By Ron Cowen
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Out of the darkness came the light. About 400,000 years after the Big Bang, the radiation from that fireball cooled and faded, plunging the cosmos into blackness. A few hundred million years later, the first stars emerged and relit the universe. And now scientists have a better idea how it happened.
Astronomers have long struggled to accurately model this milestone event. Simulations suggested that clouds of dark matter — invisible material making up more than 80 percent of the mass of the universe — gathered and compressed pockets of the hydrogen and helium gases forged during the Big Bang. When the compressed gases achieved densities high enough to ignite nuclear reactions, a star was born. And according to these models it was a whopper — 100 to 300 times the mass of the sun.
But such simulations arrive at the final mass estimate by leapfrogging over some of the trickier astrophysics, making the models uncertain. A new model, described by Naoki Yoshida of Nagoya University in Japan and his colleagues in the August 1 Science, for the first time simulates the formation of a primordial star without having to rely on an array of approximations.