Carnegie Mellon University

Physics Colloquium

Tension in  the Hubble Constant

I will present new results from the Carnegie-Chicago Hubble Program (CCHP), a decade-long project to independently measure a value of the Hubble constant to very high precision and accuracy. This program uses data from Hubble Space Telescope; the  Spitzer mid-infrared satellite; and ground-based telescopes  including dedicated robotic follow-up telescopes. High precision and accuracy distances are measured using  Cepheids, RR Lyrae variables, tip of the red giant branch (TRGB) stars, and Type Ia supernovae. By building an entirely new data set from the ground up,  we have calibrated and applied two independent methods to the derivation of Ho, and address the issue of the current tension in Ho.