Join NOVA on a mind-bending hunt for a monster lurking at the heart of our Milky Way galaxy. Astronomers are closing in on one of the most destructive objects in the universe - a supermassive black hole - and it's hiding right in the center of our own galaxy. Eventually, it will blast jets of radiation millions of miles into space, incinerating everything in its neighborhood, including planet Earth. For a long time, black holes were dismissed as pure...