Lumina simulation maps early universe across record-breaking scale

Scientists from the Center for Astrophysics, Harvard & Smithsonian and MIT published Lumina, a simulation of the early universe, in Monthly Notices of the Royal Astronomical Society in 2026. SciTechDaily gives the publication date as Oct. 26, 2026, while Smithsonian places it in the November 2026 issue and MIT lists volume 552, issue 4.

The model follows roughly the first two billion years of cosmic history, beginning about 45 million years after the Big Bang. It spans a cube about 1.5 billion light-years on each side and includes roughly 200 million galaxies while still resolving individual galaxies, and MIT says the model provides about 30 times the resolution of IllustrisTNG. The model contains roughly half a trillion elements, made up of dark matter particles and gas cells. Its scale exceeds previous comparable simulations by more than 100 times.

Researchers used Frontier, a supercomputer at Oak Ridge in Tennessee, for the calculation. At peak, it used more than 100,000 CPU cores and around 15,000 graphics processing units, drawing about 600 terabytes of memory. Frontier holds about 37,000 graphics processing units in total, and Lumina used roughly 15,000 of them. The run needed roughly six months to finish.

The paper’s authors include Oliver Zier, Aaron Smith, Xuejian Shen, Mark Vogelsberger, Lars Hernquist and colleagues from the University of Texas at Dallas, York University and the Max Planck Institute for Astrophysics. Zier leads the paper and works as a computational astrophysicist at the Center for Astrophysics, Harvard & Smithsonian.

The cosmos began with the Big Bang some 13.8 billion years ago. The dark ages opened roughly 380,000 years after the Big Bang, when electrons joined hydrogen and helium nuclei into neutral gas. During the first 380,000 years, the universe was hot and dense, filled with electrons and nuclei. Once atoms formed, few free electrons remained to scatter leftover radiation, and no stars or galaxies existed to produce light.

The era stayed hidden because neutral hydrogen filled space and absorbed ultraviolet light before stars formed. By then the universe had become transparent to most leftover radiation, but neutral hydrogen could still absorb ultraviolet wavelengths from early stars.

Reionization ended the dark ages as radiation pulled electrons from hydrogen and helium to form ions. Early starlight ionized hydrogen a few hundred million years after the Big Bang. Helium proved tougher to ionize. Starlight removed helium’s first electron, while growing supermassive black holes supplied radiation for the second.

The simulation follows dark matter, gas, stars and radiation through the epoch of reionization. It follows radiation from emerging stars as it emerges and moves through gas. The process was uneven, with ionization bubbles around large structures and neutral regions elsewhere.

This marks the first time a model of this kind has treated helium reionization as it unfolded while letting those effects shape the simulation right away. Earlier, Thesan in 2022 covered roughly a billion years inside a 300-million-light-year cube. It builds on earlier supercomputer work such as the 2005 Millenium Simulation and the 2017 IllustrisTNG.

The project posted videos, including a close-up of a single disk-shaped galaxy and a time-lapse of hydrogen reionization across the full volume over two billion years. CNET describes 15 videos in total.

JWST can examine single early-universe objects closely, while Roman will scan wider sky areas and turn up larger samples of rare, bright galaxies. JWST observations have revealed bright galaxies and supermassive black holes in the early universe that conflict with leading theories.

Lumina predicts fewer massive galaxies in the early universe than JWST has observed. It also contains the mysterious little red dots that JWST spotted, which some researchers think may be black hole stars.

Researchers plan to study intergalactic gas motion, the role of Big Bang radiation in cosmic evolution, and how intense star-forming regions emerged. MIT says the work could help forecast gravitational-wave patterns from early galaxies and black holes. Researchers are sharing Lumina with other scientists, so they can test its predictions against telescope observations.

Comparing simulated and real universes could reveal where current theories work, fail, or call for new physics. As JWST, Roman and other telescopes provide sharper views of the distant universe, Lumina will help astronomers interpret what they see. Phys.org says the simulated size matches the scale reachable by today’s most powerful telescopes.

Funding came partly from NASA and the National Science Foundation, and the work used Energy Department computing resources at Oak Ridge. MIT says the Energy Department’s Office of Science supports Oak Ridge’s computing resources through its Advanced Scientific Computing Research programs.

Julian Muñoz, a University of Texas at Austin theoretical cosmologist who was not involved, called the project an incredible feat of engineering. Volker Bromm, a University of Texas at Austin astronomer who was not involved, said the era moves from simple physics into something overwhelmingly complex.

Volker Bromm said, “The dark ages is this transition from simple physics into this overwhelmingly complex physics.” Mark Vogelsberger said, “Lumina does everything from small-scale star and galaxy formation to large-scale reionization of hydrogen and helium.” “Lumina follows both hydrogen and helium reionization,” Zier told CNET in an email.