Only The Sky Is The Limit

from the
THE HARVARD COLLEGE
UNDERGRADUATE RESEARCH PROGRAMS NEWSLETTER
January 2001

Ann Marie Cody '03 has long been reaching for the stars. A Harvard, MA native, Ann Marie found intriguing the evidence detected by astrophysicists in 1995, that there are at least 30 Jupiter and Saturn-like gaseous planets orbiting distant stars. "Not only have these discoveries provided spectacular confirmation that our solar system is not alone, but they have also revolutionized current theories on the formation of planetary systems. One of the most surprising findings has been the counterintuitive observations that many of these massive new planets orbit extremely close to their parent stars."

As a high school senior, Ann Marie decided to pursue her interest in this expanding field further. She began working with Professor Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics. "Astronomy had been a long-standing interest of mine, and I was very pleased to be able to carry out investigations of extrasolar planets and their parent stars through an internship during my last years in high school." When Ann Marie arrived at Harvard she learned of the Harvard College Research Program and applied early in her college career.

The research that Ann Marie conducted during the spring of her freshman year allowed her to continue the work she had begun as well as update her research with current developments in the field. At that point, her "plans included researching the literature for data on the parent stars of extrasolar planets, with particular concentration on close-in planets." Ann Marie was able to identify the areas of orbital distance, planet mass, stellar rotation rate, and stellar metallicity, and study their relationships. Ann Marie was also able to utilize codes on the Center for Astrophysics' computers to determine mass, radius, and evolutionary tracks for parent stars of extrasolar planets. The results of this work would provide more information about the formation and evolution of extrasolar planet systems.

"As a side project, I placed special focus on the star HD 209458, which had been reported to display the first evidence of a planetary transit." The data gathered would ultimately be used to make refinements on the radius of the star, "which would, in turn, reveal a wealth of information about the planet's atmosphere and composition."

By the end of her spring semester, Ann Marie had not only increased her knowledge of astrophysics as a topic in general, but also made great progress on her initial research topic. While she had gathered scientific information and assembled data profiles for several other stars, she was able to create numerous computer models and plot evolutionary tracks for the star HD209458. In fact, she was nearly ready to produce a refined estimate of its radius.

Ann Marie decided it was time to "take my studies further by honing calculations of HD209458's properties and zeroing in on its possible age and radius ranges. These are two parameters not precisely known by the astronomical community, and they are essential to current research." Professor Sasselov noted that during the summer months they would "complete the computations, derive accurate physical parameters for HD 209458, and prepare an article for publication. The field of extrasolar planets is as exciting as ever, and the focus of Ann Marie's research is of immediate interest."

To that end, Ann Marie decided to apply for further funding from the Harvard College Research Program for the summer. The continued funding took the form of a stipend in order for her to conduct her research in the lab for a wage as opposed to having to look for a part-time job to cover her summer expenses. Conducting research on campus during the summer allowed Ann Marie the opportunity to work more closely with her faculty sponsor. Professor Sasselov "invited me to participate in research discussions with scientists and graduate students, and has also displayed some of my results and diagrams at a major symposium during the meeting of the International Astronomical Union in Europe. I was pleased to hear that no other extrasolar planet researchers are currently attempting the kind of computer-based analysis that we are using."

Almost more important for the burgeoning scientist, Ann Marie notes that "to further hone my skills, Professor Sasselov has given me a great deal of encouragement to develop independence and scientific intuition in my work. While he is always ready to entertain my numerous questions, he often points me toward useful literature, rather than providing a quick, simple answer. I appreciate the high expectations that he places on me."

For his part, Professor Sasselov states that "during the past year Ann Marie has accomplished a lot. I dare say that what she has accomplished is comparable to work done even by some of our graduate students. Her project is both fundamental and exciting, and some of my colleagues are already starting to pay attention to her work. Ann Marie and I have written a paper, which is on my desk and ready to be submitted to the professional journal with highest standards The Astrophysical Journal. Ann Marie did the major part of the work and of the writing of the paper, and is deservedly the first author."

This fall, Ann Marie proposed to research a much broader context of extrasolar planet systems. "Recently, it has been hypothesized that planets in unstable orbits may migrate inward and eventually fall into their parent star's atmosphere. This process would lead to a significant increase in the heavy metal content in the uppermost layers of the star. I plan to attack the problem by examining the metallicities of a considerable sample of these stars and exploring the effects of high and low-metal atmospheres using my computer modeling skills. I hope to determine whether metal "pollution" has an observable effect, and how strong the current evidence is for planetary migration."

Given that Ann Marie applied for funding during her first year, she has accomplished a great deal of research. Upon further application to the program, is it likely that she will continue to receive funding throughout her college career.