Two Sources of Cosmic X-rays in Scorpius and Sagittarius

WE have observed two separate and intense sources of cosmic X-rays in the region of the constellations Scorpius and Sagittarius during a rocket experiment launched on August 28, 1964. This is the same general region of the sky from which non-solar cosmic X-rays were first detected in June 1962 by Giacconi et al.1. In that earlier work a Geiger tube detector of large area and wide angular response was mounted, looking out of the side of a spinning rocket. A strong maximum in the counting rate was observed when the detector pointed in a southerly direction. A detailed discussion of the results led to the conclusion that the X-rays were of non-terrestrial origin, and that they emanated from a source close to, but apparently not coincident with, the galactic centre. These conclusions were confirmed in two later rocket flights, also employing wide-angle detectors2. In April 1963 Bowyer et al. conducted a rocket experiment using a detector with a field of view 10° wide at half maximum intensity3. At the time of that flight the galactic centre was below the horizon. They gave a location for the source in Scorpius at about 16 h 15 min right ascension and − 15° declination and stated that its angular diameter is less than 5°.