From the Board of Visitors Executive Committee


Giant Magellan Telescope Third Mirror-Firing Set for August 24, 2013

On the weekend of August 24, 2013, the third 8.4-meter (27.6 ft.) diameter mirror for the Giant Magellan Telescope will be cast inside a rotating furnace at the University of Arizona’s Steward Observatory Mirror Lab underneath the campus football stadium. The Mirror Lab will host a special weekend of events to highlight this milestone in the creation of the optics for the Giant Magellan Telescope.

Members of Board of Visitors are invited to attend the weekend’s activities and to take the opportunity to see the liquid glass as it is spun-cast in a rotating oven at a temperature of 1170 degrees C (2140 F). This casting marks another major step in the construction of the Giant Magellan Telescope, adding to the two previous mirrors, which are now cast and polished.

Preparing a new GMT mirror for firing

Invitees for the weekend include scientists, philanthropists, and supporters from the Giant Magellan Telescope Organization’s 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 our contingent from The University of Texas at Austin.

The GMT features an innovative design utilizing seven mirrors, each 8.4 meters in diameter, arranged as segments of a single mirror 24.5 meters (80 feet) in diameter, to bring starlight to a common focus via a set of adaptive secondary mirrors configured in a similar seven-fold pattern. “In this design the outer six mirrors are off-axis paraboloids and represent the greatest optics challenge ever undertaken in astronomical optics by a large factor” said Roger Angel, Director of the Steward Observatory Mirror Lab (SOML).

The GMT will allow astronomers to answer some of the most pressing questions about the cosmos including the detection, imaging, and characterization of planets orbiting other stars, the nature of dark matter and dark energy, the physics of black holes, and how stars and galaxies evolved during the earliest phases of the universe. “Astronomical discovery has always been paced by the power of available telescopes and imaging technology. The GMT allows another major step forward in both sensitivity and image sharpness” said Peter Strittmatter, Director of Steward Observatory. “In fact the GMT will be able to acquire images 10 times sharper than the Hubble Space Telescope and will provide a powerful complement not only to NASA’s 6.5-meter James Webb Space Telescope (JWST) but also to the Atacama Large Millimeter Array (ALMA) and the Large Synoptic Survey Telescope (LSST), both located in the southern hemisphere.”

Like other mirrors produced by the SOML, the GMT mirrors are designed to be spun cast, thereby achieving the basic front surface in the shape of a paraboloid. Some 21 tons of borosilicate glass, made by the Ohara Corporation, flow into a pre-assembled mold to create a lightweight honeycomb glass structure that is very stiff and quickly adjusts to changes in nighttime air temperature, each resulting in sharper images. The Mirror Lab has already produced the world's four largest astronomical mirrors, each 8.4 meters in diameter. Two are in operation in the Large Binocular Telescope (LBT) – currently the largest telescope in the world, one is for the Large Synoptic Survey Telescope (LSST), and the fourth is the first off-axis mirror for GMT. The Mirror Lab has also produced five 6.5-meter mirrors, two of which are in the twin Magellan telescopes at Las Campanas Observatory in Chile. For more information on the weekend’s events please contact Carolyn Porter at cporter@astro.as.utexas.edu.

More on additional upcoming GMT events (including a Kavli Institute-sponsored science meeting entitled "Cosmology in the Era of Extremely Large Telescopes," to be held in June 2013) and recent updates can be found at:

Giant Magellan Telescope

[Carolyn Porter]

February 2013
Astronomy Program · The University of Texas at Austin
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