Host: Dr. Julia Bodensteiner
Measuring the Hubble constant is difficult. In the local universe, the H0 determination is hampered by two impediments: the local disturbance of the expansion field and the rarity of luminous distance indicators with a reliable absolute calibration. This led to the principle of the distance ladder, where distance indicators are calibrated at lower distances and then applied as calibrators of another distance indicator at larger distances. Several methods have been used in the past years to measure the local expansion rate, but they have not converged. In addition, some of the local H0 determinations disagree with the derived expansion rate from the Lambda CDM model as calibrated by the cosmic microwave background resulting in the ‘Hubble tension’. Recently, an improved version of the Expanding Photosphere Method (EPM) for type II supernovae has been devised and it enables us to derive H0 bypassing the distance ladder. This promises to become an independent and unique probe of the cosmic expansion rate.