The most distant star — or perhaps a pair of stars — astronomers have ever seen has just been revealed thanks to the Hubble telescope and a large cluster of galaxies. Far from Earth, the universe is curved around most of the galaxy clusters, creating a gravitational lens in space-time like the curved lens in a magnifying glass. Like a magnifying glass, it reveals something small and hidden: the star systems of the early universe.
The distant star system takes the official name WHL0137-LS, but the astronomers who discovered it have nicknamed it “Earendel” from an Old English word meaning “morning star” or “rising light.”
The earendel system as we see it today shone in just 900 million years after the Big Bang, according to the authors of a new paper in journal Nature describes the discovery A full 12.8 billion years passed before the light reached the Hubble Space Telescope, magnified by lucky gravitational tricks to appear as tiny photons smudges on the Hubble image sensor. Earendel is 8.2 billion years older than the Sun and Earth and 12.1 billion years older than the first animals on our planet.
Even by ancient stellar standards, Earendel stands out: astronomers observe the previous record holder, nicknamed Icarus, as it appeared 9.4 billion years ago — 3.4 billion years later than the new record holder. Even the oldest known supernovae, usually the brightest and most visible individual objects in the vast space-time, are younger than Earendel.
Seeing through the lens of gravity
Earendel’s home galaxy, the Rising Sun arc, takes its name from the gravitational lensing effect that made this discovery possible.
“This galaxy appears to be enlarged and stretched into a long, thin crescent shape due to the gravitational lensing effect of a large group of galaxies in the foreground,” said Brian Welch, Johns Hopkins University astronomer and lead author of the study. Nature paper.
Welch says The Verge that he discovered Earendel when he studied the gravitational lens itself.
Gravity lenses, like magnifiers, tend to bend and rotate the image and have a higher and lower magnification area. If you have a magnifying glass at home, the best possible magnification in the middle 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, appearing several times. And the closer they are parallel to the curve from our point of view on Earth, the more magnified they are.
:no_upscale()/cdn.vox-cdn.com/uploads/chorus_asset/file/23355420/hubble_earendel_annotated.png)
“I’m modeling the lensing effect of a galaxy cluster, with the goal of measuring the magnification of the Rising Sun Arc,” Welch said. “The model continues to predict that a single bright spot in this arc must have a very high magnification.”
Welch noticed that this bright spot was an object very close to the critical curve — so close and so small that even Hubble’s sharp eye broke the multiple images reflected across the line as a single smudge. The proximity to that critical curve also means that whatever it is, it has been magnified between 1,000 and 40,000 times before reaching Hubble. However small and dim it may appear to Hubble, it is in fact much smaller — tiny on the scale of the Sunrise Arc galaxy.
“When I looked further, I found that the source was too small to be anything other than individual stars (or binary systems),” Welch said.
ancient universe
Welch and a large international team of co-authors spent three and a half years studying Earendel on several Hubble observations to ensure that they were seeing something tangible and not a temporary effect of light.
The time and effort was worth it, Welch said, because these very old stars can teach us a lot about the history of the universe.
“With distant objects, we are looking into the universe’s past and into a time when the universe looked very different from what it is now,” Welch said. “We know that galaxies look different at this early age, and we know that there were only a few generations of stars that appeared before that.”
–
Stars are the factories of heavy elements in our universe, forming when lighter atoms such as hydrogen and helium combine together through nuclear fusion to form heavier matter such as carbon, oxygen, and even iron. Earendel, at an early stage in the history of our universe, probably had very little matter heavier than helium in his system, Welch said.
“Studying this lensed star in detail gives us a new window into what these early stars looked like and how they differed from stars in the nearby universe,” Welch said.
The James Webb Space Telescope (JWST), launched in December 2021, is currently preparing for science operations. Its optics, sharper than Hubble’s, should be able to confirm their conclusion that Earendel is a single star system and not a cluster of star systems put together, the paper’s authors wrote. They also hope to see if Earendel is a solitary star or a binary system, learning more about the temperature and mass of the star, among other properties.
JWST will be busy compiling a scientific wish list that has grown long in the years astronomers have spent anticipating launches, as The Verge previously reported. That would include studying exoplanets as well as the ancient universe – including star systems like Earandel that glow at dawn.
Update 12:07 am ET: This article has been updated with additional images of Earandel and the Rising Sun arc.
–
