CAPE CANAVERAL, Fla. ( Associated Press) – Astronomers have discovered the farthest star yet, a super-hot, super-bright giant that formed nearly 13 billion years ago with the advent of the cosmos.
But this light blue star is long gone, so massive that it almost certainly exploded into pieces just a few million years after it appeared. Its rapid demise makes it all the more incredible that an international team spotted it with observations through the Hubble Space Telescope. It takes centuries before light emitted by distant stars reaches us.
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“We see the star as it was about 12.8 billion years ago, which puts it about 900 million years after the Big Bang,” said astronomer Brian Welch, a doctoral student at Johns Hopkins University and lead author of the study, released Wednesday. ‘s journal Nature.
“We were definitely just happy.”
He called it Earendel, an Old English name meaning morning star or rising light – “an appropriate name for a star we observed at a time often referred to as ‘Cosmic Dawn’.”
The previous record holder, Icarus, also a blue supergiant star spotted by Hubble, formed 9.4 billion years ago. It is more than 4 billion years after the Big Bang.
In both cases, astronomers have used a technique known as gravitational lensing to magnify the minuscule starlight. Gravity from groups of galaxies closer to us – in the foreground – acts as a lens to magnify smaller objects in the background. Had it not been for that, Icarus and Earendel would not have been visible given their great distances.
While Hubble galaxies have spied as far as 300 million to 400 million years from the universe-forming Big Bang, their individual stars are impossible to choose from.
“Usually they were all suffocated together … But here nature has given us this one star – high, highly magnified, magnified by factors of thousands – so that we can study it,” said NASA astrophysicist Jane Rigby, who participated to study. “It really is such a gift from the universe.”
Vinicius Placco of the National Science Foundation’s NOIRlab in Tucson, Arizona, described the findings as “incredible work.” He was not involved in the study.
Placco said based on the Hubble data, Earendel was possibly among the first generation of stars born after the Big Bang. Future observations by the newly launched James Webb Space Telescope should provide more detail, he said, and “provide us with another piece of this cosmic puzzle that is the evolution of our universe.”
Current data suggest that Earendel was more than 50 times the size of our sun and an estimated 1 million times brighter, which Icarus was larger. Earendel’s small, still-to-mature home galaxy looked nothing like the beautiful spiral galaxies photographed elsewhere by Hubble, according to Welch, but rather “kind of an awkward, lumpy object”. Unlike Earendel, he said, this galaxy probably survived, albeit in a different form after it merged with other galaxies.
“It’s like a little screenshot in amber of the past,” Rigby said.
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Earendel may have been the prominent star in a two-star, or binary system, or even a three- or four-star system, Welch said. There is a slim chance it could be a black hole, although the observations collected in 2016 and 2019 suggest otherwise, he noted.
Regardless of his company, the star barely lasted a few million years before exploding as a supernova that was not observed like most, Welch said. The farthest supernova ever seen by astronomers goes back 12 billion years.
The Webb Telescope – 100 times more powerful than Hubble – should help explain how massive and hot the star really is, and reveal more about its parent galaxy.
By studying stars, Rigby said, “We literally understand where we come from, because we are made up of some of that star dust.”