Where is the nearest black hole and do we need to worry about it?
Well you don't need to worry about it, I know that. The nearest, really big one, is in the center of our galaxy. It's an amazing object, because we can watch stars which are in orbit around it and they whiz around every ten years or so. Telescopes are now good enough that we can watch this, and that allows us to weigh the black hole in the center. It's a few million times the mass of the sun and its still eating material, and you see flares coming out of it as materials drops in. But, its no threat to us. We're in a perfectly stable orbit, we're going to keep going around our galaxy, the sun goes around the center of the galaxy every 225 million years, and we're going to be doing that for a long while yet. There are probably some nearer, small black holes. Most small black holes form when stars bigger than eight times the mass of the sun reach the end of their lives. They explode, and their outer layers fly off and the center collapses to a black hole. They're out there, and they're perfectly happy, but they're no threat to anyone and the odds of one coming through the solar system is very low indeed.
