Physics professor looks to the stars for inspiration

After listening to M. Virginia McSwain, assistant professor of physics, describe her research, it’s evident that astronomy encompasses much more than gazing at stars.

McSwain did not become interested in astronomy until she took a course in stellar astrophysics in her senior year of college.

Today, she and her students travel to some of the best observatories in the Western Hemisphere to study massive stars, typically five to 50 times the mass of the sun, which form in close gravitationally bound binary systems.

In a binary system, two stars orbit around each other. As they evolve, says McSwain, one star’s radius expands and can transfer mass onto its companion.

Many of these massive stars end their lives as supernova explosions, leaving behind a neutron star or black hole. As material is accreted onto the neutron star or black hole, high-energy X-ray and gamma-ray emissions are produced.

“I study this radiation to understand the interplay between the remaining star and the neutron star,” says McSwain.

During mass transfer, angular momentum increases, causing the star to rotate more quickly. At this point, material starts streaming off the center of the star, forming a disk. A neutron star can orbit around this disk and interact with it.

McSwain specifically studies Be star systems, in which material from the disk collides with a type of rapidly rotating neutron star known as a pulsar.

“We think that the shock when a pulsar hits the disk produces gamma ray emission,” she says. McSwain uses ground-based telescopes to observe the optical light emitted by the X-ray and gamma ray sources.

Promoting undergraduate research

High-energy astrophysics has close ties to medical imaging. Techniques in both fields overlap, and the way that McSwain observes the star systems resembles the way an MRI scans patients.

“You never know what you’ll learn from pure research,” McSwain says. “You’ll understand the universe better, which will let you understand your ‘local universe’—your body. They obey the same physics.”

McSwain enjoys working with students and has taken them on some of her research trips. She has traveled to observatories in Arizona, Texas, West Virginia, Wyoming, Canada and Chile.

“Observing is fun and exciting but sometimes it’s very stressful because there are so many uncertainties,” she says. Applying for observation time is competitive and adverse weather can prevent scientists from observing.

She notes that the physics department’s Research Experience for Undergraduates program is one of the longest-running REU programs in the U.S. and has received funding since 1989 from the National Science Foundation (NSF).

Lehigh receives about 600 applications for the 10-week summer program each year and accepts only about 20 students. “We strongly encourage our undergrads to apply for the REU program, both here and elsewhere, to get research experience,” she says.

McSwain’s research is supported by NASA and by Lehigh. After receiving her Ph.D. in astronomy from Georgia State University in 2004, she was awarded an Astronomy and Astrophysics Postdoctoral Fellowship at Yale University from the National Science Foundation. She joined the faculty in 2007.