Einstein has passed his toughest test yet: his theory of general relativity holds up even in the extreme conditions surrounding a pair of pulsars.
“If general relativity does break down, we believe it will be in regions of very strong gravity,” says Michael Kramer of the Jodrell Bank Observatory in Macclesfield, UK. Pulsars, which are dense neutron stars, create massive gravitational fields, and their beacon-like radio emissions can be tracked from Earth.
Until now, only binary systems containing a pulsar and an unseen companion had been studied. Kramer’s team looked at a double pulsar system known as PSR J0737-3039A/B, which lies 2000 light years away in the direction of the constellation Puppis. “We can trace the paths of both members of the pair accurately,” says Kramer. “It’s a unique situation.”
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General relativity predicts that the pulsars’ elliptical orbits around each other should precess, meaning the direction of the long axis of the ellipse should shift, just as that of Mercury does in its orbit around the sun. The team analysed two and a half years’ worth of data and found that observations matched predictions to within 0.05 per cent (Science, DOI: 1/10.1126/science.1132305).
