A group of scientists has produced the larger and more detailed model of the primeval Universe that has been achieved to date. The simulation has been named ‘Thesan’ in honor of the Etruscan goddess of dawn and helps to understand the first billion years since the origin of the Universe.
It all started around 13.8 billion years ago with the big bang of the big Bang. The matter and energy that formed the Universe appeared suddenly and spectacularly, but soon after it cooled drastically and went completely dark. A couple of hundred million years after the big Bangthe universe woke up when gravity gathered matter into the first stars and galaxies.
The light from these early stars turned the surrounding gas into a hot ionized plasma, a crucial transformation known as cosmic reionizationthe second largest phase change of hydrogen in the universe that modified it into the complex structure we see today.
For physicists, cosmic evolution during these early ‘dark ages’ has been relatively simple to calculate, but beyond that the situation becomes more complicated because at some point gravity began to attract and collapse matter. “Slowly at first, but then so quickly that the calculations become too complicated and we have to do a full simulation”they comment.
Therefore this phase of cosmic reionization it has been a difficult period for astrophysicists to reconstructin the face of immensely complicated chaotic interactions, including those of gravity, gas, and radiation.
Detailed the early Universe
A simulation known as Thesan, developed by scientists at MIT, Harvard University, and the Max Planck Institute for Astrophysics, resolves these interactions of the “cosmic dawn” with the greatest detail and volume of any model achieved to date.
To do this, the Thesan simulation combines a realistic model of galaxy formation with a new algorithm that tracks how light interacts with gas, along with a model of cosmic dust. Thus, they have been able to model a cubic volume of the universe that spans 300 million light-years in diameter.
From there they have advanced in time to trace the first appearance and evolution of the hundreds of thousands of galaxies that shaped the early Universe, from 400,000 years after the Big Bang to the first billion years.
«Thesan acts as a bridge to the early universe«, explain the scientists of the project. «It is intended to serve as an ideal simulation counterpart for upcoming observing facilities, which are poised to fundamentally alter our understanding of the cosmos.”.
Thesan follows how light from these early galaxies interacts with gas over the first billion years and transforms the universe from neutral to ionized. One discovery of the model is that light did not travel great distances in the early universe: “In fact, this distance is very small and only becomes large at the end of reionization, increasing by a factor of 10 in just a few hundred million years.”.
Great riddles await. And it is that until now the simulations were based on the few observations that astronomers had of the early universe. As more data becomes available, for example with the recently launched James Webb Space Telescope, they hope to place those observations in cosmic context and improve our understanding of the origin of the Universe.