Editing European Southern Observatory (section)

== 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>