(CN) – Just 3.5 million years ago, after the dinosaurs had already become extinct and ancient human ancestors began to walk the Earth, the center of the Milky Way galaxy lit up as epic beams of energy burst forth, creating a flare that expanded to more than 200,000 light years away from the supermassive black hole that birthed it.
That’s what researchers discovered, according to a new study to be published soon in The Astrophysical Journal. The event, known as a Seyfert flare, is a burst of radiation in two energized cones. What started as a small emission of radiation grew in size to create two enormous cones that cut through the entire galaxy and beyond to the Magellanic Stream, a long trail of gas.
The Australian-U.S. team of scientists who studied the phenomenon said the size of the explosion could only have been created by Sagittarius A, the supermassive black hole in the middle of the Milk Way that is 4.2 million times more massive than our own Sun.
"The flare must have been a bit like a lighthouse beam," said Joss Bland-Hawthorn, professor at the University of Sydney. "Imagine darkness, and then someone switches on a lighthouse beacon for a brief period of time."
The event took place relatively recently in Earth’s history. By the time the flare erupted, the asteroid responsible for wiping out the dinosaurs happened 63 million years prior and human ancestors known as Australopithecines were already living in Africa.
"This is a dramatic event that happened a few million years ago in the Milky Way's history," said Lisa Kewley, professor at the Australian National University College of Physical and Mathematical Sciences. "A massive blast of energy and radiation came right out of the galactic centre and into the surrounding material. This shows that the centre of the Milky Way is a much more dynamic place than we had previously thought. It is lucky we're not residing there!"
The scientists estimate the flare lasted for about 300,000 years, a relatively short time in a galactic scale.
"These results dramatically change our understanding of the Milky Way," said Magda Guglielmo from the University of Sydney in a statement. "We always thought about our Galaxy as an inactive galaxy, with a not so bright center. These new results instead open the possibility of a complete reinterpretation of its evolution and nature.”
Guglielmo said much more work is needed to understand how black holes evolve and interact with the galaxies around them.
"The flare event that occurred three million years ago was so powerful that it had consequences on the surrounding of our Galaxy. We are the witness to the awakening of the sleeping beauty," she said.