All black holes have several things in common: besides being black, and holes, they're all insatiably hungry, all the time. The more you feed them, the bigger and hungrier they get. One particular monster at the center of our galaxy is about to scarf down a big gas cloud, and for the first time, we're going to be watching it happen.
Sagittarius A* (stop looking for the footnote, it's actually known as "Sagittarius A*") is the black hole around which the entire Milky Way galaxy revolves. It's not just a massive black hole, it's SUPERmassive, with as much mass as about four billion suns all stuffed into an object smaller than the orbit of Uranus. Not something you want to go anywhere near.
One particularly unlucky gas cloud, though, is going to get entirely too near to Sagittarius A*. "It is not going to survive the experience," say astronomers, and luckily for us, we're close enough to actually watch the mayhem happen in detail, which is going to be quite a sight (for astronomers, at least). The light emitted by Sagittarius A* should increase by anywhere from a factor of 100 to a factor of 1,000 as half of the cloud gets devoured while the other half gets flung back out into space, which is what the above pic (a simulation) shows.
The fun should start happening in 2013, with the show ending in 2021 as what's left of the cloud escapes out into space, counting its lucky stars that it still exists. Mostly.
*I told you to stop looking for the footnote! But since you came all the way down here, you get to learn that the proper way to pronounce "Sagittarius A*" is "Sagittarius A-star."