Record-Breaking View: Webb Uses Physics Trick to Spot 44 Distant Stars in a Galaxy Far, Far Away (Image Credit: Gizmodo-com)
The Webb Space Telescope captured a record-breaking image of stars in the Dragon Arc, a serpentine crescent of a galaxy in the distant universe.
The galaxy is a whopping 6.5 billion light-years from Earth and Webb’s recent snapshot of it captures 44 individual stars, seen thanks to the telescope’s remarkable capabilities and the fortuitous layout of objects between the telescope and the galaxy. Let us explain.
The Dragon Arc is just that—a bent strip of light in space—because its light is flattened by the gravity of intervening objects. Those intervening objects are gravitational lenses, which bend and refocus the light from more distant objects, magnifying them to an observer (in this case, the Webb Space Telescope).
Lens within a lens
In a recent study, a group of astronomers scrutinized Webb observations of a galaxy cluster and well-known gravitational lens known as Abell 370. The cluster magnified the distant stars by approximately 100 times, and a star within the cluster acted as a lens within that lens, making the distant stars come into sharper relief. The team’s research describing the target stars was published this week in Nature Astronomy.
“Inside the galaxy cluster, there are many stars floating around that are not bound by any galaxy,” said Eiichi Egami, a research professor at Steward Observatory and co-author of the paper, in an Arizona State University release. “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 microlensing effect of the galaxy cluster as a whole.”
New possibilities
The lensception, if you will, made it possible for the research team to pick out individual stars which otherwise would have been too fuzzy to make out. The team studied the stars and concluded that “many of them are consistent with red giants or supergiants magnified by factors of hundreds,” as the group wrote in the paper.
“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 researcher at the Center for Astrophysics | Harvard & Smithsonian, in the release.
Such red stars are nearing the end of their lives. As the stars use up their fuel, they swell and offload reams of gas and dust. Webb is no stranger to such ancient stars; in 2022 and 2023, the state-of-the-art observatory trained its eye on Earendel, the most distant known star, and found signs that the ancient ball of gas may have a partner in crime.
Discovering a single distant star is remarkable on its own. In November 2024, astronomers captured the first detailed image of a star outside our galaxy—a red supergiant in its final stages of life. But a whole collection of stars is more scientifically useful. As the team wrote, the work demonstrates that “observations by the Webb Space Telescope could lead to the possibility of conducting statistical studies of high-redshift stars.”
Astronomers will conduct follow-up observations of the arc with the Webb telescope, which are expected to reveal more of the magnified stars within the distorted galaxy. Besides helping scientists understand how different gravitational lenses magnify ancient light, the findings could reveal aspects of dark matter.
