The Milky Way may have a twin. The discovery of the most distant spiral galaxy to date may change the way we think about both the speed and process in which such systems are birthed, an international team led by the University of Geneva (UNIGE) reported in the journal Astronomy & Astrophysics.
Astrophysicists have long thought that large spiral galaxies like the Milky Way form over several billion years in a chaotic process and initially form irregular shapes. But the James Webb Space Telescope (JWST) is changing that conception. It is revealing large, well-structured galaxies at much earlier times than anticipated. And its resemblance to the Milky Way is uncanny.
“Its disk spans over 60,000 light-years, comparable to our own galaxy, and contains more than 100 billion solar masses in stars,” Mengyuan Xiao, a research fellow postdoctoral researcher at UNIGE and lead author of the study, said in a press release. “This makes it one of the most compelling Milky Way analogues ever found at such an early time, raising new questions about how massive, well-ordered spiral galaxies could form so soon after the Big Bang.”
Rethinking Galaxy Formation
The newly found galaxy, named Zhúlóng, meaning “Torch Dragon” from Chinese mythology — came into existence a mere billion years after the Big Bang.
“In the myth, Zhúlóng is a powerful red solar dragon that creates day and night by opening and closing its eyes, symbolizing light and cosmic time,’’ Xiao said in the release. “What makes Zhúlóng stand out is just how much it resembles the Milky Way – both in shape, size, and stellar mass.”
Zhúlóng was discovered somewhat serendipitously. The JWST was operating in “pure parallel mode” — meaning that while its main instrument was collecting data from a primary target, its secondary one was scanning the cosmos.
“This allows JWST to map large areas of the sky, which is essential for discovering massive galaxies, as they are incredibly rare,” Christina Williams, an astronomer at NOIRLab and an author of the paper, said in a press release. “This discovery highlights the potential of pure parallel programs for uncovering rare, distant objects that stress-test galaxy formation models.”
Read More: Space Tornadoes Are Swirling Around the Milky Way’s Core
Milky Way Twin Discovery
Discovering Zhúlóng shows that this is a sound strategy. Astronomers will employ the JWST and Atacama Large Millimeter Array (ALMA) observations to learn more about Zhúlóng’s properties as well more details about how it was confirmed.
The discovery of the Milky Way twin shows both the power of new imaging techniques as well as how much about the universe remains a mystery.
Read More: The Heart of the Milky Way May Host a New Form of Dark Matter
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Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
