Llano de Chajnantor Observatory is the name for a group of

astronomical Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxi ...

observatories located at an altitude of over 4,800 m (15,700 ft) 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 th ...

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 site is in the

Antofagasta Region The Antofagasta Region ( es, Región de Antofagasta, ) is one of Chile's sixteen first-order administrative divisions. The second-largest region of Chile in area, it comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered t ...

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 volcano. ...

. 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 deser ...

of the area is inhospitable to humans, but creates an excellent location for millimeter, submillimeter, and mid-infrared astronomy. This is because

water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous pha ...

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 vari ...

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, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observ ...

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 ...

(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 ''

Altiplano The Altiplano (Spanish for "high plain"), Collao (Quechua and Aymara: Qullaw, meaning "place of the Qulla") or Andean Plateau, in west-central South America, is the most extensive high plateau on Earth outside Tibet. The plateau is located at the ...

. The main ridge of the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

is over to the east, well into

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. The Salar de Atacama 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 American ...

. 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 geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

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 or alpinism, is a set of outdoor activities that involves ascending tall mountains. Mountaineering-related activities include traditional outdoor climbing, skiing, and traversing via ferratas. Indoor climbing, sport climbing, an ...

in the Salar de Atacama basin at approximately in elevation. Atacama Large Millimeter-Submillimeter Array, under construction

Rainfall at the ALMA site averages annually. The dry climate of Llano de Chajnantor is due to three factors: the rain shadows created by the Andes and the

Chilean Coastal Range The Chilean Coastal Range ( es, Cordillera de la Costa) is a mountain range that runs from north to south along the Pacific coast of South America parallel to the Andean Mountains, extending from Morro de Arica in the north to Taitao Peninsula, ...

, the inversion created by the Humboldt Current off the coast of Chile, and dry air descending between the

Hadley cell The Hadley cell, named after George Hadley, is a global-scale tropical atmospheric circulation that features air rising near the equator, flowing poleward at a height of 10 to 15 kilometers above the earth's surface, descending in the subtropics ...

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, bu ...

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

, in terms of

ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of ...

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

latitude In geography, latitude is a 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 the south pole to 90° at the north pol ...

deserts A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to denudation. About on ...

in southern Africa and central Australia.

Telescopes

Telescopes on Llano de Chajnantor

* The

(ALMA) is a large submillimetre radio telescope interferometer 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 and the European Southern Observatory, 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, 50 km east of San Pedro de Atacama built and operated by 3 European ...

(APEX) is a submillimetre radio telescope installed in 2003 and inaugurated in 2005. Its design is based on the North American 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. 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. In 2004 it was moved from

Las Campanas Observatory Las Campanas Observatory (LCO) is an astronomical observatory owned and operated by the Carnegie Institution for Science (CIS). It is in the southern Atacama Desert of Chile in the Atacama Region approximately northeast of the city of La Serena. ...

, where it had operated since 1995.

Telescopes on adjacent peaks

Starry night on the Chajnantor Plateau in the Chilean Andes

* The Atacama Cosmology Telescope (ACT) is Gregorian telescope designed to survey the sky at

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, t ...

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

Princeton University Princeton University is a private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the ...

. * 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 (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 In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space ...

. It is a Gregorian telescope. Attached to the telescope is the

POLARBEAR POLARBEAR (POLARization of the Background Radiation) is a cosmic microwave background polarization experiment located in the Atacama Desert of northern Chile in the Antofagasta Region. The POLARBEAR experiment is mounted on the Huan Tran Telescope ...

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 land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

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, U of C, or UChi) is a private university, private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park, Chicago, Hyde Park neighborhood. The University of 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 (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 reflectors. 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 property of a material which allows it to change or assume different properties in different directions, as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...

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.

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