The James Webb Space Telescope observed 272 galaxies from about 800 million to 1.5 billion years after the Big Bang and found most were chaotic and turbulent rather than orderly rotating disks. JWST’s NIRCam tracked ionized hydrogen and revealed multidirectional gas flows, shocks and clumps driven by intense starbursts, dense inflows of intergalactic gas and active central black holes. Most objects were low mass (≈100 million–10 billion M☉); a few larger outliers already showed more coherent rotation. Results, published Oct. 22 in MNRAS, agree with theoretical predictions and will be followed by studies of cold gas and dust to trace their evolution.
JWST Reveals the Universe’s First Galaxies Were Chaotic, Turbulent Systems
The James Webb Space Telescope observed 272 galaxies from about 800 million to 1.5 billion years after the Big Bang and found most were chaotic and turbulent rather than orderly rotating disks. JWST’s NIRCam tracked ionized hydrogen and revealed multidirectional gas flows, shocks and clumps driven by intense starbursts, dense inflows of intergalactic gas and active central black holes. Most objects were low mass (≈100 million–10 billion M☉); a few larger outliers already showed more coherent rotation. Results, published Oct. 22 in MNRAS, agree with theoretical predictions and will be followed by studies of cold gas and dust to trace their evolution.
07:11, 04.11.2025Science
Early galaxies were a 'hot mess'
A new study using the James Webb Space Telescope (JWST) suggests that the universe’s first galaxies were far from the calm, orderly disks we see in the nearby cosmos. Instead, these primordial systems were chaotic, turbulent bundles of gas driven by rapid star formation, powerful inflows of intergalactic gas, and energetic activity from central black holes.
What the team observed
Led by Lola Dunhaive of Cambridge University, the team used JWST’s NIRCam instrument to observe 272 small galaxies whose light began its journey when the universe was about 800 million to 1.5 billion years old. By tracking the motion of ionized hydrogen gas, they found that in most galaxies the gas did not revolve smoothly around a single axis. Rather, it flowed in many directions, producing turbulent eddies, shock fronts and clumpy structures instead of an orderly rotation.
“Early galaxies were more turbulent, less stable, and grew up through bursts of star formation,” said Sandro Tacchella, a Cambridge astronomer and coauthor on the study.
Why they were so messy
Several factors contributed to the disorder. Newborn stars generate strong stellar winds and intense ultraviolet radiation that disturb their natal gas clouds. Star formation in these systems often occurred in violent, irregular bursts, amplifying chaos. In addition, the universe was denser at that time, so streams of intergalactic gas more readily fed young galaxies, sometimes in rapid inflows that stirred turbulence. Central supermassive black holes, actively accreting gas, also ejected jets and radiation that further disturbed their hosts.
Most of the galaxies in the sample were relatively low mass—roughly 100 million to 10 billion solar masses—so these processes had an outsized effect on their stability. (By comparison, the Milky Way’s mass is on the order of 1–1.5 trillion solar masses.) A few larger objects in the sample already showed more coherent rotation, suggesting that mass and early growth history can help a galaxy stabilize sooner than others.
Context and next steps
The observations probe an era near the end of Cosmic Dawn and approaching the buildup toward Cosmic Noon, when star-formation rates across the universe surged. The study’s results align with theoretical models and simulations that predicted early galaxies would be turbulent and clumpy rather than well-ordered.
Dunhaive and collaborators plan to combine these measurements of hot, ionized hydrogen with upcoming observations that trace cold gas and dust in the same systems. That multi-phase view should clarify how turbulent, early galaxies gradually settled into the thinner, rotating disks and graceful spirals that dominate the modern universe.
Publication: The team published their results on Oct. 22 in the journal Monthly Notices of the Royal Astronomical Society.