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January 12, 2004 -- The University of Utah and a
group of Japanese and U.S. universities plan to build a $17 million
to $18 million cosmic ray observatory named the Telescope Array
in central Utah’s Millard County. It will try to determine
the mysterious source of the most energetic particles in the universe.
Japan’s government has promised $12 million to build the
observatory. American universities hope to raise another $5 million
to $6 million in U.S. government grants by mid-2005 to enhance
the observatory’s capabilities, says Pierre Sokolsky, professor
and chair of physics at the University of Utah. Construction is
slated to begin this spring, and should be complete by late 2007.
The Telescope Array is distinct from the University of Utah’s
existing $14.4 million High-Resolution Fly’s Eye cosmic
ray observatory at Dugway Proving Ground, and the $50 million
Pierre Auger Project, another kind of cosmic ray observatory proposed
for construction in Millard County, Utah, or in Colorado.
All three projects seek to understand a major puzzle: What incredibly
powerful phenomenon in the universe is hurling ultrahigh-energy
cosmic rays through space?
A Mystery of the Universe
Cosmic rays, discovered in 1912, are subatomic particles: the
nuclei of atoms such as hydrogen, oxygen, carbon, nitrogen or
iron. Medium-energy cosmic rays come from exploding stars, while
the sun and other stars emit even lower-energy cosmic rays.
But the source of ultrahigh-energy cosmic rays is unexplained.
They are 100 million times more energetic than anything produced
by particle smashers on Earth. Scientists theorize they may come
from noisy radio galaxies, supermassive black holes at the centers
of active galaxies, shock waves from colliding galaxies, bizarre
sources such as so-called cosmic strings or even from the decay
of massive particles left over from the “big bang”
that scientists believe formed the universe about 13 billion years
ago.
“Something out there is producing subatomic particles with
energies that a lead brick has when you drop it on your toe,”
Sokolsky says. “Whatever it is, it is the most energetic
mechanism we know of in the universe short of the big bang.”
Physicists around the world hope to find the answer in Utah’s
western desert.
“The vast open land and dark, clear night sky are essential
for the success of our experiment,” says Masaki Fukushima,
a physicist at the University of Tokyo Institute for Cosmic Ray
Research and leader of Japanese scientists working on the Telescope
Array. “We are happy to work with Utah colleagues who pioneered
the study of the tiniest, most energetic particles in the universe
– particles we believe carry the secret of the big bang.”
The Telescope Array will be built in open rangeland west of Delta,
Utah, where high school students and other residents have helped
in preparing the project.
“There’s a feeling of excitement at wanting to uncover
the mysteries of the universe,” says Utah state Rep. Michael
Styler, R-Delta, among government officials in Millard County
who met University of Utah scientists on Jan. 9 to discuss the
Telescope Array and Auger Project. “We are especially happy
to have it in our own backyard.”
The Telescope Array
The Telescope Array is a collaboration by the University of Utah,
University of New Mexico, University of Montana, University of
Tokyo Institute for Cosmic Ray Research, Tokyo Institute of Technology,
Osaka City University, Chiba University, Shibaura Institute of
Technology, KEK (Japan’s High Energy Accelerator Research
Organization), Kinki University, Saitama University and Yamanashi
University. Others may join later, says Kai Martens, assistant
professor of physics at the University of Utah.
The Telescope Array will include two types of devices scattered
over a large area:
-- Three fluorescence detectors – sets of mirrors that detect
faint blue flashes in the night sky caused when cosmic rays hit
atmospheric gas molecules – will be built on three hills:
Black Rock Mesa 13 miles south-southwest of Delta, Long Ridge
30 miles southwest of Delta, and between the Drum and Little Drum
Mountains 25 miles northwest of Delta. The university plans to
lease the sites from Utah’s School and Institutional Trust
Lands Administration, and expects to start construction this spring.
A Central Laser Facility, which will shoot laser beams skyward
to test the mirrors, will be built on leased federal land equidistant
from the three hills.
If the additional $5 million to $6 million can be raised, another
one or two fluorescence detector sites might be added in the future,
Martens says.
-- A “ground array” of 576 scintillation detectors
will be installed in a vast grid on a roughly 18-by-22-mile area
west of Delta, Hinckley and Deseret, sharing the grazing land
with cattle. When a cosmic ray hits atmospheric gases, it causes
a cascade or “air shower” of other subatomic particles
that reach the ground and will be measured by the scintillation
detectors. Each detector will contain a flat plastic plate that
produces a measurable pulse of light when hit by the particles.
Each solar-powered scintillation detector will sit on a 2-foot-tall
stainless steel table measuring 6-by-10-feet wide. Each of the
576 detectors will be three-fourths of a mile from other detectors,
minimizing the visual impact. The University of Utah has started
seeking permits from the federal Bureau of Land Management and
will perform an environmental assessment for 80 percent of the
scintillation detector sites that are on BLM land, and will negotiate
with ranchers and landowners for permission to install the other
20 percent of scintillation detectors on private land, Martens
says.
Roads exist to the three fluorescence detector sites, although
improvements will be needed on some stretches to Black Rock Mesa
and Long Ridge, Martens says. Scientists will use existing roads
and ATVs if necessary to install the scintillation detectors,
which should need maintenance only rarely.
A Brief History of Cosmic Ray Research
The University of Utah is a pioneer in cosmic ray research. After
atmospheric humidity stymied a 1950s effort to observe cosmic
rays from upstate New York, University of Utah physicists built
a prototype in New Mexico in 1976, constructed the Fly’s
Eye at Dugway Proving Ground during 1980-1981, improved it in
1986, and then upgraded it during 1994-1999 and renamed it the
High-Resolution Fly’s Eye. The name comes from the use of
fly-like multifaceted mirrors to observe the sky.
The highest-energy cosmic ray ever detected was measured in 1991
by the Fly’s Eye. It had an energy of 300 billion billion
electron volts (billion twice is correct), and would feel like
a fast-pitched baseball if it could penetrate the atmosphere and
hit a person in the head.
The High-Resolution Fly’s Eye uses two fluorescence detectors
similar to the three that will be built in the Telescope Array.
But research at the High-Resolution Fly’s will end in a
few years because “we have learned as much as we can with
that configuration,” says Sokolsky, who calls the Telescope
Array “a natural next step.”
Operation of the High-Resolution Fly’s Eye has become difficult
– especially for foreign students and faculty – due
to its presence on a military base. For two years after the Sept.
11, 2001, terrorist attacks on the World Trade Center and Pentagon,
the University of Utah had to hire people with security clearances
to enter Dugway and operate the observatory.
Meanwhile, a Japanese cosmic ray observatory named AGASA –
which uses scintillation detectors like those proposed for the
Telescope Array – has operated for 10 years but will be
dismantled next year. Clouds, humidity and air pollution make
more sensitive fluorescence-detector observatories there impractical,
Sokolsky says.
One key goal for the Telescope Array is to determine why the High-Resolution
Fly’s Eye has detected far fewer ultrahigh-energy cosmic
rays than AGASA. It also will seek to explain an apparent shortage
of cosmic rays that are about 100 times less powerful than the
most energetic particles.
In 1996, an international group of physicists proposed building
the Pierre Auger Project: twin $50 million cosmic ray observatories
in Argentina and Utah. (Auger was a physicist who discovered air
showers in 1938.) U.S. science agencies decided to finance the
Argentina observatory first to look for cosmic rays in southern
skies. Construction is underway there, and the first scientific
results are anticipated in 2005, says University of Utah physicist
Paul Sommers.
Scientists at the University of Utah and elsewhere expect to seek
federal funding in 2005 to build the Auger project’s northern
observatory. They hope to begin construction in late 2006. If
it is built in Utah rather than Colorado, 1,657 water tanks would
be installed in a grid pattern south of Delta and west of Fillmore,
covering 1,200 square miles – an area five times larger
than the Telescope Array. The tanks detect blue flashes of Cherenkov
light created when cosmic ray air shower particles hit the water.
If both the Telescope Array and northern Pierre Auger observatory
are built, physicists will be able to measure cosmic rays simultaneously
with three kinds of detectors: fluorescence, scintillation and
Cherenkov. Sokolsky says that will allow them to study cosmic
rays with a wide range of energies – from high to ultrahigh
– to gain a better understanding of their source.
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