Neutron stars… the name implies that they’re just a big pile of neutrons, packed as closely together as matter can get (without forming a black hole). Yet in another recent thread, it was mentioned that if you took a chunk of a neutron star outside of its environment, then it’ll just expand outward into a big ol’ pile of gooey plasma.
Well… why? Is neutronium (or “degenerate matter”, if you prefer) naturally unstable? Is it possible to stabilize it in any way, short of constantly keeping it under intense gravitational stress?
And, granted, I’m aware that exact info on neutron stars and/or neutronium is sparse, at best.
In answer to the OP: No, you can’t think of it as one giant nucleus. Why not? No protons. There are no atoms with only neutrons at their centers. (Now we go out on a limb:) Technically, it wouldn’t be a nucleus even with the appropriate number of protons; since nuclei are only nuclei within the context of atomic structure, each grouping would be, um, something else.
As to it being unstable when removed from the neutron star environment, the answer is the same: no protons. Since neutrons have no charge, the only things that hold them together are gravity (in the neutron star) gluons (inside an atom). The expansion would be relatively slow and uneventful, since nothing would be forcing the neutrons apart either.
Well, the thing that keeps neutron stars from collapsing is degeneracy pressure, and if you could suddenly turn off gravity, they’d blow up pretty good because to anthropomorphize, neutrons don’t like eachother. This can be contrasted with nuclei, where the neutrons can adequately avoid eachother. (Really, this is a Pauli principle argument, if you object to anthropomorphizing.) In other words, yes, neutronium ought to be naturally unstable. Off the top of my head, I can’t think of any way to stabilize it but of course that doesn’t mean there isn’t one.
Well, I had some nuclear physics in grad school, but I can’t claim to answer this (OP) question either. However, there is the Strong Nuclear Force in play here. I can’t imagine that a small amount of neutronium would explode since the SNF is really strong. My recollection is that neutrons actually stabilize the nucleus of an atom when there are so many protons that the positive repulsive charge (and distances involved with large nuclei) will overcome the SNF. The neutrons add additional SNF to hold things together. Check and see how many neutrons are (required) in stable nuclei as you go up the periodic table.
Maybe g8rguy has it right when he says it will collapse rather than expode.
For large enough nuclei, the strong force ain’t strong enough. Unless there is some energy valley we haven’t discovered yet, every nuclei with more than 209 nuclear particles is unstable.
This issue has been addressed before in several threads. IIRC the consensus was that neutronium can only exist (as neutronium) when the gravitational energy compressing neutrons into this state is insanely high, and the reaction if neutronium suddenly materialized on earth sans this compression, would be akin to a spring being released and the potential to kinetic energy release is what would cause the heat and plasma etc. effects.
Relative to the SNF binding a chunk of neutronium together or interfering with it exploding outward in an earth gravity environment I would think that the gravitational pressure differentials would be several orders of magnitude more energetic in order to compress it in the first place, and the SNF energies would not really figure into keeping neutronium together in a non-hyper gravity environment.
Re: The OP. I wouldn’t consider it a nucleus since the SNF only works on a very small scale, i.e., the size of a large (regular) nucleus. This is one of the reasons why you can’t have really massive nuclei. (Exchange particle lifetimes and all that, I believe.) Hence the physics of the beast is substantially different from a nucleus. It’s like comparing hunks of iron held together by welding vs held together by magnetism.
Suppose you collected a bottle of neutrons. LOTS of neutrons, enough so the blob had detectable weight. Not having any electron clouds to form big puffy atoms, at first they’d fall downwards and form a very thin (and weighty) coating on the bottom surface of the bottle. (Jeeze, I wonder what they’d look like. Silvery? Or like glass?)
You’d have a problem, since lone (non-nucleus) neutrons decay with 10hr half-life, flinging off a high-speed electron and neutrino, and leaving behind a proton. Your bottle of neutrons would be insanely radioactive, would immediately heat itself white-hot, and I presume would act like any white-hot gas.
It’s better to start out with a big chunk of solid hydrogen, then squeeze it down to the size of a tiny speck; until the electrons and protons are crushed together. That way you don’t have to deal with the issue of neutron decay at all. Also, anything that can squeeze hydrogen down to neutronium would by definition keep it that way (keep it from expanding back into protons and electrons.) Besides gravity, what could you use? How about some big pliers made from tightly woven cosmic string? Or a c-clamp made from sintered black hole powder?
My only curiosity about neutronium is using it for flavor text in science fiction stories. And everybody’s got force fields in science fiction. (There was a thread a while ago that talked about that sort of stuff.)
Anyway, I only asked because a debating opponent mentioned that you could essentially just scoop neutronium (assuming you had, like, a really powerful tractor beam or something) out of a neutron star, and it’d cool down and just stay the way it is. His reasoning was that neutron stars - and thus neutronium - was just a really big atomic nucleus.
Except for the fact that “ordinary” matter is only held inside a bottle via electrostatic force whcih a neutron is notable in the fact that it doesnt have any. The neutron would fall through the bottle and through the earth until it got to the center or until it got absorbed by some matter first.
Just a guess, could this material be completely transparent to light, as in truly invisible (no refractive index at all).
As far as I understand, light only interacts with charged particles. This is a pretty interesting quesiton, bbeaty. Can we find anyone on the board that could answer this one with much certainty?
By the by, there are charged particles in Neutron Stars, there just are considerably more (like by an order of magnitude or more) neutrons than anything else. They are not homogeneous objects.
My immediate response would be to say to assume it is room temperatrue. But…
My understanding of QED makes me wonder if the term temperature could even be applied to neutronium. My understanding of temperature of matter to be a manifestation of kinetic energy at the atomic scale, that pieces of the whole wiggle in place. The more wiggling, the hotter the object.
Would the neutrons in neurtonium be able to wiggle in place or would the the construction of the material make it only possible to wiggle at a macro scale?
It would imply to me that maybe neutronium could only be at absolute zero by definition. Or maybe, it could have temperature, but the material would be an extremely efficient thermal conductor (infinitely efficient?) and every bit of a sample would be extremely close to exactly the same temp? It mostly seems to me that the only measure of temperature that would apply to it would be its macro scale momentum.
Or maybe this very problem is part of what makes it impossible to have a small piece of stable neutronium?
I have an extremely hard time imagining what the interaction between normal matter and neutronium would be. If for example, a sample of neutronium could only vibrate as a whole, would it immediately slow/stop the heat vibrations in normal matter touching it? It seems that in touching normal matter, it would try to freeze/cool that matter.
My understanding of single atoms is that in isolation they don’t have a temperature, only a velocity or more accurately a momentum. It seems that a chunk of neutronium would behave like a macro size atom.
If that question was intended to get me to think along these lines, I think I will need another bump in the right direction to get to an answer for myself.