WE ARE ALL DESIGNIST:

Another way to gain insights on this bygone era is to simulate it on computers. The early stages of reionization are relatively simple to re-create because the universe was relatively dark and uniform then, explains Aaron Smith, an astrophysicist at the Massachusetts Institute of Technology, who helped develop THESAN. As primordial matter sorts itself into galaxies and stars, however, complex interactions between gravity, light, gas and dust become increasingly difficult to model.

"Since modeling light is quite complicated and computationally expensive, there are only a few cosmological simulations that focus on exploring this epoch," says astrophysicist Rahul Kannan of the Harvard-Smithsonian Center for Astrophysics, who helped develop THESAN. "Each of these cosmological simulations have their own advantages and disadvantages."

THESAN is designed to simulate the early universe to an unprecedented extent. Some cosmological simulations, such as the Cosmic Dawn (CoDa) simulations and the Cosmic Reionization on Computers (CROC) project, have modeled large volumes at relatively low resolutions, while others, such as the Renaissance and SPHINX simulations, are more detailed but do not span great distances. In contrast, THESAN "combines high resolution with large simulated volumes," Kannan says.

"Usually there's a trade-off between studying in detail galaxy formation and cosmic reionization, but THESAN manages to do both," says astrophysicist John Wise of the Georgia Institute of Technology, who did not work on THESAN.

THESAN's developers built it on the back of an older series of simulations called Illustris-TNG, which have been shown to accurately model many of the properties and populations of evolving galaxies. They next developed a new algorithm to model how the light from stars and galaxies interacted with and reionized their surrounding gas over the first billion years of the universe--details that previous simulations have not successfully incorporated at large scales. Finally, the THESAN team included a model of how cosmic dust in the early universe may have influenced the formation of galaxies.

Tweet   @brothersjudd