Mathematical models shed new light on the interior of neutron stars

Neutron stars were first discovered more than 60 years ago, but very little is known about the interior of neutron stars, the incredibly compact cores of dead stars.

Now, a team of physicists from Goethe University in Frankfurt has developed mathematical models that may help to uncover the interior of the mysterious star types.

According to their findings, a press statement reveals, they bear a surprising resemblance to chocolate pralines.

Neutron stars surprisingly resemble pralines

The physicists developed numerous so-called equations of state, and they found that they shed surprising light on the interior of neutron stars. An equation of state reveals the state of matter of an object under a pre-specified set of physical conditions.

The Goethe University team's equations suggest that "light" neutron stars (smaller than about 1.7 solar masses) have a soft mantle and a stiff core, while "heavy" neutron stars (larger than 1.7 solar masses) have a stiff mantle and a soft core.

"This result is very interesting because it gives us a direct measure of how compressible the center of neutron stars can be," explained study lead Luciano Rezzolla. "Neutron stars apparently behave a bit like chocolate pralines: light stars resemble those chocolates that have a hazelnut in their center surrounded by soft chocolate, whereas heavy stars can be considered more like those chocolates where a hard layer contains a soft filling."

Neutron stars are believed to form when a massive star collapses in on itself after a supernova explosion. That is, unless the star is so massive it creates a black hole, instead. They are effectively the stellar remains of a star that has used up all of its fuel.

Uncovering the mysteries of neutron stars

The scientists also made other discoveries by analyzing their equations of state. They found, for example, that regardless of their mass, neutron stars probably have a radius of only 7 miles (12 kilometers), meaning they are the same size as Goethe University's hometown of Frankfurt in Germany.

"Our extensive numerical study not only allows us to make predictions for the radii and maximum masses of neutron stars, but also to set new limits on their deformability in binary systems, that is, how strongly they distort each other through their gravitational fields," explained study co-author Christian Ecker. "These insights will become particularly important to pinpoint the unknown equation of state with future astronomical observations and detections of gravitational waves from merging stars."

While the new findings don't definitively reveal the interior of neutron stars, they do provide the delightful image of countless chocolate-praline-like stars spread throughout the night sky.

In reality, some types of neutron stars have so much concentrated magnetic force, they could rip iron from your bloodstream atom by atom, even at a distance of 1,000 miles (1,609 km). They are some of the most enigmatic and powerful objects in our universe, meaning the more we know about them, the more we understand about the evolution of the cosmos as a whole.