From Giant Magellan Telescope via CfA: “Giant Magellan Telescope Organization Casts Fifth Mirror”

Giant Magellan Telescope, to be at the Carnegie Institution for Science’s Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile, over 2,500 m (8,200 ft) high

Giant Magellan Telescope

Harvard Smithsonian Center for Astrophysics


Center For Astrophysics

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The last piece of glass is placed into the mold for GMT mirror 5. No image credit.

“The Giant Magellan Telescope Organization (GMTO) today announced that it has initiated the casting of the fifth of seven mirrors that will form the heart of the Giant Magellan Telescope (GMT). The mirror is being cast at the University of Arizona’s Richard F. Caris Mirror Laboratory, the facility known for creating the world’s largest mirrors for astronomy. The nearly 25-meter diameter GMT will be sited in the Chilean Andes and will be used to study planets around other stars and to look back to the time when the first galaxies formed. The process of “casting” the giant mirror involves melting nearly 20 tons of glass in a spinning furnace. Once cooled, the glass disk will be polished to its final shape using state-of-the-art technology.

The GMT will combine the light from seven of these 8.4-meter mirrors to create a telescope with an effective aperture 24.5 meters in diameter (80 feet). 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.

Harvard University and the Smithsonian Institution are both members of the GMT project. Other members include Astronomy Australia Ltd., the Australian National University, the Carnegie Institution for Science, the Korea Astronomy and Space Science Institute, the São Paulo Research Foundation, the University of Texas at Austin, Texas A&M University, the University of Arizona, and the University of Chicago. The GMT primary mirrors are made at the University of Arizona’s (UA) Steward Observatory Mirror Lab in Tucson.

‘We are thrilled to be casting the Giant Magellan Telescope’s fifth mirror,’ said Dr. Robert N. Shelton, President of GMTO. ‘The Giant Magellan Telescope project will enable breakthrough discoveries in astronomy, and perhaps entirely new fields of study.’ ”

Each of GMT’s light-weighted mirrors is a marvel of engineering. The mirrors begin as pristine blocks of custom manufactured low-expansion E6 glass from the Ohara Corporation of Japan. Precisely 17,481 kg of these glass blocks have been placed by hand into a custom-built furnace pre-loaded with a hexagonal mold. At the peak of the lengthy casting process, in which the giant furnace spins at up to five revolutions per minute, the glass is heated to 1165°C (2129°F) for about four hours until it liquefies and flows into the mold. The casting process continues as the glass is carefully cooled for three months while the furnace spins at a slower rate. The glass then undergoes an extended period of shaping and polishing. The result of this high-precision process is a mirror that is polished to an accuracy of one twentieth of a wavelength of light, or less than one thousandth of the width of a human hair.

“Casting the mirrors for the Giant Magellan Telescope is a huge undertaking, and we are very proud of the UA’s leading role creating this new resource for scientific discovery. The GMT partnership and Caris Mirror Lab are outstanding examples of how we can tackle complex challenges with innovative solutions,” said UA President Robert C. Robbins. “The University of Arizona has such an amazing tradition of excellence in space exploration, and I have been constantly impressed by the things our faculty, staff, and students in astronomy and space sciences can accomplish.”

With its casting this weekend, the fifth GMT mirror joins three additional GMT mirrors at various stages of production in the Mirror Lab. Polishing of mirror 2’s front surface is well underway; coarse grinding will begin on the front of the third mirror shortly and mirror number 4, the central mirror, will soon be ready for coarse grinding following mirror 3. The first GMT mirror was completed several years ago and was moved to a storage location in Tucson this September, awaiting the next stage of its journey to Chile. The glass for mirror 6 has been delivered to Tucson and mirror seven’s glass is on order from the Ohara factory in Japan.

In time, the giant mirrors will be transported to GMT’s future home in the Chilean Andes at the Carnegie Institution for Science’s Las Campanas Observatory. This site is known for being one of the best astronomical sites on the planet with its clear, dark skies and stable airflow producing exceptionally sharp images. GMTO has broken ground in Chile and has developed the infrastructure on the site needed to support construction activities.

“Creating the largest telescope in history is a monumental endeavor, and the GMT will be among the largest privately-funded scientific initiatives to date,” said Taft Armandroff, Professor of Astronomy and Director of the McDonald Observatory at The University of Texas at Austin, and Vice-Chair of the GMTO Corporation Board of Directors. “With this next milestone, and with the leadership, technical, financial and scientific prowess of the members of the GMTO partnership, we continue on the path to the completion of this great observatory.”

Received via email from CfA.

See the full article from GMT here.

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The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

The Giant Magellan Telescope will be one of the next class of super giant earth-based telescopes that promises to revolutionize our view and understanding of the universe. It will be operational in about 10 years and will be located in Chile.

The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope under construction, planned for completion in 2025.
The location of the telescope is Las Campanas Observatory.

Organizations

The project is US-led in partnership with Australia, Brazil, and Korea, with Chile as the host country.[4] The following organizations are members of the consortium developing the telescope.[27]

Observatories of the Carnegie Institution of Washington
University of Chicago
Harvard University
Smithsonian Astrophysical Observatory
Texas A&M University
University of Arizona
University of Texas at Austin
Australian National University
Astronomy Australia Limited
Korea Astronomy and Space Science Institute (한국천문연구원)
University of São Paulo

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-foot segments surround a central on-axis segment, forming a single optical surface with an aperture of 24.5 meters, or 80 feet in diameter. The GMT will have a resolving power 10 times greater than the Hubble Space Telescope. The GMT project is the work of a distinguished international consortium of leading universities and science institutions.