Gamma rays may have devastated life on Earth 24 September 03 New Scientist A devastating burst of gamma rays may have caused one of Earth's worst mass extinctions, 443 million years ago.  A team of astrophysicists and palaeontologists says the pattern of trilobite extinctions at that time resembles the expected effects of a nearby gamma-ray burst (GRB). 
We have evidence that supernovae occurred near the earth in the past.