E. T. Byram

Far ultraviolet radiation in the night sky

Abstract Rocket measurements have shown that the night sky is aglow with a diffuse Lyman-α (1216 A) emission amounting to 10 −2 erg cm −2 sec −1 from the entire hemisphere. The glow was so bright that celestial sources of Lyman-α could not be detected through it. At wavelengths near 1300 A discrete celestial sources were observed, which contributed 10 −4 erg cm −2 sec −1 from the entire sky in the wavelength interval 1225–1350 A.

COSMIC X-RAY SOURCES, GALACTIC AND EXTRAGALACTIC

Instruments carried aboard an Aerobee rocket in April 1965 provided evidence for x-ray emission from the directions of the radio galaxies Cygnus A and M-87 and from the galactic supernova remnant Cassiopeia A. A survey of the Cygnus region revealed a marked decrease in the flux of x-rays from Cygnus XR-1, which was identified in June 1964 as the second brightest object in the first Naval Research Laboratory list of x-ray sources. The detection sensitivity was improved over previous surveys and several new sources were detected at lower flux levels.

X-rays from Sources 3C 273 and M 87

An x-ray survey of the Virgo region revealed signals from the directions of 3C 273 and M 87. Three other x-ray sources appear in the region scanned, but do not fit any known radio sources. The x-ray flux (1 to 10 angstroms) from the direction of 3C 273 is about 1000 times weaker than from the strongest x-ray source, Sco XR-1. If the source is located at the cosmological distance of 500 megaparsecs, the x-ray luminosity is 7.3 x 1045 ergs per second. The x-ray luminosity of M87 is 1.5 x 1043 ergs per second.

X-ray Survey of Centaurus A.

An x-ray survey of Centaurus A has given marginal evidence of its x-ray flux. If taken as an upper limit on inverse Compton x-rays generated by scattering interactions between relativistic electrons and cosmological background photons, the observation implies an upper limit of close to 3�K for the background radiation temperature.