BALTIMORE — An enormous star that’s now 28 billion light years away is the oldest ever to be detected, say astronomers. Over fifty times bigger than the Sun, its light has only just reached Earth. We are seeing it around 900 million years after the Big Bang.
The star, dubbed “Earendel,” or “morning star” in Old English, could help explain the evolution of the universe. Researchers say that the light took 12.9 billion years to reach Earth, but it would take more than double that now due to the expansion of the universe.
“When the light that we see from Earendel was emitted, the Universe was less than a billion years old; only 6% of its current age. At that time it was 4 billion lightyears away from the proto-Milky Way, but during the almost 13 billion years it took the light to reach us, the Universe has expanded so that it is now a staggering 28 billion lightyears away,” explains Victoria Strait, postdoc at the Cosmic Dawn Center in Copenhagen, and a collaborator and co-author of the study, in a statement.
Scientists are calling describing the discovery “extraordinary new benchmark” for astronomers. “It’s kind of like finding an old photograph of your great-grandparents,” says co-author Dr Selma de Mink, of the Max Planck Institute for Astrophysics, Germany. “These stars are basically our ‘stellar ancestors’. We are, after all, made out of the elements they once produced. Yet we have so many unanswered questions.”.
The observations – based on data collected by Hubble – are a huge leap further back in time.
“This might be the earliest star we will ever see since the Big Bang,” says co-author Dr. Guillaume Mahler, of Durham University. “It was so surprising. It is so much younger than the previous entry of nine billion years, at first I didn’t believe it.”
It is believed to be one of the most massive stars out there, millions of times brighter than our own. Even so, Earendel would be impossible to spot at such a great distance without the aid of a huge cluster of galaxies that sit in its path. They warp the fabric of space, creating a powerful natural magnifying glass that distorts and greatly amplifies the light from distant objects behind.
“Gravitational lensing is like observing galaxies under the microscope and with technology such as the Hubble telescope, you start to see what is inside,” says Mahler.
Thanks to the rare alignment Earendel appears virtually directly on a “ripple,” providing maximum illumination. It pops out from the general glow of its home galaxy, its brightness magnified by a factor of thousands. The effect is similar to little waves on the surface of a swimming pool – creating patterns of light on the bottom. They act as lenses, focusing sunlight.
“We almost didn’t believe it at first – it was so much farther than the previous most distant star,” says lead author Brian Welch, a PhD student at Johns Hopkins University in Baltimore, per NASA. “Normally at these distances, entire galaxies look like small smudges. This galaxy has been magnified and distorted by gravitational lensing into a long crescent that we named the ‘Sunrise Arc’. Studying Earendel will be a window into an era of the universe that we are unfamiliar with – but that led to everything we know. It’s like we’ve been reading a really interesting book but we started with the second chapter – and now we will have a chance to see how it all got started.”
Earendel will remain highly magnified for years to come as its infrared light is stretched by the universe’s expansion. NASA’s recently launched James Webb Space Telescope (JWST) is highly sensitive to these longer wavelengths.
“With Webb we expect to confirm Earendel is indeed a star – as well as measure its brightness and temperature,” says co-author Dr. Dan Coe, of the Space Telescope Science Institute in Baltimore. “We also expect to find the Sunrise Arc is lacking in heavy elements that form in subsequent generations of stars. This would suggest Earendel is a rare massive metal-poor star.”
Precise details of the star remain uncertain, something the authors say JWST will determine in the future.
“Most exciting for me is some of the black holes recently detected by gravitational waves are remnants of stars that lived back then,” adds Dr. De Mink. “I hope Earendel and future similar discoveries will help us understand a little more about the origin of these black holes.”
The researchers findings are published in the journal Nature.
South West News Service writer Mark Waghorn contributed to this report.