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Released: June 18, 2026, Academia Sinica Institute of Astronomy & Astrophysics (ASIAA), Taiwan
New simulations reveal that violent turbulence inside primordial dark matter halos fragmented the Universe’s first star-forming clouds
Just a few hundred million years after the Big Bang, the Universe was a dark and simple place. There were no galaxies like the Milky Way, no planets, and no heavy elements such as carbon or oxygen. Instead, vast clouds of primordial hydrogen and helium drifted through space, slowly falling into invisible cocoons of dark matter known as “minihalos.” Within these halos, the very first stars — called Population III stars — were born.
For decades, astronomers believed these first stars formed in relatively calm environments and grew into enormous objects hundreds of times more massive than the Sun. But a ground-breaking study led by Dr. Ke-Jung Chen at Academia Sinica Institute of Astronomy and Astrophysics paints a far more chaotic picture of the infant Universe.
Using ultra-high-resolution cosmological simulations, Chen’s team discovered that primordial gas inside early dark matter halos was far from quiet. Instead, the gas was stirred into violent supersonic turbulence — cosmic storms moving faster than the speed of sound. These turbulent flows fragmented the gas into many dense clumps, dramatically changing the conditions under which the first stars formed. The results have been published in the latest issue of The Astrophysical Journal.
The simulations followed the evolution of 15 primordial minihalos formed around 13 billion years ago, when the Universe was less than 300 million years old. To capture these tiny structures in unprecedented detail, the researchers enhanced the resolution of large cosmological simulations by a factor of 100,000, allowing them to trace turbulent gas motions down to scales smaller than a light-year.
The results reveal that gas streaming into the gravitational wells of dark matter halos naturally generates turbulence. As multiple gas flows collide near halo centers, they create swirling, chaotic motions with Mach numbers between 2 and 5 — meaning the gas was moving several times faster than the local speed of sound. In some regions, the supersonic turbulence became even more extreme.
Rather than collapsing smoothly into a single giant star, the turbulent gas fragmented into multiple dense clumps. Some of these clumps contained only a few solar masses, while others reached tens of solar masses before collapsing under their own gravity. This suggests that the first stars may have been smaller and more diverse than previously thought.
These findings could help explain long-standing mysteries in astronomy. Ancient “fossil” stars observed today in the Milky Way preserve the chemical fingerprints of the first supernova explosions. Surprisingly, many of these signatures imply that the first stars were less massive than older theories predicted. The newly discovered turbulence-driven fragmentation offers a natural explanation for this discrepancy.
The study also has important implications for modern observations with the James Webb Space Telescope. Although individual first stars are too faint and distant to detect directly, their masses strongly influence the evolution of the first galaxies and the chemical enrichment of the early Universe. Understanding how these primordial stars formed is therefore essential for interpreting observations of the cosmic dawn.
In essence, the research suggests that the first stellar nurseries in the Universe were not serene cradles, but turbulent environments filled with powerful shocks and chaotic gas motions. These primordial cosmic storms may have played a decisive role in shaping the very first generation of stars — and ultimately the galaxies, planets, and life that followed.
Gas streams into minihalos along intricate cosmic flows. As these streams collide and converge at the halo center, they feed dense clumps and stir up powerful turbulence in the surrounding gas. Image Credit: ASIAA/Meng-Yuan Ho
The maps reveal the chaotic weather inside three primordial halos near the end of the simulations. Regions where different gas motions overlap mark zones of intense turbulence, where cosmic gas is being violently stirred. Much of the gas moves faster than the speed of sound, creating powerful supersonic flows, and these cosmic storms become even stronger in larger halos. Together, these swirling and converging motions reveal how streams of infalling gas collide and interact, especially in the crowded central regions where the first stars are beginning to take shape. Image Credit: ASIAA/Meng-Yuan Ho
Deep inside one of the mini halos, two glowing islands of dense gas stand out amid the turbulent primordial cloud. These structures are sculpted by violent supersonic motions — cosmic storms that churned the gas in the Universe’s earliest star-forming regions. As the clumps continue to gather material from their surroundings, they are expected to collapse and ignite the next generation of the first stars. Their final masses may set the limits on how large these ancient stars can grow. Image Credit: ASIAA/Meng-Yuan Ho & Pei-Cheng Tung
More Information:
This research presented in a paper “Turbulence in Primordial Dark Matter Halos and Its Impact on the First Star Formation" by Ho et al. has appeared in the Astrophysical Journal on June 18, 2026.
Media Contact:
Dr. Ken Chen Email: kjchen@asiaa.sinica.edu.tw Tel: +886 2 2366 5457
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