Iron star

In astronomy, an iron star is a hypothetical type of compact star that could occur in the universe in the extremely far future, after perhaps 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.^[1] 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.

Unrelatedly, 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.^[2][3]

In popular culture

• The Soviet film The Andromeda Nebula: Episode I. Prisoners of the Iron Star is about a starship low on fuel caught by the 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 the Milky Way.

See also

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

References

1. 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.
2. 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.
3. 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.