Rise of the Super Telescopes: Why We Build Them

This illustration shows what the Giant Magellan Telescope will look like when it comes online. The fifth of its seven mirror segments is being cast now. Each of the segments is a 20 ton piece of glass. Image: Giant Magellan

One night 400 years ago, Galileo pointed his 2 inch telescope at Jupiter and spotted 3 of its moons. On subsequent nights, he spotted another, and saw one of the moons disappear behind Jupiter. With those simple observations, he propelled human understanding onto a path it still travels.

Galileo’s observations set off a revolution in astronomy. Prior to his observations of Jupiter’s moons, the prevailing belief was that the entire Universe rotated around the Earth, which lay at the center of everything. That’s a delightfully childish viewpoint, in retrospect, but it was dogma at the time.

Until Galileo’s telescope, this Earth-centric viewpoint, called Aristotelian cosmology, made sense. To all appearances, we were at the center of the action. Which just goes to show you how wrong we can be.

But once it became clear that Jupiter had other bodies orbiting it, our cherished position at the center of the Universe was doomed.

Galileo Galilei set off a revolution in astronomy when he used his telescope to observe moons orbiting Jupiter. By Justus Sustermans - http://www.nmm.ac.uk/mag/pages/mnuExplore/PaintingDetail.cfm?ID=BHC2700, Public Domain, https://commons.wikimedia.org/w/index.php?curid=230543
Galileo Galilei set off a revolution in astronomy when he used his telescope to observe moons orbiting Jupiter. By Justus Sustermans – http://www.nmm.ac.uk/mag/pages/mnuExplore/PaintingDetail.cfm?ID=BHC2700, Public Domain, https://commons.wikimedia.org/w/index.php?curid=230543

Galileo’s observations were an enormous challenge to our understanding of ourselves at the time, and to the authorities at the time. He was forced to recant what he had seen, and he was put under house arrest. But he never really backed down from the observations he made with his 2 inch telescope. How could he?

Now, of course, there isn’t so much hostility towards people with telescopes. As time went on, larger and more powerful telescopes were built, and we’ve gotten used to our understanding going through tumultuous changes. We expect it, even anticipate it.

In our current times, Super Telescopes rule the day, and their sizes are measured in meters, not inches. And when new observations challenge our understanding of things, we cluster around out of curiosity, and try to work our way through it. We don’t condemn the results and order scientists to keep quiet.

The first of the Super Telescopes, as far as most of us are concerned, is the Hubble Space Telescope. From its perch in Low Earth Orbit (LEO), the Hubble has changed our understanding of the Universe on numerous fronts. With its cameras, and the steady stream of mesmerizing images those cameras deliver, a whole generation of people have been exposed to the beauty and mystery of the cosmos.

The Hubble Space Telescope could be considered the first of the Super Telescopes. In this image it is being released from the cargo bay of the Space Shuttle Discovery in 1990. Image: By NASA/IMAX - http://mix.msfc.nasa.gov/abstracts.php?p=1711, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6061254
The Hubble Space Telescope could be considered the first of the Super Telescopes. In this image it is being released from the cargo bay of the Space Shuttle Discovery in 1990. Image: By NASA/IMAX – http://mix.msfc.nasa.gov/abstracts.php?p=1711, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6061254

Hubble has gazed at everything, from our close companion the Moon, all the way to galaxies billions of light years away. It’s spotted a comet breaking apart and crashing into Jupiter, dust storms on Mars, and regions of energetic star-birth in other galaxies. But Hubble’s time may be coming to an end soon, and other Super Telescopes are on the way.

Nowadays, Super Telescopes are expensive megaprojects, often involving several nations. They’re built to pursue specific lines of inquiry, such as:

  • What is the nature of Dark Matter and Dark Energy? How are they distributed in the Universe and what role do they play?
  • Are there other planets like Earth, and solar systems like ours? Are there other habitable worlds?
  • Are we alone or is there other life somewhere?
  • How do planets, solar systems, and galaxies form and evolve?

Some of the Super Telescopes will be on Earth, some will be in space. Some have enormous mirrors made up of individual, computer-controlled segments. The Thirty Meter Telescope has almost 500 of these segments, while the European Extremely Large Telescope has almost 800 of them. Following a different design, the Giant Magellan Telescope has only seven segments, but each one is over 8 meters in diameter, and each one weighs in at a whopping 20 tons of glass each.

This artistic bird's-eye view shows the dome of the ESO European Extremely Large Telescope (E-ELT) in all its glory, on top of the Chilean Cerro Armazones. The telescope is currently under construction and its first light is targeted for 2024.
This artistic bird’s-eye view shows the dome of the ESO European Extremely Large Telescope (E-ELT) in all its glory, on top of the Chilean Cerro Armazones. The telescope is currently under construction and its first light is targeted for 2024.

Some of the Super Telescopes see in UV or Infrared, while others can see in visible light. Some see in several spectrums. The most futuristic of them all, the Large Ultra-Violet, Optical, and Infrared Surveyor (LUVOIR), will be a massive space telescope situated a million-and-a-half kilometers away, with a 16 meter segmented mirror that dwarfs that of the Hubble, at a mere 2.4 meters.

Some of the Super Telescopes will discern the finest distant details, while another, the Large Synoptic Survey Telescope, will complete a ten-year survey of the entire available sky, repeatedly imaging the same area of sky over and over. The result will be a living, dynamic map of the sky showing change over time. That living map will be available to anyone with a computer and an internet connection.

A group photo of the team behind the Large Synoptic Survey Telescope. The group gathered to celebrate the casting of the 'scope's 27.5 ft diameter mirror. The LSST will create a living, detailed, dynamic map of the sky and make it available to anyone. Image: LSST Corporation
A group photo of the team behind the Large Synoptic Survey Telescope. The group gathered to celebrate the casting of the ‘scope’s 27.5 ft diameter mirror. The LSST will create a living, detailed, dynamic map of the sky and make it available to anyone. Image: LSST Corporation

We’re in for exciting times when it comes to our understanding of the cosmos. We’ll be able to watch planets forming around young stars, glimpse the earliest ages of the Universe, and peer into the atmospheres of distant exoplanets looking for signs of life. We may even finally crack the code of Dark Matter and Dark Energy, and understand their role in the Universe.

Along the way there will be surprises, of course. There always are, and it’s the unanticipated discoveries and observations that fuel our sense of intellectual adventure.

The Super Telescopes are technological masterpieces. They couldn’t be built without the level of technology we have now, and in fact, the development of Super Telescopes help drives our technology forward.

But they all have their roots in Galileo and his simple act of observing with a 2-inch telescope. That, and the curiosity about nature that inspired him.

The Rise of the Super Telescopes Series:

Rise of the Super Telescopes: The Overwhelmingly Large Telescope

We humans have an insatiable hunger to understand the Universe. As Carl Sagan said, “Understanding is Ecstasy.” But to understand the Universe, we need better and better ways to observe it. And that means one thing: big, huge, enormous telescopes.

In this series we’ll look at 6 of the world’s Super Telescopes:

The Overwhelmingly Large Telescope

The OWL (Overwhelmingly Large Telescope) was a gargantuan telescope proposed by the European Southern Observatory (ESO). The OWL was going to be a 100 meter monstrosity, which would dwarf anything in operation at the time. Sadly, OWL was eventually cancelled.

For now, anyway.

At the time that OWL was first proposed—in the late 1990’s—scientific studies showed that huge telescopes would be necessary to advance our knowledge. OWL promised to help us unlock the mystery of dark matter, peer back in time to witness the birth of the first stars and galaxies, and to directly image the atmospheres of exoplanets. It’s easy to see why people were excited by OWL.

This image simulates the increased resolving power of the OWL compared to its contemporaries. Image: ESO Telescope Systems Division

By 2005, the OWL study was completed and reviewed by a panel of experts. At that time, the concept was validated as a cost-effective way to build an Extremely Large Telescope (ELT). However, as the wheels kept turning, and a price tag of € 1.5 billion was attached to it, the ESO backed away.

OWL’s design called for a 100 meter diameter mirror, built out of 3264 segments. It would have had unequalled light-gathering capacity, and the ability to resolve details down to a milli-arc second. (A milli-arc second is approximately the size of a dime, placed on top of the Eiffel Tower, and viewed from New York City.) That’s extremely impressive to say the least. And OWL would have operated in both visible light and infrared.

Everything about OWL’s design was modular, in an effort to keep costs down. Image: ESO Telescope Systems Division

The problem with OWL was the cost, not the design feasibility. Engineers still think the design is feasible. In fact, the construction of the mirrors was pretty well-understood, and perhaps the most challenging part of the OWL was the adaptive optics required.

It’s a fact of large telescopes that they have to be constantly adjusted to produce sharp images. This requires adaptive optics. The adaptive optics required for OWL would have pushed the state-of-the-art technology at the time.

Adaptive optics is a method of overcoming the distortions that affect light as they pass through Earth’s atmosphere. For extremely sensitive telescopes like the OWL, the atmosphere of Earth is problematic. The photons coming from the distant reaches of the Universe can be garbled by the atmosphere as they approach the telescope. Telescopes are built on mountain-tops to reduce how much atmosphere photons have to travel through, but that’s not enough.

This video explains how adaptive optics work, and how they helped the Keck telescope make new discoveries.

OWL’s mirror segments would have to be aligned to within a fraction of the wavelength (0.0005 mm for visible light) in order for the telescope to deliver good images. OWL’s adaptive optics would have achieved this by adjusting each of OWL’s 3264 segments rapidly, sometimes several times per second.

OWL’s design called for modularity, or “serial, industrialized fabrication of identical building blocks” to reduce costs. The manufacture of extremely large telescopes is expensive, but so are the transportation costs. All of the components have to be built in engineering and manufacturing centres, then shipped to, and assembled on, fairly remote mountain tops. OWL’s components were designed to be shipped in standard shipping containers, which simplified that aspect of its construction.

This graphic shows the sizes of the world’s telescopes superimposed over the OWL. By Cmglee – Own workiThe source code of this SVG is valid., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33613161

In fact, OWL could have begun operation before all of its mirrors were in place, and would have grown in power as more mirror segments were built and integrated. (Other telescopes, like the Giant Magellan Telescope (GMT) will be in operation before all of the mirrors are installed.)

In the end, OWL’s cost became too great, and the project was cancelled. The ESO moved on to the 39.3 meter European Extremely Large Telescope. But all of the work done on the design of OWL was not lost.

This artist’s impression shows the European Extremely Large Telescope (E-ELT) in its enclosure. The E-ELT will be a 39-metre aperture optical and infrared telescope sited on Cerro Armazones in the Chilean Atacama Desert, 20 kilometres from ESO’s Very Large Telescope on Cerro Paranal, which is visible in the distance towards the left. The design for the E-ELT shown here is preliminary. ESO/L. Calçada

Everything that we learn about telescope design trickles down to our next-generation of telescopes. That’s true whether designs like OWL get built or not. We’ll just keep building on our success, and keep building larger and more powerful telescopes.

The adaptive optics that OWL required were a challenge. But huge advances have been made on that front. And in the way of things, the manufacturing costs have likely come down as well.

OWL itself may never be built, but other ‘scopes are on the way. Telescopes like the James Webb Space Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope hold the same promise that OWL did.

And in the end, the contributions of those and other ‘scopes might surpass those promised by OWL.