Resolving a 30-year-old mystery, astronomers say they have identified the source of the gamma-ray background, the faint high-energy radiation permeating the cosmos. Caleb A. Scharf and Reshmi Mukherjee of Columbia University compared known positions of 2,469 galaxy clusters with data collected for 9 years by NASA's Compton Gamma Ray Observatory. Gamma rays are concentrated in regions surrounding the most massive clusters, the scientists report in an upcoming Astrophysical Journal.
This statistical result supports a theory proposed recently by Avi Loeb of Harvard University and Eli Waxman of the Weizmann Institute in Rehovot, Israel.
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