Gravitational waves refine cosmic expansion rate ⚡ экспресс
For the first time, researchers combined standard sirens (gravitational wave signals from merging neutron stars, which act like cosmic 'beacons' of known brightness) with weak gravitational lensing and the distribution of galaxies across the sky. This joint analysis yielded a Hubble constant of H₀ = 67.9 ± 4.3 km/s/Mpc (with 6.4% precision) and sharpened our estimate of matter density by 22%. Interestingly, without data on the jet from GW170817, the precision would have dropped to 9.9%. This hybrid approach blazes a trail toward resolving the Hubble tension as new data streams in.
Measuring the universe’s expansion is like timing a race when the track stretches. Neutron star mergers act as standard sirens: their gravitational waves ring out with a known “volume,” so fainter signals mean greater distance.
A new study paired the siren from merger GW170817 with a galaxy map tracing matter, including dark matter (invisible mass first detected by Vera Rubin). The result: the Hubble constant (named after Edwin Hubble) is 67.9 km/s per megaparsec—so a galaxy 3.26 million light-years away recedes at that speed—with just 6.4% uncertainty.
This value eases a cosmic dispute: the early universe’s afterglow suggests slower expansion, while nearby exploding stars point to faster. The new number falls between them, highlighting the strength of cross-checking methods. Remarkably, the spacetime ripples from GW170817 jiggled our detectors by less than a proton’s width, yet clocked the universe’s growth.
🎯 The term 'standard siren' echoes 'standard candle,' but while candles use light, sirens use gravitational waves—a clever twist on an old cosmic yardstick.