Nearby Supernova explosions and radiation effects on the Earth's environment

The explosion of a star as a Supernova (SN) may occur in our Milky Way once every 70 years. Since the great explosion energy can also be released as high-energy radiation, we investigated the effects on the Earth's environment. To this aim we identified 217 stars lying within 200 pc from the Sun that are possible candidates for a future explosion. Starting from the models available in the literature for the first stages of the SN explosion, we simulated the spectrum of radiation emitted after the explosion by means of a black body law with a maximum temperature of similar to800 000 K, decreasing with time. The huge quantity of X-ray and UV radiation expected from this explosion were calculated. According to our calculations, the effects of the above radiation are stronger in the first two hours after the explosion. The Earth's ionosphere may increase its thickness lowering itself to 64 km from the ground, with recombination effects and re-emission of UV radiation toward the ground. Biological effects are briefly discussed.