New Milky Way Map Created; Shows Fewer Main Arms

June 3, 2008

Astronomers unveiled today what they are calling the best map ever produced of the Milky Way galaxy.

The new view shows our spiral galaxy as it would look face-on to a very distant observer.

The map is based on findings about the structural evolution of the Milky Way presented this week at the 212th meeting of the American Astronomical Society in St. Louis, Missouri.

Robert Benjamin of the University of Wisconsin-Whitewater was among the scientists who presented results at a briefing today with reporters.

The researchers determined that the Milky Way actually has two fewer major arms than previously believed.

In barred spiral galaxies like our own, major arms have a high density of stars, produce lots of new stars, and are clearly connected to the long bar of stars at the galactic center.

(See an image of the bar of stars at the center of the Milky Way.)

By contrast, minor arms have high gas density and presumably less star formation.

Scientists had long thought that the Milky Way has four major arms. But the new images show that the spirals are actually made of two major arms and two minor ones.

"These major arms plus the bar could be the things that really stand out if you were looking at the Milky Way galaxy from, say, [our nearest galactic neighbor] Andromeda," Benjamin said.

Sharper Resolution

Mapping the Milky Way is an unusual challenge, one that some experts have likened to a fish attempting to map the Pacific Ocean.

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