Green light for tests on really big telescope designs

More mirrors than Stringfellows

European scientists have been given the green light to go ahead with testing designs for a new generation of ground-based telescopes that will be capable of seeing the universe in more detail than Hubble can.

Project ELT (Extremely Large Telescope) aims to build a ground-based optical 'scope up to ten-times the size of current instruments. The mirror in the ELT will be up to 100m across, and capable of collecting 100 times as much light as the 10m diameter Keck telescopes in Hawaii.

There are many designs being considered, scientists heard at the UK National Astronomy Meeting, including a Thirty Metre Telescope (put forward by the US and Canada), The Euro50, and the 100m Overwhelmingly Large Telescope, which we suspect was so-called just so that the team could refer to it as the Owl.

The extra light collecting capability of a telescope of this size will enable astronomers to observe extra-solar planets, and even study the composition of the atmosphere on small, rocky, Earth-like worlds. It is possible that they could even detect extra-solar vegetation.

The telescope will also be used to learn more about dark matter and dark energy, and could have an impact on ongoing work to refine the Hubble constant, the number that governs the rate at which the universe is expanding.

Any of the candidates above will need a new approach to building the mirror, since a mirror can only be made in one piece up to a size of about 8m in diameter. Different projects take different approaches: some are based on combinations of circular 8m mirrors, others plan on building the main mirror out of intersecting hexagonal pieces.

All of the designs would include adaptive optical systems, designed to compensate for atmospheric turbulence.

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