The evolution of the supernova remnant Cassiopeia A is shown by combining X-ray images taken by the Chandra X-ray Observatory in January 2000, February 2002, February 2004 and December 2007. Lowest energy X-rays are shown in red, intermediate energies in green and the highest X-ray energies in blue. The explosion’s outer blast wave, moving slower than expected, is also shown in blue.

Posted in 'Evolution, 3-D animation of Cassiopeia A' at sciencenews.org/view/generic/id/39716/title/Evolution%2C_3-D_animation_of_Cassiopeia_A

Credit: D. Patnaude et al., CXC, SAO, NASA