Chandra X-ray Image of Mkn 421
This Chandra X-ray image of Mkn 421, a quasar located 400 million light years from Earth, was taken with the High Resolution Camera (HRC) on July 1, 2003.
Scale: Image is 0.5 arcmin per side
(Credit: NASA/SAO/CXC/F.Nicastro et al.)

Chandra X-ray Spectrum of Mkn 421
This image shows a portion of the X-ray spectrum of the quasar Mkn 421, taken with Chandra's Low-Energy Transmission Grating (LETG). The dips in the spectrum are produced when X-rays of a specific wavelength are absorbed by ions of oxygen in hot gas clouds located at various distances from Earth. The orange dips are caused by relatively nearby clouds; the green and red dips are from clouds at distances of 150 million and 370 million light years, respectively. These distant clouds are likely part of a predicted diffuse web-like system of hot gas clouds - the cosmic web - from which galaxies and clusters of galaxies are thought to have formed. This discovery is strong evidence that atoms and ions known to be present shortly after the Big Bang, but missing in inventories of matter in the present era, are hiding in the hard-to-see cosmic web.
(Credit: NASA/SAO/CXC/F.Nicastro et al.)

Illustration of Cosmic Web & Mkn 421
This illustration shows the absorption of X-rays from the quasar Mkn 421 by two intergalactic clouds of diffuse hot gas. These distant clouds (located 150 million and 370 million light years from Earth), are likely part of a predicted diffuse web-like system of hot gas clouds - the cosmic web - from which galaxies and clusters of galaxies are thought to have formed. This discovery is strong evidence that atoms and ions known to be present shortly after the Big Bang, but missing in inventories of matter in the present era, are hiding in the hard-to-see cosmic web.
(Credit: NASA/CXC/M.Weiss)

Chandra X-ray Image with Scale Bar
Scalebar = .1 arcmin
(Credit: NASA/SAO/CXC/F.Nicastro et al.)