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Giant Magellan Telescope gets green light for construction

The Giant Magellan Telescope (GMT), the third of a trio of megatelescopes that will peer skyward next decade, yesterday received $500 million to begin construction. GMT, which will ultimately cost about $1 billion, will have a mirror 25 meters across, giving it vision 10 times sharper than the Hubble Space Telescope. The funding agreement means that work can begin soon on the observatory structure at Las Campanas in northern Chile and on the instrument itself. The telescope, set to be fully operational by 2024, is backed by 11 institutions in Australia, Brazil, Chile, Korea, and the United States.

"GMT will herald the beginning of a new era in astronomy," said Wendy Freedman of the University of Chicago in Illinois and chair of the Giant Magellan Telescope Organization board of directors in a statement. "It will reveal the first objects to emit light in the universe, explore the mysteries of dark energy and dark matter, and identify potentially habitable planets in the Earth’s galactic neighborhood.”

Today’s top optical and infrared telescopes have mirrors about 10 meters across, but advances in optics mean the next generation will be much bigger. The European Southern Observatory has begun construction of its European Extremely Large Telescope (E-ELT) with a 39-meter mirror at Cerro Armazones in northern Chile, and a group of institutions from China, India, Japan, and the United States has started building the Thirty Meter Telescope (TMT) at Mauna Kea in Hawaii. TMT construction was recently halted following protests by indigenous Hawaiians, and efforts are continuing to find a compromise.

The GMT, which is the smallest of the three, uses a different mirror technology. Its main reflector is made up of seven large mirrors, each one 8.4 meters across with a weight of 17 tons. The other two scopes use a segmented mirror approach, their reflectors patched together with a much larger number of hexagonal mirror tiles (798 on the E-ELT and 492 on the TMT), each one independently steerable.

This new generation of telescopes will allow huge advances in studies of the early universe, of Earth-like planets around other stars, and of the mysterious dark matter and dark energy that influence the structure and expansion of the universe.