Dark Sirens to Resolve the Hubble-Lemaître Tension

The planned sensitivity upgrades to the LIGO and Virgo facilities could uniquely identify host galaxies of dark sirens—compact binary coalescences without any electromagnetic counterparts—within a redshift of z = 0.1. This is aided by the higher-order spherical harmonic modes present in the gravitational-wave signal, which also improve distance estimation. In conjunction, sensitivity upgrades and higher modes will facilitate an accurate, independent measurement of the host galaxy's redshift in addition to the luminosity distance from the gravitational-wave observation to infer the Hubble–Lemaitre constant H 0 to better than a few percent in 5 yr. A possible Voyager upgrade or third-generation facilities would further solidify the role of dark sirens for precision cosmology in the future.