New simulation is largest, most detailed model of early universe

Named after the Etruscan goddess of the dawn, the "Thesan" model will help scientists study the complex environment of the young universe.

 Evolution of simulated properties in the Thesan model (photo credit: Courtesy of THESAN Simulations)
Evolution of simulated properties in the Thesan model
(photo credit: Courtesy of THESAN Simulations)

Thesan, the largest, most detailed model of the early universe to date will help scientists study the complex environment of the young universe, MIT News reported on Thursday.

A "realistic model of galaxy formation" 

The simulation is named after the Etruscan goddess of the dawn, pointing to the fact that it is made to model the "cosmic dawn."

Scientists at the Massachusetts Institute of Technology (MIT), Harvard University, and the Max Planck Institute for Astrophysics developed the model.

The period soon after the Big Bang, about 13 billion years ago, has been difficult to model as it involves very complicated, chaotic interactions, including interactions between gravity, gas and radiation.

Thesan, which simulates the period from 400,000 years after the Big Bang and onwards, combines "a realistic model of galaxy formation with a new algorithm that tracks how light interacts with gas, along with a model for cosmic dust," according to MIT News.

Researchers can use the model to simulate a 300 million cubic light year volume of the universe, running it forward in time to track the first appearance and evolution of galaxies, beginning some 400,000 years after the Big Bang and onwards.

A bridge to a young universe

The simulations so far align with what astronomers have observed of the early universe and the model may help place further observations in cosmic context. It is already helping to shed light on how far light can travel in the early universe and which galaxies were responsible for reionization, the process in which light from early stars turned surrounding gas into a hot, ionized plasma, leading to the complex universe that exists now.

“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, according to MIT News. “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.”

Thesan has been introduced by the researchers in three papers, with the third published on Thursday.

While the earliest stages of the universe, which were dark and homogenous, can be calculated with pen and paper, calculations become more complicated as gravity begins pulling and collapsing matter together, leading to a need for a full simulation.

The team of researchers aimed to include as many major ingredients of the early universe as possible, using a successful model of galaxy formation they developed earlier and then developing a new code to incorporate the interactions between light and gas.

Thesan also includes a preliminary model of cosmic dust, a feature that is unique to this model.

The team used the SuperMUC-NG machine a massive supercomputer that simultaneously used 60,000 computing cores to carry out the calculations of the simulation over an equivalent of 30 million CPU hours. On a desktop computer, this would have taken about 3,500 years.

One finding from the simulation suggests that the distance light was able to travel towards the end of cosmic reionization increased more dramatically than scientists had previously thought.

“Thesan found that light doesn’t travel large distances early in the universe,” said Rahul Kannan of the Harvard-Smithsonian Center for Astrophysics, according to MIT News. “In fact, this distance is very small, and only becomes large at the very end of reionization, increasing by a factor of 10 over just a few hundred million years.”