The blown-out remains of supernova Cassiopeia A, as seen by NASA's Spitzer Space Telescope. Clockwise from upper left: a composite made up of three infrared views shown in the remaining panels; silicon gas (blue) deep in the interior of the remnant; argon gas (green) that synthesized as it was ejected from the star; a collection of silicate, iron and aluminum-containing dust (red). The features line up and tell astronomers that the dust, together with the gas, was created in the explosion. Credit: NASA/JPL-Caltech
