Bueno vos queres todo tambien
Lo mio era una estimacion.

Vi esto en wikipídia que me sorprendio:

Citar Mensaje original enviado por http://en.wikipedia.org/wiki/Supernova
A near-Earth supernova is an explosion resulting from the death of a star that occurs close enough to the Earth (roughly fewer than 100 light-years away) to have noticeable effects on its biosphere. Gamma rays are responsible for most of the adverse effects a supernova can have on a living terrestrial planet. The gamma ray burst from a nearby supernova explosion has been proposed as the cause of the end Ordovician extinction, which resulted in the death of nearly 60% of the oceanic life on Earth.

Recent estimates predict that a Type II supernova would have to be closer than eight parsecs (26 light-years) to destroy half of the Earth's ozone layer.