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Superbubble of supernova remnants caught in act of forming

James E. Kloeppel, Physical Sciences Editor

Released 1/9/2007

the "LHA 115-N 19" region in the Small Magellanic Cloud
Click photo to enlarge
Photo courtesy Rosa Williams

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.

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; e-mail: