Scientists create a complex simulation of the early stages of the universe

29 Mar 2022

Evolution of simulated properties such as gas density and temperature in the main Thesan run, with time progressing from left to right. Image: Thesan Simulations/MIT

The Thesan simulation has helped the scientists learn more about certain processes, such as how far light could travel in the early universe.

Scientists have created a simulation of the early universe, which they claim is the largest and most detailed model to date.

The Thesan simulation – named after the Etruscan goddess of the dawn – is designed to simulate the ‘cosmic dawn’ of the universe and specifically the phase of cosmic reionisation.

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This is a time period a couple of hundred million years after the Big Bang when matter was gathered into the first stars and galaxies, with light that turned gases into hot, ionised plasma that helped create the complexities of the universe.

The simulation was developed by scientists at MIT, Harvard University and the Max Planck Institute for Astrophysics. The researchers said this time period has been challenging to reconstruct as it involves complicated and chaotic interactions between gravity, gas and radiation.

The team combined a realistic model of galaxy formation with a new algorithm that tracks how light interacts with gas and a model for cosmic dust. Researchers used the SuperMUC-NG machine – one of the largest supercomputers in the world – to carry out Thesan’s calculations over an equivalent of 30m CPU hours.

This supercomputer simultaneously harnessed 60,000 computing cores to make these calculations, an effort that would have taken 3,500 years on a single desktop, according to the researchers.

“Thesan acts as a bridge to the early universe,” Aaron Smith, a NASA Einstein fellow in MIT’s Kavli Institute, said about the model.

“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 team has published details of the Thesan simulation in the Monthly Notices of the Royal Astronomical Society. It has already helped the scientists learn more about certain processes, such as how far light could travel in the early universe.

“Thesan found that light doesn’t travel large distances early in the universe,” Harvard ITC postdoctoral fellow Rahul Kannan said. “In fact, this distance is very small, and only becomes large at the very end of reionisation, increasing by a factor of 10 over just a few hundred million years.”

As more observations are made, through projects such as the recently launched James Webb Space Telescope, researchers said the Thesan simulation could help place new information in cosmic context.

New observations were recently made about the early Milky Way. Data from the European Space Agency’s Gaia mission suggests that a part of the Milky Way began forming 13bn years ago. This is 2bn years earlier than expected and less than 1bn years after the Big Bang.

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Leigh Mc Gowran is a journalist with Silicon Republic