Planetary formation and atmospheres
In this research area we investigate everything from the earliest formation of planets via dynamic collisions, to the atmospheres and characteristics of solar system planets and exoplanets. Exoplanet science is incredibly diverse and the thousands of discovered exoplanets present a wide range of research questions to explore. We use high performance computing to simulate the collisional dynamics that help form, or destroy, planets; develop complex multi-dimensional models of planetary atmospheres, their dynamics and chemistry; and analyse observational data from state-of-the-art telescopes to understand the nature of planets in our galaxy.
Thousands of exoplanets, planets orbiting other stars, have been discovered, most of which are surprisingly different from our solar system planets. Observations provide snapshots in time for different planetary systems and provide empirical evidence for the physics and chemistry of formation and atmospheric evolution. But we also require advanced simulations to fill in the gaps in time tracing processes from the earliest points in formation, dynamical migration, and down into the planetary atmospheres tracing chemical species across phase transitions and their feedback on the observed parameters.
Planet Formation
We develop state-of-the-art numerical methods that include the most realistic model of planetestimal evolution to date. Our goal is to develop a complete account of planet formation. This technique is highly efficient, and able to evolve newly formed planetesimals all the way through to planets. The results connect the final two stages of planet formation and capture feedback processes in which evolving protoplanets can replenish the reservoir of planetesimals. During the course of this work answers to many questions surrounding planet formation emerge, e.g., a realistic collision evolution model for planetesimals allows for accurate growth timescales to be calculated, which in turn determines whether giant planet cores can plausibly form from the gradual growth of planetesimals or if some faster mechanism is required. In addition, our research predicts the amount of debris produced by planetesimals during planet formation, which is vital to interpret observations of protoplanetary disks and our own solar system.
Links to High-performance scientific computing and AI
Atmospheric Modelling
Once a planet is formed its structure and properties can change with time, especially for small rocky planets that are unable to hold onto their primordial hydrogen/helium atmospheres like those of the gas giants. We are developing climate models of various complexity to understand the physical and chemical mechanisms driving the atmospheres of the planets in our solar system and exoplanets. Our research explores topics such as atmospheric dynamics, convection, cloud and haze formation, lightning, habitability and others. We are collaborating closely with the Met Office and actively contributing to the development of the UK's next-generation atmospheric model, LFRic. We are leading the application of LFRic to extraterrestrial climates and participating in international model intercomparison projects for exoplanets.
Links to High-performance scientific computing and AI
Atmospheric Observations
In the Astrophysics group we use a wide range of telescopes such as Hubble, JWST, TESS, Spitzer and the upcoming ESA Ariel mission to measure the atmospheres of exoplanets. Over the last decade we have been using the Hubble Space Telescope to perform large-scale surveys of exoplanet atmospheres from giant Jupiter sized worlds extremely close to their stars dubbed hot Jupiters, to Neptune sized worlds, and even rocky terrestrial worlds around small cool stars. To measure the atmosphere, we observe the transit of the exoplanet as it passes in front of its star, this causes a small dimming effect on the measured starlight which corresponds to the relative size of the planet. If the planet has an atmosphere surrounding it, some of the star's light will be filtered through the exoplanet atmosphere before reaching the telescope. Each atom and molecule have its own unique spectral fingerprint. If an atom or molecule is present in the exoplanet's atmosphere it will imprint its signature on the spectrum of the starlight which can be measured to determine the atmospheric composition. The Bristol group has world leading experts in data analysis techniques in time series spectroscopy and have worked across the UV - mid-IR to not only understand these atmospheres but the instruments we use to measure them.
Links to Observational Astrophysics and High-performance scientific computing and AI
Aerosols and clouds
We have discovered a huge diversity in the atmospheres of exoplanets from clear strong atomic and molecular signatures including water vapour, to scattering and muted or obscured features indicative of aerosols (clouds and hazes) high in the planet's atmosphere. Interestingly, due to the temperature of these worlds the clouds are not made of water, but instead things commonly found as rocks or minerals here on Earth such as enstatite (sand), or corundum (the basis of rubies and sapphires). We have developed a range of models to determine the spectral characteristics of different clouds, and are incorporating these into our 3D models to understand their role in feedback and even the effects of lightning. Our team also has strong ties to the Aerosols Group in the School of Chemistry working on experiments to produce clouds in the lab and measure their intrinsic properties.