Sharp and sensitive - but watch the twinkle in its eye

August 11, 2000

Roger Davies argues in favour of Britain joining the European Southern Observatory - a true giant in the star-gazing field

Astronomers at the International Astronomical Union general assembly eagerly await the latest results from 8-10m optical/infrared telescopes. These huge instruments, located on remote mountain tops in Hawaii, Chile and the continental United States, are now the necessary tools for forefront research. Plans are afoot for extremely large telescopes (ELTs) of 30m or even 100m diameter to be constructed over the next 10-15 years. Like Alma, the proposed 64-dish millimetre-wavelength interferometer, these giant telescopes will be global projects involving the collaborative efforts of all the major communities of astronomers.

Over the past decade, the European Southern Observatory has developed into one of the most successful builders of large telescopes, through the construction of an array of four 8m telescopes in the Atacama desert. The United Kingdom already participates in Europe's flagship particle physics and space science organisations -Cern and the European Space Agency - and astronomers are seeking to consolidate by joining the ESO. This will secure their role in future global projects and provide access to an appropriate share of the world's largest telescopes.

Larger telescopes collect more light, enabling astronomers to study more distant, fainter objects and look back in time - with 8m telescopes, we can see galaxies that are less than 1 billion years old, just one-tenth the age of the universe.

The laws of optics predict such instruments should produce sharper images. However, turbulence in the Earth's atmosphere blurs images - what we see as "twinkling". That is why pictures from even the biggest terrestrial telescopes have been spectacularly surpassed by those from the 2.4m Hubble Space Telescope.

Recently, remarkable developments in information technology, high-speed electronics and optics have been brought together to eliminate the problem.

It is the combination of light grasp and imaging fidelity that makes modern large telescopes so much more capable than their forebears, advantages compounded when working in the infrared, waves about five to ten times longer than visible light.

If we are to fathom how stars and planetary systems formed, which is one of the most pressing problems in cosmology, we need to be able to distinguish the details of the minute disks and jets associated with young stars. We must get the largest ground-based telescopes to perform at the theoretical optical limit.

However, much of the action is obscured from view by thick clouds of dust. While visible light is blocked, infrared waves can pass through these clouds, which have recently been detected through their emission of sub-millimetre wavelengths. The associated galaxies are extremely faint and often not seen at all, but by combining the high infrared sensitivity and exquisite imaging of large telescopes, we expect to be able to identify these very faint galaxies in formation.

Over the past 30 years, UK optical/infrared astronomy has flourished. Substantial investments were made in 4m telescopes in the 1970s and 1980s. In terms of access to forefront facilities, the UK was surpassed only by the United States.

University physics departments have increasingly recognised that astronomy provides an attractive entry into the physical sciences. Many groups have been established over the past decade, making an increasing contribution to the nation's scientific and technical education and increasing the demand for research facilities.

Soon there will be about a dozen 8m-class telescopes in operation. While our astronomy has a strong influence on the research agenda being addressed by these instruments, our own share is a quarter of the Gemini project, whose two 8m telescopes in Hawaii and Chile are close to completion. We are falling out of the top ten in the provision of forefront facilities and risk being marginalised from the future global projects.

By joining the ESO, UK astronomers will enhance Europe's position in astronomy, gain access to leading instruments to significantly influence the direction of research, and secure participation in Alma and ELTs.

Roger Davies is professor of astronomy at Durham University and a council member of the Particle Physics and Astronomy Research Council. He writes in a personal capacity.

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