This week, the Mirror Lab of the University of Arizona began work on the sixth of the seven main mirror segments of the Giant Magellanic Telescope (GMT). On March 1, the laboratory began heating the unique glass furnace to a temperature of 1165 degrees Celsius. This is an important stage called spin casting. In total, it took four months to create the mold, and another nine hours to accommodate about 90 tons of rare borosilicate glass.
On Friday, the oven started rotating at about five revolutions per minute. The combination of warmth and movement distributes the glass to the edges, resulting in a distinctive curved surface.
During this weekend, the 8.4-meter mirror will be formed, after which a month-long process of slowly decreasing temperature and stopping will begin. This is necessary for the mirror to cool down evenly, making it strong and eliminating the maximum number of imperfections. It will take another month and a half to cool down to room temperature. A long polishing process will follow.
The production of one glass segment takes a total of four years. The finished mirrors are in storage and will be delivered to Chile, where they will be placed at the observatory. The telescope will begin operation this decade and will capture images 10 times sharper than the Hubble telescope.
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