The formation of the first stars
Christopher McKee (U.C. Berkeley, USA)

Jeudi 30 mars 2006

The first stars formed out of pristine gas with initial conditions determined by the Big Bang. These stars created the first heavy elements and began the process of reionizing the universe. They may have produced gamma-ray bursts when they died as supernovae, opening up the possibility that they could be observed directly.

The gravitational collapse of the gas that forms the first stars can be described analytically by a theory developed for contemporary star formation. Rotation of the infalling gas has a major effect on the protostar, making it smaller and hotter than in the absence of rotation. The mass of the first stars is set by feedback processes, including photodissociation of H2 by ultraviolet radiation, radiation pressure associated with Lyman alpha photons, the development of an HII region, and photoevaporation of the protostellar accretion disk. The typical mass of the first stars appears to be about 200 solar masses, which is more massive than any star observed in the Galaxy today.