A conceptual image of the newly discovered “large star cluster buried in dust.” It is considered that IMBHs are formed at the center of the cluster. (Photo : Keio University)
Until recently, scientists mostly focused on two types of black holes: supermassive black holes with masses millions to billions that of our sun and stellar black holes with masses a few times our sun. But then astronomers confirmed that something lies in between - intermediate-mass black holes (IMBH). It is thought that the merger of middleweight black holes is what leads to the supermassive black holes in the center of galaxies, and now, astronomers may have figured out how these IMBHs are formed.
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The study was conducted by a team from Keio University led by Associate Professor Tomoharu Oka. They used radio telescopes to identify a possible birthing ground for the IMBHs about 30,000 light years from our solar system near Sagittarius, the center of our galaxy. They found four "warm, dense" molecular gas clouds, one of which is believed to contain the supermassive black hole at the center of the Milky Way.
The gas clouds are hard to peer through, so the scientists rely on other readings such as energy.
Of the remaining three gas clouds, one stood out for its immense expanding energy. The energy of its expansion was the equivalent of 200 supernova explosions. Supernovas are explosions that occur when a massive star dies. The age of the gas clouds are estimated to be around 60,000 years, which would mean a supernova every 300 years.
The rate of supernovas is incredibly high, and must mean there are an incredible number of stars in the gas clouds. The astronomers calculated that the mass of the star cluster must be around 100,000 times the mass of our sun. This is equivalent to the largest star cluster in our galaxy.
The working theory is that when these star clusters become so dense, stars actually merge, and it is in these dense clusters that IMBHs are born. These IMBHs, in turn, could expand or merge into a supermassive black hole. The location of these gas clouds so close to Sagittarius A, the gas cloud containing the Milky Way's supermassive black hole, could explain how our galaxy got its supermassive black hole.
The findings support the theory released just a few days earlier that IMBHs form in gas clouds near supermassive black holes.