Astronomers Find Clouds Of Primordial Gas From The Early Universe
November 11, 2011

Astronomers Find Clouds Of Primordial Gas From The Early Universe


Only the lightest elements, mostly hydrogen and helium, were created in the Big Bang. Then a few hundred million years passed before clumps of this primordial gas condensed to form the first stars, where heavier elements were forged. Until now, astronomers have always detected "metals" (their term for all elements heavier than hydrogen and helium) wherever they have looked in the universe.






Prior to this discovery, the lowest measurements of metal abundance in the universe were about one-thousandth the "metallicity" of the sun. "People had thought there was a 'floor' to metallicity, that nothing could be less than one-thousandth the solar enrichment. That's because the metals produced in galaxies were so widely dispersed in the universe," Fumagalli said. "So this was unexpected. It challenges our ideas about how metals are dispersed from the stars that produce them."


Powerful telescopes see distant objects as they were far back in time, due to the time it takes light to travel across the universe. The spectrographic analysis of the pristine gas clouds places them in time at about 2 billion years after the Big Bang, or nearly 12 billion years ago. At that time, theoretical models predict that galaxies were growing by pulling in vast streams of cold gas, but these "cold flows" have never been seen. According to Fumagalli, the pristine gas clouds are potential candidates for these elusive cold flows. Further studies are needed, however, to see if the newly discovered gas clouds are associated with galaxies.

This research was funded by the National Science Foundation.


Image Caption: This image from a simulation of galaxy formation shows streams of gas feeding the growing galaxy. The newly discovered gas clouds may be part of a "cold flow" of gas similar to these streams. Image from simulation by Ceverino, Dekel, and Primack.


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