Birth of a Great Observatory

For many centuries, maps of the southern sky showed extensive blank areas — the Terra Incognita of the heavens. The year 1595: For the first time, Dutch traders set sail to the East Indies. At night, navigators Pieter Keyser and Frederik de Houtman measured the positions of more than 130 stars in the southern sky. Soon, celestial globes and maps showed twelve new constellations, none of which had ever been seen before by any European.

See this fascinating story from ESOCast.

The British were the first to construct a permanent astronomical outpost in the southern hemisphere. The Royal Observatory at the Cape of Good Hope was founded in 1820. Not much later, John Herschel built his own private observatory, close to South Africa’s famous Table Mountain.

What a view! Dark skies. Bright clusters and star clouds high overhead. Little wonder that Harvard, Yale and Leiden observatories followed suit with their own southern stations. But the exploration of the southern sky still took lots of courage, passion and perseverance. Until fifty years ago, almost all major telescopes were located north of the equator.

So why is the southern sky so important? First of all, because it was largely uncharted territory. You just can’t see the whole sky from Europe. A prominent example is the centre of the Milky Way, our home galaxy. It can hardly be seen from the northern hemisphere, but from the south, it passes high overhead.

And then there are the Magellanic Clouds — two small companion galaxies to the Milky Way. Invisible from the North, but very conspicuous if you’re south of the equator.

And then finally, European astronomers were hindered by light pollution and poor weather. Going south would solve most of their problems.

A scenic boat trip in the Netherlands, June 1953. It was here, on the IJsselmeer, that the German/American astronomer Walter Baade and the Dutch astronomer Jan Oort told colleagues about their plan for a European observatory in the southern hemisphere.

Individually, no one European country could compete with the United States. But together, they might. Seven months later, twelve astronomers from six countries gathered here, in the stately Senate Room of Leiden University. They signed a statement, expressing the desire to establish a European observatory in South Africa. This paved the way for the birth of ESO.

But hang on!… South Africa? Well, it made sense, of course. South Africa already had the Cape Observatory, and, after 1909, the Transvaal Observatory in Johannesburg. Leiden Observatory had its own southern station in Hartebeespoort.

In 1955, astronomers set up test equipment to find the best possible spot for a big telescope. Zeekoegat in the Great Karoo. Or Tafelkopje, in Bloemfontein. But the weather was not all that favourable.

Around 1960, the focus shifted to the rugged landscape of northern Chile. American astronomers were also planning their own southern hemisphere observatory here. Harsh horseback expeditions revealed much better conditions than in South Africa. In 1963, the die was cast. Chile it would be. Six months later, Cerro La Silla was picked as the future site of the European Southern Observatory.

ESO was no longer a distant dream. In the end, five European countries signed the ESO Convention, on 5 October 1962 — the official birthday of the European Southern Observatory. Belgium, Germany, France, the Netherlands and Sweden were firmly committed to jointly reach for the southern stars. La Silla and its surroundings were bought from the Chilean government.

A road was built in the middle of nowhere. ESO’s first telescope took shape, at a steel company in Rotterdam. And in December 1966, the European Southern Observatory opened its first eye on the sky. Europe had embarked on a grand voyage of cosmic discovery.

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