A pair of supermassive black holes in orbit around one another have been spotted by XMM-Newton. This is the first time such a pair have been seen in an ordinary galaxy. They were discovered because they ripped apart a star when the space observatory happened to be looking in their direction.
Read more on the Science & Technology website: http://sci.esa.int/xmm-newton/53980-unique-pair-of-hidden-black-holes-discovered-by-xmm-newton/