Neutron stars are the densest celestial objects after black holes. But unlike black holes, some neutron stars emit beams of radiation out of their magnetic poles, producing a “lighthouse” effect as they rotate. By recording the flashes from these so-called pulsars, giant radio telescopes can infer physical properties of neutron stars [1]. For nearly two decades, Michael Kramer from the Max Planck Institute for Radio Astronomy, Germany, and his collaborators have monitored the double pulsar PSR J0737–3039A/B, a unique system composed of two pulsars in orbit around each other. The team has now released 16 years’ worth of their data [2]. The gravity community has long awaited this update, as an earlier study—based on just 2.5 years of data—showed that the pulsar pair is an excellent testbed for strong-field gravity [3]. The new extended dataset does not disappoint: It not only improves the precision of previous gravity tests by orders of magnitude, but it also enables a few new ones. Einstein’s general relativity passes all these challenges with flying colors.
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