Crews have begun to remove 3 million cubic feet of rock from a mountaintop in the Chilean Andes to make room for what will be the world’s largest telescope.
Sometimes life plays out in pleasantly surprising ways. Here, for example, is how Patrick McCarthy, director of what will be the world's largest optical telescope, watched explosives turn the summit of a Chilean peak to rubble — to ready it for construction — and then, a week later, how he unexpectedly found himself speaking to my high-school astronomy class in suburban Boston about the event.
This story begins on March 23rd, when astronomers and dignitaries trekked into the towering Andes northeast of La Serena, Chile, to a vantage overlooking the summit of Cerro Las Campanas. Topping out at 8,400 feet (2,550 m), this remote peak offers very dark skies, little or no risk of future light pollution, excellent atmospheric stability, and a high fraction of clear nights.Cerro Las Campanas is where, in 2007, an international consortium chose to build the Giant Magellan Telescope. But 3 million cubic feet of the summit must be removed before construction can begin, so some serious demolition work is required. March 23rd's "big bang," which accidentally happened two minutes earlier than planned, is the first step in getting the site ready.
The GMT is one of several extremely large telescopes now on astronomers' drawing boards around the world — and it's the one closest to becoming a reality. (Don't confuse the GMT with the even bigger TMT, the Thirty Meter Telescope, which is destined for Mauna Kea but faces serious funding challenges and an uphill legal battle.)The GMT's design calls for seven enormous primary mirrors, each 27½ feet (8.4 m) across, arrayed in a tight cluster that will span more than 83 feet (25 m) edge to edge. When finished, the telescope's 1,000 tons of glass and steel, combined with adaptive-optics technology, will resolve target details down to 0.01 arcsecond, besting the Hubble Space Telescope's resolution tenfold.
I was going to write about all this a week ago. But the images and video made available at the time weren't very good, so I wanted to track down better ones. Also, some critical information on the GMT's website seemed a little dated. For example, I wondered, how could the project be moving toward construction when only 40% of its estimated $750 million cost has been raised to date?
It took a while to track down anyone in the know — all of the GMT's key officials were en route back to California from Chile. But by midweek Patrick McCarthy, the observatory's director, had gotten back to me. "The project has passed a number of critical milestones in recent months," McCarthy noted in an email. "These include successfully polishing the very ambitious off-axis figure in the first primary mirror segment, casting the second primary segment, starting work on the site, and selecting the first-generation of science instruments.""I will be in Boston tomorrow," he added, not realizing that I live there. "Please feel free to call me on my cell if you would like to chat."
Well! Here was a chance to get details straight from the top. His willingness to chat soon turned into a planned face-to-face meeting. One thing led to another and, thanks to McCarthy's flexible schedule, not only did I get to interview him about the GMT but he also agreed to talk about it with my high-school astronomy class. A total win-win!
So what about the financing, I asked. McCarthy says the GMT's 10 institutional partners, anchored by Carnegie Institution of Washington, Harvard, MIT, University of Michigan, and University of Arizona, have raised just over $300 million to date, and he expects them to secure some large commitments later this year. He admits that it's risky to undertake activities like casting giant mirror blanks and blowing up a mountaintop without full funding, but he's confident that the remainder will be found. In fact, the board of directors for the Giant Magellan Telescope Organization just notified the U.S. National Science Foundation that it will not seek federal funding for the project.
Meanwhile, as McCarthy explained to my students, the GMT is proceeding in three phases: conceptual, detailed design, and construction. The project team (led by astrophysicist Wendy Freedman, director of Carnegie Observatories) has reached the second step, and the observatory's design will be finalized this year. "Now it's at the level of optimization," he explains, to capitalize on recent advances in electronics and other components. This overview is a good introduction to the GMT and its scientific potential.The summit of Cerro Las Campanas can be a little windy, so the design of the telescope's wide-open enclosure is being critically reviewed. Also tricky will be getting those seven giant eyes to work together. McCarthy says that ideally the primaries would have been hexagons, which could have been mounted edge to edge in order to create an unbroken collection area. But there's no way to trim the shape of optics so massive.
So when will all this come together? The plan is to have four mirrors feasting on starlight by 2018 and all seven in place by 2020 or 2021. The initial suite of instruments, still being negotiated among the GMT's partners, will probably involve two visible-light spectrographs and one for infrared work out to 5 microns. "We can go to 25 microns," McCarthy adds, thanks to the bone-dry climate that has made the Chilean Andes the top choice for southern-sky observing sites.
As for the impromptu lecture, I'm happy to report that my class proved an eager audience and asked some great questions. McCarthy enjoyed it too. "It is not often that I get to interact with young people — and particularly as bright a group as the students at your school."
Now, can I interest anyone from the Kepler mission to stop by?