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METIS in 500 words

METIS is the “Mid-Infrared ELT Imager and Spectrograph” and I will explain it by dissecting the complicated name:

Mid-infrared” refers to wavelengths between 3-20 micrometers. This range is also referred to as thermal radiation because things that are at room temperature emit the most light in these wavelengths. By looking at this wavelength range we can see objects in space that are at this temperature, about 300 degrees above absolute zero. These are, for example, planets that resemble the Earth, so not those hot Jupiter-like planets (that we have known for thirty years or so), but planets that may have an earth-like atmosphere and perhaps, yes… maybe even have a form of life. There is good hope that we’ll find an Earth-like planet in orbit around our closest star: Alpha Centauri. It is so bright that we have to be very careful when we observe it with METIS, otherwise our sensitive camera will be damaged. And that is exactly the challenge: block as much light as possible from the bright star until we can find the small planet nearby.

That is certainly the most spectacular use of METIS, but it is also the most risky one. Fortunately, there are many other things we can study with METIS. In our galaxy, the Milky Way, we will also make observations of the disks around young stars and the atmospheres of old stars. And in certain other galaxies we can also make observations in the mid-infrared light. In almost every galaxy there is a super-massive black hole in the center. And when that actively accretes matter, the surrounding swirl of gas and dust gets hot and at certain places it reaches room temperature so that we can easily see it in the middle infrared.

ELT” stands for “European Extremely Large Telescope” and that is the name of the largest telescope in the world that is now under construction. It is being built by a European organisation (the European Southern Observatory or ESO) on a mountain in the Atacama desert in Chile and will be ready in the mid 2020s. With its diameter of almost 40m, the area of that telescope will be larger than the areas of all current large telescopes combined! There is no company in the world that can produce such a large mirror and so the main mirror (the one that will be almost 40m in size) consists of 798 segments, each with a diameter of about 1.45m. And they all have to be placed in such a way that the whole mirror then becomes a parabola. Almost impossible, right?

Finally, “Imager and Spectrograph” refers to what the instrument will be able to do: record pictures and spectra. With the “Imager” we can for example take a real picture of an earth-like planet and with the “Spectrograph” we can analyze the light of that planet and compare it with models of atmospheres to discover what happens on that planet.

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