Exotic star
An exotic star is a hypothetical compact star composed of exotic matter (something not made of electrons, protons, neutrons, or muons), and balanced against gravitational collapse by degeneracy pressure or other quantum properties.
Types of exotic stars include
- quark stars (composed of quarks)
- strange stars (composed of strange quark matter, a condensate of up, down, and strange quarks)
- § Preon stars (speculative material composed of preons, which are hypothetical particles and "building blocks" of quarks and leptons, should quarks be decomposable into component sub-particles).
Of the various types of exotic star proposed, the most well evidenced and understood is the quark star, although its existence is not confirmed.