A massive binary black-hole system in OJ 287 and a test of general relativity

TLDR: The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system.

Abstract: Black holes are firmly established in astronomy and in the public imagination. Yet the concept still depends on the assumption that Einstein's general theory of relativity is the correct theory of gravitation. Tests of general relativity in a strong gravitational field are best conducted in systems containing black holes. Valtonen et al. report such a test in a close binary system of two proposed black holes in the quasar OJ 287. This quasar shows quasiperiodic optical outbursts at 12-year intervals, with two outburst peaks per interval. The latest outburst in September 2007 was within a day of the time predicted by the binary black hole model and general relativity. 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. Tests of Einstein’s general theory of relativity have mostly been carried out in weak gravitational fields where the space-time curvature effects are first-order deviations from Newton’s theory1,2,3,4,5,6. Binary pulsars4 provide a means of probing the strong gravitational field around a neutron star, but strong-field effects may be best tested in systems containing black holes7,8. Here we report such a test in a close binary system of two candidate black holes in the quasar OJ 287. This quasar shows quasi-periodic optical outbursts at 12-year intervals, with two outburst peaks per interval9,10. The latest outburst occurred in September 2007, within a day of the time predicted by the binary black-hole model and general relativity11. The observations confirm the binary nature of the system and also provide evidence for the loss of orbital energy in agreement (within 10 per cent) with the emission of gravitational waves from the system12. In the absence of gravitational wave emission the outburst would have happened 20 days later13.