Stunning new simulation shows how light came to be in our universe

(ORDO NEWS) — There was a time when our universe was just an opaque, opaque sea of ​​swirling gas.

However, by the time the universe was a billion years old, everything had changed. Radiation from the first stars and galaxies produced dramatic changes, allowing light to travel freely across the entire electromagnetic spectrum.

The new simulation, named Tesan after the Etruscan goddess of dawn, has allowed scientists to explore the dark ages of the universe. This is a new tool to study in detail how the light could turn on during the cosmic dawn. And he is absolutely wonderful.

“Tesan acts as a bridge to the early universe,” says physicist Aaron Smith of the MIT Kavli Institute for Astrophysics and Space Studies.

“It is intended to serve as an ideal simulation counterpart for upcoming observations that could fundamentally change our understanding of the cosmos.”

Most of what we know about the universe, we learned through light (with the exception of gravitational waves a field of astronomy that is still in its infancy).

So when the light is obstructed in some way, it creates some problems; it is enough to look (or not look, depending on the situation) at black holes that do not emit any detectable radiation.

The early universe between 50 million and 1 billion years after the Big Bang is another such case. This period is known as the “cosmic dawn” a time when the universe as we know it today was just beginning to form from primordial plasma.

Before the appearance of the first stars, it was filled with a hot cloudy fog of ionized gas. Light could not pass freely through this fog; it simply scatters away from free electrons.

When the universe cooled down enough, protons and electrons began to recombine into neutral hydrogen atoms. This meant that light could finally travel through space.

When the first stars and galaxies began to form about 150 million years after the Big Bang, their ultraviolet light gradually reionized the neutral hydrogen ubiquitous throughout the universe, allowing the entire spectrum of electromagnetic radiation to circulate freely. This is the era of reionization.

About 1 billion years after the Big Bang, the universe was completely reionized; however, sooner than 1 billion years from now, we cannot observe with our current instruments, making this critical cosmic dawn difficult to understand.

“Most astronomers don’t have laboratories in which to conduct experiments. The scales of space and time are too large, so the only way to conduct experiments is with computers,” says astrophysicist Rahul Kannan of the Harvard-Smithsonian Center for Astrophysics.

“We can take the basic physical equations and governing theoretical models to model what happened in the early universe.”

Tesan starts with a realistic model of galaxy formation, as well as a new algorithm for reproducing how light interacts with and reionizes surrounding gas, and a model of cosmic dust.

These processes and interactions are very complex; to model a 300 million light-year stretch of the universe, from 400,000 to a billion years after the Big Bang, the team used a powerful supercomputer, the SuperMUC-NG machine, which used the equivalent of 30 million CPU hours to run Thesan.

According to the researchers, the resulting simulation is the most detailed representation of the Reionization Epoch, reflecting physics on scales a million times smaller than the simulated regions.

This provides an “unprecedented” look at how early galaxies formed and interacted with the gas of the early universe. It shows a gradual change as light begins to seep through the universe.

“It’s a bit like water in trays of ice cubes; when you put it in the freezer it takes a while, but after a while it starts to freeze around the edges and then slowly seeps in,” Smith said.

“The same situation was in the early universe – it was a neutral, dark space that became bright and ionized when light began to emerge from the first galaxies.”

Interestingly, Tesan showed that initially light does not travel very far at all. Only towards the end of reionization is light capable of traveling long distances. The team also saw which types of galaxies have the biggest impact on reionization, with galactic mass playing a big role.

We won’t have to wait long to find out how accurate the simulation turned out to be.

The James Webb Space Telescope (JWST) is due to start scientific research in a few months, and it is designed in part to look into the past about 300,000 years after the Big Bang, when reionization was in full swing.

“And that’s the fun part,” said physicist Mark Vogelsberger of the Massachusetts Institute of Technology.

“Either our simulations and Tezan’s model agree with what the JWST finds, which confirms our picture of the universe, or there will be a significant discrepancy showing that our understanding of the early universe is incorrect.”

In any case, we will learn something very interesting about the mysterious birth and early years of our amazing universe.


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