The Epoch of Reionization

What happened

The intense radiation from the first stars and galaxies stripped electrons back off the hydrogen atoms filling space, a process called reionization. Over hundreds of millions of years it burned away the last of the cosmic fog, so that by roughly a billion years after the Big Bang the universe had become transparent to light, as it is today.

Why it matters

Reionization was the last great transformation of the early universe, marking the point when the cosmos lit up and cleared, allowing starlight to travel freely across it.

Sources

• NASA Science. Webb — The Early Universe · Reputable source