Researchers propose how the universe became filled with light | P. Kaaret

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Aug. 30, 2017 (Phys.org) -- Soon after the Big Bang, the universe went completely dark. The intense, seminal event that created the cosmos churned up so much hot, thick gas that light was completely trapped. Much later -- perhaps as many as one billion years after the Big Bang -- the universe expanded, became more transparent, and eventually filled up with galaxies, planets, stars, and other objects that give off visible light. That's the universe we know today.

How it emerged from the cosmic dark ages to a clearer, light-filled state remains a mystery.

In a new study, researchers at the University of Iowa offer a theory of how that happened. They think black holes that dwell in the center of galaxies fling out matter so violently that the ejected material pierces its cloudy surroundings, allowing light to escape. The researchers arrived at their theory after observing a nearby galaxy from which ultraviolet light is escaping.

"The observations show the presence of very bright X-ray sources that are likely accreting black holes," says Philip Kaaret, professor in the UI Department of Physics and Astronomy and corresponding author on the study. "It's possible the black hole is creating winds that help the ionizing radiation from the stars escape. Thus, black holes may have helped make the universe transparent."

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