Sizing Up the Most Massive Neutron Star April 29, 2021• Physics 14, 64 A satellite experiment has revealed that the heaviest known neutron star is unexpectedly large, which suggests that the matter in the star’s inner core is less “squeezable” than some models predict. Goddard Space Flight Center NICER measures the size of a neutron star by tracking the x-ray emission from “hot spots” on the surface as the star rotates. These spots occur at the magnetic poles of the star, where the field slams particles onto the star surface. Goddard Space Flight Center NICER measures the size of a neutron star by tracking the x-ray emission from “hot spots” on the surface as the star rotates. These spots occur at the magnetic poles of the star, where the field slams particles onto the star surface.×