Scientists from the Harvard-Smithsonian Center for Astrophysics have created the Lumina simulation, one of the largest and most detailed computer models of the early Universe. The work was published in the journal Monthly Notices of the Royal Astronomical Society. The model recreates the first 2 billion years of cosmic history and shows how ordinary matter, dark matter and radiation interacted.
The main goal is to help astronomers understand data coming from the James Webb and Nancy Roman space telescopes. By comparing observations with Lumina's predictions, researchers will be able to determine how correct current theories of the Universe's evolution after the Big Bang are.
Lumina is the largest cosmological simulation to date that accounts simultaneously for hydrodynamics (the motion of gas) and radiation. It models how gas, dark matter and light interact to form stars and galaxies. Previous similar models covered a volume of space more than 100 times smaller. The new simulation describes a region in the form of a cube about 1.5 billion light-years across, roughly the scale accessible to modern telescopes.
For the first time in such a model, it was possible to reproduce helium reionization, the process in which helium atoms lost electrons under the influence of radiation, and to immediately account for its effect on the evolution of the Universe within the calculation. Previously this had been achieved only for hydrogen.
"With Lumina, for the first time we can trace how both hydrogen and helium transitioned to their modern state over such an enormous volume while preserving the detail of galaxies and other luminous objects," noted one of the authors of the work, Aaron Smith of the University of Texas at Dallas.
The calculation used the Frontier supercomputer, located at Oak Ridge National Laboratory (Tennessee). This made it possible to simulate an unprecedentedly large volume of the early Universe without losing detail.
The authors emphasize that Lumina is not a discovery but a tool for testing hypotheses. In the future, it is planned to use it to study the movement of gas between galaxies, the influence of Big Bang radiation on cosmic evolution, and the formation of regions of intense star formation. If observations match the model's predictions, this will strengthen existing theories; if not, scientists will have reason to revise them.