Ethan Siegel,Forbes
How many black holes are there in the Milky Way? This straightforward question has proven extremely difficult to reply, since black holes are so difficult to directly detect. However, or scientists not only have developed indirect methods for locating and even weighing them,we also understand how the Universe forms them: from stars and stellar remnants. whether we can understand the different stars that existed at all different times in our galaxy's history, we should be able to infer exactly how many black holes and of what mass exist in our galaxy nowadays.
Source: realclearscience.com