Supernovae and cosmology

These lecture notes intend to form a short pedagogical introduction to the use of typical type Ia-Supernovae (hereafter SNIa) as standard candles to d etermine the energy density of the universe. Problems of principle for taki ng SNIa as cosmological probes are painted out, and new attempts at solving them are indicated including the empirical width-luminosity relation (WLR) and its possible explanations. Finally, the observations of SNIa at high r edshift carried out by two major teams are briefly reviewed and their inter pretation as evidence for an accelerating universe is also rapidly discusse d (C) 2001 Elsevier Science B.V. All rights reserved.