For decades, astrophysicists believed the universe’s first stars were cosmic giants: massive, uniformly enormous objects hundreds of times heavier than the Sun, born in calm, quiescent environments. New research published in The Astrophysical Journal turns that picture upside down. The first stars — known as Population III stars — were shaped by violent supersonic turbulence and were far less massive than previously assumed.
The study, led by Meng-Yuan Ho of the Institute of Astronomy and Astrophysics at Academia Sinica in Taipei, Taiwan, used ultra-high-resolution cosmological simulations to peer into the primordial dark matter halos where the very first stars ignited. What the team found was not peaceful. It was chaotic.
A Stormy Birth for the First Stars
Population III stars formed from pristine gas composed almost entirely of hydrogen and helium, roughly 300 million years after the Big Bang. Unlike later generations of stars, they contained no metals — elements heavier than helium — because none had yet been forged in stellar cores. Without metals to help cool the gas, early theoretical models predicted that star-forming clouds needed to reach enormous masses before they could collapse under gravity, producing Population III stars weighing between 40 and 500 solar masses.
But those models assumed a quiet environment. The new research suggests the opposite.
“We find that supersonic turbulence is a common feature of minihalos and plays a key role in producing clumpy star-forming clouds,” Ho and colleagues write in their paper, “Turbulence in Primordial Dark Matter Halos and Its Impact on the First Star Formation.”
The team used simulations based on the IllustrisTNG cosmological framework, enhancing the resolution by a factor of 100,000 to track gas motions on scales smaller than one light-year. They simulated 15 primordial minihalos, the dense pockets of dark matter that served as the first stellar nurseries.
The results revealed a far more dynamic picture. Gas flows into these minihalos through multiple streams, and when those streams collide near the center, they generate intense turbulence. In the simulations, gas velocities reached Mach 1.8 to 4.2 — meaning the gas moved at nearly two to more than four times the speed of sound. Larger halos produced even more extreme speeds.
Instead of collapsing smoothly into a single massive star, this turbulence fragmented the gas into numerous dense clumps. The clumps ranged dramatically in mass, from as little as 2.6 solar masses to as much as 66.5 solar masses, all exceeding the Jeans mass threshold needed for gravitational collapse.
“Our results suggest that supersonic turbulence is a common feature of minihalos and plays a key role in producing clumpy star-forming clouds, with important implications for the initial mass function of the first stars,” the researchers explain.
Solving a Long-Standing Puzzle
The findings help resolve a puzzle that has troubled astronomers for years. If Population III stars were as uniformly massive as previously thought, many of them would have ended their brief lives in powerful supernova explosions, scattering heavy elements across the early universe. The next generation of stars would have incorporated those metals, and astronomers should see clear chemical fingerprints in the oldest stars of the Milky Way.
But the evidence has been ambiguous. Many ancient “fossil” stars in our galaxy preserve chemical signatures that suggest the first stars were less massive than the old models predicted. The new turbulence-driven fragmentation offers a natural explanation: if Population III stars spanned a broader range of lower masses, fewer of them would have exploded as supernovae, and the chemical enrichment of the early universe would have proceeded more gradually.
Broader Implications for the Cosmic Dawn
The findings carry significant implications for our understanding of the early universe and for current observations with the James Webb Space Telescope. The masses of the first stars directly influence the evolution of the first galaxies, the chemical enrichment of intergalactic space, and the heating of surrounding gas that regulates further star formation.
If Population III stars were generally less massive, their feedback on the surrounding environment would have been weaker than expected. This could reshape theoretical models of how the first galaxies formed and evolved during the epoch of reionization, a critical period when ultraviolet light from the first stars and galaxies ionized the neutral hydrogen that filled the cosmos.
The research also highlights the importance of turbulence in cosmic structure formation. What was once seen as a relatively straightforward process — pristine gas collapsing into giant stars — is now understood as a deeply chaotic phenomenon shaped by the same turbulent forces that govern star formation in the present-day universe.
“These simulations show that early structure formation can naturally generate supersonic turbulence, which plays a crucial role in shaping primordial gas clouds and regulating the mass scale of Pop III stars,” the authors conclude.
The study opens a new window into the cosmic dawn. Rather than a serene birth of solitary giants, the universe’s first stars emerged from a storm.