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Scientific American | At Last, Astronomers May Have Seen the Universe’s First Stars

Telltale evidence gathered by the James Webb Space Telescope suggests we’re closer than ever before to finding elusive Population III stars The James Webb Space Telescope (JWST) was built primarily to transform our understanding of the early universe. Less than a year after it was switched on, it is delivering, finding galaxies earlier in the universe than any seen before. Yet the telescope has another, less publicized goal in probing those earliest moments after the big bang 13.8 billion years ago. It is hunting for signs of the first stars to switch on in the universe, so-called Population III stars, gigantic balls purely made of hydrogen and helium that shined brilliant and brightly to first bring light to the cosmos. “They’ve been sort of in the background,” says Garth Illingworth of the University of California, Santa Cruz, largely because finding them is so difficult. No definitive detection of such stars has ever been made, but we know they must exist. Now two new results are bringing us closer than ever before to their discovery. In a pair of papers posted on the preprint server arXiv.org, two teams of astronomers report promising signs of Population III stars. In the first study, led by Roberto Maiolino of the University of Cambridge, researchers think they may have found a pocket of Population III stars nestling in the outskirts of a remote galaxy. The second study, led by Eros Vanzella of the National Institute for Astrophysics in Italy, hints at a tiny galaxy that may be composed of, if not Population III stars per se, extremely primordial stars born early in the cosmos. “These papers quite nicely highlight the different aspects of the search,” says Jorryt Matthee of the Swiss Federal Institute of Technology in Zurich, who was not involved with either paper. “We’re almost there.” Once the universe had cooled and calmed sufficiently about 400,000 years after the big bang, the first atoms were able to form: hydrogen and helium. These atoms would have clumped together into immense clouds under gravity and eventually formed Population III stars. Unhindered by competition from other stars, these stars may have grown to huge sizes within these clumps—at least hundreds or even thousands of times more massive than our sun. This bulk meant the stars were short-lived, exhausting their fuel and exploding as supernovae within just a few million years. Yet those explosions were vital to the universe. They released heavier elements that had formed inside the stars, such as oxygen and carbon, which gave rise to Population II stars and, later, Population I stars such as our sun and even planets such as Earth and life itself. Read more at Scientific American.