NGC 6240 is a well-studied example of a galaxy merger. But the discovery that it hides three supermassive black holes makes it a stunning example of a galaxy formed through a triple merger.

http://www.astronomy.com/news/2019/11/three-supermassive-black-holes-found-lurking-in-one-galaxy-a-first?utm_source=asyfb&utm_medium=social&utm_campaign=asyfb&fbclid=IwAR3gGQ-qjwWRpsGXKGoX-KuzZCIHGirQkdN-Sz2PbShUacnYccMx4j1V4Oo