Dust from comets and asteroids is being kicked up in the middle of planetary systems around other stars, and this project will build computer models to figure out what that dust reveals about the hidden planets. This matters because the warm dust—called exozodi—sits right in the habitable zone where Earth-like planets might orbit. Current models cannot properly account for the combined effects of gravity, radiation, collisions, and gas drag on this dust. Without better models, astronomers cannot tell whether the dust is a harmless cloud or a sign of violent bombardment that could sterilise a planet. The research will develop a hybrid approach: N-body simulations track comets, while a kinetic code follows the debris they release. The team will also model how gas flows and how debris accretes onto planets, potentially altering their atmospheres. They will test these models against real observations from LBTI, JWST, and ALMA. If successful, the work will help distinguish between different dust sources and improve predictions for systems that cannot yet be imaged directly. This is fundamental science with a clear downstream goal: exozodi dust is noise that can blind telescopes searching for habitable exo-Earths, so understanding it is a necessary step before those planets can be found.
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Debris disks are the disks of asteroids, comets, dust and gas that surround nearby stars. Such debris is found in the cold outer (>30au) region of planetary systems to ~20% of stars. A similar fraction of stars host warm dust in their inner (<30au) region, which are known as exozodi by analogy with the solar system’s zodiacal cloud. Exozodi dust resides in the middle of the region where the star’s planets should reside and its structure is expected to be strongly influenced by the planetary system architecture, which is generally unknown. It has recently become possible to spatially resolve and characterise exozodi with LBTI, JWST and ALMA. This project aims to develop modelling techniques to determine the structure of exozodi expected for a given outer debris belt and planetary system. Current exozodi modelling techniques are limited by the need to combine gravitational and radiation forces with collisions and gas drag. This proposal will develop an approach that the PL has pioneered, in which N-body simulations trace the evolution of comets with debris released from them being passed to a kinetic code to follow its evolution due to collisions and radiation forces. The areas of development include: (1) exploration of planetary system architectures, development of a Monte Carlo scattering model to circumvent N-body simulations; (2) incorporation of planetary perturbations (ejection and resonant trapping) into the kinetic code via empirical functions; (3) following gas released using a hydrodynamic code and incorporating its influence on dust evolution through the kinetic code; (4) following accretion of debris onto planets to assess mass accretion and its effect on planetary atmospheres. The models developed will be applied to cutting-edge observations of exozodi that the project has access to (from LBTI, JWST and ALMA) to set unique constraints on the planetary system architectures of nearby stars. This will result in improved understanding of exozodi formation mechanisms (e.g., distinguishing between cometary and P-R drag replenishment mechanisms) and this will be used to make better predictions for systems where imaging is not yet possible. This is vitally important for our search for habitable exo-Earths, since exozodi provide noise that can hinder exo-Earth imaging while also being a signature of bombardment that can affect planetary habitability.
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