Is there a limit to how much mass a black hole can hold?

Answer

In principle, such a limit does not exist. A black hole is a mass concentration whose escape velocity is greater than the speed of light. For every possible mass you can calculate with a radius within which all that mass together forms a black hole. For the Sun that is 3 km, and for other masses it is simply proportional to the mass. So for the Earth (300 thousand times less mass than the Sun) it is 1 cm.

The question is rather how to make black holes. Mass cannot simply contract, the rotation of a contracting mass prevents further incidence. And when matter strikes a black hole, that impact generates energy that creates an outward pressure that makes further impact more difficult. All these processes are partly responsible for the fact that the physics of black holes in the universe is a very interesting research topic. It seems that they make it very difficult to create black holes larger than about 10 billion solar masses in our universe.

With some good will, our entire universe can also be regarded as a black hole, since light cannot by definition get out. But that is not conceptually very illuminating. Such as a connection between black holes and new universes that is not real. It’s true that too much incursion on the supermassive central black holes at the centers of large galaxies leads to mass repulsion, but those are “just” explosions in our universe, not new universes.