Dusty grains -- including tiny specks of the minerals found in the
gemstones peridot, sapphires and rubies -- can be seen blowing in the
winds of a quasar, or active black hole, in this artist's concept. The
quasar is at the center of a distant galaxy.
Astronomers using NASA's Spitzer Space Telescope found evidence that such
quasar winds might have forged these dusty particles in the very early
universe. The findings are another clue in an ongoing cosmic mystery:
where did all the dust in our young universe come from?
Dust is crucial for efficient star formation as it allows the giant clouds
where stars are born to cool quickly and collapse into new stars. Once a
star has formed, dust is also needed to make planets and living creatures.
Dust has been seen as far back as when the universe was less than a tenth
of its current age, but how did it get there? Most dust in our current
epoch forms in the winds of evolved stars that did not exist when the
universe was young.
Theorists had predicted that winds from quasars growing in the centers of
distant galaxies might be a source of this dust. While the environment
close to a quasar is too hot for large molecules like dust grains to
survive, dust has been found in the cooler, outer regions. Astronomers now
have evidence that dust is created in these outer winds.
Using Spitzer's infrared spectrograph instrument, scientists found a
wealth of dust grains in a quasar called PG2112+059 located at the center
of a galaxy 8 billion light-years away. The grains - including corundum
(sapphires and rubies); forsterite (peridot); and periclase (naturally
occurring in marble) - are not typically found in galaxies without
quasars, suggesting they might have been freshly formed in the quasar's
winds.
