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Construction Begins on the Giant Magellan Telescope – The World's Largest Optical Telescope

Posted by Guy Pirro   09/06/2018 12:19AM

Construction Begins on the Giant Magellan Telescope – The World's Largest Optical Telescope


A rendering of the Giant Magellan Telescope (GMT), depicting the design of the telescope, the enclosure, and the summit. (To get an idea of the size of this telescope, note the automobile parked in front at the right). The Giant Magellan Telescope will be one member of the next class of giant ground-based telescopes that promises to revolutionize our view and understanding of the universe. It is being constructed in Chile's Atacama Desert and is expected to see first light in 2024. The GMT has a unique design that offers several advantages. It is a segmented mirror telescope that employs seven of today’s largest stiff monolith mirrors as segments. Six off-axis 8.4 meter (or 27.6 foot) segments surround a central on-axis segment, forming a single optical surface 25.4 meters (or 83.3 feet) in diameter with a total collecting area of 368 square meters (or 3961 square feet). The GMT will have a resolving power 10 times greater than the Hubble Space Telescope. (Credit: Giant Magellan Telescope – GMTO Corp.) (Image Credit: Giant Magellan Telescope – GMTO Corp, Mason Media Inc.)




Construction Begins on the Giant Magellan Telescope – The World's Largest Optical Telescope


The start of hard rock excavation for the Giant Magellan Telescope’s massive concrete pier and the foundations for the telescope’s enclosure has started in Chile's Atacama Desert. Using a combination of hydraulic drilling and hammering, the excavation work is expected to take about five months to complete. The Giant Magellan Telescope (GMT) is slated to be the first in a new class of extremely large telescopes, capable of producing images with 10 times the clarity of those captured by the Hubble Space Telescope. 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, the light from which has been travelling to Earth since shortly after the Big Bang, 13.8 billion years ago. The telescope is being built at the Carnegie Institution for Science's Las Campanas Observatory in the dry, clear air of Chile's Atacama Desert, and will be housed a structure 22 stories high. GMT is expected to see first light in 2024.

The telescope's 25.4 meter (83.3 foot) primary mirror will consist of seven separate 8.4 meter (27.6 foot) diameter segments, five of which have been cast to date. 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 Steward Observatory of the University of Arizona in Tucson.

The Giant Magellan Telescope's seven mirrors will focus more than six times the amount of light of the current largest optical telescopes and enable astronomers to look deeper into space and further back in time than ever before.

The GMT, expected to have a final weight of about 1600 metric tons, will consist of seven 8.4 meter mirrors supported by a steel telescope structure that will be seated on the concrete pier. It will be housed inside a rotating enclosure that will measure 65 meters (approximately 22 stories) tall and 56 meters wide. The GMT will combine the seven 8.4 meter primary mirror segments and operate them together as if they were part of a single 25.4 meter telescope.

The most challenging part of the work on the summit will be to excavate the solid rock of the mountain top to a depth of 7 meters (23 feet) to hold the concrete for the telescope pier. Much of this work will be done with a hydraulic rock hammer and jack hammer to ensure that the integrity of the solid bedrock below the pier is undamaged.






Las Campanas Observatory, located in the southern Atacama Desert of Chile and owned by the Carnegie Institution for Science, is one of the world’s premier astronomical sites. Known for its clear, dark skies and stable airflow, the site is capable of producing exceptionally sharp images. With its unique design, the GMT will produce images that are 10 times sharper than those from the Hubble Space Telescope in the infrared region of the spectrum and will be used by astronomers to study planets around other stars and to look back to the time when the first galaxies formed.






The first 8.4 meter GMT mirrors for the Giant Magellan Telescope (GMT) have been the most challenging large astronomical mirrors ever made. By the standards used by optical scientists, its "degree of difficulty" is 10 times that of any previous large telescope mirror. Once it becomes operational in the next decade under dark southern-hemisphere skies, GMT will lead a new generation of giant telescopes that will explore planets around other stars and the formation of stars, galaxies, and black holes in the early universe.






The telescope's seven mirrors are being built by optical scientists and engineers at the University of Arizona's Steward Observatory Mirror Laboratory. "There's only one place in the world that can make these mirrors, and that's the University of Arizona Mirror Lab," said Edward Kolb of the University of Chicago.

Engineers have polished the mirrors into an unusual, highly asymmetric shape that ultimately will fit into a single 25.4 meter optical surface composed of the seven circular segments. Altogether, the seven mirrors working together will provide more than 368 square meters (or 3961 square feet) of light collecting area for the telescope.





The Giant Magellan Telescope will peer more deeply into the universe's hidden history than humans have ever attempted. Scientists say the instrument's combined mirrors will be sensitive enough to detect a candle on the moon, or to see the face on a dime 200 miles away.

"When we study the evolution of the universe we can use telescopes as time machines," said Edward Kolb. "Larger telescopes allow us to look farther out in space and further back in time to probe the very earliest history of the universe."


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