Universiteit Leiden

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NASA/Desiree Stover

Mariska Kriek is back – but this time as a professor

She left Leiden after her PhD and now, 14 years later, she returns as Professor of Extragalactic Astronomy. Mariska Kriek investigates how galaxies originate and evolve. And she is eagerly awaiting the launch for the new James Webb telescope: ‘The coolest things we are going to find are those we’re not even looking for yet.’

Light from space tells a story

Kriek unravels the history of galaxies by collecting as much information about them as possible. ‘We do this through spectroscopy. We look at the fingerprints of different wavelengths in the light of these galaxies. By dissecting the light we can find out all kinds of things. This includes the mass, size, age, chemical composition, the presence of black holes and the birth rates and movements of stars. All this data together tells us how a particular galaxy was formed, and why it looks the way it does today.’

In 2008, Kriek won the Christiaan Huygens Science Prize for her PhD thesis, which she defended at Leiden University in 2007. Her PhD thesis focused on the evolution of galaxies in the young universe.

No more new stars, but why?

Kriek is particularly interested in finding out how and why some galaxies stop forming stars. This turns out to be quite a mystery. 'Stars are formed from ice-cold gas,' she explains. If a galaxy stops forming stars, you'd think that the gas has run out. But it's not as simple as that.'One of Kriek's PhD students discovered a number of galaxies that had just stopped forming stars, but still retained enormous reservoirs of cold gas.

Kriek: ‘Even the computer models did not fully understand why these galaxies had then stopped forming stars anyway. It tells us that star formation doesn't necessarily stop because the gas runs out, but also for another reason. But what?’

A new telescope, a new era

Kriek can still marvel at what is possible with today's technology. ‘When I started my PhD, I was staring at some blurred spectrum image and thought: How am I supposed to write a dissertation about this? But in twenty years, so much has happened. And when the new James Webb telescope is launched in December, we'll be taking another giant leap forward.’

According to Kriek, the new telescope is revolutionary on all fronts.  She is one of the few lucky scientists who is permitted a research project on the telescope. ‘We will soon be able to measure at different wavelengths, which will allow us to see new elements. We can also look deeper into space and the images will be sharper. In the infrared spectrum, we will even be able to observe several galaxies at once. The coolest things we are going to find, are the things we have not even been looking for because we do not yet know they exist.’

Headerphoto: The deployed primary mirror of NASA's James Webb Space Telescope looks like a spring flower in full bloom. Credits: NASA/Desiree Stover

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