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An international team of astronomers from the University of Arizona's Steward Observatory has made a significant breakthrough by observing individual stars in a galaxy nearly 6.5 billion light-years away. This discovery was achieved using NASA's James Webb Space Telescope (JWST) and an effect known as gravitational lensing, which allowed researchers to see these stars despite the immense distance.

The findings, published in Nature Astronomy, represent the largest number of individual stars detected in such a distant galaxy. This accomplishment provides new opportunities to study dark matter, one of the universe's greatest mysteries.

Lead author Yoshinobu Fudamoto explained, "To us, galaxies that are very far away usually look like a diffuse, fuzzy blob... But actually, those blobs consist of many, many individual stars." The research leveraged gravitational lensing, where massive objects' gravitational fields amplify distant stars' light, making them detectable with instruments like JWST.

The team observed 44 individual stars in the Dragon Arc galaxy behind Abell 370 using images taken by JWST in December 2022 and 2023. Co-author Eiichi Egami noted that unbound stars within the cluster acted as microlenses, enhancing magnification and enabling detection of these distant stars.

Fengwu Sun highlighted this as "a groundbreaking discovery," demonstrating for the first time that large numbers of individual stars can be studied in distant galaxies when nature aligns favorably.

The analysis revealed many red supergiants among these stars. Future observations with JWST are expected to uncover more magnified stars and could provide insights into gravitational lenses' structure and dark matter's elusive nature.

This project received support from organizations including NASA and NSF. Details can be found in the paper "Identification of more than 40 gravitationally magnified stars in a galaxy at redshift 0.725" published in Nature Astronomy.