# Smithsonian Astrophysicists Model 1.5 Billion Light-Year Cosmic Volume in Lumina Simulation

- Published: 2026-11-10 10:10 UTC
- Section: Sky & Space › Astronomy
- Tags: cosmological simulation, radiation hydrodynamics, cosmic reionization, IllustrisTNG, AREPO code, early universe, Lumina simulation
- URL: https://realtech.media/news/rt-8029ef24b1d1162e66eacaf3_smithsonian_astrophysicists_model/

**Researchers modeled the first 2 billion years of the universe across a 500 cMpc box down to redshift z=3 to track coupled hydrogen and helium reionization.**

![Smithsonian Astrophysicists Model 1.5 Billion Light-Year Cosmic Volume in Lumina Simulation](https://realtech.media/media/2026/11/1b51c6e8df2fc23a.jpg)
*Ross Burgener, Wikimedia Commons, Public domain*

Astrophysicists from the Center for Astrophysics | Harvard & Smithsonian and their colleagues have developed Lumina, a cosmological radiation-hydrodynamic simulation tracing the first 2 billion years of the universe down to redshift z=3 [1]. The work, published in *Monthly Notices of the Royal Astronomical Society*, reproduces cosmic evolution inside a comoving cubic volume with an edge length of 500 cMpc (approximately 1.5 billion light-years) [1]. Calculations were executed on the Frontier supercomputer at Oak Ridge National Laboratory using over 15,000 GPUs to simultaneously capture large-scale structure and discrete luminous sources [1].

## Computational Architecture and Resolution

The simulation resolves cosmic evolution using the moving-mesh hydrodynamic code AREPO, combining the IllustrisTNG galaxy formation physics with a GPU-accelerated M1 radiative transfer solver across six frequency bins [1]. Lumina contains 2 × 6000³ resolution elements, providing a baryonic mass resolution of 3.6 × 10⁶ solar masses and a dark matter mass resolution of 1.9 × 10⁷ solar masses [1]. The initial conditions incorporate separate transfer functions for baryons and dark matter, accounting for their relative streaming velocity [1]. This resolution allows the system to follow the coupled evolution of the intergalactic medium, galaxies, and active galactic nuclei.

## Reionization Dynamics and Constraints

Lumina models the timeline and mechanics of cosmic reionization self-consistently across the full simulated volume [1]. The simulation predicts late hydrogen reionization powered primarily by stars, with the median sub-volume becoming fully ionized at z ≈ 5.2 and residual neutral hydrogen patches remaining until z ≈ 4.75 [1]. Helium (He II) reionization is driven by active galactic nuclei and reaches near completion by z = 3, causing a distinct late-time thermal boost in the intergalactic medium [1]. The resulting Thomson scattering optical depth matches data from the Planck observatory, while the thermal history and photoionization background align with empirical astrophysical constraints [1].

## Sources

1. [Monthly Notices of the Royal Astronomical Society](https://doi.org/10.1093/mnras/stag1469)
2. [SciTechDaily](https://scitechdaily.com/smithsonian-scientists-built-a-virtual-universe-1-5-billion-light-years-across)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-8029ef24b1d1162e66eacaf3_smithsonian_astrophysicists_model/