Credit: NASA/JPL-Caltech/J. Rho (Caltech-SSC)

This infrared image shows silicon gas (blue) deep in the interior of the supernova remnant Cassiopeia A. This cooler gas, called the unshocked ejecta, was synthesized in the supernova blast.

The data for this image was taken by Spitzer's infrared spectrograph, which splits light apart to reveal the fingerprints of molecules and elements. In total, Spitzer collected separate "spectra" at more than 1,700 positions across Cassiopeia A.