NASA’s James Webb Space Telescope (JWST) observed three galaxies 500 million years after the Big Bang, revealing they had already dispersed heavy elements like carbon, oxygen, and silicon into intergalactic space, challenging models of early cosmic evolution.
The findings, published in Nature Astronomy, show that galaxies in the early universe were not isolated but actively exchanging material, a process called baryon cycling, much earlier than previously thought. This suggests that the “pristine” gas environments assumed to dominate the early cosmos were rapidly mixed with heavier elements, potentially explaining why Population III stars—composed solely of hydrogen and helium—remain undetected.
JWST’s Spectroscopic Breakthrough
Using JWST’s Near-Infrared Spectrograph (NIRSpec) in micro-shutter assembly (MSA) mode, astronomers analyzed three galaxies at redshifts between 7.3 and 9.3, corresponding to 500 million years after the Big Bang. The team, led by the University of Arizona, examined ultraviolet absorption patterns in the galaxies’ light, which passed through surrounding gas, revealing chemical fingerprints of heavy elements.
The data, processed through the JWST Calibration Pipeline, showed that these galaxies had stellar masses ranging from 10⁹.1 to 10⁹.8 solar masses and exhibited blueshifted absorption features—indicating gas carrying oxygen, carbon, and silicon was escaping into intergalactic space. This outflow, detected over nearly 30 hours of observation, suggests galaxies were not just producing heavy elements but actively dispersing them, possibly seeding other galaxies.
A Cosmic “Food Dye” Analogy
The chemical signatures of these infant galaxies closely matched those of evolved galaxies billions of years later, indicating that baryon cycling—where galaxies produce, expel, and recycle elements—was already underway in the universe’s infancy. This challenges the long-held assumption that early galaxies were surrounded by nearly pristine hydrogen and helium gas.
Implications for Population III Stars
The discovery has profound implications for understanding Population III stars, the first generation of stars thought to form from primordial gas. If heavy elements were dispersed within 500 million years of the Big Bang, truly pristine gas environments may have been fleeting, offering an explanation for the elusiveness of these stars.
We observed that heavy elements escaped from galaxies very, very early in cosmic time,
Zhu said. Not only were the galaxies producing these elements, but they were also dispersing them, possibly seeding other galaxies.
This rapid enrichment could have accelerated the formation of later generations of stars and galaxies, reshaping the universe’s chemical evolution.
The study, which used JWST’s infrared capabilities to observe galaxies as they appeared 13 billion years ago, underscores the telescope’s role in rewriting cosmic history. As researchers continue analyzing data from the James Webb Space Telescope, the focus will shift to confirming these findings across more galaxies and understanding their broader impact on the universe’s development.