Let there be light: how did the universe’s first stars form?

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Charlotte Mason


Associate Professor


University of Copenhagen


DKK 5,000,000




Semper Ardens: Accelerate


There is a missing chapter in our Universe’s history: we cannot see the first stars and galaxies that lit up the Universe. How and when did galaxies form from the primordial soup of atomic hydrogen and helium to produce the diversity we see today? This is still an open question and a frontier in astrophysics. In the last few months, the James Webb Space Telescope (JWST) has expanded our horizon to this ‘Cosmic Dawn’, and early results have challenged theoretical models of how stars and galaxies formed. This project aims to constrain how stars formed in the early universe, by measuring the demographics of stars and the efficiency of star formation in early universe galaxies from revolutionary new JWST data.


How did we get here? Around 100 million years after the Big Bang, theoretical models predict the first stars and galaxies formed in our Universe. As they burned and exploded, the stars created every atom in our world, except hydrogen and helium, and the early galaxies were the building blocks for galaxies like our own home, the Milky Way. But all of this is untested – until now we have not been able to see the earliest galaxies, so we do not have concrete evidence for how these first stars and galaxies formed.


As we look into space we can actually see back in time - as light takes so much time to travel across the universe, when we look at very distant galaxies we are seeing them as they were when the light was emitted from them - billions of years ago, though this requires the most powerful telescopes on Earth and in space. New infra-red technology on the James Webb Space Telescope (JWST) means that we can see further back in time than ever before, to the period when the first galaxies formed. We will analyse the first JWST observations of some of the earliest galaxies forming in the universe. We will measure these galaxies’ high energy starlight and its absorption by dust to infer the demographics of their stars and the efficiency with which stars form in early galaxies. By comparison to theoretical models and simulations we will develop a new understanding of how the first stars formed.

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