Neutron are fascinating objects to study. They lie at the interface of the four fundamental interactions. For instance pulsars emit electromagnetic radiation, magnetars display an extreme magnetic field, oscillation of magnetic fields in ‘standard’ neutron stars seem to be in relation with Quasi Periodic Oscillation observed.
Their inner structure is neutron rich, and is described by nuclear physics at high density, and a superfluid phase is believed to be present in the interior of the star. Cold stars are in beta equilibrium, i.e. deal with the weak interaction, that is responsible for the fact that neutron are mostly present in the star. Gravity holds the star together and the extreme mass and high compactness of the star makes them objects probing strong gravitational fields. Their complexity makes them incredibly hard to study precisely; but also seed the prospect of impactant findings about the nature of matter, and spacetime.