Unrelatedly, the term "iron star" is also used for blue supergiants which have a forest of forbidden FeII lines in their spectra.
They are potentially quiescent hot luminous blue variables.
The premise behind the formation of 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.
[3] The formation of these stars is only a possibility if protons do not decay.