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12\05 UK - Extremely Large Telescopes - a step closer
Part 1 of 2

Royal Astronomical Society Press Notice
Issued by Jacqueline Mitton, RAS Press Officer

Contact details are listed at the end of this release 

Date: 5 December 2002 

PN02-29

Extremely Large Telescopes -- a step closer
===========================================

Astronomers think big all the time: it's their job. And on 13th 
December, at a meeting hosted by the Royal Astronomical Society in 
London, a group of them will juggle with some truly astounding large 
numbers. On this occasion, though, they won't be discussing the 
distances to remote galaxies, but the phenomenal sizes of the 
telescopes they want to build so they can explore the universe to a 
level of detail previous generations of astronomers would never have 
dreamt possible. Announcing a significant development, Professor Gerry 
Gilmore of Cambridge University will tell the meeting that Europe's 
astronomers have just agreed to join forces in a single project to 
design a new generation of ground- based optical/infrared telescopes, 
the Extremely Large Telescope.

The largest telescopes operating currently (the two Keck Telescopes in 
Hawaii) have segmented mirrors 10 metres across. Now, astronomers 
around the world are working towards a giant leap for astronomy -- 
'extremely large telescopes' (ELTs) up to 100 metres across, 10 times 
bigger than the Kecks. According to Dr Adrian Russell, Director of the 
UK Astronomy Technology Centre (UK ATC) in Edinburgh, a telescope that 
large will take up more glass than has been used in all the telescopes 
built in the history of astronomy put together.

In Europe, several projects have been under study for some years, each 
aimed at identifying the key technological and organisational advances 
that must be met to achieve such a big step. From this month, the two 
main projects -- Euro-50, led from Sweden, and OWL, led from the 
European Southern Observatory (ESO) -- are joining forces with
colleagues throughout Europe to create a single project, which will 
develop a proposal for substantial additional funding from the 
European Union. 

"An ELT facility will revolutionise astronomy with its ability to 
collect light from faint objects and distinguish details in its images 
that have never been seen before", says Eli Atad who is Head of the 
Applied Optics Group at the UK ATC and co-organiser of the meeting.

But ELTs are not just desirable, say astronomers: they are vital. The 
key to understanding a remote astronomical object is its spectrum. 
Collecting enough light to spread into a spectrum requires a much 
larger telescope than recording an ordinary image. "The largest 
telescopes we have today are struggling to obtain spectra of the 
faintest objects observable with the Hubble Space Telescope," says Dr 
Tim Hawarden, Project Scientist for ELTs at the ATC and a speaker at 
the meeting. "Hubble's successor, the James Webb Space Telescope, 
begins operation in less than 10 years. It will discover objects much 
fainter than Hubble can see and the problem of acquiring spectra will 
get ten times worse. To make the most of discoveries with the James
Webb Space Telescope, it's essential to have ELTs operating on the 
ground at the same time." 

As is the case with the Keck Telescopes, the mirrors of the Extremely 
Large Telescopes of the future will not be a single huge disc of 
glass, but will consist of thousands of hexagonal glass 'tiles'. "The 
technology exists", says Eli Atad, "but the mass production of mirror 
segments is a challenge."

"We have to prove that the key technologies are viable and
affordable," says Gerry Gilmore, who chairs the steering committee for 
the new combined European ELT project. "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."

"The potential payoffs from ELTs can fairly be described as awesome" 
says Tim Hawarden. "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. Just how large we can make the new giant telescopes is still a 
matter for debate, and that is part of what the meeting on 13th
December is all about." 

CONTACTS: 

Dr Tim Hawarden
UK Astronomy Technology Centre
Royal Observatory, Edinburgh
Phone: 0131 668 8339 
e-mail: tgh{at}roe.ac.uk 

Eli Atad
UK Astronomy Technology Centre
Royal Observatory Edinburgh
Phone: 0131 668 8202 
Mobile phone: 07718 737175 
e-mail: ea{at}roe.ac.uk 

Prof. Gerry Gilmore
Institute of Astronomy
University of Cambridge
(Chairman of the Steering Committee for the European Large
Telescope) 
Phone: 01223 337506 
Mobile phone: 07712 774522 
Secretary 01223 766097 
e-mail: gil{at}ast.cam.ac.uk 

Dr Adrian Russell
UK Astronomy Technology Centre
Royal Observatory Edinburgh
Phone: 0131 668 8313 
e-mail: apgr{at}roe.ac.uk 
[Not available 9 - 13 December] 

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