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The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an 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 about 730 staff members and receives annual member state contributions of approximately €162 million. Its observatories are located in northern Chile. ESO has built and operated some of the largest and most technologically advanced telescopes. These include the 3.6 m New Technology Telescope, an early pioneer in the use of
active optics Active optics is a technology used with reflecting telescopes developed in the 1980s, which actively shapes a telescope's mirrors to prevent deformation due to external influences such as wind, temperature, and mechanical stress. Without active op ...
, 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 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. Currently under construction is the
Extremely Large Telescope The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observator ...
. It will use a 39.3-metre-diameter segmented mirror, and become the world's largest optical reflecting telescope when operational in 2024. Its light-gathering power will allow detailed studies of planets around other stars, the first objects in the universe, supermassive black holes, 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
astronomical catalogues An astronomical catalog or catalogue is a list or tabulation of astronomical objects, typically grouped together because they share a common type, morphology, origin, means of detection, or method of discovery. The oldest and largest are star c ...
. Its findings include the discovery of the most distant gamma-ray burst and evidence for a
black hole A black hole is a region of spacetime where gravitation, gravity is so strong that nothing, including light or other Electromagnetic radiation, electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts t ...
at the centre of the Milky Way. In 2004, the VLT allowed astronomers to obtain the first picture of an extrasolar planet (
2M1207b 2M1207b is a planetary-mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth.
) orbiting a brown dwarf 173 light-years away. The High Accuracy Radial Velocity Planet Searcher (
HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...
) instrument installed on the older ESO 3.6 m telescope led to the discovery of extrasolar planets, including
Gliese 581c Gliese 581c (Gl 581c or GJ 581c) is a planet orbiting within the Gliese 581 system. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.5 times that of the Earth, it is classified as a s ...
—one of the smallest planets seen outside the Solar System.


History

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. It was pursued by Oort, who gathered a group of astronomers in Leiden to consider it on June 21 that year. Immediately thereafter, the subject was further discussed at the Groningen conference in the Netherlands. On January 26, 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. At the time, all reflector telescopes 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. Although it was initially planned to set up telescopes in South Africa (where several European observatories were located), tests from 1955 to 1963 demonstrated that a site in the Andes was preferable. On November 15, 1963 Chile was chosen as the site for ESO's observatory. The decision was preceded by the ESO Convention, signed 5 October 1962 by Belgium, Germany, France, the Netherlands and Sweden.
Otto Heckmann Otto Hermann Leopold Heckmann (June 23, 1901 – May 13, 1983) was a German astronomer. He directed the Hamburg Observatory from 1941 to 1962, after which he became the first director of the European Southern Observatory. He actively contrib ...
was nominated as the organisation's first director general on 1 November 1962. 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, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in a northwestern suburb of Gene ...
(the European Organization for Nuclear Research) highlighted the need for a convention between governments (in addition to organisations). 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. In 1966, the first ESO telescope at the La Silla site in Chile began operating. 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. ESO's European departments moved into the new ESO headquarters in
Garching Garching bei München (''Garching near Munich'') or Garching is a town in Bavaria, Germany, near Munich. It is the home of several research institutes and university departments on its campus. It became a city on 14 September 1990. Location The ...
(near Munich), Germany in 1980.


Member states


Chilean observation sites

Although ESO is headquartered in Germany, its telescopes and observatories are in northern Chile, where the organisation operates advanced ground-based astronomical facilities: *
La Silla La Silla may refer to: * La Silla Observatory, an astronomical observatory in Chile * Cerro de la Silla, a mountain and natural monument located within the metropolitan area of the city of Monterrey, Nuevo León, in northeastern Mexico. * La Sill ...
, which hosts the New Technology Telescope (NTT) *
Paranal Cerro Paranal is a mountain in the Atacama Desert of northern Chile and is the home of the Paranal Observatory. Prior to the construction of the observatory, the summit was a horizontal control point with an elevation of ; now it is above sea ...
, where the Very Large Telescope (VLT) is located * Llano de Chajnantor, which hosts the APEX ( Atacama Pathfinder Experiment) submillimetre telescope and where ALMA, the Atacama Large Millimeter/submillimeter Array, is located These are among the best locations for astronomical observations in the southern hemisphere. An ESO project is the
Extremely Large Telescope The Extremely Large Telescope (ELT) is an astronomical observatory currently under construction. When completed, it is planned to be the world's largest optical/near-infrared extremely large telescope. Part of the European Southern Observator ...
(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. Construction work at the ELT site started in June 2014. As decided by the ESO council on 26 April 2010, a fourth site ( Cerro Armazones) is to be home to ELT. 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. 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 million images (or spectra) with a total volume of about 65 terabytes (65,000,000,000,000 bytes) of data.


La Silla

La Silla, located in the southern Atacama Desert north of Santiago de Chile at an altitude of , 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. 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 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. Several telescopes at La Silla played a role in linking gamma-ray bursts, the most energetic explosions in the universe since the
Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...
, with the explosions of massive stars. The ESO La Silla Observatory also played a role in the study of supernova SN 1987A.


ESO 3.6-metre telescope

The ESO 3.6-metre telescope began operations in 1977. It has been upgraded, including the installation of a new secondary mirror. The conventionally designed horseshoe-mount telescope was primarily used for infrared
spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter wa ...
; it now hosts the HARPS spectrograph, used in search of
extra-solar planets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
and for
asteroseismology Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature ...
. The telescope was designed for very high long-term
radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the temporal rate of change, rate of change of the distance or Slant range, range between the two points. It is e ...
accuracy (on the order of 1 m/s).


New Technology Telescope

The New Technology Telescope (NTT) is an altazimuth, 3.58-metre
Ritchey–Chrétien telescope A Ritchey–Chrétien telescope (RCT or simply RC) is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors (coma). The RCT has a wi ...
, 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 Active optics is a technology used with reflecting telescopes developed in the 1980s, which actively shapes a telescope's mirrors to prevent deformation due to external influences such as wind, temperature, and mechanical stress. Without active op ...
) is now applied to all major telescopes, including the VLT and the future ELT. 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.


MPG/ESO 2.2-metre 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 The Max Planck Society for the Advancement of Science (german: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes. ...
(''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 as large as the full moon, 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, and the high-resolution spectrograph FEROS (Fiber-fed Extended Range Optical Spectrograph), used to make detailed studies of stars.


Other telescopes

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. * 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 Gliese 86 (13 G. Eridani, HD 13445) is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observ ...
. Other observing programmes focus on variable stars,
asteroseismology Asteroseismology or astroseismology is the study of oscillations in stars. Stars have many resonant modes and frequencies, and the path of sound waves passing through a star depends on the speed of sound, which in turn depends on local temperature ...
, gamma-ray bursts, monitoring active galactic nuclei (AGN) and gravitational lenses. * The 1.54-metre ''Danish National Telescope'' was built by Grubb-Parsons and has been in use at La Silla since 1979. The telescope has an 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. * The
Rapid Eye Mount telescope The Rapid Eye Mount telescope (REM) is a fully automatic, 60 cm aperture telescope located at ESO's La Silla Observatory at 2,400 metres altitude on the edge of the Atacama Desert in Chile. The telescope's aim is to catch the afterglows of gam ...
is a small rapid-reaction automatic telescope with a primary mirror. The telescope, in an
altazimuth mount An altazimuth mount or alt-azimuth mount is a simple two-axis mount for supporting and rotating an instrument about two perpendicular axes – one vertical and the other horizontal. Rotation about the vertical axis varies the azimuth (compass bea ...
, 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. * 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, revealing that it may be smaller than Pluto.Newscientist.com
Kelly Beatty – Former 'tenth planet' may be smaller than Pluto
November 2010
* The ''Quick-action telescope for transient objects'', 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 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
fireball Fireball may refer to: Science * Fireball (meteor), a brighter-than-usual meteor * Ball lightning, an atmospheric electrical phenomenon * ''Bassia scoparia'', a plant species Arts and entertainment Films * ''The Fireball'', a 1950 film starring ...
and its surrounding material. It is operated from the
Haute-Provence Observatory The Haute-Provence Observatory (OHP, french: Observatoire de Haute-Provence) is an astronomical observatory in the southeast of France, about 90 km east of Avignon and 100 km north of Marseille. It was established in 1937 as a national ...
in France.


Paranal

The Paranal Observatory is located atop
Cerro Paranal Cerro Paranal is a mountain in the Atacama Desert of northern Chile and is the home of the Paranal Observatory. Prior to the construction of the observatory, the summit was a horizontal control point with an elevation of ; now it is above sea ...
in the Atacama Desert in northern Chile. Cerro Paranal is a mountain about south of Antofagasta and from the Pacific coast. The observatory has seven major telescopes operating in visible and infrared light: the four telescopes of the Very Large Telescope, the VLT Survey Telescope (VST) and the Visible and Infrared Survey Telescope for Astronomy. In addition, there are four auxiliary telescopes forming an array used for
interferometric Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
observations. In March 2008, Paranal was the location for several scenes of the 22nd James Bond film, ''
Quantum of Solace ''Quantum of Solace'' is a 2008 spy film and the twenty-second in the List of James Bond films, ''James Bond'' series produced by Eon Productions. It is the sequel to Casino Royale (2006 film), ''Casino Royale'' (2006). Directed by Marc Forst ...
''.


Very Large Telescope

The main facility at Paranal is the VLT, which consists of four nearly identical 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
interferometer Interferometry is a technique which uses the ''interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber op ...
. 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 mm over 100 metres. The VLTI can achieve an
angular resolution Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. ...
of milliarcseconds, equivalent to the ability to see the headlights of a car on the moon. The first of the UTs had its first light in May 1998, and was offered to the astronomical community on 1 April 1999. The other telescopes followed suit in 1999 and 2000, 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. 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. The VLT's scientific discoveries include imaging an extrasolar planet, tracking individual stars moving around the supermassive black hole at the centre of the Milky Way and observing the afterglow of the furthest known gamma-ray burst. 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, submitted the winning essay and was awarded an amateur telescope during the inauguration. The four unit telescopes, UT1, UT2, UT3 and UT4, are since known as ''Antu'' (sun), ''Kueyen'' (moon), ''Melipal'' (Southern Cross), and ''Yepun'' (Evening Star), with the latter having been originally mistranslated as "Sirius", instead of "Venus".


Survey telescopes

Visible and Infrared Survey Telescope for Astronomy The VISTA (Visible and Infrared Survey Telescope for Astronomy) is a wide-field reflecting telescope with a 4.1 metre mirror, located at the Paranal Observatory in Chile. It is operated by the European Southern Observatory and started science op ...
(VISTA) is housed on the peak adjacent to the one hosting the VLT, sharing observational conditions. VISTA's main mirror is 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. 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, capturing quality images since it began operation. The
VLT Survey Telescope The VLT Survey Telescope (VST) is a telescope located at ESO’s Paranal Observatory in the Atacama Desert of northern Chile. It is housed in an enclosure immediately adjacent to the four Very Large Telescope (VLT) Unit Telescopes on the summit o ...
(VST) is a state-of-the-art, 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 The Astronomical Observatory of Capodimonte ( it, Osservatorio Astronomico di Capodimonte, italic=no) is the Neapolitan department of Istituto Nazionale di Astrofisica (National Institute for Astrophysics, INAF), the most important Italian institu ...
(Naples), a research centre at the Italian National Institute for Astrophysics
INAF The National Institute for Astrophysics ( it, Istituto Nazionale di Astrofisica, or INAF) is an Italian research institute in astronomy and astrophysics, founded in 1999. INAF funds and operates twenty separate research facilities, which in turn e ...
. The scientific goals of both surveys range from the nature of dark energy to assessing near-Earth objects. 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 megapixels, and images from OmegaCam (on the VST) will have 268 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.


Llano de Chajnantor

The Llano de Chajnantor is a plateau in the Atacama Desert, about east of San Pedro de Atacama. The site is higher than the Mauna Kea Observatory and higher than the Very Large Telescope on
Cerro Paranal Cerro Paranal is a mountain in the Atacama Desert of northern Chile and is the home of the Paranal Observatory. Prior to the construction of the observatory, the summit was a horizontal control point with an elevation of ; now it is above sea ...
. 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 Terahertz radiation – also known as submillimeter radiation, terahertz waves, tremendously high frequency (THF), T-rays, T-waves, T-light, T-lux or THz – consists of electromagnetic waves within the ITU-designated band of frequ ...
, a dry site is required for this type of radio astronomy. The telescopes are: *
Atacama Cosmology Telescope The Atacama Cosmology Telescope (ACT) is a cosmological millimeter-wave telescope located on Cerro Toco in the Atacama Desert in the north of Chile. ACT makes high-sensitivity, arcminute resolution, microwave-wavelength surveys of the sky in ord ...
(ACT; not operated by ESO) * Atacama Pathfinder Experiment * Atacama Large Millimeter Array * Q/U Imaging Experiment (QUIET; not operated by ESO) * POLARBEAR (on the Huan Tran Telescope; not operated by ESO) APEX and ALMA are telescopes 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 Absolute zero is the lowest limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, taken as zero kelvin. The fundamental particles of nature have minimum vibration ...
. Astronomers use this light to study the chemical and physical conditions in these molecular clouds, 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 In physics, a redshift is an increase in the wavelength, and corresponding decrease in the frequency and photon energy, of electromagnetic radiation (such as light). The opposite change, a decrease in wavelength and simultaneous increase in f ...
ed into longer wavelengths from the expansion of the universe.


Atacama Pathfinder Experiment

The Atacama Pathfinder Experiment telescope is operated by ESO in collaboration with the Max Planck Institute for Radio Astronomy in Bonn, Germany and the Onsala Space Observatory in Onsala, Sweden. It is a -diameter telescope operating at millimetre and submillimetre wavelengths, the largest of its kind in the southern hemisphere. APEX is a precursor of ALMA (the Atacama Large Millimeter Array), an astronomical interferometer which ESO and its international partners is building on the Chajnantor plateau. APEX is based on a prototype ALMA antenna that is modified to be operated as single dish radio telescope.


Atacama Large Millimeter/submillimeter Array

ALMA is an astronomical interferometer of innovative design, initially composed of 66 high-precision antennas and operating at wavelengths of 0.3 to 3.6 mm. Its main array will have 50 antennas acting as a single interferometer. An additional compact array of four 12-metre and twelve antennas is also planned. The antennas can be arranged across the desert plateau over distances from 150 metres to , 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. ALMA is a collaboration between East Asia (Japan and Taiwan), Europe (ESO), North America (USA 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 The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...
. A call for ALMA science proposals was issued on 31 March 2011, and early observations began on 3 October.


ESO telescopes: research and discoveries


Search for extrasolar planets

"Is there life elsewhere in the universe?" is one of humankind's most profound unanswered questions. A step in the attempt to answer this question is the search for planets outside the Solar System. ESO's observatories are equipped with an arsenal of instruments for finding, studying, and monitoring extrasolar planets. In 2004, the Very Large Telescope detected a faint glow from an apparent planet orbiting a star about 200 light-years from earth. A year later, this detection was confirmed as the first picture of an exoplanet ever recorded. Although the planet is large (five times more massive than Jupiter), this observation is a first step toward identifying the physical structure and chemical composition of exoplanets. Despite the fact that planets seem very common in the universe they are tiny, faint objects at cosmic scales; this makes their detection difficult with current technology. For this reason, most exoplanets have been detected with indirect methods. Of these, the most successful has been the radial velocity method. HARPS (the High Accuracy Radial-velocity Planet Searcher) has allowed the discovery of a number of planets with masses below that of Neptune orbiting nearby stars. However, few of these planets are among the smallest ever discovered, or reside in its star's habitable zone. The possibility exists that one of these planets is covered by oceans; this discovery is an encouraging result in the search for planets which could support life. The Danish 1.54-metre telescope at La Silla participated in the discovery of one of the most Earth-like planets found to date. The planet, detected using the microlensing technique and about five times as massive as Earth, circles its parent star in about 10 years and most certainly has a rocky and icy surface. In 2017, Breakthrough Initiatives and the European Southern Observatory (ESO) entered a collaboration to enable and implement a search for habitable planets in the nearby star system, Alpha Centauri. The agreement involves Breakthrough Initiatives providing funding for an upgrade to the VISIR (VLT Imager and Spectrometer for mid-Infrared) instrument on ESO's Very Large Telescope (VLT) in Chile. This upgrade will greatly increase the likelihood of planet detection in the system. In August 2016, the European Southern Observatory announced the detection of a planet orbiting the third star in the Alpha Centauri system, Proxima Centauri. The planet, called Proxima Centauri b, could be a potential target for one of the projects of Breakthrough Initiatives. Breakthrough Starshot is a proof of concept mission to send a fleet of ultra-fast light-driven nanocraft to explore the Alpha Centauri star system, which could pave the way for a first launch within the next generation. An objective of the mission would be to make a fly-by of and possibly photograph any Earth-like worlds that might exist in the system. In March 2019, ESO astronomers, employing the Very Large Telescope#Instruments, GRAVITY instrument on their Very Large Telescope, Very Large Telescope Interferometer (VLTI), announced the first Methods of detecting exoplanets, direct detection of an exoplanet, HR 8799 e, using Interferometry, optical interferometry.


Age of the universe

With the Very Large Telescope, astronomers have made an independent determination of the age of the universe and shed new light on the earliest stages of the Milky Way. For the first time, they measured the amount of the radioactive isotope uranium-238 in a star born when the Milky Way was still forming. Like carbon dating over longer timescales, the uranium clock measures the age of a star. It shows that this star is 12.5 billion years old. Because the star cannot be older than the universe itself, the universe must be older than this. This agrees with known cosmology, which gives an age of the universe of 13.8 billion years. The star (and the Milky Way) must have formed soon after the Big Bang. Another result is the first measurement of the beryllium content of two stars in a Milky Way globular cluster. With this measurement, astronomers found that the first generation of stars in our galaxy must have formed soon after the end of the 200-million-year "Chronology of the universe#Dark Ages, Dark Age" following the Big Bang.


Milky Way black hole

Astronomers long suspected that a black hole exists at the center of the Milky Way, but their theory was unproven. Conclusive evidence was obtained after 16 years of monitoring the Galactic Center with ESO telescopes at the La Silla and Paranal observatories. Stars at the centre of the Milky Way are so densely packed that special imaging techniques (such as adaptive optics) were needed to boost the resolution of the VLT. Thanks to these techniques, astronomers were able to watch individual stars with unprecedented accuracy as they circled the Galactic Center. Their paths conclusively demonstrated that they were orbiting in the immense gravitational grip of a supermassive black hole nearly three million times more massive than the sun. The VLT observations also revealed flashes of infrared light emerging from the region at regular intervals. While the cause of this phenomenon is unknown, observers have suggested that the black hole may be spinning rapidly. The VLT has also peered into the centre of galaxies beyond our own, where clear signs of activity produced by supermassive black holes are found. In the active galaxy NGC 1097, a complex network of filaments spiraling from the main part of the galaxy to its centre was seen in great detail.


Gamma-ray bursts

Gamma-ray bursts (GRBs) are bursts of highly energetic gamma rays lasting from less than one second to several minutes. They are known to occur at great distances from earth, near the limits of the observable universe. The VLT has observed the afterglow of the farthest known gamma-ray burst. With a measured redshift of 8.2, the light from this very remote astronomical source has taken more than 13 billion years to reach the earth. It occurred when the universe was less than 600 million years old (less than five percent of its present age), and released 300 times as much energy in a few seconds as the sun will in its entire lifetime (more than 10 billion years). The nature of these explosions has long been a mystery. Observations show that GRBs are one of two types: short- (less than a few seconds) and long-duration. Until 2003, it was suspected that two different types of cosmic event caused them. In 2003, ESO telescopes followed the aftermath of an explosion for one month. Their data showed that the light had similar properties to that of a supernova, and allowed astronomers to link long-duration GRBs with the ultimate explosions of massive stars (hypernovae). In 2005, ESO telescopes detected visible light after a short-duration burst and tracked this light for three weeks. The conclusion was that short-duration bursts could not be caused by a hypernova; instead, it is thought that they originate in the violent merges of neutron stars or black holes. Observations of gamma-ray-burst afterglows were coordinated between the VLT and the Atacama Pathfinder Experiment (APEX) to identify the possible counterpart (and its decay) at submillimeter wavelengths.


Digital archives

The Science Archive Operation Group receives and redistributes ESO data and provides archival support. About 200 Terabytes (TB) of public data are distributed per year through the ESO archive. The archive is about 1.01 Petabytes (PB), with an input rate of about 131 TB per year; this is being increased by a factor of 10 or so due to the survey telescopes' data-production rate. Breakthroughs in telescope, detector and computer technology now allow astronomical surveys to produce large numbers of images, spectra and catalogues. These data sets cover the sky at all wavelengths, from gamma- and X-rays through optical, infrared and radio waves. Astronomers are developing ways to make the large amount of data easily accessible. These techniques use the grid paradigm of distributed computing with seamless, transparent access to data through virtual observatories (VOs). As a physical observatory has telescopes with unique astronomical instruments, a VO consists of data centres with unique collections of astronomical data, software systems and processing capabilities. This global, community-based initiative is being developed under the International Virtual Observatory Alliance and in Europe as part of the EURO-VO project. VOs have proven their effectiveness in a number of ways, including discovering 31 optically faint, obscured quasar candidates in existing Great Observatories Origins Deep Survey (GOODS) fields (quadrupling the number previously found). The discovery means that surveys of supermassive black holes have underestimated their numbers by a factor of two to five.


Major discoveries

; Proxima Centauri b, the closest potentially habitable exoplanet : An ESO team led by Guillem Anglada-Escudé found Proxima Centauri b. The discovery was reported in ''Nature'' on 24 August 2016. ; Stars orbiting Milky Way black hole : Several of ESO telescopes were used in a 16-year study to obtain the most detailed view to date of the surroundings of the Galactic Center#Supermassive black hole, supermassive black hole at the centre of the galaxy. ; Accelerating universe : Two independent research teams have shown that the universe's expansion is Accelerating universe, accelerating, based on exploding-star observations with astronomical telescopes at La Silla. The research teams were awarded the 2011 Nobel Prize in Physics for their discovery. ; Oldest known Milky Way star : Using ESO's VLT, astronomers have measured the age of the NGC 6397, oldest known star in the Milky Way. At 13.2 billion years, the star was born in the universe's earliest era of star formation. However, the oldest star seems to be 13.6 billion years old, and the Methuselah star might be even older. ; Measuring exoplanet spectra and atmosphere : The atmosphere around an exoplanet has been analysed for the first time with the VLT. The planet, GJ 1214b, was studied as it passed in front of its parent star and starlight passed through the planet's atmosphere. ; First image of exoplanet : The VLT has obtained the 2M1207, first image of a planet outside the Solar System. The 5-Jupiter-mass planet orbits a failed star—a brown dwarf—at a distance of 55 times the mean Earth-Sun distance. ; Rich planetary system : Astronomers using
HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...
have discovered a planetary system (with at least five planets) orbiting a sunlike star, HD 10180. Two other planets may be present, one of which would have the lowest mass ever found. ; Supermassive black hole flares at Milky Way centre : The VLT and APEX collaborated to study violent flares from the supermassive black hole at the centre of the Milky Way, revealing material stretched as it orbits in the intense gravitational field near the central black hole. ; Gamma-ray bursts : ESO telescopes have provided proof that long gamma-ray bursts are linked with the Supernova, explosion of massive stars; short gamma-ray bursts seem to be produced by merging neutron stars. ; Milky Way stellar motion : After more than 1,000 nights of observation at La Silla over a 15-year period, astronomers have determined the motion of more than 14,000 sunlike stars in the vicinity of the sun (demonstrating that the Milky Way is more turbulent and chaotic than previously thought). ; Cosmic-temperature measurements : The VLT has detected, for the first time, carbon-monoxide molecules in a galaxy located almost 11 billion light-years away. This has allowed astronomers to obtain a precise measurement of cosmic temperature at such a remote location.


Outreach

Outreach activities are carried out by the ESO education and Public Outreach Department (ePOD). These include a range of programs and products that aim to meet the requirements of media, science communicators and the public, such as press releases, images, videos and printed material. Events such as the 2009 International Year of Astronomy (IYA2009) (with IAU and UNESCO), VLT First Light, Astronomy Online and the Comet Shoemaker–Levy 9 impact, have been reported by the Department. ePOD organises exhibitions and educational campaigns, such as Transit of Venus, Venus Transit, Science on Stage Europe, Science on Stage and Science in School. 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. A collection of photos and videos can be found in the ESO Public Image Gallery and Video Library. Products from educational material to press kits may be downloaded from the ePOD website or ordered in physical form. As part of the Department, European outreach for the NASA/ESA Hubble Space Telescope provides comprehensive information about the telescope and its scientific discoveries. The International Astronomical Union (IAU) Press Office is also hosted by ePOD.


Publications

The ESO Annual Report details activities across the organisation and outlines scientific, technical and organisational highlights. All issues dating back to the first report in 1964 are available for download. ESO press releases describe scientific, technical and organisational developments and achievements and results obtained by scientists with ESO facilities. The organisation publishes three types of press releases. Science releases describe results (usually appearing in a peer-reviewed journal) involving data from ESO observatories or staff. Organisational releases cover a range of themes related to ESO operations, including news on current and future observatories, new astronomical instruments and announcements of exhibitions worldwide. ESO also selects its best astronomical images, and presents them publicly in periodic photo releases. All press releases (dating back to 1985) are available online. There are child-friendly versions and press releases translated into the languages of ESO's member countries. The Messenger (astronomy magazine), The Messenger is a quarterly journal which has presented ESO's activities to the public since May 1974. All back copies are available for download. ESO also publishes announcements and Pictures of the Week on its website. Announcements are shorter than press releases (typically less than 200 words) highlighting stories and events of interest to the community. Pictures of the Week show beautiful (or interesting) photos from ESO telescopes, and may highlight recent events or archival photos. All former entries are available on the website. ESO also publishes several newsletters aimed at scientists and the general public; these are available upon subscription. The ESOcast is a video-podcast series dedicated to reporting news and research from ESO. In 2013, the IMAX documentary ''Hidden Universe 3D'' was produced in co-operation of Cinema Productions, Film Victoria, Swinburne University of Technology, and the European Southern Observatory.


Video gallery

File: ESO’s 50th Anniversary Gala Event.ogv, alt=Video link, with man at podium in background, ESO's 50th-anniversary event (''Munich Residenz in Germany, 11 October 2012'') File: Europe to the Stars bite-size.ogv, alt=Video link, with man using surveying equipment in background., 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


Image gallery

These images are from ESO's top-100 list. File: VISTA’s infrared view of the Orion Nebula.jpg, VISTA's infrared view of the Orion Nebula File: Helix Nebula.jpg, The Helix Nebula File: Omega Centauri by ESO.jpg, The Globular Cluster Omega Centauri File: Guisard - Milky Way.jpg, A 340-million pixel starscape from Paranal File: NGC 2264 by ESO.jpg, NGC 2264 and the Christmas Tree cluster File: Centre of the Milky Way.jpg, The Centre of the Milky Way File: NGC 2467 and Surroundings.jpg, NGC 2467 and Surroundings File: A reproduction of a composite colour image of the Horsehead Nebula and its immediate surroundings - Eso0202a.jpg, The Horsehead Nebula File: Messier 78.jpg, Messier 78: a reflection nebula in Orion File: Eta Carinae Nebula.jpg, The WR 22 and Eta Carinae regions of the Carina Nebula File: The hidden fires of the Flame Nebula.jpg, The hidden fires of the Flame Nebula File: Early Morning on Paranal.jpg, Early morning on Paranal File: The future ALMA array on Chajnantor.jpg, The future ALMA array on Chajnantor (artist's rendering) File: 360-degree Panorama of the Southern Sky.jpg, Rare 360-degree Panorama of the Southern Sky File: Lagoon Nebula (ESO).jpg, 370-million-pixel starscape of the Lagoon Nebula File: ESO - The Milky Way panorama (by).jpg, The Milky Way panorama File: ESO-The Omega Nebula-phot-25a-09-fullres.jpg, The Omega Nebula File: ESO Centaurus A LABOCA.jpg, Centaurus A File: ESO-RCW120-Phot-40-08-fullres.tif, Glowing Stellar Nurseries File: R Coronae Australis region.jpg, The R Coronae Australis region imaged with the Wide Field Imager at La Silla


See also


References


Bibliography

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External links


Atacama Large Millimeter Array

APEX telescope

ESO

ESO Top 100 Images

Webpage for the ESO telescopes at La Silla Observatory

Paranal Observatory

James Bond at Paranal



ESO Media on Youtube

ESO Vimeo channel

2011 video explaining the current and planned work of ESO
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