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In 2017, gravitational waves and electromagnetic radiation were detected from the merger of two stellar remnants called neutron stars. An observational analysis reveals how this radiation was released from the merger.
Last year, scientists reported the coalescence of two astronomical objects known as neutron stars1. The event, called GW170817, produced gravitational waves, which had weakened to a faint ‘chirp’ by the time they reached us. In addition, some of the matter in the neutron stars was ejected into space. Moments later, this matter was hit by a powerful jet of material from the merged stars, resulting in a roaring outburst of radiation at all wavelengths2. However, despite a flood of data, the process by which this radiation was generated has not been certain. In a paper in Nature, Mooley et al.3 report that GW170817 still whispers to us in radio waves. These signals suggest that the observed radiation came from a relatively slow-moving ‘cocoon’ of matter that was energized by the jet.