'Like Monsters Hiding Under Your Bed'
"These black holes are relatively close to the Milky Way, but they have remained hidden from us until now," Ady Annuar, postgraduate researcher at Durham University said.
However, the hidden monster black holes are no longer inconspicuous thanks to the "advent of NuSTAR," Professor David Alexander, research co-author and Durham's Department of Physics added.
"These hidden monsters have been predicted to be fairly abundant in our Universe. It is only after the advent of NuSTAR that we began to find each of them one by one," Professor Alexander said.
Daniel Stern, project scientists for NuSTAR at NASA's Jet Propulsion Laboratory said: "It is exciting to use the power of NuSTAR to get important, unique information on these beasts, even in our cosmic backyard where they can be studied in detail."