Abstract

Cosmology is at an interesting juncture. In the past century, astronomers obtained the first complete census of the mass and energy in the universe. We learned that the universe is composed of about one third matter, while two thirds is in a new mysterious form that astronomers refer to as dark energy. This dark energy is causing the universe to accelerate in its expansion. I will discuss measurements of cosmological parameters, with particular focus on measurements of the dark energy and the Hubble constant, the current expansion rate of the universe. I will give an update on the status of the Carnegie Supernova Program, a long-term project to follow up type I supernovae with photometry at many wavelengths and spectroscopy out to redshifts of 0.7. Finally, I will discuss a new project to improve the accuracy of the Hubble constant based on new mid-infrared measurements of distances using the Spitzer satellite.