JWST May Have Detected the Universe’s First Stars in a Distant Galaxy

Summary: New analysis of James Webb Space Telescope (JWST) data suggests the first generation of stars — Population III (Pop III) — may have been seen in a galaxy called LAP1-B. The signal became observable thanks to JWST’s infrared sensitivity combined with ~100× magnification from gravitational lensing by the galaxy cluster MACS J0416.1-2403.

What was found

A team led by Eli Visbal (University of Toledo) reports that the light from galaxy LAP1-B has traveled roughly 13 billion years to reach us, showing the system as it was about 800 million years after the Big Bang. Their analysis indicates the stars in LAP1-B are surrounded by gas with almost no heavy elements (very low metallicity) and appear concentrated in compact groups with a total mass of order ~1,000 solar masses — characteristics expected for primordial Pop III stars.

How they detected it

The detection relied on two factors: JWST’s unprecedented infrared sensitivity and strong gravitational lensing. A foreground galaxy cluster, MACS J0416.1-2403, located roughly 4.3 billion light-years away, magnified LAP1-B by about 100 times. That magnification made otherwise faint signatures visible to JWST.

"To discover Pop III stars, we really needed the sensitivity of JWST, and we also needed the 100 times magnification from gravitational lensing," said Eli Visbal. "If indeed the stars of LAP1-B are Pop III, this is the first detection of these primordial stars."

Why it matters

Pop III stars are predicted to form from nearly pristine hydrogen and helium, before significant enrichment with heavier elements (metals). Because metal-poor gas cools less efficiently and fragments less, these primordial stars could grow to very high masses — often tens to hundreds of times the mass of the Sun — and form in small dense groups. Detecting Pop III stars would illuminate the earliest stages of star and galaxy formation and provide constraints on early-universe models, including aspects of dark matter that affect where the first stars form.

Next steps

The team plans to run more detailed hydrodynamical simulations of the transition from Pop III to Pop II stars to see whether the models reproduce the observed spectrum of LAP1-B and similar targets. Their results were published in The Astrophysical Journal Letters.

Notes: The interpretation remains provisional. While the evidence — low-metal gas, compact stellar mass, and the epoch observed — is consistent with Pop III expectations, follow-up observations and modelling are needed to confirm the identification definitively.