Number 144 (Story #2), September 20, 1993 by Phillip F. Schewe and Ben Stein THE HIGH-ENERGY X-RAY BACKGROUND , the diffuse x-ray glow spread across the sky, comes mostly from active galactic nuclei (AGN). Julian Krolick of Johns Hopkins and Andrzej Zdziarski and Piotr Zycki of the Copernicus Astronomical Center in Warsaw have reinterpreted data from the Japanese satellite Ginga, the U.S. Gamma Ray Observatory, and the Russian satellite GRANAT and conclude (in the 10 Sep. Astrophysical Journal Letters) that earlier analyses were wrong and that the bulk of background x radiation at energies of tens of keV do come from the cores of powerful galaxies. The lower-energy portion of the x-ray background had already been attributed to AGN's. (Science News, 18 Sept. 1993.)