The supercomputer has solved the mystery related to the mass of the first stars

The universe is an ever-expanding entity that started small with a few stars. The question that still preoccupies astronomers is: How massive were those first primordial stars? Taiwanese scientists have now made significant progress in these calculations with the help of an American supercomputer.

Shortly after the Big Bang, there was only hydrogen and helium. In the early stages of the universe, the essential elements for life, such as carbon and oxygen, had not yet appeared. About 200 million years later, the first stars began to form.

Foundation for life
Tertiary stars, or Tertiary pop stars, as they were called, eventually created heavier elements through nuclear combustion in their cores. Near the end of their life cycles, some of those first stars turned into supernovas. The resulting powerful explosions spread new elements into the early universe, which would form the basis for life.

The type of supernova formed at that time depends on the mass of the first star when it died. Thus different chemical patterns emerged. Observations of extremely metal-poor stars, which formed after the first stars and their supernovae, were previously crucial for estimating the masses of the first stars. Based on the large number of metal-poor stars, it has been estimated that the first stars had masses equivalent to twelve to sixty solar masses.

The gap between simulation and observation
However, previous cosmological simulations suggested a heavy, widely distributed higher mass for the first stars, ranging from fifty to a thousand solar masses. This dramatic discrepancy between simulations and observations has been a mystery to astronomers for at least a decade.

To find a solution, two scientists from Taiwan worked with the powerful supercomputer at Berkeley National Laboratory. They have succeeded, for the first time ever, in developing high-resolution 3D hydrodynamic simulations of turbulent star-forming clouds that preceded the first stars.

Disturbances during star formation
Results In particular: supersonic turbulence, or intense chaotic motion, caused the star-forming clouds to disintegrate into several masses, each with a dense core ranging from 22 to 175 solar masses. The first stars from this formed with masses ranging from 8 to 58 solar masses and this is consistent with observations.

Furthermore, researchers can reproduce similar results from previous simulations, even if the disturbance is weaker. This result demonstrates the importance of turbulence in early star formation and provides a promising way to reduce the theoretical scale of the mass of the first stars. The discrepancy between simulations and observations has now been resolved, creating a solid theoretical foundation for the formation of the first stars.

the big explosion
Although we don't know for sure, we assume that the universe was created about 13.8 billion years ago from a so-called singularity, a very hot spot of almost infinite density. This uniqueness was not subject to the known laws of nature, and space and time did not exist. After the Big Bang, space and time were created and the universe began expanding and we are still in the middle of it. In those early days of the universe, it was completely dark. Only about 200 million years later did the first stars begin to form. These first generation stars are called Population III stars. They emerged from primordial clouds of hydrogen and helium along with trace amounts of lithium. Only a few million years later they exploded and became supernovas. All the heavier chemical elements, such as nitrogen, carbon, oxygen, and iron, were formed in the core of this and subsequent stars. Only in 2015 did the European Space Agency's Very Large Telescope find evidence of the existence of these primordial stars, for which there had only been theoretical arguments until then.