Dragon Arc: Webb telescope captures the most distant stars ever seen

Using the extraordinary capabilities of NASA’s Webb Telescope and the natural phenomenon of gravitational lensing, astronomers have achieved an unprecedented feat: observing individual stars in a galaxy called Dragon Arc that is 6.5 billion light-years away.

This breakthrough offers a unique opportunity to study the evolution of galaxies, the nature of dark matter, and the life cycle of distant stars.

The Dragon Arc

The galaxy, known as the Dragon Arc, was observed along the line of sight to the galaxy cluster Abell 370, which acts as a cosmic magnifying glass. 

The cluster’s gravitational field stretches and amplifies the light from the Dragon Arc, transforming its spiral structure into an elongated arc.

This macrolensing effect enabled astronomers to resolve individual stars in the distant galaxy for the first time.

“Inside the galaxy cluster, there are many stars floating around that are not bound by any galaxy,” explained co-author Eiichi Egami, a research professor at the University of Arizona’s Steward Observatory. 

“When one of them happens to pass in front of the background star in the distant galaxy along the line of sight with Earth, it acts as a microlens, in addition to the macrolensing effect of the galaxy cluster as a whole.”

44 individual stars identified

The study, led by Yoshinobu Fudamoto of Chiba University in Japan, identified 44 individual stars in the Dragon Arc, the largest number ever detected in such a distant galaxy.

These findings represent a significant leap in the study of distant galaxies, where stars typically appear as a blended glow due to the immense distance.

“To us, galaxies that are very far away usually look like a diffuse, fuzzy blob,” said Fudamoto. “But actually, those blobs consist of many, many individual stars. We just can’t resolve them with our telescopes.”

Thanks to JWST’s incredible sensitivity and the combined effects of macro- and microlensing, the team was able to track brightness variations in these stars over time.

These changes occurred because the relative motion of stars in the galaxy cluster altered the alignment and magnification of the distant stars.

Distant stars of the Dragon Arc 

The stars observed within the Dragon Arc were predominantly red supergiants – massive stars nearing the end of their lives, similar to Betelgeuse in the Orion constellation. 

This contrasts with earlier discoveries that primarily identified blue supergiants, thanks to JWST’s ability to detect cooler stars through its infrared capabilities.

“This groundbreaking discovery demonstrates, for the first time, that studying large numbers of individual stars in a distant galaxy is possible,” said Fengwu Sun, a co-author and postdoctoral scholar at the Center for Astrophysics | Harvard & Smithsonian (CfA). 

The ability to identify and study different stellar types provides valuable insights into star formation and the chemical composition of distant galaxies.

Dark matter and galactic evolution

The findings have profound implications for our understanding of the universe. Observing individual stars in distant galaxies allows scientists to probe the structure of gravitational lenses, offering a novel way to study dark matter, which is believed to shape the formation of galaxies. 

Moreover, the alignment of microlensing stars opens a window into the physical properties and behaviors of distant stellar populations.

By studying the brightness and color changes of these stars, astronomers can gain insights into the dynamics of galaxy clusters and the conditions that influence star formation and survival in the early universe.

What happens next?

The Dragon Arc is just the beginning. Future observations using JWST are expected to uncover even more stars in distant galaxies, enabling detailed studies of their life cycles and interactions.

These efforts could yield hundreds of individual stellar profiles, expanding our understanding of galaxy evolution over billions of years.

“By observing the same galaxy multiple times, we can spot stars in distant galaxies because they appear to pop in and out of existence,” Fudamoto explained. 

This technique, combined with the natural magnification effects of gravitational lensing, could revolutionize our approach to studying the cosmos.

Unlocking the mysteries of the universe

This landmark discovery demonstrates the immense potential of JWST and gravitational lensing to push the boundaries of observational astronomy. 

By resolving individual stars billions of light-years away, scientists are unraveling some of the universe’s greatest mysteries, from the nature of dark matter to the intricate dynamics of galactic evolution.

This study, published in the journal Nature Astronomy, paves the way for a deeper exploration of the cosmos, providing a foundation for future studies that will continue to expand humanity’s understanding of our place in the universe.

Image Credit: NASA

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