Looking back at the universe’s wild youth
Inaugural lecture Mariska Kriek image: NASA, ESA, CSA, Ivo Labbe, Rachel Bezanson, Alyssa Pagan
How do galaxies form? Thanks to major technological advances, astronomers are gaining ever-deeper insights, says astrophysicist Mariska Kriek in her inaugural lecture. ‘It’s almost unbelievable how many significant discoveries the James Webb Space Telescope has already yielded in such a short time. And the best is yet to come.’
Galaxies take billions of years to form. ‘Astronomers don’t live long enough to watch galaxies grow or change – give or take the odd rare supernova’, Kriek explains. But because the light from distant galaxies takes billions of years to reach Earth, astronomers can effectively look back in time and see what galaxies looked like in the distant past. And with today’s advanced telescopes, they can look all the way back to the universe’s earliest galaxies.
The early universe
Kriek studies how galaxies formed in the early universe. By observing galaxies of different ages, she researches how they evolve. ‘It’s like solving a puzzle. I look back to about two to three billion years after the Big Bang.’ Back then, the universe was much more compact, she explains. ‘The universe is constantly expanding, so everything was smaller then. There was plenty of gas available to form stars, but it hadn’t clumped together as much.’ Compared to today, this was a far more dynamic time for the universe. ‘There are far fewer galactic collisions now, and star formation is slowing down. We’re living in a rather boring period of the universe.’
Right place, right time
Technological progress has had a ‘tremendous’ impact on her work, says Kriek. She began her PhD research in 2003, just as a new generation of infrared technology became available on the world’s largest ground-based telescopes. After completing her doctorate, she gained access to a new camera on the Hubble Space Telescope. Most recently, she’s been able to peer deep into the universe with the James Webb Space Telescope. ‘I’ve been incredibly lucky – I was in the right place at the right time.’
Hubble minds
Kriek is still amazed by what the James Webb Telescope can do. ‘The level of detail is astonishing. We’re finally able to answer questions that have puzzled us for years.’ For instance, she and her colleagues recently discovered that mature galaxies in the early universe were originally rotating discs. Over time, collisions with smaller neighbouring galaxies caused them to lose their flat structure and become more spherical. ‘And this is just the beginning because there is a lot that we still don’t understand. We’re still interpreting Webb’s data with our ‘Hubble minds’. There’s so much more to uncover.’
Breakthrough on the horizon
One breakthrough Kriek expects soon is a better method for determining the mass of galaxies. ‘Until now, we’ve mostly observed the heavy stars and estimated how many lighter stars there must be. This is based on the ratio we see between heavy and light stars in our own Milky Way. But that ratio may not be the same everywhere in the universe. We’ll soon be tackling this with extremely deep observations from Webb and, for the first time, will directly measure how many light stars there are for every heavy star in distant galaxies.’
Mariska Kriek will give her inaugural lecture ‘Voorbij het Eindeloze Heelal’ (Beyond the Endless Universe) on Friday 20 June. The lecture will also be available via a live stream.