Charlotte Mason

Project title

Revealing Massive Stars at Cosmic Dawn

What is your project about?

How did we get here? How did the first stars form and transform our universe from the dark soup of hydrogen and helium created shortly after the Big Bang? Some theoretical models predict that these stars were more massive and hotter than stars today, producing energetic radiation that ionized hydrogen gas and triggered the universe's final phase transition, "Reionization." Yet direct evidence for such giant stars remains elusive, and we still do not know whether they alone powered reionization, or if other sources, such as accreting black holes, played a role. This project will use new data from a large survey I am leading with the James Webb Space Telescope, providing some of the most detailed spectra ever taken of early galaxies. We aim to detect signatures of massive stars, infer how their energetic radiation escaped and impacted their surroundings, providing new insights into how our cosmos evolved from darkness into the diversity we see today.

How did you become interested in your particular field of research?

I was interested in physics and astrophysics from a young age, as a way to understand the world around us. One of the aspects that most drew me to my field of research is being at the forefront of exploration in our universe – with the James Webb Space Telescope we are detecting light from some of the most distant, and thus earliest, galaxies in the universe, that no human has seen before. This observational frontier brings many surprises, and we are always learning new things as we seek to understand these observations.

What are the scientific challenges and perspectives in your project?

One of the biggest challenges in observational astrophysics is that we can only observe a "snapshot" of a particular galaxy – at a particular time and from one angle – and from many such snapshots of different galaxies we must piece together a coherent understanding of their general properties. In this project, a particular challenge is disentangling the contributions of different physical processes to a galaxy's spectrum: massive stars, accreting black holes, and gas inside and around the galaxies. The depth and quality of our new James Webb Space Telescope dataset is finally sufficient to separate many of these effects.

What is your estimate of the impact, which your project may have to society in the long term?

Astrophysics addresses some of the biggest questions about our place in the Universe. This project aims to push the boundaries of our understanding of the earliest stages of the universe, helping to better understand "how did we get here?". Beyond the science itself, astrophysics drives technological progress in data analysis techniques and detector capabilities, with broad applications across science and industry. Astrophysics also functions as a "gateway" discipline, inspiring young people to pursue careers in science and technology, which brings lasting value for society.

Which impact do you expect the Sapere Aude programme will have on your career as a researcher?

In the past few years my research has been primarily focused on theoretical modelling, but the Sapere Aude programme offers me the opportunity to build a dedicated observationally-focused team to work on the new James Webb Space Telescope data we are collecting. This will allow me to grow my research expertise in new directions and facilitate international collaboration, consolidating my position in the field.