http://www.newsweek.com/there-could-be-invisible-galaxy-hiding-milky-way-thousands-black-holes-1108983

Scientists think that at the heart of nearly every galaxy, including our own Milky Way, lies a supermassive black hole (SMBH) with immense gravity. These SMBHs are surrounded by dense clusters of millions of stars and—according to findings published earlier this year—probably thousands of smaller, star-sized black holes that all orbit within a few light years of the center.

Now, astrophysicists from Eötvös University in Hungary have simulated the interactions of bodies orbiting the galactic center, finding that the more massive objects form a previously unexpected structure around the central SMBH, within which the thousands of predicted black holes may be hiding.