E-ELT: The future giant telescope in the desert Print E-mail

ImageA mountain in Chile will be the site for the European Extremely Large Telescope decided the Council of the European Southern Observatory ESO in Garching, Germany. With a diameter of 42 m, this is the largest of the extremely large telescopes that are being considered for construction now. An interview with Roberto Gilmozzi, E-ELT Principal Investigator at ESO.



Which site was chosen for the E-ELT?

The ESO Council decided for a site called Cerro Armazones which is in the Atacama desert in Chile. It is very close to Cerro Paranal, the site of the existing ESO Very Large Telescope (VLT). This mountain is slightly more than 3000 metres high. It has very similar characteristics as Paranal’s.

How do you feel about that?

The decision was taken on the basis of the scientific performance of the various candidate sites. The Council has chosen the one that has the best overall atmospheric and astronomical parameters. So, as an astronomer, I am very happy with this choice.

What is the current status of the project?

The project is almost at the end of its phase B, the detailed design phase. We are writing right now the proposal for construction. That is the document that will be sent to our Council for approval in December this year. Before we reach the December milestone we will submit this proposal to an external review by an international panel of experts, and present it to our advisory committees.

What’s the size of the telescope?
It will have a diameter of 42 m, really extremely large. The main mirror will be made up of 960 segments, each of them 1.4 m across. They will be hexagonal and they pave the mirror like the eyes of an insect. The whole telescope will weigh just about 5000 tons. A sophisticated adaptive optics system will correct for the blurring caused by atmospheric turbulence. It will approach the performance of a telescope outside the atmosphere.

Why is the E-ELT so important?

It will keep Europe at the forefront of astronomy for a long time to come. This is the largest of the extremely large telescopes that are being considered for construction now. There are another two in the USA, one with 22 m and one with 30 m diameter. But the E-ELT with 42 m has the advantage of being a bigger light collector, making it possible to see fainter objects. Since it has a larger diameter, it will also have a higher spatial resolution, to resolve better details in astronomical objects.
E-ELT: The giant in the desert
 Credit: ESO.
Roberto Gilmozzi ESO
(Credit: ESO).
What are the science drivers?

There are many. Just to name two: one science case, that is very interesting to me is the search for Earth-like planets around other stars. This is the only telescope that might have the chance to find them. The other science case, on which I am also very keen, is to see the expansion of the Universe in real-time. With a high-resolution spectrograph on the E-ELT we can measure the expansion velocity today and repeat the measurement 10 and 20 years later. If the velocity has changed you know that the expansion of the Universe is accelerating.

Is there any interaction with other observatories?

A very strong one! One of the reasons to choose the southern hemisphere was to realize synergies with other observatories, with the VLT, the VLT interferometer, the Atacama Large Millimetre Array (ALMA) in Chile, and in the future also with the square kilometre array (SKA), a huge new radio telescope, or instruments from our colleagues in astroparticle physics, etc. We can look at the astronomical objects in all these different wavelength ranges and with different instrumentation and try to understand better the physics that governs their life and behaviour.
Do you have all the funds you need?

Not yet. The project has to be approved by our Council. And extra funds i(n addition to those ESO has in its budget every year) have to be found. There is a positive atmosphere and the member states are in the process of looking at their options. Let’s say that there is a cautious optimism that the funds will be found.

What is the timeline?

If the project is approved in December, the construction can start at the beginning of 2011. It is planned to last 7.5 years. In principle we can have first light in 2018. 
 Submitted by Dirk Lorenzen

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