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Just days before nations around the world were set to
begin a coordinated global research campaign called the
International Polar Year (IPY); scientists at the South
Pole aimed a massive new telescope at Jupiter and successfully
collected the instrument's first test observations.
Soon, a far more distant quarry will enter the South
Pole telescope's (SPT) sights, as a team of researchers
from nine institutions tackles fundamental mysteries of
modern cosmology and the nature of the universe: What,
for example, is dark energy, the force that dominates
the universe?
The $19.2 million telescope is funded primarily by the
National Science Foundation (NSF), with additional support
from the Kavli Foundation of Oxnard, Calif., and the Gordon
and Betty Moore Foundation of San Francisco.
"The telescope, camera and optics are all working
as designed," said John Carlstrom, the S. Chandrasekhar
distinguished service professor in astronomy and astrophysics
at the University of Chicago, who heads the SPT team that
tested the scope on Feb. 26. "SPT's first light is
a major milestone for the project and a fitting conclusion
to a remarkably productive summer at the South Pole station.
We now look forward to fully characterizing the instrument
and beginning cosmological observations."
"First light" is the scientific term for the
time when a telescope becomes operational.
The telescope stands 75 feet (22.8 meters) tall, measures
33 feet (10 meters) across and weighs 280 tons (254 metric
tons). It was assembled in Kilgore, Texas, then taken
apart, shipped across the Pacific Ocean to New Zealand,
and flown from there to the South Pole. Since November,
the SPT team under the guidance of project manager Steve
Padin has worked furiously to reassemble and deploy the
telescope.
As with any construction project at the Earth southern
extremity, SPT was supported by a long and complex logistical
chain stretching around the globe. All cargo to the South
Pole is delivered by ski-equipped LC-130 aircraft, and
the components must be able to be broken down to fit into
the aircraft cargo bay. Flown by the N.Y. Air National
Guard, the aircraft are elements of Operation Deep Freeze,
the military support arm of the U.S. Antarctic Program,
which also includes Air Force cargo jets and U.S. Coast
Guard icebreakers, Navy cargo handlers and many other
logistical and personnel assets.
Raytheon Polar Services Co, of Centennial, Colo. is NSF's
logistics contractor in Antarctica. RPSC personnel played
a variety of essential roles in the successful completion
of the SPT project, NSF officials noted.
Astrophysicists know that the universe has been expanding
since the Big Bang occurred 13.8 billion years ago. In
the late 1990s, astronomers using exploding stars as cosmic
tape measures discovered that the expansion of the universe
is accelerating. This led them to the idea that dark energy
pushes the universe apart, overwhelming gravity, the attractive
force exerted by all matter in the universe.
"We would like to know what makes the universe evolve,"
said Stephan Meyer, professor in Astronomy & Astrophysics
at the University of Chicago.
An Important Anniversary and a Historic Achievement
SPT's first views occurred almost exactly 50 years after
a team of 18 men spent the first winter in history at
the South Pole as part of the 1956-1957 International
Geophysical Year (IGY). They occurred just days before
nations around the globe launched the International Polar
Year 2007-2008, the first such global research campaign
since IGY. The U.S. opening ceremony for IPY was held
today at the National Academies of Sciences in Washington
D.C.
Under the joint leadership of scientists Paul Siple and
Navy Lt. John Tuck, 18 men were first to spend the winter
at the pole in a station the U.S. Navy built in the austral
summer of 1956-1957, using cargo dropped by U.S. Air Force
planes. Siple, Tuck and the 16 other "winterovers"
were also the first people in history to witness sunset
and sunrise at the South Pole, events that are separated
in Antarctica by six months of darkness and frigid cold.
On Sept. 18, 1957, in the depths of the austral winter,
temperature at the station dropped to -107 degrees Fahrenheit
(-77.2 degrees Celsius), the coldest temperature recorded
on Earth at the time.
"We were like men who had been fired off in rockets
to take up life on another planet. We were in a lifeless
and almost featureless world. However snug and comfortable
we might make ourselves, we could not escape from our
isolation," wrote Siple in his memoir, Living at
the Pole. "We were now face to face with raw nature
so grim and stark, that our lives could be snuffed out
in a matter of minutes. Every day would bring us new problems
to solve and our ingenuity would be taxed over and over
again. And all this to carry out a somewhat difficult
fragment of the worldwide scientific program of the International
Geophysical Year."
The men laid the foundation for the scientific legacy
that continues into the 21st Century, as NSF completes
construction of the third permanent station at the South
Pole.
The South Pole: A Premier Observatory
Astronomers work at the South Pole to take advantage
of excellent viewing conditions. Cold, dry Antarctica
will allow SPT to more easily detect the cosmic microwave
background (CMB) radiation, the afterglow of the big bang,
with minimal interference from water vapor. On the electromagnetic
spectrum, the CMB falls somewhere between heat radiation
and radio waves.
The CMB is largely uniform, but it contains tiny ripples
of varying density and temperature. These ripples reflect
the seeds that, through gravitational attraction, grew
into the galaxies and galaxy clusters visible to astronomers
today. The SPT's first key science project will be to
study small variations in the CMB to determine if dark
energy began to affect the formation of galaxy clusters
by fighting against gravity over the past few billion
years.
Galaxy clusters are groups of galaxies, the largest celestial
bodies that gravity can hold together. "Our galaxy,
the Milky Way, is in one of these clusters," Meyer
said. "And these clusters of galaxies actually change
with time."
The CMB allows astronomers to take snapshots of the infant
universe, when it was only 400,000 years old. No stars
or galaxies had yet formed. If dark energy changed the
way the universe expanded, it would have left its "fingerprints"
in the way it forced galaxies apart over the deep history
of time. Different causes would produce a different pattern
in the formation of galaxy clusters.
According to one idea, dark energy could be Albert Einstein's
cosmological constant: a steady force of nature operating
at all times and in all places. Einstein introduced the
cosmological constant into his theory of general relativity
to accommodate a stationary universe, the dominant idea
of the day. If Einstein's idea is correct, scientists
will find that dark energy was much less influential in
the universe 5 billion years ago than it is today.
"Clusters weren't around in the early universe.
They took a long time to evolve," Carlstrom said.
Another version of the dark energy theory, called quintessence,
suggests a force that varies in time and space. Some scientists
even suggest there is no dark energy at all, and that
gravity merely breaks down on vast intergalactic scales.
To pinpoint when dark energy became important, SPT will
use a phenomenon called the Sunyaev-Zeldovich effect,
which distorts the CMB as it passes through the hot gas
of intervening galaxy clusters. As the microwaves interact
with gas in the clusters, some of the microwaves get kicked
into a higher frequency. SPT will measure the slight temperature
difference associated with the frequency change and produce
an image of the gas in the cluster.
SPT can scan large regions of the sky quickly. Scientists
expect it to detect thousands, or even tens of thousands,
of galaxy clusters within a few years. "To get a
meaningful constraint on dark energy through measuring
galaxy clusters, you need something like this South Pole
Telescope," Carlstrom said. "The cluster SZ
[Sunyaev-Zeldovich] signals cover small patches in the
sky relative to the intrinsic variations in the cosmic
microwave background. To get the necessary resolution,
you need a big telescope. Now we have one."
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National
Science Foundation
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