Primordial halo simulations reveal how cosmic storms shaped the universe’s first stars

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 groundbreaking 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 were published in 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.

Who’s behind this story?

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries.

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Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language.

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