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Very Large Telescope (VLT)
The Very Large Telescope (VLT), built by The European Southern Observatory (ESO) of eight European countries, is worth $500 million and was approved in 1987 as the world’s only large telescope built on the planned and budgetary schedule. In addition, VLT consists of four individual telescopes and were named in the local Mapudan language by Antu, Kuyeen, Melipal and Yepun. The four telescopes are combined to observe and thus become the world’s largest optical telescope.
The Very Large Telescope (VLT) is located in the Atacama desert, northwest of Chile, South America. More specifically, the VLT is located at an altitude of 2,635 meters Cerro Paranal, which is the home of Paranal Observatory, 120 km south of Antofagasta. Its coordinate is (24° 37′ 38″ S, 70° 24′ 15″ W). The Very Large Telescope stands in the Atacama Desert because the driest area making it ideal for astronomical observations (ESO, 2018).
Figure 1. The map shows the location of the very large telescope (Google maps, 2019).
Purpose and function
Like other telescopes, the VLT is an extension of the human eyes to observe and explore every corner of the universe and understand the mysteries of the vast universe. The main wavelengths of VLT operate visible and infrared wavelengths, which are about 300 nm to 20 μm (NASA, 2014). The reasons why VLT operates visible and infrared wavelengths due to some advantages of them compared with other electromagnetic spectra. First of all, visible light wavelength passing through the atmosphere can overcome many challenges, avoid atmospheric obstruction, and observe most of the portion of the electromagnetic spectrum. Secondly, infrared radiation can through the atmosphere while the longer wavelengths are blocked. In addition, everything that has heat emits infrared radiation, including telescopes. (NASA, 2014) So VLT operates visible and infrared wavelengths among the EM spectrum to detect objects.
Figure 2. Image of VLT EM Spectrum (Josh’s Infrared Cache, 2009)
The Very Large Telescope consists of four telescopes with a mirror diameter of 8.2 m and four additional movable auxiliary telescopes measuring 1.8 m in diameter. By combining light from these telescopes (called the process of interferometry)(ESO, 2018). The interferometer records the interference fringes produced by combining light from two or more telescopes. The basic measurement is the amplitude and phase of the fringes.
Figure 3. Interferometry telescope measure（CHARA，2015）
NACO is the abbreviation of NAOS-CONICA, which is equipped with visible and infrared wavefront sensors. NACO with visible and infrared sensors, through computer-controlled flexible mirrors, can compensate for image distortion caused by atmospheric turbulence in real time (ESO, 2019).
Figure 5. NAOS optical components and transportation principle（Lenzen，2019）
The VLT uses an active optical system compared to other telescopes. The active optics is a wavefront correction technique used to eliminate the deformation of the optical system and the support of the telescope caused by factors such as gravity and temperature and it is a small portion of its beam is directed through the steering mirror to the four quadrant diodes used to measure the position of the laser beam, and the other is used to measure the direction on the focal plane behind the lens.
Figure 4. The active optical system (National Schools’ Observatory, 2019)
Supermassive blackhole – The centre of the Milky Way
VLT observed the central parts of our Galaxy with the NACO instrument in the near-infrared (spectrum with wavelengths between 780 and 2500 nm). The observed centre is also viewed as a supermassive black hole. Astronomers now can decide the mass of this supermassive black hole, this is contributed to the result of the motions of the most central stars, which have been followed more than 16 years (ESO, 2008). In the observation, 28 stars have been tracked, they are moving rapidly, orbiting a common, invisible point. Astronomers thus then concluded the location and mass of the black hole. The mass of the black hole is stated to be approximately 4 million solar mass (the mass of the Sun). In order to calculate the exact mass of this supermassive black hole, scientists measure the speed of the star and the size of the stellar orbit, then apply these data with Theory of relativity and law of universal gravitation. Astronomers from the ESO also derived the distance from the galactic centre to the Solar System, which is 27,000 light years away (O’NEILL, 2008).
In the photograph below, Sgr A* is marked by the orange cross and S2 is the bright star near it. Sagittarius A*(Sgr A*) is a bright and very dense astronomical radio source at the centre of the Milky Way galaxy. S2 is a star that is located close to the radio source Sagittarius A*, orbiting it with an orbital period of approximately 16 years.
Figure 7. Image of the Galactic Centre – Milky Way
(ESO/MPE/S. Gillessen et al, 2017)
The Very Large Telescope (VLT) is in the forefront of research into planets, stars and galaxies. Following are some good and acceptable reasons for investing VLT. To improve efficiency, to enlarge spectral coverage, to provide some quantitative analysis of spatial performance, and to let VLT has a substantially longer lifetime (ESO, 2018).
These upgrades allow government, universities, science centres and industry to do better research, and the VLT can remain world leading.
In addition, the producers may be attracted to film the movie around VLT due to its exceptional design and its remote location in the Atacama desert. There has had an example, that is, the spy film Quantum of Solace. Other countries can also access to VLT through the international partnership for their research, for instance, The Australian National University(Connery, 2017). For VLT, these can be the income sources and also raise its prestige.
The Very Large Telescope in the northwest desert of Chile, South America is of great significance for humans to understand black holes and other items or phenomenons in the infinite universe. The adaptive optical imager, the interferometer and the visible infrared wavefront sensors of the VLT make it the largest optical and near-infrared land-based telescopes currently built. Moreover, some discoveries of the supermassive black hole in Milky Way are done by VLT, giving scientists a deeper understanding of mysteries in the universe. In addition to the black hole, VLT is used for researches around the world, and it has a high prestige of world-top telescope.
Connery, G. (2017). ANU welcomes $26.1 million for access to Chilean telescopes. Retrieved fromhttps://www.smh.com.au/technology/anu-welcomes-261-million-for-access-to-chilean-telescopes-20170510-gw1ae6.html
- European Southern Observatory (ESO). (2008). Unprecedented 16-Year Long Study Tracks Stars Orbiting Milky Way Black Hole. Retrieved from https://www.eso.org/public/news/eso0846/
- European Southern Observatory (ESO). (2017). Image of the Galactic Centre. Retrieved from https://www.eso.org/public/images/ann17051c/
- European Southern Observatory (ESO). (2018). EUROPEAN ORGANISATION FOR ASTRONOMICAL RESEARCH IN THE SOUTHERN HEMISPHERE. Retrieved fromhttps://www.eso.org/public/about-eso/committees/cou/cou-149th/external/ESO-Cou-1796_PIP.pdf
- European Southern Observatory (ESO). (2018). The VLT 8.2-meter Unit Telescopes. Retrieved from https://www.eso.org/sci/facilities/paranal/telescopes/ut.html
- European Southern Observatory (ESO). (2019). Very Large Telescope. Retrieved from https://www.eso.org/public/teles-instr/paranal-observatory/vlt/
- Googlemap. (2019). Retrieved from https://www.google.com.au/maps/place/Very+Large+Telescope/@-30.632303,-59.4763107,5738433m/data=!3m1!1e3!4m5!3m4!1s0x96a54b61d20df8a7:0xffc2d3eef16a026b!8m2!3d-24
- National Aeronautics and Space Administration (NASA). (2014). Imagine the universe!. Retrieved from https://imagine.gsfc.nasa.gov/science/toolbox/emspectrum_observatories1.html
- National Schools’ Observatory (NSO) .(2019). Very Large Telescope (VLT). Retrieved from https://www.schoolsobservatory.org/learn/eng/tels/groundtel/vlt
- O’NEILL,I. (2008). Beyond Any Reasonable Doubt: A Supermassive Black Hole Lives in Centre of Our Galaxy. Retrieved from https://www.universetoday.com/22104/beyond-any-reasonable-doubt-a-supermassive-black-hole-lives-in-centre-of-our-galaxy/
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