A new telescope mirror will begin to take shape March 5 at the University of Arizona. It will be the sixth of seven mirrors planned for the Giant Magellan Telescope (GMT), which is under construction in Chile. To create the mirror, technicians place chunks of a special glass in a giant oven. The oven melts the glass and spins rapidly to form the molten glass into a thin disk. The disk is then cooled over a period of months to prevent cracks from forming. After that, it undergoes a long process of grinding and polishing to create the precise shape needed to accurately reflect starlight. This image shows mirror number 5 emerging from the oven. When completed, the GMT will have a mirror surface equivalent to a single mirror about 80 feet (24.5 meters) in diameter, which is far larger than any telescope currently in use. GMT is an international collaboration that includes the University of Texas at Austin astronomy program. [Richard F. Caris Mirror Lab/University of Arizona]