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  • Steward to Cast 1st Mirror for Magellan
Dec 2004
TUCSON, Ariz., Dec. 29 -- The University of Arizona Steward Observatory Mirror Laboratory and the Carnegie Observatories of the Carnegie Institution have signed an agreement to produce the first mirror segment for the Giant Magellan Telescope (GMT), a project of the multi-institutional GMT consortium.

The Steward Observatory Mirror Lab in Tucson, Ariz., will cast the 27-foot (8.4-meter) mirror next summer, in 2005.

The GMT will be located at the Carnegie Observatories' site at Las Campanas, Chile.

"The National Academy of Sciences’ astronomy decadal survey has ranked extremely large telescopes as the highest priority for ground-based optical astronomy," Steward Observatory Mirror Laboratory Director and Regents’ Professor J. Roger P. Angel said. "The GMT is the first of this next generation, which is several times larger than the current generation of large telescopes, to begin construction of the primary mirror optics."

The GMT's primary mirror will consist of seven large mirror segments, each 27 feet (8.4 meters) in diameter. The mirror to be cast next summer will be the first of six identical outer segments that will be arranged in a hexagon around the seventh, central element. The GMT will incorporate other advanced technologies pioneered by Steward Observatory and collaborating researchers in Italy. Its adaptive optics system -- a system that compensates for light blurring in Earth's atmosphere -- will be directly integrated into the telescope optics. The deformable secondary mirror will make the correction. Together they will bring light to a focus much as a single mirror 70 feet (21.4 meter) in diameter -- roughly as wide as the 2004 Christmas tree in New York's Rockefeller Center is tall.

The GMT will use the lightweight, honeycombed borosilicate primary mirrors for which the Mirror Lab is famous. Six GMT primary mirror segments will be off axis; that is, they'll focus light at an angle so it merges with light focused by the on-axis central mirror.

The nearly 10-foot (3 meter) diameter secondary mirror will be electro-magnetically gripped by thousands of computer-controlled 'actuators' that tweak the mirror with nanometer precision. The unique system has been pioneered at the MMT and also is being incorporated in the LBT. When corrected for atmospheric blurring with adaptive optics, the telescope will make infrared images 10 times sharper than the Hubble Space Telescope, the same as a single 83-foot (25.4 meter) mirror in space.

Researchers at Steward Observatory also are developing a tomographic system to measure atmospheric blurring.

The GMT builds on concepts and technologies developed for the Large Binocular Telescope (LBT), which is nearing completion on Mount Graham. Scheduled for completion in 2016, the GMT will be able to probe the secrets of planets that have formed around other stars in the Milky Way, peer back in time toward the Big Bang with unprecedented clarity, delve into the nature of dark matter and dark energy and explore the formation of black holes.

The eight partners in the GMT project consortium are the Carnegie Observatories, the University of Arizona, Harvard University, Smithsonian Astrophysical Observatory, University of Michigan, Massachusetts Institute of Technology, University of Texas at Austin and Texas A & M University.

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