Astronomers say they have just proven the existence of a new class of massive black hole which measures about 20,000 times the size of our sun - and there's one right here in the Milky Way.
The "thrilling" find validates decades of speculation about the existence of such a black hole at the centre of a neighbouring star cluster, Omega Centauri.
It is believed to be the nearest black hole of its kind to Earth.
An international team including University of Queensland researchers have published the findings of their study in the journal Nature today.
Astronomers led by the Max-Planck-Institut für Astronomie in Germany analysed and catalogued 1.4 million stars in the Omega Centauri cluster and then compared these against theoretical models made by UQ's Associate Professor Holger Baumgardt.
Baumgardt said the team was looking for fast-moving stars which were expected to exist near concentrated masses such as black holes.
"Identifying these stars was the smoking gun evidence we needed to prove the black hole's existence - and we did," he said.
"When I saw the data, I immediately knew we found something special.
"Astronomers have tried to find one of these black holes for over 20 years, and now we have finally succeeded."
The enormous black hole is located about 18,000 light years from our solar system - a mind-blowing distance that in astronomical terms makes it our near neighbour.
The very existence of this size of black hole - classed as an intermediate-mass black hole - has been in question until now.
Although stellar black holes - produced when a star dies and collapses in on itself - have been found as close as 1000 light years from Earth, these measure just a few dozen kilometres wide and could be squeezed between the Sydney Opera House and the airport.
At the other end of the spectrum, supermassive black holes can be up to billions of times the mass of the sun and are typically found at the centre of large galaxies, including our Milky Way.
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The international team analysed more than 500 images of the Omega Centauri cluster taken by the Hubble space telescope.
Using Baumgardt's theoretical model, they determined that only an intermediate-mass black hole - smaller than a supermassive but much, much larger than a stellar - could produce the seven fast-moving stars they identified.
"This class of black holes has been a theory for decades but is now fully confirmed to exist," Baumgardt said.
He said he and the team were amazed at the magnitude of their discovery.
"I think this will invigorate the field and lead to a lot of new research in this area.
"We can begin to speculate how this black hole formed, how it's related to other massive black holes astronomers have found, and where other intermediate-mass black holes might exist."
