Supernova explosions in the Universe

During the lifetime of our Milky Way galaxy, there have been something like 100 million supernova explosions, which have enriched the Galaxy with the oxygen we breathe, the iron in our cars, the calcium in our bones and the s ilicon in the rocks beneath our feet. These exploding stars also influence the birth of new stars and are the source of the energetic cosmic rays that irradiate us on the Earth. The prodigious amount of energy (similar to 10( 51), Or similar to 2.5 x 10(28) megatonnes of TNT equivalent) and momentum associated with each supernova may even have helped to shape galaxies as th ey formed in the early Universe. Supernovae are now being used to measure t he geometry of the Universe, and have recently been implicated in the decad es-old mystery of the origin of the gamma-ray bursts. Together with major c onceptual advances in our theoretical understanding of supernovae, these de velopments have made supernovae the centre of attention in astrophysics.