Distribution and Variability of Cosmic X-Ray Sources

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Science  21 Apr 1967:
Vol. 156, Issue 3773, pp. 374-378
DOI: 10.1126/science.156.3773.374


At least 30 discrete cosmic x-ray sources have been detected thus far. The distribution is concentrated toward the galactic plane, and most of the sources are believed to lie within 2 kiloparsecs of the sun. It is estimated that the average luminosity of the observed sources is about 5 x 1036 ergs per second and that the entire galaxy contains about 1250 such sources. Comparisons of fluxes observed over the course of the past 2 years reveal that many sources are highly variable.