The false colors in this x-ray image of the Cassiopeia A supernova remnant show the varying strengths of x-rays emitted from different parts of the nebula and reveal otherwise invisible aspects of its structure.
The nebula has a dual structure:
a fainter outer shell (blue) and a brighter inner one (yellow and red). Astronomers believe the outer
shell results from intense heat produced where the outer layers
of the decimated star have collided with interstellar gas and dust.
The inner shell is the result of the even greater heat generated when heavy elements, from deep within the original star, penetrate the outer layers and move into interstellar space. The mass of the entire nebula may be up to 30 times
