Fear Not A Supernova 2012

Supernova 1987A was the closest exploding star seen in modern times. It occurred in the Large Magellanic Cloud, a small galaxy that orbits our own Milky Way. Given the incredible amounts of energy in a supernova explosion, as much as the sun creates during its entire lifetime, another erroneous doomsday theory is that such an explosion could happen in 2012 and harm life on Earth. However, given the vastness of space and the long times between supernovae, astronomers can say with certainty that there is no threatening star close enough to hurt Earth. Astronomers estimate that, on average, about one or two supernovae explode each century in our galaxy. But for Earth’s ozone layer to experience damage from a supernova, the blast must  occur less than 50 light-years away.

All of the nearby stars capable of going supernova are much farther than this. Another explosive event, called a gamma-ray burst (GRB), is often associated with supernovae. A gamma-ray burst could affect Earth in much the same way as a supernova, but only if its jet is directly pointed our way. Astronomers estimate that a gamma-ray burst could affect Earth from up to 10,000 light-years away with each separated by about 15 million years, on average. So far, the closest burst on record, known as GRB 031203, was 1.3 billion light-years away.
source:www.nasa.gov