Europe plans world's biggest telescope

Brussels, 09 Dec 2002

Astronomers in Europe have agreed to join forces in a single project to design and build the largest optical telescope in the world.

The telescope's main mirror will be up to 100 metres across, and will mean scientists can examine remote objects in space in much more detail. The biggest telescopes currently in operation are between eight and 11 metres across.

Building an Extremely Large Telescope (ELT) of the size now envisaged would be a huge engineering endeavour - not least because the instrument will have to be built thousands of metres above sea level to see the heavens clearly.

The chairman of the organising committee for the project, Professor Gerry Gilmore of Cambridge University, recognises the technical challenge involved. 'The key thing about these giant telescopes is they're big - they're as big as a football pitch. They're sitting outside, on a mountain top, where it's cold and it's windy and there are earthquakes, and it's shaking around; and it weighs up to 10,000 tonnes. So, it's sagging under its own weight. In spite of that, we need it to work to sufficient precision so that light is exactly in focus,' Professor Gilmore told the BBC.

It would be utterly impractical, however, to build a perfect, single mirror 100 metres across and get it up a mountain. To get to the size of telescope desired, the main mirror will therefore have to be segmented into thousands of glass 'tiles'. These would be manipulated by a computer-controlled system of sensors and precision pistons to focus light on to a single point.

Optical tricks that enable current telescopes to see through the Earth's turbulent atmosphere would also be employed to enhance the image still further.

Several ELT projects have been under study for some years in Europe and now the two main initiatives, Euro-50, led by Sweden, and Owl, led by the European Southern Observatory (ESO), will come together to develop a proposal for substantial additional funding from the European Union.

'We have to prove that the key technologies are viable and affordable,' Dr Gilmore said. 'In particular, we have to demonstrate that the huge number of components needed for an ELT can be built taking advantage of industrial scale efficiencies. The challenge is as much managerial and industrial as it is technical. But it must be met if Europe's astronomers are to have the tools they need to keep abreast of international scientific developments.'

Dr Tim Hawarden, a project scientist for ELT at the UK Astronomy Technology Centre in Edinburgh, said the benefits to come from the next generation of instruments would be huge. 'For example, we may be able to see Earth-like planets, if there are any, in orbit around stars up to tens of light-years away, and perhaps even find out what their atmospheres are made of.'

CORDIS RTD-NEWS/© European Communities, 2001