Scientists have discovered hundreds of black holes for the first time using computer simulations.
The technology allowed researchers at the University of Surrey to get a closer look at a "globular cluster" - a spherical collection of stars - to deduce the presence of the black holes.
They found that the 13 billion-year-old cluster, known as NGC 6101, is younger than the stars making it up, which suggests the existence of the holes.
Researchers say it is an insight they have never been able to see before.
Author of the study Miklos Peuten said: "Due to their nature, black holes are impossible to see with a telescope, because no photons can escape.
"In order to find them, we look for their gravitational effect on their surroundings. Using observations and simulations we are able to spot the distinctive clues to their whereabouts and therefore effectively 'see' the un-seeable."
Black holes are a few times larger than the Sun, and form in the gravitational collapse of massive stars at the end of their lives.
It was previously thought that these black holes would almost all be expelled from their parent cluster during the death of a star.
But the study of NGC 6101, which involved recreating its every star and black hole to see how it evolved, is calling this theory into question.
Professor Mark Gieles said: "Our work is intended to help answer fundamental questions related to dynamics of stars and black holes, and the recently observed gravitational waves.
"These are emitted when two black holes merge, and if our interpretation is right, the cores of some globular clusters may be where black hole mergers take place."
Mr Peuten added: "The results show that globular clusters like NGC 6101, which were always considered boring, are in fact the most interesting ones, possibly each harbouring hundreds of black holes.
"This will help us to find more black holes in other globular clusters in the universe. "