Rare intermediate-mass black hole discovered

A new possible example of an intermediate-mass black hole has been identified, an extremely rare object that represents the link between stellar-mass black holes and supermassive black holes. The bright X-ray source, called NGC 6099 HLX-1 , was located in a globular cluster within a giant elliptical galaxy by the Hubble Space Telescope and NASA's Chandra X-ray Observatory. The results of the study, which also involved researcher Roberto Soria of the National Institute for Astrophysics in Turin, are published in The Astrophysical Journal. Intermediate-mass black holes range in mass from a few hundred to hundreds of thousands of times that of the Sun and are very elusive. Neither too big nor too small, they are often invisible because they do not devour as much gas and stars as supermassive black holes, which, thanks to this process, emit powerful radiation and are visible. The new possible specimen identified by Hubble and Chandra is located on the outskirts of the galaxy NGC 6099 , about 40,000 light-years from its center . The galaxy itself is about 450 million light-years from Earth , in the constellation Hercules. The X-ray emission from NGC 6099 HLX-1 has a temperature of 3 million degrees , consistent with the possibility that the intermediate-mass black hole is having a 'snack': Hubble has in fact found a small star cluster nearby that could offer it a hearty meal. The putative intermediate-mass black hole, first observed in 2009 , reached its maximum brightness in 2012 , and then continued to decline until 2023. "If it's eating a star, how long will it take for it to swallow its gas?", asks Soria. "We have to wait and see if it will have further peaks of activity, or if there was a beginning, a peak, and now its brightness will decrease until it disappears."