This two-panel graphic compares an artist’s illustration (left) of a simplified picture of the inner layers of a star just before it exploded to form the Cassiopeia A supernova remnant with a Chandra image (right) of what we see today. The different elements are represented by different colors: iron (blue), sulfur and silicon (green), and magnesium, neon and oxygen (red). The Chandra image uses the same color scheme to show the distribution of iron, sulfur and magnesium in the supernova remnant. A comparison of the illustration and the Chandra element map shows clearly that most of the iron, which according to theoretical models of the pre-supernova was originally on the inside of the star, is now located near the outer edges of the remnant.
