Using the natural effects of a cosmic phenomenon, an international team of astronomers managed to break through the limitations of traditional astronomy, allowing them to detect “a treasure trove” of giant stars in a galaxy previously too distant to observe accurately.
The study, published in the journal Nature Astronomy, was described as a “groundbreaking discovery.”
Most galaxies contain tens of billions of stars, all of which can easily be individually observed using the right equipment. However, no matter how strong the telescope, beyond a certain range—think billions of light-years away—stars lose definition because of the immense distance their light has to travel before reaching Earth.
“To us, galaxies that are very far away usually look like a diffuse, fuzzy blob,” lead study author Yoshinobu Fudamoto of the Chiba University in Japan said. “But actually, those blobs consist of many, many individual stars. We just can’t resolve them with our telescopes.”
As a result, astronomers were typically able to identify just one or two stars per distant galaxy, Fudamoto said.
Using a particular quirk of nature called “gravitational lensing,” the team was able to successfully overcome the long-standing challenge to make sense of the fuzzy imagery.
As correctly predicted by Albert Einstein, gravitational lensing is a visual magnification effect caused by the strong gravitational fields of massive cosmic objects.
These gravitational lenses can amplify the light of distant stars by hundreds or even thousands of factors, making them observable with sensitive instruments like NASA’s James Webb Space Telescope (JWST).
The Dragon Arc
The Dragon Arc, a galaxy 6.5 billion light-years away from Earth, was an ideal object of study as it is located behind a massive cluster of galaxies called Abell 370.
Abell 370’s huge mass forms an ideal gravitational lens in front of the Dragon Arc and allows for a stunning find.
While previous studies with the Hubble Space Telescope found around seven stars in Dragon Arc—in itself an exceptional find—Fudamoto and his team were able to detect no less than 44 stars, setting the record of individual stars spotted in a single distant universe.
“This groundbreaking discovery demonstrates, for the first time, that studying large numbers of individual stars in a distant galaxy is possible,” said Fengwu Sun, one of the co-authors of the study.
Abell 370’s gravitational lens worked fine, even though it stretches the Dragon Arc’s image into an elongated shape “like a hall of mirrors of cosmic proportions,” the Center for Astrophysics (CFA), a cooperative research institute of the Harvard College Observatory and the Smithsonian Astrophysical Observatory, said in a news release.
“When we processed the data, we realized that there were what appeared to be a lot of individual star points,” Sun said. “It was an exciting find because it was the first time we were able to see so many individual stars so far away.”
The stars were found to be hundreds of times bigger than red giants or supergiant stars. Red giants typically range between 20 to 100 times the size of the sun, while supergiants may be up to 1,000 times the size of our sun.
Beyond Counting Stars
Because light takes 6.5 billion years to travel from the Dragon Arc to Earth, the study provides important insight into the state of the universe at half of its estimated age.
“We can use the knowledge we’ve gained from studying red supergiants in the local universe to interpret what happens next for them at such an early epoch of galaxy formation in future studies,” Sun said.
But the study carries an even greater promise, as a more detailed look into our universe’s past could shed light on the nature of dark matter and provide a better understanding of the structure of gravitational lenses.
The CFA expects future JWST observations to reveal more magnified stars in the Dragon Arc—and in many other galaxies.