In a discovery that’s turning heads and rewriting textbooks, an international team of astronomers has uncovered an enormous spiral disk galaxy that existed just 2.4 billion years after the Big Bang. This giant—nicknamed the Big Wheel—is not only a marvel of early cosmic engineering but also three times larger than any other known disk galaxy from the same ancient era.
Published in Nature Astronomy, this landmark discovery was made possible by the extraordinary capabilities of NASA’s James Webb Space Telescope (JWST). It offers a rare glimpse into how galaxies assembled themselves in the chaotic, gas-rich environment of the early universe. The team behind the find includes scientists from Australia’s Swinburne University of Technology, with galaxy spectral modeling expert Dr. Themiya Nanayakkara playing a key role.
And here’s why this discovery is making cosmologists sit up and take notice: according to existing models of galaxy formation, there shouldn’t be something like the Big Wheel—at least, not at this time in the universe’s history.
Galaxies: Cosmic Cities in Motion
Galactic disks are vast, pancake-shaped structures made of stars, dust, and gas, all orbiting a central core. Our own Milky Way is a textbook example of this elegant cosmic architecture. These disks rotate like giant wheels, with stars—including our sun—riding the spiral arms as they move through space.
But how these galactic disks formed, especially in the early universe, has been one of astronomy’s great unsolved mysteries. Most simulations suggest that these structures should take billions of years to stabilize, slowly accumulating gas and stars in ordered rotations. So how did the Big Wheel manage to grow so large, so early?
A Giant Galaxy From a Younger Universe
Dr. Nanayakkara and his colleagues spotted the Big Wheel while targeting a specific slice of deep space—a region that also hosts a bright quasar located at redshift z=3.25. In simpler terms, this galaxy appears as it was about 11 billion years ago, when the universe was just 20% of its current age.
“Seeing a massive, well-ordered disk galaxy when the universe was just 2.4 billion years old forces us to rethink how rapidly and efficiently nature can build cosmic structures,” Dr. Nanayakkara said.
The Big Wheel’s optical radius stretches a staggering 10 kiloparsecs (kpc), making it at least three times larger than theoretical models predict for galaxies of this epoch. That’s about 32,600 light-years across—similar to some of the largest galactic disks we see in the modern universe.
How Did They Find It?
Thanks to the JWST’s advanced instruments—NIRCam and NIRSpec—the team was able to observe faint galaxies at incredible distances with unmatched clarity. Using this data, they identified a group of galaxies within this densely packed region of the universe and analyzed their redshifts (which tell us their distance and age), their shapes, and most importantly, their kinematics.
It was through these detailed kinematic measurements that they found the Big Wheel’s disk was rotating at roughly 300 kilometers per second. That’s faster than most cars on Earth by several orders of magnitude—and fast enough to confirm it as a mature, rotating disk galaxy.
What Makes This Galaxy So Special?
What truly sets the Big Wheel apart isn’t just its size or speed. It’s the environment it’s living in. The galaxy exists within an extremely dense region of the early universe—one that’s brimming with galaxies, quasars, gas flows, and black holes. Astronomers call these regions proto-clusters, the building blocks of the modern-day galaxy clusters we see today.
Such dense environments might actually help galaxies grow faster. Dr. Nanayakkara suggests that the Big Wheel’s neighborhood could have provided it with a constant supply of cold gas to fuel star formation, allowing the disk to expand rapidly.
But this idea presents a problem. Current simulations and galaxy formation models don’t predict this kind of behavior. Why? Because typically, when galaxies merge or collide—something common in dense areas—the resulting gravitational chaos often destroys or disrupts disk structures. Yet here, in this cosmic metropolis, the Big Wheel not only survived but thrived.
“These favorable physical conditions are likely not fully captured yet in current galaxy formation models,” Dr. Nanayakkara explained. “In order to have a disk form early and grow quickly, galaxy mergers in this environment must have been non-destructive and oriented in particular directions. Alternatively, gas inflows must have carried angular momentum that largely co-rotated with the galaxy disk.”
Rewriting the Rules of Cosmic Evolution
The discovery of the Big Wheel hints at a missing piece in the cosmic puzzle. If such massive disks can form so early, astronomers need to rethink how galaxies grow and evolve. It’s possible that dense environments in the early universe acted as galactic nurseries, churning out large, well-ordered structures far faster than we thought possible.
Previous studies of this region had already shown that the quasar at its center sits inside a vast proto-cluster—a kind of embryonic galaxy cluster filled with raw cosmic material. Now, with the Big Wheel added to the picture, scientists are realizing just how fertile this corner of the universe was for early galaxy formation.
What’s Next?
This discovery is just the beginning. According to Dr. Nanayakkara, the team hopes to conduct more targeted observations of similar over-dense regions to see if the Big Wheel is an outlier—or the first example of a much more common phenomenon.
“With more targeted observations, we could build a statistical sample of giant disks in the early universe and open up a new window on the study of early phases of galaxy formation,” he said.
If they find more galaxies like the Big Wheel, it could radically shift our understanding of the early cosmos. Scientists may need to refine their models to account for how galaxies assemble and survive in extreme environments.
The Power of the James Webb Space Telescope
None of this would have been possible without the James Webb Space Telescope. Launched in December 2021, JWST has already begun to transform our understanding of the universe. Its ability to peer deep into cosmic history—further and with greater precision than any telescope before it—is unlocking secrets long hidden in the light of ancient galaxies.
Using its NIRCam and NIRSpec instruments, JWST can not only capture incredibly sharp images of distant galaxies but also analyze their chemical compositions, movement, and even the dynamics of their star formation.
In the case of the Big Wheel, JWST’s powerful infrared vision allowed astronomers to see light that had been traveling for more than 11 billion years. That light told the story of a galaxy far larger and more sophisticated than anyone expected to find from such an early time in the universe’s history.
A Cosmic Wheel That Keeps on Turning
The Big Wheel isn’t just another galaxy—it’s a challenge to everything we thought we knew about how galaxies form and grow. It stands as a cosmic testament to the universe’s ability to surprise us and serves as a reminder that even our best models are still works in progress.
As telescopes like JWST continue to survey the skies, we can expect many more discoveries that will challenge our assumptions and push the boundaries of cosmic knowledge. But for now, the Big Wheel is turning our understanding of the early universe in a whole new direction—and astronomers around the world are eager to follow where it leads.
Key Takeaways:
- The Big Wheel galaxy was discovered using JWST and exists 11 billion years in the past.
- It’s three times larger than similar galaxies from the same cosmic era.
- Its size and structure defy current models of galaxy formation.
- The galaxy resides in an extremely dense, gas-rich environment that may have fueled its rapid growth.
- This discovery could pave the way for a new understanding of how galaxies formed in the early universe.
The universe has always been a place of mysteries—but thanks to discoveries like the Big Wheel, we’re getting closer to understanding how our cosmic home came to be.
Reference: Weichen Wang et al, A giant disk galaxy two billion years after the Big Bang, Nature Astronomy (2025). DOI: 10.1038/s41550-025-02500-2