\n Supermassive black holes occasionally devour or merge with other black holes<\/p>\n MARK GARLICK\/SCIENCE PHOTO LIBRARY<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n Three galaxies with supermassive black holes at their centres appear to be in the process of merging into a single, giant galaxy, a process that astronomers have rarely seen.<\/p>\n To grow to such enormous sizes, astronomers think supermassive black holes must occasionally devour or merge with other massive black holes during collisions between galaxies. This process is difficult to spot, both because these mergers are short-lived compared with the lifetime of the black hole and because the black holes can only be easily seen if they are giving off light from actively feeding on material, which is also rare. As a result, astronomers have only caught around 150 pairs of galactic black holes in the act of merging.<\/p>\n <\/p>\n Now, Emma Schwartzman at the US Naval Research Laboratory in Washington DC and her colleagues have found a group of three supermassive black holes, all actively feeding, that appear to be combining into a single system. \u201cThe more galaxies involved, the rarer the system gets,\u201d says Schwartzman.<\/p>\n Each of the supermassive black holes is emitting low-frequency radiation in the form of radio waves, which can pass through dust that blocks other light. This allowed Schwartzman and her team to observe them with two radio observatories, the Very Long Baseline Array in Hawaii and the Very Large Array in New Mexico, then rule out that the light was coming from another source, like bright galaxies full of stars.<\/p>\n \u201cWhat\u2019s really interesting is that all three of these [black holes] emit in the radio regime, which we\u2019ve never seen before,\u201d says Schwartzman. \u201cThere\u2019s no guarantee that any [black hole] would emit in the radio regime.\u201d<\/p>\n There are already visible signs that the galaxies have begun interacting with each other, says Isabella Lamperti at the University of Florence, Italy, but they are at a relatively early stage of interaction, given that two of the galaxies are still separated by around 70,000 light years and the third is 300,000 light years away.<\/p>\n But relative to their total lifetime of billions of years, we are witnessing the end of the story. \u201cIt\u2019s like catching the final moments of a galaxy-merging soap opera,\u201d says Emma Kun at Ruhr University Bochum in Germany.<\/p>\n Simulating how three active supermassive black holes merge is extremely difficult, she says, but observing this system will allow physicists to better understand what happens in more complex mergers. \u201cThis is the first step of finding some physics about the system,\u201d says Kun.<\/p>\n Spend a weekend with some of the brightest minds in science, as you explore the mysteries of the universe in an exciting programme that includes an excursion to see the iconic Lovell Telescope.<\/p>\n<\/p><\/div>\n<\/p><\/div>\n<\/section>\n Topics:<\/p>\n<\/section><\/div>\n![\"Jodrell](\"https:\/\/images.newscientist.com\/wp-content\/uploads\/2025\/01\/15113200\/img_6300.jpeg\")
\n <\/picture>\nMysteries of the universe: Cheshire, England<\/h3>\n