April 13, 2024

Supercomputer simulations decode the mass puzzle of the first stars

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Huge Pop III stars reach the end of their life cycles through supernova explosions, releasing a torrent of energy and ejecting the first heavy elements into surrounding space. This process chemically enriches the once-primordial gas, fundamentally altering the conditions for subsequent star formation in the early universe. Credit: ASIAA/Ke-Jung Chen

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Huge Pop III stars reach the end of their life cycles through supernova explosions, releasing a torrent of energy and ejecting the first heavy elements into surrounding space. This process chemically enriches the once-primordial gas, fundamentally altering the conditions for subsequent star formation in the early universe. Credit: ASIAA/Ke-Jung Chen

Ching-Yao Tang and Dr. Ke-Jung Chen of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) have made substantial progress in decoding the birth mass of the first stars using Berkeley National Laboratory’s powerful supercomputer.

This new research is reported in the latest issue of Monthly Notices of the Royal Astronomical Society.

During the early stages of the universe, only hydrogen and helium existed after the Big Bang, and elements crucial to sustaining life, such as carbon and oxygen, had not yet emerged. Approximately 200 million years later, the first stars, known as Population III (Pop III) stars, began to form.

These stars began producing heavier elements through nuclear burning in their cores. As these stars reached the end of their life cycles, some went supernova, creating powerful explosions that dispersed newly synthesized elements in the early universe, becoming the basis for life.

The type of supernova that occurs depends on the mass of the first star at its disappearance, resulting in different patterns of chemical abundance. Observations of extremely metal-poor (EMP) stars, formed after the first stars and their supernovae, were crucial in estimating the typical mass of the first stars. Observationally, the elemental abundance of EMP stars suggests that the first stars had masses ranging from 12 to 60 solar masses.


The image shows the cosmological structure during the period of the first star formation, about 200 million years after the Big Bang. The gray structures illustrate the distribution of dark matter when the first stars form within some dark matter halos. The colored spots represent stars with varying masses, providing a visual representation of the complex processes that shaped the early universe. Credit: ASIAA/ Ke-Jung Chen

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The image shows the cosmological structure during the period of the first star formation, about 200 million years after the Big Bang. The gray structures illustrate the distribution of dark matter when the first stars form within some dark matter halos. The colored spots represent stars with varying masses, providing a visual representation of the complex processes that shaped the early universe. Credit: ASIAA/ Ke-Jung Chen


During the formation of the cosmic structure, primordial gas flows into gravity wells created by dark matter halos. As the flowing gas converges toward the center of the halo, it begins a powerful turbulent motion. This intense turbulence acts to shake the cloud, giving rise to distinct agglomerated structures, as described above. Ultimately, the dense cores within these clusters undergo gravitational collapse, marking the formation of the first stars. Credit: ASIAA/Ching-Yao Tang

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During the formation of the cosmic structure, primordial gas flows into gravity wells created by dark matter halos. As the flowing gas converges toward the center of the halo, it begins a powerful turbulent motion. This intense turbulence acts to shake the cloud, giving rise to distinct agglomerated structures, as described above. Ultimately, the dense cores within these clusters undergo gravitational collapse, marking the formation of the first stars. Credit: ASIAA/Ching-Yao Tang







However, previous cosmological simulations have proposed a heavier, more widely distributed mass function for the first stars, ranging from 50 to 1,000 solar masses. This significant mass discrepancy between simulations and observations has perplexed astrophysicists for more than a decade.

Ching-Yao Tang and Ke-Jung Chen used Berkeley National Lab’s powerful supercomputer to create the world’s first high-resolution 3D hydrodynamic simulations of turbulent star-forming clouds for the first stars. Their results indicate that supersonic turbulence effectively fragments star-forming clouds into multiple clusters, each with dense cores ranging from 22 to 175 solar masses, destined to form the first stars with masses of about 8 to 58 solar masses that agree well. with observation. .

Additionally, if turbulence is weak or unresolved in simulations, researchers can reproduce similar results from previous simulations. This result highlights for the first time the importance of turbulence in the formation of the first stars and offers a promising path to downscaling the theoretical mass of the first stars. It successfully reconciles the mass discrepancy between simulations and observations, providing a solid theoretical basis for the first star formation.

More information:
Ching-Yao Tang et al, Clumpy structures within the turbulent primordial cloud, Monthly Notices of the Royal Astronomical Society (2024). DOI: 10.1093/mnras/stae764

Diary information:
Monthly Notices of the Royal Astronomical Society

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