Peter M. Garnavich (CfA)
Reference URL: http://cfa-www.harvard.edu/cfa/oir/Research/supernova.html
The discovery of a correlation between the light curve shape and intrinsic brightness has made Type Ia supernovae exceptionally accurate distance indicators out to cosmologically interesting redshifts. Ground-based searches and follow-up as well as Hubble Space Telescope observations of Type Ia supernovae have produced a significant number of objects with redshifts between 0.3 and 1.0. The distant SNe, when combined with a local sample analyzed in the same way, provide reliable constraints on the deceleration and age of the Universe. Early this year an analysis of a handful of Type Ia events indicated that the deceleration was too small for gravitating matter alone to make a flat Universe. A larger sample of supernovae gives the surprising result that the Universe is accelerating, implying the existence of a cosmological constant or some other exotic form of energy.
The success of this research has depended on the development of algorithms and software to register, scale and subtract CCD images taken weeks apart and to search for variable objects. A good fraction of the point-sources identified are asteroids, variable stars or AGN, so spectra are needed to confirm the identification as a Type Ia supernova and obtain a redshift. The best candidates are followed photometrically to construct light curves . The steps to transform the observed light curves into cosmologically interesting results will also be described.