Summary Points
Lumina simulates two billion years, capturing hydrogen and helium reionization.
Early stars drove hydrogen reionization; black holes powered helium reionization.
It models half a trillion elements across volumes 100 times larger than predecessors.
Researchers can use Lumina to compare cosmic predictions with telescope observations.
A new view of the early universe
For hundreds of millions of years after the Big Bang, neutral hydrogen filled the universe and blocked much of its light. A new simulation called Lumina follows how that darkness lifted — and how the first galaxies, stars and black holes reshaped the cosmos.
Across two billion years of cosmic history, Lumina models two major changes. Early stars and galaxies produced ultraviolet light that stripped electrons from hydrogen, allowing light to travel more freely. Later, intense radiation from actively feeding supermassive black holes ionized helium. The simulation captures both processes together, offering a detailed way to study how the first cosmic structures formed.
Big scale, significant computing demands
Lumina combines an upgraded galaxy-formation model with calculations of how radiation travels through space. It tracks about half a trillion elements across a region roughly 500 megaparsecs wide. That is 100 times the volume of previous leading simulations, with about 30 times the resolution of its predecessor.
The scale comes at a cost. Researchers ran Lumina on the Frontier supercomputer, using the equivalent of more than 100,000 CPU cores and about 15,000 GPUs at peak. That computing demand makes the project a major technical achievement, but also underscores how difficult it is to repeat or expand such work.
The team is making the simulation available to scientists, who can compare its predictions with observations from current and future telescopes. Lumina does not replace those observations: Its results depend on the physical models and starting conditions built into the simulation. But by linking small-scale star formation with changes across vast regions of space, it gives researchers a powerful tool for testing ideas about the universe’s early history.
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