Superbubble of supernova remnants caught in act of forming (Forwarded)

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University of Illinois at Urbana-Champaign
Champaign, Illinois

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James E. Kloeppel, Physical Sciences Editor
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Released: 1/9/07

Superbubble of supernova remnants caught in act of forming

CHAMPAIGN, Ill. -- A superbubble in space, caught in the act of forming,
can help scientists better understand the life and death of massive stars,
say researchers at the University of Illinois at Urbana-Champaign.

Found within the Small Magellanic Cloud -- a galactic neighbor of the
Milky Way -- the large region of ionized hydrogen gas is designated
"LHa115-N19," and "contains a number of massive stars and overlapping
supernova remnants," said Rosa Williams, an astronomer at the U. of I. "We
can tell there has been a fair amount of stellar activity going on."

From birth to death, massive stars have a tremendous impact on their
surroundings. While alive, these stars generate stellar winds that push
away nearby gas and dust, forming low-density cavities inside expanding
bubbles. When the stars die, shock waves from their death throes can
enlarge those bubbles into huge supernova remnants.

"In N19, we have not one star, but a number of massive stars blowing
bubbles and we have several supernova remnants," Williams said. "Some of
these cavities may overlap with one another. Eventually, these bubbles
could merge into one enormous cavity, called a superbubble."

To identify the locations of massive stars, stellar-wind bubbles and
supernova remnants in N19, Williams and colleagues combined optical
images, X-ray data and spectroscopic measurements.

"We caught this particular region of N19 at a neat moment in time,"
Williams said. "The stars are just dispersed enough that their stellar
winds and supernova blasts are working together, but have not yet carved
out a full cavity. We are witnessing the birth of a superbubble."

The behavior of matter and energy within a superbubble has implications
for the formation of planetary systems, said Williams, who will present
her team's findings at the American Astronomical Society meeting in
Seattle, on Tuesday (Jan. 9).

During its life and death, a massive star forges the heavy elements that
enrich the interstellar medium and form planets. "Our own solar system may
have formed within the confines of a superbubble," said Williams, who uses
an analogy with people to help explain her interest in superbubbles.

"Some people live pretty independently in isolated country houses, while
others live in large cities that require a centralized structure,"
Williams said. "In N19, we are looking at a possible bridge between an
individual star living its life and dying its death, and a community of
stars, where living and dying affects other stars and planets, and creates
a structure around them."

Collaborators on the project with Williams are You-Hua Chu, Rosie Chen and
Robert Gruendl at Illinois, and Sean Points and Chris Smith at the
Cerro-Tololo Inter-American Observatory in Chile.

The work was funded by NASA and the Smithsonian Astrophysical Observatory.

Editor's note: To reach Rosa Williams, call 217-244-4209.

IMAGE CAPTION:
[http://www.news.uiuc.edu/WebsandThum...osa/0108_b.jpg (179KB)]
These images show the "LHA 115-N 19" region in the Small Magellanic Cloud.
This area hosts a number of massive stars, as well as three supernova
remnants (marked in the left-hand image). The amount of activity from
massive stars in this region may eventually form a huge low-density cavity
called a superbubble.

Left: 3-color image showing emission in an optical hydrogen line taken at
Cerro-Tololo Inter-American Observatory (red); radio data from the
Australia Telescope Compact Array (green); and X-ray emission from the
Chandra X-ray Observatory (blue). Right: 3-color image showing X-ray
emission at different energies: low (0.3-0.8 keV) in red, medium (0.8-1.5
keV) in green, and high (1.5-8.0 keV) in blue. The X-ray images have been
adaptively smoothed.

Photo courtesy Rosa Williams