HOME

TheInfoList



OR:

The Extremely Large Telescope (ELT) is an
astronomical observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysical, oceanography and volcanology are examples of disciplines for which observatories have been constructed. His ...
currently under construction. When completed, it is planned to be the world's largest
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
/
near-infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of Light, visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from ...
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 ...
. Part of the
European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...
(ESO) agency, it is located on top of
Cerro Armazones Cerro Armazones is a mountain located in the Sierra Vicuña Mackenna of the Chilean Coast Range, approximately south-east of Antofagasta in the Antofagasta Region, Chile. Before construction started on the European Extremely Large Telescope, th ...
in the
Atacama Desert The Atacama Desert ( es, Desierto de Atacama) is a desert plateau in South America covering a 1,600 km (990 mi) strip of land on the Pacific coast, west of the Andes Mountains. The Atacama Desert is the driest nonpolar desert in the ...
of northern
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
. The design consists of a reflecting telescope with a segmented
primary mirror A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope. Description The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal ...
and a diameter secondary mirror, and will be supported by
adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
, eight
laser guide star A laser guide star is an artificial star image created for use in astronomical adaptive optics systems, which are employed in large telescopes in order to correct atmospheric distortion of light (called '' astronomical seeing''). Adaptive op ...
units and multiple large science instruments. The observatory aims to gather 100 million times more light than the human eye, 13 times more light than the largest optical telescopes existing in 2014, and be able to correct for atmospheric distortion. It has around 256 times the light gathering area of the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
and, according to the ELT's specifications, would provide images 16 times sharper than those from Hubble. The project was originally called the European Extremely Large Telescope (E-ELT), but the name was shortened in 2017. The ELT is intended to advance astrophysical knowledge by enabling detailed studies of planets around other stars, the first galaxies in the Universe, supermassive black holes, and the nature of the Universe's dark sector, and to detect water and organic molecules in
protoplanetary disk A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for the star itself, be ...
s around other stars. As of 2011, the facility was expected to take 11 years to construct, from 2014 to 2025. On 11 June 2012, the ESO Council approved the ELT programme's plans to begin civil works at the telescope site, with construction of the telescope itself pending final agreement with governments of some member states. Construction work on the ELT site started in June 2014. By December 2014, ESO had secured over 90% of the total funding and authorized construction of the telescope to start, which will cost around one billion
euro The euro ( symbol: €; code: EUR) is the official currency of 19 out of the member states of the European Union (EU). This group of states is known as the eurozone or, officially, the euro area, and includes about 340 million citizens . ...
s for the first construction phase. The first stone of the telescope was ceremonially laid on 26 May 2017, initiating the construction of the dome's main structure and telescope. , first light is planned for 2027.


History

On 26 April 2010, the
European Southern Observatory The European Organisation for Astronomical Research in the Southern Hemisphere, commonly referred to as the European Southern Observatory (ESO), is an intergovernmental organization, intergovernmental research organisation made up of 16 mem ...
(ESO) Council selected
Cerro Armazones Cerro Armazones is a mountain located in the Sierra Vicuña Mackenna of the Chilean Coast Range, approximately south-east of Antofagasta in the Antofagasta Region, Chile. Before construction started on the European Extremely Large Telescope, th ...
,
Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the east a ...
, as the baseline site for the planned ELT. Other sites that were under discussion included Cerro Macon, Salta, in Argentina;
Roque de los Muchachos Observatory Roque de los Muchachos Observatory ( es, Observatorio del Roque de los Muchachos, ORM) is an astronomical observatory located in the municipality of Garafía on the island of La Palma in the Canary Islands, Spain. The observatory site is operated ...
, on the Canary Islands; and sites in North Africa, Morocco, and Antarctica. Early designs included a segmented primary mirror with a diameter of and an area of about , with a secondary mirror with a diameter of . However, in 2011 a proposal was put forward to reduce its size by 13% to 978 m2, for a diameter primary mirror and a diameter secondary mirror. It reduced projected costs from 1.275 billion to 1.055 billion euros and should allow the telescope to be finished sooner. The smaller secondary is a particularly important change; places it within the capabilities of multiple manufacturers, and the lighter mirror unit avoids the need for high-strength materials in the secondary mirror support spider. ESO's Director General commented in a 2011 press release that "With the new E-ELT design we can still satisfy the bold science goals and also ensure that the construction can be completed in only 10–11 years." The ESO Council endorsed the revised baseline design in June 2011 and expected a construction proposal for approval in December 2011. Funding was subsequently included in the 2012 budget for initial work to begin in early 2012. The project received preliminary approval in June 2012. ESO approved the start of construction in December 2014, with over 90% funding of the nominal budget secured. The design phase of the 5-mirror
anastigmat An anastigmat or anastigmatic lens is a photographic lens completely corrected for the three main optical aberrations: spherical aberration, coma, and astigmatism. Early lenses often included the word ''Anastigmat'' in their name to advertise th ...
was fully funded within the ESO budget. With the 2011 changes in the baseline design (such as a reduction in the size of the primary mirror from 42 m to 39.3 m), in 2017 the construction cost was estimated to be €1.15 billion (including first generation instruments). In 2014, the start of operations was planned for 2024. Actual construction officially began in early 2017, and , first light is planned for 2027.


Planning

ESO focused on the current design after a feasibility study concluded the proposed diameter,
Overwhelmingly Large Telescope The Overwhelmingly Large Telescope (OWL) was a conceptual design by the European Southern Observatory (ESO) organization for an extremely large telescope, which was intended to have a single aperture of 100 meters in diameter. Because of the c ...
, would cost €1.5 billion (£1 billion), and be too complex. Both current fabrication technology and road transportation constraints limit single mirrors to being roughly per piece. The next-largest telescopes currently in use are the
Keck Telescopes The W. M. Keck Observatory is an astronomical observatory with two telescopes at an elevation of 4,145 meters (13,600 ft) near the summit of Mauna Kea in the U.S. state of Hawaii. Both telescopes have aperture primary mirrors, and when co ...
, the
Gran Telescopio Canarias The Gran Telescopio Canarias (GranTeCan or GTC) is a reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It is the world's largest single-aperture optical telescope. Constr ...
and the
Southern African Large Telescope The Southern African Large Telescope (SALT) is a 10-metre class optical telescope designed mainly for spectroscopy. It consists of 91 hexagonal mirror segments each with a 1-metre inscribed diameter, resulting in a total hexagonal mirror of 11.1 ...
, which each use small hexagonal mirrors fitted together to make a composite mirror slightly over across. The ELT uses a similar design, as well as techniques to work around atmospheric distortion of incoming light, known as
adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
. A 40-metre-class mirror will allow the study of the atmospheres of
extrasolar planet 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 ...
s. The ELT is the highest priority in the European planning activities for research infrastructures, such as the
Astronet Astronet is a consortium which gather European funding agencies in order to establish a comprehensive long-term planning for the development of European astronomy. The consortium started on September 1, 2005. Participants *Centre national de ...
Science Vision and Infrastructure Roadmap and the ESFRI Roadmap. The telescope underwent a Phase B study in 2014 that included "contracts with industry to design and manufacture prototypes of key elements like the primary mirror segments, the adaptive fourth mirror or the mechanical structure (...) ndconcept studies for eight instruments".


Design

The ELT will use a novel design with a total of five mirrors. The first three mirrors are curved (non-spherical), and form a
three-mirror anastigmat A three-mirror anastigmat is an anastigmat telescope built with three curved mirrors, enabling it to minimize all three main optical aberrations – spherical aberration, coma, and astigmatism. This is primarily used to enable wide fields of view, ...
design for excellent image quality over the 10 arcminute field of view (one third of the width of the full Moon). The fourth and fifth mirrors are (almost) flat, and provide
adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
correction for atmospheric distortions (mirror 4), and tip-tilt correction for image stabilisation (mirror 5). The fourth and fifth mirrors also send the light sideways to one of the Nasmyth focal stations at either side of the telescope structure, allowing multiple large instruments to be mounted simultaneously.


ELT mirror and sensors contracts


Primary mirror

The surface of the 39-metre primary mirror will be composed of 798 hexagonal segments, each measuring approximately 1.4 metres across and with 50 mm thickness. Each working day, two segments will be re-coated and replaced to ensure the mirror is always clean and highly reflective. Edge sensors constantly measure the relative positions of the primary mirror segments and their neighbours. 2394 position
actuators An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) an ...
(3 for each segment) use this information to support the system, keeping the overall surface shape unchanged against deformations caused by external factors such as wind, temperature changes or vibrations. In January 2017, ESO awarded the contract for the fabrication of the 4608 edge sensors to the FAMES consortium, which is composed of Fogale and Micro-Epsilon. These sensors can measure relative positions to an accuracy of a few nanometres, the most accurate ever used in a telescope. In May 2017, ESO awarded two additional contracts. One was awarded to
Schott AG Schott AG is a German multinational glass company specializing in the manufacture of glass and glass-ceramics. Headquartered in Mainz, Germany, it is owned by the Carl Zeiss Foundation. The company's founder and namesake, Otto Schott, is credi ...
who will manufacture the blanks of the 798 segments, as well as a maintenance set of 133 additional segments. The latter allow segments to be removed, replaced, and recoated on a rotating basis once the ELT is in operation. The mirror will be cast from the same low-expansion ceramic
Zerodur Zerodur (notation of the manufacturer: ZERODUR®), registered trademarkof Schott AG, is a lithium-aluminosilicate glass-ceramic produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including GTC, Keck ...
as the existing
Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...
mirrors in Chile. The other contract was awarded to the French company, Safran Reosc, a subsidiary of
Safran Electronics & Defense Safran Electronics & Defense, formerly known as Sagem Défense Sécurité, is a French company specializing in optronics, avionics and electronic systems, as well as software for civil and military applications in the naval, aeronautical and space ...
. They will receive the mirror blanks from Schott, and polish one mirror segment per day to meet the 7-year deadline. During this process, each segment will be polished until it has no surface irregularity greater than 7.5 nm RMS. Afterwards, Safran Reosc will then mount, test, and complete all optical testing before delivery. This is the second largest contract for the ELT construction and the third-largest contract ESO has ever signed. The segment support system units for the primary mirror are designed and produced by CESA (Spain) and VDL (the Netherlands). The contracts signed with ESO also include the delivery of detailed and complete instructions and engineering drawings for their production. Additionally, they include the development of the procedures required to integrate the supports with the ELT glass segments; to handle and transport the segment assemblies; and to operate and maintain them.


Secondary mirror

Making the secondary mirror is a major challenge as it is highly convex, and aspheric. It is also very large; at 4.2 metres in diameter and weighing 3.5 tonnes, it will be the largest secondary mirror ever employed on an optical telescope and the largest convex mirror ever produced. In January 2017, ESO awarded a contract for the mirror blank to
Schott AG Schott AG is a German multinational glass company specializing in the manufacture of glass and glass-ceramics. Headquartered in Mainz, Germany, it is owned by the Carl Zeiss Foundation. The company's founder and namesake, Otto Schott, is credi ...
, who will manufacture it of
Zerodur Zerodur (notation of the manufacturer: ZERODUR®), registered trademarkof Schott AG, is a lithium-aluminosilicate glass-ceramic produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including GTC, Keck ...
. Complex support cells are also necessary to ensure the flexible secondary and tertiary mirrors retain their correct shape and position; these support cells will be provided by
SENER SENER is a private engineering and technology group founded in 1956, and specialises in activities related to Engineering and Construction, and has industrial holdings in companies working in the areas of energy, environment and aeronautics. SEN ...
. The pre-formed glass-ceramic blank of the secondary mirror will then be polished, and tested by Safran Reosc. The mirror will be shaped and polished to a precision of 15 nanometres (15 millionths of a millimetre) over the optical surface.


Tertiary mirror

The 3.8-metre concave tertiary mirror, also cast from Zerodur, will be an unusual feature of the telescope. Most current large telescopes, including the VLT and the NASA/ESA Hubble Space Telescope, use just two curved mirrors to form an image. In these cases, a small, flat tertiary mirror is sometimes introduced to divert the light to a convenient focus. However, in the ELT the tertiary mirror also has a curved surface, as the use of three mirrors delivers a better final image quality over a larger field of view than would be possible with a two-mirror design.


Quaternary mirror

The 2.4-metre quaternary mirror is a flat adaptive mirror, and only 2 millimetres thick. With up to 8000 actuators, the surface can be readjusted at very high time frequencies. The deformable mirror will be the largest adaptive mirror ever made, and consists of six component petals, control systems, and voice-coil actuators. The image distortion caused by the turbulence of the Earth's atmosphere can be corrected in real time, as well as deformations caused by the wind upon the main telescope. The ELT's adaptive optics system will provide an improvement of about a factor of 500 in the resolution, compared to the best seeing conditions achieved so far without adaptive optics. The AdOptica consortium, partnered with
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 ...
(Istituto Nazionale di Astrofisica) as subcontractors, are responsible for the design and manufacture of the quaternary mirror, which is to be shipped to Chile by the end of 2022. Safran Reosc will manufacture the mirror shells, and also polish them.


Quinary mirror

The 2.7-metre by 2.2-metre quinary mirror is a tip-tilt mirror used to refine the image using
adaptive optics Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical tele ...
. The mirror will include a fast tip-tilt system for image stabilization that will compensate perturbations caused by wind, atmospheric turbulence, and the telescope itself before reaching the ELT instruments.


ELT dome and structure


Dome construction

The ELT dome will have a height of nearly 74 metres from the ground and a diameter of 86 metres, making it the largest dome ever built for a telescope. The dome will have a total mass of around 6100 tonnes, and the telescope mounting and tube structure will have a total moving mass of around 3700 tonnes. For the observing slit, two main designs were under study: one with two sets of nested doors, and the current baseline design, i.e. a single pair of large sliding doors. This pair of doors has a total width of 45.3 m. ESO signed a contract for its construction, together with the main structure of the telescopes, with the Italian ACe Consortium, consisting of
Astaldi Astaldi S.p.A. is an Italian multinational major construction company based in Rome. The group is active in the fields of civil engineering, hydraulic engineering, Electromechanical Engineering and transportation. Significant subsidiaries incl ...
and Cimolai and the nominated subcontractor, Italy's EIE Group. The signature ceremony took place on 25 May 2016 at ESO's Headquarters in Garching bei München, Germany. The dome is to provide needed protection to the telescope in inclement weather and during the day. A number of concepts for the dome were evaluated. The baseline concept for the 40m-class ELT dome is a nearly hemispherical dome, rotating atop a concrete pier, with curved laterally-opening doors. This is a re-optimisation from the previous design, aimed at reducing the costs, and it is being revalidated to be ready for construction. One year after signing the contract, and after the laying of the first stone ceremony in May 2017, the site was handed over to ACe, signifying the beginning of the construction of the dome's main structure.


Astronomical performance

In terms of astronomical performance the dome is required to be able to track about the 1-degree
zenith The zenith (, ) is an imaginary point directly "above" a particular location, on the celestial sphere. "Above" means in the vertical direction (plumb line) opposite to the gravity direction at that location (nadir). The zenith is the "highest" ...
al avoidance locus as well as preset to a new target within 5 minutes. This requires the dome to be able to accelerate and move at angular speeds of 2 degrees/s (the linear speed is approximately 5 km/h). The dome is designed to allow complete freedom to the telescope so that it can position itself whether it is opened or closed. It will also permit observations from the zenith down to 20 degrees from the horizon.


Windscreen

With such a large opening, the ELT dome requires the presence of a windscreen to protect the telescope's mirrors (apart from the secondary), from direct exposure to the wind. The baseline design of the windscreen minimises the volume required to house it. Two spherical blades, either side of the observing slit doors, slide in front of the telescope aperture to restrict the wind.


Ventilation and air-conditioning

The dome design ensures that the dome provides sufficient ventilation for the telescope not to be limited by dome seeing. For this the dome is also equipped with louvers, whereby the windscreen is designed to allow them to fulfill their function. Computational fluid dynamic simulations and wind tunnel work are being carried out to study the airflow in and around the dome, as well as the effectiveness of the dome and windscreen in protecting the telescope. Besides being designed for water-tightness, air-tightness is also one of the requirements as it is critical to minimise the air-conditioning load. The air-conditioning of the dome is necessary not only to thermally prepare the telescope for the forthcoming night but also in order to keep the telescope optics clean. The air-conditioning of the telescope during the day is critical and the current specifications permit the dome to cool the telescope and internal volume by 10 °C over 12 hours.


Science goals

The ELT will search for extrasolar planets – planets orbiting other stars. This will include not only the discovery of planets down to Earth-like masses through indirect measurements of the wobbling motion of stars perturbed by the planets that orbit them, but also the direct imaging of larger planets and possibly even the characterisation of their atmospheres. The telescope will attempt to image Earthlike
exoplanets 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 ...
, which may be possible. Furthermore, the ELT's suite of instruments will allow astronomers to probe the earliest stages of the formation of planetary systems and to detect water and organic molecules in protoplanetary discs around stars in the making. Thus, the ELT will answer fundamental questions regarding planet formation and evolution. By probing the most distant objects the ELT will provide clues to understanding the formation of the first objects that formed: primordial stars, primordial galaxies and black holes and their relationships. Studies of extreme objects like black holes will benefit from the power of the ELT to gain more insight into time-dependent phenomena linked with the various processes at play around compact objects. The ELT is designed to make detailed studies of the first galaxies. Observations of these early galaxies with the ELT will give clues that will help understand how these objects form and evolve. In addition, the ELT will be a unique tool for making an inventory of the changing content of the various elements in the Universe with time, and to understand star formation history in galaxies. One of the goals of the ELT is the possibility of making a direct measurement of the acceleration of the Universe's expansion. Such a measurement would have a major impact on our understanding of the Universe. The ELT will also search for possible variations in the fundamental physical constants with time. An unambiguous detection of such variations would have far-reaching consequences for our comprehension of the general laws of physics.


Instrumentation

The telescope will have several science instruments and will be able to switch from one instrument to another within minutes. The telescope and dome will also be able to change positions on the sky and start a new observation in a very short time. Four of its instruments, the first generation, will be available at or shortly after first light, while two others will begin operations at a later stage. Throughout its operation other instruments can be installed to make new use of its high resolution. The first generation includes four instruments: MICADO, HARMONI and METIS, along with the adaptive optics system MAORY. * HARMONI: The High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph (HARMONI) will function as the telescope's workhorse instrument for spectroscopy. * METIS: The Mid-infrared ELT Imager and Spectrograph (METIS) will be a mid-infrared imager and spectrograph. *MICADO: The Multi-AO (adaptive optics) Imaging Camera for Deep Observations (MICADO) will be the first dedicated imaging camera for the ELT and will work with the Multi-conjugate Adaptive Optics RelaY, (MAORY). The second generation of instruments consists of MOSAIC and ANDES: * MOSAIC: A proposed multi-object spectrograph which will allow astronomers to trace the growth of galaxies and the distribution of matter from shortly after the Big Bang to the present day. * ANDES (formerly HIRES): The ArmazoNes high Dispersion Echelle Spectrograph will be used to search for indications of life on Earth-like exoplanets, find the first-born stars of the universe, test for possible variations of the fundamental constants of physics, and measure the acceleration of the Universe's expansion.


Comparison

One of the largest optical telescopes operating today is the
Gran Telescopio Canarias The Gran Telescopio Canarias (GranTeCan or GTC) is a reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It is the world's largest single-aperture optical telescope. Constr ...
, with a 10.4 m aperture and a light-collecting area of 74 m2. Other planned
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 ...
s include the 25 m/368 m2
Giant Magellan Telescope The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope under construction, as part of the US Extremely Large Telescope Program (US-ELTP), . It will consist of seven 8.4 m (27.6 ft) diameter primary segments, that ...
and 30 m/655 m2
Thirty Meter Telescope The Thirty Meter Telescope (TMT) is a planned extremely large telescope (ELT) that has become controversial due to its location on Mauna Kea, on the island of Hawaiʻi. The TMT would become the largest visible-light telescope on Mauna Kea. S ...
, which are also targeting the second half of the 2020 decade for completion. These two other telescopes roughly belong to the same next generation of optical ground-based telescopes. Each design is much larger than previous telescopes. The size of the ELT has been reduced from its original design. But even with this reduction, the ELT is significantly larger than both other planned extremely large telescopes. It has the aim of observing the universe in greater detail than the
Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...
by taking images 15 times sharper, although it is designed to be complementary to space telescopes, which typically have very limited observing time available. The ELT's 4.2-metre
secondary mirror A secondary mirror (or secondary) is the second deflecting or focusing mirror element in a reflecting telescope. Light gathered by the primary mirror is directed towards a focal point typically past the location of the secondary. Secondary mirr ...
is the same size as the primary mirror on the
William Herschel Telescope The William Herschel Telescope (WHT) is a optical/near-infrared reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain. The telescope, which is named after William Herschel, ...
, the second largest optical telescope in Europe. The ELT under ideal conditions has an angular resolution of 0.005
arcsecond A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The na ...
which corresponds to separating two light sources 1 AU apart from distance, or two light sources 30 cm apart from roughly 12,000 km distance. At 0.03 arcseconds, the contrast is expected to be 108, sufficient to search for exoplanets. The unaided human eye has an angular resolution of 1 arcminute which corresponds to separating two light sources 30 cm apart from 1 km distance.


Stills

The images below show artistic renderings of the ELT and were produced by
ESO 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 ast ...
. File:Artist’s rendering of the ELT in operation.jpg, Artist's rendering of the ELT in operation. File:E-ELT Primary Mirror.svg, Diagram of the 40m-class ELT primary
mirror A mirror or looking glass is an object that Reflection (physics), reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the ...
. File:ELT vlt.jpg, ELT compared with one of the four existing VLT Unit Telescopes at Cerro Paranal, Chile File:Latest Rendering of the E-ELT.jpg, Rendering of ELT during the day. File:The E-ELT Enclosure Inside.jpg, Model of the gigantic and intricate structure inside the enclosure of the ELT. File:M1-close-up.tif, Close-up of ELT primary mirror (artist's impression).


Video

File:E-ELT Laser Guide Star.ogv, Artist's impression of the Extremely Large Telescope (ELT) in its enclosure on Cerro Armazones during night-time observations. The four beams shooting skywards are lasers that create artificial stars high in the Earth's atmosphere. File:The E-ELT gets ready for action (artist's impression).ogv, This video shows an artist's impression of the Extremely Large Telescope, the ELT. The protective dome is seen opening for a night observing the optical and infrared skies. File:The E-ELT in Action (artist's impression).ogv File:Fly-over of the planned road to armazones.ogg, A 3D view of the new road to Cerro Armazones area in the Chilean desert. The road extends from the public Route B-710 to the top of the mountain where the European Extremely Large Telescope (E-ELT) will sit. File:E-ELT Groundbreaking event.ogg, On 19 June 2014, a major milestone towards construction of the ELT was reached. Part of Cerro Armazones was blasted. This video provides a closer look at the event. Note that only natural sound is provided. File:Flattening the Cerro Armazones.ogg, Numerous construction workers using heavy machinery working in the Atacama Desert to flatten the top of the mountain for a platform large enough to host the ELT with its main mirror, 39.2 metres in diameter. File:Where the E-ELT will be.webm, This drone camera view gives an early indication of the scale of the project. File:ESOcast 84- The New E-ELT Design Unveiled.webm, A video describing what the ELT will be. File:The road to Armazones.webm, A camera drone follows sections of the road that connects Cerro Armazones, the site of the ELT, to ESO's observatory site at Cerro Paranal, home of the VLT. File:The ELT's future home.webm, These drone visuals from Gerhard Hüdepohl show the future location of the ELT against the tranquil backdrop of the barren Chilean desert, as of September 2016. File:ELT's first stone ceremony video compilation.webm, This compilation features footage from a ceremony marking the first stone of the ELT.


Gallery

File:Rendering of the MICADO instrument.jpg, Rendering of the MICADO instrument. File:Potw2011a - The Milky Way.jpg, The night sky over the construction site for the Extremely Large Telescope.


See also

*
Lists of telescopes This is a list of lists of telescopes. *List of astronomical interferometers at visible and infrared wavelengths *List of astronomical observatories *List of highest astronomical observatories *List of large optical telescopes *List of largest i ...
*
List of largest optical reflecting telescopes A ''list'' is any set of items in a row. List or lists may also refer to: People * List (surname) Organizations * List College, an undergraduate division of the Jewish Theological Seminary of America * SC Germania List, German rugby union ...
*
List of optical telescopes * List of largest optical reflecting telescopes - List of large optical telescopes * List of largest optical refracting telescopes * List of space telescopes * List of solar telescopes * List of telescope types * List of largest optical telescopes ...
*
Large Binocular Telescope The Large Binocular Telescope (LBT) is an optical telescope for astronomy located on Mount Graham, in the Pinaleno Mountains of southeastern Arizona, United States. It is a part of the Mount Graham International Observatory. When using both 8 ...
*
European Solar Telescope The European Solar Telescope (EST) is a pan-European project to build a next-generation 4-metre class solar telescope, to be located at the Roque de los Muchachos Observatory in the Canary Islands, Spain. It will use state-of-the-art instrument ...
(planned completion in 2025) *
Gran Telescopio Canarias The Gran Telescopio Canarias (GranTeCan or GTC) is a reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, Spain. It is the world's largest single-aperture optical telescope. Constr ...
*
List of astronomical observatories This is a list of astronomical observatories ordered by name, along with initial dates of operation (where an accurate date is available) and location. The list also includes a final year of operation for many observatories that are no longer in ...
*
List of highest astronomical observatories This is a list of the highest astronomical observatories in the world, considering only ground-based observatories and ordered by elevation above mean sea level. The main list includes only permanent observatories with facilities constructed at ...
* Other observatories in Chile: **
Llano de Chajnantor Observatory Llano de Chajnantor Observatory is the name for a group of astronomical observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Region approximately 50 kil ...
***
Atacama Large Millimeter Array The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The a ...
) **
Paranal Observatory Paranal Observatory is an astronomical observatory operated by the European Southern Observatory (ESO). It is located in the Atacama Desert of northern Chile on Cerro Paranal at altitude, south of Antofagasta. By total light-collecting area, it ...
***
Very Large Telescope The Very Large Telescope (VLT) is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each with a primary mirror 8.2 m across, ...
**
Cerro Armazones Observatory Cerro Armazones Observatory (Spanish: ''Observatorio Cerro Armazones,'' OCA; German: ''Observatorium Cerro Armazones,'' OCA) was an astronomical observatory owned and operated jointly by the Ruhr University Bochum (RUB) and the Catholic Universit ...
**
La Silla Observatory La Silla Observatory is an astronomy, astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are located at the site and are partly maintained by ESO. The obse ...
**
Cerro Tololo Inter-American Observatory The Cerro Tololo Inter-American Observatory (CTIO) is an astronomical observatory located on Cerro Tololo in the Coquimbo Region of northern Chile, with additional facilities located on Cerro Pachón about to the southeast. It is approximately ...


References


External links


ESO Extremely Large Telescope

ESO The Extremely Large Telescope ("E-ELT") Project

Final stage for telescope design

Green light for ELT

Ground Telescope to Super Size

MICADO

METIS

HARMONI

Record mirror for Euro telescope BBC Online August 7 2006


{{Portal bar, Astronomy, Stars, Spaceflight, Outer space, Solar System Astronomical observatories in Chile European Southern Observatory Buildings and structures under construction in Chile Telescopes under construction Articles containing video clips Astronomy projects