Очень Большой Телескоп в пустыне Атакама

Telescope in the Atacama Desert, Chile

The Very Large Telescope (VLT) is an astronomical facility operated since 1998 by the European Southern Observatory, located on Cerro Paranal in the Atacama Desert of northern Chile. It consists of four individual telescopes, each equipped with a primary mirror that measures 8.2 meters in diameter. These optical telescopes, named Antu, Kueyen, Melipal, and Yepun (all words for astronomical objects in the Mapuche language), are generally used separately but can be combined to achieve a very high angular resolution. The VLT array is also complemented by four movable Auxiliary Telescopes (ATs) with 1.8 meter apertures. The VLT is capable of observing both visible and infrared wavelengths. Each individual telescope can detect objects that are roughly four billion times fainter than what can be seen with the naked eye. When all the telescopes are combined, the facility can achieve an angular resolution of approximately 0.002 arcsecond. In single telescope mode, the angular resolution is about 0.05 arcseconds. The VLT is one of the most productive facilities for astronomy, second only to the Hubble Space Telescope in terms of the number of scientific papers produced from facilities operating at visible wavelengths. Some of the pioneering observations made using the VLT include the first direct image of an exoplanet, the tracking of stars orbiting around the supermassive black hole at the centre of the Milky Way, and observations of the afterglow of the furthest known gamma ray burst.

The VLT consists of an arrangement of four large (8.2 metre diameter) telescopes (called Unit Telescopes or UTs) with optical elements that can combine them into an astronomical interferometer (VLTI), which is used to resolve small objects. The interferometer also includes a set of four 1.8 meter diameter movable telescopes dedicated to interferometric observations. The first of the UTs started operating in May 1998 and was offered to the astronomical community on 1 April 1999. The other telescopes became operational in 1999 and 2000, enabling multi telescope VLT capability. Four 1.8 metre Auxiliary Telescopes (ATs) have been added to the VLTI to make it available when the UTs are being used for other projects. These ATs were installed and became operational between 2004 and 2007.
as a set of four independent telescopes (this is the primary mode of operation). as a single large coherent interferometric instrument (the VLT Interferometer or VLTI), for extra resolution. This mode is used for observations of relatively bright sources with small angular extent. as a single large incoherent instrument, for extra light gathering capacity. The instrumentation required to obtain a combined incoherent focus was not originally built. In 2009, new instrumentation proposals were put forward to potentially make that observing mode available. Multiple telescopes are sometimes independently pointed at the same object, either to increase the total light gathering power or to provide simultaneous observations with complementary instruments.

The UTs are equipped with a large set of instruments permitting observations to be performed from the near ultraviolet to the mid infrared (i. e. a large fraction of the light wavelengths accessible from the surface of the Earth), with the full range of techniques including high resolution spectroscopy, multi object spectroscopy, imaging, and high resolution imaging. In particular, the VLT has several adaptive optics systems, which correct for the effects of atmospheric turbulence, providing images almost as sharp as if the telescope were in space. In the near infrared, the adaptive optics images of the VLT are up to three times sharper than those of the Hubble Space Telescope, and the spectroscopic resolution is many times better than Hubble. The VLTs are noted for their high level of observing efficiency and automation. The primary mirrors of the UTs are 8.2 meters in diameter but, in practice, the pupil of the telescopes is defined by their secondary mirrors, effectively reducing the usable diameter to 8.0 meters at the Nasmyth focus and 8.1 meters at the Cassegrain focus. The 8.2 m diameter telescopes are housed in compact, thermally controlled buildings, which rotate synchronously with the telescopes. This design minimises any adverse effects on the observing conditions, for instance from air turbulence in the telescope tube, which might otherwise occur due to variations in the temperature and wind flow.]] The principal role of the main VLT telescopes is to operate as four independent telescopes. The interferometry (combining light from multiple telescopes) is used about 20 percent of the time for very high resolution on bright objects, for example, on Betelgeuse. This mode allows astronomers to see details up to 25 times finer than with the individual telescopes. The light beams are combined in the VLTI using a complex system of mirrors in tunnels where the light paths must be kept equal within differences of less than 1 μm over a light path of a hundred metres. With this kind of precision the VLTI can reconstruct images with an angular resolution of milliarcseconds. Unit Telescopes 1–4 are since known as Antu (Sun), Kueyen (Moon), Melipal (Southern Cross), and Yepun (Evening Star), respectively. Originally there was some confusion as to whether Yepun actually stands for the evening star Venus, because a Spanish Mapuche dictionary from the 1940s wrongly translated Yepun as "Sirius".

Although the four 8.2 metre Unit Telescopes can be combined in the VLTI, their observation time is spent mostly on individual observations, and are used for interferometric observations for a limited number of nights every year. However, the four smaller 1.8 metre ATs are available and dedicated to interferometry to allow the VLTI to operate every night.]] Results from the VLT have led to the publication of an average of more than one peer reviewed scientific paper per day. For instance in 2017, over 600 refereed scientific papers were published based on VLT data. The telescope's scientific discoveries include direct imaging of Beta Pictoris b, the first extrasolar planet so imaged, tracking individual stars moving around the supermassive black hole at the centre of the Milky Way, and observing the afterglow of the furthest known gamma ray burst. In 2018, the VLT helped to perform the first successful test of Einstein's General Relativity on the motion of a star passing through the extreme gravitational field near the supermassive black hole, that is the gravitational redshift. In fact, the observation has been conducted for over 26 years with the SINFONI and NACO adaptive optics instruments in the VLT while the new approach in 2018 also used the beam combiner instrument GRAVITY. The Galactic Centre team at the Max Planck Institute for Extraterrestrial Physics (MPE) had use the observation revealed the effects for the first time. Other discoveries with VLT's signature include the detection of carbon monoxide molecules in a galaxy located almost 11 billion light years away for the first time, a feat that had remained elusive for 25 years. This has allowed astronomers to obtain the most precise measurement of the cosmic temperature at such a remote epoch. Another important study was that of the violent flares from the supermassive black hole at the centre of the Milky Way. The VLT and APEX teamed up to reveal material being stretched out as it orbits in the intense gravity close to the central black hole. Using the VLT, astronomers have also estimated the age of extremely old stars in the NGC 6397 cluster. Based on stellar evolution models, two stars were found to be 13.4 ± 0.8 billion years old, that is, they are from the earliest era of star formation in the Universe. They have also analysed the atmosphere around a super Earth exoplanet for the first time using the VLT. The planet, which is known as GJ 1214b, was studied as it passed in front of its parent star and some of the starlight passed through the planet's atmosphere. In all, of the top 10 discoveries done at ESO's observatories, seven made use of the VLT.

Each Unit Telescope is a Ritchey Chretien Cassegrain telescope with a 22 tonne 8.2 metre Zerodur primary mirror of 14.4 m focal length, and a 1.1 metre lightweight beryllium secondary mirror. A flat tertiary mirror diverts the light to one of two instruments at the f/15 Nasmyth foci on either side, with a system focal length of 120 m, or the tertiary tilts aside to allow light through the primary mirror central hole to a third instrument at the Cassegrain focus. This allows switching between any of the three instruments within 5 minutes, to match observing conditions. Additional mirrors can send the light via tunnels to the central VLTI beam combiners. The maximum field of view (at Nasmyth foci) is around 27 arcminutes diameter, slightly smaller than the full moon, though most instruments view a narrower field. Each telescope has an alt azimuth mount with total mass around 350 tonnes, and uses active optics with 150 supports on the back of the primary mirror to control the shape of the thin (177mm thick) mirror by computers.

One of the large mirrors of the telescopes was the subject of an episode of the National Geographic Channel's reality series World's Toughest Fixes, where a crew of engineers removed and transported the mirror to be cleaned and re coated with aluminium. The job required battling strong winds, fixing a broken pump in a giant washing machine and resolving a rigging issue. The procedure is part of routine scheduled maintenance. The area surrounding the Very Large Telescope was featured in the 2008 film Quantum of Solace. The ESO Hotel, the Residencia, served as a backdrop for part of the James Bond movie.