Astronomers using the James Webb Space Telescope may have spotted the first cluster of primordial Population III stars in a galaxy called LAP1-B. These ancient stars, formed from pure hydrogen and helium, offer clues to the early universe's chemistry. The discovery, though promising, requires further confirmation due to its rarity.
Population III stars represent the universe's first generation, forming from pristine hydrogen and helium gas before heavier elements emerged from supernovae. Unlike modern Population I stars, they are expected to be larger and hotter. A team led by Eli Visbal at the University of Toledo in Ohio analyzed James Webb Space Telescope (JWST) observations of LAP1-B, a galaxy at redshift 6.6, visible as it existed about 800 million years after the big bang.
The galaxy's light was magnified by gravitational lensing from a nearer cluster, allowing detection. "There should be tons and tons of these all over the observable universe, but we can only look sort of under the lamppost of this cluster that’s magnifying the light," Visbal said. The team's calculations predicted roughly one such Population III cluster at this redshift, matching their finding. LAP1-B's stellar mass, equivalent to a few thousand suns, aligns with simulations of early star cluster formation.
"This is the best candidate we have so far," Visbal noted. Most Population III stars are thought to have existed between 100 and 400 million years post-big bang, making this late detection intriguing but skeptical. "This object ticks many of the boxes, but I am a bit sceptical because it’s late in the game for these stars to be around, and there may be alternatives that might do the job as well," said Ralf Klessen at Heidelberg University in Germany.
Pockets of pristine gas might have persisted longer, Visbal suggested. Roberto Maiolino at the University of Cambridge called LAP1-B "an extremely interesting candidate, but it is still far from having the clear, unambiguous signatures that we expect for a clean Population III detection." Deeper observations and simulations are needed.
Understanding these stars is key to tracing heavy element formation. "They can tell us how the chemistry of the universe evolved from just hydrogen and helium to all the cool chemistry and life and everything that we have in the universe today," Visbal explained. The findings appear in The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/ae122f).