A giant wheel surrounded by its neighbors. (Photo credit: Weichen Wang et al. (2025), CC BY-NC-ND 4.0)
Deep observations using the James Webb Space Telescope (JWST) have revealed an incredibly large galaxy that existed in the early universe. This cosmic giant emits light that has been traveling toward us for more than 12 billion years. We call it the Great Wheel, and our findings were published March 17 in the journal Nature Astronomy.
This colossal disk galaxy existed during the first two billion years after the Big Bang, meaning it formed when the universe was just 15% of its current age. Its discovery challenges our understanding of how galaxies form.
What is a disk galaxy?
Imagine a galaxy like our Milky Way: a flat, rotating structure of stars, gas, and dust, often surrounded by a vast halo of invisible dark matter.
Disk galaxies typically have distinct spiral arms extending from a dense central region. Our Milky Way is itself a disk galaxy, with beautiful spiral arms that wrap around its center.
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Studying disk galaxies like the Milky Way and the recently discovered Great Wheel helps us understand how galaxies form, evolve, and develop over billions of years.
These studies are especially important because understanding galaxies like ours can provide deeper insights into the cosmic history of our galactic home.
Amazing discovery
Previously, it was believed that galactic disks formed gradually over a long period of time: either through a slow influx of gas from the surrounding space or through mergers with smaller galaxies.
Typically, rapid galaxy mergers disrupt delicate spiral structures, turning them into more disordered shapes. However, the Big Wheel managed to quickly grow to an impressive size without losing its characteristic spiral shape, challenging traditional ideas about the growth of giant galaxies.
Our detailed observations with JWST show that the Big Wheel is comparable in size and rotation speed to the largest “superspiral” galaxies observed in the modern Universe. It is three times larger in size than similar galaxies of that era, and is one of the most massive galaxies detected in the early cosmos.
In fact, its rotation speed places it among galaxies at the upper end of the so-called Tully-Fisher relation, a well-known relationship between a galaxy's stellar mass and its rotation speed.
Remarkably, despite its extraordinary size, the Great Wheel is actively growing at a rate comparable to other galaxies of the same cosmic age.
Sourse: www.livescience.com
