Cosmic Reionization

In the Big Bang model of cosmology, early in the history of the universe it was too hot for neutral hydrogen gas, all the electrons were stripped from the nucleus (usually a proton), and the hydrogen gas filling the universe was ionized. As the universe expanded, the temperature cooled enough for neutral hydrogen, and the electrons became bound to protons. At some point stars began to form and the ultraviolet radiation the stars radiated was sufficient to ionize hydrogen gas once again - cosmic reionization. In this preprint Testing Reionization with Gamma Ray Burst Absorption Spectra the era of reionization is studied by looking for very ancient gamma ray bursts, the most energetic events known in the universe.