'Green Pea' Galaxies May Have Reheated the Universe After Cosmic Dark Age

Swiss scientists may have found the answer to a troubling mystery about the early evolution of our universe. After the Big Bang, the universe cooled down for a billion years in a kind of cosmic dark age. But then it mysteriously reheated. Electrons and protons that had been happily joined in hydrogen atoms were ripped apart again during a period known as the "cosmic reionization." What could have done this?