Credit:ESO/B. Tafreshi (twanight.org)
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| Credit: ESO |
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La Silla Observatory has been the first astronomical site of the European consortium ESO since 1964. ESO means "European Southern Observatory". La Silla hosts two of the most active four-meter-class telescopes in the world:
- The very famous ESO-3.6-m Telescope
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| Credit: ESO |
- The New Technology Telescope (NTT), a pioneer in optical instrumentation for astronomy.
As a matter of fact, La Silla is not the home of only two but a total of 18 independent astronomical observatories whose a dozen of them is currently commissioned. This major concentration of scientific instruments helps to raise La Silla among the world's most active observatories, with an average of 300 annual research papers. Even today for its 50th anniversary, La Silla remains a relevant and prolific workplace for astronomers.
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| Credit: ESO |
If we leave the VLT in order to link La Silla, it is not a short travel at all. The track is about 1 000 km long towards the South. Moreover, La Silla is not situated within the Atacama region but rather in the Coquimbo region, where La Serena is the capital city, counting around 200 000 inhabitants -150 km south of La Silla.
In addition to benefit from having a comfortable 2 400 meters altitude, La Silla is immersed in the arid climate influenced by the Atacama: a cold and dry weather during nightime, with extremely rare annual rainfall as well as overcast weather; definitely a spot intelligently selected by the Astronomers.
La Silla is mountain-station like: hotel, restaurant, library, conference hall, nursery, water station, solar power plant...and so on. Obviously, all these facilities are only dedicated to scientists and operating staff. If visiting such an amazing observatory is an idea which has been kept in your mind for a long time, you should know that public tours are offered every Saturdays. Learn more...
Telling the story of this observatory does not go without telling the roots of ESO.
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| Credit: ESO |
The idea of building a collaborative observatory maintained by a group of European astronomers did not raised up yesterday but in 1952! An emblematic figure who triggered the discussions on such an ambitious project was Walter Baade. Baade was a German astronomer who had worked at the Mount Wilson Observatory in the USA for 27 years. He and his friend Fritz Zwicky are the fathers of a new category of deep sky objects known as Supernovae made with observations in 1934.
During a meeting at the Leiden Observatory in the Netherlands, in spring 1953, Walter Baade suggested to European astronomers that if they wanted to catch up with the performance level of their Americans colleagues, they should gather all their forces and use their financial, scientific and technical skills in order to construct a large telescope.
A year later, in 1954, 12 great astronomers from 6 European nations reached out at the Leiden's Parliament for proposing a convention which could allow them to work together on an European Observatory project. The countries involved in this consortium were: Belgium, Germany, France, the Netherlands, Sweden and the United-Kingdom.
Nevertheless, they should wait several years of negotiations to end up signing an agreement. Indeed, on October 5, 1962, the European Southern Observatory was officially created thanks to the commitment of 5 nations (the UK retired in 1960 since it did not comply with ESO other member states).
During a meeting at the Leiden Observatory in the Netherlands, in spring 1953, Walter Baade suggested to European astronomers that if they wanted to catch up with the performance level of their Americans colleagues, they should gather all their forces and use their financial, scientific and technical skills in order to construct a large telescope.
A year later, in 1954, 12 great astronomers from 6 European nations reached out at the Leiden's Parliament for proposing a convention which could allow them to work together on an European Observatory project. The countries involved in this consortium were: Belgium, Germany, France, the Netherlands, Sweden and the United-Kingdom.
Nevertheless, they should wait several years of negotiations to end up signing an agreement. Indeed, on October 5, 1962, the European Southern Observatory was officially created thanks to the commitment of 5 nations (the UK retired in 1960 since it did not comply with ESO other member states).
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| Credit: ESO |
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All-sky analysis on the Chilean side were carried out in the same time as in South Africa and more particularly in 1963 when ESO's Europeans astronomers and AURA's Americans ones met together for a special visit of potential construction sites for their telescopes.
AURA stands for "Association of Universities for Research in Astronomy". It is an American institution similar to ESO but already owned at that time several lands whose main one is Cerro Tololo. Atop this mount was built the first astronomical observatory in Chile: CTIO. Thus, AURA proposed to ESO some of its property which could comply with Europeans requirements in terms of surface area and especially atmospheric quality. This offer could have led to a partnership between the two major institutions in the worldwide astronomy community. |
| Crédit: ESO |
Less than a year after, constructions started, and first of all, a road leading to the summit was drawn. The official inauguration of La Silla observatory happened on March, 25 1969, 50 years ago!
La Silla is not only a common astronomical facility settled in the middle of nowhere. La Silla is a pioneer in optical engineering applied to astronomy. For instance, it hosts the New Technology Telescope (NTT) and as its name suggests, was the first one in the world to be equipped with an active optics system. Such an instrument is composed of a deformable mirror hold by tens of actuators that are controlled by a Real-Time Computer to compensate for optical defects caused by the weight of the primary mirror and the temperature variations. Active optics enables to build slimmer mirrors, lighter and consequently larger collecting surfaces at lower costs.
In 1989, a second telescope, the ESO-3.6-m telescope made history! For the first time a telescope used an operational system of Adaptive Optics (AO): COME-ON, later called ADONIS. This AO was made of 52 actuators and a wavefront sensor capable of correcting atmospheric turbulence 30 times per second. The first lights of COME-ON showed impressive results and extended the telescope's resolution limit to 0.2 arcseconds, with an average seeing of more than 1 arcsecond.
Since the 1980s, we have been knowing what key role active optics and adaptive optics play in modern astronomy. They are an asset for pushing the telescopes performances up to their theoretical resolution diffraction limit. Today, both of these systems are now integrated in every large telescope and sub-instrument.
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| NTT as seen on the front page of Sky & Telescope Magazine in 1989 |
In 1989, a second telescope, the ESO-3.6-m telescope made history! For the first time a telescope used an operational system of Adaptive Optics (AO): COME-ON, later called ADONIS. This AO was made of 52 actuators and a wavefront sensor capable of correcting atmospheric turbulence 30 times per second. The first lights of COME-ON showed impressive results and extended the telescope's resolution limit to 0.2 arcseconds, with an average seeing of more than 1 arcsecond.
Since the 1980s, we have been knowing what key role active optics and adaptive optics play in modern astronomy. They are an asset for pushing the telescopes performances up to their theoretical resolution diffraction limit. Today, both of these systems are now integrated in every large telescope and sub-instrument.
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| Credit: ESO |
The most popular scientific instrument which equips La Silla Observatory is certainly the High resolution spectrometer HARPS on ESO-3.6-m telescope which is one of the most powerful in its category. HARPS is a spectrograph entirely dedicated to Exoplanet research around low-mass stars using the radial velocity indirect detection method. By comparing the spectrum of a star to a reference spectrum, a shift in wavelength could appear. In the case these spectral lines are shifted, it means an invisible object is interacting with the star and orbiting it. This physical principle is the so-called Doppler effect. Therefore planets orbiting stars other than the sun can be detected with a high efficiency thanks to this method.
HARPS ended up detecting Gliese 581 e, in 2009, which is the lightest known exoplanet. It is located 20 light-years away and weights not more than twice the Earth. Gliese 581 e is just an example among a rich catalog of 135 exoplanets discovered by HARPS instrument since 2002.
HARPS ended up detecting Gliese 581 e, in 2009, which is the lightest known exoplanet. It is located 20 light-years away and weights not more than twice the Earth. Gliese 581 e is just an example among a rich catalog of 135 exoplanets discovered by HARPS instrument since 2002.
Both NTT and ESO-3.6-meter telescopes are the only two observatories fully operated by ESO. Obviously the list goes on since we can find far more telescopes atop La Silla, all of them administrated by individual ESO-member institutions. Here is a non-exhaustive list of telescopes currently in operation:
- MPG/ESO 2.2-metre telescope
- Danish 1.54-metre telescope
- Swiss 1.2-metre Leonhard Euler Telescope
- Rapid Eye Mount telescope
- TRAnsiting Planets and PlanetesImals Small Telescope–South
- Télescope à Action Rapide pour les Objets Transitoires (TAROT)
- ESO 1-metre Schmidt telescope
- ESO 1-metre telescope
- Multi-site All-Sky CAmeRA
- BlackGEM
- ExTrA
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| Credit: ESO |
I hope this virtual journey around the European observatory of La Silla was instructive. Feel free to drop a comment, to ask some questions and to share this article! Our next step will drive us to the Atacama Desert, to know more about the famous Paranal Observatory, where the Very Large Telescope is located, but not only...
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