In every direction at all times, the sky glows in X-rays . 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. 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.
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