Ask Ethan: How many Black Holes are there in the Universe? (Synopsis) [Starts With A Bang]

“Black holes are the seductive dragons of the universe, outwardly quiescent yet violent at the heart, uncanny, hostile, primeval, emitting a negative radiance that draws all toward them, gobbling up all who come too close…these strange galactic monsters, for whom creation is destruction, death life, chaos order.” -Robert Coover

For the third time since it began taking data, the LIGO collaboration discovered direct evidence for merging black holes in the Universe. There’s an incredible amount we’ve learned about black holes and where they’re located, however, and very little of it comes from gravitational waves.

Instead, we know how black holes are made, where their progenitors are and were located, and how they’re likely to be distributed today. If we put this picture all together, we can come up with a numerical estimate for how many are likely to be present in our galaxy, along with where they’re expected to be concentrated. It’s an incredible picture!

Just a few decades ago, we weren’t sure black holes even existed; now we think we know where millions ought to be in every galaxy. Come get the remarkable story on this week’s Ask Ethan!