It has been quite some time since the last record-breaking finding of a distant star.
However, in 2022, astronomers broke all records when they detected a star that existed within the first billion years after the birth of the Universe. It is the most distant known star today.
The unique discovery was made with the Hubble Space Telescope - (Image Credit: Dima Zel via Shutterstock)
The light originating from this star (now dubbed Earendel) took 12.9 billion years to reach us.
During these billions of years, the Universe has expanded so much that the star is now located at a mind-bending comoving distance of 28 billion light-years (or 8.6 billion parsecs) from Earth.
These kinds of distances are hard to wrap your mind around. However, if you'd like to give it a try, be sure to check out our article that attempts to explain cosmic distances from a human point of view.
"We almost didn't believe it at first, it was so much farther than the previous most distant, highest redshift star," said astronomer Brian Welch, lead author of the underlying paper.
Earendel versus Icarus
Earendel, meaning 'morning star,' was discovered using the Hubble Space Telescope. It appeared to astronomers as it did when the Universe was only about 1 billion years old, or 7 percent of its present age.
Earendel is indicated here with an arrow. The entire scene here is observed through a distorted lens established by an enormous galaxy cluster in the intervening space.
It enables the galaxy's features to be observed but also distorts their appearance—an effect known as gravitational lensing, described below
Image Credit: NASA, ESA, B. Welch (JHU), D. Coe (STScI), A. Pagan (STScI) via ESA/Hubble.org - (Click on image to enlarge)
To put into perspective how giant this leap actually is, we need to look at the previous record-breaking discovery dating back to 2018. That discovery focused on a star (dubbed Icarus) that existed when the Universe was 4.4 billion years old or 30 percent of its current age—located about 14 billion light-years from Earth.
"Normally, at these distances, entire galaxies look like small smudges, the light from millions of stars blending together" said Welch. Earendel is located almost double as far away as Icarus. So how did astronomers make such a giant leap compared to a few years ago?
The answer lies with a phenomenon called 'gravitational lensing.' A gravitational lens can be seen as some sort of cosmic magnifying glass. It bends the light from distant objects. Gravitational lenses form due to a distribution of matter (in this case, a huge cluster of galaxies) between a distant light source (in this case, Earendel) and an observer (in this case, the Hubble Space Telescope) that is capable of bending the light from the source as it travels toward the observer.
The galaxy hosting Earendel has been magnified and warped by gravitational lensing into a long crescent that astronomers dubbed the Sunrise Arc.
Earendel is positioned along a ripple in spacetime that gives it extreme magnification, allowing it to emerge into view from its host galaxy, which appears as a red smear across the sky.
The image also shows a cluster of stars that is mirrored on either side of the line of magnification
Image Credit: Science: NASA, ESA, Brian Welch (JHU), Dan Coe (STScI); Image processing: NASA, ESA, Alyssa Pagan (STScI)
The research team estimates that Earendel has at least 50 times the mass of our sun and is millions of times brighter. It means it can contend with the heaviest stars we know. But even such a bright, massive star would be impossible to see at such a great distance without the aid of a gravitational lens caused by a huge cluster of stars that sits between Earendel and us. Astronomers expect Earendel to remain highly magnified for years to come.
Improving our understanding of the history of the Universe
This discovery means we can better understand a still unknown era in the history of our Universe.
As Welch explains: 'Earendel existed so long ago that it may not have had all the same raw materials as the stars around us today.' Further studying it will open up a window onto an era of the Universe that we are still unfamiliar with, but that led to everything we do 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.' Welch said.
Legendary population III stars
Later this year, the recently launched James Webb Telescope will have a look at the Earendel. The hope is that Webb can reveal more information about the distant star, including its age, temperature, mass, and radius.
Suppose further research shows that Earendel is only made up of hydrogen and helium. In that case, it could provide the first evidence for the legendary Population III stars, believed to have been the very first stars to form after the Big Bang...
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