There’s a new contender for the universe’s earliest first-generation stars.
A bright clump seen about 450 million years after the Big Bang has the chemical hallmarks of first-generation stars — notably that it appears to have no elements heavier than helium. This identification, reported in a trio of papers submitted March 20 to arXiv.org, pushes evidence for these pristine stars much earlier than previous candidates.
First-generation stars, known as population III stars, probably would have been massive — up to 1,000 times the mass of the sun — and very bright. These stars were born with only the elements created in the Big Bang: hydrogen, helium and a tiny amount of lithium. The stars we see in the night sky, on the other hand, also contain heavier elements forged by and passed down from previous generations of stars.
Astronomers think the earliest of the first-generation stars formed a couple hundred million years after Big Bang — over 13.5 billion years ago. But until now, researchers had seen evidence of such stars only around 1 billion years after the start of the universe. The new report of much earlier candidates increases astronomers’ confidence of finding more such systems in the early universe, says astronomer Seiji Fujimoto of the University of Toronto, who was not involved in the research.
The clump, which the astronomers dubbed Hebe (named partially for the goddess of youth in Greek mythology, partially for the technical name of one of the wavelengths of light it emits), was first spotted in 2024. At the time, astronomers lacked the evidence to determine the object’s nature. So in 2025, they took higher resolution observations with the James Webb Space Telescope.
To determine if a candidate is a first-generation star, astronomers first look for evidence of elements heavier than helium. Hebe not only showed no evidence of heavier elements but also emitted light specific to highly energized helium and hydrogen. This light, emitted by gas clouds, indicates that the clump contains an object or objects that emit extremely high-energy radiation.
“It’s a textbook case for the first generation of stars,” says astronomer Roberto Maiolino of University of Cambridge, a coauthor on the studies. “There’s no other really satisfactory explanations for other kinds of sources.”
The team estimates that Hebe is up to 1,200 light-years across, with two distinct clusters, and contains the mass of between 10,000 and several hundred thousand suns. But since first-generation stars are hefty, the cluster may have no more than a few hundred stars.
Hebe was also discovered near a galaxy, named GN-z11, with the mass of 1 billion suns. Some computer simulations suggest population III stars shouldn’t be found near such galaxies, which are chemically evolved and have therefore polluted their environments with heavy elements. Hebe’s proximity to GN-z11, Fujimoto says, “opens up new questions about how such systems form and survive.”
Other simulations suggest the gravity of these galaxies could pull in pockets of pristine gas from their surroundings, creating the conditions for population III stars to form. The discovery of Hebe, along with future studies of population III candidates, will help astronomers better understand the birthplaces of these pristine stars, Maiolino says.
