theory.toys – Standard Sirens

True H₀: 70 km/s/Mpc

Number of Detections: 10

Measurement Uncertainty: 10🔑 Unlock

Inferred H₀ from GW Data

About Standard Sirens

Gravitational wave (GW) detections from binary mergers provide "standard sirens" - direct distance measurements from the GW strain amplitude without needing a cosmic distance ladder.

The GW strain amplitude h ~ M_chirp/D_L, where M_chirp is the chirp mass (determined from the frequency evolution) and D_L is the luminosity distance. Combined with redshift z from an EM counterpart (like GW170817's kilonova), this directly measures H₀.

At low redshift: H₀ ≈ cz/D_L. With many detections, statistical uncertainties shrink as 1/√N, providing an independent probe of the Hubble tension.

Reference Values

Planck CMB: H₀ = 67.4 ± 0.5 km/s/Mpc
SH0ES (Cepheids): H₀ = 73.0 ± 1.0 km/s/Mpc
GW170817: H₀ = 70 ± 12 km/s/Mpc
Future: 50+ events → σ(H₀) ~ 2%