We may soon be able to tell if neutron stars are full of 'quark soup' just by listening to the hum they make when they’re near a black hole.
arXiv · March 17, 2026 · 2603.13637
The Takeaway
Neutron stars are so dense that their centers might dissolve into a liquid of quarks, but we have no way to look inside. This paper shows that if this transition occurs, it causes a specific 'stutter' in the gravitational waves emitted as the star orbits a black hole, allowing us to use gravity to see inside the densest objects in the universe.
From the abstract
Extreme Mass Ratio Inspirals (EMRIs) constitute a prime target for future space-based gravitational-wave observatories such as LISA. In this paper, we analytically investigate the long-term phase shift (dephasing) in the gravitational wave signal induced by a first-order quantum chromodynamics (QCD) phase transition within a neutron star orbiting a supermassive Kerr black hole. By modeling the transition from a hadronic phase to a quark core phase, we quantify the sudden change in the tidal defo