Iron star

In astronomy, an iron star is a hypothetical type of compact 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 may be iron, according to some predictions, it is distinct from an iron star.

The term is also used for blue supergiants which have a forest of forbidden Fe_II lines in their spectra. They are potentially quiescent hot luminous blue variables. Eta Carinae has been described as a prototypical example.

In popular culture

• Soviet film The Andromeda Nebula: Episode I. Prisoners of the Iron Star is about a starship low on fuel caught by gravity of an iron star, which could only be seen in the infrared. It is based on the novel Andromeda: A Space-Age Tale by Ivan Yefremov written when Steady State theory was dominant and iron stars were expected to exist in our galaxy.

See also

• Future of an expanding universe
• Hypothetical star
• Heat death of the universe