Chandra Resolves the Hard X-Ray Background

Explanation: It is everywhere but nobody knew why. In every direction at all times, the sky glows in X-rays . The X-ray background phenomenon was discovered over 35 years ago, soon after the first X-ray satellites were launched, and has since gone unexplained. Yesterday results were released using data from the recently launched Chandra X-Ray Observatory that appears to have resolved much of this mystery. 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? Early speculation, much of which predates these observations , holds that many of these sources are the active centers of distant galaxies , probably involving massive black holes . Still other sources may be of origins currently unknown.