An international team of astronomers using the James Webb Space Telescope (JWST) located a gargantuan spiral galaxy located about 11.7 billion light-years away. This colossal spiral galaxy, aptly nicknamed “Big Wheel,” is about five times more massive than the Milky Way galaxy.
“This galaxy is spectacular for being among the largest spiral galaxies ever found, which is unprecedented for this early era of the universe,” says Charles (Chuck) Steidel (PhD ’90), the Lee A. DuBridge Professor of Astronomy at Caltech. “Ultimately, this galaxy would have been stripped of gas and would not have survived to the modern day. It is like finding a live dinosaur, before it became extinct.”
Steidel is part of a team of astronomers led by the University of Milano-Bicocca in Italy, and their research was published last month in Nature Astronomy. The research paper, “A giant disk galaxy two billion years after the Big Bang,” outlines how Big Wheel is larger than any other confirmed spiral galaxy of its era, about two billion years following the Big Bang.
“This galaxy is larger than any other kinematically confirmed disks at similar epochs and is surprisingly similar to today’s largest disks with regard to size and mass,” the researchers write. “James Webb Space Telescope imaging and spectroscopy reveal its spiral morphology and a rotational velocity consistent with a local Tully–Fisher relationship. Multiwavelength observations show that it lies in an exceptionally dense environment, where the galaxy number density is more than ten times higher than the cosmic average and mergers are frequent.”
The novel research, highlighted by Space.com, demonstrates evidence that large-disk formation in the early Universe is not only possible but that the conditions may have been more favorable for it than previously realized.
However, this novel discovery was serendipitous. The researchers noticed the strikingly massive spiral galaxy while using Webb to capture images of a nearby quasar, a powerful, active supermassive black hole. The team followed up on the area to learn more about the spiral galaxy, now known as Big Wheel.
“Prior to the discovery, it was thought that disk-shaped galaxies in the early universe were considerably smaller,” Caltech explains. “Big Wheel is about three times larger than any previously discovered galaxies with similar masses at similar cosmic times, and it is also at least three times larger than what is predicted by current cosmological simulations. The galaxy’s radius stretches across 100,00 light-years.”
The team is now grappling with a significant question: How did Big Wheel get so big so fast?
“Exceptionally dense environments such as the one hosting the Big Wheel are still a relatively unexplored territory,” concludes study co-author Sebastiano Cantalupo of the University of Milano-Bicocca. “Further targeted observations are needed to build a statistical sample of giant disks in the early universe and thus open a new window on the early stages of galaxy formation.”
Credits: The relevant research paper, ‘A giant disk galaxy two billion years after the Big Bang,’ was published on March 17, 2025, in ‘Nature Astronomy.’ The paper is authored by Weichen Wang, Sebastiano Cantalupo, Antonio Pensabene, Marta Galbiati, Andrea Travascio, Charles C. Steidel, Michael V. Maseda, Gabriele Pezzulli, Stephanie de Beer, Matteo Fossati, Michele Fumagalli, Sofia G. Gallego, Titouan Lazeyras, Ruari Mackenzie, Jorryt Matthee, Themiya Nanayakkara and Giada Quadri.
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