Astrophysicists Unlock the Universe: Breaking Down Barriers with Hubble’s Constant

A group of astrophysicists has presented the first measurement of the Hubble Constant using a combined analysis of weak gravitational lensing, galaxy clustering, and gravitational waves. This groundbreaking work employs a unique blend of data from the Dark Energy Survey (DES) and a gravitational wave catalog, including events detected by the LIGO-Virgo-KAGRA (LVK) detectors. Measuring the Hubble Constant-a key parameter determining the rate of expansion of the Universe-remains one of the most pressing challenges in modern cosmology. The problem is complicated by the fact that values obtained through traditional methods based on supernovae or the cosmic microwave background diverge from each other by several percent.

Recent advancements in gravitational wave astronomy have significantly enriched this analysis. With the emergence of next-generation detectors, the precision of such measurements is anticipated to improve drastically. Moreover, forthcoming data from the James Webb Space Telescope and the upcoming European Euclid mission are expected to provide unprecedented insights into cosmic expansion, further informing this research field.

The new methodology offers an independent approach, free from the classic “cosmic ladder” of distances. The method combines the analysis of correlations between distortions of galaxy shapes, their clustering, and the cross-links between these effects-with “standard sirens”: mergers of compact objects whose distances are determined directly from the shape of the gravitational signal. In the analysis, 141 “standard sirens” were included, along with the event GW170817-the only one to date with electromagnetic accompaniment. Additional data on the redshift of the host galaxy and orientation of the relativistic jet were used for this event.

As a result, a Hubble Constant value of H0 = 67.9 (+4.4/–4.3) km/s per Mpc was obtained with 6.4% precision. This is significantly better than using each of the individual methods alone: analysis of only “standard sirens” gives about 7% accuracy, and correlations of galaxy shapes and distortions around 17%. The data combination also improved DES’s constraints on the matter density of the universe by approximately 22%.

Authors emphasize the critical role of the angle of GW170817’s jet in the calculations: without it, the measurement accuracy worsens to nearly 10%. Estimates from gravitational waves and from the analysis of the large-scale structure fit well together-the deviation between their medians is only 0.78σ. The Hubble Constant remains one of the pivotal problems of modern cosmology due to discrepancies between measurements based on the early and late Universe. The achieved level of accuracy is comparable to other modern approaches and shows that “standard sirens” can become a crucial tool for studying cosmology as data accumulation continues.

Such analyses have significantly enhanced the assessment of the universe’s matter density by incorporating weak lensing. As the community prepares for the next big waves in observational data, the new methodologies pave the way for even more precise cosmological parameters, potentially resolving discrepancies that have puzzled scientists for years.