NASA Chandra Image: Cassiopeia A supernova

This colourful image of Cassiopeia A, taken by the Chandra X-Ray Observatory in 2009, shows an exploded star 11,000 light-years away. 

The green ring surrounding the supernova is from the initial shock wave generated by the explosion; it measures 10 light years in diameter. 

The bright blue areas are nearly pure iron gas from the hottest part of the star.

Credit: NASA Chandra