 |  | | | | Circumstellar Dust Takes Flight in 'The Moth'
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01.10.08
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Donna Weaver / Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4493 / 4514
dweaver@stsci.edu / villard@stsci.edu
Dean Hines
Space Science Institute, Boulder, Colo.
505-239-6762
dean.hines@colorado.edu
Michael Meyer
Steward Observatory, University of Arizona, Tucson, Ariz.
520-626-9199
mmeyer@as.arizona.edu
Release No. STScI-PR08-01
What superficially resembles a giant moth floating in space is giving
astronomers new
insight into the formation and evolution of planetary systems.
Image right: This image, taken with the Near-Infrared Camera and Multi-Object
Spectrometer (NICMOS) aboard NASA's Hubble Space Telescope, shows the wing-
shaped dust disk surrounding the young, nearby star HD 61005. Click image for enlargement. Credit: NASA, D. Hines (Space Science Institute, Corrales, New Mexico), and G. Schneider (University of Arizona)
This is not your typical flying insect. It has a wingspan of about 22
billion miles. The wing-
like structure is actually a dust disk encircling the nearby, young star
HD 61005, dubbed
"The Moth." Its shape is produced by starlight scattering off dust.
Dust disks around roughly 100-million-year-old stars like HD 61005 are
typically flat,
pancake-shaped structures where planets can form. But images taken with
NASA's Hubble
Space Telescope of "The Moth" are showing that some disks sport
surprising shapes.
"It is completely unexpected to find a dust disk with this unusual
shape," said senior
research scientist Dean Hines of the Space Science Institute in Boulder,
Colo., and a
member of the Hubble team that discovered the disk. "We think HD 61005
is plowing
through a local patch of higher-density gas in the interstellar medium,
causing material
within HD 61005's disk to be swept behind the star. What effect this
might have on the disk,
and any planets forming within it, is unknown."
Hines called this possible collision "unusual, because we don't expect
very much material to
be in the solar neighborhood. That's because the area through which our
Sun is moving was
evacuated within the past few million years by at least one supernova,
the explosion of a
massive star. Yet, here's evidence of dense material that's very close,
only 100 light-years
away."
Astronomers have found evidence that the environment in which a star
forms influences its
prospects for planet formation. Hubble has actually seen that young
planet-forming disks
can be affected directly by their environment. The harsh stellar
radiation from the Trapezium
stars in the Orion Nebula has altered some disks. It is unclear,
however, what effect
passage through a cloud similar to the one in which HD 61005 finds
itself would have on
planet formation. Researchers have speculated that passage through dense
regions of the
interstellar medium could impact the atmospheres of evolving planets.
The Moth is part of a survey of Sun-like stars that Hines and
collaborators observed with
Hubble's Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and
NASA's
Spitzer Space Telescope to study the formation and evolution of
planetary systems. Under
the lead of Michael Meyer of the University of Arizona in Tucson, the
team initially used
Spitzer to look for heat radiation - the tell-tale sign of dust warmed
by the star - to identify
interesting star systems.
Hines then teamed with Glenn Schneider of the University of Arizona to
use Hubble's high-
contrast imaging capability of the NICMOS coronagraph to image these
disks and reveal
where the dust detected by Spitzer resides. The NICMOS coronagraph
blocked out the
starlight so that astronomers could see details in the surrounding disk.
"These symbiotic capabilities, uniquely implemented in NASA's Great
Observatories,
provide astronomers with the powerful observational tools to study the
circumstellar
environments of potentially planet-forming systems," Schneider said.
Added Meyer: "Combining observations from these two spacecraft gives us
information
about the composition of the dust grains, whether they're icy or sandy,
or whether they're
like the sooty smoke particles rising from a chimney. The composition
and sizes of the dust
can tell us a lot about the dynamics and evolution of a solar system. In
our solar system, for
example, astronomers have evidence of rocks smashing into each other and
generating
dust, as in the asteroid and Kuiper belts. We're seeing these same
processes unfold in
other planetary systems."
Hines and his collaborators will report their finding on Jan. 10 at the
211th meeting of the
American Astronomical Society in Austin, Texas. The result also appeared
in the December
20 issue of the Astrophysical Journal Letters.
The Space Telescope Science Institute conducts Hubble science
operations. The institute is
operated for NASA by the Association of Universities for Research in
Astronomy, Inc.,
Washington.
Related links:
> NASA's Hubble site
> More images and information from Hubblesite.org
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