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Astronomie - The Giant Magellan Telescope (GMT) - Update-1

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5.09.2013

World’s Most Advanced Mirror for Giant Telescope Completed
Scientists at the University of Arizona and in California have completed the most challenging large astronomical mirror ever made. The mirror will be part of the 25-meter Giant Magellan Telescope, which will explore planets around other stars and the formation of stars, galaxies and black holes in the early universe.
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The Giant Magellan Telescope, against the southern Milky Way, as it will appear when it's completed.
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Scientists at the University of Arizona and in California have completed the most challenging large astronomical mirror ever made.
For the past several years, a group of optical scientists and engineers working at the UA Steward Observatory Mirror Laboratory underneath the UA’s football stadium have been polishing an 8.4-meter (27 ½ feet) diameter mirror with an unusual, highly asymmetric shape.
By the standards used by optical scientists, the “degree of difficulty” for this mirror is 10 times that of any previous large telescope mirror. The mirror surface matches the desired prescription to a precision of 19 nanometers – so smooth that if it were the size of the continental U.S., the highest mountains would be little more than a half-inch high.
This mirror, and six more like it, will form the heart of the 25-meter Giant Magellan Telescope (GMT), providing more than 380 square meters, or 4,000 square feet, of light-collecting area. The Giant Magellan Telescope will lead a next generation of giant telescopes that will explore planets around other stars and the formation of stars, galaxies and black holes in the early universe.
Buell Jannuzi, director of the UA Steward Observatory and professor of astronomy, said, “Making this first GMT mirror required all the expertise and experience that the University has built up over 25 years of making telescope mirrors and a great deal of innovation to push beyond previous limits in optical fabrication and testing. In achieving this remarkable milestone, the team built and demonstrated all the equipment and techniques that will lead to efficient production of the remaining mirrors for the GMT.”
The mirror was cast at the mirror lab from 20 tons of glass, melted in a rotating furnace until it flowed into a honeycomb mold. Once the glass had cooled and the mold material was removed, scientists at the lab used a series of fine abrasives to polish the mirror, checking its figure regularly using a number of precision optical tests.
The mirror has an unconventional shape because it is part of what ultimately will be a single 25-meter (82 feet) optical surface composed of seven circular segments, each 8.4 meters (27 ½ feet) in diameter.
“We need to be certain the off-axis shape of this mirror, as well as the other six that will be made for GMT, is precisely right, to an accuracy of 1/20 of a wavelength of light,” said Buddy Martin, polishing scientist at the Mirror Lab. “Only then will the seven large mirrors form a single, exquisitely sharp image when they all come together in the telescope in Chile. We have now demonstrated that we can fabricate the mirrors to the required accuracy for the telescope to work as designed.”
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The first of seven mirrors for the Giant Magellan Telescope after removal from the furnace. The back surface of the mirror is shown here during an inspection of the holes used to ventilate the mirror during operation in the telescope. (Photo: Ray Bertram/UA)
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The testing techniques, developed by Jim Burge, professor at the UA College of Optical Sciences, and his team, are a key part of the innovation enabling these giant off-axis mirrors. The second of seven mirrors for the GMT was cast at the mirror lab in January of this year; the third will be cast in August 2013.
The Giant Magellan Telescope will be located on a remote mountaintop in the Chilean Andes where the skies are clear and dark, far from any sources of light pollution. At the Carnegie Institution for Science’s Las Campanas Observatory in northern Chile, earthmovers are completing the removal of 4 million cubic feet of rock to produce a flat platform for the telescope and its supporting buildings. Wendy Freedman, chair of the GMT board, said: “The technical achievements at the UA’s mirror lab and the dedication and commitment of our national and international partners will allow us to open a new window on the universe. An exciting future of discovery awaits us.”
The telescope, slated to begin operations late in the decade, will allow astronomers and students across the U.S. and from around the world to address critical questions in cosmology, astrophysics and planetary science. Matthew Colless, director of the Australian Astronomical Observatory, said, “The Giant Magellan Telescope has the potential to transform how we see the cosmos, and our place in it.”
The GMT partner institutions are the Australian National University, Astronomy Australia Limited, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, The Smithsonian Institution, Texas A&M University, the University of Arizona, the University of Chicago and the University of Texas at Austin.
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The first of seven mirrors for the Giant Magellan Telescope being polished at the UA Steward Observatory Mirror Laboratory. The polishing head, shown center, changes shape to match the curvature of the mirror as it moves across the surface. (Photo: Ray Bertram/UA)
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Dr. Rebecca A. Bernstein named Project Scientist for Giant Magellan Telescope
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The Giant Magellan Telescope Organization announces the appointment of Rebecca A. Bernstein, Ph.D. to the position of GMT Project Scientist. Dr. Bernstein will provide technical and scientific leadership for the design and construction of the Giant Magellan Telescope – a unique optical and infrared instrument with an aperture of 25 meters (80 feet in diameter) intended for basic research in astronomy and astrophysics. Dr. Bernstein completed her BS in physics at Princeton and received a Ph.D. in astrophysics from the California Institute of Technology. She took a prestigious NASA Hubble Postdoctoral Fellowship to the Carnegie Institution for Science where she played a leading role in the development of a high-resolution spectrograph for the 6.5m Clay (Magellan II) Telescope at Carnegie’s Las Campanas Observatory. In 2001 she joined the faculty of the University of Michigan as an Assistant Professor. In 2007 she accepted a position as Professor of Astronomy at the University of California, Santa Cruz. In addition to her role as the GMT Project Scientist, Dr. Bernstein will join the distinguished research faculty at the Observatories of the Carnegie Institution for Science. Dr. Bernstein said of this move, "I think this is a terrific project and I am thrilled to have the opportunity to join GMT."
Dr. Bernstein is known for her fundamental research into extragalactic background light and the chemical enrichment of galaxies. She is also known for her work in the development of state of the art instrumentation for large telescopes. Most recently she has been the optical designer and Principle Investigator for the wide-field, optical spectrograph for the Thirty Meter Telescope project, one of the first generation instruments currently planned for TMT. Dr. Wendy Freedman, Chair of the GMTO Board, said of this appointment, "Dr. Bernstein brings a unique combination of technical excellence and scientific breadth to a critical leadership position within the project."
Concurrent with this appointment, GMTO has appointed Dr. Bruce C. Bigelow to the position of Opto-mechanical Systems Lead. Dr. Bigelow has managed the design and development of large scientific instruments for a wide range of ground- and space-based telescopes, including the TMT project and the Keck and Magellan Telescopes, and has contributed innovative design work to many of those instruments. Dr. Bigelow will lead design and development activities for critical optics and opto-mechanical systems for the GMT.
The GMT scientific mission spans the range from studies of planets orbiting nearby stars to studies of the first-light in the universe a few hundred million years after the big bang. Dr. Patrick McCarthy, the GMT Project Director said, "These two outstanding appointments strengthen our team enormously. The Project Staff are delighted to welcome our new colleagues." The GMT team is completing their design process with the intent to start construction in early 2014. The telescope site in the Chilean Andes at the Las Campanas Observatory has been leveled. The third of seven 8.4-meter primary mirror segments that form the heart of the GMT will be cast in the spinning furnace at the University of Arizona’s Steward Observatory Mirror Lab on August 24, 2013. The first of the segments was completed in November 2012 and the second was cast in January 2012. First light for GMT is expected in 2019 and closeout of the commissioning phase is projected for the 2021-2022 time frame.
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Quelle: GMT
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Update: 8.12.2013
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Giant Magellan Telescope’s Third Mirror Unveiled

Pasadena, Calif. - Dec. 4, 2013 - The Giant Magellan Telescope’s third primary mirror will be unveiled at the University of Arizona’s Steward Observatory Mirror Lab on December 6, 2013. The combined surface area of the three mirrors created to date surpasses that of any existing telescope and will help enable astronomers to peer more deeply into space than ever before once the telescope is completed.

Primary mirrors are the heart of the modern day reflecting telescope. They capture and focus photons coming from space to help construct images of the universe and collect complex spectra. Generally, the larger the surface area of the primary mirrors, the more photons they can capture, leading to better images and improved data. The Giant Magellan Telescope will offer the best image resolution ever seen to explore deep space.

"The Giant Magellan Telescope will be one of the most powerful tools for approaching some of society’s most profound questions: where did we come from, where are we going, and are we alone in the Universe?” said Patrick McCarthy, Giant Magellan Telescope Project Director. “The technology used to design and construct the telescope is breathtaking, but the answers it may provide as to the beginnings of time itself will be staggering."

The first of a new generation of "extremely large telescopes," or "ELTs," the Giant Magellan Telescope will have a mirror array consisting of seven 27-foot- (8.4-meter-) diameter mirror segments. The telescope is anticipated to begin operation in 2020 with four mirror segments completed, making it the largest telescope in the world. When its final stages of construction are complete, it will have ten times the resolution of the Hubble Space Telescope.

Each of the Giant Magellan Telescope’s mirrors is the product of cutting edge technology and processing. Cast in a custom-built rotating furnace that reaches approximately 2,100°F, they each weigh about 20 tons, yet their internal architecture features an intricate honeycomb pattern that allows them to regulate temperature quickly while remaining extremely rigid. Additionally, each mirror is meticulously polished and evaluated to create a surface that is so smooth that no imperfection is taller or deeper than a twentieth of a wavelength of light—one millionth of an inch. Details of the mirror making process can be seen here.

"The mirror surface is so smooth that if we took one 27 foot mirror and spread it out from coast to coast across the U.S., the height of the tallest mountain on that mirror would be only half an inch – an engineering masterpiece," said Wendy Freedman, Director of the Observatories of the Carnegie Institution for Science and Chair of the Board of Directors for the Giant Magellan Telescope Organization.

The third mirror--dubbed "GMT3"--was cast in August at the Steward Observatory Mirror Lab, the only facility in the world capable of creating mirrors of this size. The University of Arizona is one of ten international partners who are collaborating to build the Giant Magellan Telescope. Collectively, the partners represent more than 1,000 years of astronomy experience. Their accomplishments include the construction of past record- breaking telescopes and the cultivation of some of astronomy’s most brilliant minds.

"Once fully operational, this telescope will provide discoveries for the next 50 years," added Freedman. "These huge mirrors are critical steps along the path to deployment, and then we can open the floodgates of research."

The Giant Magellan Telescope will be constructed at the Las Campanas Observatory in the Atacama Desert in northern Chile, where it will be able to work synergistically with other astronomical instruments and surveys. The program to fund and build the Giant Magellan Telescope is a global first, targeting a total of $1 billion from mostly private, philanthropic donors, with some contributions coming from government agencies around the world.

The Giant Magellan Telescope will be the first of its kind and the largest privately led telescope initiative in history, igniting a new era of discovery and unlocking answers to some of the most fundamental questions of humanity, including whether or not life exists on other planets and how the universe began. Astronomers will also use it to better understand how planets and galaxies form and to help find answers to the mysteries of dark matter and dark energy.

The event is supported by the University of Arizona’s Steward Observatory and College of Science. The Giant Magellan Telescope Organization (GMTO) manages the GMT project on behalf of its international partners: Astronomy Australia Ltd., The Australian National University, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, the Smithsonian Institution, Texas A&M University, the University of Arizona, the University of Chicago, and the University of Texas at Austin.
Quelle: GMT
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Update: 20.02.2014
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Giant Magellan Telescope Looking Toward Construction

Pasadena, CA–The international consortium of the Giant Magellan Telescope (GMT) project has passed two major reviews and is positioned to enter the construction phase. When completed, the 25-meter GMT will have more than six times the collecting area of the largest telescopes today and ten times the resolution of the Hubble Space Telescope. Scientists will explore distant and potentially habitable planets around other stars, the universe in the first billion years after the Big Bang, and the mysteries of dark matter, dark energy and massive black holes.
The Carnegie Institution for Science is a founding partner of the Giant Magellan Telescope Organization (GMTO).* During a week-long review in mid-January, an international panel of experts examined the telescope’s design, its complex optical systems and precision scientific instruments. The panel concluded that the project meets the technical readiness required to proceed to construction. Immediately following the design review, a team of construction experts scrutinized the project’s cost estimate and management plan. Both review panels endorsed the team’s cost estimate and their approach to managing construction of the telescope atop a remote mountain peak in the Chilean Andes.
Carnegie president Richard A. Meserve remarked, “This is a major milestone for the project, for astronomy, and for the human quest for knowledge. I congratulate Wendy Freedman, director of the Carnegie Observatories and chair of the GMTO board, for her steadfast commitment to this far-reaching venture.”
“These reviews are critical milestones required by the GMTO board to proceed with the construction phase,” said Freedman. “I am delighted with the very positive results of the design and the cost reviews. Along with the successful casting of the first three 8.4-meter primary mirrors and the leveling of the mountaintop in Chile, each step brings us closer to construction.”
Board members representing the partner research institutions that make up the GMT consortium will meet mid-year to review the construction plan.
Though the project has not formally entered the construction phase, the long timelines required to fabricate some elements of the telescope have required early activity. Production of three of the telescope’s seven primary mirror segments is underway; work on the fourth mirror will begin in January of 2015. Early science operations on the GMT are planned to begin in 2020. It will be located at Carnegie’s Las Campanas Observatory in Chile where the mountaintop construction site has already been leveled.
Quelle: Carnegie Institution of Washington
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Update: 8.03.2014
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UT Austin to Become Partner in Construction of World’s Largest Telescope

AUSTIN, Texas — The University of Texas System Board of Regents Friday authorized UT Austin to spend $50 million in research reserves to participate in building the Giant Magellan Telescope, which will be the world’s largest telescope when it’s completed in 2020. The project will give students, researchers and faculty the opportunity to make groundbreaking discoveries in astronomy.

The Giant Magellan Telescope, or GMT, will be built in Chile, in the foothills of the Andes, because the extremely dry climate is optimal for providing the sharpest images.

The telescope’s seven mirrors will comprise about 3,900 square feet, which is about the size of a basketball court. Compared to the Hobby-Eberly Telescope at the UT Austin’s McDonald Observatory in west Texas, the GMT will have six times the light-gathering power and the ability to produce images 10 times sharper.

The total cost of the telescope is expected to be about $1.05 billion. UT Austin has set a goal to contribute 10 percent of the construction costs, or roughly $100 million.

In addition to UT Austin, founding partners in the telescope project include Astronomy Australia Ltd., the Australian National University, the Carnegie Institution for Science, Harvard University, the Korea Astronomy and Space Science Institute, the Smithsonian Institution, Texas A&M University, the University of Arizona and the University of Chicago.

“Being a charter investor in this remarkable scientific tool will benefit our students, our faculty and the whole university,” UT Austin President Bill Powers said. “Not only will we be helping to answer the most basic questions about our universe, but our involvement will underscore our status as a top world university. This is the leading edge of science, and it is where Texas must be.”

UT System Chancellor Francisco G. Cigarroa, M.D., said UT Austin will be one of few U.S. universities with access to the world’s largest telescope.

“This will help position UT Austin to become the top public research university in the country,” Cigarroa said. “In the 1500s, Ferdinand Magellan organized the first expedition to circumnavigate the globe. Now, UT Austin and the Giant Magellan Telescope project are continuing that journey to better understand the world we live in.”

For example, the Giant Magellan Telescope will be able to take images of previously undiscovered planets and determine if they are habitable, said David Lambert, director of the McDonald Observatory.

“If we succeed, I think the discovery of a series of habitable planets would be a landmark in human history,” he said.

UT Austin’s financial contribution guarantees annual access to the telescope. The university is hoping to raise an additional $50 million through fundraising.

"Not only does this funding put us over half of the way toward our goal, it shows the university's vital commitment to the astronomy program,” Lambert said. “It also sends a strong signal to the young researchers and faculty that we'd like to recruit over the next few years that the University of Texas at Austin intends to continue being a major player in optical astronomy far into the future."

Quelle; UT Austin

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Update: 4.06.2015

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Magellan super-scope gets green light for construction

Construction of the Giant Magellan Telescope has been given the go-ahead.
One of the largest optical observing systems ever conceived, the GMT will sit atop Cerro Las Campanas in Chile.
With its 24.5m-wide primary mirror system, astronomers should be able to see the first objects to emit light in the Universe, investigate dark energy and dark matter, and identify potentially habitable planets.
The GMT's international partners have all approved the $500m assembly phase.
Contracts against this money can now be awarded to suppliers.
Flattened mountain
The mountain ridge of Las Campanas itself, which is in the Atacama Desert, is ready to receive the observatory's components.
Two-and-a-half-thousand cubic metres of rock have been removed from its southern end to create a flat surface the size of four football fields. A road is in place to take all the elements to the summit when they become available.
Chief among these, of course, will be the seven 8.4m mirrors that comprise the GMT's primary reflecting surface.
Three are already at various stages of production (one is actually finished); the other four will begin their manufacture very soon.
"We expect in late 2021, possibly in early 2022, we will put three or four primary mirrors in the telescope, start doing some engineering, start doing some astronomy, and by that point we will have the largest (optical) telescope on the planet by a good margin," said GMT director, Pat McCarthy.
"We'll then slowly integrate the rest of the mirrors as they come along so that by 2024 or 2025, we should have all seven mirrors in the telescope," he told BBC News.
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The GMT is one of three ground-based optical super-scopes planned for the next decade.
The other two are the European Extremely Large Telescope (E-ELT), also in Chile, and the Thirty Meter Telescope (TMT), to be sited in Hawaii.
Construction of the latter has been in the news of late because of a dispute with Native Hawaiian activists, who say the installation on Mauna Kea volcano is a desecration of sacred land.
With primary diameters of 39m and 30m respectively, the E-ELT and the TMT will be bigger than the GMT at completion. They will also have a very different architecture in that their big reflecting surfaces will be made up of many hundreds of smaller mirror segments.
The designers of the GMT, on the other hand, think their decision to go for just seven large units will pay dividends in certain types of observations.
Sharper than Hubble
"We think there is great advantage in having as much of your collecting area as possible in a contiguous, uninterrupted optical surface," explained Dr McCarthy, a researcher from Carnegie Observatories.
"This will limit the number of phase jumps that you have. So, for high-contrast applications, where you're using adaptive optics, imaging planets around nearby stars - we feel that having this much of the telescope's aperture as coherent pieces of glass will help us when we try to achieve that very high contrast."
The "adaptive optics" of which Dr McCarthy speaks is really now a must-have in modern astronomy.
Such systems counter the "twinkling" of stars and other astrophysical phenomena caused by their light passing through Earth's turbulent atmosphere.
By manipulating flexible secondary mirrors, it is possible to subtract this effect based on information gleaned from artificial stars projected on to the sky by lasers.
This approach, together with its great aperture size, should enable the GMT to capture images that are 10 times sharper than those from the Hubble Space Telescope.
Quelle: BBC

Construction to Begin on Largest Telescope 

Resting on an air-cushioned cart, one of the GMT's seven mirrors undergoes optical testing in the UA's Richard F. Caris Mirror Lab. (Photo: Ray Bertram)

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Collaborators secure more than $500 million for the historic project to build the Giant Magellan Telescope, with seven of its mirrors produced at the UA.

The Giant Magellan Telescope Organization announced Wednesday that its 11 international partners have committed more than $500 million to begin construction of the first of a new generation of extremely large telescopes. Once it is built, the Giant Magellan Telescope is poised to be the largest optical telescope in the world.
The telescope’s seven mirrors, produced at the University of Arizona, will focus more than six times the amount of light of the current largest optical telescopes into images up to 10 times sharper than those of the Hubble Space Telescope. The GMT will enable astronomers to look deeper into space and farther back in time than ever before.
The GMT aims to discover Earth-like planets around nearby stars and the tiny distortions that black holes cause in the light from distant stars and galaxies. It will reveal the faintest objects ever seen in space, including extremely distant and ancient galaxies whose light has been travelling to Earth since shortly after the Big Bang, 13.8 billion years ago. The telescope will be built at the Carnegie Institution for Science’s Las Campanas Observatory in the dry, clear air of Chile’s Atacama Desert, in a dome 22 stories high. It is expected to see first light in 2021 and be fully operational by 2024.
"The GMT will herald the beginning of a new era in astronomy," said Wendy Freedman, chair of the Giant Magellan Telescope Organization board of directors and professor of astronomy and astrophysics at the University of Chicago. "It will reveal the first objects to emit light in the universe, explore the mysteries of dark energy and dark matter, and identify potentially habitable planets in the Earth’s galactic neighborhood. The decision by the GMTO partner institutions to start construction is a crucial milestone on our journey to making these amazing discoveries using state-of-the-art science, technology and engineering.”
The telescope’s light-gathering surface, spanning 82 feet, will be comprised of seven separate 8.4-meter (27-foot) diameter segments. Each mirror segment weighs 17 tons and takes one year to cast and cool, followed by more than three years of surface generation and meticulous polishing at the Richard F. Caris Mirror Lab of the UA's Steward Observatory. Funding for the project comes from the partner institutions, governments and private donors.
"The University of Arizona is very proud to be part of the international partnership building the GMT, and our faculty and students are looking forward to using the GMT to explore the universe in new and exciting ways," said Buell Jannuzi, director of Steward Observatory and head of the UA's Department of Astronomy.
GMTO President Edward Moses said, "The GMT is a global scientific collaboration, with institutional partners in Australia, Brazil, Korea, the United States and in its host nation, Chile. The construction approval means work will begin on the telescope’s core structure and the scientific instruments that lie at the heart of this $1 billion project. Early preparation for construction has included groundwork at the mountaintop site at Las Campanas in northern Chile, and initial fabrication of the telescope’s seven enormous primary mirror segments."
Professor Matthew Colless, vice chair of the board of directors and director of the Research School of Astronomy and Astrophysics at the Australian National University, said the construction approval was an exciting moment for astronomy.
"Plans that have existed only in two dimensions or as computer models are about to become a three-dimensional reality in glass, steel and high-tech semiconductor and composite materials," Colless said. "The GMT will provide astronomers and astrophysicists with the opportunity to truly transform our view of the universe and our place within it."
The Giant Magellan Telescope Organization manages the GMT project on behalf of its international partners: Astronomy Australia Ltd., the Australian National University, the Carnegie Institution for Science, Fundação de Amparo à Pesquisa do Estado de São Paulo, Harvard University, the Korea Astronomy and Space Science Institute, the Smithsonian Institution, Texas A&M University, the University of Arizona, the University of Chicago and the University of Texas, Austin.
Quelle: The University of Arizona

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Update: 2.12.2015

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A new giant telescope aims to answer the question: Is there anybody out there?

LIMA, Peru — On a remote hilltop 8,000 feet above sea level in Chile’s Atacama Desert, scientists hope to answer one of the most fundamental questions facing humankind: Is there life elsewhere in the universe?
That’s one of various goals of the Giant Magellan Telescope, or GMT, now in the early stages of construction and scheduled to start scanning outer space in 2021. Once it does, it's expected to offer views of the farthest depths of the universe ever achieved.
With seven curved mirrors giving it a record optical surface 80 feet in diameter, the GMT will have the sharpest images of any telescope ever built. Its resolution will be 10 times better than that of the Hubble Space Telescope.
That will allow scientists to peer not just to the edge of the universe billions of light years away, but also effectively back in time.
In particular, they hope to focus on the period between 50 billion and 100 billion years after the Big Bang. That’s the period when most stars, galaxies and black holes began to form — and when the conditions for the start of life on many other planets were most optimal.
But if that sounds challenging, then bear in mind that the telescope will be seeking out planets in the “habitable zone” similar to ours, with water, moderate temperature fluctuations and a stable atmosphere. In most cases, those planets are outshone billions of times by the neighboring stars around which they orbit.
“Are we alone? That is a fundamental question that every human being is interested in answering,” says Patrick McCarthy, GMT president and a Carnegie astronomer. “We are very lucky to be living at a time when we can begin attempting to answer it.”
“Even when I was a graduate student, in the ’80s and ’90s, there was a certain degree of pessimism. It was that we are either on our own in this universe, or else extremely rare. That has changed very quickly, with various breakthroughs in the science,” he adds. 
Even if just one star in a billion has a planet in the habitable zone, McCarthy says that still leads to significant odds of life developing elsewhere in the universe. There are 100 billion stars in the Milky Way, one of just 100 billion galaxies. He says there could be as many as “10 to the 15th” habitable planets out there.
If the telescope is successful in picking up the first signs of extraterrestrial life — even if it's just a few microbes rather than “intelligent” beings — it would be one of the most sensational discoveries in the history of science.
It would also silence the doubters, who still remain a significant minority of experts on the subject.
The consortium behind the GMT is made up of a host of colleges and research centers from Australia, Brazil, Korea and the United States, including Harvard, Texas A&M, the Universities of Arizona, Chicago and Texas at Austin, as well as the Carnegie and Smithsonian Institutions. So far, they have already raised $500 million of the project’s total $1 billion cost, enough for them to decide to move ahead with breaking ground in Chile in November.
The site they have chosen in the Atacama desert is one of the driest areas on Earth. It’s ideal not just because there are roughly 300 days a year without clouds, or because of the altitude. The area also lacks human settlements nearby that give off the kind of ambient light that makes it harder to view the stars, a problem that's lessened the effectiveness of some other large telescopes around the world. The Chilean site is so remote that the project’s planners believe that even in 50 years, there will still be no people residing or emitting light from their homes and businesses anywhere near the GMT.
That has also allowed them to invest in some truly astonishing technology.
The telescope’s secondary mirrors will be made from honey-combed glass. That makes them unusually light, but also lets them flex and bend, to compensate for atmospheric turbulence distorting light from distant galaxies.
It’s that kind of turbulence that causes stars to twinkle, but which also presents a headache for astronomers. By flexing tiny portions of their reflecting surface up to 500 times a second, the GMT’s mirrors will give scientists a clearer, stable image.
“Glass has this wonderful property that when you bend it — so long as you don’t break it — unlike metal it has no memory of being bent and returns to its original shape,” McCarthy says. “Glass is pretty stiff. You don’t have to bend it very much.”
But now, as the GMT team reaches for the skies, the first step toward putting the telescope in place is building its foundations by digging a huge hole on that Atacama hilltop.
Quelle: gp
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Update: 31.01.2017
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The world’s biggest telescope needs half a billion dollars more

The Giant Magellan Telescope amps up fundraising as construction moves forward.

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It has been a long road for planners of the Giant Magellan Telescope, which will become the world's largest telescope—if it's completed on schedule. Casting of the first of seven mirrors, each formed from about 20 tons of borosilicate glass made from Florida sand, began way back in 2005. The project seems to finally be closing in on first light as the team amps up fundraising and construction efforts.

The organizers of the telescope are gearing up for fundraising needed to bring the project to completion and have hired a new president with significant executive experience: Robert N. Shelton, a former president of the University of Arizona and provost and executive vice chancellor of the University of North Carolina at Chapel Hill. "Anyone who has been a president and a provost understands the importance of fundraising," Shelton told Ars in an interview.

In the last 15 years or so, the project to build a 24.5-meter telescope in Chile's Atacama desert has raised slightly more than half of the project's $1.05 billion cost. The telescope would be about two-and-a-half times larger than any existing optical telescope. Raising the remainder will not be easy for a telescope, Shelton acknowledged. "For grateful alumni or hospital patients that’s a smaller number in terms of a fundraising campaign," he said. "But if you’re an observatory, it’s a little more challenging."

In the meantime, the group has continued to press ahead with construction at the site in the high desert. In late 2015, bulldozers began leveling a road to the site at 2,516 meters (8,255 feet), and during the past year, three buildings have been constructed that will provide housing for workers and eventually,astronomers. By the end of this year, Shelton said, excavation will begin to build a foundation for the massive telescope itself, and the organization will issue "requests for proposals" for mirror mounts that will support each of the 8.4-meter mirrors.

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The current timeline calls for completing construction of a partial four-mirror version of the telescope (which will have seven mirrors when completed) in 2023. Four of the mirrors have been cast and are in various states of polishing. But the overall timeline remains aspirational and dependent upon funding. A decade ago, the group had intended to finish the telescope as early as 2016.

Time matters because two other projects are also in various stages of building a super-large optical telescope—The Thirty Meter Telescope led by California institutions and backed by the Gordon and Betty Moore Foundation, and a European telescope consortium with an even more ambitious 39-meter instrument. The Thirty Meter Telescope project has run into controversy as some native Hawaiians oppose the instrument's construction atop Mauna Kea on Hawaii’s Big Island. The European project also faces significant technical problems associated with assembling such a large instrument.

Quelle: ars technica

 


Tags: GMT Astronomie - The Giant Magellan Telescope (GMT) - Update-1 

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