Scientists, led by Simon Lilly from ETH Zürich in Switzerland, have discovered why the universe is no longer opaque. Using data from NASA’s James Webb Space Telescope, they focused on a time called the Era of Reionization, which was a significant period when gas in the universe was heated, cooled, and then given an electrical charge again (reionized).
When the team examined galaxies from just 900 million years after the Big Bang, they discovered that most of the gas in the universe was partially transparent. However, the area directly surrounding the galaxies was clear. This led them to conclude that the galaxies were reionizing the gas around them, like balloons filled with reionized gas. As the galaxies grew, these bubbles merged, creating larger transparent areas. Eventually, they all combined to make the universe transparent.
To observe this phenomenon, the team used the light from a quasar, which is an extremely bright supermassive black hole. By directing the James Webb Telescope toward a specific quasar, the astronomers could see how its light passed through the gas in the universe. Some areas absorbed the light due to opaque gas, while in other areas, the light traveled through transparent gas.
The quasar’s light illuminated the gas along the astronomers’ line of sight, providing them with valuable information about the gas’s composition and state. Anna-Christina Eilers from the Massachusetts Institute of Technology, the lead author of another paper by the team, explained this in a statement.
In their future research, the team plans to study galaxies in five other regions of the sky that also have a central quasar. This will further enhance our understanding of the early universe’s opacity.
Source: Space.com / Image: Felix Mittermeier
