Neutron stars are actually giant cosmic chocolates, say astrophysicists

An illustration of two giant chocolates in space.

An illustration showing the inner workings of heavier (left) and lighter (right) neutron stars, represented as chocolates.
Illustration: Peter Kiefer & Luciano Rezzolla

Astrophysicists who model the insides of neutron stars have found that the extremely compact objects have different internal structures, depending on their mass. She suggest think of the stars as different kinds of chocolate praline, a delicious treat – but that’s where the similarities end, at least as far as we know.

Neutron stars are the extraordinarily dense corpses of massive stars imploding; they are second only to black holes in their density. Neutron stars are so named because their gravitational pull causes their atoms electrons crash on the protons, creating an object composed almost entirely of neutrons.

The gravitational fields of neutron stars are super intense. If a human observer came close, they would be torn apart on an atomic level. Their are gravitational fields so strong that a “mountain” would stand on top of a neutron star less than a millimeter high.

The recent research team has built millions of models to try distinguish its internal workings stars, which are remarkably difficult to study and, as result, are more the domain of theory than of observation.

The researchers found that lighter neutron stars — those with masses about 1.7 times that of our Sun and less-should have soft mantles and stiff cores. More massive neutron stars have the opposite, according to the team’s findings published today in The Astrophysical Journal Letters.

Luciano Rezzolla, an astrophysicist at the Institute for Theoretical Physics who led the research, compared the structure of the stars to chocolate pralines.

“Light stars resemble chocolates with a hazelnut in the center surrounded by soft chocolate, while heavy stars can be considered more like chocolates where a hard layer contains a soft filling,” said Rezzolla in a Goethe University Frankfurt release.

The researchers modeled more than a million possible scenarios for the composition of neutron stars, based on expectations for the mass, pressure, volume and temperature of the star, as well as astronomical observations of the objects.

Modeling is a crucial means of interrogating neutron starsbecause there are only a few structures on Earth—CERN’s Large Hadron Collider and SLAC’s case in extreme circumstances instrument, for two – are capable of recreating such intense physics.

To determine the consistency of the stars, the researchers modeled how the speed of sound would travel through the objects. Sound waves are also used to understand the internal structure of planets InSight lander has done dauntless on Mars.

An illustration showing a possible layer configuration of a neutron star.

“What we have shown, by constructing millions of equations of state (from which the speed of sound can be calculated), is that maximally massive neutron stars have a lower speed of sound in the core region than in their outer layers,” said Christian Ecker. , an astrophysicist at Goethe University, in an email to Gizmodo.

“This points to some material change in their nuclei, such as a transition from baryonic to quark matter, for example,” Ecker added.

The researchers also found that all neutron stars are probably about 7.46 miles (12 km) regardless of their mass. That measurement is less than half that of a find 2020 that the typical neutron star is about 13.6 miles (22 kilometres) across. Despite its size, the average mass of a neutron star is round half a million Earths. There is close, and then there is stretched.

While the findings offer some insight into the diversity of neutron stars in terms of their consistency, the researchers did not examine the stars’ ingredients or how they fit together. (If you’ve come this far, neutron stars aren’t really made of chocolate.) Some suspect that neutron stars are neutrons all the way down; others believe that the centers are of the stars factories for exotic, as yet unidentified particles.

But for the most part, these super dense conundrums remain just that. Fortunately, observatories have been set up to collect more direct data. Fusions (ie violent collisions) between neutron stars and with black holes can reveal the masses of the objects involved, as well as the nature of the neutron star material.

Projects such as NICER, NANOGrav, the CHIME radio telescope, and the LIGO and Virgo science collaborations are all learning physicists about size and structure of neutron stars.

More observational data can be fed into models for better estimates of the stars’ aspects. Ecker added that very massive neutron stars (on the margin of two solar masses) would be particularly useful in better constraining expectations of the physical characteristics of these extreme objects.

With a bit of luck we will soon learn more about the exact ingredients of these giant cosmic pralines – and how their recipes may differ depending on their size.

More: Extremely massive neutron star may be the largest ever spotted

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