Size Matters

Designing the Thirty Meter Telescope, the world's largest, poses significant challenges for Canadian and US astronomers and engineers but success may well reveal some of the universe's longest held secrets.

Comments Off on Size Matters May 12, 2009
by Mike McLeod

When Scottish mathematician James Gregory invented his revolutionary reflecting telescope, little could he have known that, 340 years later, his scientific descendants would begin work on The Thirty Meter Telescope (TMT), an instrument capable of answering some of the discipline’s oldest questions, such as how did galaxies, suns and planets first form and are we alone in the universe?

In 2003, the Association of Canadian Universities for Research in Astronomy, the California Institute of Technology, the University of California, and the US-based Association of Universities for Research in Astronomy, agreed to an equal partnership to build the world’s largest telescope. When completed in 2018 at a projected cost of approximately US$700 million, TMT will be as big as a football stadium, dwarfing the reigning 10-meter W.M. Keck Observatory’s collecting power by nine times and the Hubble Space Telescope by nearly 100 times.

The gain in light gathering ability, says Dr. Raymond Carlberg, astronomy and astrophysics professor at the University of Toronto and the Canadian scientific lead on the TMT project, will allow astronomers to see the most distant known objects in the universe. And, given the time it takes light to travel billions of miles across the cosmos, TMT will also peer back approximately 13 billion years to when matter first began to coalesce into stars and galaxies.

“There was a time in the universe where there were no stars and so TNT has the ability of going from today to back to the first stars,” he says. “That’s incredibly exciting.”

“The great thing about astronomy and astrophysics today is that we are genuinely solving problems for things we didn’t even know 10 years ago,” he adds. “For instance, 10 years ago we didn’t know that other stars had planets. Now we know that virtually all other stars have planets. The burning question is could those planets potentially support life. With a big telescope you can begin to ask those questions and get answers.”

Primary mirror
Using a modified version of the first reflecting telescope, TMT will be an aplanatic Ritchey-Chrétien telescope, a design that provides a large field of view compared to more conventional configurations. The 30-meter wide, parabolically-shaped primary mirror collects the faint light from deep space objects and concentrates it onto a much smaller ellipsoid secondary mirror. The secondary then reflects the light down toward a hole in the centre of the primary mirror where a flat and rotate-able tertiary mirror bounces the light sideways to one of the telescope’s large Nasmyth platforms. These platforms will hold the telescope’s various scientific instruments and its adaptive optics, a complex system that filters out thermal turbulence introduced by the Earth’s atmosphere.
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