"A strange star is a hypothetical astronomical object, a quark star made of strange quark matter Strange stars might exist without regard to the Bodmer–Witten assumption of stability at near-zero temperatures and pressures, as strange quark matter might form and remain stable at the core of neutron stars, in the same way as ordinary quark matter could.[4] Such strange stars will naturally have a crust layer of neutron star material. The depth of the crust layer will depend on the physical conditions and circumstances of the entire star and on the properties of strange quark matter in general.[5] Stars partially made up of quark matter (including strange quark matter) are also referred to as hybrid stars."