Pulsars in binaries allow us to estimate their masses via pulse timing orbits. Figure Masses of neutron stars. Neutron stars are supported by the neutron degenerate pressure . However, uncertainties remain because there is little laboratory data on the behaviors of nucleons under such extreme circumstances. Thus, the precise equation of state of neutron star matter is not known.
Neutron stars have a solid crust, and a superfluid core.
Figure The glitches of the Vela Pulsar. Because neutron stars are much smaller even than white dwarfs, their surface thermal emissions are often hard to detect. Only a handful have been detected in the X-rays, and even fewer in the optical. In these systems, the magnetic field has more energy even than the spin energy, and may result in unique phenomena not seen in ordinary neutron stars. Using the Arecibo 305m antenna, Russell Hulse and Joseph Taylor discovered a 59 millisecond pulsar in 1974.