NASA'S Spitzer Sees Crystal "Rain" In Outer Clouds Of Infant Star
WASHINGTON -- Tiny crystals of a green mineral called olivine arefalling down like rain on a burgeoning star, according to
observations from NASA's Spitzer Space Telescope.
This is the first time such crystals have been observed in the dusty
clouds of gas that collapse around forming stars. Astronomers are
still debating how the crystals got there, but the most likely
culprits are jets of gas blasting away from the embryonic star.
"You need temperatures as hot as lava to make these crystals," said
Tom Megeath of the University of Toledo in Ohio. He is the principal
investigator of the research and the second author of a new study
appearing in Astrophysical Journal Letters. "We propose that the
crystals were cooked up near the surface of the forming star, then
carried up into the surrounding cloud where temperatures are much
colder, and ultimately fell down again like glitter."
Spitzer's infrared detectors spotted the crystal rain around a
distant, sun-like embryonic star, or proto-star, referred to as
HOPS-68, in the constellation Orion.
The crystals are in the form of forsterite. They belong to the olivine
family of silicate minerals and can be found everywhere from a
periodot gemstone to the green sand beaches of Hawaii to remote
galaxies. NASA's Stardust and Deep Impact missions both detected the
crystals in their close-up studies of comets.
"If you could somehow transport yourself inside this proto-star's
collapsing gas cloud, it would be very dark," said Charles Poteet,
lead author of the new study, also from the University of Toledo.
"But the tiny crystals might catch whatever light is present,
resulting in a green sparkle against a black, dusty backdrop."
Forsterite crystals were spotted before in the swirling planet-forming
disks that surround young stars. The discovery of the crystals in the
outer collapsing cloud of a proto-star is surprising because of the
cloud's colder temperatures, about minus 280 degrees Fahrenheit
(minus 170 degrees Celsius). This led the team of astronomers to
speculate the jets may in fact be transporting the cooked-up crystals
to the chilly outer cloud.
The findings might also explain why comets, which form in the frigid
outskirts of our solar system, contain the same type of crystals.
Comets are born in regions where water is frozen, much colder than
the searing temperatures needed to form the crystals, approximately
1,300 degrees Fahrenheit (700 degrees Celsius). The leading theory on
how comets acquired the crystals is that materials in our young solar
system mingled together in a planet-forming disk. In this scenario,
materials that formed near the sun, such as the crystals, eventually
migrated out to the outer, cooler regions of the solar system.
Poteet and his colleagues say this scenario could still be true but
speculate that jets might have lifted crystals into the collapsing
cloud of gas surrounding our early sun before raining onto the outer
regions of our forming solar system. Eventually, the crystals would
have been frozen into comets.
The Herschel Space Observatory, a European Space Agency-led mission
with important NASA contributions, also participated in the study by
characterizing the forming star.
"Infrared telescopes such as Spitzer and now Herschel are providing an
exciting picture of how all the ingredients of the cosmic stew that
makes planetary systems are blended together," said Bill Danchi,
senior astrophysicist and program scientist at NASA Headquarters in
Washington.
The Spitzer observations were made before it used up its liquid
coolant in May 2009 and began its warm mission.
NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the
Spitzer Space Telescope mission for the agency's Science Mission
Directorate in Washington. Science operations are conducted at the
Spitzer Science Center at the California Institute of Technology in
Pasadena. Caltech manages JPL for NASA.
For more information about Spitzer, visit:
http://www.nasa.gov/spitzer
and
http://spitzer.caltech.edu/
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