Einstein has passed his toughest test yet: his theory of general relativity holds up even in the extreme conditions surrounding a pair of pulsars.
鈥淚f general relativity does break down, we believe it will be in regions of very strong gravity,鈥� 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鈥檚 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. 鈥淲e can trace the paths of both members of the pair accurately,鈥� says Kramer. 鈥淚t鈥檚 a unique situation.鈥�
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General relativity predicts that the pulsars鈥� 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鈥� worth of data and found that observations matched predictions to within 0.05 per cent (Science, DOI: 1/10.1126/science.1132305).
