astronomy

La Silla Observatory

La Silla Observatory is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand La Silla Observatory rather than just read about it. In short: La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are also located at the site and are partly maintained by ESO.

Key takeaways

La Silla Observatory belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect La Silla Observatory to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of La Silla Observatory from memory before moving on to harder problems.

Reference excerpt

La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are also located at the site and are partly maintained by ESO. The observatory is one of the largest in the Southern Hemisphere and was the first in Chile to be used by ESO. The La Silla telescopes and instruments are located in the North of the Coquimbo region, 150 km northeast of La Serena, on the outskirts of the Atacama Desert, one of the driest and most remote areas in the world. Like other observatories in this region, La Silla is far from sources of light pollution and, like the Paranal Observatory—home to the Very Large Telescope—it has some of the darkest night skies on Earth.

History

Following the decision in 1963 to approve Chile as the site for the ESO observatory, scouting parties were sent to various locations to assess their suitability. The site that was decided upon was La Silla in the southern part of the Atacama Desert, 600 km north of Santiago de Chile and at an altitude of 2400 metres. Besides being government property, it had the added benefits of being in a dry, flat and easily accessible area, yet isolated and remote from any artificial light and dust sources. Originally named the Cinchado, it was renamed La Silla ("the saddle" in Spanish) after its saddle-like shape. On October 30, 1964, the contracts were signed and an area of 627 square kilometres (242.1 sq mi) was purchased the following year. During 1965, temporary facilities were erected with living quarters, a workshop and storage area. The dedication ceremony of the road to the summit took place in March 1966, two months after completion of the road. On 25 March 1969, the ESO site at La Silla was finally formally inaugurated by President Eduardo Frei Montalva. With a permanent base of dormitories, workshops, hotels and several functioning telescopes, the observatory was fully operational. The ESO 1.5-metre and ESO 1-metre telescopes had been erected in the late 1960s, and were joined in 1968 by the Gran Prismo Objectif telescope, which had previously been used in South Africa. These three telescopes can be seen in this order from right to left in the background of the image on the left from June 1968. By 1976, the largest telescope planned, the § ESO 3.6 m Telescope, started operations. It was subsequently to have a 1.4m CAT (Coudé Auxiliary Telescope) attached. In 1984, the 2.2m telescope began operations, while in March 1989, the 3.5 m New Technology Telescope (NTT) saw first light. The program reached its apex with the installation of the SEST in 1987 (Swedish ESO Submillimetre Telescope), the only large submillimetre telescope in the southern hemisphere, which was a combined project between ESO and the Swedish Natural Science Research Council. Around the end of the century some of the original telescopes were closed: the 1m Schmidt closed in 1998 and the 1.5m in 2002, while new equipment owned by various foreign observatories was introduced. A 1-metre telescope owned by Marseille Observatory opened in 1998, followed by a 1.2-metre telescope from Geneva Observatory in 2000.

Telescopes

ESO operates three major optical and near infrared telescopes at the La Silla site: the New Technology Telescope (NTT), the 3.6-m ESO Telescope, and the 2.2-m Max-Planck-ESO Telescope (MPG/ESO Telescope). In addition La Silla hosts several other national and project telescopes such as the ESO 1-metre Schmidt Telescope, the 1.54-m Danish Telescope, the 1.2-m Leonhard Euler Telescope, the Rapid Eye Mount telescope, TRAPPIST and TAROT. These telescopes are not operated by ESO and hence do not fall under the responsibility of La Silla Science Operations.

ESO 3.6 m Telescope

This 3.6 m Cassegrain telescope started operations in 1976 and has been frequently upgraded since, including the installation of a new secondary mirror that has kept the telescope efficient and productive for astronomical research. The telescope hosts HARPS, the High Accuracy Radial velocity Planet Searcher. HARPS is a spectrograph with high precision and is the most successful finder of low-mass exoplanets to date. Since 2022, the 3.6 m telescope has also hosted NIRPS, the Near Infra Red Planet Searcher.

New Technology Telescope

The ESO New Technology Telescope (NTT) is an Alt-Az, 3.58-metre Richey-Chretien telescope which pioneered the use of active optics. The telescope and its enclosure had a revolutionary design for optimal image quality. NTT saw first light in March 1989. The telescope chamber is ventilated by a system of flaps which optimize the air flow across the NTT optimizing the dome and mirror seeing. To prevent heat input to the building, all motors in the telescope are water cooled and all the electronics boxes are insulated and cooled. The primary mirror of the NTT is actively controlled to preserve its figure at all telescope positions. The secondary mirror position is also actively controlled in three directions. The optimized airflow, the thermal controls, and the active optics give the excellent image quality of the NTT. The NTT has active instead of adaptive optics: it corrects the defects and deformation of the telescope and mirror, but does not correct the turbulence; it ensures that the optics is always in perfect shape. Together with the thermal control, it allows the NTT to reach the ambient seeing, but it does not improve it.

MPG/ESO 2.2 m Telescope

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with La Silla Observatory

Start with the simplest possible case. Write down what La Silla Observatory claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to La Silla Observatory before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about La Silla Observatory ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of La Silla Observatory

In research: La Silla Observatory appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses La Silla Observatory in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: La Silla Observatory is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1964 establishments in Chile, Astronomical observatories in Chile, Atacama Desert, so understanding it makes those chapters shorter.
In everyday life: Look for La Silla Observatory outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study La Silla Observatory in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what La Silla Observatory means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain La Silla Observatory out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is La Silla Observatory in simple terms?

Why does La Silla Observatory matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study La Silla Observatory?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on La Silla Observatory.