What a millisecond pulsar's X-ray hotspots reveal about neutron star size

Astronomers combined sharp X-ray images and polarization measurements from two space telescopes (NICER and IXPE) to map the glowing hotspots on a rapidly spinning neutron star. The pulsar's dual hotspots—one near each pole—suggest a massive, large neutron star, though many parameters sit at the edge of what the model can explain. The mismatch suggests their current picture of how these objects emit light is incomplete.