Hypothetical star

This article is about scientifically accepted hypothetical star types. For stars in religion, see Stars proposed in religion (disambiguation). For other hypothetical astronomical objects, see Hypothetical astronomical object.

A hypothetical star is a star, or type of star, that is speculated to exist but has yet to be definitively observed. Hypothetical types of stars have been conjectured to exist, have existed or will exist in the future universe.

Types

Scientifically speculated hypothetical types include:

Type	Description	Candidates	Notes	Refs
Blitzar	Neutron star with a rapid rotation.
Blue dwarf	conjectured to develop after a red dwarf has exhausted its hydrogen.	N/A	The universe is not old enough for this form to come into existence.
Black dwarf	the final state for a star, like the Sun, that is too small to become either a black hole or a neutron star. It would take a star like our Sun roughly a quadrillion years to reach this state, so none are believed to exist today.	N/A	The universe is not old enough for this form to come into existence.
Black star	a star predicted in semiclassical gravity which collapses into a black hole state but has neither a gravitational singularity nor an event horizon.
Boson star	a star or astronomical object made of bosons, such as photons or gluons, rather than conventional matter.	none
Dark energy star	a conjectured alternative to a black hole.
Dark matter star	conjectured to have existed early in the universe.
Dark star	a theoretical construct based on Newtonian gravitation, of a star with gravity so strong that even light cannot escape.	N/A	This form cannot exist, as Newtonian gravitation is not correct under these gravity conditions.
Electroweak star	a star where gravitational collapse is prevented by radiation pressure resulting from electroweak burning.	none
Frozen star	A very low-mass star with a surface temperature of only around 273 Kelvin that could form in the far future, when the metallicity of the interstellar medium is several times the current one.	N/A	The universe is not old enough for this form to come into existence.
Fuzzball	a formulation of black holes in string theory.
Gravastar	an alternative to a black hole that denies the possibility of a singularity.
Grey hole	a conjectured type of neutron star, where most light does not escape the star.
Intermediate-mass black hole	a black hole that is roughly a few thousand times the mass of the Sun; thus larger than a stellar mass black hole yet smaller than a supermassive black hole.
Iron star	a final state for a star in the far future (101500 years) of the universe, when all matter is transmuted to iron via quantum tunnelling.	N/A	The universe is not old enough for this form to come into existence.
Magnetospheric eternally collapsing object	a hypothetical alternative to black holes.
Planck star	a star where the energy density is around the Planck density.
Population III star	stars virtually free of metals believed to have existed in the early universe.	none
Preon star	a star with a core composed of preons.	none
Q star	a compact, heavy neutron star with an exotic state of matter.	V404 Cygni
Quark star	star composed of quark matter or strange matter.	3C 58, PSR B0943+10, XTE J1739-285
Quasi-star	a conjectured star from the early universe with a black hole at its center.	none
Strange star	a form of quark star, a neutron star with strange matter at its core, or star which is a ball of strange matter.
Thorne–Żytkow object	a red giant or red supergiant whose core is a neutron star.	U Aquarii
White hole	the polar opposite of a black hole, it ejects matter from its core into space.

Specific stars

Specific hypothetical stars include:

Star	Description	Notes	Refs
Nemesis	a star proposed as a companion to the Sun by Richard A. Muller in 1984
3 Cassiopeiae	a star recorded by astronomer John Flamsteed, but never seen again
34 Tauri	a star recorded by John Flamsteed later revealed to have been the planet Uranus

See also

• Hypothetical astronomical object