Researchers from Goethe University Frankfurt conducted a large-scale simulation of the equations
In his study, published in TheAstrophysical Journal Letters, scientists have developed over a million different equations of state for neutron stars. All of them, on the one hand, correspond to the laws of theoretical nuclear physics, and, on the other hand, to astronomical observations.
When evaluating the equations of state, especially the velocitypropagation of sound inside such objects, scientists have made an unexpected discovery. "Light" neutron stars, whose mass does not exceed 1.7 solar, have a soft mantle and a hard core, while the internal structure of heavier stars has a reverse structure. In addition, regardless of mass, the diameter of such space objects does not exceed 12 km.
Artistic illustration of stars resembling pralines. Image: P. Kiefer/L. Rezzolla, Goethe University Frankfurt
The researchers note that neutron starsreminiscent of chocolate pralines: light stars are like hazelnuts surrounded by soft chocolate, while heavy stars can be considered more like those candies where the hard layer contains a soft filling. The results of the study will make it possible to predict the radii and maximum masses of neutron stars, as well as determine how they will be deformed in binary systems.
Despite a significant number of observations aboutneutron stars, while very little is known, the authors of the study note. Such space objects are formed after the death of a star: the mass of our Sun or even more is compressed into a sphere with a diameter of a large city. Such ultra-compact conditions are difficult to recreate in an Earth laboratory, and therefore modeling extreme conditions inside neutron stars remains a big challenge.
Therefore, there are many models in whichvarious properties, from density to temperature, are described using equations of state. They model the structure of neutron stars from the surface to the inner core.
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On the cover: an artistic illustration of a neutron star. Image: NASA