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This plot of data captured by NASA's Spitzer Space Telescope reveals dust
entrained in the winds rushing away from a quasar, or growing black hole.
The quasar, called PG2112+059, is located deep inside a galaxy 8 billion
light-years away. Astronomers believe the dust might have been forged in
the winds, which would help explain where dust in the very early universe
came from.
The data were captured by Spitzer's infrared spectrograph, an instrument
that splits apart light from the quasar into a spectrum that reveals
telltale signs of different minerals. Each type of mineral, or dust grain,
has a unique signature, as can be seen in the graph, or spectrum, above.
The strongest features are from the mineral amorphous olivine, or glass
(purple); the mineral forsterite found in sand (blue); and the mineral
corundum found in rubies (light blue). The detection of forsterite and
corundum is highly unusual in galaxies without quasars. Therefore, their
presence is a key clue that these grains might have been created in the
quasar winds and not by dying stars as they are in our Milky Way galaxy.
Forsterite is destroyed quickly in normal galaxies by radiation, so it
must be continually produced to be detected by Spitzer.
Corundum is hard, and provides a seed that softer, more common minerals
usually cover up. As a result, corundum is usually not seen in spectra of
galaxies. Since Spitzer did detect the mineral, it is probably forming in
a clumpy environment, which is expected in quasar winds. All together, the
signatures of the unusual minerals in this spectrum point towards dust
grains forming in the winds blowing away from quasars.
