Astronomers Think They May Have Spotted the Universe’s First Stars Glowing From the Dawn of Time

Artist’s impression of a field of Population III stars as they would have appeared after the Big Bang. Credit: Wikimedia Commons/ NOIRLab/NSF/AURA/J. da Silva/Spaceengine

Astronomers have chased the first stars for decades, squinting at the early universe for any hint of their brief, brilliant lives. Now a tiny, lensed speck coined LAP1-B may be the clearest glimpse yet.

In a multi-university analysis of James Webb Space Telescope (JWST) data published in The Astrophysical Journal Letters, led by the University of Toledo and Columbia University, researchers argue that LAP1-B behaves exactly as theorists said the very first generation of Population III (Pop III) stars should.

What Were The First Stars?

Pop III stars were forged from the universe’s original recipe: hydrogen and helium with a dash of lithium, no heavier elements at all. That matters because “metals” (anything heavier than helium) change how gas cools and fragments. With no metals around, the first stars were expected to be monsters; tens to perhaps a thousand times the mass of the Sun and burning furiously while dying young. Their supernovae then seeded space with the first oxygen, carbon, and other elements that later generations used to build planets, and eventually us.

We see LAP1-B as it was about 800 million years after the Big Bang. It’s only visible because a foreground galaxy cluster acts like a cosmic magnifying glass, boosting its light by orders of magnitude — a trick known as gravitational lensing. In JWST’s spectrum, LAP1-B stands out not for a bright starlight “continuum,” but for intense emission lines from glowing hydrogen. That’s the calling card of very young, very hot stars.

What makes this object compelling is how neatly it fits three longstanding predictions for Pop III systems. First, theory says the earliest stars should form in small dark-matter halos just massive enough for plain hydrogen to cool — so-called “atomic-cooling” halos. The team estimates that LAP1-B resides in a dark-matter clump of roughly 50 million solar masses, right on target for that threshold.

Second, the stars themselves should be massive, with a “top-heavy” distribution skewed toward big bodies. The line ratios in LAP1-B match what you’d expect from such giants.

Third, fierce feedback from these stars — radiation, winds and supernovae — should keep clusters small. Converting the observed hydrogen line strength into stellar mass points to only a few thousand Suns’ worth of massive stars in total. That’s modest, and that’s the point.

The gas around LAP1-B also shows spectral fingerprints of only trace metals, consistent with a system so young that its first heavy elements were minted locally, either from a handful of early supernovae or from winds driven by rapidly spinning massive stars. In other words, the pollution has begun, but just barely.

Statistics back the story. Because JWST was peering under the lamppost of a strong lens, the team asked how many Pop III clusters you’d expect to catch there, at that epoch, with Webb’s sensitivity. Their answer: about one. However, the researchers believe there might be many more lurking in the universe.

Not everyone is ready to declare victory, though.

In an interview with New Scientist, Roberto Maiolino of the University of Cambridge calls LAP-B1 “an extremely interesting candidate, but it is still far from having the clear, unambiguous signatures that we expect for a clean Population III detection.”

Caution is healthy here. Open questions remain about how efficiently the first stars formed, how long pristine pockets could survive, and exactly how much material early supernovae ejected. But as a target and a template, LAP1-B is gold. It demonstrates the power of pairing JWST’s infrared sensitivity with gravitational lensing to turn barely-there specks into measurable signals. And it shows that theory, observation and even the expected headcount can align.

The authors themselves hedge appropriately. Astronomy is a team sport played over years, not press cycles. Still, there is room for optimism. LAP1-B may only represent the tip of the iceberg for cluster-lensed Pop III studies. If that’s true, the first stars won’t stay first-and-only for long. Deeper looks, more lensing fields and a bit of luck could turn this promising candidate into the opening chapter of a much larger story about how the universe switched on the lights.