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Pulsar Research: Team Effort in Full Swing

by Jimmy Morris

Undergraduate researchers record and analyze data from stellar objects that have captured the interest of radio astronomers worldwide.

photo of pulsar research team

Studying the stars at the National Astronomy and Ionosphere Center in Puerto Rico are Joaquin Espinoza, Kate Becker, Mark Kramer, Jim Sheckhard, and physics professor Dan Stinebring.

ELEVEN P.M.: KATE BECKER ARRIVES AT THE NATIONAL ASTRONOMY AND IONOSPHERE CENTER in Arecibo, Puerto Rico, home of the largest radiotelescope in the world. The crisp air of the tropical night echoes with the incessant croaking of coquis, a sound distinct to the island, greeting her as she enters the observation building to take over the main console of the telescope.

Kate joins students Joaquin Espinoza and Clait Smith, both working in the lab with Oberlin physics professor Dan Stinebring. The team intends to record data from pulsars--stellar objects that have captured the interest of radio astronomers worldwide and whose exceedingly unique properties have proven useful in studying aspects of space. NAIC is a hotbed for the discovery of new pulsars, as well as work like Becker's involving already known pulsars. Pulsars are extremely dense stars that have exploded, then collapsed, creating a neutron star with an enormous magnetic field that rotates about once per second. These rotating magnetic fields produce pulses of radio waves that astronomers can detect with the 1,000-foot-diameter radiotelescope at Arecibo.

Becker is a third-year undergraduate research assistant from Oberlin's Pulsar Lab. This Winter Term she was one of three undergraduates working with Stinebring in using pulsars to study the interstellar medium, the vast virtual vacuum in between stars and other large objects in space. For the past few years this team has coordinated efforts at Arecibo with Cornell University's Jim Cordes and graduate student Maura McLaughlin.
Space is not as empty as people might think. Great distances between stars are filled with small numbers of protons and electrons. These particles scatter the radio waves, causing interference effects between different parts of the wave. This causes the radio signals from pulsars to twinkle in intensity as the high-speed pulsars move through the interstellar gas. The same sort of thing happens when light passes through turbulence in the Earth's atmosphere, causing the stars to twinkle. By analyzing these changes, scientists can understand variations in the atmosphere.

In Stinebring's work, a similar process is implemented to analyze radio waves from pulsars to identify and study the interstellar medium. The radio wave intensity data collected from pulsars is transformed by computers into a dynamic spectrum, a graph that plots spectra over a time period of about an hour. Using these, the variations caused by the interstellar medium can be analyzed.

When this information is plotted over time and examined carefully, the interstellar medium can be seen, just like air on earth, to vary in content from place to place and to move around in ways similar to racing jet streams and swirling fog.

Stinebring and the students are currently investigating a mysterious new finding, what they call "wisps," a phenomenon that hadn't been seen before the group's most recent trip to Puerto Rico. "It's an exciting moment in any scientific project when you know you've got something and you don't understand what it is," Stinebring said.

The team is now building models of the interstellar medium and its scattering properties. By comparing the analyses of the simulated models with actual data, Oberlin's pulsar researchers hope to identify what is causing the strange wisps in their data.

When Becker stations herself at the radiotelescope's computer, her work is not solely to administer the telescope. On a typical night the entire group meets at the observatory from 11 p.m. to 4 a.m. Observations can yield around 5 megabytes of data per second, and with studies involving over 70 hours total observing time, the amount of information gathered into computer memory can rival the amount of raw information held in 2,000 compact discs.

Arecibo's telescope has been fixed on a gas cloud for hours by the time Becker arrives, and now she must use a catalogue to find the coordinates of the first pulsar being observed. The telescope's tracking system will automatically follow the neutron star across the night sky for as long as it is in view, with almost pinpoint accuracy. Along with managing the recording computer, Becker will work with the team on other aspects of the research. "There are several things we can do," says Espinoza. "Dan talks with us about his ideas, and we throw out our own and discuss them, or we work on coding programs to analyze the data." He continues with a grin, "Sometimes if we get really bored we play a little Parcheesi."

Stinebring is still being aided by undergraduate research students like Becker, Espinoza, and Smith, who work on the analysis of the data from Winter Term and offer a fresh perspective on his continuing work uncovering the secrets of the cosmos. With further help from his students, Stinebring hopes to discover more about the enigmatic wisps in the data from pulsars.

Jimmy Morris is a junior neuroscience and
philosophy major.
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