Astronomers using the James Webb Space Telescope have found that the universe's first galaxies were turbulent and disorderly, far from the stable structures seen today. Led by University of Cambridge researchers, the study examined over 250 galaxies from when the universe was 800 million to 1.5 billion years old. These findings challenge prior views and show a transition from cosmic chaos to ordered formation.
The James Webb Space Telescope (JWST) has provided unprecedented insights into the early universe, revealing that galaxies formed just a few hundred million years after the Big Bang were highly unstable and filled with gas clumps rather than smooth, rotating disks like the Milky Way.
A team from the University of Cambridge analyzed over 250 youthful galaxies existing between 800 million and 1.5 billion years after the Big Bang. By tracking gas movement, they determined most were turbulent, undergoing rapid star formation and mergers. The research, published in Monthly Notices of the Royal Astronomical Society, used JWST's NIRCam instrument in grism mode to capture faint light from ionized hydrogen gas. First author Lola Danhaive developed software to interpret this data alongside other JWST surveys.
"We don't just see a few spectacular outliers -- this is the first time we've been able to look at an entire population at once," said Danhaive from Cambridge's Kavli Institute for Cosmology. "We found huge variation: some galaxies are beginning to settle into ordered rotation, but most are still chaotic, with gas puffed up and moving in all directions."
Co-author Dr. Sandro Tacchella noted, "Previous results suggested massive, well-ordered disks forming very early on, which didn't fit our models. But by looking at hundreds of galaxies with lower stellar masses instead of just one or two, we see the bigger picture, and it's much more in line with theory. Early galaxies were more turbulent, less stable, and grew up through frequent mergers and bursts of star formation."
The study bridges the epoch of reionization and cosmic noon, the peak of star formation, illustrating how chaotic clumps evolved into ordered structures. Data came from the JWST Advanced Deep Extragalactic Survey (JADES), supported by the Royal Society, European Union, and UK Research and Innovation. JWST is a collaboration between NASA, ESA, and the Canadian Space Agency.
"This work helps bridge the gap between the epoch of reionisation and the so-called cosmic noon," Danhaive added. Future observations of cold gas and dust will deepen understanding of these early systems.