A seven-mirror telescope spanning 25.5 meters, or nearly 84 feet, the Giant Magellan Telescope (GMT) will focus six times the amount of light that is harnessed by the biggest optical telescopes in operation today. As described on the project website, the GMT will have “six off-axis 8.4 meter or 27-foot segments surround a central on-axis segment, forming a single optical surface 24.5 meters, or 80 feet, in diameter with a total collecting area of 368 square meters”. And although the seven mirrors will not all be in place until 2024, the GMT should start to see first light via three or four of the primary mirrors by 2021, at which point it will already be the world's largest optical telescope "by a good margin" according to project director Pat McCarthy. And once completed, the GMT will leverage cutting-edge optics technology to achieve 10 times the angular resolution of the Hubble Space Telescope in the infrared region of the spectrum.
Specifically, the light collected by the GMT will reflect first off the seven primary mirrors and then again off the seven smaller secondary mirrors, before finally reflecting down through the center primary mirror to advanced CCD (charge coupled device) imaging cameras. At that point the concentrated light will be measured to determine how far away objects are and from what they are comprised.
The GMT's stated purpose is to gaze back to the light that marked the start of our universe, a time shortly after the Big Bang, which today can only be approached by technology's finest radio and x-ray telescopes. At the start, the GMT will seek to discover and explore the origins of the chemical elements (carbon, oxygen, nitrogen and others) that comprise all matter, the formation of the universe's first stars, and the mysteries of dark matter and dark energy. It will also be used to search distant planets for signs of biological processes around other stars in our galaxy.
Construction of the Giant Magellan Telescope is set to begin later this year at the Las Campanas Peak, with the second phase of the project consisting of construction of the actual telescope and a support campus for staff and visiting astronomers. The project's first phase — the preparation of the mountain ridge — took place in 2012, with the removal of 2500 cubic meters of rock from the mountain ridge's southern end to create a flat surface the size of four football fields. The next major construction activity will be to excavate the foundations for the observatory and the massive pier that will form the base of the telescope.
The GMT is one of three ground-based optical super-scopes in the planning, along with the European Extremely Large Telescope (E-ELT) which is also set for construction in Chile, and the Thirty Meter Telescope (TMT) which is set to be built in Hawaii on the Mauna Key volcano (a site that is generating considerable controversy, as Hawaiian activists are characterizing the scope's construction as a desecration of sacred land).
The decision to move forward with funding for the Giant Magellan Telescope was made unanimously by the project's Board of Directors, which include Astronomy Australia, the Australian National University, Carnegie Institution for Science, Harvard, the Korea Astronomy and Space Science Institute, the Smithsonian, Texas A&M University, the University of Arizona, the University of Chicago, the University of Texas at Austin, and Fundação de Amparo à Pesquisa do Estado de São Paulo.