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Black Hole Observed by X-Ray Satellite
eldavojohn writes "Scientists at JAXA and NASA used the Japanese Suzaku satellite to collect data and observations at a distance nearer to a black hole than we've ever been. From the article: 'The observations include clocking the speed of a black hole's spin rate and measuring the angle at which matter pours into the void, as well as evidence for a wall of X-ray light pulled back and flattened by gravity. The findings rely on a special feature in the light emitted close to the black hole, called the "broad iron K line," once doubted by some scientists because of poor resolution in earlier observations, now unambiguously revealed as a true measure of a black hole's crushing gravitational force.' Suzaku also has been providing images and data of super novas and their activities. It's always nice to see national space agencies working together, it almost gives me hope that the world might one day be united in space exploration."
PhysicsPhil has a pretty good explanation. Here's another way of phrasing it.
Electrons, neutrons, and so on don't really exist as volumes, but rather as forces. Think about a balloon filled with air; it takes up space, but the only reason it does is because of the pressure of the air inside pushes out on the surface.
Now, if you squeeze the balloon, it'll shrink. The more you squeeze, the smaller it gets. If you could squeeze as hard as you please, you can continue to shrink the balloon smaller and smaller.
Particles are like that. Gravity is unique in that it's a force that can get infinitely strong, so it can overcome any other force, and squeeze everything together down to an arbitrarily small point.
Interestingly, from the perspective of a star collapsing into a black hole, it never actually quite makes it, as time slows down as gravity becomes stronger. It's like Zeno's paradox: If you try to go from point A to point B, crossing half the distance each time, do you ever get there? Intuitively, you'd think no, but if you take an infinite number of steps, yes.
In other words, black holes, from the perspective of the black hole, take forever to collapse down to a singularity. However, from our perspective outside the black hole, the singularity forms essentially instanteously, as our subjective time speeds up relative to the black hole's subjective time.
(As a side note, we don't have a theory of quantum gravity, so we don't actually know what the absolute center of a black hole is like, but we do understand the physics up to and past the event horizon, all the way to the singularity, all of which is just subject to general relativity. All the effects with astronomical significance occur outside the event horizon, as information that goes past there is effectively meaningless.)