Lumina Simulation Models Early Universe's Evolution

On October 26, 2026, researchers at the Center for Astrophysics | Harvard & Smithsonian, in collaboration with MIT and other institutions, introduced Lumina, a large-volume radiation-hydrodynamics simulation. This advanced model tracks the early universe from the dark ages to redshift z=3, covering the first 2 billion years of cosmic evolution. Lumina represents a significant step forward in understanding how the universe evolved after the Big Bang, capturing the emergence of structures such as galaxies and stars. The simulation spans a vast area of 500 megaparsecs, or approximately 1.6 billion light-years, offering insights into the processes that shaped the cosmos.

The early universe, following the Big Bang, was initially a hot and dense mixture of particles. As it expanded and cooled, neutral hydrogen formed, creating a shroud that blocked light, leading to a cosmic dark age. Lumina illuminates this period by simulating the processes that eventually resulted in the re-ionization of hydrogen and helium. These pivotal transformations are essential for understanding how the first stars and galaxies emerged, thereby lifting the veil of darkness that enveloped the universe for hundreds of thousands of years.

In the simulation, two major processes are highlighted: hydrogen re-ionization and helium re-ionization. Hydrogen re-ionization occurs when early stars emit ultraviolet light that interacts with neutral hydrogen, stripping it of electrons and allowing light to pass through freely. Lumina captures this phenomenon in remarkable detail. Helium re-ionization, on the other hand, is driven by the intense radiation from supermassive black holes. The simulation provides a comprehensive view of how these processes unfolded across a vast volume of space, marking the first time that both re-ionization events have been simulated together.

The development of Lumina builds upon earlier simulations like IllustrisTNG, enhancing both resolution and volume to track cosmic evolution more effectively. Lumina encompasses half a trillion individual elements, including dark matter particles and gas cells, achieving approximately 30 times higher resolution than prior models. This level of detail allows researchers to compare simulations with observational data from new and future telescopes, advancing our understanding of the universe's formative years and the processes that led to the formation of galaxies and other structures.

As researchers continue to refine Lumina, its significance extends beyond academic inquiry. The simulation serves as a vital tool for the scientific community, enabling comparisons between simulated and observed cosmic structures. By providing insights into the universe's evolution, Lumina contributes to a broader understanding of cosmic history and the fundamental processes that shaped our universe, ultimately paving the way for future discoveries in astrophysics.