Astronomers on Wednesday announced their discovery of the solar system’s nearest massive black hole, an elusive and long-sought, so-called “missing link” in the formation of supermassive black holes.

The black hole estimated to weigh at least 8,200 times the sun’s mass is located at the centre of a collection of stars called the Omega Centauri cluster, 18,000 light years away, they said in a study reporting their discovery. Their study was published in the journal Nature on Wednesday.

Black holes are the mystery-ridden remnants of massive stars that, after exhausting their fuel, have collapsed under their own weight into compact objects with such high gravity that not even light can escape them.

Scientists have since 1965 documented dozens of black holes within the Milky Way and in other galaxies. But all of them have been either stellar-mass black holes 5 to 150 times the mass of the sun or supermassive black holes, more than 1,00,000 to millions or billions of times the mass of the sun. A supermassive black hole 4 million times the mass of the sun lies at the core of the Milky Way itself.

The black hole lurking in the Omega Centauri cluster is the first firm detection of an intermediate-mass black hole, what astronomers view as a missing link between stellar-mass and supermassive black holes.

“We do not yet have a full understanding of how supermassive black holes are formed,” Nadine Neumayer, a scientist at the Max Planck Institute for Astronomy in Germany and a study team member, told The Telegraph via email. “Intermediate-mass black holes have been speculated to be the seeds for supermassive black holes.”

Neumayer and her colleagues analysed the speeds of 1.4 million stars in the Omega Centauri cluster, using 500 images taken by the Hubble Space Telescope over the past 20 years and spotted seven stars orbiting a central region of the cluster at high speeds..

“Looking for and documenting the motion of high-speed stars was the proverbial search for a needle in a haystack,” Maximilian Haberle, a research scholar and team member, said in a media release. The search resulted in seven “needles” — tell-tale stars indicating the black hole.

Neumayer said Omega Centauri is believed to be the left-over nucleus of a dwarf galaxy that merged with the Milky Way a long time ago. “In this merger, the galaxy lost all its gas and the growth of its own central black hole was interrupted, leaving it in an intermediate mass state,” Neumayer said.

“This is a cool result — the strongest evidence yet that Omega Centauri has an intermediate-mass black hole,” said Varun Bhalerao, an astrophysicist and associate professor at the Indian Institute of Technology, Bombay, who was not associated with the study.

“Intermediate-mass black holes were like a missing link — you can’t go from 150 solar mass black holes to millions to billions of times even bigger without something in between,” Bhalerao said.