Spiral Star Blowing in the Wind

Astronomers may have solved the riddle of how dust can survive radiation streaming off blazing hot stars. By cleverly masking parts of a giant telescope, a team captured images, unveiled in today's Nature, showing a graceful spiraling dust trail that models suggest was created by colliding stellar winds.

Dusty winds flow from the surfaces of some stars, but these stars burn so hot that any nearby dust should be vaporized. One way to resolve this seeming paradox, astronomers have speculated, is for a second stellar wind from a nearby star to collide with the first wind, cooling the gas enough to preserve dust. One such dust-encircled star, Wolf-Rayet 104 (WR104), lies so far away--some 17 million billion kilometers--that not even the vaunted 10-meter Keck I on Mauna Kea in Hawaii can discern any fainter stars in the vicinity of WR104.

That was the situation until Peter Tuthill, a postdoctoral research physicist at the University of California, Berkeley, and his co-workers hit upon the idea to help the Keck telescope squint. They placed a perforated metal plate over the aperture, such that each hole forms a separate image of the star, like a pinhole camera. By combining hundreds of these images in a computer, a technique called interferometry, the team improved the telescope's resolution 10-fold--and found a rotating spiral of dust near WR104. Although the Keck was unable to pick out a nearby star, the computer simulations suggest that the dust stream is probably shaped by colliding stellar winds.

"They have done a really nice job," says Ken Johnston, an astronomer at the U.S. Naval Observatory in Washington, D.C. Because WR104 is only the first star in its class to be observed with the new technique, team member Bill Danchi hopes to turn up some dusty binaries. "We did this observation for peanuts," he says, "think what the new generation of big interferometers will do."

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