This illustration shows the absorption of X-rays from the quasar Mkn 421 by two intergalactic clouds of diffuse hot gas, and a portion of the Chandra X-ray spectrum of the quasar. The spectrum provides evidence that three separate clouds of hot gas are filtering out, or absorbing X-rays from Mkn 421. Image Credit: Spectrum: NASA/SAO/CXC/F.Nicastro et al.; Illustration: CXC/M.Weiss
