I saw something like this in an episode of the Universe..they said it happnt before and caused a major extinction event.
I wouldnt be to scared though because they are very rare.
cheers
A STAR is primed to explode in a blast that could wipe out the Earth, according to American astronomers. A new study shows the star, called T Pyxidis, is much closer than previously thought at 3,260 light-years away - a short hop in galactic terms.
It is set to self-destruct in an explosion called a supernova with the force of 20 billion billion billion megatons of TNT. The blast from the thermonuclear explosion could strip away the Earth's ozone layer that keeps out deadly space radiation, scientists said.
The doomsday scenario was described today by astronomers from Villanova University in Philadelphia. They said the International Ultraviolet Explorer satellite has shown them that T Pyxidis is really two stars, one called a white dwarf that is sucking in gas and steadily growing. When it reaches a critical mass it will blow itself to pieces