“Nuclear pasta”: Is this the strongest material in the Universe?
When measuring the strength of a material, it is a little more complicated than measuring just strength or hardness. Steel, diamond and even the wonder material graphene are strong, but the strongest material in the universe could be the “nuclear pasta“.
This is a strange substance formed in the intense pressures inside neutron stars. Now, on the basis of computer simulations to test just how strong it is, researchers have now concluded that nuclear pasta is the strongest material in the universe.
Nuclear Pasta: What exactly is it?
When stars of a certain size die, they explode as supernovae. In the explosion, they throw off their outer layers and leave behind a dense core that collapses inwards. Then the core can form a neutron star, cramming the mass of a Sun or two into an object about 10 km (6.2 mi) wide. That incredible density of material gives rise to some pretty strange phenomena.
One of these is nuclear pasta, which is essentially a solid structure of neutrons held together by their mutual attraction. It forms in the extreme conditions inside the neutron star, and has some unusual properties. For instance, it conducts heat very effectively, but cannot conduct electricity (or electromagnetic radiation at all).
Nuclear pasta is so dense that a teaspoon of it would weigh over a billion tons. Models say nuclear pasta is a trillion times denser than water. At this level of density, they predict that the star’s nucleons – mostly neutrons but also protons – practically touch, forming dense spaghetti-like strands or lasagna-like layers within less-dense voids. But the question still remains: How strong is this stuff?
Questioning Pasta Strength: How it was tested?
To work out how strong the nuclear pasta really is, researchers used computer simulations to see if this strange substance could withstand different pressures under different circumstances. The team created 15 different types of nuclear pastas and then subjected them to different compression techniques (including pressure, shear and torsion), trying to find out where they broke and what happened at every step. The results were then compared to simulations of neutron stars in the lab to determine which of the pastas could survive indefinitely.
To test the effects of pressure, they simulated a zero-gravity environment and then created an artificial gravity field around it and tried increasing the gravitational pull until the pasta began to break. The team also set up a torsion model where they surrounded a solid (made out of nuclear pasta) with rings that exerted pressure against it, and then twisted them.
“Nuclear pasta is so strong under pressure that if you were able to squeeze material made from nuclear pasta in a laboratory, it would be like turning coal into a diamond,” explains Caitlin Casey from Carnegie Mellon University, who was involved in the study. “But nuclear pasta is so strong under torsion that the material it’s made out of would be like turning diamonds into coal.”
The results of the simulations showed that, when subjected to a shear force, nuclear pasta breaks like glass. And when subjected to compression, it breaks even harder than glass. Under normal conditions, though, nuclear pasta is almost impossible to break. It has just enough flexibility in it to allow for a shear break in which the outer layers can come off before impacting other material with greater strength. But it is extremely hard to compress without shattering.
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Is “Nuclear Pasta” stronger than the material in a black hole?
The results of the simulations can now be compared to other experiments that have been done in the lab in order to calculate the strength of the material. For example, they found that nuclear pasta is incredibly strong under pressure, but it’s not much stronger than steel under pressure.
“Our results have shown that nuclear pasta is very strong under normal conditions, but it’s also very strong when you push it to its limit,” says Casey. “If you could squeeze that material and make it even denser, it would be more than twice as strong as neutron-dense iron. That means an object made of nuclear pasta would be twice as strong as a black hole.”
Just how strong an object can be before it becomes the strongest material in the Universe? That is something scientists will have to figure out. For now, though, nuclear pasta appears to be a very strange and extremely strong material.
Today is 2022, and to-date, the strongest material in the Universe is “nuclear pasta”.
The team’s paper has been published in the journal Physical Review C.
