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The European Southern Observatory (ESO, also more formally the European Organisation for Astronomical Research in the Southern Hemisphere) is an intergovernmental research organisation for astronomy, composed and supported by twelve countries from the European Union plus Switzerland. Created in 1962, 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), which was one of the telescopes which pioneered active optics technology, and more recently the VLT (Very Large Telescope), consisting of four 8-meter class telescopes.

Its numerous observing facilities have made many astronomical discoveries, and produced several astronomical catalogues. Among the more recent are the farthest galaxy ever seen by humans, the Abell 1835 IR1916 galaxy, though this claim seems to be debunked by a series of new articles. In 2005, it obtained the first picture of an exosolar planet, 2M1207b, orbiting a brown dwarf 260 light-years away.

Contents 1 Facilities 2 Instruments at La Silla 2.1 2.2 m telescope 2.2 3.6 m telescope 2.3 New Technology Telescope (NTT) 3 Instruments at Paranal 4 Instruments at Llano de Chajnantor 5 See also 6 External links

Most of its observation facilities are located in Chile (hence the name "Southern"), and the headquarters are located in Garching near Munich, Germany. ESO operates three major observatories in Chile's Atacama desert:

• La Silla Observatory
• Paranal Observatory, which includes the Very Large Telescope
• Llano de Chajnantor Observatory, which will host submillimetre telescopes, and is operated in collaboration with organisations in the USA, Canada and Chile. This site will host the Atacama Large Millimeter Array under construction in collaboration with the NSF (USA), the NRC (Canada), and the NAOJ (Japan).

One of the most ambitious ESO projects is the Overwhelmingly Large Telescope (OWL). If built, it will be the largest optical telescope in the world.

Member countries:

• Belgium
• Czech Republic (since 1 January 2007^[1])
• Denmark
• Finland
• France
• Germany
• Italy
• Netherlands
• Portugal
• Spain (since 1 July 2006^[2])
• Sweden
• Switzerland
• United Kingdom

Host countries^[1]:

• Chile
• Germany

Austria is currently in accession negotiations. [3]

Of the eighteen telescopes at La Silla Observatory, three are operated by ESO for use by the ESO astronomical community:

This telescope is loaned from the Max-Planck-Gesellschaft. Its instrumentation includes both a spectroscope and a wide-field CCD imager capable of mapping substantial portions of the sky in a single exposure.

A conventionally designed horseshoe mount telescope, this is mostly instrumented for infrared spectroscopy.

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. Also it had, at the time of building, innovative thermal control systems to minimise the telescope and dome seeing.

The Very Large Telescope (VLT) is the main instrument, composed of four near-identical 8.2 m telescopes. In addition the four main telescopes can combine their light to make a fifth instrument, the VLTI, Very Large Telescope Interferometer. Four auxiliary telescopes of 1.8 m each are being added to the VLTI to make it available when the main telescopes are being used for other projects. The first two of these were installed in early 2004 and 2005.

The site also houses the 2.5 m VLT Survey Telescope and 4 m VISTA survey telescope with wider fields of view for surveying large areas of sky uniformly.

• Cosmic Background Imager (CBI)
• Atacama Pathfinder Experiment (APEX)
• Atacama Large Millimeter Array (ALMA)

• European Northern Observatory

• ESO
• Paranal Observatory
• Webpage for the ESO telescopes at La Silla Observatory

Coordinates: 48°15′36″N, 11°40′16″E