In astronomy, an iron star is a hypothetical type of star that could occur in the universe in 101500 years. The premise behind iron stars states that cold fusion occurring via quantum tunnelling would cause the light nuclei in ordinary matter to fuse into iron-56 nuclei. Fission and alpha-particle emission would then make heavy nuclei decay into iron, converting stellar-mass objects to cold spheres of iron. The formation of these stars is only a possibility if the proton does not decay.
Though the surface of a Neutron star is iron, it is distinct from an iron star.