Galactic archaeologists trace back the origins of the Milky Way, examining the faintest traces of light, gases and matter to determine how, when and why various galactic bodies formed or disappeared. One of the most pressing mysteries in this field is the nature of the first generations of stars – a mystery that is now being probed by a team of American and Italian researchers, with an assist from a pair of supercomputers.

The first generation of stars is almost certainly gone forever, having lasted just a few million years after forming in the aftermath of the Big Bang. When those stars went supernova, however, they released heavier elements that formed the second generation of stars – including stars known as carbon-enhanced metal-poor stars, which the researchers call “living fossils” due to their ability to inform astronomers about the nature of the stars that birthed them.

“We can’t see the very first generations of stars,” said study co-author John Wise, an associate professor at the Center for Relativistic Astrophysics at Georgia Tech, in an interview with Jorge Salazar of the Texas Advanced Computing Center (TACC). “Therefore, it’s important to actually look at these living fossils from the early universe, because they have the fingerprints of the first stars all over them through the chemicals that were produced in the supernova from the first stars.”

To understand the relationship between these living fossils and their forebears, the researchers ran a series of simulations that modeled the first stars at various masses, solved for the radiative transfers as the simulated stars went supernova, and finally modeled the molecular clouds produced by the supernovae. To conduct these experiments, the researchers primarily used their in-house cluster at the Georgia Tech Partnership for an Advanced Computing Environment (PACE) center. 

However, to run the more intensive parts of the simulations, the researchers received a grant through the Extreme Science and Engineering Discovery Environment (XSEDE) that permitted them time on two supercomputers: TACC’s Stampede2 system and the Comet system at the San Diego Supercomputer Center (SDSC).

“The XSEDE systems Comet at SDSC and Stampede2 at TACC are very fast and have a large storage system,” said Gen Chiaki, a postdoctoral researcher at the Center for Relativistic Astrophysics. “They were very suitable to conduct our huge numerical simulations.”

“Because Stampede2 is just so large, even though it has to accommodate thousands of researchers, it’s still an invaluable resource for us,” Wise added. “We can’t just run our simulations on local machines at Georgia Tech.”

The researchers were also granted time on TACC’s larger Frontera system, but Wise says they “haven’t gotten to full steam yet” on Frontera, though they “look forward to using it.”

Already, the simulations have yielded results: first, an initial image of the first stars’ supernovae; and second, signs of “giga-metal-poor” stars that have yet to be observed, but which theoretically may still exist. The researchers are hopeful that in the coming years, they will gain access to even more supercomputers (such as the forthcoming Expanse system at SDSC) and expand their research beyond its current scope.

“We want to enlarge our interest to the other types of stars and the general elements with larger simulations,” Chiaki said.

To read the reporting from TACC’s Jorge Salazar, click here.