Galactic survey reveals a new look for the Milky Way

Aug 16, 2005

The Milky Way, it turns out, is no ordinary spiral galaxy. According to a massive new survey of stars at the heart of the galaxy by Wisconsin astronomers, including professor of astonomy Edward Churchwell and professor of physics Robert Benjamin, the Milky Way has a definitive bar feature -- some 27,000 light years in length -- that distinguishes it from pedestrian spiral galaxies, as shown in this artist's rendering. The survey, conducted using NASA's Spitzer Space Telescope, sampled light from an estimated 30 million stars in the plane of the galaxy in an effort to build a detailed portrait of the inner regions of the Milky Way.

With the help of NASA's Spitzer Space Telescope, astronomers have conducted the most comprehensive structural analysis of our galaxy and have found tantalizing new evidence that the Milky Way is much different from your ordinary spiral galaxy.

The survey using the orbiting infrared telescope provides the fine details of a long central bar feature that distinguishes the Milky Way from more pedestrian spiral galaxies.

"This is the best evidence ever for this long central bar in our galaxy," says Ed Churchwell, a UW-Madison professor of astronomy and a senior author of a paper describing the new work in an upcoming edition of Astrophysical Journal Letters, a leading astronomy journal.

Using the orbiting infrared telescope, the group of astronomers surveyed some 30 million stars in the plane of the galaxy in an effort to build a detailed portrait of the inner regions of the Milky Way. The task, according to Churchwell, is like trying to describe the boundaries of a forest from a vantage point deep within the woods: "This is hard to do from within the galaxy."

Spitzer's capabilities, however, helped the astronomers cut through obscuring clouds of interstellar dust to gather infrared starlight from tens of millions of stars at the center of the galaxy. The new survey gives the most detailed picture to date of the inner regions of the Milky Way.

"We're observing at wavelengths where the galaxy is more transparent, and we're bringing tens of millions of objects into the equation," says Robert Benjamin, the lead author of the new study and a professor of physics at the University of Wisconsin-Whitewater.

The possibility that the Milky Way Galaxy has a long stellar bar through its center has long been considered by astronomers, and such phenomena are not unheard of in galactic taxonomy. They are clearly evident in other galaxies, and it is a structural characteristic that adds definition beyond the swirling arms of typical spiral galaxies.

The new study provides the best estimates for the size and orientation of the bar, which are far different from previous estimates.

It shows a bar, consisting of relatively old and red stars, spanning the center of the galaxy roughly 27,000 light years in length - 7,000 light years longer than previously believed. It also shows that the bar is oriented at about a 45-degree angle relative to a line joining the sun and the center of the galaxy.

Previously, astronomers debated whether a presumed central feature of the galaxy would be a bar structure or a central ellipse - or both. The new research, the Wisconsin astronomers say, clearly shows a bar-like structure.

"To date, this is the best evidence for a long bar in our galaxy," Benjamin asserts. "It's hard to argue with this data."

The Spitzer Space Telescope was lofted into orbit in August of 2003. It consists of a telescope and three science instruments, including the Infrared Array Camera, the primary instrument used for the new survey, known as GLIMPSE for Galactic Legacy Mid-Plane Survey Extraordinaire.

Source: University of Wisconsin System

Explore further: The Milky Way's new neighbour

add to favorites email to friend print save as pdf

Related Stories

Team creates Milky Way structure simulations

Nov 18, 2014

If you took a photograph of the Milky Way galaxy today from a distance, the photo would show a spiral galaxy with a bright, central bar (sometimes called a bulge) of dense star populations. The Sun—very ...

Image: Galactic wheel of life shines in infrared

Oct 24, 2014

It might look like a spoked wheel or even a "Chakram" weapon wielded by warriors like "Xena," from the fictional TV show, but this ringed galaxy is actually a vast place of stellar life. A newly released ...

Spirals in a galaxy may arise from density waves

Oct 09, 2014

It's often said that the shape of a spiral galaxy follows the curve of a golden spiral. You can see this, for example, in the image above. While it's often implied that this curve matches exactly, that isn't ...

A galaxy with two hearts

Jan 09, 2014

This new Hubble image shows the spiral galaxy Messier 83, otherwise known as the Southern Pinwheel Galaxy. One of the largest and closest barred spirals to us, this galaxy is dramatic and mysterious; it has ...

Recommended for you

Scientists 'map' water vapor in Martian atmosphere

5 hours ago

Russian scientists from the Space Research Institute of the Russian Academy of Sciences and the Moscow Institute of Physics and Technology (MIPT), together with their French and American colleagues, have ...

Water fleas prepared for trip to space

9 hours ago

Local 'Daphnia' waterfleas are currently being prepared by scientists at the University of Birmingham for their trip to the International Space Station (ISS), where they will be observed by astronauts.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.