Riccardo Giacconi (1931-2018) Astronomer Who Opened the X-Ray Window Onto the Universe

COMMENT OBITUARY Riccardo Giacconi (1931-2018) Astronomer who opened the X-ray window onto the Universe.

evolutionary discoveries in astron- Giacconi led the opening up of space obser- omy stem from new observing tech- vatories to general use — not just by special- nologies. And so it was with orbiting ist operating teams — and the establishment RX-ray telescopes. They revealed a Universe of calibrated data archives. Such archives are dominated by luminous, gravity-fed black now widely implemented by NASA, and are BETTMANN/GETTY holes and plasmas glowing at tens of mil- gaining ground in the new generation of large, lions of degrees, inside clusters of galaxies. ground-based observatories. As a result, more Now 60 years old, the discipline requires astronomers are embracing multi-wavelength space observatories — outside Earth’s X-ray- observations, from radio to X-rays. Archival blocking atmosphere — and new, specialized data get re-used, increasing their discovery optics and detectors. For pioneering these, potential with time (a typical Chandra data Riccardo Giacconi won the 2002 Nobel Prize set is re-published about six times). This in Physics. openness has catalysed a better understand- Giacconi shaped the tools and culture of ing of the Universe and its evolution. modern astronomy, which centres on large In 1981, Giacconi became the first facilities that serve the community. He real- director of the Space Telescope Science Insti- ized the importance of catering to the entire tute (STScI) at the Johns Hopkins Univer- observatory life cycle, across the electro- sity in Baltimore, Maryland, which operates magnetic spectrum — from conception to NASA’s Hubble Space Telescope. His man- hardware implementation and operations, agement style, developed during his AS&E including calibrations, software pipelines, of X-ray observatories. The first, NASA’s years, shaped the STScI into one of the pre- data archives and software tools for users. He Small Astronomy Satellite 1, was launched mier astronomy centres worldwide. He took championed scientific leadership and man- from the Italian San Marco platform off the same tack when he became director- agement, and integrated teams, with mem- the coast of Kenya, on 12 December 1970 general of the European Southern Observa- bers doing both technical work and research. — Kenya’s independence day — and was tory (ESO) in Garching, Germany, in 1992. His approach is now integral to all major renamed Uhuru, Swahili for ‘freedom’. At the ESO, he oversaw the development of international observatories. One result is the Uhuru performed the first X-ray survey the highly successful Very Large Telescope adoption of data interoperability standards of the entire sky. It led to the discovery of in Chile, and was involved in the early devel- for astronomy, developed by the International accreting neutron-star and black-hole opment of the revolutionary Atacama Large Virtual Observatory Alliance since 2002. sources in binary stars, X-ray emission from Millimeter/submillimeter Array (ALMA). Giacconi died on 9 December 2018 in San supernova remnants, active galactic nuclei He continued to oversee ALMA, together Diego, California, aged 87. He was born in and hot haloes in clusters. with other major US radio telescopes, during Genoa, Italy, in 1931. His mother, who taught In 1973, Giacconi and his group moved his five-year tenure as president of Associ- in a secondary school and wrote mathematics to the Harvard-Smithsonian Center for ated Universities, Inc., which started in 1999. textbooks, spurred him to excel. In 1956, with Astrophysics. Here, he led the collaboration Science was Giacconi’s driving force. His a doctorate on cosmic-ray detection from the that built and operated the first imaging professional, social and family lives were often University of Milan, he moved to the United X-ray telescope, the Einstein Observatory. intertwined, with friends and engagements States, as a Fulbright fellow at Indiana Univer- This detected X-rays from almost all types worldwide. Architecture and art were impor- sity Bloomington and later became a research of object in the cosmos, establishing the tant to him: he enjoyed copying Renaissance associate at Princeton University in New Jer- technique as a branch of astronomy. paintings, with which he decorated his home. sey. In 1959, Giacconi joined the Massachu- Understanding the X-ray background He could be blunt and push controversial setts Institute of Technology (MIT) spin-off drove Giacconi. It led him to pursue ideas, but he appreciated a vigorous discus- company American Science & Engineering telescopes with increasingly higher image sion. I remember his disappointment during (AS&E), then in Cambridge. resolution — notably, the Chandra X-ray the Harvard years that people did not argue Here, with Bruno Rossi of MIT and other Observatory, NASA’s flagship mission with him any more. As Giacconi wrote in AS&E physicists, Giacconi conducted a launched on the Space Shuttle Columbia in his autobiography, Secrets of the Hoary Deep series of experiments on the detection of July 1999. Thanks to Chandra, we know that (2008), he needed to explore uncharted seas. X-rays from space. In 1962, with Geiger this background is mostly due to giant black He opened new realms to discovery. ■ counters flown on an Aerobee rocket from holes with masses up to one billion times that the US White Sands Missile Range in New of the Sun, swallowing gas clouds and stars. Giuseppina Fabbiano is senior Mexico, Giacconi and his collaborators Early X-ray observations presented a whole astrophysicist at the Center for Astrophysics discovered the first celestial X-ray source new set of phenomena. They showed that, in | Harvard & Smithsonian, and head of (Sco X-1). It was later identified as a neutron some cases, the energy produced by celestial the Chandra X-ray Center Data Systems star that was accreting matter from a low- bodies is more than can be observed in visual Division. She met Giacconi in the early 1970s, mass star companion. The team also detected light. These findings underpin the present while working on Uhuru data for her doctoral a pervasive celestial X-ray background. understanding of the evolution of binary thesis. In 1975, she joined his High Energy These discoveries spurred Giacconi’s stars, galaxies and the giant black holes at Division of the Center for Astrophysics. proposal to NASA for a strategic programme their centres, and of the Universe at large. e-mail: [email protected]