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Making mirrors for the Giant Magellan Telescope

Posted By Jason Davis

2013/09/02 06:00 CDT

Topics: optical telescopes

When the Giant Magellan Telescope goes online around 2020, it will be the first of a new generation of massive telescopes that will be able to look back and see the earliest objects in the Universe. The GMT will also be able to directly image exoplanets up to one million times fainter than their host stars.

The telescope’s third 8.4-meter mirror was cast on August 24, 2013, at the University of Arizona’s Steward Observatory Mirror Lab. The completed telescope will use seven mirrors to give it an effective aperature of 24.5 meters (80 -feet). When completed, it should briefly hold the title for the largest optical telescope in the world.

Jason Davis

Giant Magellan Telescope mirrors one and two

The first two mirrors for the Giant Magellan Telescope sit in the University of Arizona's Steward Observatory Mirror Lab. Mirror one, on the left, is complete, and has a protective coating. Mirror two, on the right, has been cast and is awaiting front surface polishing. Each mirror has a diameter of 8.4 meters, and the finished telescope will have seven mirrors, giving it an effective aperture of 24.5 meters (80 feet).

To create one of the GMT’s 8.4-meter mirrors, technicians painstakingly load chunks of borosilicate glass into a large mold. The glass is then spun in a large oven as it is heated up to 1170 degrees Celsius (2140 degrees Farenheit), which shapes the molten glass into a parabola. It takes three months for the mirror to cool down to the point where technicians can safely open the mold. 

Please enjoy this brief video piece I created that gives an overview of the GMT’s capabilities and the work that goes into creating its massive mirrors. Set the quality to 1080p if you have the bandwidth.