Number 51 (Story #1), October 10, 1991 by Phillip F. Schewe and Ben Stein THE COSMIC X-RAY BACKGROUND , first detected in 1971, consists perhaps largely of radiation from discrete quasars. British scientists analyzing data from the German x-ray satellite Rosat looked at a very select far-distant field of the sky and found 39 x-ray sources; follow-up studies with an optical telescope showed that 24 of these were quasars. The scientists conclude that at least 30% (but perhaps almost all) of the x-ray background in the 1-keV energy range arise from quasars. (Nature, 26 Sept. 1991.)