Prof. Roy Kerr (University of Canterbury, New Zealand)

Quasars, Black Holes and the Kerr Metric - Prof. Roy Kerr Colloquium

ATNF Marsfield Lecture Theatre

Abstract

Once powerful radio telescopes became available in the 1950‘s it was realised that the sky was full of objects emitting very intense radio waves but with no known associated optical counterparts. Because of the way that their intensities were changing rapidly they had to be very small and so they were called quasi-stellar radio sources, or Quasars. In 1962 it was shown that they are inside distant galaxies and therefore that the energy being emitted is truly enormous.

In 1963 a meeting of over 300 astronomers and their theoretical colleagues, both astrophysicists and general relativists, was organised in Dallas to try to find an explanation for these quasars. I gave the only talk by a relativist, "Gravitational collapse and rotation". The mathematical solution for the gravitational field outside a non-rotating spherical star had been constructed by Schwarzschild soon after Einstein's original paper on General Relativity. This has the strange property that if the star collapses inside its "Schwarzschild radius", then it is lost forever. It was conjectured by most that if the star were spinning then this would not happen and so "Black Holes" were considered science fiction. In my Dallas talk I gave a mathematical solution for a spinning star, something that theorists had been hunting for 40+ years, and showed that the spin of the collapsing star would not stop a black hole forming.

At that time the astronomers ignored this paper completely but it is now believed that there is a supermassive black hole inside the center of most if not all galaxies and that the most violent events in the universe are associated with accretion disks around these or with the collapse of massive stars to neutron stars (Super-Novae) or even black holes (GRBs). In this talk I will tell the story of the discovery of this solution and of its application to these colossal events.