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12 Biggest Optical Telescopes In The world (2022 edition)

by Simran Dolwani

Telescopes have always been an integral part of planetary research. Whether it’s Hubble or Galilean, they have been the most demanding tools in astronomy for analyzing distinct celestial objects. The history of the development of telescopes has been revolutionizing. Galileo Galilei redefined astronomy when he first used a telescope to study extraterrestrial objects in the 17th century. Before this, no one used magnification instruments for this purpose. Galilei invented the world’s first telescope called Galilean Telescope, which is preserved in a museum in Italy. Galilei’s pioneering works have inspired researchers to develop more advanced optical telescopes which can reach the farthest points in the universe and use the latest technology to detect and measure radiations of mysterious space objects. 

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Below are the ten biggest optical telescopes that have been created to date, which exhibit our scientists’ progress in astronomy and space research domains. 

MMT or Multi-Mirror Telescope

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MMT is a part of Fred Lawrence Whipple Observatory, located in Arizona. The planetarium is managed by the Smithsonian Institute and the University of Arizona. Interestingly, it has a large primary mirror (a light-reflecting surface) of 6.5 meters in diameter. This mirror is lightweight and has an unusual honeycomb design created by the University of Arizona’s Stewards Observatory Mirror Laboratory. Its original name, however, Multi-Mirror Telescope, comes from six smaller mirrors that were used before the installation of a single mirror in 1998. It has changed from its inception in 1979 to 1998 to the present to enhance its power. Its improved adaptive optics system contributed to the revolutionary design of the Large Binocular Telescope. Besides, the telescope showed desired outcomes in the infrared experiments by eliminating warm surfaces from its light path. 

Gemini Observatory Telescopes

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The Gemini Observatory is an astronomical planetarium situated in Hawaii and Chile. It consists of two telescopes, Gemini North and Gemini South measuring 8.1 meters each. Both telescopes are a suite of the latest instruments and can work in infrared wavelengths using wide-field adaptive optics technology. It has a new instrument Gemini Planet Imager, a contrast spectrometer that allows telescopes to take images of exoplanets when they revolve around bright stars. The GPI has discovered 51 Eridani b, a Jupiter-like exoplanet that orbits around a star 51 Eridani in the Eridanus star constellation. Gemini has been supporting research in modern astronomy and space, including exoplanet analysis, the Solar System, star formation and evolution, galaxy dynamics and structure, black hole mysteries, long-distance galactic nucleus, and the construction of the universe. 

Very Large Telescope

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Very Large Telescope (VLT) is one of the most advanced telescopes in the world, operated by the European Southern Observatory. It has four independent telescopes, each having a single plane mirror measuring 8.2 meters. They can be used in combination or separately to attain maximum angular resolution or clarity. The telescope(s) can work in both infrared and visual wavelengths. All telescopes have advanced interferometric instruments, which help researchers to study luminous celestial objects such as stars and nebulas. VLT became the first telescope to capture a direct image of Beta Pictoris b, an exoplanet (a planet outside the solar system). It is one of the few optical telescopes that can track stars orbiting around massive black holes at the center of the Milky Way. 

Subaru Telescope

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The Subaru Telescope is situated at the Mauna Kea Observatory, Hawaii, United States and is operated by the National Astronomical Observatory of Japan. Its name was inspired by the Pleiades, a famous star cluster. It is a single-mirror type telescope and is almost similar to Gemini Telescopes. Various hi-tech instruments such as Cooled Mid Infrared Camera and Spectrometer (COMICS) and Multi-Object Infrared Camera and Spectrograph (MOIRCS), facilitate astronomers to study multiple targets at a time, like the magnificent interstellar dust. The telescope’s advanced high-contrast imaging system, Subaru Coronagraphic Extreme Adaptive Optics (SCExAO), can take direct images of the exoplanets. The Subaru Telescope is well known to be used for research purposes with an unaided eye. Due to its large field view and exceptional light-collecting power, Subaru has been used for deep astronomical surveys. For this reason, Subaru is used for planet-hunting space. 

Large Binocular Telescope (LBT)

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The Large Binocular Telescope is situated in the lush mountains of Arizona. Currently, it is the largest operational non-segmented telescope in the world. It has two identical primary mirrors of 8.4 meters in width. The telescope is one of a kind due to its unique design combined with light adaptive optics. This allows the telescope to decrease the atmospheric phase errors during the study and have a high resolution, low thermal background, and high sensitivity to spot the farthest objects. Earlier in 2008, LBT and a space-based telescope discovered the distinct galaxy cluster 2XMM J083026+524133, located about 6 billion light-years away from earth. 

Southern African Large Telescope

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The Southern African Large Telescope is currently the largest optical telescope in the southern region. It measures about 9.2 meters in length and has a distinctive mirror design. The primary mirror has 91 hexagonal segments and is fixed at an angle of 37 degrees which empowers the telescope to capture a larger area of the sky. Interestingly, its location enables researchers to do spectroscopic (electromagnetic radiation measurement) studies of celestial objects which cannot be done from the northern hemisphere. 

Keck 1 and 2

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Keck 1 and 2 is a dual telescope of W.M Keck Observatory situated in Hawaii. Both telescopes have a primary mirror of 10 meters in width and are composed of 36 hexagonal segments. They are equipped with advanced instruments such as laser guide star adaptive optics to improve astronomical seeing. Another instrument, the Deep Extragalactic Imaging Multi-Object Spectrograph (DEIMOS), can collect light from more than 130 galaxies in a single exposure. The Keck telescopes have supersensitive Near Infrared Cameras (NIRC) that can spot tiny flames on the Moon’s surface. This allows them to collect data from distant galaxies to study their origin and evolution. 

Hobby-Eberly Telescope

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The Hobby-Eberly Telescope is the second largest optical telescope on the globe located at the McDonald Observatory, Texas. Like other telescopes, its primary mirror has multiple hexagonal segments. HET is the most widely used telescope for identifying and studying distant objects such as galaxies and exoplanets. Unlike other telescopes, HET’s primary mirror is angled at 55 degrees and can rotate on its base. This allows the telescope to view 71 to 80 percent of the night sky. 

Gran Telescopio Canarias

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The Gran Telescopio Canarias (GranTeCan) is the largest segmented and operational primary mirror telescope. Canarias is maintained by the Spanish astrophysical research institute IAC. Initially, the telescope had 12 hexagonal segments, but the number was increased to 36. These segments are powered by an adaptive controlling system. The telescope includes three vital imaging instruments; OSIRIS, a low-resolution integrated spectroscope, MEGARA, a multi-wavelength spectrograph and CanariCam, an advanced mid-infrared imager. 

Telescopes under construction

Thirty Meter Telescope

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The Thirty Meter telescope is going to be among the largest optical telescopes after its completion in 2027. It will have a 30-meter-wide primary mirror complemented with two small mirrors to increase its working capacity. The telescope can operate from near-ultraviolet to mid-infrared wavelengths and will have a Multi-Conjugate Adaptive Optics system. This minimizes atmospheric disturbances and ensures accurate astronomical research. 

The Giant Magellan Telescope

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Currently, the Giant Magellan Telescope is under construction. It is expected to be completed in 2025. It will measure 24.5 meters in diameter and; will have seven identical mirrors of 8.4 meters in width forming the primary mirror. However, it will be launched with four mirror segments. The telescope is anticipated to have ten times higher image resolving power than the Hubble Space Telescope. 

European Extremely Large Telescope

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If everything goes to plan,  the European Extremely Large Telescope will be the world’s largest telescope by 2024. It will be able to collect light 13 times more than existing telescopes. Further, it will produce 16 times sharper images than the Hubble Space Telescope. Apart from the 39.3 meters giant primary mirror having 798 hexagonal segments, the telescope will access four extra mirrors to improve adaptive optics and image quality. It will help to analyze supergiant black holes and search for distant exoplanets and galaxies. Moreover, its state-of-the-art instruments will allow researchers to study star formation and evolution at the molecular level. 

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