In 1964 and 1966 he published a series of articles on the effects and possible applications of gravitational lenses. 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 in
Germany, and remained in that position until he retired in 2001. 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. On 16 February 2005, he was awarded the
King's Medal of Merit in Gold. 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). This method was applied for the first time in 2018, with the homonymous
SN Refsdal, nicknamed in his honor. == References ==