Mystery Behind Supermassive Explosion From Black Hole in our Galaxy Explained

Astronomers from the University of Sydney say that a supermassive black hole situated in the heart of our galaxy erupted with such force about two million years ago that it illuminated a cloud located 200,000 light years away.

This discovery verifies that black holes can flicker in a short span of time. A lacy thread of gas called Magellanic Stream, which comprises mostly of hydrogen, provided clues to the researchers for this discovery.

"For 20 years astronomers have suspected that such a significant outburst occurred, but now we know when this sleeping dragon, four million times the mass of the sun, awoke and breathed fire with 100 million times the power it has today," Professor Joss Bland-Hawthorn, the lead author of this study stated in a press release.

The light emitted by the Magellanic Stream can be seen in the Large and Small Magellanic Clouds. The astronomers knew about the emission but the reason behind it was still a mystery for them.

"Since 1996, we've been aware of an odd glow from the Magellanic Stream, but didn't understand the cause. Then this year, it finally dawned on me that it must be the mark, the fossil record, of a huge outburst of energy from the supermassive black hole at the centre of our galaxy."

The area around this supermassive black hole is called Sagittarius A* (pronounced Sagittarius A-star). And it emits x-rays, gamma rays, infrared, radio and ultraviolet. When gas clouds fall on this hot sphere of emissions spinning around the black hole, the radiation flashes more.

The evidences available to the researchers point towards a cataclysmic event, which occurred in the past.

"In particular, in 2010 NASA's Fermi satellite discovered two huge bubbles of hot gas billowing out from the centre of the galaxy, covering almost a quarter of the sky," said Professor Bland-Hawthorn.

The University of California Santa Cruz had earlier this year produced computer models of the Fermi bubbles and suggested that a colossal explosion from Sagittarius A*, which took place some million years ago, caused it.

Professor Bland-Hawthorn analyzed this research and concluded that the same reason could cause the glow of the Magellanic Stream.

"Together with Dr. Ralph Sutherland from Mount Stromlo Observatory and Dr Phil Maloney, from the University of Colorado, I calculated that to explain the glow it must have happened two million years ago because the energy release shown by the Santa Cruz group perfectly matched, to our delight, that from the Magellanic Stream," said Professor Bland-Hawthorn.

The researchers said that the stars present in the galaxy don't produce enough ultraviolet to emit such a strong glow as they are too weak. Only the colossal explosion from Sagittarius A* present in the incredibly enormous black hole could account for it.

"The realisation that these black holes can switch on and off within a million years, which given the universe is 14 billion years old means very rapidly, is a significant discovery," Professor Bland-Hawthorn stated.

A similar colossal explosion is likely to recur when a gas cloud called G2 will meet the hot disc of emissions early next year, according to the researchers.