Neutron Stars Structure Resembles Chocolate Pralines, With Stiff Mantle and Soft Core [Study]

Less is known about the interiors of neutron stars, which are incredibly compact objects that may develop after a star dies. The energy of the sun, and maybe more, is compacted into a sphere the size of a huge city. Scientists have been attempting to unravel its structure for over 60 years.

Neutron stars, which are among the densest things in the Universe, can have structures that resemble chocolates, with gooey or hard cores. The kind of particle arrangements at those cores are yet unknown, but recent theoretical literature revealing this unexpected conclusion might bring one more step closer to comprehending the bizarre innards of such death stars, as well as the crazy extremes imaginable in the universe.

Neutron stars are magnificent. If scientists considered black holes to be structures with enormous (if not boundless) concentrations of mass, neutron stars play second fiddle there in the Universe's Most Dense Category. When a star with a size of 8 to 30 times those of the Sun runs out of materials to fuse in its center, it is no longer held by heat's release of energy, causing the center to collapse beneath gravity while its shell of encircling gasses drifts off into space. The resultant neutron star has a decreased mass of up to 2.3 times that of the Sun, but it is compressed into a sphere of 20 kilometers (12 miles) wide.

Neutron Stars' Soft Mantle and Stiff Core

The much more difficult task is simulating the harsh circumstances within neutron stars, which are difficult to duplicate in the laboratories on Earth. As a result, there are several frameworks in which various properties-ranging from density to temperature-are defined using so-called equations of state. These equations try to describe neutron star structure from the celestial surface to the internal part.

Now, physicists from Goethe University Frankfurt have accomplished a critical puzzle piece. The research group there at the Institute of Theoretical Physics, coordinated by Prof. Luciano Rezzolla, has created over a million distinct equations of state that fulfill the limitations imposed by data gained from conceptual nuclear physics on the one hand and astrophysical observations on the other. Their findings have been released in The Astrophysical Journal Letters.

The working group made an unexpected discovery when evaluating the equations of state: "light" neutron stars (with masses less than about 1.7 solar masses) appear to possess a soft mantle as well as a stiff core even though "heavy" neutron stars (with masses greater than 1.7 solar masses) appear to have a stiff mantle and a soft core.

Prof. Luciano Rezzolla stated that this effect is very fascinating since it gives us a precise assessment of how compact the core of neutron stars can be. Neutron stars appear to start to behave like chocolate pralines: luminous stars represent those chocolates with a hazelnut in the region bounded by soft chocolate while heavy stars mirror those chocolates with a hard layer containing a soft filling, as presented by Eurekalert.

Identifying Unknown Features of Neutron Stars

The sound intensity, a research emphasis of Bachelor's candidate Sinan Altiparmak, was critical to this revelation, as reported by Phys. This number defines how quickly sound waves travel within an item and is affected by just how stiff and otherwise soft the matter is. Throughout Earth, increasing the speed of sound is also utilized to investigate the planet's interior and locate oil resources.

The scientists were also able to identify previously unknown features of neutron stars by simulating the equations of state. For instance, regardless of mass, they almost certainly have a radius of just 12 kilometers. As a result, they have the same circumference as Frankfurt, the location of Goethe University.

Dr. Christine Ecker, the lead author of the paper, notes that the detailed numerical analysis not only allows them to forecast the radii as well as maximum masses of neutron stars but to establish new constraints on their deformability in binary star systems, that is, how strongly they twist one another through their gravitational fields. She added that such discoveries will be especially useful in determining the undiscovered analytical model with future observational data and detection techniques of gravity waves from converging stars.

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