Spectacular image of the supernova remnant Cassiopeia A is the most detailed image ever made of the remains of an exploded star. The one million second image shows a bright outer ring (green) ten light years in diameter that marks the location of a shock wave generated by the supernova explosion. A large jet-like structure that protrudes beyond the shock wave can be seen in the upper left. In this image, the colors represent different ranges of X-rays with red, green, and blue representing, low, medium, and higher X-ray energies. Scale: Image is 8 arcmin per side. Nine observations in 2004: February 8, April 14, 18, 20, 22, 25 28, May 01, 05, 2004.