Analysis of this data, which resolves about 60% of the 5-10 keV X-ray background, tends to indicate that many of these sources are probably obscured Seyfert galaxies and quasars.

Viewed in visible light, the sky appears as a dark expanse, adorned with the twinkling lights of faraway stars. But with an X-ray telescope, the sky seems uniformly bright, bathed in a diffuse ...