Multi-wavelength images help astronomers study star birth, death(Forwarded)

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Contact:
James E. Kloeppel, Physical Sciences Editor
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1/11/06

Multi-wavelength images help astronomers study star birth, death

CHAMPAIGN, Ill. -- Black and white reproductions of Vincent van Gogh's
"The Starry Night" lack the beauty and depth of the original oil
painting. In a similar fashion, images of stars and galaxies composed of
a single wavelength band cannot convey the wealth of information now
accessible to astronomers.

In recent years, a number of ground-based optical and radio surveys of
the Large and Small Magellanic Clouds -- Earth's nearest neighboring
galaxies -- have become available. New composite images of optical,
radio, infrared, ultraviolet and X-ray wavelengths are giving
astronomers at the University of Illinois at Urbana-Champaign a clearer
picture of the birth, life and death of massive stars, and their effect
on the gas and dust of the interstellar medium surrounding them.

From their birth to their death, massive stars have a tremendous impact
on their galactic surroundings. While alive, these stars energize and
enrich the interstellar medium with their strong ultraviolet radiation
and their fast stellar winds. As they die, shock waves from their death
throes inject vast quantities of mechanical energy into the interstellar
medium and can lead to the formation of future stars.

"Comparing images at different wavelengths lets us create a more
complete picture, rather than seeing only a few features in isolation,"
said You-Hua Chu, chair of the astronomy department at Illinois. "Using
multi-spectral data sets, we can examine the physical structure of the
interstellar medium and study the conditions that lead to star formation."

Massive stars interact with the interstellar medium in many ways. Their
fast stellar winds and supernova blasts can sweep up the surrounding
medium into expanding shells filled with hot gas.

"The expanding shells produce conditions that may start a new wave of
star births," said Robert Gruendl, an Illinois astronomer who uses
Spitzer Space Telescope observations to search for proto-stars. "The
combination of X-ray, optical and infrared observations allow us to
determine whether the pressure of the hot gas or compression by a
passing shock wave is responsible for triggering star formation."

In related work, Illinois astronomer Rosa Williams has added data from a
new wavelength regime to her growing database on stellar graveyards in
the Magellanic Clouds. Comparing infrared images obtained with the
Spitzer Space Telescope, Williams explored the distribution of matter
caught in the expanding shells of supernova remnants.

"We expected significant infrared emission to be generated by dust
particles," Williams said. "Instead, most of the emission from these
remnants came from heated gas."

Strong ultraviolet radiation from nearby star-forming regions may have
ionized the gas and torn apart the dust particles consisting of
hydrocarbon molecules, Williams said. "Other dust particles could have
been shattered by shock waves from the supernova."

To solve the missing dust mystery, Williams said, "We are investigating
the nature and amount of dust in regions surrounding the supernova
remnants to see whether the deficiency in dust is inherent in the
environment or created by the remnant."

Chu, Gruendl and Williams will present their latest findings at the
American Astronomical Society meeting in Washington, D.C., on Wednesday
(Jan. 11).

The National Aeronautics and Space Administration funded their work.

Editor's note:

To reach You-Hua Chu, call 217-333-5535
To reach Rosa Williams, call 217-244-4209
To reach Robert Gruendl, call 217-244-4209

IMAGE CAPTIONS:

[Image 1:
http://www.news.uiuc.edu/WebsandThum...1n51.4hx_b.jpg (114KB)]
This false-color image shows infrared (red), optical (green), and X-ray
(blue) views of the large star-forming complex N51. The warm ionized gas
is shown in green, the hot ionized gas is in blue, and the proto-stars
are primarily in red. This color image reveals the relative position of
the expanding shell N51D and the recently formed proto-stars, allowing
astronomers to determine whether the star formation is triggered by
pressure from hot gas or by compression by a passing shock wave.

The infrared image was taken with the Spitzer Space Telescope's Infrared
Array Camera (IRAC) at a wavelength of 8 microns. The optical image of
hydrogen emission was taken as part of the Magellanic Cloud
Emission-Line Survey (MCELS) with the Curtis-Schmidt Telescope at Cerro
Tololo Inter-American Observatory in Chile. The X-ray image was taken
with the European Space Agency's satellite, XMM-Newton, using its
European Photon Imaging Camera (EPIC) camera.

Credit: NASA/SSC/MCELS/ESA/U.Illinois (Y.-H. Chu and R. A. Gruendl)

[Image 2:
http://www.news.uiuc.edu/WebsandThum...1chandra_b.jpg (104KB)]
This false-color image shows infrared (red), optical (green), and X-ray
(blue) views of the N49 supernova remnant. This object, the remains of
an exploded star, has million-degree gas in the center, with much cooler
gas at the outer parts of the remnant. While astronomers expected that
dust particles were generating most of the infrared emission, the study
of this object indicates that much of the infrared is instead generated
in heated gas.

Images forming this composite were taken with NASA's three Great
Observatories. The infrared image was taken with the Spitzer Space
Telescope's Multiband Imaging Photometer for Spitzer (MIPS) at a
wavelength of 24 microns. The optical image was taken with the Hubble
Space Telescope's Wide Field Planetary Camera 2 (WFPC2) of hydrogen
emission. The X-ray image was taken with the Chandra X-ray Observatory's
Advanced CCD Imaging Spectrometer.

Credit: NASA (SSC/HST/CXC), U.Illinois (R.Williams & Y.-H.Chu)