Chandra Release - January 6, 2009

Visual Description: Cassiopeia A

This series of X-ray images of the supernova remnant Cassiopeia A shows the object changing over time. The tones in this image are colorful and vibrant, with a mix of pink, purple, blue, red, green, and yellow. The structure of this celestial object resembles that of an irregular sphere. This image showcases the aftermath of a massive explosion that occurred in the constellation Cassiopeia over 300 years ago. This new movie of X-ray data from Chandra was made by combining observations taken in January 2000, February 2002, February 2004, and December 2007. In each image, the lowest-energy X-rays Chandra detects are shown in red, intermediate energies in green, and the highest energies in blue. Scientists have used the movie to measure the expansion velocity of the leading edge of the explosion's outer blast wave (bright blue along the edge). The researchers find that the velocity is 11 million miles per hour, which is significantly slower than expected for an explosion with the energy estimated to have been released in Cas A.