No. 79: Jan-Feb 1992
A persistent problem needling astronomers has been the diffuse X-ray background radiation; that is, that flux of X-rays that pervades the universe but which seems to come from no place in particular. Distant quasars are thought to contribute some of this diffuse X-ray flux but, even with recent quasar discoveries, there are just not enough of them to account for the X-rays observed. To make matters worse, quasar X- ray spectra do not match that of the X-ray background either, particularly at very short wavelengths.
Superimposed on the general X-ray background are discrete X-ray sources separated by extended blobs of X-ray emitting material. If these blobs are really clumps of clumps of quasars too close to be separated by our instruments, the Big Bang model is at risk, for it cannot account for large, organized assemblages of quasars. (Powell, Corey S.; "X-Ray Riddle," Scientific American, 264:26, March 1991.)