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The Pristine Universe

Observations reveal two gaseous regions with a composition close to that of the universe before the first stars were formed. The existence of everything around us today sometimes seems far removed from the thermonuclear reactions occurring in the interiors of stars and stellar supernovae. These processes are responsible for producing almost all elements heavier than helium and for dispersing these elements throughout the universe. On page 1245 of this issue, Fumagalli et al. (1) report two gaseous regions that consist of virtually pristine gas (no detected elements heavier than helium) at an epoch where none are expected to exist. These findings demonstrate the nonuniform dispersion of elements throughout the universe, with direct consequences on the formation epoch of first-generation stars.