It's really easy now in 2.2; just set some manned science ships to patrol in and out of a black hole system. You'll eventually get it. If I have one near by at the start of the game, I usually dedicate a science ship just to the system because the bonuses from the end of the event chain are too good. 60% habitability on everything on my main species? Yes please. A bunch of tomb worlds to colonize and later turn into ecumenopolises? Hell yeah. I'm actually a bit sad it's too easy to cheese now, because at least before you had to queue up a ton of move actions, but now you just set it and forget until the event pops up.