Discoveries Fuel Fight Over Universe’s First Light | Quanta Magazine
https://www.quantamagazine.org/discoveries-fuel-fight-over-universes-first-light-20170519/
A series of observations at the very edge of the universe has reignited a debate over what lifted the primordial cosmic fog.
Not long after the Big Bang, all went dark. The hydrogen gas that pervaded the early universe would have snuffed out the light of the universe’s
first stars and galaxies. For hundreds of millions of years, even a galaxy’s worth of stars — or unthinkably bright beacons such as those created
by supermassive black holes — would have been rendered all but invisible.
Eventually this fog burned off as high-energy ultraviolet light broke the atoms apart in a process called reionization. But the questions of exactly
how this happened — which celestial objects powered the process and how many of them were needed — have consumed astronomers for decades.
Now, in a series of studies, researchers have looked further into the early universe than ever before. They’ve used galaxies and dark matter as a giant
cosmic lens to see some of the earliest galaxies known, illuminating how these galaxies could have dissipated the cosmic fog. In addition, an international
team of astronomers has found dozens of supermassive black holes — each with the mass of millions of suns — lighting up the early universe. Another team
has found evidence that supermassive black holes existed hundreds of millions of years before anyone thought possible. The new discoveries should make
clear just how much black holes contributed to the reionization of the universe, even as they’ve opened up questions as to how such supermassive
black holes were able to form so early in the universe’s history.
