Nothing more wonderful in heaven
Than black hole OJ287
The mass of OJ287 is equal to 18 billion Suns (see Saturday's post). That's about a thirtieth of the mass of the Milky Way Galaxy. By my calculation, all of that mass must be contained in a volume with a radius about the size of the Solar System (including the realm of the comets beyond Pluto). In other words, roughly, to make a black hole like OJ287, you take a smallish galaxy and squeeze it down to something the size of the a planet system. That's the equivalent of squeezing the Earth into a space the size of this letter O -- which would turn the Earth into a black hole.
Now suppose that I give you as a present an O-size black hole, in a jewel box made of an antigravity material. You open the box...
I will leave it as an exercise to our physicist commenters to describe what happens next.