The James Webb Space Telescope (JWST) has confirmed previous findings from the Hubble Space Telescope (HST) regarding the Hubble Constant (H0), a critical parameter in cosmology that determines the universe's expansion rate. The recent study, led by Adam G. Riess of Johns Hopkins University, validates HST's measurements using JWST to refine the cepheid/supernova distance ladder.
The Hubble Constant defines the relationship between the velocity at which distant galaxies recede from Earth and their distances, measured in kilometers per second per megaparsec. Accurate determination of H0 is essential for understanding the universe's age, size, and ultimate fate.
In this study, the researchers utilized JWST to explore earlier findings regarding the distances of cepheid variable stars and Type 1a supernovae, which serve as 'standard candles' for measuring cosmic distances. By comparing their apparent brightness to intrinsic luminosity, the team aimed to provide a more precise value for H0.
Previous attempts to measure H0 have led to a phenomenon known as 'Hubble tension,' where different methods yield varying results. The latest findings from JWST suggest H0 is 72.6 ± 2.0 km/s/Mpc, closely aligning with HST's value of 72.8 km/s/Mpc. Continued observations from JWST are anticipated to further refine these measurements.
To achieve accuracy, a large sample of cepheids and supernovae must be analyzed. The team also investigated alternative methods, such as measuring the luminosity of the brightest red giant branch stars and certain carbon-rich stars, which can also act as standard candles.
As JWST continues to gather data, the collaboration between these two observatories is expected to enhance our understanding of the universe's expansion, moving toward a consensus on the Hubble Constant.