The black hole GRO J1655-40, shown in this photograph, is estimated to be seven times the mass of our Sun. Its center is a one dimensional point of infinite density called a "singularity". Immediately around the core, out to a distance of about ten miles, is the "event horizon", filled with deadly X-ray light where temperatures rise to a million degrees or more, matter spins at nearly the speed of light and the magnetic force field is strong enough to re-arrange the atomic structure of all elements that fall within its gravitational pull. Nothing, not even light, can escape.