The hardest material in the universe is not graphene, spider web or diamond. It is the crystalline crust of a neutron star. His teaspoon would weigh about 5 tons if it were brought to the surface of the Earth. In the latest paper, astronomers adapted fluid dynamics models to simulate this exotic material.
A popular science discussion on this topic was one of the most read posts in 2023 on the American Astronomical Society AAS Nova website.
A material different from all the others
Almost all visible matter in our universe is in the form of plasma, which astrophysicists are trying to simulate using fluid dynamics models. Solids often require a different modeling approach because they have a property called strength that plasmas do not have. This is the resistance to breakage or deformation. Material strength is a fundamental characteristic of the crust of a neutron star, which is composed of ions that form a crystalline lattice. The crust of a neutron star is the hardest material in the universe. A teaspoon of this exotic matter would weigh about 5 tons if it were brought to the Earth’s surface.
This unusual hardness means that the neutron star’s crust cannot be simulated using typical fluid dynamics models, which do not take into account the strength of the material.
The latest publication by a team of astrophysicists led by Irina Sagert (Los Alamos National Laboratory) addresses this problem of modeling the crust of a neutron star using fluid dynamics models
In the illustration: Snapshots at time “t” (microseconds) of the collision of rubber rings. The color indicates the percentage of sound speed for the simulated particles. Source (CC BY 4.0): I. Sagert et al 2023 ApJS 267 47
Creating a solid body model
Before this model was used to simulate neutron stars, tests were performed for many of the following configurations:
• two rubber rings that collide and crush and bounce against each other;
• spherical metal shell that implodes (i.e. collapses inwards);
• a cylindrical metal bar striking a solid surface.
Although these scenarios seem far from the simulation of the crust of a neutron star, the aforementioned tests show the capabilities of this model to realistically reflect the behavior of a solid body under the influence of various stresses. This model passed each of the tests mentioned above. tests – which allowed astrophysicists to apply it to the main task.
In the illustration: Model of the toroidal oscillations of the crust of neutron stars. Source (CC BY 4.0): I. Sagert et al 2023 ApJS 267 47
Challenges and future directions
A team of astrophysicists used their model to simulate the propagation of toroidal waves in a neutron star with a solid shell. Scientists faced several challenges in doing so:
• The crust makes up only a small fraction of the total volume of the neutron star, so all the computing power is used to simulate the liquid core rather than the crust itself.
• In the simplest case, when a neutron star has no magnetic field, there should be no friction between the crust and the core. However, due to the way calculations are performed in the smooth particle model (SPH), there will always be some friction between the crust and core of a neutron star in simulations.
• Despite its extreme density and hardness, the shell of a neutron star has something in common with gelatin: it is more resistant to compression from all directions than to tearing. This property means that small numerical fluctuations in the density of this crust can become large until they are dampened.
Astrophysicists have explored several ways to deal with the above. challenges and the results of numerical simulations in this model show promising agreement with analytical models.
The search for models of the crust of neutron stars is not over yet, but Sagert and his colleagues see further opportunities to improve it. When relativistic physics is incorporated into the model, a new window opens for accurately modeling the coalescence of neutron stars. This will allow astrophysicists to study neutron star collisions and the huge X-ray flares generated by cracks in their crust with much greater precision than before.
Prepared by: Ryszard Biernikowicz
More information:
Source: AAS Nova
Pictured: An artist’s vision of a neutron star forming after the core of a massive star collapses and the star explodes as a supernova. Source: ESO/L. Calçada
2024-01-01 19:39:36
#model #hardest #material #universe #Urania