A group of astronomers led by Sarah Bosman from the Max Planck Institute for Astronomy have robustly timed the end of the epoch of reionization of the neutral hydrogen gas to about 1.1 billion years after the Big Bang. Reionization began when the first generation of stars formed after the cosmic “dark ages,” a long period when neutral gas alone filled the universe without any sources of light. The new result settles a debate that lasted for two decades and follows from the radiation signatures of 67 quasars with imprints of the hydrogen gas the light passed through before it reached Earth. Pinpointing the end of this “cosmic dawn” will help identify the ionizing sources: the first stars and galaxies.
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Source: Phys.org