Chandra mosaic of the X-ray sources in the Lockman Hole. Color code: Energy (red 0.4-2 keV, green 2-8 keV, blue 4-8 keV). Image is about 50 arcmin per side. Credit: X-ray: NASA/CXC/U. Wisconsin/A.Barger et al.; Illustrations: NASA/CXC/M.Weiss.
