Sjur Refsdal (30 December 1935 – 29 January 2009) was a Norwegian astrophysicist, born in Oslo. He is best known for his pioneer work on gravitational lensing, including the Chang-Refsdal lens.
In 1970 he earned a doctorate at the Institute of Theoretical Astrophysics, University of Oslo. Later that year he became professor in astrophysics at the Hamburg Observatory[1] in Germany, and remained in that position until he retired in 2001.
In 1964 and 1966 he published a series of articles on the effects and possible applications of gravitational lenses.[2] He is particularly known for the "Refsdal Method", which describes how one may estimate the expansion rate of the Universe (Hubble constant) using the measured time-delay and lens properties of a gravitationally lensed Supernova (SN).[3] This method was applied for the first time in 2018,[4] with the homonymous SN Refsdal. He later started work on stellar evolution, but returned to gravitational lensing shortly before the first detection of a gravitational lens, dubbed the Twin Quasar.
He was a member of the Norwegian Academy of Science and Emeritus at the Institute for theoretical Astrophysics at the University of Oslo.[5] On 1 February 2005 he was awarded the King's Medal of Merit in gold.
The first detected multiply-lensed supernova was nicknamed "SN Refsdal" in his honor.[6][7]