While examining a region where new stars are forming with NASA’s Spitzer Space Telescope, astronomers found a surprise – an object that looks like a giant tornado in space. The apparent tornado is shaped by a cosmic jet packing a powerful punch as it plows through clouds of interstellar gas and dust. They released an image of the “tornado” Jan. 12, 2006, at the 207th meeting of the American Astronomical Society in Washington, D.C.

“When I first saw the image of this tornado-like object, I was amazed,” said Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics (CfA). “In the thousands of Spitzer images we’ve looked at, we’ve never seen anything like this before.”

The “tornado” is actually a shock front created by a jet of material flowing downward through the field of view. A still- forming star located off the upper edge of the image generates this outflow. The jet slams into neighboring dust clouds at a speed of more than 100 miles per second, heating the dust to incandescence and causing it to glow with infrared light detectable by Spitzer. The triangular shape results from the wake created by the jet’s motion, similar to the wake behind a speeding boat.

The outflow that powers the “tornado,” designated Herbig-Haro 49/50, had been observed before, most recently using a ground-based telescope at the Cerro Tololo Inter-American Observatory. Intrigued by the shock emission spotted at Cerro Tololo, astronomers then targeted Spitzer onto the region and were thrilled to see a spectacular spiral structure emerge.

“The helical morphology of the `tornado’ makes it unique,” said astronomer John Bally (University of Colorado), lead author on the research.

The scientists could only speculate about the source of the spiral appearance. Magnetic fields throughout the region might have shaped the object. Alternatively, the shock might have developed instabilities as it plowed into surrounding material, creating eddies that give the “tornado” its distinctive appearance.