Sjur Refsdal 1935-2009

It is with deep regret the Institute of Theoretical Astrophysics announces the death of Professor Sjur Refsdal on Thursday, the 29th of January, 2009 at the age of 73.

Prof. Refsdal after being awarded the King's Medal of Merit in Gold. Photo: University of Oslo

Sjur was born in Oslo on the 30th of December 1935. He received the master degree from the Physics Department of the University of Oslo in 1962. He was at NORDITA, Copenhagen 1962 – 1963 and held a fellowship at the Institute of Theoretical Astrophysics, University of Oslo 1963 – 1966. From 1967 to 1970 he was associate professor at the University of Nebraska; in 1970 he returned briefly to Oslo to defend the degree of dr. philos. at the University of Oslo. In the same year he was appointed professor at the University of Hamburg, Germany, which became his working place until he retired in 2001.

Throughout his career he kept very close contact with the Institute of Theoretical Astrophysics. He held an adjunct professorship at the Institute from 1991 to 2001. When he retired in Hamburg in 2001, he moved to Oslo and continued working as an emeritus professor at our Institute until the incurable progressive nerve disease that he suffered from in the later years made it impossible for him to get to his office almost two years ago. He was a member of the Norwegian Academy of Science and Letters, and in the academic year 1997/1998 he led (together with Professor Rolf Stabell) a research program at the Centre for Advanced Study at the Norwegian Academy of Science and Letters. In 2005 he was awarded The King's Medal of Merit in Gold.

In the period 1964-1970 Sjur wrote a series of six classical papers on gravitational lensing, really laying the foundation of this field long before the first gravitational lens was found in 1979. Already in 1964 he showed how the gravitational lens effect can be used to determine the expansion rate of the universe (the Hubble constant) and the masses of galaxies. Together with students at the Institute of Theoretical Astrophysics in the mid-1960s he also did pioneering numerical studies of the evolution of cosmological models with a cosmological constant. For several years Sjur worked on the theory of stellar interiors and stellar evolution, especially with colleagues in Hamburg and Oslo, producing many well quoted papers on later stages of stellar evolution. After the discovery of the first gravitational lens in 1979, he was quick back to developing their theory further. Already in the same year, he produced together with his Ph.D. student Kyongae Chang a seminal paper predicting the phenomenon of microlensing, a phenomenon that was observationally confirmed in 1989.

Sjur became a widower when his wife Gunthara died in 1996. He is survived by his two sons Thomas and Gunnar. Our thoughts go to them and to his companion through the last years, Kari-Lise. He also leaves a large number of mountaineering and chess playing friends. At the Institute of Theoretical Astrophysics, Sjur will be remembered not only for being Norway's most quoted astrophysicist, but as much for his kind and unassuming personality. He was also the incarnate absentminded professor. He is deeply missed!

By Per Lilje
Published Aug. 13, 2012 3:53 PM - Last modified Aug. 22, 2012 9:13 AM