Webb telescope data hints at heavy elements in early universe galaxies

September 24, 2026 at 10:38 PM2 min

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Astronomers using the James Webb Space Telescope detected oxygen, carbon, and silicon in gas surrounding three galaxies that existed about 500 million years after the Big Bang. The gas is moving outward at 50–250 km/s, indicating that early galaxies rapidly enriched their surroundings with heavy elements. The finding challenges assumptions about the pristine nature of the early universe and the search for the first stars.

Key Facts

The James Webb Space Telescope detected absorption lines of neutral and ionized oxygen, carbon, and silicon in gas around three galaxies at redshift z = 7.2–9.3, when the universe was about 500 million years old.
The enriched gas is moving outward from the galaxies at velocities of 50–250 km/s, as indicated by blueshifted absorption lines.
The observations were made during a 30-hour observing session using the NIRSpec spectrograph on board Webb.
The chemical signature of these early galaxies resembles that of much more mature galaxies, suggesting a rapid establishment of the baryon cycle.
The presence of heavy elements so early in cosmic history implies that pristine gas for Population III stars may be scarcer than previously thought.

Detection of Heavy Elements

A team from the University of Arizona reported the detection of heavy elements in gas surrounding three galaxies at redshifts between 7.2 and 9.3. The galaxies were observed during a 30-hour session with the James Webb Space Telescope's NIRSpec spectrograph. Absorption lines of neutral and ionized oxygen, carbon, and silicon were identified in the spectra of background galaxies shining through the surrounding gas. The lines are predominantly blueshifted relative to the galaxies' systemic velocities, indicating outflow speeds of 50–250 km/s.

Implications for Early Galaxy Evolution

The outflowing enriched gas suggests that the baryon cycle—the exchange of matter between galaxies and their surroundings—was already operating within the first few hundred million years after the Big Bang. Massive first-generation stars likely synthesized carbon, oxygen, and other elements, which were then expelled by stellar winds and supernova explosions. The chemical fingerprint of these early galaxies resembles that of significantly more mature galaxies, indicating rapid establishment of matter recycling.

Impact on Population III Star Search

Population III stars are hypothesized to be the first generation of stars formed from nearly pure hydrogen and helium. If galaxies were already ejecting heavy elements into intergalactic space 500 million years after the Big Bang, the amount of pristine gas available for Population III star formation may be much lower than models predicted. This finding complicates the search for the very first stars in the universe.