Llano de Chajnantor Observatory is the name for a group of

astronomical Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include ...

observatories An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...

located at an altitude of over 4,800 m (15,700 ft) in the

Atacama Desert The Atacama Desert () is a desert plateau located on the Pacific Ocean, Pacific coast of South America, in the north of Chile. Stretching over a strip of land west of the Andes Mountains, it covers an area of , which increases to if the barre ...

of northern

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. The site is in the

Antofagasta Region The Antofagasta Region (, ) is one of Chile's Administrative divisions of Chile, sixteen first-order administrative divisions. Being the second-largest region of Chile in area, it comprises three provinces, Antofagasta Province, Antofagasta, El ...

approximately 50 kilometres (31 mi) east of the town of

San Pedro de Atacama San Pedro de Atacama is a Chilean town and commune in El Loa Province, Antofagasta Region. It is located east of Antofagasta, some 106 km (60 mi) southeast of Calama and the Chuquicamata copper mine, overlooking the Licancabur volcan ...

. The exceptionally

arid climate The desert climate or arid climate (in the Köppen climate classification ''BWh'' and ''BWk'') is a dry climate sub-type in which there is a severe excess of evaporation over precipitation. The typically bald, rocky, or sandy surfaces in desert ...

of the area is inhospitable to humans, but creates an excellent location for millimeter,

submillimeter Submillimetre astronomy or submillimeter astronomy (see spelling differences) is the branch of observational astronomy that is conducted at submillimetre wavelengths (i.e., terahertz radiation) of the electromagnetic spectrum. Astronomers plac ...

, and mid-infrared astronomy. This is because

water vapour Water vapor, water vapour, or aqueous vapor is the gaseous phase of water. It is one state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Water vapor ...

absorbs and

attenuate In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable at ...

s submillimetre radiation. Llano de Chajnantor is home to the largest and most expensive astronomical

telescope A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...

project in the world, the

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 ar ...

(ALMA). Llano de Chajnantor and the surrounding area has been designated as the Chajnantor Science Reserve (Spanish: ''Reserva Científica de Chajnantor'') by the government of Chile.

Site description

The Llano de Chajnantor is located on the western side of the

Puna de Atacama The Puna de Atacama or Atacama Plateau''Atacama Plateau''
article at the ''Encyclopædia Bri ...

, which is another name for the southern part of the

Altiplano The Altiplano (Spanish language, Spanish for "high plain"), Collao (Quechuan languages, Quechua and Aymara language, Aymara: Qullaw, meaning "place of the Qulla people, Qulla") or Andean Plateau, in west-central South America, is the most extens ...

. The main ridge of the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

is over to the east, well into

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. The

Salar de Atacama Salar de Atacama, located south of San Pedro de Atacama, is the largest Salt pan (geology), salt flat in Chile. It is surrounded by mountains and lacks drainage outlets. To the east, it is enclosed by the main chain of the Andes, while to the wes ...

basin borders the Puna de Atacama to the west, which in turn is bordered by the Cordillera Domeyko. The western side of the Puna de Atacama is dotted with the volcanoes of the Central Volcanic Zone of the

Andean Volcanic Belt The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca plate and Antarctic plate underneath the South Americ ...

. The Llano de Chajnantor site itself is bounded by volcanic peaks of the Purico Complex, which have been active in the

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

but have not erupted in historic times. Cerro Chajnantor is to the north, Cerro El Chascón to the east, and smaller peaks to the south and west. The Pampa la Bola lies to the northeast, north of Cerro El Chascón and east of Cerro Chajnantor. Llano de Chajnantor has an average elevation of , while Pampa la Bola averages . The thin atmosphere makes work difficult for humans, so much of the activity for ALMA will be conducted at a

base camp Mountaineering, mountain climbing, or alpinism is a set of outdoor activities that involves ascending mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas that have become sp ...

in the Salar de Atacama basin at approximately in elevation. Rainfall at the ALMA site averages annually. The dry climate of Llano de Chajnantor is due to three factors: the

rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from body of water, bodies of water (such as oceans and larg ...

s created by the Andes and the Chilean Coastal Range, the inversion created by the

Humboldt Current The Humboldt Current, also called the Peru Current, is a cold, low-salinity ocean current that flows north along the western coast of South America.Montecino, Vivian, and Carina B. Lange. "The Humboldt Current System: Ecosystem components and pro ...

off the coast of Chile, and dry air descending between the

Hadley cell The Hadley cell, also known as the Hadley circulation, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward near the tropopause at a height of above the Earth's surface, cooling and des ...

and the

Ferrel cell Atmospheric circulation is the large-scale movement of air and together with ocean circulation is the means by which thermal energy is redistributed on the surface of the Earth. The Earth's atmospheric circulation varies from year to year, but ...

, which forms the South Pacific High. While the site is generally viewed as being in the

, in terms of

ecoregion An ecoregion (ecological region) is an ecological and geographic area that exists on multiple different levels, defined by type, quality, and quantity of environmental resources. Ecoregions cover relatively large areas of land or water, and c ...

s it is in the Central Andean dry puna. Llano de Chajnantor is at the same

latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...

deserts A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the l ...

in southern Africa and central Australia.

Telescopes

Telescopes on Llano de Chajnantor

* The

(ALMA) is a large submillimetre

radio telescope A radio telescope is a specialized antenna (radio), antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the r ...

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 opt ...

at Llano de Chajnantor, consisting of 54 big and 12 smaller parabolic antennas. Due to the high projected total cost of over $1.3 billion, ALMA has been developed and is run by a consortium led by the

National Radio Astronomy Observatory The National Radio Astronomy Observatory (NRAO) is a federally funded research and development center of the United States National Science Foundation operated under cooperative agreement by Associated Universities, Inc. for the purpose of radi ...

and 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 m ...

, which are consortiums themselves. It has been in full operation since October 2013. * The

Atacama Pathfinder Experiment The Atacama Pathfinder Experiment (APEX) is a radio telescope 5,064 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama Desert in northern Chile Chile, officially the Republic of Chile, is a country in western Sou ...

(APEX) is a submillimetre radio telescope installed in 2003 and inaugurated in 2005. Its design is based on the North American

ALMA Alma or ALMA may refer to: Arts and entertainment * ''Alma'' (film), a 2009 Spanish short animated film * ''Alma'', an upcoming film by Sally Potter * ''Alma'' (Oswald de Andrade novel), 1922 * ''Alma'' (Le Clézio novel), 2017 * ''Alma'' ( ...

prototype antenna modified for single dish use. It is operated by a consortium led by the

Max Planck Institute for Radio Astronomy The Max Planck Institute for Radio Astronomy (MPIfRA) (German: ''Max-Planck-Institut für Radioastronomie'') is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society (German: Max-Planck-Gesellschaft). History By com ...

Telescopes on Pampa la Bola

* The Atacama Submillimeter Telescope Experiment (ASTE) is a submillimetre radio telescope built by

Mitsubishi Electric is a Japanese Multinational corporation, multinational electronics and electrical equipment manufacturing company headquartered in Tokyo, Japan. The company was established in 1921 as a spin-off from the electrical machinery manufacturing d ...

. It was an early prototype for the antennas of ALMA, and is operated by a consortium led by the National Astronomical Observatory of Japan. It was first built in Japan in 2000, and then was reassembled in Chile in 2002. It began regular observations in 2004. * The NANTEN2 Observatory (NANTEN2) is millimeter-wavelength radio telescope operated by a consortium led by the

Nagoya University , abbreviated to or NU, is a Japanese national research university located in Chikusa-ku, Nagoya. It was established in 1939 as the last of the nine Imperial Universities in the then Empire of Japan, and is now a Designated National Universit ...

. In 2004 it was moved from

Las Campanas Observatory Las Campanas Observatory (LCO) is an astronomy, astronomical observatory managed by the Carnegie Institution for Science (CIS). Located in Chile's Atacama Region, it sits about northeast of the city of La Serena, Chile, La Serena. The LCO's telesc ...

, where it had operated since 1995.

Telescopes on adjacent peaks

Starry night on the Chajnantor Plateau in the Chilean Andes

* The University of Tokyo Atacama Observatory (TAO) is a optical and infrared telescope under construction (as of 2019) on Cerro Chajnantor, which is immediately north of Llano de Chajnantor. A test facility, the miniTAO, with a telescope was completed in 2009. It is currently the highest permanent astronomical observatory in the world. * The

Cerro Chajnantor Atacama Telescope The Cerro Chajnantor Atacama Telescope (CCAT) is a proposed diameter telescope that is intended to reveal the cosmic origins of stars, planets, and galaxies with its Submillimetre astronomy, submillimeter cameras and spectrometers enabled by sup ...

(CCAT) is a proposed submillimetre radio telescope which will be located on Cerro Chajnantor near the TAO. Originally called the Cornell Caltech Atacama Telescope earlier in the development process, it is now referred to on the project's website by the CCAT acronym. Completion was at one time expected in 2020. The CCAT project has had trouble finding funding, and construction has not began as of 2019. The scientific collaboration has decided to build a pathfinder facility, CCAT-prime (CCAT-p), before pursuing the full CCAT. CCAT-p will be a similar type of telescope at CCAT, but much smaller, with 6 metre diameter. CCAT-p started construction in 2017 (fabrication started in late 2018) and first light is expected 2021. * The Huan Tran Telescope (HTT) is part of a project to measure the polarization of the

cosmic microwave background radiation The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

. It is a Gregorian telescope. Attached to the telescope is the POLARBEAR experiment, which is an array of

bolometer A bolometer is a device for measuring radiant heat by means of a material having a temperature-dependent electrical resistance. It was invented in 1878 by the American astronomer Samuel Pierpont Langley. Principle of operation A bolometer ...

s cooled to less than . HTT was first installed for testing at the CARMA site in 2010. It was moved to a location on Cerro Toco near the ACT in 2011 and saw first light in January 2012. It was developed by a consortium led by the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

. * The Simons Observatory is a microwave observatory consisting of a 6-m Large Aperture Telescope (LAT) and three 0.5 m Small Aperture Telescopes (SATs) with a total of 60,000 transition-edge sensor

s. It will conduct a wide survey of the

cosmic microwave background The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

and its linear polarization with arcminute resolution and a sensitivity an order of magnitude higher than the Planck space telescope. The SATs began observation April 2024, while the LAT's first light is expected early 2025.

Former telescopes

* The QU Imaging Experiment (QUIET) telescope was a three-element radio telescope array designed to measure the polarization of the

. The telescopes were custom-designed of an unusual Mizuguchi-Dragone design fitted with highly sensitive

s. The project, led by the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...

, was installed in 2009 in the facility that previously housed the CBI array. It operated until 2010 and was dismantled in 2011. * The

Cosmic Background Imager The Cosmic Background Imager (or CBI) was a 13-element astronomical interferometer perched at an elevation of 5,080 metres (16,700 feet) at Llano de Chajnantor Observatory in the Chilean Andes. It started operations in 1999 to study the cosmi ...

(CBI) was a radio telescope interferometer designed to measure the intensity and polarization of the

. It operated with thirteen antennas between 1999 and 2006, and from 2006 until 2008 with antennas. The CBI facility was later reused by the QUIET experiment. * The Millimeter-wave Interferometer (MINT) was a heterogenous four-element array that operated on the slopes of Cerro Toco in late 2001. The prototype instrument contained two and two

Cassegrain reflector The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and Antenna (radio), radio antennas, the main characteristic being that the optical path folds back onto itself, ...

s. It was designed to measure the cosmic microwave background radiation. * The Mobile Anisotropy Telescope (MAT, or MAT/TOCO) was a telescope that was designed to measure the

anisotropy Anisotropy () is the structural property of non-uniformity in different directions, as opposed to isotropy. An anisotropic object or pattern has properties that differ according to direction of measurement. For example, many materials exhibit ve ...

of the

. It originally was the gondola of the QMAP balloon-borne experiment. It operated on the slopes of Cerro Toco in late 1997 and again in late 1998. * The Atacama Cosmology Telescope (ACT) was a Gregorian telescope designed to survey the sky at

microwave Microwave is a form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves. Its wavelength ranges from about one meter to one millimeter, corresponding to frequency, frequencies between 300&n ...

wavelength In physics and mathematics, wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats. In other words, it is the distance between consecutive corresponding points of the same ''phase (waves ...

s. It was installed on the western side of Cerro Toco in 2007 and was operated by a consortium led by

Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...

until its decommissioning in 2022.

References

External links

*
Atacama Large Millimeter/sub-millimeter Array
public site homepage
Description of a trip to Llano de Chajnantor Observatory on BBC News

{{Portal bar, Chile, Stars, Spaceflight, Solar System, Science Astronomical observatories in Chile Atacama Desert Buildings and structures in Antofagasta Region European Southern Observatory 1999 establishments in Chile