JWST data show early galaxies spread heavy elements into space just 500 million years after the Big Bang

By the Everything Space news desk · 24 Sep 2026 · written from the sources below

Image: Phys.org

The finding suggests the early universe was less pristine than assumed, complicating the search for the first, unenriched stars.

Astronomers using data from the James Webb Space Telescope have found that some of the earliest known galaxies were already releasing heavy elements like carbon, oxygen and silicon into surrounding space far sooner than previously thought, according to a new study from University of Arizona researchers published in Nature Astronomy.

The study examined three galaxies whose light took more than 13 billion years to reach Earth, showing them as they existed roughly 500 million years after the Big Bang, during the Epoch of Reionization when the first stars and galaxies were transforming the early universe. Researchers used the galaxies' own light as a backdrop, studying how it was absorbed by surrounding gas to identify which elements were present.

The absorption patterns detected were blueshifted relative to each galaxy's redshift, indicating that enriched gas was actively flowing outward from these galaxies into intergalactic space. According to lead author Yongda Zhu, this shows that early galaxies were not just producing heavy elements through stellar processes but actively dispersing them into their surroundings, potentially influencing the formation of neighboring galaxies.

This challenges the long-held assumption that gas in the early universe remained largely pristine, consisting mainly of hydrogen and helium left over from the Big Bang. The chemical signatures found in these ancient galaxies closely resembled those seen in much later, more evolved galaxies, suggesting that the process of enriching the cosmos with heavier elements began earlier than models had predicted.

The findings also offer a possible explanation for why astronomers have never directly observed Population III stars, the theorized first generation of stars formed purely from hydrogen and helium before any heavier elements existed. If galaxies were already contaminating their surroundings with heavier elements this early, truly pristine gas clouds may not have persisted long enough for such stars to form and be observed.

The research relied on the infrared sensitivity of the James Webb Space Telescope, which allowed scientists to capture faint spectral signals from galaxies as they appeared roughly 13 billion years ago, using nearly 30 hours of exposure time. The work highlights baryon cycling, the exchange of material between galaxies and their surroundings, as a key process shaping the universe's chemical evolution from its very earliest epochs.

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