Don’t accuse Virginia McSwain of having her head in the clouds. She’s set her sights on something much higher. An astronomer, McSwain came to Lehigh with a passion for stars and is now helping to bolster the university’s astrophysics program.
McSwain, a new faculty member in the physics department
, joins professors George McClusky and Gary DeLeo in Lehigh’s astronomy group. Lehigh undergraduates can currently obtain a B.S. in astrophysics or a B.A. in astronomy.
“I hope to develop new courses and broaden the program,” says McSwain, who noted that there’s a growing interest in the field both here at Lehigh and among college students in general.
In addition to her teaching responsibilities, McSwain is still very much involved in the research she began during her graduate work at Georgia State University and continued while completing an NSF Astronomy and Astrophysics Postdoctoral Fellowship at Yale University.
Among her research interests are Be stars, a special type of massive stars that have emission disks around their equators. Be stars are named such because “B” denotes the spectral class and the “e” refers to the emission. According to McSwain, the stars can be from 2-1/2 to 20 times the mass of our Sun. These stars, which are rapidly rotating, are subjected to strong centrifugal forces which are almost strong enough to lift material off the star. The rotation isn’t quite fast enough, by itself, to lift material off the star and into the disk. McSwain suspects that waves traveling over the star’s surface give the material just enough of an extra kick to put it into orbit.
Most Be stars have nearly permanent disks, and until now it was extremely unusual to see a Be star’s disk disappear. But in four years of measuring the disks in one-star cluster, she has watched 11 Be star disks grow, disappear, and then return.
“Astronomers have been studying this type of star for more than a hundred years and have never seen so many large changes in the disks over a relatively short time,” says McSwain. She believes that the surface waves are not permanent and that the disks dissipate when they aren’t fed constantly. One of her next goals is to detect these waves directly and measure how frequently they appear.
She conducts most of her research at Cerro Tololo Inter-American Observatory
in Chile. She uses spectroscopy to split the starlight into its rainbow of colors and measure the disks from their trademark red emission. To detect the surface waves, she will use photometry to look for very subtle variations in the stars’ brightnesses.
She’s returning to Chile in March 2008 to determine what the Be stars in this cluster have been doing lately, and why they’re not acting the same as most other Be stars. “This particular cluster may have something unique about it—the way the stars are assembled, their chemical abundances, interactions with other cluster members, their rotation. My colleagues and I are trying to compare lots of different qualities of this cluster with other clusters to help understand the variability we’re seeing,” says McSwain.
“From the tiny bit of light that reaches us, we can extract a lot of information,” says McSwain. “But it will take more work to see the whole picture.”