European Southern Observatory

European Southern Observatory

European Southern Observatory (ESO), an intergovernmental organization for astronomical research with headquarters in Garching, near Munich, Germany. The ESO began in 1962 as a consortium among Belgium, France, Germany, the Netherlands, and Sweden. Denmark, Switzerland, Italy, Portugal, Great Britain, Finland, Spain, Czech Republic, and Austria subsequently joined. The ESO operates three observatories in the Atacama desert, Chile.

The older observatory, inaugurated in 1969, is located on Cerro La Silla at an altitude of about 8,000 ft (2,400 m). The initial instrument was a 142-in. (3.6-m) reflecting telescope, but in 1989 the 141-in. (3.58-m) New Technology Telescope (NTT) was installed. Its primary mirror is three times faster than the original and has only half its weight. It uses a principle called active optics, in which the optics are adjusted by computer to react to the changing seeing conditions of the night sky. Other instruments include a 86.6-in. (2.2-m) reflector, a 20-in. (0.5-m) reflector, a 39.4-in. (1-m) Schmidt camera telescope, twin 15.7-in. (0.4-m) astrographic telescopes, a 60-in. (1.52-m) spectrographic reflector, and a 39.4-in. (1-m) photometric reflector. Also located at Cerro La Silla are a 20-in. (0.5-m) reflector belonging to Denmark and a 24.4-in. (0.62-m) reflector belonging to the Univ. of Bochum, Germany.

The second observatory, initiated in 1988 and inaugurated in 1999, is located atop Cerro Paranal at an altitude of about 8,640 ft (2,635 m). The observatory is the home of the Very Large Telescope (VLT) program. Begun in 1996, it links four 315-in. (8-m) telescopes together with several movable 72-in. (1.8-m) telescopes through optical interferometry, a technique in which the signals from each telescope enhance the signals from the others. Completed in 2003, the combination produces a virtual telescope image equivalent to that of a 630-in. (16-m) conventional reflecting telescope. Also there is the Visible and Infrared Survey Telescope for Astronomy (VISTA), which was constructed by a British university consortium and officially handed over to the ESO in 2009. VISTA is 13-ft (4-m) wide-field survey telescope and is equipped with a near infrared camera.

ESO's newest site is Chajnantor, located at an altitude of some 16,730 ft (5,100 m), where construction of the Atacama Large Millimeter/Submillimeter Array (ALMA) began in 2003. When completed it will consist of an array of 66 39-ft (12-m) and 23-ft (7-m) radio telescopes. Also there is the APEX (Atacama Pathfinder Experiment) telescope, a 39-ft (12-m) submilliter radio telescope that is a collaboration among the Max Planck Institute for Radioastronomy, Onsala Space Observatory, and the ESO. It began operations in 2005.

Among the other programs of the observatory is the completion of the photographic Sky Survey for the Southern Hemisphere, in cooperation with the Siding Spring Observatory in Australia. This project is a continuation of the work begun in the Northern Hemisphere with the Schmidt telescope at Palomar Observatory.

The European Southern Observatory (ESO, whose official name is the European Organization for Astronomical Research in the Southern Hemisphere), is an intergovernmental research organization for astronomy, composed and supported by fourteen countries from Europe. Created in 1962, to provide state-of-the-art facilities and access to the Southern Sky to European astronomers, it is famous for building and operating some of the largest and most technologically advanced telescopes in the world, such as the New Technology Telescope (NTT), the telescope that pioneered active optics technology, and the VLT (Very Large Telescope), consisting of four 8-meter class telescopes and four 1.8-m Auxiliary Telescopes.

Its numerous observing facilities have made many astronomical discoveries, and produced several astronomical catalogues. Among the more recent discoveries is the discovery of the farthest gamma-ray burst and the evidence for a black hole at the centre of our Galaxy, the Milky Way. In 2004, the VLT allowed astronomers to obtain the first picture of an extrasolar planet, 2M1207b, orbiting a brown dwarf 173 light-years away. The HARPS spectrograph led to the discoveries of many other extrasolar planet, including a 5 earth mass planet around a red dwarf, Gliese 581c. The VLT has also discovered the candidate farthest galaxy ever seen by humans, Abell 1835 IR1916.


All its observation facilities are located in Chile (because of the need to study the Southern skies and the unique atmospheric conditions of the Atacama Desert, ideal for astronomy), while the headquarters are located in Garching near Munich, Germany. ESO operates three major observatories in Chile's Atacama desert, one of the driest place on Earth:

One of the most ambitious ESO projects is the European Extremely Large Telescope, a 42-m telescope based on an innovative 5-mirror design, following the concept of an Overwhelmingly Large Telescope (OWL). If built, the E-ELT will be the largest optical/near-infrared telescope in the world. ESO has started in early 2006 the design phase of this telescope with the aim to be able to start construction in 2010. The E-ELT would then be ready by 2017.

La Silla

La Silla Observatory hosts eighteen telescopes, albeit most are now closed. Three are still operated by ESO for use by the astronomical community:

MPG/ESO 2.2 m telescope

This telescope is on permanent loan from the Max-Planck-Gesellschaft. Its instrumentation includes a spectroscope and a wide-field CCD (WFI) imager capable of mapping substantial portions of the sky in a single exposure. In 2007, a third instrument was added, GROND, that takes images simultaneously in seven colours. It will be mostly used to determine distances of gamma-ray bursts .

ESO 3.6m Telescope

This conventionally designed horseshoe mount telescope, was mostly used for infrared spectroscopy. It now hosts the HARPS spectrograph, which is devoted to measuring velocities with extreme precision. Values as small as a few cm/s have been obtained. It is thus used especially for the search of extra-solar planets and for asteroseismology. HARPS was used in the discovery of Gliese 581c and Gliese 581d.

New Technology Telescope (NTT)

Although the NTT is almost the same size as the 3.6 m telescope, the use of active optics makes it a higher resolution instrument. The NTT is indeed the first large telescope to be equipped with active optics, a technology developed at ESO, and nowadays used on all major telescopes. The NTT had also, at the time of building, innovative thermal control systems to minimise the telescope and dome seeing.

Other telescopes

Other telescopes present on the La Silla site include three ESO reflectors, two Danish ones, one Dutch refractor, the Swiss Euler telescope, all in the range from 0.5 to 1.5 meter, and the Swedish SEST, 15-m submillimeter radio telescope. All but the Euler telescope are now decommissioned.


The Very Large Telescope (VLT) is the main facility at Paranal. It is composed of four near-identical 8.2-m Unit Telescopes, each hosting two or three instruments, making it certainly the most versatile astronomical facility. The telescopes are named Antu, Kueyen, Melipal and Yepun. The telescopes can also combine their light, in groups of two or three, as an Interferometer. This is the VLTI (Very Large Telescope Interferometer). Four 1.8-m Auxiliary Telescopes (ATs) have been added to the VLTI to make it available when the Unit Telescopes are being used for other projects. These ATs were installed between 2004 and 2007. The first of the Unit Telescopes had its First Light in May 1998 and was offered to the astronomical community on 1 April 1999. The other telescopes followed suit in 1999 and 2000, and the VLT is thus fully operational. Statistics show that in 2007, almost 500 refereed scientific papers were published based on VLT data.

The site also houses the 2.5-m VLT Survey Telescope (VST) and the 4-m VISTA (Visible and Infrared Survey Telescope for Astronomy) with wide fields of view for surveying large areas of sky uniformly, in the visible and infrared, respectively. First Light for VISTA is foreseen in 2008.

In March 2008, Paranal was the location for the filming of several scenes in the 22nd James Bond movie, Quantum of Solace .

Llano de Chajnantor

Member states

Member country Joined
1 January 2007
1 July 2004
24 may 1982
27 june 2000
1 July 2006
8 July 2002
1 July 2008

The Irish Astronomical Association is currently lobbying the Irish Government for membership.

ESO General Directors
Otto Heckmann 1962–1969
Adriaan Blaauw 1970–1974
Lodewijk Woltjer 1975–1987
Harry van der Laan 1988–1992
Riccardo Giacconi (Nobel Prize winner) 1993–1999
Catherine Cesarsky 1999-2007
Tim de Zeeuw from 2007


See also

External links

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