University of Vermont

The College of Arts and Sciences

Department of Physics

To the Cosmic Lighthouse

Pulsars: some are 10 miles wide and heavier than the sun. Undergraduate researchers Isaac Backus and Isabel Kloumann are helping to draw a portrait of the

And you thought the remote for your TV was tricky? Isabel Kloumann and Isaac Backus, both undergraduate students, sit in a cinderblock office on the fifth floor in the Cook Building entering coordinates into an iMac computer. One-thousand-eight-hundred-forty-seven miles away -- in a limestone sinkhole on a mountaintop in Arecibo, Puerto Rico -- the world's largest telescope moves to their commands.

"It's like playing a slow video game," says Kloumann. Far stranger are the objects they are pointing the telescope toward: pulsars many light years away.

Compared to a black hole, a pulsar is a kind of scrawny cousin not quite massive enough to fall into complete light-sucking density. Still, these strange objects are staggeringly dense, holding about a billion tons per cubic centimeter. Imagine a teaspoon of sugar that weighed as much as three thousand Empire State Buildings.

"Pulsars are about the size of Burlington with mass comparable or greater than the sun," says UVM astrophysicist Joanna Rankin, who has employed Kloumann and Backus as independent researchers. "What we're observing this morning are city-sized remnants of medium-massed stars." This observing depends on the Arecibo telescope that Rankin and her students use several times each year through funding from the National Science Foundation. With a reflecting dish a thousand feet across and a colossal cable system to carry the receiver hither and yon overtop, the telescope gathers radio waves pouring in from clouds of cold gas throughout the Milky Way and beyond, like the famed Andromeda galaxy.

But the telescope also records the compact, highly regular, on/off bursts of radio energy that come from pulsars. ("Pulsar" is a contraction of pulsating star.) As these spheres of hyper-dense neutrons spin -- some rotating once every few seconds, some hundreds of times per second -- they shoot out two cones of radio emissions from above their bogglingly powerful magnetic poles.

"It's just like a lighthouse," says Kloumann, "every time it sweeps past, you get a flash." Kloumann has been studying pulsar B1944+17 on her own for the past year. Sometimes it just turns off. And no one is exactly sure why.

"We're looking at these really unusual stars that don't fit the perfect model," she says. "They test the bounds of the theory -- which is what you always should do in science: push the limits of the theory." The students pushed enough to get the attention of professional astronomers. In May 2010, the prestigious astronomy journal, the Monthly Notices of the Royal Astronomical Society published a scientific paper comparing two unusual pulsars -- with Isaac Backus as the lead author; a rare feat for an undergraduate. The journal's referees, "liked it," he says. "The comments were mostly about grammar. Well, with a few other things."

Kloumann -- an Honors College student, Goldwater Scholar, and "one of UVM's stars in physics and mathematics," says Rankin -- also published her study of pulsar B1944+17 in the same journal.

"My freshman year I wanted to be involved in research, so I went and found Joanna," Kloumann says. She found that Joanna Rankin is both a devoted teacher and researcher. Rankin’s work on pulsar “carousels” has helped pioneer a new understanding of how these stars generate radio radiation. This summer, Rankin launched a new project, funded by the National Science Foundation, to see if the hyper-precise timing of pulsar radio bursts can be used to detect one of the most elusive prizes in physics: gravity waves.

"I worked one-on-one with her every week and she would tell me about pulsars for three hours!" Kloumann says. "She's a great mentor. She's given us a lot of freedom and flexibility. And she's there when you need her."

Kloumann, Backus, and graduate student Megan Force have worked closely together, and each has had a chance to travel to Arecibo with Rankin to see the telescope in action. Now, Backus has what he calls the best summer job ever: a three-month stint working at the Arecibo telescope with Rankin's close colleague Dipanjan Mitra, a leading Indian pulsar astronomer.

For her part, Megan Force finds working at Arecibo deeply inspirational. “You feel like Galileo,” she says, “right there next to the machine."