the observed x-ray background is thought to result from, at the "soft" end (below 0.3 kev), galactic x-ray emission (the "galactic" x-ray background), and, at the "hard" end (above 0.3kev), from a combination of many unresolved x-ray sources outside of the milky way (the "cosmic" x-ray background). the galactic x-ray background is produced largely by emission from hot gas in the local bubble within 100 parsecs of the sun. deep surveys with x-ray telescopes, such as the chandra x-ray observatory, have demonstrated that around 80% of the cosmic x-ray background is due to resolved extra-galactic x-ray sources, the bulk of which are unobscured ("type-1") and obscured ("type-2") active galactic nuclei (agn). ==references== *t shanks, i georgantopoulos, gc stewart, ka pounds, "the origin of the cosmic x-ray background", nature 353, 315 - 320 (26 september 1991);  *xavier barcons, the x-ray background, 1992 cambridge university press, 324 pages isbn 0-521-41651-5 * audio cain/gay (2009) astronomy cast x-ray astronomy ==see also== *x-ray astronomy
Astronomical_X-ray_sources Cosmic_background_radiation Observational_astronomy X-ray_astronomy