A study of 42 type Ia supernovae and a resulting measurement of ΩM and ΩΛ1This work was supported in part by the United States Department of Energy, contract numbers DE-AC03-76SF00098, CfPA, and NSF contract number AST-9120005.1

A search for cosmological supernovae has discovered over 75, most of which are type Ia supernovae. There is strong evidence from measurements of nearby type Ia supernovae that they can be considered as distance indicators or “standard candles” after correction for the width (time scale stretch parameter) of the individual light curves. Measurements and analysis are completed on 42 of these distant, z=0.18 to 0.83, supernovae. These supernovae, together with 18 “nearby”, z Ω M +Ω Λ =1 , we obtain ΩM= 0.28 +0.09 −0.08 ( statistical ) +0.05 −0.04 (systematic). The data are strongly inconsistent with a Λ=0 flat cosmology, the simplest inflationary universe model. An open, Λ=0 cosmology also does not fit the data well: the data strongly suggest that the cosmological constant is non-zero and positive, with a confidence of P(Λ>0)>99%.