Supercomputer Simulations Unravel the Mass Mystery of the Universe’s First Stars

For over a decade, astronomers have been grappling with a cosmic whodunit. Observations suggested the universe's first stars, colossal beings known as Population III stars, were mid-sized, ranging from 12 to 60 times the mass of our Sun. However, computer simulations kept painting a different picture, proposing these stars were much heftier, reaching sizes of up to 1,000 solar masses.

Massive Pop III stars reach the end of their lifecycles through supernova explosions, releasing a torrent of energy and ejecting the first heavy elements into the 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

A new study by Dr. Ke-Jung Chen and Ching-Yao Tang from Academia Sinica's Institute of Astronomy and Astrophysics (ASIAA) is shedding light on this stellar mystery. Utilizing the immense power of a supercomputer at Berkeley National Lab, they've conducted the first-ever high-resolution 3D simulations of the turbulent clouds where these first stars ignited.

The culprit behind the size discrepancy seems to be the wild weather within these star-birthing clouds.

"Our simulations show that supersonic turbulence within these clouds acts like a cosmic sculptor," explains Dr. Chen. "It fragments the gas into clumps of various sizes, destined to become the first stars."

These clumps, according to the simulations, have a mass range of 22 to 175 solar masses, perfectly aligning with the observations of extremely metal-poor stars – the remnants of the universe's earliest explosions.

The research, published in the latest Monthly Notices of the Royal Astronomical Society, goes a step further. By weakening the turbulence in their simulations, the researchers were able to reproduce the results of previous, mass-inflated models. This highlights the crucial role turbulence plays in shaping the birthplaces of the first stars.

"Not only does this reconcile the mass discrepancy, but it also paves the way for future simulations to explore even lower mass ranges for the first stars," concludes Tang.