Astronomers using the NASA/ESA/CSA James Webb Space Telescope have discovered an ultra-massive grand-design spiral galaxy that existed just one billion years after the Big Bang. Named Zhúlóng (Torch Dragon), this galaxy is the most distant bulge-disk galaxy candidate with spiral arms known to date.
This image of Zhúlóng, the most distant spiral galaxy discovered to date, shows its remarkably well-defined spiral arms, a central old bulge, and a large star-forming disk, resembling the structure of the Milky Way. Image credit: NASA / CSA / ESA / M. Xiao, University of Geneva / G. Brammer, Niels Bohr Institute / Dawn JWST Archive.
Large spiral galaxies like our Milky Way are expected to take several billion years to form.
During the first billion years of cosmic history, galaxies are thought to be small, chaotic, and irregular in shape.
However, Webb is beginning to reveal a very different picture.
The telescope’s deep infrared imaging is uncovering surprisingly massive and well-structured galaxies at much earlier times than previously expected — prompting astronomers to reassess how and when galaxies take shape in the early Universe.
Among these new findings is Zhúlóng, the most distant spiral galaxy candidate identified to date, seen at a redshift of 5.2.
Despite this early epoch, the galaxy exhibits a surprisingly mature structure: a central old bulge, a large star-forming disk, and spiral arms — features typically seen in nearby galaxies.
“What makes Zhúlóng stand out is just how much it resembles the Milky Way — both in shape, size, and stellar mass,” said Dr. Mengyuan Xiao, a postdoctoral researcher at UNIGE.
“Its disk spans over 60,000 light-years, comparable to our own Galaxy, and contains more than 100 billion solar masses in stars.”
“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.”
The Zhúlóng galaxy was discovered as part of the PANORAMIC survey.
“This discovery highlights the potential of pure parallel programs for uncovering rare, distant objects that stress-test galaxy formation models,” said Dr. Christina Williams, an astronomer at NOIRLab and principal investigator of the PANORAMIC program.
Spiral structures were previously thought to take billions of years to develop, and massive galaxies were not expected to exist until much later in the Universe, because they typically form after smaller galaxies merged together over time.
“This discovery shows how Webb is fundamentally changing our view of the early Universe,” said Professor Pascal Oesch, an astronomer at UNIGE and co-principal investigator of the PANORAMIC program.
A paper on the discovery was published today in the journal Astronomy & Astrophysics.
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Mengyuan Xiao et al. 2025. PANORAMIC: Discovery of an ultra-massive grand-design spiral galaxy at z ~ 5.2. A&A 696, A156; doi: 10.1051/0004-6361/202453487
