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Pulsar-Hunting Student Makes New Discovery


People have been searching the sky for millennia, hoping to decipher its mysteries. With the advent of powerful telescopes and advanced computer equipment, many new discoveries have been made. Now, Ben Sulman ’06 has added to these discoveries, identifying a pulsar deep within the center of the Milky Way with the help of Oberlin’s new supercomputer.

Sulman discovered "his" pulsar during a summer internship at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. There he worked with astronomer Scott Ransom and NRAO's Green Bank Telescope, the largest fully steerable radio telescope in the world. Sulman helped Ransom study a star cluster known as Terzan 5, which holds a buzzing beehive of rapidly spinning millisecond pulsars - all 28,000 light years from Earth.

"I thought this would be a good opportunity for Ben to get some hands-on experience in the field," says Professor of Physics and Astronomy Dan Stinebring, who helped arrange the internship with Ransom. "Plus, he will be able to continue his research at Oberlin, now that the summer is over, with me as his mentor."

To help Ransom sort pulsars from "false" signals like radio interference, Sulman used Oberlin’s new supercomputer. After logging on to the supercomputer from his laptop in Virginia, Sulman uploaded Ransom’s data and began running a software program designed to search out pulsar candidates.

"A single observation on this star cluster is seven hours long and generates 700 gigabytes of data," Ransom says. "It would take a single desktop computer years to analyze this much data. That's why we need to use Oberlin’s supercomputer for a project like this."

The supercomputer searched through the data for a week before generating several candidates for Ransom and Sulman to study further. The duo then plotted each candidate’s frequency on a graph, checking to see if the pulse repeated itself at frequent intervals and appeared in more than one observation. In the case of Sulman's pulsar, both tests proved positive.

"The pulsar I discovered had all the typical characteristics," he says. "It repeated itself in frequent intervals and turned up in 10 out of 15 data sets that spanned a year of observation."

The information that Sulman collected was entered into a public database that can be accessed by other radio astronomers. The data can then be used to test theories of gravity such as general relativity, or to search for black holes within the star cluster.

"Scientists use the clock-like precision of pulsars to test the theories of physics," says Ransom. "By measuring the signal of a pulsar through the years, we can probe the history of a star cluster or learn more about the objects that directly surround the pulsar and affect its rotation."

Sulman's collaboration with Ransom isn't over; he plans to continue using the supercomputer to run Ransom’s data sets this semester. Sulman also plans to use the data as part of a senior honors project.

Stinebring, who will supervise Sulman's use of the supercomputer, is confident that Sulman will be able to make many more discoveries with Ransom's data sets.

"Very few undergraduate institutions have a computer powerful enough to handle the demands of this project," he says. "I’m pretty sure that this won’t be the last pulsar Ben discovers with Oberlin’s supercomputer."

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