Scientific American reports on a James Webb Space Telescope discovery, allowing scientists the first possible glimpses of the very first stars ever to shine in our universe:
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.
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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.
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Maiolino’s team used JWST to observe a galaxy called GN-z11 that was previously discovered by the Hubble Space Telescope in 2015. GN-z11 dates back to just 400 million years after the big bang and was the most distant known galaxy until JWST discovered ones that are farther away. Picking apart the light at the galaxy’s edge in a process called spectroscopy, they found hints of helium that could be linked to small pockets of Population III stars in the galaxy’s outer regions. If correct, the stars in the clump would have masses at least 500 times that of our sun, with a total mass of 600,000 solar masses, which would explain the signal seen by the team. “We are pushing the telescope to its limits,” Maiolino says.
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Vanzella’s team takes a different approach. Using the gravitational bulk of a galaxy cluster called MACS J0416, the team detected what appears to be a magnified emission of hydrogen and a small amount of oxygen from a very small and very remote galaxy. “It’s magnified by a factor of maybe 500,” says Mark Dickinson of the National Science Foundation’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab) in Arizona, who is a co-author of the paper. While the researchers were not able to see the light of the galaxy directly, their findings suggest the presence of two extremely small clumps of stars in the early universe, perhaps totaling less than 10,000 solar masses altogether and seen about 800 million years after the big bang. The clumps do not seem to be solely composed of Population III stars, but the amount of heavy elements present is incredibly small. “The heavy element abundance is lower than anything else we have seen in the universe,” Dickinson says. “It’s as close to a primordial galaxy as we’ve seen.”
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You can read Maiolino’s study here, in arXiv, and Vanzello’s study here, also in arXiv.