Recent observations show that the Universe is currently expanding about 9% faster than expected based on the available information from the early Universe. Since predictions based on early-Universe observations are formulated under the assumption of cosmological models, the reported mismatch suggests a possible cosmological crisis.
A distance ladder composed of type-I Cepheids and type-Ia supernovae currently provides the most precise late-Universe measurement of the expansion rate, Hubble's constant (H0). As increasingly precise and accurate H0 measurements are required to understand or resolve the late vs. early Universe discord, due diligence requires greater detail in the determination of intervening systematics, especially for the type-I Cepheids that provide the absolute base calibration. At the same time, precision observations increasingly showcase our limitations in the understanding of these crucial stars and provide new insights into basic stellar astrophysical processes.
Starting from a brief overview of the discord in Hubble's constant, I will present recent improvements in the calibration of and upcoming opportunities for the distance ladder. In turn, I will discuss the latest new insights into Cepheid stars in the context of achieving a sound theoretical basis for distance ladder calibration. Finally, I will give some examples of recent research targeting previously unknown or confused H0 systematics that become increasingly important as the cosmological tension rises.
Meeting ID: 947 6931 1414
Excellence Cluster ORIGINS