Black hole. Computer illustration of a black hole pulling material from its companion star. A black hole is a region in space where the pull of gravity exceeds the velocity of light. Matter falling on a black hole forms an accretion disc (as seen here) as the hole is spinning rapidly. The two white jets are believed to be high-energy particles ejected at 90 degrees to the plane of the disc, forced away from the hole by radiation pressure. The centre of the disc appears white as the matter is at great speed, and thus high energy, and is thought to emit X-rays. Several candidates have been found fitting a black hole's profile, but none have been proved absolutely yet.