At www.jpl.nasa.gov/news/news.cfm?release=2012-265&cid=release_2012-265 … we learn that the WISE mission, which ended last year, discovered what they say are millions of black holes. Millions of them, as in lots and lots. They also discovered lots of hotDOGs (cloud obscured galaxies).
WISE was one of the most successful NASA missions. It found an asteroid 'dancing about' close to the Earth and its orbit, for example, lots of comets and near earth objects, cold star like orbs, and supermassive black holes as well as those galaxies in hiding, obscured by swirling clouds of dust. Scientists say they have found two and a half million 'actively feeding' black holes in the wide sky array – using infra red light. They can be seen as they glow in the infrared – and now we have NuSTAR that is looking at high energy X-ray light (so more surprises in store in the future).
See also www.nasa.gov.wise …. http://wise.astro.ucla.edu … and http://jpl.nasa.gov/wise