The Milky Way may be our own galactic neighborhood, but it still has some surprises in store. To wit: the most comprehensive structural analysis of the galaxy ever conducted indicates that ours is not a run-of-the-mill spiral one after all.

Using NASA's infrared Spitzer Space Telescope to sample light from some 30 million stars in the Milky Way, astronomers observed a long bar of relatively old stars spanning the center of the galaxy. Stellar bars are known to exist in some other spirals, and researchers have long pondered the possibility that one might reside in ours. They were unsure, however, of whether the heart of the galaxy would contain a bar structure, an ellipse or both.

The new observations paint the clearest picture yet of the Milky Way's interior and reveal the apparent bar in unprecedented detail. The feature is some 27,000 light-years long (7,000 light-years longer than expected) and sits at a 45-degree angle to the galaxy's main plane.

"To date, this is the best evidence for a long bar in our galaxy," says Robert Benjamin of the University of Wisconsin at Whitewater. Benjamin and his colleagues describe the work in a paper slated for an upcoming issue of Astrophysical Journal Letters.