A candidate for the earliest stellar generation

Astronomers may have found their strongest evidence yet for Population III stars, the first generation of stars thought to have formed after the big bang. According to the supplied report, researchers studying a distant galaxy known as Hebe say its light carries the hallmarks expected from stars made almost entirely of hydrogen and helium, without the heavier elements seen in later stellar populations.

The result matters because Population III stars have long been central to models of the early universe, yet direct evidence has remained elusive. These stars are thought to have formed when the cosmos was still chemically simple, before repeated cycles of stellar birth and death enriched galaxies with heavier elements. If the interpretation of Hebe is correct, the observations would offer a rare window into a formative era of cosmic history.

Why Hebe stands out

The candidate galaxy existed around 400 million years after the big bang, placing it deep in the universe’s infancy. Researchers led by Roberto Maiolino at the University of Cambridge reported that Hebe appears to contain no observable elements heavier than hydrogen or helium. Just as important, the light from the galaxy is concentrated around a telltale helium frequency associated with helium that has been stripped of its electrons.

That detail is significant because ionized helium of this sort requires extremely hot stars. The report says Population III stars are expected to be enormous and blazingly hot, potentially hundreds of times more massive than the sun and tens of thousands of degrees hotter. Those properties would make them capable of producing the radiation needed to generate the observed signal.

Maiolino said Population III stars appear to be the most plausible explanation available from the current evidence. The supplied text also notes that alternative explanations were judged unsatisfactory by the team.

From hint to stronger case

Hebe was first identified in 2024 with the James Webb Space Telescope. At that stage, researchers saw a spectrum that appeared to include an ionized helium line suggestive of Population III stars. But that early result left room for doubt. Scientists still needed to determine whether the helium signal was real, whether it came from the same source, and whether heavier elements might still be present.

Further Webb observations appear to have tightened the case. The team found a second spectral line, associated with ionized hydrogen and coming from the same source. According to the report, that supports the conclusion that the helium detection is genuine rather than contamination from another object.

Team member Hannah Uebler said she spent substantial time scrutinizing the data to make sure the line detection was secure. That note of caution is important. Claims involving the first stars are unusually consequential, and astronomers have reason to be conservative before treating a target as a true Population III system.

Why first stars matter

The first stars occupy a special place in cosmology because they helped transform the young universe. Formed from primordial gas, they likely played a major role in heating and ionizing their surroundings and in creating the first heavier elements through nuclear fusion and stellar explosions.

Finding such stars, or galaxies dominated by them, could help answer several longstanding questions:

  • How massive the earliest stars typically were.
  • How quickly the first galaxies became chemically enriched.
  • How early stellar populations influenced later generations of stars.
  • How radiation from the first luminous objects reshaped the early universe.

The supplied report emphasizes that Population III stars lived short lives before exploding, which helps explain why astronomers have struggled to catch them. By the time many distant systems become observable, those earliest stars may already have vanished, leaving only chemically enriched descendants behind.

A cautious milestone, not a final verdict

Even if Hebe becomes the leading candidate so far, the finding is best treated as strong evidence rather than final proof. The report frames the discovery as the most compelling glimpse yet, not a conclusive identification. That distinction matters because the farther astronomers look into the early universe, the more carefully they must test whether unusual signals reflect novel physics, measurement limits, or overlapping sources.

Still, the observation illustrates Webb’s growing power in early-universe astronomy. By capturing spectra from extremely distant galaxies, the telescope is helping move questions about the first stars from theory toward observation. If additional systems like Hebe are found, researchers may soon be able to compare candidates rather than relying on a single extraordinary case.

For now, Hebe appears to offer something astronomers have wanted for decades: a plausible sightline to stars unlike any that exist today, formed before the universe had much beyond hydrogen, helium, and the conditions needed to ignite the first cosmic lights.

This article is based on reporting by New Scientist. Read the original article.