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Is there oxygen on exoplanets? New telescope finds out

To what extent does exoplanet Proxima b resemble our Earth? And is there some form of life present? Astronomers hope to find answers to these questions with the new European Extremely Large Telescope (ELT). An NWO research grant of €18 million will allow a Dutch consortium to continue building instruments for this telescope. 'We have a neighbouring star that we know has a world around it that looks like our Earth,' says lead researcher Ignas Snellen. 'Learning more about this exoplanet is incredibly exciting.'

In the middle of the Chilean desert, the Extremely Large Telescope (ELT) is under construction. With a mirror of 39 metres width, it will be the largest telescope in the world. 'It’s the telescope that captures the light,' says Snellen. 'The bigger the telescope, the more light it captures and the further you can see. But it is the instruments on the telescope that determine what kind of science you can do with it.'

With the ELT, astronomers can study quite faint objects in space and see them sharper than ever. 'Our neighbouring star has a planet that is very similar to Earth in size and orbit, called Proxima b. With the instruments we are building for the ELT, we can find out exactly what the properties of that world are.'

Building three instruments

Dutch astronomers at NOVA are collaborating on three instruments for the ELT. Of the mid-infrared instrument METIS, the Netherlands is project leader. 'With METIS, we can find out whether Proxima b has an atmosphere and what gases are in that atmosphere. We have been working on this instrument for about ten years. It will be the first instrument put into use.’

For the other two instruments, we will have to wait a little longer. MOSAIC is a multi-object spectrograph. It can observe hundreds of stars and galaxies simultaneously and make detailed spectra of them. 'For the third instrument called EPICS, we are really still in the early stages with studies on the instrument and the technical aspects.'

Artistic impression of ESO's Extremely Large Telescope (ELT). The instruments will be on one of the platforms.

In search of oxygen

Although the latter instrument will not be built until the mid-2030s, Snellen is very much looking forward to its measurements. 'With EPICS, we can look at reflected light. Instead of looking at one or two worlds, we can study a whole group of such objects. So not just exoplanet Proxima b, but also Earth-like planets around other stars. By the time the instrument is finished, I will be well into my sixties, but I am very much looking forward to it. EPICS and METIS are two instruments that will allow us to observe exoplanets very well.'

With EPICS' sharp images, astronomers will also get more information about potential life on exoplanets. 'We can look for oxygen, for example. That is incredibly interesting because oxygen is a big clue that there is life.'


Unlike the JWST, the ELT takes measurements from Earth. 'With the ELT's large surface area, we can capture more light and therefore observe fainter objects and look many times sharper than the JWST. The JWST's mirror has a diameter of 6.5 metres. The ELT is almost five times larger.'

But looking from Earth also has its drawbacks. 'When you look from space, you are not bothered by the Earth's atmosphere. A turbulent atmosphere sometimes makes it difficult to see some parts sharply.' That means certain parts of the spectrum can be seen much better from space. 'And JWST has a huge heat shield that keeps the telescope very cool. That gives much less noise compared to looking at thermal radiation from the ground.'

Combining data from telescopes

In about five years, the ELT will be ready for its first observations. 'The great thing is that we will then have the JWST, which is better in some things, along with the superior qualities of the ELT. We can then combine that data. That will be fantastic! We are going to learn so much about the first stars, the formation of galaxies and whether we are alone in the universe. Personally, I am particularly looking forward to learning more about Proxima b. That is very exciting.’

NOVA receives the NWO grant under the National Roadmap Large-Scale Scientific Infrastructure. The 18 million euros will allow astronomers to further develop the three instruments. They already received an earlier grant for METIS. This will allow them to finish the instrument and further develop MOSAIC.

About NOVA

The Netherlands Astronomy Research School (NOVA) is the partnership of the astronomical institutes of the universities of Amsterdam, Groningen, Leiden and Nijmegen. Top research school NOVA's mission is to carry out pioneering astronomical research, train young astronomers at the highest international level and share new discoveries with society. The NOVA laboratories specialise in building state-of-the-art optical/infrared and submillimetre instrumentation for the largest telescopes on Earth.

Text: Inge van Dijck
Images: ESO/L. Calçada

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