The circle of glass casts a shimmery light like a fine piece of crystal. It weighs 16 tons and stretches 27 feet from edge to edge. Yet its understructure, a honeycombed lattice of one-inch-thick walls, is so precisely wrought that were it dinner-plate size, its filigree of glass would be wine-goblet thin. The surface, a sweeping parabola of Euclidean purity, seems perfectly matched to its function: to peer from a tiny speck in the universe called Earth into an unimaginably distant past when vast galaxies were still forming. In 2002, when it is polished and coated and then paired with a twin atop Mount Graham, Arizona, this mirror will open a new window on the cosmos.
The mirror is the brainchild of astronomer Roger Angel, whose boyish face masks a competitiveness that drove him to engage in one-upmanship with rival mirror makers. Angel’s mirror, shaped and polished, incongruously, in the bowels of the University of Arizona football stadium, is the largest piece of optical glass ever cast. But happily for astronomers,this sleek saucer is only one of an elite new generation of optics that promises to lead them beyond the solar system into unexplored regions of space.
Today, seven of these 8-meter-plus mirrors, four of them already set up 13,800 feet above sea level on Mauna Kea in Hawaii, are poised to begin the journey. Two Keck telescopes, whose jigsaw-style mirrors, assembled from hexagonal pieces, stretch a massive 10 meters across, have been operating on Mauna Kea since 1990 and 1996. Nearby, Japan’s wafer-thin 8.3-meter Subaru (the Japanese name for the Pleiades constellation) telescope collected its first images from space in January. And in the same neighborhood the Gemini North, an 8.1-meter telescope built by a seven-nation consortium that includes the United States, is scheduled to begin scanning the heavens any day.
Southern Hemisphere skies, with a panoply of stars that cannot be seen from the Northern Hemisphere, are about to be probed by the first two of four Europe-financed 8-meter instruments, called collectively the Very Large Telescope. One was scheduled to begin service atop Cerro Paranal in Chile in April. Chile’s Cerro Pachón will get the Gemini South observatory next year.
