Day 1 at AAS: Catching up on the Giant Magellan Telescope

Posted by Korey Haynes
on Tuesday, January 5, 2016

The Giant Magellan Telescope will comprise seven mirrors, each weighing 40 tons and spanning 8.4 meters. // GMTO Corporation

Today, Tuesday, kicks off the 227th meeting of the American Astronomical Society in Kissimee, Florida. Thousands of scientists are gathered to share their research and the latest developments in their field. I caught up with Patrick McCarthy, the interim president of the Giant Magellan Telescope (GMT).

Eventually comprising seven mirrors, each 8.4 meters in diameter, GMT will span 24.5 meters total and ring in the new generation of so-called "extremely large telescopes" in the 30-meter range. It will dwarf today's largest telescopes, which are only just over 10 meters across.

GMT will see first light in 2022, when only four mirrors will be completed. Because each mirror weighs roughly 40 tons, the telescope builders will need to install dummy mirror weights until all seven are cast and installed, to keep the telescope balanced. One of the central mirrors was cast back in September and is still cooling. In total, it will take about four months to anneal. The other mirrors will soon be under way, with glass for the fifth already obtained and being ordered now for the sixth. Even though only half the telescope's funding has been committed, McCarthy says his team wants to complete the telescope's mirror assembly. Future funding will go toward the telescope's adaptive optics system, enabling it to peer through Earth's flickering atmosphere, and additional cameras and spectrometers.

The telescope will see into the early universe, image exoplanets, and map out the universe near and far. McCarthy looks forward to peering into the first galaxies, a task he has spent fifty hours on with the Gemini telescope, and should be able to accomplish with much greater ease and to earlier times with GMT.

While GMT will be only one of a generation of extremely large telescopes, it will premiere with a high resolution spectrograph capable of untangling the makeup of stars and galaxies that will be unmatched by its cousins. McCarthy explains that GMT's slightly smaller size and focal ratio make such an instrument more feasible for his telescope than its competitors. It will also have a wider field of view, enabling large surveys.

GMT's first four mirrors will be completed by 2022, and construction is already underway at the telescope's Chilean site. The telescope team has a new project manager, and is busily casting its mirrors. In a time when the Thirty Meter Telescope's fate in Hawaii is so uncertain, it's cheering to look forward to the next big projects in astronomy. 

Korey Haynes is an associate editor of Astronomy. For live updates from #AAS227, follow her on Twitter @weird_worlds.

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