Hubble reveals the most distant star ever detected

The most distant star — or possibly a few stars — astronomers have ever seen has just been revealed thanks to the Hubble telescope and a massive cluster of galaxies. Far from Earth, the universe curves around the vast majority of a cluster of galaxies, creating a space-time gravitational lens similar to the curved lens in a magnifying glass. Like a magnifying glass, it revealed something small and hidden: a galaxy from the early Universe.

The distant galaxy is officially named WHL0137-LS, but the astronomers who found it nicknamed it “Earendel” from the Old English word meaning “morning star” or “rising light.”

The Earendel system as we see it today shone within just 900 million years of the Big Bang, according to the authors of a new newspaper in the magazine Nature description of the discovery. It took 12.8 billion years for that light to reach the Hubble Space Telescope, magnified by a lucky trick of gravity to appear as a tiny speck of photons on Hubble’s image sensor. Earendel is 8.2 billion years older than the Sun and Earth and 12.1 billion years older than the first animals of our planet.

Even by old star standards, Earendel stands out: Astronomers observed the previous record holder, nicknamed Icarus, as he looked 9.4 billion years ago – 3.4 billion years more recent than this new record holder. Even the oldest known supernovae, usually the brightest and easiest to spot individual objects in vast spacetime, are younger than Earendel.

An image of Icarus, the previous record holder for the farthest individual star ever seen. The left image shows the huge cluster of galaxies that lies between Earth and Icarus. From NASA: “The panels on the right show the view in 2011, with no Icarus visible, compared to the brightening of the star in 2016.”
NASA, ESA and P. Kelly (University of Minnesota)

Looking through the gravitational lens

Earendel’s home galaxy, the Sunrise Arc, takes its name from the gravitational lensing effect that made this discovery possible.

“This galaxy appears enlarged and stretched into a long, thin crescent shape because of the gravitational lensing effect of a huge foreground galaxy cluster,” said Brian Welch, a Johns Hopkins University astronomer and lead author of the study. Nature paper.

Welch told The edge that he encountered Earendel while studying the gravitational lens itself.

Gravity lenses, such as magnifiers, tend to distort and warp images and have areas of higher and lower magnification. If you have a magnifying glass at home, the best magnification is probably in the center of a simple circle. Gravity lenses are more difficult to use.

In a gravitational lens, there is a line called the “critical curve” where the magnification is strongest. Objects seen through the lens are reflected across the critical curve and appear multiple times. And the closer they are to the line of the curve from our perspective on Earth, the bigger they get.

An annotated image showing Earendel in relation to the sunrise arc
Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)

“I modeled the lens effects of the galaxy cluster to measure the magnification of the Sunrise Arc,” Welch said. “The models continued to predict that this single bright point on the arc would have extremely high magnification.”

Welch realized that this bright point was an object very closely aligned with the critical curve — so close and so small that even Hubble’s keen eye resolved its doubled, reflected image across the line as a single smear. That proximity to the critical curve also meant that whatever it was, it had already been magnified somewhere between 1,000 and 40,000 times before it reached Hubble. As small and dim as it seemed to Hubble, it was in fact much smaller – small on the scale of the Sunrise Arc galaxy.

“As I looked more closely at it, I found that the source was too small to be anything other than an individual star (or binary system),” Welch said.

The old universe

Welch and a large international team of co-authors spent three and a half years studying Earendel using multiple Hubble observations to confirm that they were seeing something real and not a transient effect of light.

The time and effort was worth it, Welch said, because these very old stars can teach us about the history of the universe.

“With distant objects, we are looking into the past of the universe and at a time when the universe looked very different than it does now,” Welch said. “We know that galaxies look different at this early time, and we know that there have been relatively few generations of stars.”

Stars are the factories of heavy elements in our universe, formed when lighter atoms like hydrogen and helium fuse together through nuclear fusion to form heavier material like carbon, oxygen and even iron. Earendel, at that early stage in our universe’s history, probably had very little material heavier than helium in his system, Welch said.

“By studying this lensed star in detail, we gain a new understanding of what stars looked like in these early days and how they differ from stars in the nearby universe,” Welch said.

The James Webb Space Telescope (JWST), launched in December 2021, is currently gearing up for science operations. The optics, sharper than Hubble’s, should confirm their conclusion that Earendel is a single star system and not a cluster of galaxies clustered together, the authors wrote in the paper. They also hope to see whether Earendel was a lone star or a binary, and learn about the star’s temperature and mass, among other properties.

JWST will be busy working its way through a scientific wish list that has grown long in the years astronomers have spent anticipating the launch, such as The edge Previously reported. That includes studying exoplanets and the ancient universe — including galaxies like Earandel that glowed at the dawn of time.

Update 12:07 PM ET: This article has been updated to include an additional image of Earandel and the Sunrise arc.

SOURCE – www.theverge.com

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