Unexplained flashes spotted coming from our galaxy's nearest black hole, scientists say

Experts describe events as 'unprecedented'

Andrew Griffin
Tuesday 13 August 2019 15:39 BST
Timelapse footage of strange flash coming from our nearest black hole Sagittarius A*

Astronomers have spotted strange, unexplained flashes coming out of our black hole.

The huge swirling object at the centre of our galaxy – which is four million times the mass of the Sun, and known as Sagittarius A* – is sending out unusual blasts of radiation that are more powerful than have ever been seen before.

And scientists do not know why it is sending out the flashes, despite having watched them in real time.

Describing the discovery in a new paper, titled 'Unprecedented Near-Infrared Brightness and Variability of Sgr A*', the researchers behind the discovery say the chance of seeing such a series of blasts being sent through the galaxy is very low, after calculating it using "the most comprehensive statistical model ever published".

The chance of seeing one night with this kind of radiation is 0.3 per cent, the researchers say. The chance of seeing unusual activity over four nights, as the researchers did, is less than 0.05 per cent.

The researchers say the flashes could indicate that the black hole known as Sgr A* has become more active, or that it has started accreting more or different material. It might also suggest that our understanding of the black hole is wrong, and that researchers will have to come up with a new model to understand it.

One of the possibilities is that the flash was thrown out when the star known as S0-2 moved close to the black hole, in 2018. Researchers had been watching that star in an attempt to understand more about Einstein's theory of general relativity, but it appears to have found something even more surprising.

It might also be the remnants of the passage of a dusty object known as G2, which passed by in 2014. Researchers had expected a thrilling display when that happened, but found themselves ultimately disappointed – it might be, however, that the exciting show was simply delayed rather than cancelled.

Researchers now hope to keep examining the black hole both to watch for potential changes in its state and to better understand what physical processes might be responsible for the changes in how it looks.

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