Franklin & Marshall College Franklin & Marshall College

An Elusive Pulsar

  • Gilpin, Crawford and Schmidt

Ten years ago, Fronefield Crawford was part of a team of astronomers that discovered a binary pulsar approximately 2,500 light years away from Earth. Then, the assistant professor of Astronomy at Franklin & Marshall College says something strange happened —the pulsar, a rapidly rotating neutron star the size of New York City, vanished.

The disappearing act meant that Crawford and his colleagues could not regularly observe and study their discovery. Several years later, they got another surprise. The pulsar was detected again by a radio telescope, this time at a higher observing frequency. The most likely explanation was that the pulsar had been eclipsed by its companion star.

“It’s an elusive pulsar,” Crawford says. “Observations prior to 2006 were done at a lower frequency than they are now. Radio waves are blocked more easily by a companion star at a lower frequency and are more transparent at a higher frequency. It’s a bit like turning your radio dial up to a higher frequency to hear a broadcast on a different channel.”

Crawford is leading the effort to learn more about the pulsar system, initially through observing runs at the Robert C. Byrd Green Bank Telescope in West Virginia, the world’s largest fully steerable radio telescope. Joining Crawford in the deep-space exploration are two F&M students, Claire Gilpin and Debbie Schmidt, both Astrophysics majors.

In February 2010 the students traveled to West Virginia to collect and analyze data from the Green Bank Telescope. The investigation continues, and Crawford says it will take him and his team at least a year of regular observations to more fully understand the pulsar’s physical properties.

“Having the opportunity to involve Claire and Debbie in this research project at such an early stage in their careers has been a joy for me—and a productive experience for all of us.”