Ionospheres of dead stars and living galaxies

Three possible mechanisms that could give rise to the x-rays generated in cosmic systems; hot gas, the universe Compton effect and synchrotron radiation, are described. It is clear that the radiating region in each case is a plasma, an ionosphere, and the observation shows that the regions are associated with five identifiable broad classes of source with perhaps distant space without distinguishable features as a sixth sense. These five classes of source are: (a) the region around a star which has died in a supernova explosion. Casseopeia-A is a prototype; (b) the region around a fast pulsar; (c) the region around a dead star; (d) active galaxies and quasars; (e) the region between galaxies. These sources of radiation are discussed. (U.K.)