Reading about the amazing Parker Solar Probe, (Parker Solar Probe - Wikipedia), gets me to thinking:
Is there a theoretical limit to the temperature of a solid material ? (of course, under enough pressure, a solid can be very hot)
So far it looks like it’s this stuff:
Per your OP, this is indeed theoretical; this material doesn’t exist yet.
For comparison, the reinforced carbon-carbon heat shield on the Parker probe maintains its mechanical strength at temps up to 3600F. I guess that means it can go hotter if you’re willing to tolerate some loss of strength, but the Wikipedia page didn’t mention the upper limit at which it simply starts to ablate.
This page suggests “carbon fiber reinforced carbon” can handle 4900F in a vacuum.
Tungsten is very nearly as good, at 6,191 F (3695 K).
At some point, under almost any pressure the electrons will be moving fast enough to no longer maintain orbit and the material will become a Plasma.
By volume an mass plasma is most common phase of ordinary matter in the universe and is the state of mater within the sun.
Basically are nuclei swimming in a sea of free electrons.
Neutronium perhaps? k not a solid bit it’s own thing.
Some other exotic state of matter?
Or perhaps we don’t need solid and can work with a plasma.
It’s a rather different state of matter of course, but the surface of a neutron star may be solid, in the sense that atomic nuclei are arranged in a fixed lattice, up to a temperatures of 10^6 K.
That is an interesting article and I enjoyed the read, but as this is GQ I do want to point out that in general the phase of matter called “solid” is primarily considered a chemical bonds through the electrostatic force or covalent bonds etc…
With no net electrical charge a sphere of neutrons probably needs a new term vs “solid” and it’s bonding.
But very interesting.
Well, that’s debatable. The article that you linked to is a classification among solids, and may not be exhaustive. That article does not offer a definition of how a solid is distinguished from other states of matter, but here’s a reasonable one:
The matter on the surface of a neutron star is certainly exotic, but it satisfies this definition of a solid. The technical term for it appears to be a Coulomb solid; and it would indeed “melt” into an exotic liquid at a higher temperature.
A neutron star isn’t just a sphere of neutrons. It’s mostly neutrons, but perhaps 10% of its mass is from protons, with a corresponding number of electrons. And that’s in the interior of the star: The crust is still discrete nuclei (albeit nuclei with far more neutrons than would be stable under low pressures) interacting with each other via their charges and the electrons around them.
The interior of a neutron star is a fluid (in fact, a superfluid), so not eligible for this thread, but it’s not fluid because it’s melted: Despite temperatures of millions of degrees, a neutron star can be treated, to an excellent approximation, as being at zero temperature. The thermal energy is insignificant compared to the Fermi energy.
fyi I wasn’t referencing the interior when I said the surface would “melt” at higher temperature. The model apparently predicts that the surface would be a crust for stars below 10^6K, but a liquid (still consisting of discrete atomic nuclei) above that surface temperature. It seems reasonable to describe the transition at a certain temperature between Coulomb solid and Coulomb liquid as melting.
The mention of hafnium-nitrogen-carbon and tungsten and their respective melting points assumes conditions at the surface of the earth. If you bury those substances deep below the crust of the earth, they will remain solid far beyond those melting points mentioned.
In fact, this is what causes volcanic eruptions. A so-called mass of magma is really just a solid, slightly plasticky mass of rock slowly floating upwards, with temperature well in excess of its melting point at the surface. No harm in that but when there’s a sudden reduction in confining pressure, like a plate or crustal movement, the magma will instantly liquefy and move up fast, causing an eruption.
What’s the difference between normal matter and degenerate matter … a solid is discrete atoms held together in position, nuclei with electrons orbiting … white dwarfs and neutron stars are degenerate matter, so much pressure makes more of a bouillabaisse of naked protons in a savory electron sauce … or just a neutron pudding … but there’s not really atoms anymore …
Yes
Well, the electron distribution depends on the type of solid.
As noted in comments above, models of neutron stars describe several different states of matter. There is neutron degeneracy in the interior, but not at the surface. At the surface, regular atomic nuclei (with protons) form a solid lattice, with electrons in a degenerate gas.
FWIW, I was thinking of “ordinary” matter in my question, but please continue this discussion of exotic matter. It’s fascinating
Indeed, has quark degenerate matter ever been observed? … how about matter within a black hole, would this be photon degenerate matter? …
At the other extreme we have Bose-Einstein condensates … something about electrons stretching out and tangling with each other … could someone please give us the StraightDope on this?
There can’t be such a thing as photon degenerate matter, because photons are bosons. All that stuff you hear about “two particles can’t exist in the same state at the same time” only applies to the subcategory of particles called fermions, particles with half-integer spins. It doesn’t apply to particles with integer spins, the bosons, such as photons. Or rather, the actual true underlying rules apply to both, but they manifest in different ways, and the manifestation of those rules for bosons isn’t anywhere near as obvious as the “no two particles in the same state” thing. Under some conditions, fermions can pair up such that the pairs of particles act like bosons, but under no conditions do bosons ever act like fermions, so you can’t have “photon degeneracy”.
At what pressure?
Is there any way to grab hold of neutron star crust and use it at everyday temperatures and pressures? It would be a useful material if it is that strong. You could make giant megastructures. strong cables, rocket engine bells that really do reflect everything, probes that go deep into the Sun (or the Earth); I’m sure this is all unobtainium, but I’m just making sure.
I think if you try, neutron star crust grabs hold of YOU (in Soviet Russia). It’s only the way it is because of the prevailing conditions that created it.
Yes, I know that, but I’m wondering if there is any way that neutronium can be made stable. Or at least metastable, so that it doesn’t explode too easily.
Everything I’ve read says that neutronium would expand into a gas, or plasma, if you brought it away from neutron star conditions, but since the crust is the top part of the star, then surely conditions there are the least extreme.