Scientists Construct Huge 20-Ton Mirror for Next Mega-Telescope

Aug. 12, 2013 August 2013 | UCSON, Ariz. — An enormous telescope that could help unlock many of the mysteries of the cosmos is really starting to come together.  The third of the seven primary mirrors for the Giant Magellan Telescope was cast here Saturday (Aug. 24) at the University of Arizona's Steward Observatory Mirror Lab. The 20-ton mirror, which measures 27.6 feet (8.4 meters) across, was formed by melting chunks of borosilicate glass in a rotating furnace at 2,140 degrees Fahrenheit (1,170 degrees Celsius).  more>