Life is not like a box of chocolates, but it seems that there is something. Neutron stars – some of the hardest things in the Universe – can have a structure very similar to chocolate, with gooey or hard surfaces.
What kinds of changes these centers have are still unknown, but new work revealing this surprising result may bring us closer to understanding the strange, wild, and possible planets in our Universe.
Neutron stars are amazing. If we consider black holes to be the largest (if not infinite) mass of matter, neutron stars win the second place in the World’s Most Popular Prize. After a star with a mass of 8 to 30 solar masses completes its core, it is no longer supported by external heat, causing the core to collapse under the same gravitational pull as its shell. around gases rush into the atmosphere.
The resulting neutron star has a mass less than 2.3 times that of the Sun, but is compressed into an orbit about 20 kilometers (12 miles) across. These things are the main characters of DENSE – and what happens in such situations is what scientists want to know.
Some studies show that the nuclei clump together until they form a pasta-like shape. Some say that even inside the star, the pressure is so great that atomic nuclei cease to exist, becoming a “soup” of quark matter.
Now, physicists led by Luciano Rezzolla of Goethe University in Germany have discovered how neutron stars can resemble chocolate with different fillings.
The team combined theoretical nuclear physics and astrophysical observations to produce more than a million equations of state. These are equations that relate the pressure, temperature, and mass of a given system, in this case a neutron star.
Using this, the team developed a model based on the speed of sound in neutron stars. And this is where it gets interesting. The speed of sound in a given object, be it a star or a planet, can reveal its inner state.
Just as seismic waves on Earth and Mars propagate differently through objects of different densities, revealing shapes and layers, sound waves traveling through a star can reveal what is going on inside.
When the team used their equations of state to study the speed of sound in neutron stars, their results were not the same across the board. In fact, neutron stars at the lower end of the mass spectrum, below 1.7 solar masses, appeared to have a more rigid and denser mantle, while those above 1.7 solar masses had a thicker mantle and squishy core.
“These results are very interesting because they give us a direct measure of the composition of the core of neutron stars,” says Rezzolla.
“Neutron stars look like chocolate pralines: light stars resemble chocolate with a hazelnut in between and soft chocolate, while heavy stars can be considered hard chocolate with a soft filling.”
This seems to be consistent with the nuclear pasta and quark soup interpretation of neutron star innards, and it also provides new information that will help model neutron stars for many types of future work.
This would also explain how, regardless of mass, all neutron stars have the same diameter of about 20 kilometers.
“Our extensive numerical analysis not only allows us to predict the radii and mass of neutron stars, but also to establish new limits on their distortion in binary systems, that is, how strongly they distort each other through their gravitational fields,” says the expert Astronomer Christian Ecker of Goethe University.
“This information will be very important to confirm the unknown parallels of the earth and future astronomical events and to detect gravitational waves from stars.”
Chocolate praline nuclear pasta quark sauce, anyone?
Research has been published in two papers in Astrophysical Journal Letters. They can be found here and here.