The Thirty-Metre Telescope (TMT) Observatory Corporation, which is planning to build a state-of-the-art, 30-metre aperture telescope as part of the next generation of giant professional telescopes, has chosen Mauna Kea in Hawaii as the location for this enormous astronomical observatory, scheduled to be completed by the year 2018.

The decision to base the observatory on Mauna Kea, subject to planning permission from the Hawaiian Department of Land and Natural Resources, will boost an already thriving astronomical community on the island mountaintop. The site boasts 13 different observatories already, including the twin W M Keck ten-metre telescopes, the 8.3-metre Subaru Telescope, the United Kingdom Infrared Telescope, the Gemini North Telescope, the Submillimeter Array and the James Clerk Maxwell Telescope.

Mauna Kea, with its low humidity, low average temperatures and excellent atmospheric conditions (ensuring many clear nights), fought off close competition from Cerro Armazones in Chile. The South American country itself sports an impressive roster of astronomical facilities, such as the European Southern Observatory’s (ESO) Very Large Telescope, and the Gemini South Telescope. ESO plan to announce where they will construct their 42-metre European Extremely Large Telescope (E-ELT) later this year, with potential sites varying from Chile to the Canary Islands, Morocco and Argentina. The E-ELT is also planned to be begin scientific operations in 2018, meaning we will have a giant telescope in each hemisphere.

The TMT’s giant mirror will be constructed from 492 segments. This is to prevent the glass from sagging in the middle, which afflicts all single telescope mirrors over a diameter of about five metres. The result will be a collecting area nine times larger than today’s largest (8–10 metre) optical telescopes, and a resolving power to boot, providing unparalleled views of star and planet formation, the faintest and most distant galaxies, direct images of nearby extra-solar planets, searches for new gravitational lenses and the ability to test dark energy and the expansion of the Universe to a far greater degree than ever before. It won’t just rely on its giant mirror, but also its adaptive optics, able to shift the mirror segments by fractions of a millimetre to compensate for the blurring effect of Earth’s atmosphere.

The TMT Observatory Corporation includes the California Institute of Technology (Caltech), the University of California, the National Astronomical Observatory of Japan and a consortium of Canadian universities. The design phase, which has just culminated with the decision to locate on Mauna Kea, cost 77 million US dollars, with the construction phase expected to cost 300 million US dollars, with grants from the Gordon and Betty Moore Foundation, and fundraising from Caltech and the University of California.