Expertise gained in South Africa through the construction of the Southern African Large Telescope (Salt) could be of great value for the construction overseas of a proposed new generation of extra-large telescopes (ELTs).

The vital characteristic of a telescope is the amount of light it can bring to a focus and therefore the area of its light-collecting surface – usually expressed as the diameter of its lens, mirror or, in the case of a conventional radio telescope, its dish.

ELTs are already defined as having a diameter greater than about 30 m.

“Nothing so big has yet been built, but there are plans and ideas for ELTs with diameters of between 30 m and 100 m; technically, the larger of these would be extraordinarily difficult and very expensive,” reveals South African Astronomical Observatory (SAAO) senior astronomer Dr Patricia Whitelock.

“Our idea is to combine these dreams for ELTs with the reality of Salt,” she asserts.

“Salt is only a large telescope (LT), with a diameter of essentially 11 m, but we did it very cheaply,” she highlights.

“We think that the techniques and expertise developed for Salt could be scaled up,” she asserts.

To this end, and to mark the official dedication of Salt in early November, this country will host (from November 14 to November 18) an international symposium entitled ‘The Scientific Case for Extremely Large Telescopes’.

Although the symposium will be a scientific gathering, it will also cover the area where science and engineering meet – what engineering is needed to build and operate the ELTs the astronomers desire? This symposium is being sponsored by the International Astronomical union (IAU – it will be only the second symposium in Africa sponsored by the union) and by the International Union of Pure and Applied Physics (IUPAP).

(Note that this symposium must not be confused with the IUPAP’s quite separate conference to be held in Cape Town in October.) “Through this symposium we hope to attract to South Africa the top LT astronomers from all over the world,” states Whitelock.

“We want to use Salt in collaborative projects with other LTs around the world, and this symposium will introduce Salt to the international LT astronomy community and open the way to joint projects,” she avers.

LTs already in operation include the Keck Observatory in Hawaii, Japan’s Subaru Telescope (also located in Hawaii), and the European Southern Observatory’s Very Large Telescope (VLT), based in Chile.

The VLT is an array of four telescopes, each with a diameter of 8,2 m, which can either operate indepedently or together as an interferometer.

There is also an LT in the Canary Islands.

“The biggest LT concentration is in Hawaii and the second-biggest is in Chile,” reports Whitelock.

This is because Hawaii and Chile are rated as the all-round (observing conditions, infrastructure, costs, and so on) best sites in the world for optical astronomy.

Consequently, the first ELTs are most likely to be sited in these two locations.

“Sutherland is a good site, although South Africa still has Internet bandwidth problems, but Chile and Hawaii are rated as better sites, so there is only a remote chance that Sutherland could get an ELT,” she says.

(Sutherland, in the Northern Cape, is the location of the SAAO’s telescopes and of Salt.) Among many other missions, ELTs would be used to study the first objects in the universe, to understand the formation of galaxies, and explore other solar systems, including searching for earth-like planets and signs of life.

In addition to this international symposium, but scheduled just ahead of the dedication of Salt, there will also be a workshop targeting postgraduate students in South Africa.

“The workshop will be organised by the National Astrophysics and Space Science Programme and by the African Institute of Mathematical Sciences, and will include students from both backgrounds – we hope it will be sponsored by the Department of Science and Technology,” she reports.

The workshop will be addressed by international physicists and astronomers.

“The idea is to show postgraduates from Africa just how exciting astronomy is and what fantastic opportunities we have right here to tackle the really fundamental questions of science,” concludes Whitelock.