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LEGACY TEAM WILL USE SPACE INFRARED TELESCOPE FACILITY
TO TRACE FORMATION, EVOLUTION OF PLANETARY SYSTEMS

From Lori Stiles, UA News Services, 520-621-1877)
April 14, 2003

Part 1 of 2

Astronomers soon will look at dust disks evolving around Milky Way
stars to learn if solar systems like ours are rare or commonplace.

"We will look for signatures of planets that sculpt circumstellar
dust in a sample of 300 solar-like stars ranging in age from 3
million to 3 billion years," said Michael R. Meyer of the University
of Arizona Steward Observatory.

Meyer is principal investigator for a team that will use the Space
Infrared Telescope Facility (SIRTF) in the Legacy Science Program
project, "The Formation and Evolution of Planetary Systems: Placing
Our Solar System in Context."

-------------------------------------------------
Contact Information
Michael R. Meyer
520-626-9199  mmeyer{at}as.arizona.edu

FEPS website - http://feps.as.arizona.edu/outreach.html
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Five other teams, including one headed by UA astronomer Robert C.
Kennicutt Jr., also were chosen for the SIRTF Legacy Science Program.
The six projects comprise more than 3,000 hours of observations, or
about half the time available during SIRTF's first year of operation.

The fourth and last of NASA's Great Observatories, SIRTF is scheduled
for launch April 26 or soon after.  It will view the universe at very
long wavelengths, the far infrared, and see objects that are too
cool, too dust-enshrouded or too far away to otherwise be seen.

The three previous Great Observatories are the Hubble Space
Telescope, Compton Gamma Ray, and Chandra X-ray Observatories. SIRTF
is managed for NASA by the Jet Propulsion Laboratory, Pasadena,
Calif.

The SIRTF telescope is designed to operate at a temperature of only a
few degrees above absolute zero. It carries three science
instruments. One of these is a highly sensitive camera called MIPS
that uses imaging arrays at far-infared wavelengths and will see the
coolest objects in space. It was built by a team headed by the UA
astronomy Professor George H. Rieke. 

"SIRTF has unprecedented sensitivity at long infrared wavelengths,"
Meyer said. "It will be a powerful instrument for viewing
circumstellar dust as it evolves from the earliest stages of planet
formation toward mature planetary systems like our own."

Because SIRTF will detect very cold dust, Meyer's project may reveal
planets far from their stars ­ as far as Uranus and Neptune are from
our sun. These planets have such long orbital periods that it would
take many decades to detect them using radial velocity techniques
that since 1995 have successfully been used to find Jupiter-like
planets orbiting very close to their stars.

"We would like to locate things that are directly analogous to our
own solar system. SIRTF will provide really the first evidence of the
diversity of solar systems going out to these large radii," Meyer
said. 

"We won't actually see beautiful resolved images of a circumstellar
disk around a young star of interest," he explained. "We'll simply
see radiation from the dust at different wavelengths and then
construct spectral energy distributions, curves of how much energy
there is per wavelength, which allows us to model distribution of
dust. 

"Dust close to the star will be very hot and will emit at shorter
wavelengths. Dust that is very cold and far from the star will emit
at very long wavelengths. So by looking at ratios of hot dust to warm
dust to cold dust, we'll be able to build a model for the dust
distributions in the system."

Our own solar system provides an example, he added. It has an inner
dust disk called the zodiacal dust disk, generated by asteroids
colliding in the asteroid belt between Mars and Jupiter. These dust
grains are heated as they stream toward the sun. As they increase in
temperature, they emit more light at shorter infrared wavelengths.

Our solar system also has an outer dust disk beyond the orbit of
Neptune, where Kuiper Belt objects smash against each other and
generate dust. This dust is cold, and emits most of its light at much
longer wavelengths. In between, planet Jupiter sweeps our solar
system clean of dust, creating a huge gap in the dust disk around our
sun. 

 - Continued -

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