There’s a curious gap in the universe when it comes to black holes. Astronomers routinely find small black holes, weighing between five and 100 times the mass of our sun. They also frequently encounter gigantic supermassive black holes, hundreds of thousands of times the mass of the sun or even larger. But finding black holes in between these two size ranges is incredibly rare, a puzzling phenomenon for several reasons.
One key question it raises is how black holes evolve. If they start small and gradually grow over time, then where are all the medium-sized black holes? Conversely, if they only exist in small or huge sizes, why? Our current understanding of black hole physics doesn’t offer a reason why medium-sized black holes shouldn’t exist. This mystery has prompted astronomers to embark on a long search for these elusive intermediate-mass black holes (IMBHs).
Now, the Hubble Space Telescope has provided some of the most compelling evidence yet for an IMBH within our own Milky Way galaxy, specifically within the cluster of Omega Centauri. This cluster, teeming with approximately 10 million stars, has been under close scrutiny by astronomers using Hubble images to catalogue its stars. Amidst this cataloguing process, they noticed something peculiar.
“We discovered seven stars that shouldn’t be there,” explained lead researcher Maximilian Häberle of the Max Planck Institute for Astronomy in Germany, in a statement. “They are moving so fast that they should escape the cluster and never come back. The most likely explanation is that a very massive object is gravitationally pulling on these stars and keeping them close to the center.”
The only object capable of exerting such immense gravitational pull is a black hole, with a mass at least 8,200 times that of our sun. This figure is significant because it firmly places the object within the IMBH size range. Previous studies had hinted at the possibility of an IMBH in this region, but this new evidence is the strongest yet, revealing a relatively nearby IMBH that can be studied further to shed light on black hole evolution.
The researchers are eager to delve deeper into this black hole using the James Webb Space Telescope to precisely determine its mass and position. This research, published in the journal Nature, has the potential to revolutionize our understanding of black holes and their mysterious growth patterns.
