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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.
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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