Question: can a black hole absorb a black hole?

Alexander Burke answered on 5 Mar 2018:

Absolutely! Black holes are dynamical (they move around) and so it’s very common for one black hole to smash into another and become a larger black hole. For example, on the 14th of September, 2015, we managed to detect the collision of two black holes. Approximately 2 billion years ago, 2 black holes which weighed 29 and 36 times the mass of the sun smashed into each other forming a larger black hole. The new black hole weighed 62 times the mass of the sun and released an incredible amount of energy in the form of gravitational waves (wobbly gravity – read my description of you’re curious!).