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World’s Biggest Optical Telescope – ELT


The Extremely Large Telescope will be
the largest optical and infrared telescope in the world, producing images
16 times sharper than those from the Hubble Space Telescope. It will make the
most detailed studies of planets around other stars, the first galaxies, in the
universe supermassive black holes, and the nature of the universe’s Dark Sector.
And we’re gonna learn more about it starting right now. Hello everyone,
welcome back to Launch Pad Astronomy, I’m Christian Ready, your friendly
neighborhood astronomer. This video is about the Extremely Large Telescope, or
ELT. lt’s origins date back to the late 1990s when the European Southern
Observatory started to think about the next generation of telescopes. They just
finished building their Very Large Telescope, or VLT. VLT consists of four
8-meter telescopes by combining the light from all four unit telescopes. VLT
can achieve a resolution equivalent to a single 130 meter telescope. This
technique is called “interferometry”, and while it does achieve high resolution, it
simply cannot collect as much light as a real telescope of that same aperture
because there are far fewer reflecting surfaces. In the early 2000s, ESO looked
into the Overwhelmingly Large Telescope, or OWL; a 100 meter telescope. The
proposal carried a 1.5 billion euro price tag, but it only had somewhere
between a 75 to 90 percent chance of success. Those are not good odds when
spending that kind of money, so the project was resized down to a 42 meters.
A 42 meter telescope would have answered the question of life, the universe, and
everything, but its overall price tag was only down to about 1.3 billion euro. In
2011 the telescope was resized again to 39.3 meters by removing the outer ring of
segmented hexagons. This brought the price tag under 1.1 billion euro and all
of the participating countries committed to the project. Another way to keep the
costs under control is to make sure that the overall design is this compact as
possible. This meant introducing a unique five-mirror design which folds up the
light path. The primary mirror consists of 798
hexagonal segments. Each segment is about 1.4 meters across, but is only 50
millimeters thick. That makes the mirrors lightweight and easy to produce. The
secondary mirror is convex shaped. Tt’s 4.2 meters in diameter and
weighs 3.5 tonnes. It will be the largest secondary mirror ever
employed on a telescope, and the largest convex mirror ever produced. The mirror
will be shaped and polished to a precision of 15 millionths of a
millimeter. In order to achieve the sharpest highest resolution images
possible, ELT employs the most advanced adaptive optics system ever developed,
making use of a fourth mirror that is 2.4 meters across but only 2 millimeters
thick. 8,000 magnetically levitated actuators will readjust the surface of
this mirror up to 1000 times per second to correct for any distortions in the
incoming light introduced by Earth’s atmosphere. Up to 8 high-powered lasers
will create artificial guide stars for the adaptive optics system to build up a
3d map of the atmospheric turbulence between the telescopes mirror and the
top of the sky. This system will provide an improvement of about 500 in ELT’s
resolution, allowing ELT to resolve images as sharply as the laws of physics
allow. When ELT begins operations in 2024, it will be equipped with two
state-of-the-art first light instruments. The High Angular Resolution Monolithic
Optical and Near-infrared Integral field spectrograph – or HARMONI – is a
spectrograph that’s designed to be set up and calibrated very quickly, allowing
ELT to achieve a kind of point-and-shoot capability so that if something
interesting happens they can stop what they’re doing and swing over and take a
look at an exploding star, gamma-ray burst, or anything else going boom in the
night. It will be able to probe high-redshift galaxies racing away from
us in the expanding universe. It will even have the ability to achieve one of
ELT’s highest priority scientific goals: to directly analyze
the atmospheres of extrasolar planets in great detail. The Multi adaptive optics
Imaging Camera for Deep Observations, or MICADO, will be capable of
diffraction-limited imaging at near-infrared wavelengths. The
sensitivity of this camera will be comparable to the James Webb Space
Telescope, but will have six times the resolution. It will image the center of
the Milky Way galaxy in unprecedented detail, making ultra-
sharp images of stars orbiting the supermassive black hole lurking in our
galaxy’s core. Even though ELT is designed to be as compact as possible
for its aperture, its dome is the largest constructed for a telescope, dwarfing
every other observatory. The dome has to be aerodynamic to keep a uniform wind
flow over the telescope. A ventilation system keeps the wind flowing over the
telescope smooth, automatically opening and closing to ensure a continuous
laminar airflow over the mirrors. ELT will be located at Cerro Armazones in
Chile. This site was chosen in part for its cool dark and dry skies but also
because of its proximity to the Paranal Observatory which is home to the VLT.
This allows ELT to make use of existing infrastructure, such as roads,
electricity, and so forth. First light is expected in 2024 at that time ELT will
not just be the pinnacle of ground-based astronomy, but will also stand as a
testament to our curiosity to understand the universe and our place in it. It will
detect Earth-like planets from the wobbling motions of their stars. It will
directly image larger exoplanets and even characterize their atmospheres. It
will be able to detect water and organic molecules in protoplanetary disks around
stars in the making; a major step forward in answering the question of are we
alone and if life can exist beyond Earth. It will explore the first objects in the
universe, looking back through time to study the first stars, the first galaxies,
even the first black holes. It will help us to understand how galaxies,
including our own Milky Way, form and evolve. It’ll mark our deepest probe into
the mystery of dark matter, and the dark energy that accelerates the
universe apart. ELT will give ESO much deserved bragging rights as the largest
eye on the sky, but it’s hardly a zero-sum game. ELT represents an
international collaboration not just between countries and institutions, but
also between the other next-generation telescopes such as the Giant Magellan
Telescope, the Thirty Meter Telescope, the James Webb Space Telescope, and many more.
Now if you’d like to learn more about the next generation of telescopes that
are under development, I have some links to them which I’ll provide for you both
here on screen and in the description below.
And if you’d like to join me on this journey through this amazing universe of
ours, please make sure to subscribe and ring the notification bell so that you
don’t miss out on any new videos. Until we see you next time, I’m Christian Ready,
and keep watching the skies. you

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