Tests of Einstein's general theory of relativity in a strong gravitational field may be best conducted in systems containing black holes. Such a test in a close binary system of two proposed black holes in the quasar OJ287 is reported. This quasar shows quasi-periodic optical outbursts at 12 year intervals, with two outburst peaks per interval. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black hole model and the general relativity.
- M. J. Valtonen
- H. J. Lehto
- S. Dogru
