Scientists Discover Possible Signatures of the Universe’s First Stars

Astronomers have gained an unprecedented insight into some of the universe’s first stars, known as “Population III” stars. These primordial stars could significantly enhance our understanding of the early universe, including their mass and influence on subsequent star formation.

Predicted to be composed almost entirely of hydrogen and helium, these ancient stars were colossal—hundreds of times the size of our Sun—and reached scorching temperatures of tens of thousands of degrees.

Despite their crucial role in cosmic history, most Population III stars had short lifespans, leading to their explosions, and astronomers have not conclusively identified galaxies rich in these stars due to their extremely early existence.

Recently, Roberto Maiorino and researchers at the University of Cambridge uncovered that the Hebe Galaxy, which formed just 400 million years post-Big Bang, aligns perfectly with characteristics of a Population III galaxy.

It contains no detectable elements heavier than hydrogen or helium, and the emitted light concentrates around specific frequencies tied to helium, a signature only achievable through extremely hot stars like the Population III. “As we understand it, a Population III star seems to be the most plausible explanation,” stated Maiorino. “Any other explanations fall short.”

The Hebe Galaxy was initially identified in 2024 through observations made with the James Webb Space Telescope (JWST). While its spectrum initially suggested lines of ionized helium indicative of a Population III star, doubt lingered regarding the reality of these lines or the presence of heavier metals.

Further JWST observations revealed a second line linked to ionized hydrogen from the same source, confirming the presence of helium.

“We invested significant time analyzing the data to validate this line detection,” said Hannah Uebler from Ludwig-Maximilians-University, Munich. “Discovering the peak in ionized hydrogen without additional detection was a pleasant surprise, confirming our previous claims of helium and hydrogen indicating a Population III scenario.”

The compelling results suggest we are witnessing a very hot object, consistent with expectations for a Population III star. Daniel Whalen, studying at the University of Portsmouth, UK, notes that while findings are promising, precision remains insufficient to exclude heavy elements typical of more mature Population II stars.

A galaxy populated predominantly by Population III stars, as anticipated by Maiorino and his team, poses challenges even in existing simulations of early universe conditions. These simulations indicate that initial stars typically formed in isolated, sparse clusters.

“This is not merely a quest to claim we found Population III stars,” said Maiorino. “We have gained significant insights already.” If Hebe’s stars are confirmed as Population III, it could yield vital knowledge about the universe’s infancy.

Maiorino and his team have leveraged early observations from Hebe to infer that most of the original stars had masses between 10 to 100 times that of the Sun, with significantly fewer being smaller.