'Most Powerful Telescope In History' Gets Go Ahead
"TMT, with adaptive optics, gives us a much finer quality of detail than Hubble Space Telescope."
- Richard Ellis, California Institute of Technology
The Universe has steadily been opening up its secrets as more and more giant telescopes spring up like mushrooms around the world. Now approval has been given to build an optical observatory on Hawaii that, for a while, will be the largest on the planet.
The Thirty Meter Telescope (TMT) project won a permit for its construction from the Hawaiian Board of Land and Natural Resources. It means it can now become the latest large instrument to operate from the ideal location near the summit of Mauna Kea, an extinct volcano.
Astronomers hope the telescope will begin scientific observations in 2021, allowing it briefly to take the crown as biggest telescope before the European Extremely Large Telescope (E-ELT) opens its eye on the sky a couple of years later in Chile.
The TMT planners say their telescope, operating in wavelengths ranging from the ultraviolet to the mid-infrared, will be essential to help understand star and planet formation, unravel the history of galaxies and to learn how large-scale structure in the Universe developed.
Currently the largest optical telescope in the world is the 10.4-metre GranTeCan on the Canary Island of La Palma off the north-west coast of Africa. Such monster mountaintop telescopes have huge light-gathering power which, when matched with technology that compensates for the distortions introduced by the atmosphere, allows sharp images of celestial targets.
The telescope within the striking TMT dome will be of Ritchey-Chretien design, with a main mirror that is a mosaic of 492 separate segments to collect the feeble starlight from the depths of the Universe. It will have 144 times the collecting area of the Hubble Space Telescope.
The optical system will reflect the light collected to be analysed by an array of different instruments, using adaptive optics to provide to remove that atmospheric blurring and wobbling.
The dome itself will be spherical with a circular shutter that will open at night when the telescope is operating. This unusual design is intended to protect the telescope from the strong winds that can blow at its high altitude of 4,200 metres above sea level. At the same time it must allow airflow through vents to help control the temperature inside the dome to avoid producing thermal currents during observing.
Construction could start as early as April next year, although the observatory planners must first deal with a challenge from some native Hawaiian groups who consider the site to be sacred. Thirteen telescopes already stand on the mountain a short way above the chosen location for TMT.
The TMT project is a collaboration between California, Canada, Japan, China and India.
image: An artist’s impression of the TMT complex; credit: TMT Observatory Corporation