Supernova Cosmology: Legacy and Future

The discovery of dark energy by the first generation of high-redshift supernova surveys has generated enormous interest beyond cosmology and has dramatic implications for fundamental physics. Distance measurements using supernova explosions are the most direct probes of the expansion history of the universe, making them extremely useful tools with which to study the cosmic fabric and the properties of gravity at the largest scales. The past decade has seen confirmation of the original results. Type Ia supernovae are among the leading techniques to obtain high-precision measurements of the dark energy equation-of-state parameter and, in the near future, its time dependence. The success of these efforts depends on our ability to understand a large number of effects, mostly of an astrophysical nature, that influence the observed flux at Earth. The frontier now lies in understanding whether the observed phenomenon is due to vacuum energy, despite its unnatural density, or some exotic new physics. Future surveys will address the systematic effects with improved calibration procedures and will provide thousands of supernovae for detailed studies.