Hawking - How massive are debris discs? Weighing a fundamental component of planetary systems

Our Solar System contains lots of 'debris', which refers to any solid object smaller than a planet: asteroids, comets, dust and dwarf planets (like Pluto) are all debris. Much of the debris in the Solar System is concentrated in the Asteroid and Kuiper Belts, which are more generally referred to as 'debris discs'. Such discs contain debris with a huge range of sizes, from tiny dust grains all the way up to asteroids and dwarf planets. Surprisingly, we can see debris discs around other stars too; modern instruments can see the dust in extrasolar debris discs, although the larger bodies (asteroids and dwarf planets) cannot be detected with current technology. This leads to a problem: we do not know how massive debris discs are, because their masses are dominated by the unseen large bodies. These debris discs look very different to our own Asteroid and Kuiper Belts, and establishing their masses would really help us to understand how planetary systems form, how they evolve, where exoplanets orbit, and how typical (or unusual) our Solar System is.

My proposed research combines brand new dynamical theory with cutting-edge data from the James Webb Space Telescope (JWST), to measure debris-disc masses for the first time. This is done by considering the interactions that occur when an exoplanet orbits close to a debris disc. These interactions affect both the disc shape and the exoplanet orbit, and depend on the debris-disc mass; I would use these interactions to measure debris-disc masses directly. This new method has the advantage that, unlike previous techniques, it does not require a lot of assumptions about unknown quantities. Specifically, I identify two types of known debris disc that are particularly susceptible to having their masses measured in this way: first, discs that are both narrow and elliptical in shape, and second, discs that are both wide and contain a gap. I am a member of several JWST programmes, which will look for exoplanets near these discs before the fellowship starts; as a fellow I would then measure the debris-disc masses by combining these observations with new dynamical theory. These masses would then be used to determine the sizes of the largest debris bodies (asteroids or dwarf planets) that lie within the discs; finally, these debris sizes would be used to test key aspects of debris theory and system-formation models.

In parallel to my scientific research, I also plan a large public-engagement programme to raise awareness of how vital mathematics is to almost all products and services that people rely on today. Without maths we could not design aeroplanes, build mobile phones, perform medical scans or understand the universe, but to many people maths can be boring, annoying or even scary. My aim is to show to young people that mathematics has many fascinating applications beyond what most people experience in their everyday lives; for example, try building a city or launching a rocket to Mars without maths. I propose to build fun, interactive computer software that demonstrates the diverse and exciting applications of mathematics to primary school pupils, to foster an early understanding that maths has enormous potential beyond people's day-to-day experiences. The aim is not to teach maths, but to provide a supplementary tool for teachers to show the amazing things that maths can tackle, to help demonstrate why maths is important and worth learning. Ultimately, it could even inspire the next generation of STEM students.