Years after ripping stars to shreds, 24 black holes suddenly flared up with radio waves in inexplicable 'burping' bouts. Half of all star-killing black holes may experience the same.

Black holes keep 'burping up' stars they destroyed years earlier, and astronomers don't know why

Source: space
Source Link: https://www.space.com/black-holes-burping-stars-astronomers-stumped