Many neutron star properties are closely related to the structure of neutron rich nuclei. We construct data to data relationships between nuclear and neutron star quantities using relativistic effective field theories. Here, the common unknown is the equation of state (pressure versus density) for neutron rich matter.
We review the parity radius experiment at Jefferson Laboratory that aims to measure the neutron radius of 208Pb, accurately and model independently, via parity violating electron scattering. This measurement has implications for atomic parity violation experiments, the structure of neutron rich nuclei, and neutron stars.
The transition density in a star, from solid crust to liquid interior, can be inferred from an accurate measurement of the neutron skin thickness of a heavy nucleus. Both the star crust and the skin of a nucleus are made of neutron rich matter at somewhat below nuclear density. The thicker the skin in Pb, the lower the predicted transition density from crust to liquid interior.
The skin thickness in Pb constrains the density dependence of the symmetry energy. This is important for neutron star cooling calculations. If the rms neutron minus proton radius in Pb is measured to be below 0.2 Fm, the proton fraction in dense matter is, very likely, too small to allow direct URCA cooling. Alternatively if the skin thickness is above 0.25 fm, direct URCA cooling is very likely.