Scientists have captured the 'awakening' of a supermassive black hole unexpectedly springing to life.
More than 300 light-years from Earth in the Virgo constellation, this black hole had remained silently hidden until it reactivated without warning in 2019.
More than a 100,000 times the mass of our sun, this enormous void suddenly began to consume the matter of its surrounding galaxy.
The black hole is now emitting so much light that an international team of scientists has been able to watch the 'unprecedented' moment it came back to life.
And, the experts say that this is something that could happen at the core of our own galaxy.
Researchers have captured the moments that a terrifying black hole 'awakens' from its slumber and begins consuming its galaxy, as shown in this artist's impression
The three types of black hole
Stellar: Five to several tens of solar masses (one solar mass is the mass of our sun)
Intermediate: 100 to 100,000 solar masses
Supermassive: Millions to billions of solar masses
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Until very recently, the galaxySDSS1335+0728 had been just another dim and relatively uninteresting part of space.
But, in December 2019, scientists noticed that the star had started to give off massive amounts of infrared, ultraviolet, and visible light.
Paula Sánchez Sáez, an astronomer at European Southern Observatory in Germany and lead author of the study, says: 'Imagine you’ve been observing a distant galaxy for years, and it always seemed calm and inactive.
'Suddenly, its [core] starts showing dramatic changes in brightness, unlike any typical events we've seen before.'
While it is not uncommon for galaxies to become brighter, none of those explanations matched what the scientists were now seeing.
Supernovae or tidal disruption events, in which a star is torn apart by a black hole, produce lots of light but only over very short periods of time.
However, Galaxy SDSS1335+0728 is still getting brighter more than four years after it first 'turned on'.
As this artist's impression shows, before 2019 the galaxy was fairly dim and did not feature a bright light at its core. This was because the supermassive black hole at its centre was dormant
By combining observations from various telescopes around the world, including the ESO's 'Very Large Telescope' (VLT) researchers have been able to watch this process as it unfolds.
The data they collected shows that the galaxy is now producing four times as much UV radiation, twice as much infrared radiation, and has even started to produce X-rays.
This provides strong evidence that the black hole has activated, making this an 'active galactic nucleus'.
Co-authorLorena Hernández García, from the University of Valparaíso in Chile, says: 'The most tangible option to explain this phenomenon is that we are seeing how the [core] of the galaxy is beginning to show activity.
'If so, this would be the first time that we see the activation of a massive black hole in real time.'
This gives scientists a unique opportunity to peer into the inner workings of some of the most exotic objects in the universe.
As black holes feed, the matter falling into their pull becomes extremely hot and bright. Scientists believe it is the radiation from gases falling into the black hole that they can now observe (artist's impression)
Black holes are so dense that not even light can escape their gravitational pull, making them extremely difficult to observe.
Scientists can only observe the effects they have on the universe around them, either through gravitational lensing or through the light emitted by super-hot orbiting matter.
This means that when a black hole is inactive and not consuming any more matter, they are all but invisible to our telescopes.
Co-authorClaudio Ricci, from the Diego Portales University in Chile, says: 'These giant monsters usually are sleeping and not directly visible.
'In the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, [which] suddenly started to feast on gas available in its surroundings, becoming very bright.'
Not only does this provide scientists with data on how black holes work, but it might also give us a hint at the future of our galaxy, the Milky Way
The largest black hole in the Milky Way is Sagittarius A*, at the galaxy's centre, which has a solar mass of around 4 million – and is spinning so fastit's taken on the shape of a football.
Although the GalaxySDSS1335+0728 is more than 300 light-years away in a region of space called the Virgo constellation (pictured) the researchers think we could use it to learn about the supermassive black hole in the centre of our own galaxy
Pictured, instruments that form the Very Large Telescope in the remote, sparsely populated Atacama Desert in northern Chile
Lead author Dr Sáez told MailOnline: 'The black hole in the centre of our galaxy, Sagittarius A*, is currently in a quiescent phase, but we cannot discard that in the future, it can pass through a similar process to the one observed in SDSS1335+0728.'
However, DrSáez also notes that it is not certain how likely this is to happen.'
She says: 'So we are not at risk, and probably, if it activates, nothing will happen to the solar system, as we are very far from the centre of the galaxy.
'But we will probably see some spectacular light coming from the galactic centre.'
The researchers say that more tests will be needed to rule out any alternative explanations, but that the black hole reactivating remains the most likely explanation.
For example, they note that this could be caused by an exceptionally slow 'tidal disruption event' –when a star is torn apart by the strong gravitational force of a nearby supermassive black hole.
Yet this would either have to be the longest and dimmest tidal disruption event ever observed or some even more unusual as-yet-unknown class of event.
Dr Sáez concludes: 'Regardless of the nature of the variations, [this galaxy] provides valuable information on how black holes grow and evolve.'
FIVE BLACK HOLE THEORIES THAT WILL BLOW YOUR MIND
Black holes are among the most fascinating and fiercely debated objects in the universe.
They have captured the public's imagination for decades, partly thanks to the late Stephen Hawking, who transformed them from a difficult-to-understand scientific theory to a source of mysterious wonder.
Mysterious:Black holes are among the most fascinating and fiercely debated objects in the universe (stock image)
They have also percolated popular culture through sci-fi magazines, Star Trek and Hollywood blockbusters.
But what are the five most bizarre and captivating theories about black holes that are so unfathomable the mind boggles?
Here MailOnline takes a look.
