Can gravitational waves reveal what neutron star cores are made of?

When massive stars collapse into neutron stars and spin fast, they develop a specific instability that creates spiral-shaped density waves. Using simulations with different models of ultra-dense matter, researchers found this instability always occurs but generates gravitational waves at frequencies that depend on how stiff or compact the neutron star becomes. This suggests gravitational wave detectors like LIGO could decode the neutron star's equation of state—its fundamental material properties—directly from the signal frequency.