Neutron stars may be bigger than expected, measurement of lead nucleus suggests Apr. 27, 2021 , 11:00 AM Say what you want about lead, it’s got a surprisingly thick skin—of neutrons, that is. In fact, the layer of neutrons on the outside of a lead nucleus is twice as thick as physicists thought, according to a new study. The seemingly abstruse result could have out-of-this-world implications: Neutron stars, the ultradense spheres left behind when stars explode in supernova explosions, could be stiffer and bigger than theory generally predicts. “It’s a fantastic experimental achievement,” says Anna Watts, an astrophysicist at the University of Amsterdam who studies neutron stars. “It’s been talked about for years and years and years, and it’s so cool to finally see it done.”