Cosmological parameters from type Ia supernovae

Observational cosmology is currently experiencing a revolution. Recent meas urements of mangitudes vs redshift of very distant type Ia supernovae indic ate that the expansion velocity of the universe is increasing. This acceler ation requires the existence of an energy form that overcomes the gravitati onal self-attraction of matter, such as the vacuum energy density associate d with the cosmological constant (Lambda). This papers describes how cosmological parameters can be extracted from the Supernova Cosmology Project data and what can be expected from future meas urements of Type Ia supernovae.