X-rays are generated when electrically charged particles are made to decelerate strongly. In practice this means the sudden stopping o f high-speed electrons when they crash into the tungsten targets in X-rays tubes. They are also produced when the tracks o f energetic electrons or ions in the outer reaches o f stars bend under the influence o f very strong m agnetic fields. A third source is the high-energy photons em itted when the inner (but still very m uch extranuclear) electrons in atoms are first excited and then returned to their ground states. It is this third source o f X-rays that accounts for most o f the low-energy X-ray segm ent that overlaps with UV radiation in the electromagnetic spectrum. The com ponents o f a typical X-ray tube are shown in the diagram below.