Back in February 2024, astronomers witnessed something very strange happening in a galaxy 300 light-years away from Earth.
Erupting from the supermassive black hole located in its heart were huge flares of X-ray light, 10 times brighter than anything seen like it before and emitting 100 times more energy.
Whatever was going on at that distant black hole, it was an extreme event.
Now, after over a year of careful watching, astronomers have realised they might finally be witnessing one of the most dramatic events in the Universe – the moment a black hole bursts into life.
Bright lights, black hole
According to a study released in April 2025, the flares could be a sign that the black hole (named Ansky) has begun to feast on its surrounding gas and dust.
While that might conjure an image of a vast hole in space sucking down everything around it like a giant vacuum, the reality is a bit different.
Though nothing, not even light, can escape a black hole, this tight-hold only extends out as far as its event horizon.
Just beyond that limit, gravity instead pulls the gas and dust around the black hole into what’s known as an accretion disc.
In most black holes, like the one found at the centre of our Galaxy, the accretion disc quietly swirls around the black hole, not doing much interesting.
Until, that is, something comes along to stir up the disc. The environment close to a black hole is so extreme that even a relatively small disturbance can cause the gas to superheat and glow incredibly brightly.
In some cases, the black hole becomes what’s known as an active galactic nucleus, where the disc starts to gather more dust and gas from the surrounding environment, feeding some of it down towards the event horizon.
The resulting chaos can heat the gas until it glows so brightly, the black hole ends up outshining every star in the galaxy it resides in.
A black hole returns to life
Astronomers have seen black holes shifting from one state to another, but only when they checked on one that was previously quiet, and discovering it was now burning brightly – they never managed to catch one just at the moment it woke up.
Which is why when astronomers like Dr Lorena Hernández-García from University of Valparaíso in Chile first saw the flares erupting from Ansky, they initially thought it was what’s known as a tidal disruption event.
“These kinds of eruptions are typically linked to interactions between a compact object – like a star or another black hole – and a dense ring of gas and dust swirling around the black hole,” Hernández-García told BBC Science Focus.
If that object strays too close to the event horizon, the extreme gravitational forces can tear it apart. As each fragment of the star falls towards the black hole, it creates a bright flash of light.
But according to Hernández-García, “Ansky has not shown the typical signs of a tidal disruption event seen in other systems. There’s no evidence of such a violent disruption. We can’t be completely certain that a star isn’t being torn apart. But if it is, it would have to be a very unusual case.”
Instead, Hernández-García believes Ansky’s strange behaviour is our first glimpse of a black hole just on the cusp of becoming an active galactic nucleus.
“We believe we’re witnessing a galaxy in the process of ‘switching on’ – its central black hole is just beginning to feed again,” says Hernández-García.
If true, Ansky is granting astronomers an unprecedented opportunity to watch one of the most dramatic transformations in the Universe as it happens.
Catching a waking black hole
One of the reasons astronomers have struggled to capture this event before now is that they needed to not just be looking at the right place at the right time, but with the right telescope.
Fortunately, Ansky had already attracted astronomers' attention. Until a few years ago, it was just another quiet, boring black hole that was largely being ignored by astronomers.
It is, however, in the field of view of the Zwicky Transient Facility. This telescope sweeps the sky night after night, recording the brightness and position of stars and galaxies, monitoring for any changes.
In December 2019, it noticed the galaxy that hosts Ansky had suddenly brightened. According to Hernández-García, there was a “rise of about 20 per cent in the optical brightness occurring over less than six months. Since then, the brightness has remained higher than the original level through 2025.”
Ever since, astronomers have been monitoring Ansky for changes, including with NASA’s Swift X-ray telescope.
Despite initially finding no signs of any X-rays, in February 2024, it noticed bright flares beginning to erupt from the black hole.
What’s not clear, however, is whether there is any connection between the two events.
“We don’t yet know if the 2019 optical brightening and the 2024 X-ray eruptions are parts of the same process – like the black hole ‘waking up’ – or if they represent separate phenomena,” says Hernández-García.
While Ansky is a brilliant insight into what happens when a black hole wakes, astronomers really need to catch more events like it to understand what’s going on.
With any luck, that won’t take too long as the immensely powerful Vera Rubin Observatory is soon set to join Zwicky sweeping the sky, looking for any sign of something strange occurring in the depths of the Universe.
With more eyes on the sky than ever before, astronomers will be able to catch even more of these sleeping giants just as they are waking from their long, deep slumber.
About our expert
Lorena Hernández-García is an expert in supermassive black holes, particularly curious about how they feed and how this activity affects their galactic neighbourhoods.
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