Enormous Black Holes

Ordinary black holes form when large stars collapse under their own gravitational force. Stars start out with fusion fires in their cores, which generates enough countervailing pressure to keep them inflated. When the fuel burns out, the pressure from the high temperatures diminishes, and they collapse. If there is enough matter in the star, the matter condenses to neutronic matter, which is at the density of an atomic nucleus. This results in something tiny, Earth-sized, as opposed to normal star sized. This means the gravitational potential well is much deeper, and even photons have a hard time escaping. With enough matter, they can’t, and we have a black hole. It takes about 10 solar masses to do this. Stars in our galaxy go up to about 100 times solar mass, so there are very many candidates for future black holes. These massive stars burn very hot, so their lifetimes are short, and the galaxy is old, meaning there should be a lot of them around.

If you look at an globular cluster with a good telescope, you will see a million or many millions of stars, all pulling themselves together into a kind of tiny spherical galaxy. If you look closely, the hottest, heaviest stars cluster in the center. That’s simply a result of random motions in the cluster, where one star interacts with another star, sharing angular momentum and kinetic energy. The lighter stars are easier to kick around, so heavier ones lose some velocity and drop closer in toward the center. They don’t loose too much and collapse into a tiny volume, but the average distance to the center drops, and they make the core of the globular cluster nice and bright, yellow and blue.

These stars have been doing it for a long time in many globular clusters, meaning there would be a lot of black holes around, and they would be in the center as well, since their masses are about the same as the heavier stars. But they are invisible. There would be a range of neutron stars as well, also mostly invisible, and since they are lighter than black holes, they would range out farther in the cluster.

The center of the galaxy should have experienced the same phenomena, and should be full of heavy stars and black holes. Astronomers cannot see the black holes there, but they can map the gravitational potential by seeing how fast stars orbit near the core, just like we can see planets moving faster as they are closer to the sun. This provides an idea of how much mass is inside these orbits. For some unknown reason, there seems to be the idea that instead of a swarm of black holes in the center of the galaxy, there is a giant, enormous, single black hole. It would be impossible to tell the difference, and there is no obvious mechanism by which the matter in the galaxy could form an enormous black hole in the age of the galaxy, but the idea persists. A swarm of ordinary black holes could be the source of the gravitational potential, and that is a simpler idea.

But can enormous black holes exist? Do a thought experiment. Forget about time, and just imagine some immensely later time in the universe. Black holes are, so far, known only to be a one-way street for matter, and keep gobbling up anything which ventures too close to them. Suppose you are in the universe after immense amounts of time have passed, and black holes kept forming and kept accreting matter. Now there is nothing left in the universe except black holes and a bit of legacy matter. Sooner or later, actually, much later, black holes get close enough to one another and lose relative velocity, and if this happens enough, maybe quintillions of years, a binary black hole will form and tidal interactions will toss off gravity waves, carrying away the angular momentum, and they will spiral down until they merge. Again, this is a one-way street. So keep watching, and black holes will get larger and larger, but it might be a very long time.

As you keep watching, the average black hole mass will keep getting larger and larger. There is nothing known to stop this. So, from 100 solar masses to 1000 solar masses to a million and a billion. Now you have enormous black holes.

What is going on inside a black hole? The small ones have neutronic matter, as they form from neutron stars. Earth science does not know what other, more dense states of matter might be. At some pressure, do neutrons disassociate into quarks, leaving quark matter black holes? Actually, it there is a state of matter more dense than neutronic matter, it would start forming at the center of a black hole, and as more mass were accreted, increasing the pressure, the core area of quark matter or whatever matter would expand, growing larger and larger. No one has even a faint clue of what the mass required for such a transition might be. Are there further states beyond quark matter? Maybe…

Does something go wrong with the equations of general relativity at these high gravitational fields? Does it break down just like classical physics breaks down when size gets too small, requiring quantum mechanics and similar theories? The important point is, does gravitation cease when density gets too high? This might happen through an imperfection in the theory of gravity, or it might happen from the equation of state of matter at very high densities. In essence, do quarks carry gravitational force, or does it go away when a neutron oozes into a set of three quarks?

If gravitation goes away at insanely high densities of matter, we would have an instability inside a huge black hole. And the change to non-gravitational matter would have to occur at the core of the huge black hole, meaning it would want to rise to the surface. This type of instability is called a Rayleigh-Taylor instability, and it explains why you cannot have a water layer on top of an oil layer. It just inverts abruptly, no matter how carefully you do the pouring. So, if there is a cessation of gravitation inside a single, massive, gigantic, enormous black hole, you have an explosion. It might be called “The Big Bang”.