According to this Neutron Stars start out composed of the same material as White Dwarves, combinations of Helium, Oxygen, Carbon, Neon, Magnesium, and possibly Iron before undergoing gravitational collapse. What I'm curious about and can't seem to find information about is what happens to Neutron Stars when they get old. Are Neutron Stars:
- Completely stable once created, barring catastrophic external influences, like running into another star.
- Subject to some form of "evaporation" slowly decompressing into their pre-collapse elemental constituents.
- Subject to degradation into chunks of pure neutrons that undergo rapid beta-decay and form strange high-mass isotopes.
- None of the above apply or we have no idea.
This is related to this question but I'm interested in the natural evolution of Neutron Stars left to their own devices rather than what would happen to chunks artificially broken off them.