The Giant Magellan Telescope. Credit: GMTO Corportaion
The Giant Magellan Telescope will be one of the few super giant earth-based telescopes that promises to revolutionize our view and understanding of the universe. It will be constructed at the Las Campanas Observatory in Chile. Commissioning of the telescope is scheduled to begin in 2021.
The GMT is a segmented mirror telescope that employs seven of today’s largest stiff monolithic mirrors as segments. Six off-axis 8.4 meter segments surround a central on-axis segment, forming a single optical surface 24.5 meters in diameter, with a total collecting area of 368 square meters. Harvard University and the Smithsonian Institution are both members of the GMT project, which also includes Astronomy Australia Ltd., the Australian National University, the Carnegie Institution for Science, the Korea Astronomy and Space Science Institute, the São Paulo Research Foundation, the University of Texas at Austin, Texas A&M University, the University of Arizona, and the University of Chicago.
Richard F. Caris Mirror Lab Casts Fourth GMT Segment. Credit: Ray Bertram, University of Arizona, Steward Observatory
The GMT primary mirrors are made at the Steward Observatory Mirror Lab in Tucson, Arizona. They are a marvel of modern engineering and glassmaking; each segment is curved to a very precise shape and polished to within a wavelength of light—approximately one-millionth of an inch. Light from the edge of the universe will first reflect off of the seven primary mirrors, then reflect again off of the seven smaller secondary mirrors to travel down through the center primary mirror hole to form a single focus on one of various advanced instruments that will analyze the light.
The Giant Magellan Telescope at night. Credit: GMTO Corportaion
One of the most sophisticated engineering aspects of the telescope is what is known as “adaptive optics.” The telescope’s secondary mirrors are flexible. Under each secondary mirror surface, there are hundreds of actuators that will constantly adjust the mirrors to counteract atmospheric turbulence. These actuators, under the command of advanced control systems, will transform twinkling stars into clear steady points of light 10 times sharper than possible with the Hubble Space Telescope. Scientists and engineers at the Center for Astrophysics are playing a crucial role in the design and construction of these control systems.
The location of the GMT also offers a key advantage in terms of seeing through the Earth’s atmosphere. Chile’s Atacama Desert is one of the highest and driest locations on earth, where the GMT will have spectacular conditions for more than 300 nights a year. Las Campanas Peak, has an altitude of over 2,550 meters (8,500 feet) and is almost completely barren of vegetation due to lack of rainfall. The combination of seeing, number of clear nights, altitude, weather and vegetation make Las Campanas Peak an ideal site for the GMT.
The Giant Magellan Telescope mirrors at sunset. Credit: GMTO Corportaion
Perhaps one of the most exciting questions yet to be answered by astronomy is: are we alone? That question will be addressed by the first advanced instrument planned for GMT, the GMT-Consortium Large Earth Finder, or G-CLEF, whose design and construction are being supervised at the Center for Astrophysics. G-CLEF has been optimized to have extreme precision velocity capability, which will allow it to detect the presence of an Earth-mass exoplanet orbiting Sun-like stars.
The unprecedented light gathering ability and resolution of GMT will help with many other fascinating questions in 21st century astronomy as well. What is dark matter and what is dark energy, two mysterious things that comprise most of our universe? How did the first stars form from the diffuse gas of the Big Bang? How did the first galaxies form? What is the fate of the universe?