Simpler models may miss important physics

The results indicate that less detailed models may underestimate how strongly stellar radiation and complex chemical processes affect the gas surrounding galaxies.

By simulating these effects at exceptionally high resolution, the researchers captured structures in the gas that simpler approaches can miss. That added detail could help astronomers make more accurate predictions for observations being collected now and for those planned in the future.

The simulations begin with pristine gas containing no heavy elements, reproducing conditions that existed shortly after the Big Bang. From there, the models follow the formation of the first stars, the radiation those stars release, the supernova explosions that end their lives, and the spread of newly created elements into later generations of stars and galaxies.

Reconstructing this process could help answer one of astronomy's most fundamental questions: where did the elements making up the modern Universe come from?

A physical bridge

"The James Webb Space Telescope gives us a direct glimpse of the infant cosmos, while stellar archaeology allows us to study the relics of those earliest times in our own Galactic neighborhood," said Dr. Martin Rey of the Department of Physics at the University of Bath, a lead contributor to the MEGATRON collaboration. "MEGATRON provides a physical bridge between the two."

Dr. Rey emphasized the stakes: "The elements that make our world and life possible — carbon, oxygen, iron and many others — were forged by stars. To understand where those elements came from, we need to understand how the first stars formed and enriched their surroundings. MEGATRON allows us to test these ideas directly by comparing detailed simulations with observations from JWST and the chemical fingerprints preserved in ancient stars."

These are simulation results, not observations, so their value will depend on how well the models match reality as JWST data and stellar surveys improve. The collaboration is counting on exactly that comparison. JWST continues to reveal new information about some of the earliest known galaxies, while large stellar surveys produce increasingly detailed measurements of ancient stars in and around the Milky Way.

Next-generation simulations

Dr. Rey and his colleagues at Bath are already building the next generation of MEGATRON simulations. The project has received 40 million processor hours on the UK's national supercomputers — computing power equivalent to running five million laptops simultaneously for an entire year.

The additional resources will allow the team to build simulations with even greater resolution and more complete physical models. Researchers will then make increasingly direct comparisons between their simulations, JWST observations, and the chemical fossil record in ancient stars.

"MEGATRON provides a common physical framework for interpreting two of astronomy's most exciting new datasets: JWST's view of the earliest galaxies and the stellar fossil record," said Dr. Rey. "Together, these complementary observations allow us to test competing models of the first stars in ways that weren't previously possible."

The MEGATRON project began in 2023 and is scheduled to continue through 2030.