Revealing the Heart of Neutron Stars: The High Probability of Quark Matter Cores

Exploring the depths of massive neutron stars, scientists are edging closer to a monumental discovery: the existence of quark-matter cores. Recent findings suggest a staggering 80-90% likelihood that these dense astrophysical bodies harbor cores composed of deconfined quark matter. This breakthrough, detailed in a new article in Nature Communications by a team led by the University of Helsinki, hinges on extensive supercomputer simulations and Bayesian statistical inference.

Neutron stars, often likened to colossal atomic nuclei, encapsulate two solar masses within a 25 km diameter sphere. At these extreme densities, surpassing even individual protons and neutrons, the matter inside neutron stars becomes a frontier for particle and nuclear physics. The central question revolves around whether this immense pressure can transmute protons and neutrons into a new phase: cold quark matter. In this state, quarks and gluons, usually confined within particles, are liberated, moving almost freely.

Professor Aleksi Vuorinen from the University of Helsinki elucidates this concept, describing the potential transition of matter in neutron stars. However, this transition isn't without its challenges. A strong phase change could prompt a rapid destabilization, possibly leading the star to collapse into a black hole.

The international research collaboration, spanning Finland, Norway, Germany, and the USA, aims to eventually confirm or refute the existence of quark-matter cores. The crucial factor lies in understanding the strength of the phase transition from nuclear to quark matter, a discovery potentially unlocked by future gravitational-wave signals from binary neutron-star mergers.

Underpinning these findings are substantial supercomputer calculations, employing Bayesian inference to align theoretical predictions with observational data. These calculations help refine the properties of neutron-star matter, indicating a trend towards conformal behavior near the cores of massive neutron stars.

Dr. Joonas Nättilä, soon to be Associate Professor at the University of Helsinki, highlights this work as an interdisciplinary triumph. Meanwhile, PhD student Joonas Hirvonen acknowledges the critical role of high-performance computing, facilitated by the Finnish supercomputer center CSC.

This research not only unravels the mysteries of neutron stars but also propels our understanding of the universe's fundamental matter. Each new observation sharpens our insight into the extraordinary interiors of these celestial giants.