Future science

What will the Extremely Large Telescope reveal about the Universe?

6 March 2020
What you’ll discover in this blog post:
  • What makes the Extremely Large Telescope (ELT) a massive technological leap forward compared to its predecessors
  • How the ELT could help us to find alien life and learn more about black holes
  • How the ELT will be our window to the “Dark Age” of the Universe
  • Why the ELT will lead astronomers to ask new questions that they haven’t even thought of yet
The Extremely Large Telescope (ELT) will massively advance ground-based astronomy by tackling the biggest scientific challenges of our time. With such a powerful telescope, astronomers will be able to examine the Universe in unprecedented detail. This week, we caught up with ELT Programme Scientist Michele Cirasuolo to learn exactly what this new telescope will be able to tell us about the Universe.
Interview with
Michele Cirasuolo
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Q. Michele, could you first tell us what led you to join ESO and become Programme Scientist for the ELT? How did you end up helping to coordinate the 'world’s biggest eye on the sky’?

A. A few years ago, I was working on instrumentation for the Very Large Telescope (VLT), so when the opportunity arose to become Programme Scientist for the ELT, it kind of felt like moving to new heights. The ELT is a gigantic step forward compared to the VLT. The instruments on the VLT are already state of the art, but the ELT is just at another level; it will open up so many more frontiers in astronomy and I wanted to be able to help ESO and the scientific community steer the direction of this amazing machine.

I first trained as an astrophysicist. But during my postdoc at Edinburgh University there was an opportunity to take on more of an instrument scientist role where I could learn more about instrumentation. Working on the ELT allows me to combine these two interests of science and technology; we are building an ambitious telescope that will solve many astrophysical problems, and in doing so, we need to combine our knowledge of theory, observations and engineering to really push forward the boundaries of technology.

Q. ELT Programme Scientist sounds you have a lot on your plate — could you tell us a little about what you do on a day-to-day basis?

A. The short answer: I jump from meeting to meeting!

I act as the hub between all of the main stakeholders to ensure that we get the best science from the ELT. Each ELT instrument has its own Project Scientist and I coordinate the work between all of them. I listen to what the science community wants and explain to them what the ELT will be able to do. I report to funding bodies to keep them updated on our progress. And I present to ESO management to keep them in the loop of our progress and our set-backs. So all-in-all I have a broad view of what’s happening across the entire programme, allowing me to transfer information from one party to another, and solve problems by looking at the big picture.

Q. The ELT is a massive leap forward in telescope technology, size and observing power. Exactly how will it compare to current telescopes?

A. It is an understatement to say that the ELT is a massive leap forward. In the past, we have typically progressed telescopes by doubling the size of the main mirror. From one metre, to two to four and now we’re up to eight metres with the VLT. But the ELT primary mirror, M1, will be almost forty metres wide – a truly astonishing jump in terms of both science and technology.

Controlling such a huge mirror that is made up of almost 800 individual smaller mirror segments, is such a technological challenge. The telescope itself will be a massive structure weighing more than 3500 tonnes, with five giant mirrors in its optical train, known as M1 to M5. But the accuracy with which we look at astronomical objects will be on the order of a few nanometres, or 0.000000001 metres. Achieving this accuracy is extremely challenging because while observing the telescope will move to point and track different astronomical objects, and we will have to contend with gravity, temperature changes, vibrations due to wind, and the turbulence of Earth’s atmosphere. In order to compensate for all these effects and obtain sharp images each individual mirror segment will be controlled and moved with motors at a very fast rate. For example, more than 5300 motors control the shape of M4, which can receive up to 1000 commands per second. This will ensure that the mirrors are constantly in precisely the right position to deliver the best science.

From a more scientific perspective, the VLT is an incredible machine, but it is not powerful enough to see very faint objects, so we need the ELT. Right now we’re just seeing the tip of the iceberg, and the deeper we go, the more we will discover.

Right now we’re just seeing the tip of the iceberg, and the deeper we go, the more we will discover.

Q. ESO has been at the forefront of ground-based astronomical innovation for a long time — could you tell us what existing ESO telescope technology has made the ELT possible?

A. The ELT builds on the shoulders of the VLT, and is really only possible thanks to the expertise we gained from developing and operating it. The VLT taught us how to align mirrors, how to do adaptive optics, how to build huge structures, how to deal with extensive manufacturing processes and specifications, how to operate such a state-of-the-art facility, how to deliver the best science, and much more.

So we already had a lot of expertise in terms of instruments, serving the science community and providing data. But at the same time almost every part of the ELT is nothing like anything that’s been done before. A lot of new technology has had to be developed and it has resulted in some enormous Research and Development projects for both the telescope and the instruments, which are also huge compared to the VLT’s.

Q. So what instruments will the ELT have, and are you already making plans for the first observations? If not, when does that process begin?

A. We considered all the possible science topics that the ELT could address, and then planned instruments to tackle specific problems, but also instruments that could complement each other.

The first instruments, HARMONI and MICADO, will later be joined by METIS and MAORY.
Credit: ESO

When the ELT is first ‘switched on’, it will be using two instruments both using adaptive optics — MICADO with its adaptive optics module MAORY and HARMONI with its Laser Tomography Adaptive Optics module. HARMONI is a spectrograph and MICADO is an imager. Next in line is METIS, a mid-infrared imager and spectrograph combined. A second wave of instruments will follow, based on our “instrument roadmap”, for which we have already identified a high-resolution spectrograph (HIRES) and a multi-object spectrograph (MOSAIC).

Each instrument is built by a consortium that gets guaranteed observing time to tackle specific science questions. So the consortia are already planning how best to make these observations. The rest of the observing time is offered to the astronomical community to make their own discoveries, and yes, we are already planning for these.

We are exploring how best to use the instruments, what their performance will be, and how the data will be used, extracted and archived to be used by others. Once the instruments are built and the ELT is up-and-running we will test their performance and make sure that we have this kind of infrastructure ready for the whole community to make the best use of the ELT. We will organise workshops and hands-on demonstration to help people with this.

Q. The ELT will give us an unprecedented view of the Universe. One frontier that it will allow us to explore is the very early history days of the Universe — the so-called “Dark Ages”. What might we learn?

The jump from previous telescopes is so big that wherever we look we will find something new.

A. Whatever the ELT observes will be a new discovery. The jump from previous telescopes is so big that wherever we look we will find something new.

The first objects in the cosmic Dark Ages are very faint and distant; the light that we see from them left them 13 billion years ago so we see the universe as it was at a very early age. The ELT will be able to collect this light much better than the VLT, so that we can start to resolve these objects to find out what they’re made of and how they work.

The ELT: The world’s biggest eye on the sky.
Credit: ESO

Q. One of the hottest topics in astronomy is exoplanetary science. How will the ELT change our understanding of other worlds?

A. Pretty much all space telescopes and existing ground-based telescopes are now being used to search for stars with planetary companions that could possibly host life. We have already found thousands of exoplanets orbiting all sorts of different stars. But we need to go a step beyond finding out the number of exoplanets and their respective sizes, and start really characterising their atmospheres to see whether they may be suitable for life. We need the enormous power of the ELT in order to do this. So maybe the ELT will help us find new Earths!

Q. The VLT notably produced the most detailed view ever of the surroundings of the supermassive black hole lurking at the heart of our galaxy. Will the ELT be able to go further?

A. The VLT has enabled some incredible research on the centre of the Milky Way, especially using a star called S2 that lies close to the black hole. But there are still many open questions – for example whether the black hole is spinning.

The ELT will have a much higher angular resolution, meaning that it may be able to pick out stars even closer to the black hole and accurately measure their positions and radial velocities. This would allow us to test even better the surroundings of a black hole, to understand the physics of general relativity. The ELT will also be powerful enough to study supermassive black holes in other galaxies, for example by looking at the gas swirling around them. In this way, we will find out whether the black hole in the Milky Way is special in any way.

Q. The discoveries made using the ELT will probably lead astronomers to ask new questions they haven’t even thought of yet — can you make a guess at what areas these might be in?

A. My expectation is that people will start asking a lot more about the distant Universe. So far our study of the distant — and therefore early — Universe is limited by our inability to resolve the individual building blocks. At the moment, many distant galaxies look like blobs and we don’t really understand much of their physics. The ELT will allow us to resolve the individual components of these objects and make studies similar to those we can already make in the nearby Universe.

What this means is that we will understand how physics evolves over time. For example, there is a set of fundamental physical constants that describe a lot of what we know about the Universe, and according to the laws of physics they are constant, not changing with time. With the ELT we will be able to directly test this and see whether these were the same in the past or whether they have changed over time. This will open up a new era in fundamental physics and maybe rewrite the physics textbooks. Also in cosmology, we will better understand dark matter, dark energy and the expansion of the Universe, and actually I think it will open up entirely new fields of research.

What excites me the most are the moments when we open that eye and discover something completely unexpected.

Q. Lastly, what ELT future science are you most excited about?

A. What excites me the most are the moments when we open that eye and discover something completely unexpected. Discovering unknown bits of the Universe and finding things we’ve never even thought about. This will trigger theoreticians to find explanations, observers to verify and find new targets, and engineers to continue pushing the boundaries of technology.

This fantastic project has been made possible through the collaboration, coming together and ingenuity of all of ESO, including management, engineers and scientists, as well as industry and the scientific community. It’s truly a pan-European effort and is a good example of how Europe should work; no country could have taken on this project alone, and ESO is showing that when we collaborate, we can make great things happen. It is extremely exciting to be part of this.

Numbers in this article

0.000000001 Accuracy with which the ELT will look at astronomical objects (in metres).
7 Number of instruments the ELT can host when it is switched on.
8.1 Diameter of a single VLT Unit Telescope (in metres).
39 Diameter of the ELT main mirror (in metres).
798 Number of individual mirror segments that make up the ELT’s primary mirror.
1000 Number of times per second we command M4 to change its shape in order to get sharp images.
> 3500 Mass of the ELT (in tonnes).
> 13 billion Age of objects we see in the “dark ages” of the Universe (in years).

Biography Michele Cirasuolo

Michele Cirasuolo is the Programme Scientist for ESO’s Extremely Large Telescope (ELT) — the largest optical/near-infrared telescope in the world, which is currently under construction. He has plenty of experience with astronomical instrumentation, including time spent as Principal Investigator of a multi-object spectrograph for the Very Large Telescope (VLT). With a PhD in astrophysics and two decades of active research under his belt, Michele has published extensively in the field of galaxy formation and evolution across cosmic time. In his spare time he enjoys martial arts, tennis, sailing and salsa dancing.