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We now know that most stellar systems have 2 or more stars orbiting each other. Do we know of any galaxies which have 2 or more super massive black holes orbiting each other? Is it possible?
Yes, there are galaxies with two supermassive black holes in the center, see for instance 4C +37.11
Most likely such galaxies are formed by collision and merger of two galaxies, and their cores have not yet merged. Source
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