exotic star

The term exotic star is a catch-all for very unusual theoretical types of stars. Some examples:

• quark star - containing quark matter, matter broken down into quarks.
• strange star - a quark star including strange quark matter, a type of quark matter including strange quarks.
• preon star - preons are theoretical particles that would be the building-blocks of quarks.
• boson star - composed of some sort of bosons (the primary constituent of most stars, ¹H, is not a boson) such as axions.
• dark star aka dark matter star - early-universe-giant star incorporating enough dark matter in the form of neutralinos that halts its collapse, preventing its surface temperature from rising; possibly the progenitors of supermassive black holes.
• quasi-star aka black hole star - early-universe very large/massive star (1000 solar masses) powered through a core consisting of a black hole; also possible progenitors of SMBHs.
• iron star - star in far future composed entirely of iron.

Note that the term dark star was also a very early term for black holes.