http://www.nytimes.com/2015/01/08/science/in-a-far-off-galaxy-2-black-holes-... https://www.caltech.edu/news/unusual-light-signal-yields-clues-about-elusive... Matthew J. Graham, S. G. Djorgovski, Daniel Stern, Eilat Glikman, Andrew J. Drake, Ashish A. Mahabal, Ciro Donalek, Steve Larson, Eric Christensen: A possible close supermassive black-hole binary in a quasar with optical periodicity, NATURE Wednesday 7 January 2015 http://www.nature.com/nature/journal/vaop/ncurrent/full/nature14143.html If they are right, then two supermassive black holes are in an orbit the size of the solar system, and are going to merge soon (within 1 million years) due to loss of energy from gravity waves it is radiating. The resulting thud is going to be far bigger than anything humanity has ever observed. Matthew J. Graham, S. G. Djorgovski, Daniel Stern, Eilat Glikman, Andrew J. Drake, Ashish A. Mahabal, Ciro Donalek, Steve Larson, Eric Christensen, DOI:10.1038/nature14143