Feasibility of Measuring the Cosmological Constant Lambda and Mass Density Omega Using Type IA Supernovae

We explore the feasibility of resurrecting the apparent magnitude-redshift relation for a "standard candle" to measure the cosmological constant and mass density. We show that Type Ia supernovae, if measured with 0.15 mag uncertainty out to a redshift of z = 1, may provide a good standard candle or calibrated candle for this purpose. The recent discovery of probable Type Ia supernovae in the redshift range z = 0.3-0.5 (Perlmutter et al. 1994, 1995) indicates that the flux of optical photons from these events can be measured this accurately. The seven distant supernovae discovered to date do not by themselves distinguish among different cosmological models; however, the further discovery of about 50 Type Ia supernovae at redshifts in the range 0.5 ≤ z ≤ 1.0 could strongly constrain the allowed range of these parameters. We estimate that the follow-up photometry necessary for this measurement would be on the order of 20-70 hr of time on a 10 m class telescope at a site with good seeing.