Orange County Branch Newsletter
Giant Magellan Telescope
On October 22, 2015, our members got treated to a wonderful presentation about the design and construction of the Giant Magellan Telescope (GMT). What is special about this telescope besides its enormous size is that it will let astronomers see the light of the very first stars when galaxies were starting to form and our universe was less than 1 billion years old. The GMT will provide images to astronomers with ten times the resolution of the images of the Huble Space Telescope.
Amy Carlson made a general introduction of the project and her excitement of being part of the project definitely showed. The Director of the Program, Patrick McCarthy, captivated the audience with his ability to present complex concepts in a very simple and fun manner.
The Giant Magellan Telescope was named after the explorer Ferdinand Magellan. The GMT will be built in an Andean mountain in Chile called Las Campanas, meaning the bells in Spanish. What makes this place so special is that it rarely has clouds to obscure the stars, there is no artificial light pollution and the air is dry, since this is one of the driest desserts in the world. The dark nights make it easier for the astronomers to see the stars. The site where the GMT will be built is 8,500 feet above sea level and not too far from the site, are the Twin Magellan telescopes, built in the year 2000.
Putting things into perspective, the GMT will weigh 1,123 tons and float on a thin film of oil. The building itself is 64.0 meters (210 feet) tall and has bi-parting shutters, (see figures below), that will provide a 30-meter (98-foot) opening to have access to the sky at night. The shutters must be light, air and water tight when closed during the day to avoid damage to the equipment. The building has a moon screen and wind screen allowing the astronomers to make adjustments as needed. Because of its location, the uniqueness of the building and the sensitive equipment that it houses, the building was designed to withstand earthquakes of 8 and 9 magnitudes. The engineers also designed the building to withstand hurricane level winds. Because of all its moving parts, this building is more of a machine than a building.
The heart of the telescope is its primary mirror which gathers light from the heavens and brings it to a focus for astronomers to analyze using precision scientific instruments. The primary mirror is comprised of seven 28-foot diameter individual glass pieces. The primary mirrors are being made from high purity glass at the University of Arizona’s precision mirror laboratory. Although the mirrors weight 20 tons each, they are considered lightweight due to their “honeycomb” structure as shown in the adjacent picture. The laboratory is using ground breaking polishing techniques. The mirrors are “spun cast” through a process that heats up the glass at 2,000 F where it is liquefied and flows into the honeycomb mold assuming a parabolic shape as the furnace rotates.
Once the mirror has cooled, the optical scientist will work on it for more than a year, polishing it to its final shape where it must match optical prescription with a precision of 25 nanometers or one millionth of an inch. The cost of manufacturing each mirror is $20M. The GMT’s full set of mirrors will have a 4,000 square foot of light collecting area, producing images as clear as a dime seen at a distance of 200 miles.
Project construction will offer its challenges. The Andean mountain site is isolated but it can still be reached by road, it has water, electrical power and communications infrastructure. The roads are narrow and trucks specially rigged to transport the large and heavy components of the GMT such as the mirrors shown in the attached picture will require special care. Once completed, the project will have in addition to the main building that houses the telescope, other buildings such as a utility building, construction and first aid offices to be used during construction, warehouse, shop building, water tank, weather tower, lodge, and other minor buildings necessary to support the daily activities of the GMT team.
The construction and commissioning phase started in early 2014 with the site development and mirror production. The enclosure and telescope installation will be completed in mid-2019 and by 2022, the GMT will be operational.
The funding for the GMT requires active engagement by the scientific community, foundations and universities. The GMT partners include universities and institutions from Australia, Korea, and the USA.
This short article barely touches all the intriguing technical details that were provided at the presentation and the reader is encouraged to access the project’s web site at www.gmto.org.