Student Researchers Study Supernova Variations
McKinley Brumback ’14 and Katie Pierce ’14 are working with Assistant Professor of Physics Natalia Connolly and her husband, University of Pennsylvania Postdoctoral Researcher Brian Connolly, on a summer research project that has the potential to fundamentally change much of what is known about the universe.
The 2011 Nobel Prize in Physics was awarded to three physicists for a groundbreaking discovery on the increasing speed of the universe’s expansion, but their theory, like countless others before it, relies upon a simple yet fundamentally unproven assumption of modern physics: that all Type Ia supernovae, or white dwarf star explosions, emit the same amount of light.
Given this assumption, astronomers can use Type Ia supernovae as “standard candles,” or units of measure to calculate distance based on the known speed of light. The Connollys, however, have theorized that there may be subtypes in the Type Ia supernova group, and even the smallest variation in Type Ia supernova brightness has the potential to drastically alter spatial distance calculations.
In order to aid the Connollys in disproving this Type Ia supernova assumption, physics majors Brumback and Pierce are creating a program to analyze data from 33 supernova that occurred between 1997 and 2001. While a sample size of 33 star explosions may seem small, the data set is actually made up of tens of thousands of individual snapshots of stellar light. By using a statistical method known as the Bayesian Information Criterion to compare the points, the two hope to detect patterns of deviation in the brightness of the supernova explosions.
The students’ work involved extensive programming and debugging in the C++ programming language before even a subset of data could be run. Both researchers were new to the language, but after months of hard work learning its subtleties and writing their program, their creation is now in its final stages of completion and testing. Once their program finishes running a set of data, a process that can take anywhere from a few hours to a day, the researchers analyze the resulting graphs, searching for the desired spectral patterns.
A particularly frightening moment for the researchers took place when a weekend power surge caused the cooling system for the group’s server to fail and their hard disks to overheat. Brumback and Pierce feared that their entire summer’s research had been lost, but the Connollys managed to recover nearly all of the group’s data after a week of working with the failed hard disks.
As of now, the Connollys still have yet to identify the patterns they set out searching for; however, Brumback and Pierce do have the satisfaction of knowing that their program runs almost entirely without issue. The group has identified dot products, a less accurate measure of sameness, that conform to their expectations of Type Ia supernova subcategories, and they hope to confirm this finding using the Bayesian Information Criterion.
Brumback, who has a passion for astrophysics and hopes to teach on the subject one day, is one of only two student volunteers trained to open and operate the Hamilton CHF Peters Astronomical Observatory. Pierce, who plans to become a laboratory researcher, enjoys exploring the different branches of physics as she plans for her future career.
Brumback is a graduate of The Bryn Mawr School (Md.) and Pierce is a graduate of Clinton High School (N.Y.)