Star-gazing has long been a pastime—and profession—for humans. As technology
has advanced, so has our view of the cosmos. We’ve gone from discovering nearby planets to
cataloguing far-flung galaxies – and we now find ourselves on the precipice of another giant leap.
With the upcoming launch of the Extremely Large Telescope, there’s a chance of finding
something that astronomers have been searching for for decades: a new Earth.
This is Unveiled, and today we’re answering the extraordinary question:
Will This New Telescope Finally Discover a New Home for Humanity?
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Telescopes are by no means a modern invention, with the first telescope being patented in 1608
by Dutch eyeglass maker Hans Lippershey. While some controversy surrounds who actually invented
the telescope, Lippershey’s patented tube with two lenses—one concave, one convex—revolutionized
astronomy. This simple design was quickly adopted by, and improved upon by, the finest minds of
the ages, including Italian polymath Galileo, who built his own and pointed it heavenward.
From there, it was off to the races, with advances in telescope technology arriving relatively
rapidly. In 1668, Isaac Newton built the first reflecting telescope. Utilizing a large concave
mirror to focus light onto a smaller flat mirror, which projected the image into an eyepiece,
Newton’s telescope was a huge leap forward. His design proved cheaper and simpler to construct
while eliminating chromatic aberration (a kind of color distortion) and widening its field of view.
In 1789, William Herschel built the first giant telescope, and many more were built in the 1800s.
The 1930s saw the creation of radio telescopes, which detect radio waves, while the latter half
of the 20th century saw the rise of space telescopes, like the famous Hubble Telescope,
and massive terrestrial telescopes like the W.M. Keck Observatory in Hawaii.
Fast forward to 2005, and the European Southern Observatory, or ESO, starts planning the most
ambitious and advanced ground-based telescope ever: The Extremely Large Telescope, or ELT. In
2012, it was approved for construction at Cerro Armazones in Chile’s Atacama Desert, and in 2014,
construction began. Expected to be fully operational in 2025 or 2026, the ELT could be the
biggest game-changer in our cosmic understanding since Galileo’s prototype over 400 years ago.
As its name suggests, the ELT will be extremely large! The dome housing the telescope will be
over 240 feet high and 288 feet in diameter—an area roughly equivalent to a soccer pitch.
And it’ll be tough—built to withstand desert storms and even major earthquakes,
with the building resting on shock absorbers. In addition to being strong,
the dome also has to be agile. In order to make precise astronomical observations,
the dome needs to rotate quickly and smoothly, as any vibrations could negatively affect viewing.
The telescope’s main structure will house five mirrors, including the gigantic 128 foot
primary mirror, known as M1—by far the largest ever constructed. M1 will be made up of 798
individual hexagonal segments. M2 is another record-breaker: the largest secondary mirror ever
built. M2 will collect light from M1 and reflect it to a tertiary mirror, M3. Together, all three
mirrors will help deliver revolutionary image quality over the largest field of view possible
with current technology. M4 will be the largest adaptive mirror ever built, just shy of eight feet
in diameter. Its surface can literally be deformed to correct for any turbulence or vibrations.
Finally, M5 will be the largest tip-tilt mirror ever built. Its function will be to ensure that
images are stabilized. Together, these mirrors can gather 100 million times more light than
the human eye can, and 13 times more light than the next largest optical telescopes.
The instruments the ELT will use to analyze are nearly as impressive as the telescope itself.
Consisting of six major instruments, four at launch and two coming later,
these tools will help examine the universe in detail never before seen. HARMONI,
or High Angular Resolution Monolithic Optical and Near-infrared Integral field spectrograph,
is a 3D spectrograph that disperses light from objects into their component wavelengths.
This will enable astronomers to study objects both near and far in finer detail than ever before.
MICADO, or Multi-AO Imaging Camera for Deep Observations, is capable of taking
images at unprecedented depths. With a sensitivity comparable to the new James Webb Space Telescope,
but with six times the resolution, MICADO will be a key instrument in searching for exoplanets.
MAORY, or Multi-conjugate Adaptive Optics Relay, will help compensate for light distortion from
Earth’s atmosphere, enabling other instruments to take crystal clear images. METIS, or Mid-infrared
ELT Imager and Spectrograph, is a powerful spectrograph and high contrast imager that
will cover the infrared wavelength. It too will be searching for exoplanets. HIRES (High-Resolution
Spectrograph) and MOSAIC (Multi-Object Spectrograph) will be added at a later stage.
This revolutionary telescope and powerful instruments will aid astronomers in a wide range
of missions. In our own solar system, the ELT will be able to shed light on the formation of planets
through observation of objects in the Asteroid Belt between Mars and Jupiter. We’ll also be able
to study outer planets like Neptune and Uranus in finer detail than ever before. On the opposite
end of the scale, the ELT will allow scientists to peer far beyond our solar system at the very
first galaxies, helping us better understand how our universe formed. Astronomers are also
keen to use the ELT to study black holes, dark matter and energy, and other cosmic mysteries.
However, its biggest, and arguably most important mission, will be to search for exoplanets.
The ELT will allow us to closely observe exoplanets in habitable zones. Currently, there
have been about 4,000 exoplanets discovered. These are typically detected through indirect means. The
radial velocity method detects planets from the wobbling effects they have on their parent star,
while the transit method detects drops in a star’s brightness as
a planet passes in front of it. However, to accurately detect certain kinds of planets,
such as rocky planets in habitable zones, you need incredible precision and stability.
The ELT’s ultra-sensitive and ultra-stable spectrographs can overcome these limitations,
allowing astronomers to find exoplanets that would otherwise be impossible to discover.
After an exoplanet is discovered, the next logical step is to study its physical properties.
This is almost impossible without direct light from the planet. The light must be detected and
separated from the light of its star, which has been a gigantic obstacle until now. Overcoming
this contrast requires extremely sharp imaging. Smaller planet-finding telescopes on Earth,
as well as space telescopes like the James Webb, are capable of contrasts of 10–5 to 10–6 at
sub-arcsecond distances from the parent stars. To find an Earth-twin, however, you need a contrast
of 0–9 or better within less than 0.1 arcseconds from the star—something only the ELT can do.
And not only can the ELT discover previously undiscoverable exoplanets,
but it can also analyze their atmospheres in detail—an obviously critical component
in its habitability. Up until now, only young, self-luminous exoplanets could be
studied in any sort of detail. But because of its extraordinary sensitivity and spatial resolution,
the ELT will be able to look at giant and telluric (or rocky) exoplanets in reflected light. The
atmospheres of these planets can be analyzed using both optical and infrared wavelengths. The spectra
of these planets, including methane, water, carbon dioxide and monoxide, and even oxygen, can be
examined for biomarkers, potentially opening the door to the discovery of extraterrestrial life.
Indeed, it’s hard to predict what the ELT will uncover. The Hubble Space Telescope
is famous for its deep-field images of galaxies, but that wasn’t its original goal.
The ESO’s La Silla Observatory has been instrumental in finding exo-planets,
but it was created in 1977 when no one had heard of exoplanets. The ELT is poised to make
discoveries that no one has even thought of yet. This huge step forward in telescopic technology
could mean an even bigger leap in humanity’s progress, and, potentially, another Earth.
And that’s how this new telescope may finally discover a new home for humanity.
What do you think? Is there anything we missed? Let us know in the comments, check out these other
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