Not long after our universe was formed by the Big Bang, the lights went out. We know that this darkened state didn’t last, but we don’t know what caused the change. Now, a team of researchers from the University of Iowa have a compelling theory on what happened.
The dark period was caused by the huge amount of thick gas that was thrown around by the Big Bang, which trapped all light. It’s thought that it might have taken up to a billion years for the fog to lift, resulting in an environment closer to the universe as we know it today.
The researchers believe that black holes situated at the center of galaxies cut through the gas clouds by ejecting matter violently. This theory is based on observations of a galaxy known as Tol 1247-232, which is some 600 million light years away from Earth, and one of just three nearby galaxies where ultraviolet light has been seen to escape.
“The observations show the presence of very bright X-ray sources that are likely accreting black holes,” Philip Kaaret — corresponding author on the paper and professor in the University of Iowa’s Department of Physics and Astronomy — told Phys. “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.”
The team observed that the brightness of the source of the X-rays fluctuated. From this, they could determine that it wasn’t a star, which led them to believe that it was a small object, and more than likely a black hole.
Black holes are known for their intense gravitational pull, which sucks in matter and doesn’t let go. Flinging material away from them might seem rather out of character, but Kaaret has an explanation: the matter that was pushed away and pierced the clouds of gas was propelled by the black hole’s rotational energy.
“As matter falls into a black hole, it starts to spin and the rapid rotation pushes some fraction of the matter out,” Kaaret explained to Phys. “They’re producing these strong winds that could be opening an escape route for ultraviolet light. That could be what happened with the early galaxies.”
More research is needed to confirm whether or not this theory is correct. Kaaret plans to continue looking at Tol 1247-232, and will also look into other galaxies where ultraviolet light is escaping to see if a pattern can be identified.