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The European Southern Observatory

Space Seen from Earth

Laurent Vigroux, the current director of the Astrophysics Institute of Paris,(1) has also been president of the Council of the European Southern Observatory (ESO) since January 2009. He explains the role of this organization and its future projects.

Tell us about the European Southern Observatory.
laurent vigroux

© D. Jamet/CNES

Laurent Vigroux:
It is an intergovernmental organization which was set up in 1962 to develop modern astronomy in Europe. At the time, the main objective of the five founding countries (Germany, France, the Netherlands, Belgium, and Sweden) was to build a 4-meter telescope at La Silla in Chile that would be dedicated to studying three objects that are hard to observe from the Northern Hemisphere: the Magellanic Clouds, which are the two galaxies closest to our own, and our galaxy, the Milky Way—especially its center. Because this first instrument and those that were added during the 1970s produced excellent results, other countries decided to join ESO, making even more ambitious projects possible. The best-known example was the construction in the 1990s of the four 8-meter telescopes of the Very Large Telescope (VLT) on Mount Paranal in Chile. Today, this observatory is considered the best in the world. ESO now has 14 Member States and owns some 20 instruments at the La Silla and Paranal sites, which enable observations of the sky at almost all wavelengths.

very large telescope

© F. Kamphues/ESO

The Very Large Telescope (VLT) is today considered the best observatory in the world.

What role does ESO play in world astronomy?
ESO occupies a unique place in the discipline as it is currently the largest organization responsible for ground-based instruments: all major European countries are now members. No region of the world has an equivalent structure—namely an organization capable of playing a federative role at the scale of an entire continent, with an annual budget and qualified in-house personnel—not even the US, where telescopes generally belong to universities or private consortia. Furthermore, unlike the European Space Agency which devotes a large share of its activities to space launches and Earth observations, ESO only concerns itself with astronomy. This gives it a much more significant mandate in the eyes of the scientific community.
The latest call for proposals for observations received more than 1200 requests for the use of the ESO telescopes—unfortunately seven times more than available. Every year, 400 scientific articles are published on studies performed using the VLT, i.e., more than one a day. To this figure should be added the 25 to 30 yearly publications that focus on discoveries made using the VLTI (Very Large Telescope Interferometer: the interferometric mode of VLT2) and the telescopes at La Silla.
ESO is today a real science-generating machine to which we owe results as spectacular as the assessment, last year, of the mass of the black hole that lies at the center of our galaxy, or in 2005, the production of the first image of an exoplanet.

To what degree is CNRS involved?
Although indirect, CNRS' involvement in ESO is considerable since most French astronomers work in CNRS laboratories. They also make important contributions to the design of instruments. Out of the 15 instruments of the VLT and VLTI, 7 were designed with the assistance of French teams, 6 of these being from CNRS. Besides, most of the 100 or so French articles based on ESO observations involve CNRS.

What is the relationship between ESO and the various space agencies? Is there competition between space- and land-based astronomy?
Not at all, these two branches of astronomy are complementary. To obtain images of exoplanets, for example, a ground-based 40-meter telescope is essential. But determining where to point it still requires a space-based telescope of the CoRot type.3
Similarly, observing the sky at certain wavelengths—X-ray, gamma-ray, or far-infrared—is not possible from Earth. For this reason, some initiatives have to be taken outside ESO, especially since all terrestrial observation resources are not represented in our organization. ESO does not carry out radioastronomy and does not participate in high-energy astrophysics instruments like HESS or Auger.

How is ESO organized?
The observatory is managed by a Council where each Member State has two representatives. This Council, of which I have been the president since January 2009, is responsible for appointing the director general, approving the budget, and determining our principal policy orientations. ESO's annual budget is just over €130 million, which mainly comes from the contributions of each Member State proportionally to its GDP. Roughly 40% makes up the operational budget, which also includes industrial contracts for the building and instrumentation of the telescopes. The remainder is spent on the 650 or so staff, spread between the ESO head office near Munich (Germany) and the observatories in Chile. It should be noted that in most cases, ESO does not build the instruments that equip its telescopes. It issues calls for proposals that are answered by laboratories in the Member States in exchange for observation time. France is one of the leading countries in this area, and has become renowned for its novel ideas in adaptive optics, the technique that uses a deformable mirror to enable the real-time correction of disturbances caused by the atmosphere. The country boasts several specialized teams, based in science observatories in Marseille, Toulouse, Bordeaux, Grenoble, Nice, and Lyon, and at the French Atomic Energy Commission (CEA).

alma project


The ALMA project aims to build a giant interferometer by 2013 at an altitude of 5104 meters in northern Chile.

How will ESO instruments evolve over the next few years?
The VLT is currently equipped with 12 instruments. These will gradually be replaced by new, second-generation systems, two of which are currently being developed in France. Dedicated to research on exoplanets and to the visible and infrared spectroscopy of distant galaxies, these systems, called SPHERE, MUSE, and KMOS, should be operational by 2012 or 2013. The VLTI also has a second-generation instrumentation plan, in which CNRS will play a major role.
In parallel, ESO represents Europe in a vast international program called ALMA, in which the US, Canada, Japan, and Taiwan also participate. Endowed with a budget of €800 million—half of which comes from ESO as the European contribution—this project aims to build a giant radio interferometer at an altitude of more than 5000 meters at the Llano de Chajnantor, Northern Chile. When it becomes operational in 2013, this network of antennae will be dedicated to studying the composition of interstellar clouds, the clouds of gas and dust from which the first galaxies probably emerged.
As for the post-VLT period, we are currently studying the concept of a 42-meter telescope, the European Extremely Large Telescope (E-ELT), whose main objective will be to obtain images of exoplanets. The ESO Council should decide on its construction by the end of 2010 or mid-2011. It could become fully operational by 2017-18.
But this all depends on the political decisions taken by the different Member States. Supporting this project, which will cost approximately €1 billion, means accepting a substantial increase in their financial contributions.

Interview by Vahé Ter Minassian

A Camera to Film the Universe
OCam, an ultrafast and ultra-sensitive camera for adaptive optics, able to capture 1500 images per second in almost complete darkness, has just been completed. It took five years for a consortium of three French laboratories1 from CNRS-INSU to develop this camera, jointly funded by the European Commission, ESO, and INSU, in the context of the European Opticon project.
It was especially designed to be used on one of the VLT's second-generation instruments, called SPHERE, but will also be used on all VLT adaptive optics systems to come. This ultrafast camera will allow astronomers to measure and then correct for in real-time—and with hitherto unequaled accuracy—the atmospheric turbulence that interferes with the astronomical images captured by large ground-based telescopes.

1. Laboratoire d'astrophysique de Grenoble (CNRS / Université Grenoble-I, Observatoire des sciences de l'Univers de Grenoble (CNRS / Université Grenoble-I / Institut polytechnique Grenoble)), Laboratoire d'astrophysique de Marseille (CNRS / Université Aix-Marseille-I / Observatoire astronomique de Marseille-Provence) and Observatoire de Haute-Provence (CNRS).

Contact information:
Philippe Feautrier,
Jean-Luc Gach,


Notes :

1. Institut d'astrophysique de Paris (CNRS / Université Paris-VI).
2. Interferometry produces images of a cosmic object by operating several telescopes in concert.
3. COnvection, ROtation and planetary Transit.

Contacts :

Laurent Vigroux,
IAP, Paris.


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