Professor Adriaan Blaauw, one of the most influential astronomers of the twentieth century, passed away on 1 December 2010.
Adriaan Blaauw was born in Amsterdam, the Netherlands, on 12 April 1914. He studied astronomy at Leiden University, under de Sitter, Hertzsprung and Oort, and obtained his doctorate (cum laude) with van Rhijn at the Kapteyn Laboratory in Groningen in 1946, on a PhD thesis entitled: A study of the Scorpio–Centaurus Cluster. In this work he used the proper motions of the stars on the sky, deduced by very careful comparison of position measurements taken more than 50 years apart, and demonstrated that most of the bright hot O and B stars in the constellations Scorpius and Centaurus have nearly identical space motions and hence constitute a physical group of stars. This work laid the basis for a career of groundbreaking studies of the properties of these OB associations which still contain the fossil imprint of their star formation history. Perhaps Blaauw’s most famous work explained why some OB stars are found in isolation and are traveling unusually rapidly: the so-called run-away stars. During his time at Yerkes, he and Morgan had discovered curious examples such as the OB stars μ Columbae and AE Aurigae which are moving very fast in opposite directions, putting both of them at the location of the Orion Nebula at approximately the same time, 2.6 million years earlier. Blaauw proposed in 1961 that run-away stars had originally been members of binary stars, and when one star in the binary experiences a supernova explosion, its companion suddenly ceases to feel the gravitational pull that keeps it in its orbit and hence it “runs away” at its orbital velocity and rapidly leaves the group it was born in.
In addition to his distinguished research career, Blaauw played a decisive role in the creation of the intergovernmental European Organization for Astronomical Research in the Southern Hemisphere, often referred to as the European Southern Observatory, or simply as ESO. In 1953, Baade and Oort proposed the idea of combining European resources to create an astronomical research organisation that could compete in the international arena. Blaauw had returned to Leiden in 1948 at Oort’s invitation, had moved to Yerkes Observatory in 1953, becoming its associate director in 1956, and moved back to Groningen in 1957, where he revitalized the institute and initiated a new program in radio astronomy together with van Woerden. Here he was also in a key position to contribute to transforming the idea of Baade and Oort into reality. He was Secretary of the ESO Committee (the proto ESO Council) from 1959 through 1963, a period which included the signing of the ESO Convention on 5 October 1962 by the five founding Member States Belgium, France, Germany, the Netherlands and Sweden. Blaauw became ESO’s Scientific Director in 1968. In this position he also provided the decisive push to combine the various national journals for astronomy into Astronomy and Astrophysics, which today is one of the leading astronomy research publications in the world.
Blaauw succeeded Heckman as Director General of ESO in 1970, for a five-year term. During this period several telescopes including the ESO 0.5-meter and 1-meter Schmidt telescopes began operating at ESO’s first observatory site, La Silla, in Chile, and much work was done on the design and construction of the ESO 3.6-meter telescope, which saw first light in 1976. Blaauw decided that it was crucial for this challenging project to move ESO’s Headquarters and the Technical Department from Hamburg to Geneva, to benefit from the presence of the experienced CERN engineering group.
After his ESO period, Blaauw returned to Leiden, where he continued to play a very important role in international astronomy. He was President of the International Astronomical Union from 1976 to 1979. During his tenure he used his considerable diplomatic skills to convince China to rejoin the IAU even though Taiwan was also a member. He retired from his Leiden professorship in 1981 and moved back to Groningen, but stayed active in various areas. He organized the historical archives of ESO and of the IAU — a work which resulted in two books, ESO’s Early History and History of the IAU. He also served as Chairman of the Scientific Evaluation Committee for the European Space Agency satellite HIPPARCOS, which would measure the proper motions of the 100,000 brightest stars with unprecedented accuracy, and advised on many aspects of its scientific programme. When the data became available in 1996, he was actively involved in the re-analysis of the young stellar groups he had studied during his PhD research, more than fifty years earlier.
Blaauw remained keenly interested in developments at ESO. He drove himself from Groningen to Garching and back for a two-day stay in July 2009 in order to take another look at the historical documents in the ESO library. He visited Chile in February 2010 during which he was driven to La Silla and then Paranal by car to enjoy Chile’s beautiful landscapes and ‘inspect’ the telescopes on both these sites. He actively engaged young people in interesting discussions and throughout the visit displayed a crystal clear perspective on the development of astronomy in general and of ESO’s program in particular, including the exciting opportunities for the future. The characteristic twinkle in his eye was as bright as always.
Blaauw won many academic distinctions, including membership in many academies of science, honorary doctorates from the University of Besancon and from l’Observatoire de Paris and the Bruce Medal of the Astronomical Society of the Pacific. He was well-known for his warm personality, wisdom, humour, legendary patience, and the very rare gift of being able to slow down when the pressure mounts. The personal account of his life entitled My Cruise Through the World of Astronomy, published in the 2004 Annual Reviews of Astronomy and Astrophysics, provides an accurate and inspiring picture of a truly remarkable person, who positively influenced the lives of many others.