Editing European Southern Observatory

{{short description|Intergovernmental organization and observatory in Chile}}
{{Redirect|ESO|other uses|ESO (disambiguation)|the European Space Agency|ESA}}

{{EngvarB|date=July 2019}}

{{Dmy|date=February 2025}}

{{Infobox organization
| name         = European Organisation for Astronomical Research in the Southern Hemisphere
| image        = [[File:European Southern Observatory (ESO) logo.svg|145px]] [[File:ESO member states.svg|139px]]
| alt          = ESO's standard logo in blue color
| caption      = {{longitem|(L–R): ESO logo; Map of member states|style=width:300px; padding: 6px 0;}}
| abbreviation = ESO<ref>{{cite web |url=https://www.eso.org/public/about-eso/acronyms/ |title=ESO Glossary of Acronyms |access-date=2018-09-07 |archive-date=2013-09-11 |archive-url=https://web.archive.org/web/20130911024041/https://www.eso.org/public/about-eso/acronyms/ |url-status=live }}</ref>
| type         = [[Intergovernmental organisation]]
| purpose      = [[Astronomy]]
| headquarters = [[Garching]], Germany
| membership   = 16
| leader_title = Director General
| leader_name  = [[Xavier Barcons]]
| leader_title2 =
| leader_name2 =
| formation    = {{start date and age|1962}}
| language     = {{longitem|English, French, German}}
| website      = {{URL|https://www.eso.org/}}
}}

[[File:ESO Trailer.webm|thumb|Trailer of the European Southern Observatory]]

The '''European Organisation for Astronomical Research in the Southern Hemisphere''',<ref>{{cite web |url=https://www.eso.org/public/unitedkingdom/about-eso/organisation/ |title=ESO's Organisational Structure |access-date=2018-09-07 |archive-date=2018-09-07 |archive-url=https://web.archive.org/web/20180907182913/https://www.eso.org/public/unitedkingdom/about-eso/organisation/ |url-status=live }}</ref> commonly referred to as the '''European Southern Observatory''' ('''ESO'''), is an [[intergovernmental organization|intergovernmental research organisation]] made up of 16 member states for ground-based [[astronomy]]. Created in 1962, ESO has provided astronomers with state-of-the-art research facilities and access to the southern sky. The organisation employs over 750 staff members and receives annual member state contributions of approximately €162&nbsp;million.<ref>{{cite web |url=http://www.eso.org/public/about-eso/memberstates/ |title=Member States |date=2017-04-02 |access-date=2018-06-15 |archive-date=2020-06-15 |archive-url=https://web.archive.org/web/20200615083311/https://www.eso.org/public/about-eso/memberstates/ |url-status=live }}</ref> Its observatories are located in northern [[Chile]].

ESO has built and operated some of the largest and most technologically advanced [[telescope]]s. These include the 3.6 m [[New Technology Telescope]], an early pioneer in the use of [[active optics]], and the [[Very Large Telescope]] (VLT), which consists of four individual 8.2 m telescopes and four smaller auxiliary telescopes which can all work together or separately. The [[Atacama Large Millimeter Array]] observes the [[universe]] in the [[Terahertz radiation|millimetre and submillimetre]] wavelength ranges, and is the world's largest ground-based astronomy project to date. It was completed in March 2013 in an international collaboration by Europe (represented by ESO), North America, East Asia and Chile.<ref>{{cite web |url=http://www.almaobservatory.org/en |title=ALMA website |access-date=2011-09-21 |archive-date=2011-10-06 |archive-url=https://web.archive.org/web/20111006034647/http://www.almaobservatory.org/en |url-status=live }}</ref><ref>{{cite web |url=http://www.eso.org/sci/facilities/alma/ |title=Welcome to ALMA! |access-date=2011-05-25 |archive-date=2016-06-23 |archive-url=https://web.archive.org/web/20160623232705/http://www.eso.org/sci/facilities/alma/ |url-status=live }}</ref>

Currently under construction is the [[Extremely Large Telescope]]. It will use a 39.3-metre-diameter [[segmented mirror]], and become the [[List of largest optical reflecting telescopes|world's largest]] optical reflecting telescope when operational towards the end of this decade. Its light-gathering power will allow detailed studies of planets around other stars, the first objects in the universe, [[supermassive black hole]]s, and the nature and distribution of the [[dark matter]] and [[dark energy]] which dominate the universe.

ESO's observing facilities have made astronomical discoveries and produced several [[European Southern Observatory Catalog|astronomical catalogues]].<ref>{{cite web |url=http://archive.eso.org/starcat/astrocat/astrocat_screen_list.html |title=ESO Archive |access-date=2011-04-28 |archive-date=2011-07-26 |archive-url=https://web.archive.org/web/20110726144715/http://archive.eso.org/starcat/astrocat/astrocat_screen_list.html |url-status=dead }}</ref> Its findings include the discovery of the most distant [[gamma-ray burst]] and evidence for a [[black hole]] at the centre of the [[Milky Way]].<ref>{{cite journal| title = A gamma-ray burst at a redshift of 8.2| volume=461 | issue = 7268| doi = 10.1038/nature08459 | pmid = 19865165| journal=Nature | pages=1254–1257|arxiv = 0906.1577 |bibcode = 2009Natur.461.1254T | year = 2009| last1 = Tanvir| first1 = N. R.| last2 = Fox| first2 = D. B.| last3 = Levan| first3 = A. J.| last4 = Berger| first4 = E.| last5 = Wiersema| first5 = K.| last6 = Fynbo| first6 = J. P. U.| last7 = Cucchiara| first7 = A.| last8 = Krühler| first8 = T.| last9 = Gehrels| first9 = N.| last10 = Bloom| first10 = J. S.| last11 = Greiner| first11 = J.| last12 = Evans| first12 = P. A.| last13 = Rol| first13 = E.| last14 = Olivares| first14 = F.| last15 = Hjorth| first15 = J.| last16 = Jakobsson| first16 = P.| last17 = Farihi| first17 = J.| last18 = Willingale| first18 = R.| last19 = Starling| first19 = R. L. C.| last20 = Cenko| first20 = S. B.| last21 = Perley| first21 = D.| last22 = Maund| first22 = J. R.| last23 = Duke| first23 = J.| last24 = Wijers| first24 = R. A. M. J.| last25 = Adamson| first25 = A. J.| last26 = Allan| first26 = A.| last27 = Bremer| first27 = M. N.| last28 = Burrows| first28 = D. N.| last29 = Castro-Tirado| first29 = A. J.| last30 = Cavanagh| first30 = B.| display-authors= 29| hdl = 10261/18184| s2cid=205218350 }}</ref><ref>{{cite journal| title = Monitoring stellar orbits around the Massive Black Hole in the Galactic Center| year = 2009| last1 = Gillessen| first1 = S.| display-authors = 4| last2 = Eisenhauer| first2 = F.| last3 = Trippe| first3 = S.| last4 = Alexander| first4 = T.| last5 = Genzel| first5 = R.| last6 = Martins| first6 = F.| last7 = Ott| first7 = T.| doi = 10.1088/0004-637X/692/2/1075| journal = [[The Astrophysical Journal]]| volume = 692| issue = 2| pages = 1075–1109|arxiv=0810.4674|bibcode = 2009ApJ...692.1075G | s2cid = 1431308}}</ref> In 2004, the VLT allowed astronomers to obtain the first picture of an [[extrasolar planet]] ([[2M1207b]]) orbiting a [[brown dwarf]] 173 light-years away.<ref>{{cite journal| title = A giant planet candidate near a young brown dwarf. Direct VLT/NACO observations using IR wavefront sensing|bibcode=2004A&A...425L..29C| last1 = Chauvin| first1 = G.| display-authors = 4| last2 = Lagrange| first2 = A.-M.| last3 = Dumas| first3 = C.| last4 = Zuckerman| first4 = B.| last5 = Mouillet| first5 = D.| last6 = Song| first6 = I.| last7 = Beuzit| first7 = J.-L.| last8 = Lowrance| first8 = P.| volume = 425| date = 2004| pages = L29| journal = [[Astronomy and Astrophysics]]| doi = 10.1051/0004-6361:200400056| issue = 2|arxiv = astro-ph/0409323 |s2cid=15948759}}</ref> The High Accuracy Radial Velocity Planet Searcher ([[HARPS]]) instrument installed on the older ESO 3.6 m telescope led to the discovery of extrasolar planets, including [[Gliese 581c]]—one of the smallest planets seen outside the [[Solar System]].<ref>{{cite web| url = http://obswww.unige.ch/Instruments/harps/| title = The HARPS Home page| access-date = 2011-09-21| archive-date = 2019-03-23| archive-url = https://web.archive.org/web/20190323213158/http://obswww.unige.ch/Instruments/HARPS/| url-status = dead}}</ref>

== History ==

{{multiple image
 |direction = horizontal
 |total_width = 400
 |image1 = ESO Headquarters.jpg
 |image2 = A Bird’s-eye View of ESO.jpg
 |caption1 = The ESO headquarters in [[Garching]], Germany, in 1997
 |caption2 = The same site in 2014, a year after a new extension was built (in the foreground)
}}

The idea that European astronomers should establish a common large observatory was broached by [[Walter Baade]] and [[Jan Oort]] at the [[Leiden Observatory]] in the Netherlands in spring 1953.<ref>{{cite book |title=ESO's Early History |author=Adriaan Blaauw |publisher=ESO |date=1991 |page=4}}</ref> It was pursued by Oort, who gathered a group of astronomers in Leiden to consider it on 21 June that year. Immediately thereafter, the subject was further discussed at the Groningen conference in the Netherlands. On 26 January 1954, an ESO declaration was signed by astronomers from six European countries expressing the wish that a joint European observatory be established in the southern hemisphere.<ref name="ESO Timeline">{{cite web |url=http://www.eso.org/public/about-eso/timeline.html |title=ESO Timeline |access-date=2011-04-28 |archive-date=2013-09-27 |archive-url=https://web.archive.org/web/20130927205026/http://www.eso.org/public/about-eso/timeline.html |url-status=live }}</ref>

At the time, all [[reflector telescope]]s with an [[aperture]] of 2 metres or more were located in the northern hemisphere. The decision to build the observatory in the southern hemisphere resulted from the necessity of observing the southern sky; some research subjects (such as the central parts of the [[Milky Way]] and the [[Magellanic Clouds]]) were accessible only from the southern hemisphere.<ref>{{cite book |title=Europe's Quest for the Universe |author=Lodewijk Woltjer |publisher=EDP Sciences |date=2006}}</ref>

{| class="wikitable floatright" style="font-size: 0.95em; width: 220px;"
! Director General !! In office
|-
| [[Otto Heckmann]]
| align=center | 1962–1969
|-
| [[Adriaan Blaauw]]
| align=center | 1970–1974
|-
| [[Lodewijk Woltjer]]
| align=center | 1975–1987
|-
| Harry van der Laan
| align=center | 1988–1992
|-
| [[Riccardo Giacconi]]
| align=center | 1993–1999
|-
| [[Catherine Cesarsky]]
| align=center | 1999–2007
|-
| [[Tim de Zeeuw]]
| align=center | 2007–2017
|-
| [[Xavier Barcons]]
| align=center | 2017–present
|-
| colspan=2 style="background-color: #f2f2f2; font-size: 0.90em; padding: 6px 0 4px 4px;" | Source: ''www.eso.org, about ESO''<ref>{{cite web |url=http://www.eso.org/public/about-eso/dg-office/previous-dg.html |title=Past ESO Directors General |access-date=2011-04-29 |archive-date=2011-05-13 |archive-url=https://web.archive.org/web/20110513235223/http://www.eso.org/public/about-eso/dg-office/previous-dg.html |url-status=live }}</ref>
|}

It was initially planned to set up telescopes in South Africa where several European observatories were located ([[Boyden Observatory]]), but tests from 1955 to 1962 demonstrated that a site in the [[Andes]] was preferable: When [[Jürgen Stock (astronomer)|Jürgen Stock]] enthusiastically reported his observations from [[Chile]], [[Otto Heckmann]] decided to leave the South African project on hold. ESO—at that time about to sign the contracts with South Africa—decided to establish their observatory in Chile.<ref>{{Cite web |last=DIRK H. LORENZEN |title=Obituary JÜRGE STOCK 1923 – 2004 |url=https://www.eso.org/sci/publications/messenger/archive/no.117-sep04/messenger-no117-65-65.pdf |website=ESO |access-date=2024-05-08 |archive-date=2024-05-08 |archive-url=https://web.archive.org/web/20240508204158/https://www.eso.org/sci/publications/messenger/archive/no.117-sep04/messenger-no117-65-65.pdf |url-status=live }}</ref>  The ESO Convention was signed 5 October 1962 by Belgium, Germany, France, the Netherlands and Sweden. Otto Heckmann was nominated as the organisation's first director general on 1 November 1962. On 15 November 1963 Chile was chosen as the site for ESO's observatory.<ref>{{cite book |title=ESO's Early History |author=Adriaan Blaauw |publisher=ESO |date=1991}}</ref>

[[File:Directors General of ESO – First Stone Ceremony.jpg|thumb|upright=1.1|Directors general of ESO (from left to right): Lodewijk Woltjer, Harry van der Laan, Catherine Cesarsky, Tim de Zeeuw and Xavier Barcons]]
A preliminary proposal for a convention of astronomy organisations in these five countries was drafted in 1954. Although some amendments were made in the initial document, the convention proceeded slowly until 1960 when it was discussed during that year's committee meeting. The new draft was examined in detail, and a council member of [[CERN]] (the European Organization for Nuclear Research) highlighted the need for a convention between governments (in addition to organisations).<ref>{{cite book |title=ESO's Early History |author=Adriaan Blaauw |publisher=ESO |date=1991 |page=7}}</ref>
The convention and government involvement became pressing due to rapidly rising costs of site-testing expeditions. The final 1962 version was largely adopted from the CERN convention, due to similarities between the organisations and the dual membership of some members.<ref>{{cite book |title=ESO's Early History |author=Adriaan Blaauw |publisher=ESO |date=1991 |page=8}}</ref>

In 1966, the first ESO telescope at the La Silla site in Chile began operating.<ref name="ESO Timeline"/> Because CERN (like ESO) had sophisticated instrumentation, the astronomy organisation frequently turned to the nuclear-research body for advice and a collaborative agreement between ESO and CERN was signed in 1970. Several months later, ESO's telescope division moved into a CERN building in [[Geneva]] and ESO's Sky Atlas Laboratory was established on CERN property.<ref>{{cite book |title=ESO's Early History |author=Adriaan Blaauw |publisher=ESO |date=1991 |pages=169, 179}}</ref> ESO's European departments moved into the new ESO headquarters in [[Garching]] (near [[Munich]]), Germany, in 1980.

In 2015, [[Guillem Anglada-Escudé]] confirmed the existence of [[Proxima Centauri b]] at the Southern Observatory.

=== Member states ===
{| class="wikitable sortable floatleft" style="margin-top: 8px;"
! Country
! Accession<ref>{{cite web| url=http://www.eso.org/public/about-eso/memberstates/| title=Member States| last=| website=www.eso.org| access-date=2015-05-11| archive-date=2020-06-15| archive-url=https://web.archive.org/web/20200615083311/https://www.eso.org/public/about-eso/memberstates/| url-status=live}}</ref>
|-
| {{BEL}}
| {{sort|1962|1962}}
|-
| {{DEU}}
| {{sort|1962|1962}}
|-
| {{FRA}}
| {{sort|1962|1962}}
|-
| {{NED}}
| {{sort|1964|1964}}
|-
| {{SWE}}
| {{sort|1964|1964}}
|-
| {{DEN}}
| {{sort|1967|1967}}
|-
| {{SUI}}
| {{sort|1982|1982}}
|-
| {{ITA}}
| {{sort|1982|1982}}
|-
| {{POR}}
| {{sort|2001-1-1|1 January 2001}}
|-
| {{UK}}
| {{sort|2002-7-8|8 July 2002}}
|-
| {{FIN}}
| {{sort|2004-7-1|1 July 2004}}
|-
| {{ESP}}
| {{sort|2006-7-1|1 July 2006}}
|-
| {{CZE}}
| {{sort|2007-1-1|1 January 2007}}
|-
| {{AUT}}
| {{sort|2008-7-1|1 July 2008}}
|-
| {{POL}}
| {{sort|2014-10-28|28 October 2014}}
|-
| {{IRL}}
| {{sort|2018-9-28|28 September 2018}}
|-
|}

{{clear}}

== Chilean observation sites ==

{{Location map+ | Chile
| width = 200
| caption = Map of Chile with ESO's four observatories
| places =
  {{Location map~ | Chile
    | label = [[Llano de Chajnantor Observatory|Chajnantor]]&nbsp;(1999)
    | background = #fdd
    | lat_deg = -23.022778
    | lon_deg = -67.755 }}
  {{Location map~ | Chile
    | label = [[Paranal Observatory|Paranal]] (1998)
    | position = left
    | background = #fdd
    | lat_deg = -24.627222
    | lon_deg = -70.404167 }}
  {{Location map~ | Chile
    | label = [[Extremely Large Telescope|ELT]]<br />
(2024)
    | position = right
    | background = #fdd
    | lat_deg = -24.588889
    | lon_deg = -70.192222 }}
  {{Location map~ | Chile
    | label = [[La Silla Observatory|La Silla]] (1964)
    | background = #fdd
    | lat_deg = -29.261167
    | lon_deg = -70.731333 }}

  {{Location map~ | Chile
    | label = ''Bolivia''
    | marksize = 0
    | lat_deg = -20.0
    | lon_deg = -63.0 }}
  {{Location map~ | Chile
    | label = ''Argentina''
    | marksize = 0
    | lat_deg = -34.0
    | lon_deg = -68.0 }}
  {{Location map~ | Chile
    | label = ''Chile''
    | position = left
    | marksize = 0
    | lat_deg = -33.0
    | lon_deg = -70.5 }}
}}

Although ESO is headquartered in Germany, its telescopes and observatories are in northern [[Chile]], where the organisation operates advanced [[Observatory|ground-based]] astronomical facilities:
* [[La Silla Observatory|La Silla]], which hosts the [[New Technology Telescope]] (NTT)
* [[Paranal Observatory|Paranal]], where the [[Very Large Telescope]] (VLT) is located
* [[Llano de Chajnantor Observatory|Llano de Chajnantor]], where ALMA, the [[Atacama Large Millimeter/submillimeter Array]], is located

These are among the best locations for astronomical observations in the southern hemisphere.<ref>{{cite web |url=http://www.almaobservatory.org/en/about-alma/location/why-chile |title=The best observing sites on Earth |access-date=2011-05-13 |archive-url=https://web.archive.org/web/20110414111949/http://www.almaobservatory.org/en/about-alma/location/why-chile |archive-date=2011-04-14 |url-status=dead }}</ref> An ESO project is the [[Extremely Large Telescope]] (ELT), a 40-metre-class telescope based on a five-mirror design and the formerly planned [[Overwhelmingly Large Telescope]]. The ELT will be the largest visible and near-infrared telescope in the world. ESO began its design in early 2006, and aimed to begin construction in 2012.<ref name="The E-ELT project">{{cite web |url=http://www.eso.org/sci/facilities/eelt/ |title=The E-ELT project |access-date=2011-04-29 |archive-date=2020-06-13 |archive-url=https://web.archive.org/web/20200613014619/https://www.eso.org/sci/facilities/eelt/ |url-status=live }}</ref> Construction work at the ELT site started in June 2014.<ref name=beginning>{{cite news|url=https://www.independent.co.uk/news/science/european-extremely-large-telescope-to-break-ground-using-dynamite-live-later-today-9548123.html|title=European Extremely Large Telescope to break ground (using dynamite) live later today|author=James Vincent|newspaper=The Independent|date=19 June 2014|archive-date=3 May 2020|access-date=27 August 2017|archive-url=https://web.archive.org/web/20200503011912/https://www.independent.co.uk/news/science/european-extremely-large-telescope-to-break-ground-using-dynamite-live-later-today-9548123.html|url-status=live}}</ref> As decided by the ESO council on 26 April 2010, a fourth site ([[Cerro Armazones]]) is to be home to ELT.<ref>{{cite news |date=26 April 2010 |title=E-ELT Site Chosen |url=http://www.eso.org/public/news/eso1018/ |publisher=ESO |access-date=2011-04-29 |archive-date=2015-12-22 |archive-url=https://web.archive.org/web/20151222121709/http://www.eso.org/public/news/eso1018/ |url-status=live }}</ref><ref>{{cite web| url = http://site2010.sai.msu.ru/section/4| title = Comprehensive characterization of astronomical sites| access-date = 2011-10-04| archive-date = 2016-03-04| archive-url = https://web.archive.org/web/20160304000216/http://site2010.sai.msu.ru/section/4| url-status = live}}</ref><ref>{{cite web| url = http://www.dfa.uv.cl/sitetestingdata/index.htm/4| title = Conference Astronomical Site Testing Data in Chile| access-date = 2011-10-04}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

Each year about 2,000 requests are made for the use of ESO telescopes, for four to six times more nights than are available. Observations made with these instruments appear in a number of peer-reviewed publications annually; in 2017, more than 1,000 reviewed papers based on ESO data were published.<ref name="ESOstats">{{cite web| url = http://www.eso.org/sci/libraries/edocs/ESO/ESOstats.pdf| title = ESO Publication Statistics| access-date = 2018-08-06| archive-date = 2019-02-21| archive-url = https://web.archive.org/web/20190221051951/http://www.eso.org/sci/libraries/edocs/ESO/ESOstats.pdf| url-status = live}}</ref>

ESO telescopes generate large amounts of data at a high rate, which are stored in a permanent archive facility at ESO headquarters. The archive contains more than 1.5&nbsp;million images (or spectra) with a total volume of about 65&nbsp;terabytes (65,000,000,000,000&nbsp;bytes) of data.

{| class="wikitable" style="font-size: 1.0em; margin: 1px auto;"
|+ ESO telescopes
|-
! Name || width=70 | Short || width=95 | Size || Type || Location || width=60 | Year
|-
| &nbsp;[[ESO 3.6 m telescope]] {{small|– ''hosting [[HARPS]]''}} || align=center | ESO&nbsp;3.6m || align=center | 3.57&nbsp;m || optical and infrared || [[La Silla Observatory|La Silla]] || align=center | 1977
|-
| &nbsp;[[MPG/ESO telescope|MPG/ESO 2.2 m telescope]] || align=center | MPG || align=center | 2.20&nbsp;m || optical and infrared || La Silla || align=center | 1984
|-
| &nbsp;[[New Technology Telescope]] || align=center | NTT || align=center | 3.58&nbsp;m || optical and infrared || La Silla || align=center | 1989
|-
| &nbsp;[[Very Large Telescope]] || align=center | VLT || align=center | 4 × 8.2&nbsp;m<br />4 × 1.8&nbsp;m || optical to mid-infrared, array || [[Paranal]] || align=center | 1998
|-
| &nbsp;[[VISTA (telescope)|Visible and Infrared Survey Telescope for Astronomy]] || align=center | VISTA || align=center | 4.1 m || near-infrared, survey || Paranal || align=center | 2009
|-
| &nbsp;[[VLT Survey Telescope]] || align=center | VST || align=center | 2.6 m || optical, survey || Paranal || align=center | 2011
|-
| &nbsp;[[Atacama Large Millimeter/submillimeter Array]]{{ref label|about-alma|A|A}} || align=center | ALMA || align=center | 50 × 12&nbsp;m<br />12&nbsp;×&nbsp;7&nbsp;m<br />4 × 12&nbsp;m<ref>{{cite journal |author=Satoru Iguchi |date=2009 |title=The Atacama Compact Array (ACA) |journal=Publications of the Astronomical Society of Japan |volume=61 |issue=1 |pages=1–12 |url=http://pasj.asj.or.jp/v61/n1/610101/610101-frame.html |access-date=2011-04-29 |bibcode=2009PASJ...61....1I |last2=Morita |first2=Koh-Ichiro |last3=Sugimoto |first3=Masahiro |last4=Vila Vilaró |first4=Baltasar |last5=Saito |first5=Masao |last6=Hasegawa |first6=Tetsuo |last7=Kawabe |first7=Ryohei |last8=Tatematsu |first8=Ken'Ichi |last9=Seiichi |first9=Seiichi |last10=Kiuchi |first10=Hitoshi |last11=Okumura |first11=Sachiko K. |last12=Kosugi |first12=George |last13=Inatani |first13=Junji |last14=Takakuwa |first14=Shigehisa |last15=Iono |first15=Daisuke |last16=Kamazaki |first16=Takeshi |last17=Ogasawara |first17=Ryusuke |last18=Ishiguro |first18=Masato |display-authors=9 |doi=10.1093/pasj/61.1.1 |doi-access=free |archive-date=2017-06-23 |archive-url=https://web.archive.org/web/20170623154918/http://pasj.asj.or.jp/v61/n1/610101/610101-frame.html |url-status=live }}</ref> || millimetre-/submillimetre-wavelength<br />[[Astronomical interferometer|interferometer array]] || Chajnantor || align=center | 2011
|-
| &nbsp;[[Extremely Large Telescope]] || align=center | ELT || align=center | 39.3 m || optical to mid-infrared || [[Cerro Armazones]]<ref name="The E-ELT project"/> || align=center | ''End of this decade''
|-
| colspan=6 style="font-size:0.92em; padding: 12px 0 6px 4px; background-color: #f2f2f2;" |{{note label|about-alma|A|A}}ALMA is a partnership among Europe, the United States, Canada, East Asia and the Republic of Chile.<br />{{·}}Additional ESO research facilities are located in Santiago, Chile and include a library, computing resources and programmes for visiting scientists.<ref>{{cite web| url = http://www.eso.org/sci/activities/santiago.html| title = Science in Santiago| access-date = 2011-10-04| archive-date = 2020-05-29| archive-url = https://web.archive.org/web/20200529060003/https://www.eso.org/sci/activities/santiago.html| url-status = live}}</ref><br />{{·}}ESO also maintains close ties with other observatories and universities throughout the country.<ref>{{cite web| url = http://www.sochias.cl/docs/ESOChileMinutes20060316.pdf| title = Minutes of the ESO Chile Joint Committee| access-date = 2011-10-05| url-status = dead| archive-url = https://web.archive.org/web/20120425050041/http://www.sochias.cl/docs/ESOChileMinutes20060316.pdf| archive-date = 2012-04-25}}</ref><ref>{{cite web| url = http://www.eso.org/public/outreach/partnerships/chile.html| title = Cooperative Projects in Chile| access-date = 2011-10-05| archive-date = 2013-08-06| archive-url = https://web.archive.org/web/20130806212730/http://www.eso.org/public/outreach/partnerships/chile.html| url-status = live}}</ref><br />{{·}}Source: ''ESO – Telescopes and Instrumentation''<ref>{{cite web |url=http://www.eso.org/public/teles-instr.html |title=Telescopes and Instrumentation |access-date=2011-04-29 |archive-date=2013-09-01 |archive-url=https://web.archive.org/web/20130901034805/http://www.eso.org/public/teles-instr.html |url-status=live }}</ref>
|}

=== La Silla ===
{{Main|La Silla Observatory}}
[[File:Observatorio la silla1.JPG|thumb|upright=1.2|La Silla cluster of telescopes]]
La Silla, located in the southern [[Atacama Desert]] {{convert|600|km}} north of [[Santiago de Chile]] at an altitude of {{convert|2400|m}}, is the home of ESO's original observation site. Like other observatories in the area, La Silla is far from sources of [[light pollution]] and has one of the darkest night skies on Earth.<ref>{{cite web |url=http://www.chile.travel/en/what-to-do/astronomy/touristic-observatories.html |title=Observatories in Chile |access-date=2011-10-05 |url-status=dead |archive-url=https://web.archive.org/web/20110923095254/http://chile.travel/en/what-to-do/astronomy/touristic-observatories.html |archive-date=2011-09-23 }}</ref> In La Silla, ESO operates three telescopes: a 3.6-metre telescope, the New Technology Telescope (NTT) and the 2.2-metre Max-Planck-ESO Telescope.

The observatory hosts visitor instruments, attached to a telescope for the duration of an observational run and then removed. La Silla also hosts national telescopes, such as the 1.2-metre Swiss and the 1.5-metre Danish telescopes.

About 300 reviewed publications annually are attributable to the work of the observatory. Discoveries made with La Silla telescopes include the [[High Accuracy Radial Velocity Planet Searcher|HARPS-spectrograph]] detection of the planets orbiting within the [[Gliese 581 planetary system]], which contains the first known rocky planet in a habitable zone outside the solar system.<ref>{{cite news|date=25 April 2007|url=http://www.eso.org/public/news/eso0722/|publisher=ESO|title=Astronomers Find First Earth-like Planet in Habitable Zone|access-date=2011-04-28|archive-date=2020-06-12|archive-url=https://web.archive.org/web/20200612200927/https://www.eso.org/public/news/eso0722/|url-status=live}}</ref><ref>{{cite web|url=http://obswww.unige.ch/%7Eudry/udry_preprint.pdf | title = The HARPS search for southern extra-solar planets | access-date = 2011-10-04}}</ref> Several telescopes at La Silla played a role in linking [[gamma-ray burst]]s, the most energetic explosions in the universe since the [[Big Bang]], with the explosions of massive stars. The ESO La Silla Observatory also played a role in the study of supernova [[SN 1987A]].<ref>{{cite news |date=24 February 2007 |title=SN 1987A's Twentieth Anniversary |url=http://www.eso.org/public/news/eso0708/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-06-12 |archive-url=https://web.archive.org/web/20200612060522/https://www.eso.org/public/news/eso0708/ |url-status=live }}</ref>

==== ESO 3.6-metre telescope ====
{{Main|ESO 3.6 m Telescope}}
[[File:3.6-m Telescope at La Silla.jpg|thumb|upright=0.6|The [[ESO 3.6 m Telescope]]]]
The ESO 3.6-metre telescope began operations in 1977. It has been upgraded, including the installation of a new [[secondary mirror]].<ref>{{cite web |url=http://www.eso.org/sci/facilities/lasilla/telescopes/3p6/ |title=The ESO 3.6m Telescope |access-date=2011-05-05 |archive-date=2012-10-19 |archive-url=https://web.archive.org/web/20121019071518/http://www.eso.org/sci/facilities/lasilla/telescopes/3p6/ |url-status=live }}</ref> The conventionally designed [[Telescope#Telescope mountings|horseshoe-mount]] telescope was primarily used for [[infrared]] [[spectroscopy]]; it now hosts the HARPS spectrograph, used in search of [[extra-solar planets]] and for [[asteroseismology]]. The telescope was designed for very high long-term [[radial velocity]] accuracy (on the order of 1&nbsp;m/s).<ref>{{cite web |url=http://www.eso.org/sci/facilities/lasilla/instruments/harps/overview.html |title=HARPS: The Planet Hunter |access-date=2011-05-05 |archive-date=2020-05-30 |archive-url=https://web.archive.org/web/20200530003012/https://www.eso.org/sci/facilities/lasilla/instruments/harps/overview.html |url-status=live }}</ref>

==== New Technology Telescope ====
{{Main|New Technology Telescope}}
[[File:The NTT Enclosure.jpg|thumb|upright=0.6|The [[New Technology Telescope]]]]
The New Technology Telescope (NTT) is an [[Altazimuth mount|altazimuth]], 3.58-metre [[Ritchey–Chrétien telescope]], inaugurated in 1989 and the first in the world with a computer-controlled main mirror. The flexible mirror's shape is adjusted during observation to preserve optimal image quality. The secondary mirror position is also adjustable in three directions. This technology (developed by ESO and known as [[active optics]]) is now applied to all major telescopes, including the VLT and the future ELT.<ref>{{cite journal | url = http://www.eso.org/sci/publications/messenger/archive/no.142-dec10/messenger-no142-41-41.pdf | title = Raymond Wilson honoured with two prestigious prizes | journal = The Messenger | volume = 142 | pages = 41 | access-date = 2011-10-05 | bibcode = 2010Msngr.142...41W | last1 = Walsh | first1 = J. | year = 2010 | archive-date = 2019-12-08 | archive-url = https://web.archive.org/web/20191208003846/http://www.eso.org/sci/publications/messenger/archive/no.142-dec10/messenger-no142-41-41.pdf | url-status = live }}</ref>

The design of the octagonal enclosure housing the NTT is innovative. The telescope dome is relatively small and ventilated by a system of flaps directing airflow smoothly across the mirror, reducing turbulence and resulting in sharper images.<ref>{{cite web |url=http://www.eso.org/public/teles-instr/lasilla/ntt.html |title=ESO NTT |access-date=2011-05-05 |archive-date=2013-08-07 |archive-url=https://web.archive.org/web/20130807080311/http://www.eso.org/public/teles-instr/lasilla/ntt.html |url-status=live }}</ref>

==== MPG/ESO 2.2-metre telescope ====
{{Main|MPG/ESO telescope}}

The 2.2-metre telescope has been in operation at La Silla since early 1984, and is on indefinite loan to ESO from the [[Max Planck Society]] ({{Lang|de|Max-Planck-Gesellschaft zur Förderung der Wissenschaften}}, or MPG, in German). Telescope time is shared between MPG and ESO observing programmes, while operation and maintenance of the telescope are ESO's responsibility.

Its instrumentation includes a 67-million-pixel wide-field imager (WFI) with a [[Field of view#Astronomy|field of view]] as large as the full moon,<ref>{{cite web |url=http://www.eso.org/lasilla/instruments/wfi/index.html |title=WFI—Wide Field Imager |access-date=2011-04-29 |archive-url=https://web.archive.org/web/20110902075709/http://www.eso.org/lasilla/instruments/wfi/index.html |archive-date=2011-09-02 |url-status=dead }}</ref> which has taken many images of celestial objects. Other instruments used are [[GROND]] (Gamma-Ray Burst Optical Near-Infrared Detector), which seeks the afterglow of gamma-ray bursts—the most powerful explosions in the universe,<ref>{{cite news |date=6 July 2007 |url=http://www.eso.org/public/news/eso0730/ |title=GROND Takes Off |publisher=ESO |access-date=2011-04-29 |archive-date=2020-05-23 |archive-url=https://web.archive.org/web/20200523172814/https://www.eso.org/public/news/eso0730/ |url-status=live }}</ref> and the high-resolution spectrograph FEROS (Fiber-fed Extended Range Optical Spectrograph), used to make detailed studies of stars.

==== Other telescopes ====

{{multiple image
 |direction = vertical
 |align = right
 |width = 225
 |image1=LaSillaByNight2.jpg
 |image2=REMTelescopeDaylight.jpg
 |caption1=The [[Euler Telescope]] and the ESO 3.6-m Telescope (background) have discovered many [[exoplanet]]s.
 |caption2=The [[Rapid Eye Mount telescope]]
}}

La Silla also hosts several national and project telescopes not operated by ESO. Among them are the Swiss Euler Telescope, the Danish National Telescope and the REM, TRAPPIST and TAROT telescopes.<ref name="National and Project Telescopes">{{cite web |url=http://www.eso.org/sci/facilities/lasilla/telescopes/national.html |title=National and Project Telescopes |access-date=2011-04-29 |archive-date=2020-05-31 |archive-url=https://web.archive.org/web/20200531155900/https://www.eso.org/sci/facilities/lasilla/telescopes/national.html |url-status=live }}</ref>
* The [[Euler Telescope]] is a 1.2-metre telescope built and operated by the [[Geneva Observatory]] in Switzerland. It is used to conduct high-precision radial velocity measurements primarily used in the search for large extrasolar planets in the southern celestial hemisphere. Its first discovery was a planet orbiting [[Gliese 86]].<ref>{{cite news|date=24 November 1998|url=http://www.eso.org/public/news/eso9855/|title=Extrasolar Planet in Double Star System Discovered from La Silla|publisher=ESO|access-date=2011-04-29|archive-date=2020-05-21|archive-url=https://web.archive.org/web/20200521205711/https://www.eso.org/public/news/eso9855/|url-status=live}}</ref> Other observing programmes focus on [[variable star]]s, [[asteroseismology]], gamma-ray bursts, monitoring [[Active galactic nucleus|active galactic nuclei]] (AGN) and [[gravitational lens]]es.<ref>{{cite web|url=http://obswww.unige.ch/exoplanets/coralie.html|title=Southern Sky extrasolar Planet search Programme|access-date=2011-10-05|archive-date=2011-09-27|archive-url=https://web.archive.org/web/20110927021703/http://obswww.unige.ch/exoplanets/coralie.html|url-status=dead}}</ref>
* The 1.54-metre ''Danish National Telescope'' was built by [[Sir Howard Grubb, Parsons and Co|Grubb-Parsons]] and has been in use at La Silla since 1979. The telescope has an [[Off-axis optical system|off-axis]] mount, and the optics are a Ritchey-Chrétien design. Because of the telescope's mount and limited space inside the dome, it has significant pointing restrictions.<ref>{{cite book |chapter-url = http://www.eso.org/sci/facilities/lasilla/telescopes/d1p5/ |chapter = The Danish Telescope at La Silla |title = The La Silla Observatory – from the Inauguration to the Future. Held 25–29 March |pages = 1 |access-date = 2011-04-29 |bibcode = 2019lsof.confE...1A |last1 = Andersen |first1 = Michael I. |journal = The la Silla Observatory - from the Inauguration to the Future |year = 2019 |doi = 10.5281/zenodo.3245240 |s2cid = 210314337 |archive-date = 2012-10-17 |archive-url = https://web.archive.org/web/20121017182659/http://www.eso.org/sci/facilities/lasilla/telescopes/d1p5/ |url-status = live }}</ref>

[[File:The Great Dane.jpg|thumb|Dome of the Danish 1.54-metre telescope that has been in operation at [[La Silla Observatory]] since 1979<ref>{{cite journal|title=The Great Dane|journal=Nature|volume=338|issue=6210|pages=27–28|url=http://www.eso.org/public/images/potw1512a/|access-date=18 June 2015|bibcode=1989Natur.338...27C|last1=Casimir|first1=H. B. G.|year=1989|doi=10.1038/338027b0|s2cid=4364680|doi-access=free|archive-date=26 June 2015|archive-url=https://web.archive.org/web/20150626183011/http://www.eso.org/public/images/potw1512a/|url-status=live}}</ref>]]
* The [[Rapid Eye Mount telescope]] is a small rapid-reaction automatic telescope with a primary {{convert|60|cm|in|adj=on}} mirror. The telescope, in an [[altazimuth mount]], began operation in October 2002. The primary purpose of the telescope is to follow the afterglow of the GRBs detected by the [[Swift Gamma-Ray Burst Mission]] satellite.<ref name="National and Project Telescopes"/><ref>{{cite web |url=http://www.rem.inaf.it/ |title=Rapid Eye Mount |access-date=2011-04-29 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114506/http://www.rem.inaf.it/ |url-status=live }}</ref>
* The Belgian [[TRAPPIST]] is a joint venture between the [[University of Liège]] and Geneva Observatory. The 0.60-metre telescope is specialised in [[comets]], exoplanets, and was one of the few telescopes that observed a [[stellar occultation]] of the dwarf planet [[Eris (dwarf planet)|Eris]], revealing that it may be smaller than [[Pluto]].<ref name=beatty>Newscientist.com, [https://www.newscientist.com/article/dn19697-former-tenth-planet-may-be-smaller-than-pluto.html Kelly Beatty – Former 'tenth planet' may be smaller than Pluto] {{Webarchive|url=https://web.archive.org/web/20120223213839/http://www.newscientist.com/article/dn19697-former-tenth-planet-may-be-smaller-than-pluto.html |date=2012-02-23 }}, November 2010</ref>
* The ''Quick-action telescope for transient objects'', [[TAROT-South robotic observatory|TAROT]], is a very fast-moving optical robotic telescope able to observe a gamma-ray burst from its beginning. Satellites detecting GRBs send signals to TAROT, which can provide a [[Minute of arc#Astronomy|sub-arc second]] position to the astronomical community. Data from the TAROT telescope is also useful in studying the evolution of GRBs, the physics of a [[Meteoroid#Fireball|fireball]] and its surrounding material.<ref>{{cite web |url=http://tarot.obs-hp.fr/tarot/ |title=TAROT website |access-date=2011-05-04 |url-status=dead |archive-url=https://web.archive.org/web/20110830125651/http://tarot.obs-hp.fr/tarot/ |archive-date=2011-08-30 }}</ref> It is operated from the [[Haute-Provence Observatory]] in France.

=== Paranal ===
{{Main|Paranal Observatory}}

The Paranal Observatory is located atop [[Cerro Paranal]] in the Atacama Desert in northern Chile. Cerro Paranal is a {{convert|2635|m|ft|adj=mid|-high}} mountain about {{convert|120|km}} south of [[Antofagasta]] and {{convert|12|km}} from the Pacific coast.<ref>{{cite web |url=http://www.eso.org/sci/facilities/paranal/site/paranal.html |title=Paranal Site Details |access-date=2011-05-04 |archive-date=2013-10-05 |archive-url=https://web.archive.org/web/20131005055420/http://www.eso.org/sci/facilities/paranal/site/paranal.html |url-status=live }}</ref>

The observatory has seven major telescopes operating in visible and infrared light: the four {{convert|8.2|m|adj=on}} telescopes of the Very Large Telescope, the {{convert|2.6|m|adj=on}} VLT Survey Telescope (VST) and the {{convert|4.1|m|adj=on}} Visible and Infrared Survey Telescope for Astronomy. In addition, there are four {{convert|1.8|m|adj=on}} auxiliary telescopes forming an array used for [[interferometric]] observations.<ref>{{cite web |url=http://www.eso.org/public/teles-instr.html |title=Telescopes and Instrumentation |access-date=2011-05-04 |archive-date=2013-09-01 |archive-url=https://web.archive.org/web/20130901034805/http://www.eso.org/public/teles-instr.html |url-status=live }}</ref> In March 2008, Paranal was the location for several scenes of the 22nd James Bond film, ''[[Quantum of Solace]]''.<ref>{{cite news |date=25 March 2008 |title=A Giant of Astronomy and a Quantum of Solace |url=http://www.eso.org/public/news/eso08007/ |publisher=ESO |access-date=2011-05-04 |archive-date=2012-04-19 |archive-url=https://web.archive.org/web/20120419194710/http://www.eso.org/public/news/eso08007/ |url-status=live }}</ref><ref>{{cite web | url = https://www.imdb.com/title/tt0830515/ | title = IMDB—Quantum of Solace (2008) | website = [[IMDb]] | access-date = 2011-05-04 | archive-date = 2011-05-01 | archive-url = https://web.archive.org/web/20110501212031/http://www.imdb.com/title/tt0830515/ | url-status = live }}</ref>

{{Panorama
| image = 360-degree Panorama of the Southern Sky.jpg
| height = 150
| caption = A 360-degree panoramic view of the southern night sky from Paranal, with telescopes in foreground
}}

==== Very Large Telescope ====
{{Main|Very Large Telescope}}
{{multiple image
 |direction = vertical
 |align     = right
 |width     = 225
 |image1    = Paranal platform.jpg
 |image2    = The VLT´s Laser Guide Star.jpg
 |caption1  = [[Very Large Telescope]] (VLT). Complex of four large telescopes and several smaller ones.
 |caption2  = VLT Laser Guide Star. The orange laser beam from the telescope is used for [[adaptive optics]].
}}

The main facility at Paranal is the VLT, which consists of four nearly identical {{convert|8.2|m|adj=on}} unit telescopes (UTs), each hosting two or three instruments. These large telescopes can also work together in groups of two or three as a giant [[Interferometry|interferometer]]. The ESO Very Large Telescope Interferometer (VLTI) allows astronomers to see details up to 25 times finer than those seen with the individual telescopes. The light beams are combined in the VLTI with a complex system of mirrors in tunnels, where the light paths must diverge less than 1/1000&nbsp;mm over 100 metres. The VLTI can achieve an [[angular resolution]] of milliarcseconds, equivalent to the ability to see the headlights of a car on the Moon.<ref>{{cite web |url=http://www.eso.org/public/teles-instr/vlt.html |title=The Very Large Telescope |access-date=2011-05-04 |archive-date=2013-08-27 |archive-url=https://web.archive.org/web/20130827183731/http://www.eso.org/public/teles-instr/vlt.html |url-status=live }}</ref>

The first of the UTs had its [[First light (astronomy)|first light]] in May 1998, and was offered to the astronomical community on 1 April 1999.<ref name="A Great Moment for Astronomy">{{cite news |date=27 May 1998 |title=A Great Moment for Astronomy |url=http://www.eso.org/public/news/eso9820/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-21 |archive-url=https://web.archive.org/web/20200521203429/https://www.eso.org/public/news/eso9820/ |url-status=live }}</ref> The other telescopes followed suit in 1999 and 2000, making the VLT fully operational. Four 1.8-metre auxiliary telescopes (ATs), installed between 2004 and 2007, have been added to the VLTI for accessibility when the UTs are used for other projects.<ref>{{cite news |date=22 December 2006 |title=Little Brother Joins the Large Family |url=http://www.eso.org/public/news/eso0651/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520092402/https://www.eso.org/public/news/eso0651/ |url-status=live }}</ref>

Data from the VLT have led to the publication of an average of more than one peer-reviewed scientific paper per day; in 2017, over 600 reviewed scientific papers were published based on VLT data.<ref name="ESOstats"/> The VLT's scientific discoveries include imaging an extrasolar planet,<ref>{{cite news |date=21 November 2008 |title=Beta Pictoris planet finally imaged? |url=http://www.eso.org/public/news/eso0842/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114538/https://www.eso.org/public/news/eso0842/ |url-status=live }}</ref> tracking individual stars moving around the [[supermassive black hole]] at the centre of the Milky Way<ref name="eso.org">{{cite news |date=10 December 2008 |title=Unprecedented 16-Year Long Study Tracks Stars Orbiting Milky Way Black Hole |url=http://www.eso.org/public/news/eso0846/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114546/https://www.eso.org/public/news/eso0846/ |url-status=live }}</ref> and observing the afterglow of the furthest known gamma-ray burst.<ref>{{cite news |date=19 September 2008 |title=NASA's Swift Catches Farthest Ever Gamma-Ray Burst |url=http://www.nasa.gov/mission_pages/swift/bursts/farthest_grb.html |publisher=NASA |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114546/https://www.nasa.gov/mission_pages/swift/bursts/farthest_grb.html |url-status=live }}</ref>

At the Paranal inauguration in March 1999, names of celestial objects in the [[Mapuche language]] were chosen to replace the technical designations of the four VLT Unit Telescopes (UT1–UT4). An essay contest was prior arranged for schoolchildren in the region concerning the meaning of these names which attracted many entries dealing with the cultural heritage of ESO's host country. A 17-year-old adolescent from [[Chuquicamata]], near [[Calama, Chile|Calama]], submitted the winning essay and was awarded an amateur telescope during the inauguration.<ref>{{cite news |date=6 March 1999 |title=VLT Unit Telescopes Named at Paranal Inauguration |url=http://www.eso.org/public/news/eso9921/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114554/https://www.eso.org/public/news/eso9921/ |url-status=live }}</ref> The four unit telescopes, UT1, UT2, UT3 and UT4, are since known as ''Antu'' (sun), ''Kueyen'' (moon), ''Melipal'' (Southern Cross), and ''Yepun'' (Evening Star),<ref>{{cite web |url=http://www.eso.org/public/teles-instr/vlt/vlt-names.html |title=Names of VLT Unit Telescopes |access-date=2011-05-04 |archive-date=2013-08-07 |archive-url=https://web.archive.org/web/20130807063615/http://www.eso.org/public/teles-instr/vlt/vlt-names.html |url-status=live }}</ref> with the latter having been originally mistranslated as "Sirius", instead of "Venus".<ref>{{cite web | url=http://www.eso.org/public/teles-instr/vlt/yepun.html | title=On the Meaning of "YEPUN" | access-date=2011-05-04 | archive-date=2010-11-10 | archive-url=https://web.archive.org/web/20101110110223/http://www.eso.org/public/teles-instr/vlt/yepun.html | url-status=live }}</ref>

==== Survey telescopes ====
{{multiple image
| direction         = vertical
| align             = right
| width             = 225
| image1            = VISTA at Paranal Eso0704b.tif
| image2            = Vst view.jpg
| caption1          = Enclosure of British developed [[VISTA (telescope)|VISTA]]
| caption2          = [[VLT Survey Telescope|VST]] seen in the back between VLT's dome-shaped auxiliary telescopes
}}

[[Visible and Infrared Survey Telescope for Astronomy]] (VISTA) is housed on the peak adjacent to the one hosting the VLT, sharing observational conditions. VISTA's main mirror is {{convert|4.1|m}} across, a highly curved mirror for its size and quality. Its deviations from a perfect surface are less than a few thousandths the thickness of a human hair, and its construction and polishing presented a challenge.<ref>{{cite news |date=11 December 2009 |title=VISTA: Pioneering New Survey Telescope Starts Work |url=http://www.eso.org/public/news/eso0949/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-21 |archive-url=https://web.archive.org/web/20200521205956/https://www.eso.org/public/news/eso0949/ |url-status=live }}</ref>

VISTA was conceived and developed by a consortium of 18 universities in the United Kingdom led by [[Queen Mary, University of London]], and it became an in-kind contribution to ESO as part of the UK's ratification agreement. The telescope's design and construction were managed by the Science and Technology Facilities Council's [[UK Astronomy Technology Centre]] (STFC, UK ATC). Provisional acceptance of VISTA was formally granted by ESO at the December 2009 ceremony at ESO headquarters in Garching, which was attended by representatives of Queen Mary, University of London and STFC. Since then the telescope has been operated by ESO,<ref>{{cite news |date=11 December 2009 |title=First stunning images captured by VISTA Telescope |url=http://www.stfc.ac.uk/News+and+Events/13651.aspx |publisher=STFC |access-date=2011-05-04 |url-status=dead |archive-url=https://web.archive.org/web/20110308055042/http://www.stfc.ac.uk/News+and+Events/13651.aspx |archive-date=8 March 2011 }}</ref> capturing quality images since it began operation.<ref>{{cite news |date=10 February 2010 |title=Orion in a New Light |url=http://www.eso.org/public/news/eso1006/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114627/https://www.eso.org/public/news/eso1006/ |url-status=live }}</ref><ref>{{cite news |date=5 January 2011 |title=VISTA Stares Deeply into the Blue Lagoon |url=http://www.eso.org/public/news/eso1101/ |publisher=ESO |access-date=2011-05-04 |archive-date=2020-05-20 |archive-url=https://web.archive.org/web/20200520114629/https://www.eso.org/public/news/eso1101/ |url-status=live }}</ref>

The [[VLT Survey Telescope]] (VST) is a state-of-the-art, {{convert|2.6|m|adj=on}} telescope equipped with OmegaCAM, a 268-megapixel CCD camera with a field of view four times the area of the full moon. It complements VISTA by surveying the sky in visible light. The VST (which became operational in 2011) is the result of a joint venture between ESO and the [[Astronomical Observatory of Capodimonte]] (Naples), a research centre at the Italian National Institute for Astrophysics [[INAF]].<ref>{{cite web|url=http://www.eso.org/public/news/eso1119/|title=First Images from the VLT Survey Telescope|access-date=2011-10-05|archive-date=2020-05-21|archive-url=https://web.archive.org/web/20200521222318/https://www.eso.org/public/news/eso1119/|url-status=live}}</ref><ref>{{cite web |url=http://vstportal.oacn.inaf.it/ |title=VLT Survey Telescope Center at Naples Web Portal |access-date=2011-05-04 |url-status=dead |archive-url=https://web.archive.org/web/20070305031627/http://vstportal.oacn.inaf.it/ |archive-date=2007-03-05 }}</ref>

The scientific goals of both surveys range from the nature of dark energy to assessing [[near-Earth object]]s. Teams of European astronomers will conduct the surveys; some will cover most of the southern sky, while others will focus on smaller areas. VISTA and the VST are expected to produce large amounts of data; a single picture taken by VISTA has 67&nbsp;megapixels, and images from OmegaCam (on the VST) will have 268&nbsp;megapixels. The two survey telescopes collect more data every night than all the other instruments on the VLT combined. The VST and VISTA produce more than 100 terabytes of data per year.<ref>{{cite web |url=http://www.eso.org/public/teles-instr/surveytelescopes.html |title=The ESO Survey Telescopes |access-date=2011-05-04 |archive-date=2013-09-01 |archive-url=https://web.archive.org/web/20130901065634/http://www.eso.org/public/teles-instr/surveytelescopes.html |url-status=live }}</ref>

=== Llano de Chajnantor ===
{{Main|Llano de Chajnantor Observatory}}
{{multiple image
 |direction = vertical
 |align = right
 |width = 225
 |image1=Three ALMA antennas close together on Chajnantor.jpg
 |caption1=Three [[Atacama Large Millimeter Array|ALMA]] antennas on Chajnantor
 |alt1=Three large parabolic-dish telescopes, seen from behind
 |image2=ALMA antenna en route.jpg
 |caption2=ALMA antenna on route to Chajnantor plateau
 |alt2=Large white parabolic-dish antenna on yellow, multi-wheeled vehicle
}}

The Llano de Chajnantor is a {{convert|5100|m|ft|adj=mid|-high}} plateau in the Atacama Desert, about {{convert|50|km}} east of [[San Pedro de Atacama]]. The site is {{convert|750|m}} higher than the [[Mauna Kea Observatory]] and {{convert|2400|m}} higher than the [[Very Large Telescope]] on [[Cerro Paranal]]. It is dry and inhospitable to humans, but a good site for [[submillimetre astronomy]]; because [[water vapour]] molecules in [[Earth's atmosphere]] absorb and attenuate [[submillimetre radiation]], a dry site is required for this type of [[radio astronomy]].<ref>{{cite web
|url=http://www.alma.nrao.edu/projectbk/construction/chap14/chap14.html
|title=ALMA Site Characterization and Monitoring
|access-date=2011-10-05
|archive-date=2012-04-25
|archive-url=https://web.archive.org/web/20120425050101/http://www.alma.nrao.edu/projectbk/construction/chap14/chap14.html
|url-status=live
}}</ref> The telescopes are:
* [[Atacama Cosmology Telescope]] (ACT; not operated by ESO)
* [[Atacama Pathfinder Experiment]] (Operated on behalf of the Max Planck Institute for Radio Astronomy (MPIfR))
* [[Atacama Large Millimeter Array]]
* [[QUIET|Q/U Imaging Experiment]] (QUIET; not operated by ESO) <!-- Though the Wikipedia article is horribly outdated -->
* [[POLARBEAR]] (on the Huan Tran Telescope; not operated by ESO)

ALMA is a telescope designed for millimetre and submillimetre astronomy. This type of astronomy is a relatively unexplored frontier, revealing a universe which cannot be seen in more-familiar visible or infrared light and ideal for studying the "cold universe"; light at these wavelengths shines from vast cold clouds in interstellar space at temperatures only a few tens of degrees above [[absolute zero]]. Astronomers use this light to study the chemical and physical conditions in these [[molecular cloud]]s, the dense regions of gas and cosmic dust where new stars are being born. Seen in visible light, these regions of the universe are often dark and obscure due to dust; however, they shine brightly in the millimetre and submillimetre portions of the [[electromagnetic spectrum]]. This wavelength range is also ideal for studying some of the earliest (and most distant) galaxies in the universe, whose light has been [[redshift]]ed into longer wavelengths from the expansion of the universe.<ref>{{cite web |url=http://www.eso.org/public/teles-instr/apex.html |title=ESO APEX |access-date=2011-05-03 |archive-date=2011-06-22 |archive-url=https://web.archive.org/web/20110622023612/http://www.eso.org/public/teles-instr/apex.html |url-status=live }}</ref><ref>{{cite web |url=https://almascience.nrao.edu/about-alma/alma-site |title=ALMA Site – ALMA Science Portal |access-date=2011-05-04 |archive-date=2020-05-17 |archive-url=https://web.archive.org/web/20200517003409/https://almascience.nrao.edu/about-alma/alma-site |url-status=live }}</ref>

==== Atacama Pathfinder Experiment ====

ESO hosts the Atacama Pathfinder Experiment, APEX, and operates it on behalf of the [[Max Planck Institute for Radio Astronomy]] (MPIfR). APEX is a {{convert|12|m|adj=on}} diameter telescope, operating at millimetre and submillimetre wavelengths—between infrared light and radio waves.

==== Atacama Large Millimeter/submillimeter Array ====
{{Main|Atacama Large Millimeter Array}}

ALMA is an astronomical interferometer initially composed of 66 high-precision antennas and operating at wavelengths of 0.3 to 3.6&nbsp;mm. Its main array will have 50 {{convert|12|m|adj=on}} antennas acting as a single [[interferometer]]. An additional compact array of four 12-metre and twelve {{convert|7|m|adj=on}} antennas, known as the Morita array is also available.<ref>{{Cite web |last=information@eso.org |date=2013-05-07 |title=ALMA Compact Array Completed and Named After Japanese Astronomer |url=https://www.eso.org/public/announcements/ann13040/ |access-date=2023-05-14 |website=www.eso.org |language=en}}</ref> The antennas can be arranged across the desert plateau over distances from 150 metres to {{convert|16|km}}, which will give ALMA a variable "zoom". The array will be able to probe the universe at millimetre and submillimeter wavelengths with unprecedented sensitivity and resolution, with vision up to ten times sharper than the [[Hubble Space Telescope]]. These images will complement those made with the [[VLT Interferometer]].<ref>{{cite web |url=http://www.eso.org/public/teles-instr/alma.html |title=ESO ALMA |access-date=2011-05-04 |archive-date=2013-08-10 |archive-url=https://web.archive.org/web/20130810124241/http://www.eso.org/public/teles-instr/alma.html |url-status=live }}</ref> ALMA is a collaboration between East Asia (Japan and [[Taiwan]]), Europe (ESO), North America (US and Canada) and Chile.

The scientific goals of ALMA include studying the origin and formation of stars, galaxies, and planets with observations of molecular gas and dust, studying distant galaxies towards the edge of the observable universe and studying [[Cosmic microwave background radiation|relic radiation]] from the [[Big Bang]].<ref>{{cite web |url=https://almascience.nrao.edu/alma-science |title=ALMA Science—ALMA Science Portal |access-date=2011-05-04 |archive-date=2020-05-17 |archive-url=https://web.archive.org/web/20200517003426/https://almascience.nrao.edu/alma-science |url-status=live }}</ref> A call for ALMA science proposals was issued on 31 March 2011,<ref>{{cite web |url=https://almascience.nrao.edu/call-for-proposals |title=Call for Proposals—ALMA Science Portal |access-date=2011-05-04 |url-status=dead |archive-url=https://web.archive.org/web/20111114071735/https://almascience.nrao.edu/call-for-proposals |archive-date=2011-11-14 }}</ref> and early observations began on 3 October.<ref>{{cite news |title=ALMA Early Science Cycle 0 Call for Proposals |url=https://science.nrao.edu/facilities/alma |publisher=NRAO |access-date=2011-05-04 |archive-date=2011-07-25 |archive-url=https://web.archive.org/web/20110725223434/https://science.nrao.edu/facilities/alma |url-status=live }}</ref><ref>{{cite web|url=http://www.eso.org/public/news/eso1137/|title=ALMA Opens its Eyes|access-date=2011-10-05|archive-date=2011-10-05|archive-url=https://web.archive.org/web/20111005095244/http://www.eso.org/public/news/eso1137/|url-status=live}}</ref>

== Outreach ==
[[File:Artist’s impression of ESO Supernova Planetarium & Visitor Centre.jpg|thumb|Artist's impression of [[ESO Supernova Planetarium & Visitor Centre]]<ref>{{cite news|title=Groundbreaking Ceremony for ESO Supernova Planetarium & Visitor Centre|url=http://www.eso.org/public/announcements/ann15011/|access-date=27 February 2015|work=ESO Announcement|agency=European Southern Observatory|archive-date=20 May 2020|archive-url=https://web.archive.org/web/20200520095639/https://www.eso.org/public/announcements/ann15011/|url-status=live}}</ref>]]

Outreach activities are carried out by the ESO education and Public Outreach Department (ePOD).<ref>{{cite web|url=http://www.eso.org/public/outreach/department.html|title=ESO ePOD|access-date=2011-10-06|archive-date=2013-09-01|archive-url=https://web.archive.org/web/20130901152853/http://www.eso.org/public/outreach/department.html|url-status=live}}</ref> 

ePOD also manages the [[ESO Supernova Planetarium & Visitor Centre]], an astronomy centre located at the site of the ESO Headquarters in Garching bei München, which was inaugurated 26 April 2018.<ref>{{cite web|url=http://supernova.eso.org/|title=ESO Supernova website|access-date=2016-06-08|archive-date=2020-06-04|archive-url=https://web.archive.org/web/20200604145719/https://supernova.eso.org/|url-status=live}}</ref>

== Video gallery ==
<gallery class="center" mode="packed" heights="100">
File:ESO’s 50th Anniversary Gala Event.ogv|ESO's 50th-anniversary event (''[[Munich Residenz]] in Germany, 11 October 2012'')
File:Europe to the Stars bite-size.ogv|ESO's first 50 years of exploring the southern sky
File:Visit of José Manuel Barroso to the VLT.ogv|[[José Manuel Barroso]] visits the ESO in January 2013.
File:ESO and its 50th Anniversary, by ESO Director General, Tim de Zeeuw.ogg|[[Tim de Zeeuw]] talks on ESO and its 50th anniversary.
File:Making Way for Construction of the ESO Supernova.ogg|The temporary office buildings at the ESO headquarters in Garching being dismantled
File:ESO Timelapse Compilation.ogg|Timelapses of ESO's [[Very Large Telescope|VLT]], [[Atacama Large Millimeter Array|ALMA]] and [[La Silla Observatory|La Silla site]]
</gallery>

== See also ==
{{cmn|
* [[Cerro Tololo Inter-American Observatory]], U.S. main site in Chile
* [[Extremely Large Telescope]], ESO's largest telescope under construction
* [[European Northern Observatory]], name of a Portuguese group of observatories which is a [[word play]] on ESO
* [[Roque de los Muchachos Observatory]], telescopes on the Canary Islands, Spain
* [[Teide Observatory]], telescopes on the Canary Islands, Spain
* [[CERN]]
* [[HD 155448]]
* [[Paolo Padovani]]
* [[Simone Zaggia]]
* [[VVV Survey]]
}}

== References ==
{{reflist|30em}}

== Bibliography ==
* {{cite journal |last=Shaw |first=E. N. |date=1976 |title=The European Southern Observatory |journal=The Observatory |publisher=Royal Astronomical Society |location=London}}
* {{cite book |author=Council of Europe |date=2010 |url= https://books.google.com/books?id=_SAFci-FqBsC&pg=PR443 |title=European Yearbook / Annuaire Européen |volume=58 |publisher=Martinus Nijhoff Publishers |isbn=978-9004206793 |page=cdxliii}}
* {{cite book |last=Lodewijk |first=Woltjer |date=2012 |title=Europe's Quest for The Universe |publisher=EDP Sciences |isbn=9782759801671}}
* {{cite book |last1=Schilling |first1=Govert |last2=Christensen |first2=Lars Lindberg |date=2013 |title=Europe to the Stars: ESO's first 50 years of exploring the southern sky |publisher=John Wiley & Sons |isbn=9783527671670}}

== External links ==
{{Commons}}
* [https://www.eso.org/ ESO]

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