Can gravitational waves reveal what's ringing inside neutron stars?

As two neutron stars spiral together, rising gravitational-wave frequencies ring the stars like bells — and those vibrations leave faint imprints in the signal. Simulating a year of Einstein Telescope observations, the researchers found the detector could catch these resonances in the loudest events and measure phase shifts of just 0.03 radians. Miss them, and you miscalculate the stars' internal structure — but detect them, and you have a direct seismological probe of matter at nuclear densities.