Available to member states first and foremost, these observatories are equipped with innovative, high performance instruments which, generally speaking, have been developed for years by university consortiums in collaboration with ESO. This association between astronomical sites of excellence, large telescopes and leading-edge instrumentation, has always allowed European astronomers to be at the forefront of new scientific breakthroughs in the Southern Hemisphere. At the beginning of the 1990s, La Silla had some 15 telescopes of all sizes, including the famous New Technology Telescope (NTT), 3.5 m in diameter. It was truly revolutionary with its active optics mirror, a computer-controlled mount and a “dome” in a completely new form. This telescope was the precursor of the VLT giants. But since then, ESO has had to programme the gradual closure of La Silla’s small telescopes to make savings in order to find the budgets required for projects such as the VLT, ALMA and the future E-ELT, which hasn’t always pleased astronomers. Today, there are only three telescopes left that are used by ESO, but La Silla was given a second chance a few years ago, thanks to the installation of national telescopes on the site (often in the old renovated buildings). There are half a dozen from all sorts of countries including TRAPPIST (Transiting Planets & PlanetesImals Small Telescope), the fruit of a collaboration between the ATI group from ULg’s Insitute of Astrophysics and the Geneva Observatory (See article: Des astrophysiciens liégeois au septième ciel).

Increasingly enormous, powerful and costly

On Cerro Paranal, in the middle of the Atacama Desert, 600 km north of La Silla, ESO has set up its most remarkable tool: the Very Large Telescope (VLT), which is the biggest observatory in the Southern Hemisphere. It is composed of four identical telescopes weighing 550 tons, each with a primary mirror 8.2 m in diameter. These telescopes are capable of seeing stars that are 4000 million times fainter than those we can see with the naked eye. Every telescope is equipped with three instruments worth several million euros each, allowing astronomers to make the sorts of observations they dream of, from near ultraviolet to thermal infrared in different modes such as imaging and spectroscopy! Four other “small” mobile telescopes (1.8 m mirror) – which move on rails – called auxiliary telescopes (AT) are the principal pieces of the VLTI (VLT Interferometer) that allow the particularities of the universe to be observed in 3D at a very high resolution. It was Amos (see below), an SME based in Liège, that designed these unique telescopes and participated in the creation of various parts of the VLT such as the adapter-rotators, the lifting platform and the mirror-cleaning unit.

Not far from the VLT, on Cerro Armazones at 3,060 m, ESO decided to acquire the imposing E-ELT (European-Extremely Large Telescope) as a gift for its 50th birthday. It is a highly complex machine that will use a mirror 39.3 m in diameter, comprised of some 800 segments adjusted to one another to collect images of an exceptional quality. The green light for this enormous telescope was given by the ESO Council in June 2012. It will take 11 years to build and will cost more than EUR 1 billion, including instrumentation. The construction should begin in earnest in the coming months. The E-ELT must be operational by the beginning of the 2020s: it will be the most advanced and most powerful eye in service in the world! It will be a massive step towards characterising exoplanets, particularly their atmosphere, observing the expansion of the universe and better understanding its destiny by trying to uncover the mysteries of dark energy and dark matter, observing the formation of the first stars in embryonic galaxies situated at the edges of the universe... The primary mirror’s control algorithms were elaborated at the University of Liège, while the design of its pre-focal station was researched by Amos. Almost EUR 2 million have already been spent in Belgium on the design studies.

The use of the VLT/VLTI and the appearance of the E-ELT doesn’t in any way call into question the development of the European space observatories by ESA. The astrophysicist Jean-Pierre Swings from Liège, who has completed missions for both ESA and ESO, is convinced that they can live in perfect harmony: “There is a complementarity between earth and space and we must encourage the synergy between telescopes on earth and around it”.  The interest of ESO’s terrestrial means is to combine their use with space systems than can make observations using the wavelengths obscured by the atmosphere.