AlbaNova and Nordita Colloquium
Mauri Valtonen (Tuorla Observatory, University of Turku and Helsinki Institute of Physics)
FR4 Oskar Kleins Auditorium
Thursday 25 March
15:00 - 16:00
One of the most extreme predictions of General Relativity is the existence of a physical singularity, a black hole. Does it really exist? It is not enough to find a compact dark body in space, such as the over 3 million solar mass body in the Galactic centre, but one must also demonstrate that it satisfies the no-hair theorems of black holes (Israel, Carter, Hawking). Thorne (1980) suggested a simple way to prove the theorems in a binary system: determine the mass, spin and the quadrupole moment of the suspected black hole. For a real black hole these quantities are connected to each other in a definite way which is different from neutron stars or other material bodies. The first test of the no-hair theorems using the binary black hole system in OJ287 has now been carried out. We will describe this system, the current level of the test and possibilities of improving the error limits in future. References: Valtonen et al. ApJ 709, 725 (2010), CeMDA 106, 235 (2010).