9 months ago
Last edited at 9:00PM on 3/29/2013
Think of a a black hole as the vortex or whirlpool that forms when your bath water is running down the plug-hole. The water that defines the shape of that vortex is matter, but the actual whirlpool is nothing but air. In space, the matter that defines the shape and position of the black hole is solid enough, but the hole is just that - a hole - a whirlpool that swallows all nearby matter, a planet for breakfast, a star or two for lunch and anything within a million miles is on the menu.
A black hole is a region of space-time from which gravity prevents anything, including light, from escaping. The theory of general relativity predicts that a sufficiently compact mass will deform space-time to form a black hole. There's a lot more information on this site http://en.wikipedia.org/wiki/Black_hole
9 months ago
Last edited at 5:18PM on 3/29/2013
Black holes are from stars that were once larger than our own sun. As these stars came to the point in their life where there were no more atoms to fuse together that would generate enough heat to create a balance of pressures, gravity prevailed and the star collapsed in on itself. Gravity became so intense that not even light can escape. Interestingly enough gravity has no problem however in expressing how much matter lies beneath this horizon. Light is held back, but gravity is not, and black holes can grow too, by eating other stars and whatever other materials that get pulled into it's vicinity. My guess is that black holes are still made up of some sort of matter, but it's extreme environment makes it unknown as to what type or form this matter now resides as.