Supermassive black hole nearest Earth is becoming mysteriously, intensely bright, astronomers say

The huge black hole at the heart of our galaxy has turned unusually bright – and scientists have no explanation for the dramatic behaviour.

It has started eating far more interstellar gas and dust than it has ever been seen doing before, researchers said. When they first spotted it, they thought they had accidentally looked a star – but further research has shown that the black hole is in fact showing behaviour that astronomers had never expected.

“We have never seen anything like this in the 24 years we have studied the supermassive black hole,” said Andrea Ghez, UCLA professor of physics and astronomy and a co-senior author of the research. “It’s usually a pretty quiet, wimpy black hole on a diet.

"We don’t know what is driving this big feast.”

Scientists looked through observations taken since 2003, from observatories in Hawaii and Chile. They noticed that on 13 May, the back hole was lit up twice as bright as had ever been before – and it continued to turn incredibly bright on two other nights this year.

The changes are "unprecedented", scientists say, and it is not clear why they are happening.

The kind of brightness spotted by researchers usually comes from radiation thrown out as gas and dust is eaten up by the black hole. As such, it could be just the beginning in a major change in the activity of the black hole.

“The big question is whether the black hole is entering a new phase — for example if the spigot has been turned up and the rate of gas falling down the black hole ‘drain’ has increased for an extended period — or whether we have just seen the fireworks from a few unusual blobs of gas falling in,” said Mark Morris, UCLA professor of physics and astronomy and the author of a paper describing the discovery..

Scientists will now keep looking at the area and hope that new images can help resolve that question. That could in turn help us understand how black holes grow and the kinds of effects they have on the galaxy and the larger universe.

The brightening could have come from the fact that a star was seen going very close to the black hole in summer last year, or that another mysterious object known as G2 had its outer layer ripped off when it passed by in 2014. It might also be the result of big asteroids passing near the black hole, scientists said.

The black hole poses no danger to life on Earth. It is 26,000 light years away, and the radiation coming out of it would need to be 10 billion times brighter to have any effect here.