NOVA: Death Star
They are so bright, they are a billion billion times more luminous than the sun. They are so distant, their light takes billions of years just to reach Earth. These amazingly violent explosions-or death stars-may even have the power to eradicate life in an entire galaxy. See how these celestial phenomena can teach us about the dawn of the universe. And hear a controversial theory of how a gamma ray burst somewhere in our own galaxy could destroy life on Earth.