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Large astronomical observatories have been installed in Chile. In the north, the Atacama Desert has a dry climate, and its skies are a treasure trove for astronomy.

From Chile, it is possible to observe areas of the southern celestial hemisphere, such as the center of the Milky Way and the Magellanic Clouds, impossible to see with telescopes installed in northern countries.

Laguna Chile
Magnificent image of the sky in the Cejar lagoon, in the Atacama desert. Credit: Stéphane Guisard.

The primitive inhabitants of Chile, a remote and unknown country, enjoyed the wonderful spectacle of the star-studded night skies.

Surely, they reflected a lot on the mystery of the stars, but they did not record their thoughts.

In recent years, thanks to international collaboration, it can be said that Chile is the capital of astronomy.

Early years of astronomy in Chile

The official history of Astronomy in Chile began in 1849, when Lieutenant James Gilliss, from the US Navy, arrived in Santiago to make measurements of the distance scale in the Solar System.

To measure the distance from Earth to Mars, Gilliss needed two points on Earth, as far from each other as possible.

One of these points was in Washington, where the meridian coincided with that of Chile.

James Gilliss wanted to settle in Chiloé, as far south as possible; But, in Santiago, he was shown the data of the Chiloé meteorology, and he understood that it was not sensible to install his instruments in that very rainy area.

The Chilean government made it easy for him to establish his observation point at Cerro Santa Lucía, in Santiago. From there, he was able to successfully perform his work.

On August 17, 1852, the Chilean government founded the National Astronomical Observatory (OAN).

One of the first measures was to buy the instruments and infrastructure that the Americans had used to measure planetary distances.

Astronomy in Chile in the 20th century

A century after the work of James Gillis, on the occasion of the 1957 International Geophysical Year, Federico Rutllant, director of the NAO, was invited to Washington to give lectures.

Under these circumstances, Professor Rutllant learned that the University of Chicago was planning to install a telescope in South Africa.

Federico Rutllant
Federico Rutllant Alsina (1904 – 1971) astronomer born in Spain and Chilean national. Credit: blog “”

Federico Rutllant managed to convince the director of the University of Chicago that Chile was closer than South Africa, that there was a direct flight to Santiago and that in Chile the sky was much better for astronomy.

When the American delegation entered the Elqui Valley and began to climb to the top of Cerro Tololo, the Chilean leadership in world astronomy began.

Observatory in Cerro Tololo, in the province of Elqui. Credit: Wikipedia, Photographer: David Walker.

Federico Rutllant did not stop there, and shortly afterwards he got the Carnegie Institution to install the first radio telescope in South America in Maipú.

In addition, the Carnegie Institution, which operated at the Mount Wilson Observatory, also installed an Observatory, in Chile, on Cerro Las Campanas.

Shortly after, on October 12, 1962, a Soviet mission arrived at Cerro Calán, followed by European scientists who contributed their knowledge and experience.

Why ESO chose Chile

The “European Southern Observatory” (ESO) is the main intergovernmental astronomical organization in Europe.

Since 1960, ESO has designed, financed and directed the construction and installation of astronomical observatories dedicated to large optical telescopes.

The objective of these observatories is to provide astronomers with state-of-the-art facilities that allow them to carry out important scientific discoveries

Very soon, ESO’s attempts focused on the Atacama Desert, one of the driest places on Earth, in Chile.

Chile had already proven to be a good host, giving preferential treatment and tax exemptions to establish important international research and observation centers in its territory.

In the Atacama desert, the climate is dry, with 350 days a year clear of clouds, atmospheric stability, minimal environmental and light pollution. There are clear skies, optimal for astronomical observation.

Artistic representation of the ALMA antenna array. Credit: ALMA (ESO / NAOJ / NRAO).

ESO projects in Chile

Currently, in Chile there are five large astronomy projects founded or administered or brought by ESO:

  • APEX telescope
  • La Silla Observatory
  • VLT Observatory
  • ELT telescope
  • ALMA telescope

APEX telescope

APEX (Pioneer Experiment in Atacama) is a collaboration between the Max Planck Institute, NASA and ESO.

Astronomers are already doing millimeter and submillimeter astronomy at Chajnantor, with the Atacama Pathfinder Experiment (APEX).

It is a 12 m telescope, of new technology, based on an ALMA antenna prototype and operating at the ALMA site.

The telescope was manufactured in Germany and is located on the Llano de Chajnantor, 50 km east of San Pedro de Atacama, at an altitude of 5,100 meters.

The APEX in Chajnantor. Credit: NASA

APEX has modified optics and improved antenna surface accuracy. It is designed to take advantage of the excellent transparency of the sky, working with wavelengths in the range of 0.2 to 1.4 mm.

La Silla Observatory

The La Silla Observatory is located at an altitude of 2,400 meters in the southern part of the Atacama Desert, 600 kilometers north of Santiago de Chile.

La Silla
The La Silla Observatory. Credit: ESO

Here, ESO operates two 4-meter optical telescopes, one of the most productive in the world.

The 3.58 meter diameter New Technology Telescope (NTT), which was the first in the world to have a computer-controlled main mirror, a technology developed at ESO.

The ESO Telescope, with a 3.6 meter primary mirror, today houses the world’s most important extrasolar planet finder: the HARPS instrument (High Precision Radial Velocity Planet Finder), a spectrograph with unmatched precision.

The four VLT telescopes

The VLT (Very Large Telescope) project was installed on Cerro Paranal, a 2,635-meter-high mountain, in the Atacama desert, in Chile.

The four VLT telescopes, inaugurated between 1998 and 2001, can operate as four independent telescopes or as a single instrument, for very high resolution.

The VLT3 telescope, at Cerro Paranal, Atacama, Chile. Credit: J.L. Dauvergne & G. Hüdepohl, web

Working together, the four telescopes possess the same light-gathering capacity of a single 16-meter diameter telescope, making them the largest optical instrument in the world.

ELT telescope

One of ESO’s most prominent projects is the European Extremely Large Telescope: ELT (Extremely Large Telescope). ELT is ESO’s proposal for the new generation of ground-based optical telescopes.

Artist’s impression of the Extremely Large Telescope (ELT). Credit: web “”

In 2011, the governing bodies of the European Southern Observatory (ESO) approved its budget for 2012.

This budget included preparatory work to locate the Extremely Large Telescope (ELT), at Cerro Armazones, in Chile.

It will be the largest optical-infrared telescope in the world, with a 40-meter diameter mirror: the world’s largest eye to scan the skies.

The facility is expected to take 11 years to build, from 2014 to 2025.

ALMA telescopes

ALMA is the acronym for “Atacama Large Millimeter / submillimeter Array”.

The ALMA set of telescopes was installed in “El Llano de Chanjnantor”, some 5,000 meters above sea level, in the Andes mountain range, in Chile.

The project has had the effective cooperation of Chile, which also contributed with the transfer of 176,000,000 square meters of land for these facilities.

ALMA telescopes in Atacama, Chile. Credit: NRAO, National Radio Astronomy Observatory.

ALMA is the largest ground-based telescope ever built. Its main array features fifty high-precision antennas, each 12 meters in diameter, which together act as a single telescope: an interferometer.

This is complemented by an additional set of four 12 m diameter antennas; in addition, there are twelve 7 m diameter antennas.

ALMA antennas can be configured in different ways. The maximum distances between antennas can range from 150 meters to 16 kilometers.

On March 13, 2013, ALMA was inaugurated. Currently 250 people work in the ALMA project in Chile and 250 in 17 other countries.

Click here to see this recommended link: “10 years of astronomy in Chile”

It compiles a decade of astronomical research (2002-2011) carried out by elite scientists from the University of Chile, the Catholic University of Chile and the University of Concepción.

The documentary contains unpublished images of some of the main astronomical discoveries made by Chilean scientists between 2002 and 2012.