A new computer simulation called Lumina models the universe from 50 million to 200 million years after the Big Bang, charting how the first stars and black holes helped bring an end to the cosmic dark ages. The work was published in the November issue of the Monthly Notices of the Royal Astronomical Society.
The cosmic dark ages began after the universe cooled enough for electrons to combine with hydrogen and helium, forming neutral gas. With no stars or galaxies yet producing light, the early cosmos entered a dark period that scientists understand less fully than the Big Bang and its immediate aftermath.
Lumina follows the epoch of reionization, when radiation stripped electrons from hydrogen and helium. The process unfolded unevenly: early stars could ionize hydrogen and remove one electron from helium, while radiation from developing supermassive black holes was needed to remove helium’s second electron. The simulation shows ionized bubbles growing around large structures while broad regions remained neutral.
Researchers say Lumina is among the largest and most detailed simulations of this period. It spans 1.5 billion light-years on each side and includes 200 million galaxies, while allowing researchers to examine the development of individual galaxies. Its volume is more than 100 times that of comparable simulations, according to the project’s statement.
The team used the Frontier supercomputer at Oak Ridge National Laboratory to create the model. The project required about 600 terabytes of memory and took roughly six months to run. Its scale and detail are intended to help scientists test theories against observations from the James Webb Space Telescope and the Nancy Grace Roman Space Telescope.
Lead author Oliver Zier, a computational astrophysicist at the Center for Astrophysics, Harvard & Smithsonian, said comparing telescope observations with simulations could help researchers investigate the unexpectedly large number of bright galaxies seen in the early universe. JWST can examine individual objects in detail, while Roman is expected to survey much larger areas of sky and find broader samples of rare, bright galaxies.
Lumina builds on earlier computer models of the cosmos, including IllustrisTNG, which provided a foundation for the project. The researchers hope the simulation will help astronomers better understand how the first luminous structures formed and how the universe emerged from its long period of darkness.
Sources: Smithsonian Magazine.