From: LARRY KLAES (ljk4_at_msn.com)
Date: Tue Dec 30 2003 - 08:00:06 PST
Astronomy's New Grail: The $1 Billion Telescope
December 30, 2003
By DENNIS OVERBYE
In the quest for some understanding of our twinkling
existence, astronomers have built ever larger telescopes
capable of catching and pooling the rare light of remote
stars and galaxies.
Over the decades the torch of awe has been passed from
mountaintop to mountaintop, from Mount Wilson, from where
the expansion of the universe was discovered, to Palomar,
home of the famous 200-inch reflector, which reigned
supreme for almost half a century, to the cinder cones of
Mauna Kea in Hawaii, where the twin 400-inch-diameter Keck
Telescopes lord it over 13 others.
And even to space, where the Hubble Space Telescope is a
peerless time machine.
Now the torch may be passed again.
Emboldened by the
advances of the last two decades, groups of universities,
observatories, nations and other research organizations are
pondering plans for radical new telescopes that will dwarf
even the giants on Mauna Kea and reach even farther into
space and further back in time.
The proposals sport Brobdingnagian names like the
California Extremely Large Telescope, or CELT; Giant
Magellan; or the Overwhelming Large Telescope, OWL, a
100-meter-diameter behemoth being contemplated by a
collaboration of European nations. And their proponents
promise appropriately outsized scientific results.
The new telescopes, they say, will be able to deliver
images sharper than the Hubble's, while gathering much more
light, bringing into focus the blobs of primeval stars and
gas from which galaxies were assembling themselves 10
billion years ago, or glimpses of planets around distant
stars.
"With such a telescope you can for the first time really
trace the connections between the first seconds of the Big
Bang and the formation of life in the universe," said Dr.
Rolf-Peter Kudritzki, director of the Institute for
Astronomy at the University of Hawaii.
Astronomers say such a telescope will be needed to follow
up and investigate the discoveries of the James Webb Space
Telescope, scheduled for a 2011 launching, and the Atacama
Large Millimeter Array, a radio telescope being built by
the United States and Europe in Chile. In a report
published in 2000, a committee of the National Academy of
Sciences ranked a 30-meter telescope first on a wish list
of new instruments for the coming decade.
But such a telescope also comes with a Brobdingnagian price
tag - roughly a billion dollars to build, equip and operate
for 20 years. That is more than the most recent generation
of large telescopes cost altogether, according to a survey
in Physics Today.
"We are really going to have a hard time building even one
of these," said Dr. Richard Ellis, an astronomer at the
California Institute of Technology, and one of the leaders
of the effort to build the California telescope. Paying for
such a telescope will require a merger of private and
public sources of financing that is rare in astronomy, he
said. Many large ground-based innovative telescopes in the
United States, like Palomar and the Kecks have been built
by private observatories and universities - not the
taxpayer.
Dr. Ellis and his colleagues at Caltech and the University
of California working on the California telescope have
taken the first steps into this new era. This year the
Associated Universities for Research in Astronomy, or AURA,
agreed to join the California effort, which was renamed the
30-Meter Telescope. Subsequently the Gordon and Betty Moore
Foundation granted Caltech and California $17.5 million
each to help pay the cost of designing the telescope. AURA,
which has no money of its own, has applied to the National
Science Foundation for its share of the design cost.
But the 30-Meter Telescope has competitors, in particular
the Giant Magellan, an effort led by the Carnegie
Observatories in Pasadena, Calif., to build a 20-meter
telescope in Chile.
AURA is a consortium of 36 educational and other
institutions, which operates a network of national
observatories for American astronomers. In an interview,
the consortium president, Dr. William Smith, said it was
important to move ahead in order to have a telescope by the
time the Webb telescope was launched.
But the consortium's move to join the California effort
dismayed some of its members, some of them involved in
rival projects. They say that it is too soon to know yet
what is involved in building a giant telescope or what is
at stake scientifically in choosing one design over
another.
In a letter to the National Science Foundation, 18
astronomers said in November that the agreement between
AURA and CELT "may violate the principle of open
competition." They included Dr. Peter Strittmatter,
director of the University of Arizona's Steward
Observatory; Dr. Irwin Shapiro, director of the
Harvard-Smithsonian Center for Astrophysics; and Dr. Wendy
Freedman, director of the Carnegie Obseratories. They urged
the science foundation to hold an open competition to
develop the best strategy for a giant telescope.
Dr. Michael Turner, the foundation's assistant director for
mathematics and physical sciences, said all options were
still open.
In statements and at meetings recently, he and Dr. Wayne
Van Citters, director of astronomical sciences at the
science foundation, have been circumspect, emphasizing the
need for strategic planning before locking in a specific
design. "The science that a Really Big Telescope can do has
everyone excited," Dr. Turner said in an e-mail message.
"We just have to figure out the best way to get there."
The road once ended at Palomar.
Palomar's Hale reflector,
finished in 1948, was long considered the limit for
ground-based telescopes. Bigger mirrors would just be too
heavy.
But in the 1990's, technological advances made it possible
to build thin, lightweight mirrors as large as 8 meters
(about 26 feet) in diameter that relied on computer
adjusted supports to keep the mirrors from sagging under
their own weight.
The largest of the new breed were the Kecks, built by
Caltech and California on Mauna Kea. Instead of being
monolithic slabs of glass, their 10-meter-diameter mirrors
are composed of 36 small hexagons warped and fitted
together. The design was the brainchild of Dr. Jerry
Nelson, a former particle physicist at the University of
California at Santa Cruz.
The first Keck went into operation in 1993. By the end of
the decade Dr. Ellis and his colleagues had already begun
to study how to scale up the Keck idea. Last year they
published a 300-page "conceptual design" for a 30-meter
telescope with a mirror made of some thousand hexagons.
The new Moore Foundation grant, he said, will enable the
California group to refine their design and study the
trade-offs between size, cost and performance of a
telescope.
In the meantime, they have also begun testing sites for the
telescope in Chile; Baja, Mexico; and Mauna Kea in Hawaii.
Only when the design is finished, will the 30-Meter
partners, which Dr. Ellis hopes will soon include the
Association of Canadian Universities for Research in
Astronomy, or Acura, be able to decide whether to proceed
with building the telescope and with raising the serious
money it will require.
With no "hiccups," Dr. Ellis said, the telescope could be
ready in 2012.
While the California telescope will consist of many small
pieces, the 20-meter Giant Magellan is to have only a few
very large ones. Its main mirror will have only six
circular segments surrounding a central one.
The project grew out of the twin 6.5-meter Magellan
telescopes that have recently been built at Carnegie's Las
Campanas Observatory in Chile by a partnership that
includes the Universities of Michigan and Arizona, the
Harvard-Smithsonian Center for Astrophysics, and the
Massachusetts Institute of Technology, as well as Carnegie.
The plan capitalizes on the expertise of Dr. Roger Angel
and his colleagues at the Optical Sciences Center at the
University of Arizona, who have mastered the art of casting
giant mirror blanks in a rotating furnace and then
polishing them into shape. Each of the seven mirror
segments is to be 8.4 meters in diameter, which is the
biggest size his furnace can handle.
The telescope could be ready by 2015, if all goes well, the
Magellan partners say.
Dr. Freedman, Carnegie's director, said she was optimistic
that there would be resources and room on the planet for
both the 30-Meter and the Giant Magellan, and that they
could complement each other.
"We're all moving forward," she said after a recent meeting
on telescopes at the National Academy of Sciences in
Irvine, Calif. "We will succeed because the science is
exciting."
Looming over these and other efforts is the prospect of a
European giant.
That is the 100-meter Overwhelmingly Large Telescope
contemplated by the European Southern Observatory, a
multinational consortium that operates the world's largest
array, the Very Large Telescope, on Cerro Paranal in Chile.
Dr. Robert Gilmozzi, an astronomer at the European Southern
Observatory, said 100 meters was the minimum size needed to
peruse Earth-like planets around nearby stars for signs of
life.
The mirror for the proposed telescope has a novel spherical
design that will allow it to be enlarged, or built in
stages, said Dr. Guy Monnet, an astronomer at the European
Southern Observatory and the project manager for OWL.
This means, Dr. Monnet said, that every segment of the
primary mirror will be identical, simplifying the
construction. It also means that the the European Southern
astronomers can build a 60-meter telescope and see if it
works, and then expand the mirror by filling out the sphere
with more segments to make a 100-meter telescope. Such a
telescope will be more likely if Americans participate, he
added.
In order to realize their full potential the new telescopes
will have to make maximum use of a new technology that
undoes the blurring effects of the atmosphere.
In principle the resolving power of a telescope depends on
its diameter - a bigger one can see finer detail - but in
practice atmospheric turbulence, the same effect that makes
stars appear to twinkle, blurs the stars and erases fine
detail. This is why the Hubble, even though it is not
large, only about 2.4 meters (96 inches), compared with the
new giants on the ground, can do breathtaking work.
Lately astronomers have begun to learn how to tune out some
of the blurring by monitoring the image of a bright star
near the target of observation and continually adjusting a
mirror inside the telescope. But these so-called "adaptive
optics" systems have been added after the fact to existing
telescopes.
The new big telescopes will be the first telescopes to have
adaptive optics built in from the start, Dr. Ellis said.
What can you see with such a telescope?
Extraterrestrial
planets are on the top of many astronomers' lists.
In the last decade more than 100 planets have been detected
around nearby stars by their gravitational effects. These
have all been very massive objects, at least as big as
Jupiter, but the discoveries have fueled hopes that
full-fledged systems with planets more like Earth, possible
abodes of life, may eventually be found.
A giant mirror that could focus starlight into the smallest
tiny point would be particularly well-suited to detecting
planets. Masking out the bright star might bring the much
fainter light of a planet otherwise lost in the glare.
Most of these would be the Jupiter-size planets, but Dr.
Angel said 20- or 30-meter telescopes could be on the
threshold of being able to detect Earth-like planets. A
100-meter telescope, with another tenfold increase in
light-gathering power and even sharper images, he said,
would be "extremely powerful." It would allow spectroscopy
of Earth-like planets, he said, allowing astronomers to
examine its atmosphere and perhaps rudimentary signs of
life.
At the other end of creation, a really big telescope will
be able to study what happened about 11 billion or 12
billion years ago when the universe was undergoing a rush
of construction. Clouds of gas and dust collapsed and lit
up as stars, which in turn began to transform the universe
from primordial hydrogen and helium into the rich mix of
elements like carbon and oxygen that have seeded life and
wonder today. Meanwhile, clusters of stars were condensing
into the first gawky-looking galaxies, ancestors of the
milky spirals and bulging smooth clouds that now rule
space.
But, Dr. Patrick McCarthy of Carnegie explained, "a large
telescope will be able to see all the bits and pieces that
coalesce into galaxies. That's where the physics is."
http://www.nytimes.com/2003/12/30/science/space/30SCOP.html?ex=1073798878&ei=1&en=79d3298e3333595d
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