Thanks to the Webb Space Observatory, they discover that galaxies transformed the early universe

The finding by scientists from the University of Zurich and published by NASA sheds light on a period known scientifically as ‘the Era of Reionization’, when the gas in the universe went from being opaque to transparent.

By analyzing new observations from NASA’s James Webb Space Telescope, a team led by Simon Lilly of ETH Zürich in Switzerland found evidence that galaxies that existed 900 million years after the Big Bang ionized the gas around them, causing it to make it transparent

Observations from the Webb Space Telescope provided evidence that galaxies that existed 900 million years after the Big Bang ionized the gas around them, making it transparent.

In the early universe, the gas between the stars and galaxies was opaque: energetic starlight could not penetrate it. But a billion years after the Big Bang, the gas had become completely transparent, and new research led by ETH Zurich astronomer Siman Lilly found the explanation. It just so happened that the stars in the galaxies emitted enough light to heat and ionize the gas around them, clearing our collective vision for hundreds of millions of years. The results of this research are the latest insights into a time period known as the Reionization Era, when the universe underwent drastic changes. After the Big Bang, the gas in the universe was incredibly hot and dense. Over hundreds of millions of years, the gas cooled. Then the universe hit “replay.” The gas became heated and ionized again, thought to be due to the formation of the first stars in galaxies, and over millions of years it became transparent.

Researchers have long searched for definitive evidence to explain these transformations. The new results effectively pull back the curtain on the end of this reionization period. “Not only does Webb clearly show that these transparent regions are found around galaxies, but we have also measured their size,” Daichi Kashino of Nagoya University in Japan, the lead author of the team’s first paper, explained in a statement.

NASA’s James Webb Space Telescope has returned extraordinarily detailed near-infrared images of galaxies that existed when the universe was just 900 million years old, including never-before-seen structures.

As the light from the quasar traveled towards us through different patches of gas, it was either absorbed by the opaque gas or moved freely through the transparent gas. The team’s groundbreaking results were only possible by combining Webb’s data with observations of the central quasar from the W.M. Keck in Hawaii, and the Very Large Telescope of the European Southern Observatory and the Magellan Telescope at Las Campanas Observatory, both in Chile.

“By illuminating gas along our line of sight, the quasar gives us extensive information about the composition and state of the gas,” explained Anna-Christina Eilers of MIT in Cambridge, Massachusetts, lead author of another paper by the team. The researchers then used Webb to identify galaxies near this line of sight and showed that galaxies are generally surrounded by transparent regions about 2 million light-years in radius. In other words, Webb witnessed galaxies in the process of clearing the space around them at the end of the Reionization Era. To put this in perspective, the area that these galaxies cleared is roughly the same distance as the space between our Milky Way galaxy and our closest neighbor, Andromeda.