first, called Uhuru, was launched in 1970. The more powerful Einstein X-ray Observatory went into orbit in 1978, and the even more powerful Chandra X-ray Observatory was launched in 1999.
Riccardo Giacconi was born in Genoa, Italy, on Oct. 6, 1931. In 1954, he received a Ph.D. degree in cosmic ray physics from the University of Milan. In 1959, he joined American Science and Engineering (AS&E), a company then located in Cambridge, Massachusetts. He became a United States citizen in 1967.
In 1973, Giacconi and several members of his research group moved from AS&E to Harvard University. Giacconi became associate director for high energy astrophysics at the Harvard-Smithsonian Center for Astrophysics in Cambridge in 1976. In 1981, he was named the first director of the Space Telescope Science Institute, which conducts research using the Hubble Space Telescope.
In I982, Giacconi joined the faculty of Johns Hopkins University in Baltimore, Maryland, as a professor of physics and astronomy. In 1993, he became director general of the European Southern Observatory (ESO), an organization of several nations. The ESO is based in Garching, near Munich, Germany, and operates observatories in Chile. Giacconi became a research professor at Johns Hopkins University in 1998. In 1999, he was named president of Associated Universities, Inc., an association of United States universities that operates the National Radio Astronomy Observatory. He died on Dec. 9, 2018.
