Construction on Giant Magellan Telescope Blasts Off

 

 

In the picture below, it is a big explosion taking place on a distant mountaintop in the Chilean Andes. The detonation is the first of 70 carefully controlled blasts being set off to make room for the Giant Magellan Telescope (GMT), a $700 million joint endeavor by an international consortium involving institutions from the United States, South Korea and Australia.

Chilean mountaintop is home to the Carnegie Institution's Las Campanas Observatory, and it is an ideal location for astronomical observations because it is one of the highest and driest places on Earth. There's very little light pollution, the weather patterns are stable, plus its Southern Hemisphere location makes it an ideal spot for peeking at the Large and Small Magellanic Clouds.

Wendy Freedman, chair of the GMO Organization and director of the Carnegie Observatories, said that the blasting will remove roughly 3 million cubic feet of rock to flatten out the peak and make room for two large telescopes. Right now, however, the focus is on just completing the GMT.

The GMT is one of three extremely large telescopes currently being developed, along with the Thirty Meter Telescope (TMT) and the European Extremely Large Telescope (EELT). What makes the GMT unique is that it is comprised of large segments -- seven mirrors, each 28 feet across and weighing 20 tons, carefully ground and polished to within one-millionth of an inch, to achieve very precise resolutions. The final surface area will provide nearly 4000 square feet of surface area to gather light. 

 

Despite the size of this array of mirrors, it won't weigh as much as one might expect because of a unique honeycomb mold being used to cast them inside a giant rotating oven. Thanks to this "spin-casting," the finished glass is mostly hollow and has a natural parabolic shape, ideal for focusing light. It takes less precision grinding and polishing to achieve those excellent resolutions.

Atmospheric interference is a common issue for ground-based telescopes -- even given the near-ideal conditions found on Las Campanas Peak. There is also a layer of flexible secondary mirrors lined with hundreds of actuators. These will respond to any atmospheric turbulence and adjust the secondary mirrors accordingly, ensuring images that could be ten times sharper than those of the Hubble Space Telescope.

Light from the night sky will reflect off the seven primary mirrors, then reflect again off seven smaller secondary mirrors, eventually traveling down to a CCD array that will collect and analyze the concentrated light. Because of the size of its array, the GMT will be able to observe a much larger area of the sky than other similar large telescopes.

"This will enable us to take simultaneous spectra of thousands of distant galaxies at one time," said Freedman. It will also "offer a great capability for studying the formation and evolution of galaxies, including the motions of stars and gas within galaxies, the chemical compositions, the merging of galaxies, and the history of star formations for statistically large samples of galaxies at large cosmological distances."

The GMT will also help astronomers determine the masses of extrasolar planets comparable to Earth -- "rocky planets orbiting solar-like stars," according to Freedman, as well as possibly detecting the chemical signatures of potential extraterrestrial life. I think the possibility of finding alien life might be worth a few mountaintop blasts in the long run.