Swan Lake -- The Celestial Version

December 09, 2008

Stellar winds are so stiff in the Swan nebula -- scientists estimate the speed at 4.5 million mph -- that its clouds of dust are being swept away -- literally. This new image from the infrared-sensitive Spitzer Space Telescope shows what happens when ripples of gas, which are streaming from a collection of massive stars at the center of the nebula, crash into star-forming regions.

The force of the winds, as well as the radiation, are creating a cavity in the nebula, which is located about 6,000 light years away in the constellation Sagittarius. The winds come from massive stars, some of which are more than 40 times bigger than our sun.

"The gas being lit up in these star-forming regions looks very wispy and fragile, but looks can be deceiving," astronomer Robert Benjamin of the University of Wisconsin, Whitewater, said in a press release.

Colleague and lead researcher Matt Povich, with University of Wisconsin, Madison, adds, " The growth of this cavity pushes gas up against winds from other massive stars, causing 'smiley-faced' bow shocks -- three of which can be seen in the new picture.

"The direction of the bow shocks tells researchers exactly which way the 'wind is blowing,' " added Povich, the lead author of a paper about the discovery appearing in this week's Astrophysical Journal.

The picture is one of the first examples of multiple bow shocks around massive stars in a star-forming region.

"These bow shocks serve as a reminder that stars aren't born in quiet nurseries, but in violent regions buffeted by winds more powerful than anything we see on Earth," Benjamin said.