BALTIMORE, Maryland (AP) — Astronomers have discovered the farthest star yet, a super-hot, super-bright giant that formed nearly 13 billion years ago at the dawn of the cosmos.
An international team spotted it with observations by the Hubble Space Telescope.
“We’re seeing the star as it was about 12.8 billion years ago, which puts it about 900 million years after the Big Bang,” says astronomer Brian Welch, a doctoral student at Johns Hopkins University and lead author of the study appearing in Wednesday’s journal Nature.
But this luminous blue star is long gone, so massive that it almost certainly exploded into bits just a few million years after emerging.
“We have been working under the assumption that the light we’re seeing is just from one massive star. And with that assumption, it works out that it would have to be at least 50 times the mass of the Sun. So it’s a really big, really massive star, which is not unheard of within the local universe,” says Welch.
Its swift demise makes it all the more incredible that an international team spotted it with observations by the Hubble Space Telescope.
He nicknamed it Earendel, an Old English name that means morning star or rising light.
The previous record-holder, Icarus, also a blue supergiant star spotted by Hubble, formed 9.4 billion years ago. That’s more than 4 billion years after the Big Bang.
In both instances, astronomers used a technique known as gravitational lensing to magnify the minuscule starlight.
Gravity from clusters of galaxies closer to us – in the foreground – serve as a lens to magnify smaller objects in the background.
If not for that, Icarus and Earendel would not have been discernible given their vast distances.
While Hubble has spied galaxies as far away as 300 million to 400 million years of the universe-forming Big Bang, their individual stars are impossible to pick out.
Current data indicate Earendel was more than 50 times the size of our sun and an estimated 1 million times brighter, outsizing Icarus.
Earendel’s small, yet-to-mature home galaxy looked nothing like the pretty spiral galaxies photographed elsewhere by Hubble, according to Welch, but rather “kind of an awkward-looking, clumpy object.”
Unlike Earendel, he said, this galaxy probably has survived, although in a different form after merging with other galaxies.
Earendel may have been the prominent star in a two-star, or binary, system, or even a triple- or quadruple-star system, Welch said. There’s a slight chance it could be a black hole, although the observations gathered in 2016 and 2019 suggest otherwise, he noted.
Regardless of its company, Earendel lasted barely a few million years before exploding as a supernova that went unobserved as most do, Welch said. The most distant supernova seen by astronomers to date goes back 12 billion years.
Earendel’s own supernova explosion would have taken out any smaller companion stars and orbiting planets. Welch doubts it had planets – similarly, massive stars in our own Milky Way don’t, after all, and the early universe would have had fewer ingredients to make planets.
NASA and the European Space Agency’s Webb telescope – Hubble’s successor launched in December -will take aim at Earendel in the next year or so to determine its chemical makeup and temperature. Webb also will scour ever more distant galaxies in hopes of zooming in on ever more distant stars.
“And then as far as beating that distance record, there are a few programs with Webb that are looking to observe a bunch of galaxy clusters looking for similar objects at greater distances. So I’m kind of hoping that it (the record) doesn’t stand too long and kind of I’m excited to find ever more distant objects, so I’m really looking forward to the chance that something good can break this record,” says Welch.