  The first stars fundamentally transformed the early universe by emitting the
first light and by producing the first heavy elements. These effects were
predetermined by the mass distribution of the first stars, which is thought to
have been fixed by a complex interplay of gas accretion and protostellar
radiation. We performed radiation-hydrodynamics simulations that followed the
growth of a primordial protostar through to the early stages as a star with
thermo-nuclear burning. The circumstellar accretion disk was evaporated by
ultraviolet radiation from the star when its mass was 43 times that of the Sun.
Such massive primordial stars, in contrast to the often postulated extremely
massive stars, may help explain the fact that there are no signatures of the
pair-instability supernovae in abundance patterns of metal-poor stars in our
galaxy.
