Chandra Resolves the Hard X Ray Background . ... Credit Copyright: R. Mushotzky ( GSFC ) et al., Chandra , NASA Explanation: It is everywhere but nobody knew why. In every direction at all times, the sky glows in X-rays . ... The above photograph shows that about 80 percent of the apparently diffuse hard X-ray background can be resolved into very many very faint sources. The new question is now what are these sources? ... NASA Official: Jay Norris. ... A service of: LHEA at NASA / GSFC . ...