It is my understanding that when an electron drops to a lower orbital that 2 photons of light are produced. The moving electric charge produces EM radiation just like moving charges in a radio transmitters antenna produce EM radiation. Energy in the form of radiation, heat, or whatever else, can bump electrons up into higher orbitals, preparing them to drop again and emit more photons. If all the matter in a neutron star is neutrons then there are no charged particles. None of the neutron matter should emit, absorb, or interact with EM radiation, so how can such a star shine?