This week, the University of Arizona Observatory’s mirror laboratory began work on the sixth of the seven primary mirror segments for the Giant Magellan (GMT) telescope. On March 1, the laboratory began heating its one-of-a-kind glass furnace to a temperature of 1,165 degrees Celsius. This in itself was a major cornerstone in the manufacturing process known as casting. It took about four months to make the mold and another nine hours to cover it with almost 90 tons of rare borosilicate glass.
On Friday, the furnace began to rotate at about five revolutions per minute. The combination of heat and motion will force the glass up the sides of the mold as it melts, leading to the formation of a curved surface. Once the 8.4-meter mirror is cast over the weekend, it will enter a one-month “annealing”
The production of one glass segment takes about four years. In 2019, the university completed work on the second GMT mirror. This one is already in storage and waiting to be transported to Chile. Although the project broke through in 2015, it will not be completed until later in the decade. But once it’s over, GMT will be able to capture images that are 10 times clearer than those created by the Hubble Space Telescope.