2008 Astrophysics Citation
|The Norwegian Academy of Science and Letters awards the
2008 Kavli Prize in Astrophysics to:
Emeritus Professor of Astronomy
California Institute of Technology, USA
Institute of Astronomy, Cambridge University, UK
|“for their seminal contributions to understanding the nature of quasars”|
In 1963, Maarten Schmidt unlocked the gate to the far reaches of the Universe by correctly identifying emission lines in the optical spectrum of a radio “star” known as 3C273. That insight immediately showed that 3C273 is an extremely luminous, very distant object rather than a star in our own Galaxy. Objects like 3C273 are now known as quasars. Schmidt’s breakthrough interpretation of the spectrum of 3C273 followed essential work by radio astronomers, who discovered quasars by their radio wave emission and measured their positions on the sky.
Schmidt extended his discovery by finding quasars even more distant than 3C273 and showing that quasars were much more numerous when the Universe was young. Schmidt also devised powerful statistical techniques to measure the luminosity and space density evolution of quasars.
The extraordinary power emitted by quasars requires an extraordinary engine. Various proposals for the nature of the quasar engine were advanced in the years following Schmidt’s discovery. The watershed in our theoretical understanding of the nature of quasars was Donald Lynden-Bell’s investigation in 1969 of the hypothesis that quasars were powered by gravity, through the accretion of material onto massive black holes.
Although others had suggested that quasars were powered by black hole accretion, Lynden-Bell argued persuasively that most of their luminosity comes from frictional heating in a rotating gaseous disk (the “accretion disk”); developed an approximate model for their spectrum; and suggested that these black holes are to be found in the centers of galaxies. He also pointed out that many nearby galaxies should contain black holes at their centers that do not currently shine (“dead quasars”) and that these could be detected by their gravitational influence on stars orbiting nearby, a prediction that has been observationally confirmed.
Maarten Schmidt’s and Donald Lynden-Bell’s seminal work dramatically expanded the scale of the observable Universe and led to our present view of a violent Universe in which massive black holes play a key role.