Click on image for larger graph
This artist's concept shows delicate greenish crystals sprinkled
throughout the violent core of a pair of colliding galaxies. The white
spots represent a thriving population of stars of all sizes and ages.
NASA's Spitzer Space Telescope detected more than 20 bright and dusty
galactic mergers like the one depicted here, all teeming with the tiny
gem-like crystals.
When galaxies collide, they trigger the birth of large numbers of massive
stars. Astronomers believe these blazing hot stars act like furnaces to
produce silicate crystals in the same way that glass is made from sand.
The stars probably shed the crystals as they age, and as they blow apart
in supernovae explosions.
At the same time the crystals are being churned out, they are also being
destroyed. Fast-moving particles from supernova blasts easily convert
silicates crystals back to their amorphous, or shapeless, form.
How is Spitzer seeing the crystals if they are rapidly disappearing?
Astronomers say that, for a short period of time at the beginning of
galactic mergers, massive stars might be producing silicate crystals
faster than they are eliminating them. When our own galaxy merges with
the Andromeda galaxy in a few billion years, a similar burst of massive
stars and silicate crystals might occur.
Crystal Storm in Distant Galaxy
The graph (see inset above) of infrared data from NASA's Spitzer Space Telescope tells
astronomers that a distant galaxy called IRAS 08752+3915 is experiencing
a storm of tiny crystals made up of silicates. The crystals are similar
to the glass-like grains of sand found on Earth's many beaches.
The data were taken by Spitzer's infrared spectrograph, which splits
light open to reveal its rainbow-like components. The resulting spectrum
shown here reveals the signatures of both crystalline (green) and
non-crystalline (brown) silicates.
Spitzer detected the same crystals in 20 additional galaxies, all
belonging to a class called ultraluminous infrared galaxies. These
extremely bright and dusty galaxies usually consist of two galaxies in
the process of smashing into each other. Astronomers believe massive
stars at the hearts of the galaxies are churning out clouds of silicate
crystals. This phenomenon may represent a short-lived phase in the
evolution of galactic mergers.
