Black holes form when a massive star runs out of fuel.  Gravity causes the core to collapse down to an object so dense that light itself can not escape.  In the Milky Way galaxy, there are expected to be over 100 Million black holes, though of course we can’t see them.  The one we can see is the supermassive black hole Sag A*, lying deep within the core of the galaxy.  But how did Sag A* form? Was it from the merger of many smaller black holes?  Or is there some other process forming the most enigmatic objects in the...