Researchers have released the first major findings from the MEGATRON project, a high-resolution simulation suite that connects James Webb Space Telescope observations of early galaxies with the chemical fossil record of ancient Milky Way stars, explaining how primordial stellar explosions enriched the universe with heavy elements.
Cosmologists modeling the evolution of the early universe have unveiled a new physical bridge connecting two previously separate astronomical views. Published across four papers in the Open Journal of Astrophysics, initial results from the MEGATRON project use advanced cosmological simulations to track how the universe’s very first stars lit up the cosmic dark ages and dispersed heavy elements into their surroundings.
The collaboration began in 2023 and is scheduled to run until 2030, supported by an award of 40 million processor hours on the UK’s national supercomputers. Led by the University of Bath in the United Kingdom, alongside collaborators at the University of Chicago and the Institut d’Astrophysique de Paris, the project combines cutting-edge cosmological models with detailed simulations of radiation, chemistry, and galaxy formation.
MEGATRON Simulations Bridge Telescope Observations and Stellar Archaeology
For years, astronomers studied the infant cosmos through two distinct lenses that rarely intersected directly. Observations from the James Webb Space Telescope provide a direct view of young galaxies. Meanwhile, stellar archaeology examines the chemical clues preserved in ancient stars residing in and around the Milky Way.
The MEGATRON simulations were designed to resolve this gap by tracking the entire lifecycle of pristine gas from the Big Bang through the formation, radiation, and supernova deaths of the earliest stellar generations.
The simulations offer an explanation for this anomaly. According to the calculations, most of these tiny galaxies received their entire metal content from a single explosion of an extremely massive first-generation star.
These first stars, known as Population III stars, were primarily composed of hydrogen and helium. During their lives and supernova deaths, they forged and distributed elements such as carbon, oxygen, and iron. In the simulations, stars with a mass between 160 and 300 times that of the Sun were completely disrupted without leaving a black hole behind, releasing about five solar masses of iron.
Computing High-Resolution Cosmic Models
Executing these calculations required addressing a severe multiscale computational challenge. The dark-matter particle mass is approximately 2.5 × 10⁴ solar masses, while spatial resolution evolves from roughly 2.5 parsecs at z = 25 to approximately 5 parsecs at z = 8.
Rather than treating physical processes in isolation, the simulation solves a tightly coupled chain of equations involving radiative transfer and non-equilibrium chemistry across more than 80 primordial species, molecules, and metal ions. Starlight alters the thermal and chemical state of surrounding gas, which changes gas cooling, which in turn dictates star formation and subsequent supernova feedback.
The findings indicate that simplified cosmological models may underestimate the influence of stellar radiation and complex chemical processes on gas surrounding galaxies. By modeling these dynamics at exceptionally high resolution, the research team captured fine structural details in the gas that simpler approaches miss.
With 40 million processor hours allocated on national supercomputers, the MEGATRON collaboration is already developing the next generation of simulations to strengthen predictions for incoming data and future astronomical observations.