For 10 points, name this hypothetical extremely low- or zero-metallicity oldest generation of stars in the universe.
The complete destruction of these bodies after their internal pressure is reduced by positron-electron annihilation is likely responsible for the early uniform distribution of heavy elements in the interstellar medium. That end-state of these bodies, unique to objects between 140 and 260 solar masses, is known as a pair-instability supernova. The era in which these objects formed ended when the primordial gas was sufficiently "pre-enriched" that cloud fragmentation proceeded in multiple steps. Despite their high mass, these objects did not process material via the (*) CNO cycle. The fact that even halo stars have Z/H ratios six orders of magnitude higher than is consistent with accepted models of the Big Bang gave rise to the hypothesis of these objects' existence. The formation of these objects signifies the end of the cosmic dark ages. For 10 points, name this hypothetical extremely low- or zero-metallicity oldest generation of stars in the universe.
The complete destruction of these bodies after their internal pressure is reduced by positron-electron annihilation is likely responsible for the early uniform distribution of heavy elements in the interstellar medium.
Population III Stars [prompt on "early stars," "first stars," or similarly vague descriptions]