The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low3-7, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).
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Acknowledgements We thank J. Reynolds of the Parkes Observatory, and B. Sault of the ATCA, for prompt allocations of observing time. The Parkes Observatory and the ATCA are part of the Australia Telescope, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. M.B., N. D’A. and A.P. acknowledge financial support from the Italian Ministry of University and Research (MIUR) under the national programme ‘Cofin 2001’. V.K. acknowledges partial support by a David and Lucile Packard Science and Engineering Fellowship and a NSF Gravitational Physics grant. D.R.L. is a University Research fellow funded by the Royal Society.