Scientists have possibly discovered a rare, medium-sized black hole located in the spiral arm of a galaxy 100 million light-years from Earth that may be the "missing link" in the evolution of these mysterious cosmic objects.

"In paleontology, the discovery of certain fossils can help scientists fill in the evolutionary gaps between different dinosaurs," Mar Mezcua of the Harvard-Smithsonian Center for Astrophysics, who led the study, said in a news release. "We do the same thing in astronomy, but we often have to 'dig' up our discoveries in galaxies that are millions of light years away."

Using observational data from NASA's Chandra X-ray Observatory and the European Very Long Baseline Interferometry (VLBI) Network, the research team identified what astronomers call an "intermediate-mass black hole" (IMBH).

Black holes are known to come into two main classes: stellar-mass black holes that are around 5-30 times the mass of the Sun, and supermassive black holes, which are found at the center of most galaxies and weigh millions or even billions times the Sun's mass. And as their name suggests, IMBHs fall in between these two classes, with masses ranging from a few hundred to a few hundred thousand solar masses.

Now, researchers have possibly identified one such IMBH, called NGC2276-3c, with a mass of about 50,000 times that of the Sun. This discovery could possibly answer some longstanding questions about how black holes evolve and grow over time.

"Astronomers have been looking very hard for these medium-sized black holes," said co-author Tim Roberts, of the University of Durham. "There have been hints that they exist, but the IMBHs have been acting like a long-lost relative that isn't interested in being found."

Further studies of NGC2276-3c could provide insight into how black holes in the early Universe influence their surroundings, and close an important gap in the black hole family tree.

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