Bengt Strömgren: Interstellar Glow, Helium Content, and Solar Life Supply, 1932–1940


* The Steno Institute, University of Aarhus, Ny Munkegade, Building 1521, DK-8000 Aarhus C, Denmark. E-mail:


Abstract This paper examines a significant period in the career of the Danish astronomer and astrophysicist, Bengt G. D. Strömgren (1908–1987), in particular, it focuses on his time spent at the University of Chicago and at the Yerkes Observatory in Wisconsin between 1936 and 1938 and his subsequent return to Denmark in the spring of 1938. The years from 1932 to 1940 were a verdant time for new theories of chemical composition in stellar interiors, of nuclear energy production in stars, and of interstellar hydrogen glow (HII regions/Strömgren Spheres), and Strömgren was actively involved in, if not initiating, much of this research. This paper looks at Strömgren’s scientific contributions and aims to provide an insight into the relative states of US and European astronomy at the time by examining the intellectual and social development of astrophysics as Strömgren both experienced it and helped to make it happen in the eight pre-war years.1 My analysis of this phase in Strömgren’s life, both at the University of Copenhagen and the University of Chicago, is based upon newly uncovered archival materials from both sites.2 Strömgren’s interaction with scientific figures such as Otto Struve, George Gamow, Subrahmanyan Chandrasekhar, Hans Bethe, and von Weizsäcker also helps to highlight the significance of this period.