Universiteit Leiden

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ERC Advanced Grant for dark matter research

Dark matter. Something invisible that, according to calculations, comprises about 85% of the matter in the universe. With an ERC Advanced Grant of €2.5 million, Professor of Observational Cosmology Henk Hoekstra will map out even more precisely where this dark matter is to be found.

Dark matter is something that we cannot see, but that we know is there. At least, that is what astronomers can tell from the behaviour of stars in the outer parts of galaxies. Stars that would never move so fast if there wasn't a lot of unexplained mass floating around in the universe.

Distorted galaxies

But how do you track down something that is invisible? ‘Because dark matter has mass and therefore gravity, it also distorts the space around it', explains Henk Hoekstra, professor at Leiden University. ‘By studying the distortion of galaxies very closely, we can determine where this dark matter is located.’

One third of the sky

With this goal, the Euclid space telescope will be launched sometime in the next few years. This telescope works in a slightly different way than the well-known Hubble and James Webb telescopes. ‘Euclid has a much larger field of view. With a single Euclid image, we can capture about 120 times more Universe than a Hubble image. Over the course of six years, we hope to be able to map a third of the sky.’

By looking closely at the information we receive, we can already deduce a lot about the mass of galaxies, for example

Two billion galaxies

This is important, because only by looking at the big picture you can make good estimates about where the dark matter is exactly. ‘We would like to map the large structures of dark matter in our universe. And in order to do that properly statistically, we need to include about two billion galaxies in our research,’ Hoekstra says.

The gravity of ordinary matter

How will the 2.5 million euros from the European Commission help? Hoekstra wants to use the money from the ERC Advanced Grant to make Euclid's measurements as good as possible: 'A major hindrance in our search for dark matter is ordinary matter. Ordinary matter also exerts gravity and thus influences our measurement results. However, it is difficult to model and therefore difficult to compensate for.’

Telescopic self-reflection

‘I want to use the data we receive from Euclid to immediately make its own measurements more accurate. By looking closely at the information we receive, we can already deduce a lot about the mass of galaxies, for example. Then we can include it in our calculations and make the most accurate map of dark matter as possible,' Hoekstra explains.

Rocket required

For this, the telescope first has to get into space, and that turns out not to be so easy. Hoekstra: 'We were actually going to launch the telescope in mid-2023 on a Russian Soyuz rocket. But one day after my meeting with the European Commission, Russia invaded Ukraine.’ But Hoekstra remains positive and hopes to be able to hunt for dark matter in mid-2024 by launching the telescope on a brand-new Ariana 6 rocket.

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