European Southern Observatory
The European Southern Observatory (ESO) is a group of 16 European countries that runs big ground-based telescopes in Chile. It was founded in 1962 and is based in Garching near Munich, Germany. ESO employs about 750 people and collects roughly €162 million a year from its member states. Its main goal is to advance astronomy by providing world-class facilities for scientists.
ESO’s main observing sites are in northern Chile. La Silla, the organization’s original site, hosts several telescopes including the 3.6-meter New Technology Telescope (NTT) and the 2.2-meter MPG/ESO telescope, along with other national instruments. Paranal Observatory sits on Cerro Paranal and houses the Very Large Telescope (VLT): four 8.2-meter Unit Telescopes that can work together as an interferometer, plus the VLT Survey Telescope (VST) and the Visible and Infrared Survey Telescope for Astronomy (VLTI). The VLT’s light-combining capability lets astronomers see details far sharper than any single telescope. ESO’s VLT data have produced more than 600 peer-reviewed papers in some years, and the VLT helped capture iconic results like images of extrasolar planets and stars orbiting the Milky Way’s central black hole.
Nearby, the VISTA telescope (a 4.1-meter survey telescope) and the VST (a 2.6-meter survey telescope) map the sky in infrared and visible light, respectively. These surveys generate enormous amounts of data to study dark energy and near-Earth objects.
On the Llano de Chajnantor plateau, at 5,100 meters altitude, ESO operates ALMA (an array of 66 high-precision antennas for millimeter and submillimeter astronomy). ALMA is a collaboration between Europe (ESO), East Asia, North America and Chile. It can see details up to ten times sharper than the Hubble Space Telescope and is ideal for studying how stars, galaxies, and planets form. ESO also operates APEX (a single 12-meter telescope) at the site.
A major upcoming facility is the Extremely Large Telescope (ELT), a 39.3-meter optical/near-infrared telescope with a five-mirror design. Under construction at Cerro Armazones in Chile, the ELT will be the world’s largest of its kind and will help scientists study planets around other stars, the early universe, supermassive black holes, and dark matter and dark energy.
ESO’s discoveries come from thousands of observing proposals each year. Its archives hold more than 1.5 million images or spectra, totaling about 65 terabytes of data. The organization also runs public outreach programs, including the ESO Supernova Planetarium & Visitor Centre opened in 2018 at ESO’s Garching headquarters.
The idea for a European, southern-hemisphere observatory began in the 1950s and led to the ESO convention in 1962. Chile was chosen as the observatory site in 1963 because many southern-sky targets (like the center of the Milky Way and the Magellanic Clouds) are best viewed from the southern hemisphere.
This page was last edited on 2 February 2026, at 18:05 (CET).