Riccardo Giacconi
1931–2018, Genoa, Italy, San Diego, California, United States
Italian-American physicist, 'father of X-ray astronomy' — he discovered the first cosmic X-ray source and the extragalactic X-ray background.
Giacconi earned his physics doctorate in Milan in 1954 and moved to the US in 1956, working at Indiana and Princeton before joining American Science and Engineering in 1959 — where he led the X-ray astronomy program.
In 1962 his rocket detected Sco X-1, the first X-ray source beyond the Sun, along with a diffuse X-ray background. He went on to lead the Uhuru satellite (1970), the Einstein Observatory (1978), then served as first director of the Space Telescope Science Institute operating Hubble (1981), and as ESO director building the VLT. He received the 2002 Nobel Prize.
Nobel-winning work
Cosmic X-rays are fully absorbed by the atmosphere, so detectors must fly above it. On 12 June 1962, Giacconi, Gursky, Paolini and Rossi launched an Aerobee rocket carrying three Geiger counters on an 80-second suborbital flight — and recorded a blazing X-ray source in Scorpius (Sco X-1) plus a uniform X-ray glow from all directions.
The result, published in Physical Review Letters, opened X-ray astronomy: the sources turned out to be neutron stars and black holes devouring matter; the diffuse background is the sum of countless distant supermassive black holes. From Uhuru to Einstein, Chandra and XMM-Newton, the entire science of the 'hot universe' descends from those five minutes of flight. The 2002 Nobel honored 'pioneering contributions to astrophysics, which have led to the discovery of cosmic X-ray sources'.
Workplaces: Johns Hopkins University, Space Telescope Science Institute
Italy, United States