And actually, now you've got me thinking about this, it occurs to me there should be a dramatic difference in internal structure between a superconducting and not neutron star. (Which the papers so far cited on this topic do not mention at all...) Let me explain. Assume that the interior is made of neutrons which are polluted to some extent by proton-electron mixture. Now here is the thing: protons are heavier and denser than electrons. Therefore, we would expect the protons to sink toward the center, while the electrons rise toward the outside. Which means, after that happens, there should be a very large static radial ELECTRIC field pointing out of the core, within the neutron star. The thing is a big capacitor. If there is no superconductivity, this seems to be something about which there should be no controversy. However, electric field is not possible inside a superconductor (whether type II or type I). So what do you physicists conclude from that? Crikey. The analogue in lab-accessible kinds of matter would be, I guess, if you had a bar of superconducting metal, and then you applied a magical force (analogue of gravity) to the electrons and nuclei inside, pulling them toward opposite ends of the bar. And then as a thought experiment (since there is no such magic force available) you ask "what would happen then?" My top guess, actually, is this would yield a state of matter that I think nobody has ever seen or conceived of before, namely: a superconductor containing a macroscopic permanent internal electric field. What. The. Hell. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)