Astronomical changes afoot

The widening scope of British astronomy could spell the end for an Anglo-Australian collaboration. Julia Hinde reports

In the new millennium, optical astronomy - one of the world's oldest sciences - is experiencing a boom.

Several new eight-metre telescopes are under construction in Hawaii in the northern hemisphere and Chile in the south as different consortia of countries outbuild one another, aiming for the best earth window on space.

United Kingdom astronomers are in on the act and although funding is still tight, construction is well under way on the two eight-metre Gemini telescopes in which the UK has a stake. And money has been found from the Joint Infrastructure Fund - the joint Wellcome Trust/government initiative to revamp UK labs and facilities - to deliver a new southern hemisphere four-metre telescope called Vista, probably in Chile.

But as the frontiers of optical astronomy are pushed forward, and as eight-metre telescopes become the leading mode of star study, questions are raised about the UK's existing telescopes.

Can the UK afford to maintain so many telescopes at so many

different sites? Does it need four-metre telescopes at La Palma in the Canaries and Hawaii, as well as in Australia and Chile, when much of the cutting-edge research is being done with eight-metre machines?

One of the first potential casualties of such talk could be the 25-year-old Anglo-Australian Observatory, home to a four-

metre telescope housed at Siding Spring Mountain in the north-west of New South Wales in Australia, jointly funded by the British and Australian governments. It now costs the UK about Pounds 1.4 million per year.

With inferior viewing conditions to Chile, the UK's involvement with the Anglo-Australian Telescope (AAT) is bound to come under the microscope.

"When Vista comes on line, from the UK point of view the AAT comes into question," explains Rachel Webster, head of astronomy at the University of Melbourne. "This is something the Australian community is concerned about." The AAT is Australia's only four-metre telescope.

Phil Charles, professor of astronomy at Oxford University, would agree. "The AAT has been fantastic," he says. "But it's just not a competitive site compared with Chile. It's lower, the seeing conditions are significantly poorer. Many people in the community are viewing Vista as a natural replacement to a com-bination of the AAT and the Schmidt telescopes in Australia.

"With the kind of pressure we have on the community from the particle physics people, who say we don't ever shut telescopes, we will find it hard to justify keeping both Vista and the AAT operating in the south." He adds, however, that enormous amounts of science can still be done with four-metre telescopes, which are likely to be allocated to researchers for larger chunks of time than the eight-metre telescopes and could continue to play a valuable role.

Some point out that despite both being four-metre telescopes, Vista and the AAT are different animals. Vista is being built with the purpose of surveying the sky to back up eight-metre telescopes, to find points of interest for follow up on the higher resolution machines, while the AAT was built for the investigation of individual stars and galaxies, not as a survey telescope. Today the AAT - which was designed to work in optical wavelengths, and whose effectiveness in the infrared is limited - concentrates on spectroscopy. Vista will be optimised to work in both the infrared and optical, and will be designed specifically for surveying.

"Vista does different things," explains Brian Boyle, director of the AAT, who hopes the two southern four-metre telescopes will be complementary. He stresses how the AAT has recently made its name not in imaging but through wide-field spectroscopy. Using instrumentation built at the AAT, astronomers - using the Australian telescope - can now study 400 objects simultaneously over an area of sky four times the diameter of a full moon. The instrument developed at the AAT uses hundreds of small optical fibres that are placed at the exact location of the star and galaxy images the scientists wish to observe. The light they produce is then passed to a spectrograph that splits light into its constituent wavelengths.

"This is where we lead the world," explains Boyle, adding that wide-field spectroscopy is one strategic strength of the AAT which should guarantee its future in the 21st century.

The other, he says, is instrument building, for which scientists at the AAT have become renowned. As the world experiences a boom in telescope building, the AAT's instrument builders are at the cutting edge, providing instrumentation for the European Southern Observatory, for Gemini - a collaboration involving the UK, the United States, Canada, Australia, Argentina and Brazil - and even for the Japanese, who are also building an eight-metre telescope, called Suzuki, on Hawaii.

It is, agrees Professor Charles, as an instrument building facility and as a test telescope for new instrumentation that the AAT may well find a new niche in the 21st century. Much of the AAT's enduring value has come from the fact that instrumentation has been developed to counteract the relatively poor viewing conditions found in Australia.

The UK is now considering the possibility of joining ESO, the European Southern Observatory, which already has two four-metre telescopes in the south and is building a group of four eight-metre telescopes, called the Very Large Telescope, on a mountain called Cerro Paranal in Chile. According to Ian Corbett of the Particle Physics and Astronomy Research Council, international collaboration is bound to be the route to large future telescopes, such as the 50m types scheduled to be built in the first decades of this century. And the sites where they might be placed are not to be found in Australia. The UK is already involved with Munich-based ESO in a telescope called Alma, being built at a 5,200m-high site in Chile, and UK astronomers are impressed with ESO's capabilities.

"I think the AAT has to continue to evolve," explains Paul Murdin, head of astronomy at PPARC. "We cannot continue to send astronomers on highly targeted expeditions to Australia for a small number of nights' observations as we currently do. That mode of four-metre working is no longer as appropriate as it was. It's more relevant for the eight-metre Gemini telescope.

"Science moves on and it is only natural that we develop new interests. Our interests are now building towards Gemini and telescopes bigger than the AAT. The AAT needs to find a new future." He adds: "It may be that our portfolio of telescopes is too big. That means withdrawing from certain telescopes or, with our partners, finding new, less burdensome ways to use them."