This Chandra image shows gravitationally-bound, hot gas enveloping the distant galaxy known as 3C294. This X-ray emission is considered a signature for an extremely massive cluster of galaxies – one of the largest known structures in the universe. Astronomers believe they have captured the cluster surrounding 3C294 at a time when the universe was only 20 percent of its current age. This faraway cluster may therefore have important implications for the understanding how the universe evolved from a much earlier epoch.
The vast clouds of hot gas that surround clusters of galaxies are thought to be heated by the collapse toward the center of the cluster. Until Chandra, X-ray telescopes have not had the needed sensitivity to identify this signature X-ray emission of such distant galaxy clusters.
The Daily Galaxy via Chandra X-Ray Telescope