Scientists at the Center for Astrophysics | Harvard & Smithsonian have created Lumina, one of the largest and most detailed simulations of the early universe. By modeling interactions among ordinary matter, dark matter and radiation during the first two billion years after the Big Bang, the simulation offers a way to test theories of cosmic evolution against observations from the James Webb Space Telescope (JWST), the Nancy Grace Roman Space Telescope and other instruments.
The research, published in Monthly Notices of the Royal Astronomical Society, could help astronomers understand how the earliest galaxies formed and how they changed the gas surrounding them. Comparing Lumina’s predictions with telescope observations may also reveal discrepancies that point to physical processes not fully accounted for in current theories.
Astronomers have spent centuries developing explanations for the formation of stars, galaxies and other cosmic structures. Modern supercomputers allow researchers to turn those ideas into detailed simulations that predict how the universe should evolve. Agreement between simulations and observations strengthens confidence in existing theories, while unexpected differences can indicate that those theories need to be refined.
“JWST has made the early Universe an exciting new frontier in astrophysics,” said lead author Oliver Zayer, an ITC Fellow at the Center for Astrophysics | Harvard & Smithsonian. “To understand what we’re seeing with this telescope, we need to translate theory into detailed predictions. After several years of work with many ups and downs, it’s very rewarding to see the simulation results and see the predictions come to life on video.”
Recreating the first 2 billion years
Lumina is described as the largest cosmic radiation-hydrodynamics simulation ever created. It uses powerful computers to calculate how gas, dark matter and light interact as the young universe develops. By following those interactions across the first two billion years after the Big Bang, researchers can investigate the formation of the earliest galaxies and how their activity affected the enormous gas clouds around them.
The simulated region is more than 100 times larger than those modeled in previous comparable projects. Lumina’s virtual universe occupies a cube about 1.5 billion light-years on each side, providing a view of cosmic evolution on a scale comparable to the vast regions that can be studied with today’s most advanced telescopes.
Another important feature is the simulation’s treatment of helium reionization, a process in which radiation strips electrons from helium atoms. Lumina tracks this transformation as it unfolds while also modeling its effects on the surrounding universe. This enables researchers to study the relationship between evolving galaxies, radiation and the gas filling the space between galaxies.
“We feel very fortunate to be able to build simulations like Lumina,” said Aaron Smith, an assistant professor of physics at the University of Texas at Dallas and an author of the paper. “For the first time, we can follow the transformation of both hydrogen and helium into their modern forms across the vast expanses of the universe, while unraveling the galaxies and other luminous objects driving that transformation.”
A virtual universe on a supercomputer
Recreating such a large portion of cosmic history required substantial computing power. The team used more than 15,000 graphics processing units on Frontier, one of the world’s fastest supercomputers, at Oak Ridge National Laboratory in Tennessee.
That processing capacity allowed the researchers to model an enormous region of the early universe without losing the detail needed to study individual galaxies and other important structures. Lumina can therefore track both large-scale cosmic evolution and processes involved in the formation of stars, galaxies and black holes.
Investigating the early universe
Lumina is intended not only to reconstruct cosmic history but also to provide a framework for studying how the universe developed. The researchers plan to use it to examine the movement of gas between galaxies, the effects of radiation left over from the Big Bang and the emergence of regions where stars formed at especially high rates.
By comparing these predictions with observations from JWST, the Nancy Grace Roman Space Telescope and other instruments, scientists hope to develop a more complete picture of the universe’s early stages. Differences between the simulated and observed universes could provide clues about where current theories need to be refined or reconsidered.
Source: www.sciencedaily.com
