Rate of explosion

The rates bring fundamental information to us on the populations relationships and the physical processes which govern the explosion. They are expressed either in a number of supernovæ per century and by $10^{10 } \rm \, M_\odot$. The supernovæ are more frequent in the spirals than in the elliptic ones and the irregular ones. When they explode in the spirals, these explosions take place close to the spiral arms, zones of star formation. It should be noted that this goes against the assumption of old population for the progéniteurs. This could indicate that the stars progéniteurs are of average lifespan (0.5 billion years).

These measurements of rate inform not only about the nature of the progéniteurs but also about the mechanisms of star formation and about the evolution of the chemical composition of the galaxies by enrichment in intermediate elements of mass.