April 17, 2024

Further Confirmation of Quark-Matter Cores in Massive Neutron Stars

Scientists from the University of Helsinki have provided compelling evidence for the existence of quark-matter cores in massive neutron stars. Neutron stars are incredibly dense objects with masses equivalent to two suns packed into a sphere just 25 kilometers in diameter. These astrophysical marvels can be thought of as giant atomic nuclei, with their cores compressed to densities that exceed those of individual protons and neutrons. The enormous pressure at the center of neutron stars raises the question of whether protons and neutrons can be compressed into a new form of matter called cold quark matter, in which individual protons and neutrons cease to exist and constituent quarks and gluons become liberated.

The team, led by Professor Aleksi Vuorinen, calculated the likelihood of quark-matter cores based on current astrophysical observations and found a quantitative estimate ranging from 80% to 90%. This suggests that quark matter is almost inevitable in the most massive neutron stars. However, there is a small chance that all neutron stars consist solely of nuclear matter, which would require a strong first-order phase transition from nuclear to quark matter. This rapid change in the properties of neutron star matter could potentially destabilize the star, causing it to collapse into a black hole.

To determine whether quark-matter cores exist, scientists need to assess the strength of the phase transition from nuclear to quark matter. Detection of a gravitational-wave signal from the final stages of a binary neutron star merger could provide the necessary information. The international collaboration, consisting of researchers from Finland, Norway, Germany, and the US, used Bayesian inference in their calculations. This statistical method allowed them to compare their theoretical predictions with observational data and derive new constraints for the properties of neutron star matter.

Dr. Joonas Nättilä, one of the lead authors of the study, emphasized the interdisciplinary nature of the research, requiring expertise from astrophysics, particle and nuclear physics, and computer science. The use of high-performance computing and millions of CPU hours was vital to compare theoretical predictions with observations and determine the likelihood of quark-matter cores. The team expressed gratitude to the Finnish supercomputer center CSC for providing necessary resources.

The results of this study offer exciting insights into the nature of neutron stars and the existence of quark-matter cores. As each new observation of neutron stars provides more precise data, scientists can deduce the properties of neutron-star matter with increasing accuracy. The confirmation or elimination of quark-matter cores will further our understanding of the fundamental physics that governs these cosmic objects.

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1. Source: Coherent Market Insights, Public sources, Desk research
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