As everything in existence, stars die as well. And many of them have reserved a kind of death brilliant and explosive: We call it a Supernova.
When a dying star hasn´t "fuel" enough to keep shining, it´s own gravity pull it inside and collapse, exploding with an incredible energy with no comparation. This enormous burst not only would end with all the planets of the star, but it would wipe out all the surronding star systems too.
What happens the if a nearby star to our solar system becomes a Supernova? How would it affect us? Well it´s assumed that if it occurs in a star located within 100 light years, almost all life in our planet would dommed. If not all species were killed in the first wave, the loss of the ozone layer, will cause a fatal damage to the rest of life.
Luckily the only nearby candidate to supernova, lies more than 400 light years and it´s our old friend Betelgeus, in the Orion constellation.
So far, most of the supernovae we´ve observed, were in others galaxies and thus their light reaches us but it doesn´t mean any danger to us at all.
Last weekend I could picture that one in M74 and though it was very faint, I could mesure its magnitude that was around 17. I really woudn´t want to be its neighbour.