Exotic quark matter nuclei are likely to exist in neutron stars

At the end of the star’s life, nuclear fusion stops, and the resulting pressure is no longer sufficient to counteract the force of gravity. This collapse can lead to the formation of neutron stars, which are composed of the densest matter in the universe. However, the formation of neutron stars has been the subject of much controversy.

Based on reviews Neutron stars And quantum chromodynamics theory, a research team led by Professor Fan Yizhong of the Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences (CAS) found that a strange quark matter nucleus most likely exists in a massive cluster. neutron stars. Observing this strange core provides a unique opportunity to explore the equation of state (EOS) of dense matter, in particular the transition from hadronic matter to quark matter.

The study has been published in Science Bulletin On April 11th.

The researchers analyzed data about the neutron star’s mass and radius, gravitational waves of binary neutron star mergers, and theoretical limitations from quantum chromodynamics calculations. Taking advantage of the shared information and their newly developed statistical method, the researchers studied the structure of EOS dense matter in detail.

They found that EOS’ supersonic peak structure most commonly appeared in the back part, located at a density lower than that of the center of the largest massive neutron star. This non-monotonic behavior indicates that the state deviates from pure hadronic matter.

In addition, they found support for the existence of exotic cores in neutron stars that are 0.98 times heavier than the most massive, based on a back part that satisfies both experimental and theoretical limitations.

Quantitative analysis revealed that the state at the center of the most massive neutron star is a softer state than typical hadronic matter (even with hyperons), and that a large (>1 kilometer) exotic core is plausible.