UW-Whitewater professor gives the Milky Way a makeover
Released: June 3, 2008
A landmark astronomical discovery about our very own Milky Way galaxy was announced today by assistant professor Robert Benjamin at the American Astronomical Society’s 212th national meeting in St. Louis.
Benjamin’s research has shown that the Milky Way’s spiral appearance is dominated two major arms of stars and not four as previously thought. Taking data from a NASA Spitzer Space Telescope infrared survey of the Galaxy called GLIMPSE, Benjamin developed software at UW-Whitewater that allowed him to tabulate the positions and brightness of more than 100 million stars. When he looked at where the stars were concentrated in the sky, he found that there was an enhanced density of stars in the direction expected for one of the spiral arms of the galaxy, the Scutum-Centaurus Arm. However, when he looked in the direction of two other spiral arms, the Sagittarius and Norma Arms, he saw no change in the density of stars in the sky. To resolve the mystery of the Milky Way’s missing arms, he hypothesizes the existence of two different types of arms.
The two major arms, Scutum-Centaurus and Perseus, are filled with young stars along with older red-giant stars making them the strong spiral arms. The two minor arms, Sagittarius and Norma, are filled with gas and pockets of young stars that make them visible, but not as pronounced as the major arms. These two major arms are thought to wrap off the Galactic bar, the topic of a previous discovery by Benjamin.
“Spitzer has provided us with a starting point for rethinking the structure of the Milky Way,” Benjamin said. “We will keep revising our picture in the same way that early explorers sailing around the world had to keep revising their maps.”
The Web site alienearths.org/glimpse allows viewers to zoom in and pan through the galaxy.
Like much of Benjamin’s work, this discovery involved his students from UW-Whitewater.
“One of my students, Eric Phillips, performed the exact same experiment as I did, just with a different survey of Galaxy, so we could compare our results,” Benjamin said.
Benjamin tries to involve students as much as he can with his work and research. “Students can use the data and create their own programs to study them,” he said. “Some of my physics students were the first to see the data on the Milky Way discovery.”
“I also always try to incorporate my discoveries into the classroom,” Benjamin said. “I just can’t help it; I get excited.”
While the discovery is important, when it comes to UW-Whitewater students, the access to data fresh from the telescope is just as important. “UW-Whitewater students can be the first to see this data and make their own discoveries before anyone else on the planet has had a chance to see this new view of the Galaxy. That’s great motivation.”
At the start, Benjamin urges his students to discover an interesting object or two from the vast Galactic panorama and then start to figure out what they are seeing. “That’s how I got started in astronomy. I started by studying a single nova explosion, and ever since then I’ve been expanding my view.”
When it comes down to his groundbreaking discovery and the impact it has on his students, Benjamin had only this to say, “Right now, I’m a very lucky astronomer.”
- Tom Applegarth,applegartg17@uww.edu
