(Cape Canaveral) Astronomers have found the farthest star ever observed from Earth, a super-hot, super-bright giant that formed nearly 13 billion years ago at the dawn of the cosmos.
Posted at 1:39 p.m.
But this luminous blue star no longer exists, since it was so massive that it most likely exploded only a few million years after its birth. Its brief existence makes it all the more remarkable that it was detected by an international team based on observations made by the Hubble Space Telescope. The light emitted by distant stars takes an unimaginable time to reach us.
“We see the star as it existed about 12.8 billion years ago, or about 900 million years after the Big Bang,” said Brian Welch, a PhD student at Johns Hopkins University who is the lead author of the study published Wednesday by the prestigious scientific journal Nature.
“We were certainly lucky,” he added.
He dubbed the star Earendel, an Old English word meaning morning star ― “an apt name for a star we observe at a time often called the ‘cosmic dawn’.”
The star that was previously the oldest to be known, Icarus, had also been spotted by Hubble. It was formed 9.4 billion years ago, more than four billion years after the Big Bang.
In both cases, the astronomers used a technique called the “gravitational lensing effect” to amplify the very low light. The gravity of galaxy clusters closer to us ― in the foreground ― serve as a lens to magnify smaller objects in the background. Otherwise, Icarus and Earendel would remain invisible due to their gigantic distance.
If Hubble has seen galaxies that formed 300 or 400 million years after the Big Bang, their individual stars are impossible to discern.
“Unless they’re stuck on top of each other… But here nature has given us a star ― very, very magnified thousands of times ― for us to study,” said Jane Rigby, a NASA astrophysicist. who participated in the study. It’s such a beautiful gift from the universe. »
Vinicius Placco of the National Science Foundation called the discovery “fantastic”. He did not take part in the study.
Based on the Hubble data, Placco said, Earendel could very well belong to the first generation of stars born after the Big Bang. Upcoming observations by the brand new James Webb Space Telescope should provide more detail, he added, and “provide us with a new piece of this cosmic puzzle that is the evolution of our universe”.
Current data indicates that Earendel was more than 50 times larger than our sun and up to a million times brighter, dwarfing Icarus. The small, immature Earendel galaxy looked nothing like spiral galaxies photographed elsewhere, Welch said, but more like a “gross object”.
Unlike Earendel, he said, this galaxy likely survived, but in a different form after merging with other galaxies.
“It’s like a little snapshot of the past,” said M.me Rigby.
Earendel was possibly the dominant star in a system that had two, or three, or four, Welch said. There’s a slim chance it could be a black hole, although observations made in 2016 and 2019 don’t point in that direction.
No matter who its neighbors were, the star only survived a few million years before exploding and morphing into a supernova that went unnoticed, as it often does. The most distant supernova observed by astronomers is 12 billion years old.
The Webb Telescope, which is a hundred times more powerful than Hubble, should help clarify just how massive and hot this star is, and tell us a bit more about its galaxy.
In studying the stars, said Mr.me Rigby: “We literally understand where we come from since we are partly made of this stardust. »