crushing->1:new element?2:how far?

I once understood that a neutron star is a star that has spent all of its fuel and clasped under its own gravity so much that the electrons and protons combine to form neutrons, and that is all that it in there if this is true, it brings up 2 questions
1: can a neutron star be considered an element with an atomic number of 0 and atomic mass of 10^x where x is a very large number?
2: going further to blackholes how much further can matter compress past the all neutron level- can it be compressed to a single point?

1 - sort of. It can be considered a giant neutral nucleus. To be considered an element, it’d be better to have a nucleus of protons and neutrons with a cloud of electrons. Neutron stars don’t have free electrons.

2 - That’s exactly what black holes are: matter that has been compressed to a single point. Beyond a certain point, no known force, including degeneracy (neutrons touching each other), can prevent compression. Logically, it must contract to a point.

I’d opine that a big nucleus is not really a terrific definition for a neutron star since the word itself means the center (of a larger particle), which a neutron star is not. We needn’t postulate on the valence of a neutron star unless I can call Elvis as a witness.

And I would stick my neck further over the block by stating that a ‘black hole’ comprises everything within it’s event horizon, not just the singularity at the center.

I’m not a physicist but I am certainly well equipped to deliver a dissertation on the subject of energy loss from particle decay through aging…especially in one 53 year old male.

Well, actually, a neutron star does have protons and electrons, but they’re in the minority. if I recall correctly, neutrons only make up something like 80% of the total mass-- This still leaves a heck of a high atomic number, if you insist on calling it that. I’d say that it isn’t, personally, just because it’s bound by gravitational forces, and not the strong force, as true nuclei are.

And tcburnett is right: Usually, when physicists speak of a black hole, they mean everything inside the horizon. The smaller the black hole, the higher the density, but there’s probably a lower limit on the size of a black hole-- Welcome to quantum gravity.

Thanks for the clarifications - I didn’t know that about neutron stars, Chronos. Interesting.

And, yes, black holes include everything in the event horizon. But still, all the mass within the event horizon is compacted to a point, right? It’s just that the gravitational pull is inescapable out to the horizon. The horizon does not delineate the position of the mass.

I agree with Chronos about the make-up of a neutron star.

Smeghead - yep, matter/energy is compacted into the singularity of a black hole. The event horizon is not a physical thing, it’s the distance from the singularity at which the escape velocity is the speed of light. IIRC, however, I think the effective mass of a black hole is measured at the event horizon - I forget the rationale at the moment - anyone RC?

Because the size of the event horizon is directly related to the gravitational pull of the black hole, which is directly related to the mass of the black hole.

Small mass=less total gravitational pull=small-diameter event horizon

large mass=greater total gravitational pull=large-diameter event horizon
The event horizon is simply the distance from the center of the black hole where the escape velocity from its gravity is equal to the speed of light. This distance is farther out for more massive bodies than it is for small bodies.

Quoth Smeghead:

The short answer is, we don’t know. The long answer is, that we can’t know. All we know about the distribution of mass inside a black hole is that it’s spherically symmetric. In order to determine more than that, we’d need to make measurements from inside the hole, and we could never transmit those measurements out. This is part of what’s called the “no hair” theorem, which states that a black hole can be completely described by its mass, electric charge, magnetic charge, and angular momentum, and no other quantities.

OK, good point. Not to beat a dead horse - we never do that here, after all - but, although we can’t go in and check, as Chronos pointed out, as far as we know, there is no force that could prevent a collapse into a singularity. OTOH, because we can’t check, there may be some force that only acts within an event horizon, so as Chronos said, we can’t know.
I think we’re all in agreement here.

Damn. I just passed my 400 post mark and didn’t even notice.

The smaller a black hole is, the denser it is. So for black holes that form from the collapse of a neutron star, you probably don’t get any physical state denser than neutronium. But to get a less massive black hole, you’d have to compress the matter much more densely. Our understanding of physics gets a little spotty at that point, but you might have something like a quark plasma.

Also, if you could make a black hole entirely out of one kind of nuclear particle, could you end up with a black hole that has “strangeness” or a “baryon” value?