Astronomers may have discovered the rarest black hole in the Milky Way after spotting an improbably fast cluster of stars at the heart of a nearby star cluster. If confirmed, this cosmic giant, known as an intermediate-mass black hole (IMBH), would be the second largest black hole ever discovered in our galaxy.
IMBHs are an extremely rare subset of black holes, which are larger than stellar-mass black holes but smaller than supermassive black holes. That means they can have a mass between 100 and 100,000 times the mass of the Sun, according to NASA.
In theory, IMBHs should be as common as other types of black holes. However, astronomers have had difficulty locating possible IMBHs or confirming their existence, and they are not sure why. As a result, IMBHs are often referred to as “missing link” black holes. Although several promising candidates have been detected, none have been proven to be real.
A possible intermediate mass black hole
Now, in a recent study uploaded on the preprints server arXivresearchers may have discovered evidence of a large IMBH in the Omega Centauri globular cluster, a compact group of about 10 million stars in the Milky Way located about 17,000 light-years from Earth.
The team compared 500 pictures of Omega Centauri taken by the Hubble Space Telescope and mapped the motions of about 1.4 million stars at the center of the cluster. This revealed at least seven stars that “shouldn’t be there”, the researchers wrote.
This happens because these stars have been observed moving fast enough to escape the cluster’s gravity and fly off into intergalactic space. But despite this, the stars continue to orbit at high speed near the center of the cluster.
“The most likely explanation is that a very massive object is gravitationally pulling these stars and keeping them close to the center of the cluster,” said lead study author Maximilian Häberle, a PhD student at the Max Planck Institute for Astronomy (MPIA) in Germany.
“The only object that can be that massive is a black hole with a mass at least 8,200 times the mass of our sun,” he adds.
Where is the rarest black hole in the Milky Way hiding?
Omega Centauri is an unusual entity: it is about 10 times larger than most other globular clusters, and it is surprisingly flat. It is so massive that it can even be seen with the naked eye on dark, clear nights, when it takes up almost as much of the night sky as the Moon as seen from Earth. scrie Live Science.
Researchers suspect that the cluster may have been a dwarf galaxy orbiting the Milky Way before being pulled into the middle of the galaxy. As a result, scientists have often wondered if there could have been a sizable black hole at its heart.
Researchers first proposed the idea of an IMBH in Omega Centauri in 2008, when Hubble revealed how tightly clustered the stars at the center of the cluster are. However, at the time, other researchers argued that this could be caused by a swarm of several smaller, stellar-mass black holes.
But the very fast stars highlighted in the new study point to the existence of an IMBH, the study authors argue.
When will we learn more about the rarest black hole in the Milky Way?
“This discovery is the most direct evidence yet of an IMBH in Omega Centauri,” said study co-author Nadine Neumayer, an astronomer at MPIA. If confirmed, it would be the second largest known black hole in the Milky Way, after Sagittarius A*, the supermassive black hole at the heart of our galaxy, she added.
“This is exciting because there are very few other known black holes with a similar mass,” says the researcher.
However, the presence of an IMBH in Omega Centauri is not confirmed and more data is needed to know for sure if it is really there. It is also unclear how large the cosmic entity could be and where exactly it is located.
Researchers have been given time in the future to use the powerful James Webb Space Telescope to look deeper into the cluster, meaning we won’t have to wait too long for more evidence of the Milky Way’s rarest black hole.
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Source: www.descopera.ro
