MIT scientists developed the most detailed simulation of the early universe ever

Imagine seeing the early universe, in real-time.
Loukia Papadopoulos
A screenshot from clip of the Thesan simulationMIT

How did we come to be? How was the universe created? Those are questions that astrophysicists have pondered and explored for many years.

Now, scientists at MIT, Harvard University, and the Max Planck Institute for Astrophysics have developed a detailed view of how the universe may have unfolded after the big bang, according to a press statement by MIT published on Thursday.

They have named their new simulation Thesan after the Etruscan goddess of the dawn and it is designed to recreate the cosmic reionization period, a mysterious time that has often perplexed astrophysicists.

Long-standing questions

The simulation is being used to answer long-standing questions such as how far light could travel in the early universe and which galaxies were responsible for reionization.

“Thesan acts as a bridge to the early universe,” said Aaron Smith, a NASA Einstein Fellow in MIT’s Kavli Institute for Astrophysics and Space Research. “It is intended to serve as an ideal simulation counterpart for upcoming observational facilities, which are poised to fundamentally alter our understanding of the cosmos.”

The project began with a model of galaxy formation that the researchers previously engineered, called Illustris-TNG, which has been shown to accurately simulate the properties and populations of evolving galaxies. The teams then conceived of a new code that would illustrate how the light from galaxies and stars interacted with and reionized the surrounding gas.

“Thesan follows how the light from these first galaxies interacts with the gas over the first billion years and transforms the universe from neutral to ionized,” said Rahul Kannan of the Harvard-Smithsonian Center for Astrophysics. “This way, we automatically follow the reionization process as it unfolds.”

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Last but not least the team incorporated a model of cosmic dust.

The most detailed view of cosmic reionization

The end result is a simulation that produces the most detailed view of cosmic reionization, across the largest volume of space, of any currently existing simulation. There are plenty of simulations models available today but they either model across large distances at low resolution or offer more detailed simulations that do not span large volumes.

“We are bridging these two approaches: We have both large volume and high resolution,” Mark Vogelsberger, associate professor of physics at MIT, concluded.

The resulting video simulation is a mesmerizing clip that is entertaining to watch even if you are not an astrophysicist that can fully understand it. The study is published in the journal Monthly Notices of the Royal Astronomical Society.

Study abstract: 

The visibility of high-redshift Lyman-alpha emitting galaxies (LAEs) provides important constraints on galaxy formation processes and the Epoch of Reionization (EoR). However, predicting realistic and representative statistics for comparison with observations represents a significant challenge in the context of large-volume cosmological simulations. The THESAN project offers a unique framework for addressing such limitations by combining state-of-the-art galaxy formation (IllustrisTNG) and dust models with the AREPO-RT radiation-magneto-hydrodynamics solver. In this initial study, we present Lyman-alpha centric analysis for the flagship simulation that resolves atomic cooling haloes throughout a (95.5 cMpc)3 region of the Universe. To avoid numerical artifacts we devise a novel method for accurate frequency-dependent line radiative transfer in the presence of continuous Hubble flow, transferable to broader astrophysical applications as well. Our scalable approach highlights the utility of LAEs and red damping-wing transmission as probes of reionization, which reveal nontrivial trends across different galaxies, sightlines, and frequency bands that can be modeled in the framework of covering fractions. In fact, after accounting for environmental factors influencing large-scale ionized bubble formation such as redshift and UV magnitude, the variation across galaxies and sightlines mainly depends on random processes including peculiar velocities and self-shielded systems that strongly impact unfortunate rays more than others. Throughout the EoR local and cosmological optical depths are often greater than or less than unity such that the exp ( − τ) behavior leads to anisotropic and bimodal transmissivity. Future surveys will benefit by targeting both rare bright objects and Goldilocks zone LAEs to infer the presence of these (un)predictable (dis)advantages.

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