The farthest star sheds new light on the early universe

“We almost didn’t believe it at first, it was so much further than the previous most distant star,” Brian Welch, a PhD student at Johns Hopkins University and lead author of a Nature paper detailing the discovery, said in a NASA report. press release. “Normally, entire galaxies look like tiny specks at these distances. The galaxy that hosts this star has been magnified and distorted by gravitational lensing into a long crescent moon we’ve called the ‘Sunrise Arc’.

Studying this arc in detail as part of Hubble’s Reionization Lensing Cluster Survey (RELICS) program — which analyzes images taken by these gravitational lenses to peer into the early Universe — Welch was able to see Earendel, emerging from the general glow of its own galaxy, thanks to the lens effect that boosted its brightness. Welch is a fan of JRR Tolkein’s work and named the star after a character from The Silmarillion whose name means morning star. “We thought that was very appropriate, because this is a star from the beginning of star formation, the beginning of time,” says Thaler.

Although Earendel is long dead, looking at his “baby photos” can give us important clues about the nature of the universe and the origin of matter. “You’re actually looking at the time when most of the chemical elements that make up our bodies were formed,” says Thaler. “The universe started with just hydrogen and helium gas. That is it. Everything else, like the calcium in my teeth or the iron in my blood, had to form in stellar nuclei that then exploded. And so this first generation of stars produced a huge amount of these heavier, richer chemicals, the things that make life possible.”

Researchers have been able to make basic inferences about Earendel based on its brightness and color profile. But to learn more — and confirm that it is indeed a single star rather than a double or triple star system — more observations are needed. That’s where the newly launched James Webb Space Telescope could play an important role. Hubble is 32 years old and may have a decade to live, so the fact that the star aligns with the gravitational lens during the short period that both Hubble and the JWST are available to take a picture is another novelty. luck for scientists. “The two working together will reveal so much more about the universe than we’ve ever known,” Smethurst says.

Unlike Hubble, who sees mostly in the visible light spectrum, the JWST sees in infrared, which gives it more information about Earendel’s chemical makeup. “Webb can really tap into that, do some spectroscopy, separate the light into a rainbow to find out what the chemistry is, what the temperature of the star is, all that,” Thaler says.

There’s a slim chance that Earendel could be a so-called Population III star — a hypothetical category of stellar objects composed purely of hydrogen and helium that were there immediately after the Big Bang. “We don’t have such a species in the Milky Way, because it is much older,” says Smethurst. “It could prove this last bit of this theory of nucleosynthesis — how elements are formed in stars.”

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