English: More than 13 billion years ago, during the Era of Reionization, the universe was a very different place. The gas between galaxies was largely opaque to energetic light, making it difficult to observe young galaxies. As stars and young galaxies continued to form and evolve, they began to change the gas around them. Over hundreds of millions of years, the gas converted from neutral, opaque gas to ionized, transparent gas.

What allowed the universe to become completely ionized, leading to the “clear” conditions we see in the present-day universe? Researchers using the James Webb Space Telescope found that galaxies are overwhelmingly responsible toward the end of this period. Read about their findings.

NASA, ESA, CSA, Joyce Kang (STScI)