A non-thermal source of radiation emitted by charged particles being accelerated in magnetic fields and moving at near the speed of light. When the speed of a charged particle is close to the speed of light, it emits much
stronger radiation, known as synchrotron radiation. An example of this are quasars, which emit synchrotron
radiation in addition to visible light and X-rays.
When electrons (also a charged particle) are decelerated in a magnetic field, they also give off radiation known as synchrotron radiation -- when
decelerating, it is sometimes called braking radiation or "Bremsstrahlung" radiation.