Supernova Cosmology Project

The Supernova Cosmology Project (SCP) was a project begun in the 1990s to determine the history of the Hubble parameter, which determined that the expansion of the universe has accelerated. Previous general thought had been that the universe's expansion would be decelerating, due to the sum of the universe's gravity, and the intent of this project was to determine the rate of that deceleration, with special interest regarding whether this deceleration is such that expansion will eventually cease and contraction begin. The project's strategy was to collect data on the frequency of Type Ia supernovae against redshift, producing a kind of Hubble diagram; conceptually, any bending in the diagram's slope would reveal past changes in the pattern of expansion. The supernova search was carried out with the Blanco 4m telescope, with follow-up spectroscopy and photometry on other telescopes, to record light curves. The project's determined that the expansion has accelerated rather than decelerated was unexpected, but was confirmed by another independent such effort carried out at the same time by the High-z Supernova Search Team. This conclusion gave rise to the term dark energy, for whatever is making that happen.