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.
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.
By the end of 101076 years, iron stars would
have collapsed into neutron stars and black
holes.
Unrelatedly, the term 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 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
