NASA's James Webb Space Telescope (JWST) has set a new milestone: capturing images of over 40 individual stars in a galaxy so distant that its light has traveled since the universe was only half its current age.
Observing individual stars halfway across the observable universe is generally regarded as impossible in astronomy, akin to trying to use binoculars to see individual grains of dust in the moon's craters. However, due to a remarkable cosmic phenomenon, an international team of astronomers accomplished this seemingly unattainable goal. This groundbreaking discovery is set to change our understanding of the cosmos.
Using JWST data, the astronomers observed a galaxy nearly 6.5 billion light-years from Earth at a time when the universe was half its current age. In this distant galaxy, the team identified many individual stars, which were made visible thanks to an effect known as gravitational lensing and JWST's high light-collecting power.
The paper describing the discovery has been published in Nature Astronomy, is led by Yoshinobu Fudamoto, an assistant professor at Chiba University in Japan and a visiting scholar at University of Arizona's Steward Observatory, and includes Arizona State University co-authors Seth Cohen, Nicholas Foo and Rogier Windhorst.
"I'm amazed at all the different ways gravitational lensing has become a useful tool to study different astrophysical phenomena," said Cohen, an associate research scientist at ASU’s School of Earth and Space Exploration.
The finding marks a record-breaking achievement — the most significant number of individual stars detected in the distant universe. This rare and important event provides an opportunity to investigate one of the universe's greatest mysteries: dark matter.
"When we predicted in 2018 that stars in galaxies at cosmological distances might be observed with Webb individually as they go across these nearly infinite magnification lines (the so-called 'caustics'), I never dreamed of Webb seeing them in such large numbers,'' said Windhorst, an ASU Regents Professor. "And now here we are observing these stars popping in and out of the images taken only a year apart, like fireflies in the night. Webb continues to amaze us all."
Most galaxies, including the Milky Way, contain tens of billions of stars. Astronomers can observe stars one by one in nearby galaxies such as the Andromeda galaxy. However, in galaxies billions of light-years away, stars appear blended together as their light needs to travel for billions of light-years before it reaches us. This presents a long-standing challenge to scientists studying how galaxies form and evolve.
“It was amazing to see the observations taken over time of the Dragon Arc. Stars would appear and disappear from image to image like a twinkling Christmas tree,” said Foo, a graduate research associate at ASU’s School of Earth and Space Exploration.