All about the Thirty Meter Telescope (TMT)

8 Apr

The Thirty Meter Telescope (TMT) will help solve some of the deepest mysteries of the universe and will be the largest, most advanced telescope ever built when it opens.

TMT has also been in the news off and on for a number of years as the project has moved through its proposal and design phases, dating back to 2003.

But recently it has been in the news in a big way (particularly in Canada), as Prime Minister Stephen Harper and Industry Minister James Moore announced that the Canadian government would provide an additional $243.5 million (approx. $200 million USD) over 10 years in funding for the construction of the next-generation telescope.

This money will be spent primarily in three areas: construction of the metal frame for the telescope dome (to be built by Dynamic Structures Ltd.); Supplying the advanced adaptive optics system, a centrepiece of the TMT design (the National Research Council of Canada is managing this), and; operating costs.

Canada already contributed about $30 million during the design phase, and the Association of Canadian Universities for Research in Astronomy (ACURA) has played a significant role – alongside the University of California (UC) and the California Institute of Technology (Caltech).

What follows is a plain language overview of the TMT project and what the Canadian funding means for it.

A schematic of the Thirty Meter Telescope (Source: TMT).

A schematic of the Thirty Meter Telescope (Source: TMT).

The Thirty Meter Telescope will be, in short, the largest and most advanced ground-based optical observatory ever built when it is completed sometime in 2022.

The project is led by a consortium of UC and Caltech. Those two schools between them account for a 25% stake in the project. Japan is also on board with a 20% stake. Canada comes next, with the $243.5 million accounting for a 15-20% stake. China and India each have a 10% stake.

With Canada’s contribution in place, the TMT has achieved 80% of the capital funding required, and the team continues to negotiate with other potential partners to secure the remaining funds. Construction though is underway, with the ground-breaking that took place in October 2014 officially kicking it off.

There are whispers the U.S. will come on board via a National Science Foundation (NSF) grant, but as yet that hasn’t happened.

TMT will be built atop the Mauna Kea volcano in Hawaii, with an elevation of about 4 kilometers.

The observatories atop Mauna Kea, Hawaii include, from left to right foreground:  the UH 0.6-meter telescope (small white dome), the UK Infrared Telescope, the UH 2.2-meter telescope, the Gemini Northern 8-meter telescope (silver, open) and the Canada-France-Hawaii Telescope. On the right in the background are the NASA Infrared Telescope Facility (silver), the twin domes of the Keck Observatory and the Subaru Telescope (Source: University of Hawaii).

The observatories atop Mauna Kea, Hawaii include, from left to right foreground: the UH 0.6-meter telescope (small white dome), the UK Infrared Telescope, the UH 2.2-meter telescope, the Gemini Northern 8-meter telescope (silver, open) and the Canada-France-Hawaii Telescope. On the right in the background are the NASA Infrared Telescope Facility (silver), the twin domes of the Keck Observatory and the Subaru Telescope (Source: University of Hawaii).

In telescopes, size matters, and so the TMT’s primary mirror at 30m (98 feet) will be three times larger than the current largest, the Gran Telescopio Canaris (10.4m, opened in 2007) at La Palma in Spain’s Canary Islands. The extra diameter will provide TMT with ten times the light collection ability.

The same size comparison holds true for the twin W. M. Keck Observatories (10m each), which will coincidentally be TMT’s neighbours at Mauna Kea. And while second in size, Keck is often considered one of the most advanced optical telescopes currently in operation thanks to the highly advanced adaptive optics they were retrofitted with about a decade ago (more on adaptive optics later). Keck 1 opened in 1993 with Keck 2 following in 1996.

Another famous telescope – perhaps the most famous – is of course the Hubble Space Telescope, launched in 1990. TMT will have 144 times (!!) the light collection ability over Hubble’s 2.4m mirror. TMT will also provide about 10 times better image resolution.

The Horsehead Nebula (Source: NASA/Hubble Space Telescope).

The Horsehead Nebula (Source: NASA/Hubble Space Telescope). TMT will have 144 times more light collection and 10 times better resolution than Hubble.

Though by the time TMT is completed, there will be other kids on the telescopic block.

The Giant Magellan Telescope at Las Campanas Observatory in Chile will likely have opened – it’s currently looking to be completed in 2021. Though at 25.4m, the GMT’s rein as world’s largest telescope will be short-lived. Of course, 25.4m is nothing to sneeze at – it will still be 2.5 times larger than the present-day biggest.

Similarly, TMT will only be the world’s largest for a few short years. Sometime around 2024-2025 the European Extremely Large Telescope (don’t you love the naming convention for these bad boys?) is expected to be completed at the European Southern Observatory (ESO) in the Atacama Desert, Chile. The E-ELT’s primary mirror will be fully 39.3m in diameter.

These three mammoth ground telescopes – the GMT, TMT, and E-ELT – represent a generational leap forward in terms of size, technology, and ability to peer deeper into the cosmos than ever before.

As a scale comparison, imagine a professional baseball stadium. If the TMT were placed on the pitcher’s mound, the primary mirror would nearly fill the entire infield. The structure is also 22-stories tall.

But why does size matter so much?

It matters because the size of the mirror is directly proportional to the amount of light the telescope has the ability to collect. And more light means the telescope is able to produce sharper images and detect fainter objects, allowing the astronomers to see objects and detail that otherwise wouldn’t be possible.

In your own life, consider the difference between a point and shoot camera and a D-SLR. In some cases the D-SLR has a better sensor than the P&S, but not always. So why does the D-SLR capture better images (particularly in low-light), assuming an equivalent sensor? Because the optics in front of the sensor capture more light, allowing the shutter to fire faster, and in turn create a sharper image. (I realize this isn’t a complete analogy, but I hope it sheds some [pardon the pun] light on why size matters.)

But, if it’s so important to have telescopes collect the maximum amount of light, why haven’t they been built this large before? A couple reasons.

First, as it often boils down to, is money. Building large telescopes is expensive (both TMT and E-ELT come with a total price tag between $1 and $1.5 billion each). But money alone only really tells part of the story here.

The underlying basis for why telescopes haven’t been built this large before is the second reason: technology. The relevant advances in technology are similarly revealed mainly in two places: segmented mirrors and adaptive optics.

Segmentation allows huge mirrors to be broken down into smaller pieces, which in turn allows for more straight forward construction, transportation, maintenance, and so on – all of which reduces cost. Large mirrors are extremely difficult to manufacture, heavy to support, and challenging to move around. For instance, could you imagine a 30m single piece of glass being moved up the side of a 4km tall volcano in Hawaii, to say nothing of getting it to the island in the first place?

TMT has two additional mirrors: a secondary (3.1m) and a tertiary (elliptical, 3.5×2.5m). The secondary mirror is placed above the primary mirror in order to collect the light from it. The secondary mirror then reflects the light back down towards the tertiary mirror, which directs the light to the instrument suites.

The 30m TMT primary mirror will actually be made up of 492 smaller mirrors. Each hexagonal piece of glass being 1.4m long corner to corner, spaced 2.5mm apart, and 4.5cm thick.

It’s worth mentioning though that TMT won’t be the first telescope with segmented mirrors; it was pioneered on Keck, and since used on other observatories as well, including the Gran Telescopio Canaris. GMT, E-ELT, and the next generation James Webb Space Telescope (set to launch in 2018) will all employ segmented mirrors, too.

But mirrors, no matter how large, won’t do you much good if you can’t get a clear view of the sky – and that’s where adaptive optics comes in.

Any telescope on Earth has to contend with the atmosphere. That blanket of layers of fluid air, all swirling around and wreaking havoc on anyone trying to get a clear view of objects in space – particularly small or faint objects, which coincidentally are the focus of a great deal of astronomy nowadays.

Even with your own eyes you have to contend with atmospheric turbulence if you happen to go out stargazing. That twinkling you see when you look at stars? That is actually caused by turbulence in the atmosphere distorting the light as it passes through (the stars don’t really twinkle at all, at least not for the purpose of this discussion).

Telescopes have to contend with the same interference, and the result – if left uncorrected – are blurry images that lack the required level of detail that astronomers require to push the frontier of understanding further forward.

In order to overcome this, a way has been devised to correct for the atmosphere by manipulating the shape of the mirrors in the telescope. Two corrective mirrors in TMT will have highly precise actuators attached, which will be able to very finely reshape each mirror in real-time to create a clear image.

Left: The Galactic Center without adaptive optics (Source: Keck Observatory). Right: The Galactic Center and central black hole (labeled Sgr A*) with adaptive optics. (Source: Keck Observatory and the UCLA Galactic Center Group).

Left: The Galactic Center without adaptive optics (Source: Keck Observatory). Right: The Galactic Center and central black hole, Sgr A*, with adaptive optics (Source: Keck Observatory and the UCLA Galactic Center Group).

The physics behind this technology, in a nutshell, is that when light is disturbed by the atmosphere it creates a distortion in the light wave. By reshaping the mirrors, an opposite distortion can be created in the telescope, cancelling out the atmospheric distortion.

The TMT’s actuators are controlled by a computer system, which in turn relies on a system that measures atmospheric turbulence. This measurement is accomplished by either pointing the telescope towards a guide star or firing a laser beam into the sky to create an artificial star, which the telescope can then image in order to measure the distortion and correct for it in real time.

Similar to segmented mirrors, TMT isn’t the first telescope to make use of a new technology. Others, including Keck, have been retrofitted with these optical systems as the technology has developed over the last decade. TMT is however the first telescope ever to be constructed with adaptive optics as a core piece of the design.

TMT, many like other telescopes, is also being constructed in a place where the impact of weather (including cloud cover) will be minimized. In being on top of a mountain 4km above sea level, TMT will not have to deal with as much weather as it would at a lower elevation. Being higher up also helps to reduce some of the atmospheric distortions, as the thickest part of the atmosphere is the part closest to sea level.

An illustration of the Thirty Meter Telescope's laser guide system (Source: TMT).

An illustration of the Thirty Meter Telescope’s laser guide system (Source: TMT).

More light, higher resolution, clearer view – what do they hope to find?

Astronomers working on TMT will have a full suite of scientific instruments at their disposal, so the telescope will essentially be able to be used to study anything and everything in the cosmos. But in terms of ushering in new discoveries, in broad strokes, TMT will be ideal for studying the origin of the universe and exoplanets.

Understanding the nature of the universe, how it – and by extension we – ended up here is a significant question for science and astronomy to try to unravel. TMT will take full advantage of its massive mirror to peer back in time and capture the faintest light from the earliest moments following The Big Bang. By observing how ancient stars and galaxies formed, it will advance our understanding of why things are the way they are, and inform what the forces at work in the universe are today. TMT will also help to fill in gaps about the structure of the universe and the role that dark matter plays.

In terms of exoplanets, TMT will have the resolution to directly image worlds orbiting other stars. Using spectroscopic instruments, astronomers will also have the ability to measure the composition of those worlds – and whether they could be hospitable for life.

Thirty Meter Telescope will perceive things that no other human-built technology has ever been able to see. In so doing TMT will help to answer two of the most fundamental questions of our existence: how did we get here and are we alone.

The next generation of discovery is just beyond the horizon today, but it’s exciting to know as a human that before long, we’ll have it in our sights.

As a Canadian, it’s exciting to know that my nation will play a significant role in those discoveries and the benefits that follow from being a leader in research and technology development.

I joined Jerry Agar on Toronto radio station CFRB Newstalk 1010 to describe TMT. Listen here:

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One Response to “All about the Thirty Meter Telescope (TMT)”


  1. » Celebrate Hubble’s 25 years in space @HarrisonRuess - April 23, 2015

    […] Hubble’s direct successor in space will be the James Webb Space Telescope, set for launch in 2018 – though Hubble is still expected to be in operation. Numerous next generation ground-based telescopes will also come online between 2020-2025, including the Thirty Meter Telescope (read in detail about TMT here). […]

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