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The Hubble Space Telescope has caught a glimpse of the most distant single star it has ever observed, shining 28 billion light-years away. And the star could be 50 to 500 times more massive than our sun and millions of times brighter.
It is the most distant detection of a star so far, since 900 million years after the Big Bang. Astronomers have nicknamed the star Earendel, derived from an Old English word meaning “morning star” or “rising light.”
A study detailing the findings published Wednesday in the journal Nature.
This observation breaks the record set by Hubble in 2018 when it observed a star that existed when the universe was around four billion years old. Eärendel is so far away that starlight has taken 12.9 billion years to reach us.
This Eärendel observation could help astronomers investigate the early years of the universe.
“As we look at the cosmos, we’re also looking back in time, so these extremely high-resolution observations allow us to understand the building blocks of some of the earliest galaxies,” said study co-author Victoria Strait, a postdoctoral researcher at Cosmic. Dawn Center in Copenhagen, in a statement.
“When the light we see from Eärendel was emitted, the Universe was less than a billion years old; only 6% of his current age. At the time it was 4 billion light-years from the proto-Milky Way, but during the nearly 13 billion years it took for light to reach us, the Universe has expanded so that it is now an astonishing distance from Earth. 28,000 million light years.
All the stars we see in the night sky exist in our own galaxy, the Milky Way. Incredibly powerful telescopes can only see individual stars within the closest galaxies. But distant galaxies look like a blur of mixed light from the billions of stars they contain.
But gravitational lensing, which was predicted by Albert Einstein, makes it possible to look deeper into the distant universe. Gravitational lensing occurs when closer objects act like a magnifying glass for distant objects. Gravity essentially warps and magnifies the light from distant background galaxies.
When light passes near massive objects, it follows a curve around that object. If that object is between Earth (or in this case, Hubble) and the distant light source, it can actually deflect and send the light our way, acting like a lens to increase its intensity.
Many distant galaxies have been found in this way.
In this case, the alignment of a massive cluster of galaxies acted like a magnifying glass and intensified Eärendel’s light thousands of times. This gravitational lensing, combined with nine hours of observing time at Hubble and an international team of astronomers, created the unprecedented image.
“Normally, at these distances, entire galaxies look like little specks, with light from millions of stars mixing together,” lead author Brian Welch, an astronomer at Johns Hopkins University in Baltimore, said in a statement. “The galaxy that hosts this star has been magnified and distorted by gravitational lensing into a long crescent we call the Arc of Dawn.”
To make sure that it really is a single star, rather than two located very close to each other, the research team will use the recently launched James Webb Space Telescope to observe Eärendel. Webb could also reveal the star’s temperature and mass.
“With James Webb, we will be able to confirm that Earendel is indeed just a star, and at the same time quantify what kind of star it is,” said study co-author Sune Toft, leader of the Cosmic Dawn Center and Niels professor. Copenhagen Bohr Institute, in a statement. “Webb will even allow us to measure its chemical composition. Potentially, Eärendel could be the earliest known example of the first generation of stars in the Universe.”
Astronomers want to know more about the star’s composition because it formed shortly after the universe began, long before the universe became filled with heavy elements created by the death of massive stars.
Webb could reveal whether Earendel is made up largely of primordial hydrogen and helium, making it a Population III star, the stars that are supposed to exist shortly after the Big Bang.
“Earendel existed so long ago that it may not have had all of the same raw materials as the stars that surround us today,” Welch said. “Studying Eärendel will be a window into an era of the universe that we are not familiar with, but which led to everything we know. It is as if we have been reading a really interesting book, but we start with the second chapter and now we will have the opportunity to see how it all began.”
And the Webb Telescope can help astronomers find even more distant stars than Hubble can find.
“With Webb, we can see stars even farther away than Earendel, which would be incredibly exciting,” Welch said. “We will go as far back as we can. I would love to see Webb break the Eärendel distance record.”