The First Stars
  Pop III stars are the key to the character of primeval galaxies, the first
heavy elements, the onset of cosmological reionization, and the seeds of
supermassive black holes. Unfortunately, in spite of their increasing
sophistication, numerical models of Pop III star formation cannot yet predict
the masses of the first stars. Because they lie at the edge of the observable
universe, individual Pop III stars will also remain beyond the reach of
telescopes for the foreseeable future, and so their properties remain unknown.
However, it will soon be possible to constrain their masses by the direct
detection of their supernovae and by reconciling their nucleosynthetic yields
to the chemical abundances measured in ancient metal-poor stars in the Galactic
halo, some of which may be bear the ashes of the first stars. Here, I review
current problems on the simulation frontier in Pop III star formation and
discuss the best prospects for constraining their properties observationally in
the near term.
