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ESO: 50 years of space observations

Article written by Théo Pirard

On 5 October 1962, a new organisation saw the light of day in Europe: ESO, which stands for the European Southern Observatory. The European Southern Observatory was born. That day, its birth certificate – the ESO Convention – was signed by six countries: Germany, Belgium, France, the Netherlands, Sweden and the United Kingdom. Although the UK didn’t confirm its membership until 40 years later! It took a decade of discussions between scientists and politicians for this idea of a European observatory for the community of astronomers and astrophysicists to take shape. The University of Liège played a pioneering role in it and was soon joined by Liège’s space industry.

At the University of Liège, Professor Pol(ydore) Swings (1906-1983) was one of these pioneers. Having worked in the United States, he was conscious that the European dimension was THE answer to research and technology challenges. He was highly active in the interest groups at the beginning of the 1960s, which convinced the political authorities to create ESO for earth-based telescopes, then ESRO (European Space Research Organisation) for space probes and satellites. In the aftermath of the Second World War, it was a matter of rebuilding the sciences and leading-edge technology in Europe, on the basis of cooperation between the various countries, while innovating. Hence, ESO wanted to fill the gap by focusing on the observation of Southern Hemisphere’s sky, which was still largely unexplored at the time. Indeed, there weren’t any major observatories below the equator to study Magellanic Clouds in detail, these dwarf galaxies that are satellites (and therefore close by) of our own, and a real key to understanding the evolution of the stars. But the southern sky concealed many other splendours that European astronomers wanted to study such as the greatest star cluster, Omega Centauri, and the strange active galaxy Centaurus A, but also and especially the heart of the Milky Way situated in the constellation of Sagittarius which conceals an enigmatic black hole, weighing several million suns...


ESO is certainly less well known than ESA (European Space Agency), which absorbed ESRO in 1975 in order to embark upon the European space program. However, its achievements and the studies which have been carried out there over the past 50 years are too numerous to mention and have led to major discoveries! This European intergovernmental organisation, which now includes 14 European states (*) plus Brazil, which is in the process of joining, is aiming for the infinitely great by endeavouring to increase our knowledge and understanding of the universe. For this purpose, it makes observatories equipped with leading-edge equipment in Chile, in the Andes, available to astronomers, astrophysicists and cosmologists.
The ESO Council meets two to three times a year to decide on the upgrade of the existing means and the development of new tools. Every member state is represented by two delegates, a public administration representative and one from the national scientific community. 

Heading for the magnificent skies of the Southern Hemisphere

The creation of ESO met two objectives: to make Europe a global reference in astronomy and astrophysics, and to explore the southern universe with high performance tools. These two objectives have been achieved without a doubt! The Atacama Desert in Chile – chosen over South Africa - was to provide ESO with sites of a unique quality thanks to the local geography that is so particular to the Atacama Desert, wedged between the Andes and the Pacific. These sites have more than 300 clear nights a year and the atmospheric stability there is such that it is possible to take images of exceptional quality. In exchange, Chilean astronomers were to be given 10% of the observation time. Three ESO observatories are currently based in northern Chile: the first one is the La Silla observatory in the Serena region at 2,400 m (first observations made in 1966), then Paranal (2,600m) with its four giant telescopes 8 m in diameter in the Antofagasta region (first light in 1998), and more recently in Chajnantor, a plateau at an altitude of almost 5,400 m (whose construction began in 2005) in the San Pedro de Atacama region. ALMA (Atacama Large Millimeter/submillimeter Array) is currently being deployed at the last site, following the APEX prototype (Atacama Pathfinder Experiment): it is a vast radio telescope which will be comprised of 66 satellite dishes (54 with a diameter of 12 m, and 12 with 7 m), when the works are finished in 2014, to listen to the sky in the submillimetric domain. The cost of this project – which is a partnership with the United States (NRAO) and Japan (NAOJ) – is in the region of a billion dollars. Once combined, these satellite dishes will form the most powerful radio interferometer in the world. Its construction will be complete in 2012, but it is already making hitherto unseen observations 24/24, since the observations can also be made during the day.

Besides the five founding countries, there is also Austria, the Czech Republic, Denmark, Finland, Italy, Portugal, Spain, Switzerland and the United Kingdom.

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