Stellar rotation can have a very rapid rate of rotation; on the order of a hundred rotations per second. Pulsars are rotating neutron stars that have a magnetic field. A narrow beam of electromagnetic radiation is emitted from the poles of rotating pulsars. If the beam sweeps past the direction of the Solar System then the pulsar will produce a periodic pulse that can be detected from the Earth. The energy radiated by the magnetic field gradually slows down the rotation rate, so that older pulsars can require as long as several seconds between each pulse. A black hole is an object
Beam spoiler Beam spoiler A beam spoiler is a piece of material, placed into the path of the photon beam in radiotherapy. The purpose of the spoiler is to reduce the depth of the maximum radiation dosage. The beam spoiler is composed of a sheet of material which has a low atomic number, typically lucite, the thickness of which is varied according to the beam energy and the distance by which the radiation dose must be shifted. As the primary photon beam passes through the plate, secondary electrons are generated. The beam exiting the spoiler is a combination of the spoiler-attenuated photons