010011100000 t1_irhcjar wrote
If it has an event horizon it's by definition a black hole. That's what defines a black hole, not the singularity. According to general relativity any black hole inevitably forms a singularity (under some pretty safe assumptions) so any object that forms an event horizon will also result in a singularity. But we believe that general relativity isn't accurate near the center of a black hole and needs to be replaced by a theory of quantum gravity, and that this will get rid of the singularity
ExactCollege3 OP t1_irhlv9c wrote
So how do we know if something is a singularity? So it’s kind of an assumption that this happens every time by general relativity? And what part of it leads to that?
If I’m hearing right, yes some neutron stars could gain enough mass to become black holes, and we’re not sure yet if all black holes are singularities because not everything adds up right and a new rule could be discovered?
mfb- t1_irhnkkz wrote
> So how do we know if something is a singularity?
We do not. It's a strong prediction of general relativity because inside a black hole, all possible trajectories lead towards the center (or a ring for rotating black holes): Trying to stay at a finite distance is as impossible as trying to stay in Sunday.
> If I’m hearing right, yes some neutron stars could gain enough mass to become black holes
Yes, because they collapse above a certain mass. They are not neutron stars any more if that happens.
DoodDoes t1_irixcna wrote
The Schwarzschild radius would be a good thing to look up to learn about when and why a black hole forms. And the event horizon is basically the point where we have to rely on math rather than observation to be able to tell what’s going on. But the same used to be true for black holes themselves, and the math held up for that
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