The James Webb Space Telescope (JWST) has marked a major achievement with the start of the new year. It captured images of 44 individual stars in a galaxy halfway across the observable universe. This remarkable feat was made possible by a rare cosmic alignment. It allowed astronomers to identify stars in a region previously thought impossible to resolve. The comparison has been made to spotting dust grains inside craters on the moon using binoculars.
“I never dreamed of Webb seeing them in such large numbers,” said Rogier Windhorst, an astronomer at Arizona State University and part of the discovery team. “Now we are observing these stars popping in and out of images taken only a year apart, like fireflies in the night. Webb continues to amaze us all.”
This discovery not only highlights the telescope’s capabilities but also offers a unique chance to study dark matter’s elusive behavior.
The Largest Star Collection in a Distant Galaxy
The 44 stars are the largest group of individual stars ever observed in the distant universe. They belong to a hidden galaxy whose light has been distorted into a long structure called “the Dragon.” Light from this galaxy began traveling about 6.5 billion years ago, when the universe was half its current age. By analyzing the colors of these stars, astronomers found they are red supergiants nearing the end of their lives. These stars resemble Betelgeuse, a well-known star in Orion’s constellation that may explode as a supernova.
A Cosmic Illusion: The Dragon and Abell 370
The Dragon is actually a collection of several duplicate images of a single spiral galaxy in the background. This cosmic mirage was caused by the galaxy’s alignment behind the Abell 370 galaxy cluster. Abell 370 is located 4 billion light-years away in the constellation Cetus. It contains several hundred galaxies bound together by gravity. The cluster also magnifies and distorts light from far-off galaxies, turning them into detectable arcs and wisps. These effects allow telescopes like the JWST to observe distant galaxies in much greater detail.
Discovering the Stars
The discovery was made by Fengwu Sun, a postdoctoral scholar at the Center for Astrophysics | Harvard & Smithsonian. While analyzing JWST images of the Dragon taken in 2022 and 2023, Sun noticed something unusual. “When we processed the data, we realized there were many individual star points,” he said. “It was exciting because it was the first time we saw so many individual stars so far away.”
Gravitational Lensing: A Helping Hand
Even with the JWST’s advanced technology, detecting so many bright stars would have been challenging. A coincidental alignment of “floating stars” within Abell 370 magnified the stars in the hidden galaxy. This gravitational lensing effect caused the stars to appear and disappear across images. “The stars’ brightness changes made them look like a twinkling Christmas tree,” explained Nicholas Foo, a co-author from Arizona State University.
Published Findings
The findings were published on January 6 in the journal Nature Astronomy. Researchers believe these observations will deepen our understanding of gravitational lensing. They also showcase the groundbreaking capabilities of the JWST, setting the stage for further discoveries of gravitational lensing, underscoring the groundbreaking capabilities of the JWST.
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