Scientists have discovered a huge collection of more than 100 black holes in our own galaxy.
The black hole is in the center of a star cluster more than 80,000 light years from us. There are about three times as many black holes as scientists think.
In billions of years to come, the stars themselves will be ejected, leaving only the black hole itself.
This discovery helps us understand the mysterious star cluster known as Palomar 5 and how it could develop in the future.
But it could also help us understand the fate of other similar clusters in our galaxy.
It might also help us explain a strange phenomenon recently discovered in our galaxy, a thin stream of stars that seem unrelated to such a cluster.
Clusters of black holes like Palomar 5 could have generated these unexplained currents, the researchers suspect.
“We don’t know how these currents formed, but one idea is that they are disrupted star clusters,” said Mark Gieles, who works at the Institute of Cosmosciences at the University of Barcelona and is the lead author of the paper.
“However, none of the recently discovered currents are associated with star clusters, so we can’t be sure. So, to understand how these currents form, we need to study them with the associated star systems. Palomar 5 is the only case that makes it a Rosetta Stone to understand river formations and we are therefore examining it in detail,” he said in a statement.
Palomar 5 is in the “Galactic Halo,” which is made up of ancient stars circling the Milky Way. This is one of the thinnest clusters in the halo.
It is also known for its two long “tails” consisting of a large stream of ejected stars. These tails stretch across the night sky, allowing scientists to use them as the key to understanding how they formed throughout the universe.
In the new study, scientists simulated the life of the stars in the cluster individually. Researchers can’t search for black holes themselves — as the name suggests, they’re impossible to see — so the new study relies on methods to figure out how many there are.
“Most of the binary black hole mergers are believed to have formed in star clusters,” said Fabio Antonini, a study co-author from Cardiff University.
“The big unknown in this scenario is how many black holes there are in the cluster, which is hard to quantify because we can’t see black holes. Our new method gives us the opportunity to tell how many black holes there are in a star cluster just by looking at the stars they emit.”
They suggest that these two defining features – its sparse structure and tail – could be the result of 100 black holes, which together make up 20 percent of their mass.
There are so many of these black holes, and together they are so massive that the stars disappear faster than black holes. Thus, in the simulation the cluster then expands and the tail grows.
Eventually the black hole in the cluster will have such an attraction that all the stars will be thrown out and consist only of black holes.
It could be the same story about another stellar stream that once inhabited the cluster before being ejected from the black hole living in the vicinity, scientists suggest. They don’t appear to be related to a cluster because the original suffered the same fate as Palomar 5 will one day, the researchers said.
The results are reported in a paper entitled “A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5” was published in Natural astronomy.
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