An international team of researchers, including members from the University of Michigan, has revealed surprising results that could rewrite our understanding of a key transition in the early universe.

Within the first billion years after the Big Bang, the universe filled with a fog of neutral hydrogen that was impenetrable to ultraviolet light. Today, however, that fog has cleared thanks to an epoch that began about 13 billion years ago known as reionization.

During reionization, energetic radiation from galaxies in the early universe collided with neutral hydrogen that made up the fog and broke it apart into charged, or ionized, protons and electrons.