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 protons do not decay. Though the surface of a neutron star may be iron according to some predictions, it is distinct from an iron star.
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. Eta Carinae has been described as a prototypical example.
In popular culture
- The Soviet film The Andromeda Nebula is about a starship low on fuel caught by an iron star's gravity, with the star itself being so dim that it 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 the Milky Way.
- In the episode: Civilizations at the End of Time: Iron Stars, Isaac Arthur discusses about the possiblilites of advanced artificial civilizations living around iron stars, and beyond the last viable sources of energy.
- Dyson, Freeman J. (1979). "Time without end: Physics and biology in an open universe". Reviews of Modern Physics. 51 (3): 447–460. Bibcode:1979RvMP...51..447D. doi:10.1103/RevModPhys.51.447.
- Walborn, Nolan R.; Fitzpatrick, Edward L. (2000). "The OB Zoo: A Digital Atlas of Peculiar Spectra". The Publications of the Astronomical Society of the Pacific. 112 (767): 50. Bibcode:2000PASP..112...50W. doi:10.1086/316490.
- Clark, J. S.; Castro, N.; Garcia, M.; Herrero, A.; Najarro, F.; Negueruela, I.; Ritchie, B. W.; Smith, K. T. (2012). "On the nature of candidate luminous blue variables in M 33". Astronomy & Astrophysics. 541: A146. arXiv:1202.4409. Bibcode:2012A&A...541A.146C. doi:10.1051/0004-6361/201118440.