the surprise is that to make an accretion disk which would make any detectable emission, there had to be a lot of matter around a black hole. the accretion dis

the surprise is that to make an accretion disk which would make any detectable emission, there had to be a lot of matter around a black hole. the accretion disks are commonly seen around binaries consisting of a stellar mass black hole and a regular star. stars feeds the disk in this case. another possibility is to have a supermassive back hole in the galaxy center, which feeds on the surrounding gas, making much larger and slowed disk. what has never been seen before a stellar mass black hole (or pair of black holes) feeding on the interstellar medium. This should happen of course, but the expected luminosity is way below anything detectable. binary black hole, i.e. a system without any addition mass to accrete, would have to be in some very unusually dense medium, and the medium would need to be disrupted by merger. interestingly, such medium can occur around another back hole - a supermassive one.