The elements and molecules that flew out of the Cassiopeia A star when it
exploded about 300 years ago can be seen clearly for the first time in
this plot of data, called a spectrum, taken by NASA's Spitzer Space
Telescope.
The spectrum, which was created by splitting light into its basic
components, reveals the composition of gas and dust that were synthesized
in the explosion. It also provides some of the best evidence yet that
stellar explosions, called supernovae, were a significant source of fresh
dust in the very young universe. Prior to these observations, nobody was
certain where this early dust—the same dust that ultimately made its
way into future stars, planets and people—came from.
One of the most interesting features of the plot is a bump labeled
"Cassiopeia A dust feature." This bump is actually the signature of a
collection of dust composed of proto-silicates, silicon dioxide and iron
oxide. The spectrum reveals that the brightness of the dust feature is
correlated to that of argon gas (yellow vertical line at left), known to
have been expelled and synthesized during the star's explosion. The fact
that the dust is associated with the expelled gas, or ejecta, tells
astronomers that this supernova manufactured new dust.
Each of the three lines of this plot represents a different layer of the
supernova remnant, with the top yellow and red line being the outermost
layer. Similar correlations between gas and dust are also seen in the
middle layer (green line). For example, neon gas correlates with dust
composed of carbon and aluminum oxide.
