Researchers from McGill University measured the strength of material deep inside the crust of neutron stars
A research led by Matthew Caplan, a postdoctoral research fellow at McGill University in collaboration with Indiana University and the California Institute of Technology, performed computer simulations of neutron star crusts. These stars are born after supernovas and possess immense gravitational force that make their outer layers freeze solid. The high density packs the material that makes up a neutron star to have a unique structure. The material is also known as nuclear pasta and the competing forces between the protons and neutrons below the crust cause them to assemble into various shapes. The shapes may include, long cylinders or flat planes that are also known as ‘lasagna’ and ‘spaghetti.’ The nuclear pasta is incredibly stiff, owing to such enormous densities and strange shapes.
The elastic properties of neutron star crusts are related to several observed electromagnetic and gravitational wave phenomena that depend on the elastic properties of nuclear pasta found in the inner crust. With the computer simulations, the researchers were able to stretch and deform the material deep in the crust of neutron stars. The team simulated idealized samples of nuclear pasta to describe the breaking mechanism in neutron stars. The deformed nuclear pasta was arranged into several domains that are similar to ions in neutron star crusts. The results revealed that nuclear pasta with a shear modulus of 1030ergs/cm3 and breaking strain greater than 0.1, is the strongest known material.
The findings are expected to help better understand gravitational waves similar to those detected in 2017 when two neutron stars collided. Moreover, the results suggest that lone neutron stars might generate small gravitational waves. “Our results are valuable for astronomers who study neutron stars. Their outer layer is the part we actually observe, so we need to understand that in order to interpret astronomical observations of these stars,” Caplan said. The research was submitted to the journal Physical Review Letters on July 06, 2018.