Gustav Andreas Tammann, a prominent scientist, renowned for his fundamental contributions to research in extragalactic astronomy and cosmology, died on 6 January 2019 in Basel, at the age of 86.
He was born in Göttingen on 24 July 1932 as son of the medical professor Heinrich Tammann and his wife Verena (née Bertholet). His paternal grandfather, the chemistry professor Gustav Heinrich Tammann, initially at the University of Dorpat (today’s Tartu) before moving to Göttingen, originated from the Baltic; his maternal grandfather Alfred Bertholet was theology professor in Basel. Gustav Andreas Tammann spent his childhood in Göttingen and Hannover, and in Pomerania and Bavaria during the Second World War. After the death of his father in 1946 his mother returned to her native Basel with him and his two sisters.
G. A. Tammann studied in Basel, Freiburg im Breisgau, and Göttingen. After his graduate studies in Basel he moved to the Mount Wilson and Palomar Observatories in Southern California, before taking up a position as Professor in Hamburg in 1972. Between 1977 and 2002 he was full professor and Head of the Institute of Astronomy at the University of Basel. Throughout his career he was frequently invited as visiting scientist at leading astronomical institutions, for example the Institute of Astronomy in Cambridge, and repeatedly the Carnegie Observatories in Pasadena. He continued his research as emeritus professor for another decade.
His collaboration with Allan Sandage in Pasadena, student and successor of Edwin Hubble, began in 1963. It focused on investigating the expansion of the Universe and the determination of the so-called Hubble constant H0. This research project spanned over 20 years and resulted in an impressive series of publications on the so-called “distance ladder”, from measuring distances to close stellar clusters up to those enabling the determination of the universal cosmic expansion. The results were based on observations of variable stars (Cepheids) and supernovae in far-away galaxies, as well as galaxy distributions.
In the 1980s and 1990s the value of the Hubble constant was heavily contested between two schools (Sandage and Tammann and the group around Gérard de Vaucouleurs), which had independently determined values of 50 - 60 and 80 - 100 km s-1 Mpc-1, respectively. The public debate between Tammann and John Huchra at the 18th Texas Symposium on Relativistic Astrophysics and Cosmology in Chicago in December 1996 remains a vivid memory.
In their publication from 2008 Tammann, Sandage and Reindl obtained a value of (62.3 ± 1.3) km s-1 Mpc-1 for H0. Tammann and Reindl’s last publication in 2013 cited a value of (64.3 ± 3.6) km s-1 Mpc-1. Even today the value of H0 is not fully settled, possibly due to an underestimation of systematic errors. Whereas the latest determination through the distance ladder method by other groups yields (73.2 ± 1.7) km s-1 Mpc-1 (targeting the nearby Universe), the most recent value derived from the measurements of the Planck satellite, based on observations of the cosmic microwave background, is (67.4 ± 0.5) km s-1 Mpc-1. Tammann was a pioneer in utilising supernovae to measure cosmic distances. In visionary publications he predicted their use for cosmology. At present, supernovae are indeed universally employed as the essential ultimate stepping stone of the cosmic distance ladder. With his colleagues he prepared the path toward the discovery of the accelerated expansion of the Universe and enabled the research of the Supernova Cosmology Project and of the High-Z Supernova Search Team that culminated in the 2011 Nobel Prize in Physics awarded to Saul Perlmutter, Brian Schmidt and Adam Riess.
Two books, “A Revised Shapley-Ames Catalog of Bright Galaxies” (with Sandage) and “Halley’s Comet” (with Philippe Véron), as well as his more than 200 scientific publications led to distinctions such as the ‘Karl-Schwarzschild Medaille’, the ‘Einstein Medaille’, and the ‘Tomalla Preis’, to the membership in the Academia Europaea, the Leopoldina, the New York, Austrian and Heidelberg Academies of Sciences as well as the Academy of Naples, that underlined the proficiency of astronomy in Basel. He further contributed his expertise and advice in fulfilling many functions, namely as President of the Commission on Galaxies of the International Astronomical Union and of the ‘Astronomische Gesellschaft’, as member of the Space Telescope Advisory Team of the European Space Agency ESA and of the Council of the European Southern Observatory ESO, as President of the Foundation High Altitude Research Stations Jungfraujoch and Gornergrat and of the Scientific Advisory Committee of the Bernoulli-Edition, and as member of the ‘Euler-Kommission’ of the Swiss Academy of Sciences (then still called ‘Schweizerische Naturforschende Gesellschaft’). With his standing and influence he was instrumental to the decision that Switzerland joined ESO, and moreover to the founding of the International Space Science Institute (ISSI) in Bern.
Tammann was also known to the general public through numerous public lectures, radio broadcasts, and his appearance in movies and on television. Highly impressive was when he compared the expansion of the Universe and the rising distances between galaxies with the growing distances between raisins during the baking of a yeast-based Gugelhupf cake. His enthusiasm, his generous character and noble demeanour, his acumen and esprit won over whoever had met him.
Encounters with him and his charming wife, Yvetta Tammann-Jundt (who passed away before him and whose family history included emigration to wine-growing areas in Bessarabia on the Black Sea as well as the return to Switzerland after the Second World War) were always life-enhancing. Besides his work in astronomy that determined his professional life, he followed up genealogical subjects and built a collection of decorations and medals from around the world (tammann.ch). He is survived by his children Tatjana and Thomas and by five grandchildren.
His students, his colleagues here and abroad will sorely miss this endearing fellow human being.
For his contemporaries, students, and former Basel colleagues:
Iris Zschokke (Basel), Martin Huber (Zürich), Johannes Geiss (Bern); Bruno Binggeli (Basel), Alfred Gautschy (Zürich), Helmut Jerjen (Canberra), Renée Kraan-Korteweg (Cape Town), Bruno Leibundgut (Garching), Anja Schröder (Cape Town); Roland Buser (Basel), Ortwin Gerhard (Garching), Eva Grebel (Heidelberg), and Friedrich Thielemann (Basel and Darmstadt).
[Released: March 2019]