The rise of neutron stars: observing them will solve key puzzles for nuclear physicists

Scientists' observations of the growth of neutron stars

The nuclear physicists hope to unravel the secrets of key puzzles by watching the neutron stars grow. The atomic nuclei of protons and neutrons are capable of separating energy and momentum. But how they share energy, being held in a bound state inside the nucleus, is one of the main mysteries. The scientists from the Lawrence Livermore National Laboratory and Washington University in St. Louis were able to address that issue in their latest study.

They used the results of experiments on nuclear scattering and introduced strict restrictions on how neutrons and protons can be located in the nucleus. Professor Cole Pruitt believes that several cornerstone nuclei in a tiny fraction of protons and neutrons have a huge share of the total energy.

It keeps protons and neutrons in nuclei. And the force turned out to be 50% more than expected by standard calculations. In addition, the scientists made new predictions for the "neutron skin". It is the name of the area where additional neutrons accumulate.

Surprisingly, these predictions are related to how neutron stars grow and what elements can be synthesized when neutron stars merge. According to Pruitt, the results of the new study demonstrate the ability of asymmetry, charge and shell effects to determine a disproportionate dose of total binding energy to the deepest nucleons.

The energy of nuclear asymmetry changes with density. How that happens is an important knowledge for compiling the equation of state of the neutron that determines the structure of the neutron star. Measuring it is not easy. In 2010, an experiment with the code name "Lead radius" was carried out.

It was the first to use a method independent of the neutron shell measurement model for lead-208, but the measurement received a very large error. The second, more accurate experiment was carried out in 2019, and the results have not yet been released.