How astronomers used gravitational lensing to discover 44 new stars in distant galaxy

The most powerful telescope to be launched into space has made history by detecting a record number of new stars in a distant galaxy.

NASA's James Webb Space Telescope, history's largest and most complex space observatory that serves thousands of astronomers around the world, has captured a unique image that revealed 44 individual stars in a galaxy 6.5 billion light-years away from the Milky Way, according to a paper published Monday in Nature Astronomy.

Astronomers used Webb's high-resolution optics and distortion in space to reveal the existence of dozens of previously unknown stars, the researchers said. The detection of a "treasure trove" of stars was only possible because the light from the 44 new stars was magnified by a large cluster of galaxies, called Abell 370, in front of it, according to the Center for Astrophysics.

The technique is known as gravitational lensing, which is when a massive amount of matter -- like a cluster of galaxies -- creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it but in the same line of sight, according to NASA. The effect is essentially like looking through a giant magnifying glass.

The strong gravitational magnification enabled astronomers to detect faint background sources and study their internal structures, which can lead to identifying individual stars in distant galaxies, according to the paper.

Gravitational lensing is also known as the "Einstein Ring" because renowned physicist Albert Einstein predicted the possibility in his theory of general relativity.

A visible arc created by gravitational lensing and the bending of light beyond Abell 370 was dubbed the "Dragon Arc." After carefully analyzing the colors of each of the stars inside the Dragon Arc, the researchers found many are red supergiants, which are stars in their final stages of life.

The discovery contrasts with earlier findings, which predominantly identified blue supergiants, which are among the brightest stars in the night sky, according to the Center for Astrophysics.

In the Milky Way and nearby galaxies, such as the Andromeda Galaxy, astronomers can observe stars one by one. But for galaxies billions of light-years away, the stars appear blended together due to the distance.

"To us, galaxies that are very far away usually look like a diffuse, fuzzy blob," lead author Yoshinobu Fudamoto, an assistant professor at Chiba University in Japan, said in a statement.

The Center for Astrophysics likened the chances of finding individual stars halfway across the observable universe to "raising a pair of binoculars at the moon in hopes of making out individual grains of dust inside its craters." The discovery came by happenstance, as the astronomers were looking for a background galaxy but instead found the individual stars, according to Fengwu Sun, a postdoctoral researcher at the Center for Astrophysics and co-author of the study.

"This groundbreaking discovery demonstrates, for the first time, that studying large numbers of individual stars in a distant galaxy is possible," Sun said. "We now have the capability to resolve stars that were previously outside of our capability."

Launched on Dec. 25, 2021, the Webb telescope orbits the sun about 1 million miles from Earth and gathers data to help astronomers study every phase of the history of the universe, from the Big Bang to the formation of solar systems capable of supporting life, according to NASA.

NASA's Hubble Space Telescope, which orbits Earth, has previously detected seven stars.

The Webb telescope's historic discovery will allow astronomers going forward to investigate "one of the universe's greatest mysteries -- dark matter," according to the Center for Astrophysics.

"Observing more individual stars will also help us better understand dark matter in the lensing plane of these galaxies and stars, which we couldn't do with only the handful of individual stars observed previously," Sun said.

Future Webb telescope observations are expected to capture more magnified stars in the Dragon Arc galaxy, according to the Center for Astrophysics.