Astronomers Discover Most Distant Milky Way-like Galaxy

In a discovery that could reshape our understanding of how galaxies form and evolve, astronomers have identified the most distant spiral galaxy candidate ever observed—a vast, mature system that existed just one billion years after the Big Bang.

The galaxy, named Zhúlóng, was found by an international team led by the University of Geneva (UNIGE) using data from the James Webb Space Telescope (JWST).

Despite its ancient origins, Zhúlóng displays features typically associated with much later cosmic periods: a central old bulge, a large star-forming disk, and clearly defined spiral arms—hallmarks of spiral galaxies like our own Milky Way.

“We named this galaxy Zhúlóng, meaning ‘Torch Dragon’ in Chinese mythology. 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,” paper author and UNIGE astronomer Mengyuan Xiao said in a statement.

“What makes Zhúlóng stand out is just how much it resembles the Milky Way—both in shape, size and stellar mass.”

The galaxy spans more than 60,000 light-years across and contains over 100 billion solar masses in stars, making it one of the most compelling analogues of the Milky Way ever found from such an early era.

How the Galaxy Was Found

Zhúlóng was identified through deep imaging gathered during the JWST’s PANORAMIC survey (GO-2514), an extragalactic observation program designed to explore large regions of the distant Universe.

The survey takes advantage of JWST’s “pure parallel” observation mode, where multiple instruments operate simultaneously to collect more data.

“This allows JWST to map large areas of the sky, which is essential for discovering massive galaxies, as they are incredibly rare,” astronomer Christina Williams of NOIRLab, said in a statement.

“This discovery highlights the potential of pure parallel programs for uncovering rare, distant objects that stress-test galaxy formation models.”

Until recently, it was widely believed that large spiral galaxies like the Milky Way required several billion years to take shape, with early galaxies thought to be small, irregular, and turbulent. Discoveries like Zhúlóng are prompting scientists to reconsider long-standing assumptions about cosmic evolution.

“This discovery shows how JWST is fundamentally changing our view of the early Universe,” Pascal Oesch, associate professor at UNIGE said in a statement.

Zhúlóng’s redshift of 5.2 places it at just one billion years after the Big Bang, a time when the Universe was less than 10 percent of its current age. Its presence suggests that some galaxies may undergo extremely rapid growth and organization, challenging old theories that rely on gradual assembly through mergers and chaotic interactions.

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Reference

Xiao, M., Williams, C. C., Oesch, P. A., Elbaz, D., Dessauges-Zavadsky, M., Marques-Chaves, R., Bing, L., Ji, Z., Weibel, A., Bezanson, R., Brammer, G., Casey, C., Cloonan, A. P., Daddi, E., Dayal, P., Faisst, A. L., Franx, M., Glazebrook, K., Hutter, A., … Whitaker, K. E. (2025). PANORAMIC: Discovery of an ultra-massive grand-design spiral galaxy at z ∼ 5.2. Astronomy & Astrophysics, 696, A156. https://doi.org/10.1051/0004-6361/202453487