Sjur Refsdal
Encyclopedia
Prof Sjur Refsdal 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 PhD
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.
In 1964 and 1966 he published a series of articles on the effects and possible applications of gravitational lenses. 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 quasar
(QSO). 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
.
On February 1, 2005 he was awarded the King's Medal of Merit in gold (Kongens fortjenstmedalje in Norwegian).
He was a member of the Norwegian Academy of Science and Emeritus
at the Institute for theoretical Astrophysics at the University of Oslo
.
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
astrophysicist, born in Oslo
Oslo
Oslo is a municipality, as well as the capital and most populous city in Norway. As a municipality , it was established on 1 January 1838. Founded around 1048 by King Harald III of Norway, the city was largely destroyed by fire in 1624. The city was moved under the reign of Denmark–Norway's King...
. He is best known for his pioneer work on gravitational lensing, including the Chang-Refsdal lens
Chang-Refsdal lens
A Chang-Refsdal lens is a point-mass gravitational lens perturbed by constant external shear.The name derives from Kyongae Chang and Sjur Refsdal who in 1979 published a paper in NATURE 282, 561. "Flux Variations of QSO Q0957+561 A,B and image splitting by stars Near the Light Path."The paper...
.
In 1970 he earned a PhD
Doctor of Philosophy
Doctor of Philosophy, abbreviated as Ph.D., PhD, D.Phil., or DPhil , in English-speaking countries, is a postgraduate academic degree awarded by universities...
at the Institute of Theoretical Astrophysics, University of Oslo
University of Oslo
The University of Oslo , formerly The Royal Frederick University , is the oldest and largest university in Norway, situated in the Norwegian capital of Oslo. The university was founded in 1811 and was modelled after the recently established University of Berlin...
.
Later that year he became professor in astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
at the Hamburg Observatory in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
, 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. 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 quasar
Quasar
A quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...
(QSO). He later started work on stellar evolution, but returned to gravitational lensing shortly before the first detection of a gravitational lens
Gravitational lens
A gravitational lens refers to a distribution of matter between a distant source and an observer, that is capable of bending the light from the source, as it travels towards the observer...
, dubbed the Twin Quasar
Twin Quasar
The Twin Quasar , also known as SBS 0957+561, or TXS 0957+561 , was the first identified gravitationally lensed object.-Quasar:...
.
On February 1, 2005 he was awarded the King's Medal of Merit in gold (Kongens fortjenstmedalje in Norwegian).
He was a member of the Norwegian Academy of Science and Emeritus
Emeritus
Emeritus is a post-positive adjective that is used to designate a retired professor, bishop, or other professional or as a title. The female equivalent emerita is also sometimes used.-History:...
at the Institute for theoretical Astrophysics at the University of Oslo
University of Oslo
The University of Oslo , formerly The Royal Frederick University , is the oldest and largest university in Norway, situated in the Norwegian capital of Oslo. The university was founded in 1811 and was modelled after the recently established University of Berlin...
.
Related Reading
- S.V.H. Haugan, "Separating intrinsic and microlensing variability using parallax measurements".