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Gay Hill (818) 354-0344
Jet Propulsion Laboratory, Pasadena, Calif.

News Release: 2006-022 February 15,
2006

NASA's Spitzer Finds Violent Galaxies Smothered in 'Crushed Glass'

NASA's Spitzer Space Telescope has observed a rare population of
colliding galaxies whose entangled hearts are wrapped in tiny
crystals resembling crushed glass.

The crystals are essentially sand, or silicate, grains that were
formed like glass, probably in the stellar equivalent of furnaces.
This is the first time silicate crystals have been detected in a
galaxy outside of our own.

"We were surprised to find such delicate, little crystals in the
centers of some of the most violent places in the universe," said
Dr. Henrik Spoon of Cornell University, Ithaca, N.Y. He is first
author of a paper on the research appearing in the Feb. 20 issue
of the Astrophysical Journal.

"Crystals like these are easily destroyed, but in this case, they
are probably being churned out by massive, dying stars faster than
they are disappearing."

The discovery will ultimately help astronomers better understand
the evolution of galaxies, including our Milky Way, which will
merge with the nearby Andromeda galaxy billions of years from now.

"It's as though there's a huge dust storm taking place at the
center of merging galaxies," said Dr. Lee Armus, a co-author of
the paper from NASA's Spitzer Science Center at the California
Institute of Technology in Pasadena. "The silicates get kicked
up and wrap the galaxies' nuclei in giant, dusty glass blankets."

Silicates, like glass, require heat to transform into crystals.
The gem-like particles can be found in the Milky Way in limited
quantities around certain types of stars, such as our sun. On
Earth, they sparkle in sandy beaches, and at night, they can be
seen smashing into our atmosphere with other dust particles as
shooting stars. Recently, the crystals were also observed by
Spitzer inside comet Tempel 1, which was hit by NASA's Deep
Impact probe

(
http://www.spitzer.caltech.edu/Media.../release.shtml).


The crystal-coated galaxies observed by Spitzer are quite
different from our Milky Way. These bright and dusty galaxies,
called ultraluminous infrared galaxies, or "Ulirgs," are
swimming in silicate crystals. While a small fraction of the
consist of two spiral-shaped galaxies in the process of
merging into one. Their jumbled cores are hectic places,
often bursting with massive, newborn stars. Some Ulirgs are
dominated by central supermassive black holes.

So, where are all the crystals coming from? Astronomers
believe the massive stars at the galaxies' centers are the main
manufacturers. According to Spoon and his team, these stars
probably shed the crystals both before and as they blow apart
in fiery explosions called supernovae. But the delicate
crystals won't be around for long. The scientists say that
particles from supernova blasts will bombard and convert the
crystals back to a shapeless form. This whole process is
thought to be relatively short-lived.

"Imagine two flour trucks crashing into each other and
kicking up a temporary white cloud," said Spoon. "With Spitzer,
we're seeing a temporary cloud of crystallized silicates
created when two galaxies smashed together."

Spitzer's infrared spectrograph spotted the silicate crystals
in 21 of 77 Ulirgs studied. The 21 galaxies range from 240
million to 5.9 billion light-years away and are scattered
across the sky.

Spoon said the galaxies were most likely caught at just the
right time to see the crystals. The other 56 galaxies might
be about to kick up the substance, or the substance could
have already settled.

Others authors of this work include Drs. A.G.G.M. Tielens and
J. Cami of NASA's Ames Research Center, Moffett Field, Calif.;
Drs. G.C. Sloan and Jim R. Houck of Cornell; B. Sargent
of the University of Rochester, N.Y.; Dr. V. Charmandaris of
the University of Crete, Greece; and Dr. B.T. Soifer of the
Spitzer Science Center.

The Jet Propulsion Laboratory manages the Spitzer Space
Telescope mission for NASA's Science Mission Directorate,
Washington. Science operations are conducted at the Spitzer
Science Center. JPL is a division of Caltech. Spitzer's
infrared spectrograph was built by Cornell University, Ithaca,
N.Y. Its development was led by Dr. Jim Houck.

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