Two supermassive black holes are spiralling towards each other and will merge into one colossal abyss, astronomers have said.
It is the closest pair of black holes found to date as a cataclysmic collision is said to be inevitable.
The two black holes are 80 million light-years away from Earth but are just 1,600 light-years apart from each other.
Lead author Dr Karina Voggel, of the University of Strasbourg, said: "They have a much smaller separation than any other previously spotted pair of supermassive black holes.
"They will eventually merge into one giant black hole."
When they come together it will send out gravitational waves, or ripples in space and time, just as predicted in Albert Einstein's general theory of relativity.
The bigger of the two black holes have a mass almost 154 million times that of the Sun.
The black holes are at the centre of a dense group of bright stars that were captured by ESO's (European Space Observatory's) Very Large Telescope (VLT) in Chile.
Dr Voggel said: "The two black holes are on a collision course and form the closest pair of supermassive black holes found to date.
"It is also the pair with the smallest separation between two supermassive black holes found to date - observed to be just 1,600 light-years apart in the sky."
Black holes, which come in different sizes, are formed when very massive stars collapse at the end of their life cycle.
Supermassive black holes are the largest kind, growing in mass as they devour matter and radiation and perhaps merge with other black holes.
These phenomenally dense celestial entities are extraordinarily difficult to observe despite their great mass because it does not allow light to escape.
The size of the black holes was calculated from the gravitational pull of the stars around them and was made possible because of how close the system is to earth.
A scanner called MUSE (Multi-Unit Spectroscopic Explorer) was mounted on the telescope and Hubble data confirmed the supermassive black holes.
Astronomers also say these findings could mean there are more black holes merging out there.
Dr Voggel said: "Our finding implies there might be many more of these relics of galaxy mergers out there.
"They may contain many hidden massive black holes that still wait to be found.
"It could increase the total number of supermassive black holes known in the local universe by 30 per cent."
The search for similarly hidden supermassive black hole pairs is set to make a great leap forward with ESO's Extremely Large Telescope (ELT).
It is also being built in the Atacama Desert just 12 miles from the VLT - and is due to be in operation before the end of the decade.
Co-author Dr Steffen Mieske said: "This detection of a supermassive black hole pair is just the beginning.
"With the HARMONI instrument on the ELT, we will be able to make detections like this considerably further than currently possible."
He added: "ESO's ELT will be integral to understanding these objects."
