The universe’s earliest galaxies may have begun enriching their surroundings with heavy elements far sooner than astronomers expected, a new study by researchers at the University of Arizona has found.
Published in Nature Astronomy, the study used observations from NASA’s James Webb Space Telescope (JWST) to examine three galaxies as they appeared about 500 million years after the Big Bang. Researchers found evidence that elements such as carbon, oxygen and silicon were already escaping these young galaxies and moving into intergalactic space.
Astronomers had expected much of the gas surrounding such early galaxies to remain relatively pristine, containing mostly hydrogen and helium — the primary elements present in the newborn universe. Heavier elements were produced later inside stars through nuclear reactions and released into space when stars died or exploded as supernovae.
The researchers analysed absorption patterns in the light from the three distant galaxies. The absorption lines were blue-shifted relative to the galaxies, indicating that the gas containing heavy elements was moving outward. Nearly 30 hours of JWST observations provided enough light to identify these faint chemical signatures.
The findings suggest that baryon cycling — the movement and recycling of material between galaxies and their surroundings — was already occurring during the Epoch of Reionization.
The findings may also have implications for the search for Population III stars, hypothesised to be the first generation of stars formed from pristine hydrogen and helium. The rapid appearance of heavy elements suggests that such pristine gas may have become increasingly uncommon as early galaxies began enriching their surroundings.