Unveiling the Secrets of Dark Matter's Impact on Stellar Explosions
Imagine a star, a massive powerhouse, with a core composed of oxygen, neon, and magnesium. As it reaches the end of its life, something extraordinary happens. This star, with a mass roughly 8 to 10 times that of our Sun, undergoes a unique type of explosion known as an Electron-Capture Supernova (ECSNe). The result? The birth of an incredibly dense neutron star.
But here's where it gets controversial... researchers from INFN-Pisa and the University of Pisa have delved into the potential influence of a mysterious entity called asymmetric dark matter (ADM) on this entire process. Their study, published in the Journal of High Energy Astrophysics, presents a groundbreaking model, the first of its kind, exploring how ADM might shape the collapse of the ECSN progenitor core and the subsequent formation of neutron stars.
"It was a eureka moment," shared Ignazio Bombaci, one of the study's co-authors. "When I read about supernova 2018zd, I realized the potential impact of fermionic dark matter on the ECSN process. It could lead to the formation of neutron stars with masses far below what we've observed so far."
The team's primary focus was on understanding how dark matter interacts with the ordinary matter in the star's core. They treated these two components as interpenetrating fluids, influenced solely by gravity.
"We used a general relativistic two-fluid formalism to describe the equilibrium of these two fluids under a shared gravitational field," explained Domenico Scordino, another co-author. "For the dark matter, we assumed it behaves like a cold, ideal, degenerate Fermi gas."
By solving stellar structural equations numerically, the team made predictions about how dark matter would alter the density profile of the ECSN progenitor's core and the mass threshold for its collapse.
"Our model shows that dark matter can make white-dwarf-like cores collapse at lower gravitational masses, leading to weaker explosions and the formation of unusually low-mass neutron stars," Scordino added.
This study introduces a new perspective, suggesting that very low-energy supernovae or unexpectedly light neutron stars could be signs of dark matter's presence within stars. It opens up a new avenue for dark matter research and our understanding of stellar explosions.
"Stellar explosions, traditionally studied from a nuclear and particle physics perspective, could also be natural laboratories for exploring dark matter's properties," said Vishal Parmar, the third co-author. "It gives us a unique astrophysical window into the mysteries of dark matter."
The team is now expanding their model, incorporating more realistic white dwarf compositions and exploring a wider range of dark matter properties. They aim to connect their theoretical work with multi-messenger astronomy, using observations from telescopes and gravitational-wave detectors to test dark matter's influence on stellar life cycles.
"We hope to provide new constraints on the neutron-star equation of state at intermediate densities by studying low-mass neutron stars originating from ECSNe," the authors concluded.
This research, a collaboration between Ignazio Bombaci, Domenico Scordino, and Vishal Parmar, highlights the intricate dance between dark matter and ordinary matter within stars, offering a new lens through which to explore one of physics' greatest mysteries.
