Supernovas

These cataclysms happen every few seconds in some remote galaxy, blazing as bright as hundreds of billions of stars and creating a fireball that expands for months. We're lucky they rarrely strike close to home. The last one in our galaxy exploded in 1604, rivaling Jupiter's brightness in the night sky. A nearby supernova - within a few light years - would bathe the earth in lethal radiation. (National Geographic March 2007)