The History of the Universe

Image Credit: NASA, ESA, and A. Feild STScI.

Michael Shull of the University of Colorado and a team of researchers have examined evidence from Hubble Space Telescope and determined that early on in its history, the universe was super hot, then started to cool down in what they call the Quasar Era. Via Lee Hamilton's blog and Physorg: "This diagram traces the evolution of the universe from the big bang to the present. Two watershed epochs are shown. Not long after the big bang, light from the first stars burned off a fog of cold hydrogen in a process called reionization. At a later epoch quasars, the black-hole-powered cores of active galaxies, pumped out enough ultraviolet light to reionize the primordial helium." The team's results will be published in the October 20 issue of The Astrophysical Journal (homepage here).