A Supernova Every 50 Years - Universe Today
A team of European astronomers has calculated the rate that supernovas are exploding in the Milky Way: approximately one goes off every 50 years. They came to this calculation by measuring the amount of gamma rays coming from radioactive aluminum at the centre of the Milky Way. They were able to estimate that there's a total of approximately three solar masses of radioactive aluminum in the galaxy - produced by supernova exploding every 50 years or so.