Sifting through ashes of the first stars, astronomers have found significant amounts of iron, which dates the initial stellar furnaces to as early as 200 million years after the universe was born.
The discovery, announced today, supports and builds upon similar evidence derived by a different method earlier this year. Combined, the findings push stellar origins back to an earlier epoch than scientists thought just a few months ago.
Researchers do not understand how the first stars and their associated galaxies formed so rapidly. The new findings won't directly help unravel that mystery, but they pin down the time frame beyond dispute.
Ironclad evidence
Iron was not present when the universe was formed, presumably in a Big Bang, according to the leading theory. It and all other elements heavier than hydrogen and helium were forged in stars, chemical factories that produce successively heavier elements, from nitrogen to carbon and finally iron.
The earliest stars were massive, theory contends, and they lived short lives and died in fiery explosions, sending their ashes into the interstellar medium where the fresh elements mixed with existing gas to fuel new star birth.
http://www.space.com/scienceastronomy/hubble_first_stars_030430.html