I was going to say the same thing about neutron degeneracy pressure, so I'll add a thought experiment that I haven't seen discussed or answered yet online. This is probably a really old debate, and is maybe settled, but not in layman's terms:

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Imagine we have a neutron star that's 1 atom away from collapsing into a black hole. What does that mean? There are 2 edge cases of interest: 1) when an event horizon begins forming at the core, and 2) when it swallows the surface.

1) Starting with the core event horizon, we can imagine dropping an atom on the surface of the star, and pressure passing the neutron degeneracy pressure limit at its center. A tiny black hole appears in the core, roughly the width of a neutron, and all of the neutrons start slipping down the drain into it, making the horizon bigger and bigger until the star is eventually swallowed.

Except that time passes more slowly in a deep gravity well. It crawls almost to a halt at the center of a neutron star, and halts completely when the event horizon at the core forms. Time may even seem to be running backwards inside the event horizon from our frame of reference.

So my feeling is that this is the point where quantum mechanics stops and relativity takes over. We can treat the event horizon as a black box trying to evaporate outwards with Hawking radiation as hard as the star is trying to collapse into it. In other words, the event horizon feels solid to the star around it.

The test of this is to see how Hawking radiation for the smallest black hole compares to the pressure at the center of a neutron star at the brink of collapse. I'd predict them to either be off by orders of magnitude or exactly equal.

2) Carrying that idea forward, as we add more atoms, the event horizon grows bigger and bigger until it finally covers the surface and we see the star red shift redder and redder until it approaches black.

What happens when we pass the tipping point and 1 final atom causes the event horizon to surround the entire star? Is it like a one-way door, where the black hole stays that way forever?

Well, we can test that by waiting for as much Hawking radiation energy to evaporate as the mass of 1 atom.

Then the neutron star red shifts less and comes back into view. In other words, time gets faster again, the event horizon retreats, and the star blue shifts back into being visible. The longer we wait, and the more Hawking radiation is emitted, the smaller the event horizon gets until it finally disappears completely and the star goes back to being a neutron star.

By this logic, with time running slower and slower, then faster and faster, is it more likely that the neutrons within the event horizon suddenly turn into pure energy and collapse into each other to a singularity? Or is it more likely that they stay how they are, frozen in time, then go back to how they were when the energy representing their mass leaks out in Hawking radiation and then back into the form of a neutron?

This is the central question not being adequately addressed IMHO.

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Now, I don't think that I have broken any rules of physics talking about black hole formation this way. But I'd vote for the latter case where nothing happens to the neutrons, the event horizon just moves outwards and inwards within the neutron star as it gains and loses mass. This may happen in real life when they suck in mass from a neighboring star.

What happens if a white dwarf or neutron star gains a lot of mass this way quickly? Any potential energy remaining in atoms which haven't been reduced to neutrons yet quickly falls beneath the electron degeneracy pressure, goes through the high-pressure slowed space on and within the neutron star, fuses instantly and explodes. Which is called a nova.

So even in the center of an ordinary star like our sun, the high-pressure slowed space presses atoms close enough together to fuse. The rate of fusion is proportional to how slow that space is. The slower the space, the faster the fusion.

Going beyond edge case 2, if we add a lot of matter and it falls beneath the event horizon, it's going to take a long time to evaporate back out, potentially trillions of years. Which is why most black holes that formed naturally probably have so much mass that we'll never see them blue shift back to our frame of reference.

But, I'm probably wrong. Another interpretation is that the slower space at the center of a neutron star is actually longer. So we can imagine the distance to the core getting further away as the star gains mass. When the event horizon forms, the space there starts falling in away from us faster than the speed of light. Meaning that Hawking radiation may not be strong enough to hold the neutrons out. The gravity gradient passes 90 degrees and they fall straight in as if nothing is beneath them.

If that's the case, then the neutrons fall through that pin prick rip in spacetime, maybe turning into pure energy. Their energy comes out the other side where time is running backwards from our frame of reference, so space is ballooning out at the speed of light, possibly with one less spatial dimension, although my gut feeling is that the z axis is just flipped so the number of dimensions probably stays constant.

This would be a white hole and look very much like the birth of our universe in the big bang. Inflation would be the period when spacetime is still flowing faster than the speed of light within the event horizon, until it reaches the radius of the event horizon in that frame of reference and slows below the speed of light again.

The child universe within the black hole would last until the parent black hole evaporates. Inside, it would look like there's an outward pressure causing the child universe to expand (dark energy), powered by the Hawking radiation of the parent black hole. This would push matter outside the child universe's visible universe, whose radius is equal to parent black hole's event horizon radius from our frame of reference, causing the rate of expansion to increase. Eventually more and more matter would escape, lowering the mass of the child universe until the edge of the universe rushes in, pulling an observer in the child universe apart in reverse spaghettification as it gets pulled back into our universe when the parent black hole evaporates completely and explodes. Which might be our universe's fate in trillions of years.

Again, I'm probably wrong about this stuff. But I'm approaching it as a software developer who just thinks of the problem as a bunch of edge cases to test. It would be helpful to know the improper steps in my thought process so that a working solution can be found.

Sorry this got so long, it might have been better to put it on a wiki somewhere.

Edit: added speculation about the source of dark energy.

Edit 2: the time direction in the white hole paragraphs doesn't seem quite right. For example, if time is running backwards inside, then I might have the inflation and reverse spaghettification timestamps reversed.