Undergrads look at the stars -- and find stellar recognition

By Lissa Harris

Most astronomers whose research is published in major science journals have spent years of work to get recognition. Not so for the students of Stephen Eikenberry, an assistant professor in Cornell's Department of Astronomy. Eikenberry makes sure his undergraduates have the opportunity to do important research and then to see their work published in leading astronomy journals.

"When I did my Ph.D. at Harvard, there were undergraduates involved there, but they were sorting nuts and bolts in the lab," Eikenberry mused. "Having this much undergraduate involvement is really unique to this project, even at Cornell."

Outside Cornell's Hartung-Boothroyd Observatory Dec. 12, Stephen Eikenberry, left, assistant professor of astronomy, and James Houck, far right, the Kenneth A. Wallace Professor of Astronomy, join student researchers (from left to right) Benjamin Fierce '02, Brian Cameron '03, Shannon Patel '03, Dounan Hu '04, Malia Jackson '02, and Donald Barry, staff astronomer. Robert Barker/University Photography

The prestigious Astrophysical Journal and its supplement, Astrophysical Journal Letters, recently published papers reporting on research by Eikenberry and his students, including eight undergraduates.

Junior Brian Cameron spent last summer working with Eikenberry on the curious behavior of the binary star system SS433. Cameron, in his fourth research project in the astronomy department, analyzed data collected by fellow students with the 25-inch telescope at Cornell's Hartung-Boothroyd Observatory, located on Mount Pleasant, north of the Cornell campus. Their research was published in the Nov. 10, 2001, issue of Astrophysical Journal in a paper, "Twenty Years of Timing SS433."

Of the paper's six co-authors, four were undergraduate students who had been freshmen at the time they conducted the research: Cameron, Benjamin Fierce, David Kull and David Dror. Other authors were Eikenberry; James Houck, the Kenneth A.Wallace Professor of Astronomy at Cornell; and Bruce Margon of the Space Telescope Science Institute.

"I've been getting published for stuff I did my freshman year. I'm sure that's going to be helpful," said Cameron. "It was a big factor in deciding whether I wanted to go into academia." Indeed, as a junior, he has more research experience under his belt than most incoming graduate students, and he plans to pursue graduate work in astrophysics.

The subject of the research is a binary star system -- an ordinary star in orbit around a massive star that either has been compressed under huge gravitational forces to form an extremely high-density neutron star or has collapsed to form a black hole. Material being pulled from the surface of the orbiting star spirals around the compact object like water circling around a drain, forming a bright ring known as an accretion disk. At the same time, the accretion disk itself is "precessing," or wobbling, in a slow circular motion like a top that has begun to spin down.

Several hundred binary star systems that include compact objects are known in the Milky Way galaxy, but what makes SS433 unique is its relativistic jets -- streams of matter that are forcibly ejected from the accretion disk at about a fourth of the speed of light. Scientists can use shifts in the velocities of the jets to calculate the precessional motion of the accretion disk.

Work by Eikenberry and his students shows that the accepted model of SS433's motion is incorrect. Their data, which covers the 20 years since SS433 was discovered, reveal that the wobble, despite being extremely erratic on short time scales, is much more stable than previously had been thought.

"It's kind of like a watch, where the second hand might jitter back and forth, but two days later it has still got the right time," said Eikenberry. The Cornell group's data means that astrophysicists must revisit their assumptions about how to interpret the jets' erratic shifts in velocity.

The second paper, "Possible Infrared Counterparts to the Soft Gamma-Ray Repeater SGR 1806-20," appeared in the Dec. 20 issue of Astrophysical Journal Letters. The co-authors, besides Eikenberry and Houck, include undergraduates Dounan Hu, MaliaJackson and Shannon Patel; graduate student Michael Colonno; Northwest Nazarene University undergraduate Megan Garske; and Cornell staff astronomer Donald Barry.

The Cornell students used images obtained with the Hartung-Boothroyd Observatory's infrared camera, as well as images from the Cerro Tololo Inter-American Observatory in Chile, to determine whether infrared light is being emitted along with the gamma rays. Their ndings narrow down the potential source of the gamma rays to a very small area of the sky, with two stars as likely candidates.

Eikenberry is supporting the undergraduate research with a ve-year, $500,000 grant he received last year as part of a National Science Foundation Early Career Award. "Very rarely will you see such strong undergraduate involvement, with a small telescope in upstate New York producing cutting-edge results," said Eikenberry. "We're really excited about this."