Supercomputer Simulation Maps Universe’s First 2 Billion Years

Scientists have developed a supercomputer simulation that tracks the formation of early galaxies and stars and models how radiation transformed the universe during its first 2 billion years, offering a new tool for interpreting observations from the James Webb Space Telescope.

Called Lumina, the simulation models interactions between ordinary matter, dark matter and radiation across a cosmic region spanning 500 megaparsecs, or about 1.6 billion light-years. The research was published today in the Monthly Notices of the Royal Astronomical Society.

The project brings together researchers affiliated with the Massachusetts Institute of Technology, the Harvard and Smithsonian Center for Astrophysics, the University of Texas at Dallas and other institutions. It combines a galaxy-formation model with calculations of how radiation travels through gas and changes its physical properties.

“Lumina does everything from small-scale star and galaxy formation to large-scale re-ionization of hydrogen and helium, in a volume that is 100 times larger than previous best simulations,” Mark Vogelsberger, an MIT professor of physics and an author of the study, said in a statement published by the university.

The simulation contains approximately 432 billion resolution elements representing dark matter particles and gas cells, according to the researchers. It also offers about 30 times the mass resolution of the IllustrisTNG simulation, allowing scientists to study individual galaxies while modelling a much larger portion of the cosmos.

The model begins approximately 45 million years after the Big Bang, when the universe was still dominated by neutral gas and the first generations of stars and galaxies had yet to transform their surroundings on a large scale. It follows the development of cosmic structures over time, showing how matter gathered under gravity and how radiation changed the intergalactic environment.

The calculations were run on Frontier, a supercomputer at Oak Ridge National Laboratory in Tennessee. At peak scale, the simulation used 105,504 central processing unit cores and 7,536 graphics processing units, according to the research paper. The system reached a peak memory footprint of about 600 terabytes, while individual full checkpoints occupied approximately 250 terabytes.

The computing challenge involved tracking both the movement of matter and the propagation of radiation across different scales. Researchers adapted the IllustrisTNG galaxy-formation framework and combined it with a graphics processing unit-accelerated radiation-transport solver, allowing the simulation to calculate how light interacts with gas as cosmic structures develop.

One of Lumina’s central objectives is to investigate reionization, the process through which radiation from the first luminous objects changed the state of gas filling the universe.

Hydrogen reionization occurred as ultraviolet radiation from early stars and galaxies stripped electrons from neutral hydrogen atoms. The process gradually reduced the amount of neutral gas absorbing light, allowing radiation to travel more freely through the universe.

The simulation indicates that stars and galaxies were the principal drivers of this transition. In its model, the median simulated region becomes fully ionized around a redshift of 5.2, with residual neutral hydrogen persisting until approximately redshift 4.75, according to the researchers.

Helium reionization required more energetic radiation and was driven primarily by active galactic nuclei, including supermassive black holes drawing in surrounding matter. The simulation indicates that helium reionization was nearly complete by redshift 3.

These transitions are important because they reveal how different populations of cosmic objects influenced the temperature and composition of intergalactic gas, shaping the conditions under which galaxies evolved.

Aaron Smith, an assistant professor of physics at the University of Texas at Dallas and a co-author of the study, said in a statement released by the Smithsonian Institution that the simulation allows researchers to follow changes in hydrogen and helium across an enormous volume while resolving the galaxies and luminous objects responsible.

Lumina arrives as astronomers use the James Webb Space Telescope to investigate galaxies that formed during the universe’s early history. Comparing observations with simulations allows scientists to test theories about how quickly galaxies emerged, how black holes grew and how gas was distributed between cosmic structures.

The simulation’s large volume could be particularly useful for studying rare, bright objects and large-scale environments that smaller models may not adequately represent. It could also support investigations into the movement of gas between galaxies and the gravitational-wave signals associated with ancient black holes and other cosmic systems.

However, Lumina is a computational reconstruction based on physical equations, theoretical models and assumed initial conditions, not a direct observation of the universe as it existed billions of years ago. Its predictions must be tested against astronomical observations, and agreement with existing measurements does not establish that every aspect of the model accurately reflects cosmic history.

The researchers plan to make the simulation available to the wider scientific community, enabling astronomers to compare its predicted galaxy populations and reionization patterns with observations from current and future telescopes.

Stay ahead of the Stories shaping our world. Subscribe to Impact Newswire and join our 
WhatsApp Channel for updates on global tech, business, and innovation—all in one place.

Dive deeper into the future with the Cause Effect 4.0 Podcast, where we explore the ideas, trends, and technologies driving the global AI conversation.

Got a story to share? Contact Us to reach a global audience with Impact Newswire.