Wednesday, April 16, 2008

Quasar Tests General Relativity to the Limit

Wow. This is a rather impressive piece of work in terms of prediction and subsequent measurement. A group of astronomers have made what appears to be the most compelling evidence of the validity of General Relativity (GR) in strong gravitational field, and in the process, produced a more direct evidence of the existence of black holes, and an indirect evidence for gravitational waves.

The quasar pulse occurred right on schedule, strongly suggesting that OJ287 is a binary black hole system (Nature 452 851). In addition to verifying the enormous mass of the primary black hole, the result shows that the orbit of the secondary black hole precesses at a rate of 39 degrees per period. For comparison, the distorting effect of the Sun on the local space–time causes Mercury's orbit to precess by little more than 0.1 degrees per century.

Furthermore, the work suggests that the binary system is losing energy by emitting gravitational waves — a key prediction of Einstein's theory that is yet to be verified directly. When this emission is not included in the model, the quasar outburst is predicted to occur 20 days later, providing indirect support for gravitational waves.



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