A comprehensive study of stars, disks and exoplanets

Lead Research Organisation: University of Exeter
Department Name: Physics and Astronomy

Abstract

Our research is focussed on improving our understanding of how stars, disks and planets form, and of the physical processes that occur deep in the interior of stars and in the atmosphere of exoplanets. We intend to achieve this goal using a combination of state-of-the art computer modelling and observations obtained from cutting-edge facilities.

Stars form from molecular clouds which collapse, resulting in the formation of objects with a wide range of masses. High mass star formation may impact low mass star formation within the same cluster and the physical processes that are the most relevant during the formation of low mass stars and high mass stars, respectively, can be different. Forming the most massive stars is clearly a challenge because of the enormous radiation field produced by massive protostars. Many stars form in binary systems and newly forming stars are surrounded by dense discs of dust and gas. How binaries and how proto-planetary discs, which are the natural sites of planet formation, form precisely remain major unsolved problems. Once the star and planet system has fully formed, the only dust that is left is generated by asteroids colliding together, a so-called debris disc. Combining different observational methods at various wavelengths and sophisticated computer modelling that include complex physics, we will study in depth all steps, starting from the properties of molecular clouds, that lead to the formation of stars, discs and planets.

After stars form, their further evolution is characterised by complex physical processes, such as turbulent convection and magnetism, that shape their internal structure and their observational properties. Exquisite observational data are now available, with for example asteroseismology providing important constrainsts on the internal structure of stars. We will use sophisticated numerical models to improve our understanding of stellar interiors and to explain various observational puzzles, such as the inflation of young stars or the large size of the convective core of hydrogen burning stars.

We will also develop original strategies to optimise the detection of exoplanets by linking their presence to debris disks and to provide a comprehensive sample that enables exploration of exoplanet atmospheres over a wide range of orbital parameters. With the large number of exoplanets now available, a new era of wide-scale comparative planetology has now begun. We will carry out a comprehensive survey of highly-irradiated gas-giant exoplanet atmospheres with the Hubble Space Telescope and investigate major outstanding issues such as the atmospheric chemistry of cloud/haze formation. To describe the physical properties of exoplanet atmospheres, we use the Met Office's computer model for the Earth's climate, which has been specially adapted to deal with the different physical process that occur in exoplanet atmospheres. We will also develop new tools to understand the detailed atmospheric chemistry of irradiated exoplanets and which will be optimised to interpret observations. We will also analyse the climates of recently discovered nearby candidate habitable exoplanets (e.g. Proxima Centauri b) that may be characterised by observations from near future platforms, in order to explore the potentiality of these small planets to host some form of life.

Planned Impact

We collaborate with a number of partners to apply our research work in a wider context. We are also committed to communicating our results, engaging schools and the general public in an increasing number of ways. Over the period of this grant, we plan to deliver impact with the following beneficiaries:

Climate modelling and exoplanets: Over the past three years our adaptations to the UK Met Office software have all, once published, been deposited back into the shared repository and therefore form part of the base model used for Earth climate and weather prediction. The direct developments required for our scientific objectives have resulted in a more flexible and faster model. Additionally, this work has provided a pathway to guide Met Office developments aimed at making the software applicable to a wider range of conditions. We have also begun a series of meetings, termed the "Idealised UM Workshops" aimed at widening use of the software both in terms of users and the problems approached, as well as performing intercomparisons.

The high performance computing community: Our group is well connected to this community via various networks (e.g. the STFC's DiRAC, and the HPC Special Interest Group). Within the University of Exeter, astrophysical fluid applications are driving a supercomputer upgrade which will make HPC available to Exeter researchers across STEM subjects, supported by Astrophysics expertise. Within Europe, Prof Bate will continue to represent the University of Exeter in the SPH European Research Interest Community (SPHERIC) (http://wiki.manchester.ac.uk/spheric/), founded in 2005 to foster the spread of a technique which is used in astrophysics but also used in engineering, computer gaming, movies, advertising, and other industries within Europe and worldwide. SPHERIC serves as a platform for transfer of knowledge between research groups, and from science to industry. We also provide to our undergraduate/postgraduate students and postdocs broad training and skills in HPC, that are valuable to go and work in industry and non academic institutions (e.g recruitments of our PhD/postdocs at the Met Office and SAP).

Radiative transfer and skin cancer: Harries, in collaboration with Drs Alison Curnow and Clare Thorn from the University's Medical School is adapting the radiative transfer code TORUS to model light scattering through human tissue. This modification was performed in collaboration with the Centre for Biomedical Modelling and Analysis and it is now being used by a 4-year PhD student to create a 'virtual laboratory' for studying photodynamic therapy. TORUS is also used to model deep Raman scattering in breast tissue (in collaboration with Exeter's biomedical physics group). Deep Raman spectroscopy provides a route to swift, non-invasive diagnosis of breast cancer, and numerical modelling is key to assessing the sensitivity and specificity of the technique.

Education, schools and teachers: The Exeter Astrophysics group is committed to widening participation and raising expectations in the rural Southwest. We have a tradition of incorporating our latest research results in our educational activities and will continue with the current projects. We deliver our outreach through a well-established network of contacts and a calendar of annual events, as well as responding to one-off requests. Since 2015, our schools outreach has expanded enormously with the support of our full-time Ogden Science Outreach Officer, Alice Mills. The Ogden trust is a charity that promotes physics through teacher networks and small grants. Alice (PhD in astrophysics) delivers astrophysics-themed schools events, campus visits, and workshops to Ogden schools partners and University widening participation schools, incorporating our research results into her activities. Staff are involved in leading events and providing talks and postdocs and PhD students are trained to provide outreach event support.

Publications

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Debras F (2019) Acceleration of superrotation in simulated hot Jupiter atmospheres in Astronomy & Astrophysics

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Yates J (2020) Ozone chemistry on tidally locked M dwarf planets in Monthly Notices of the Royal Astronomical Society

 
Description COBOM
Amount € 2,500,000 (EUR)
Funding ID COBOM 
Organisation European Research Council (ERC) 
Sector Public
Country Belgium
Start 09/2018 
End 08/2023
 
Description Collaboration with CEA-Saclay, France 
Organisation University of Paris-Saclay
Country France 
Sector Academic/University 
PI Contribution Collaboration with shared PhD student.
Collaborator Contribution Contribution to the development of an atmosphere numerical tool for brown dwarfs and exoplanets
Impact Publications: Sainsbury et al. 2020; Tremblin et al. 2020;
Start Year 2018
 
Description Collaboration with the UK Met Office 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Academic/University 
PI Contribution extension of the UM numerical tool of the Met Office to the study of exoplanets
Collaborator Contribution Co-authorship and use of the UM numerical tool of the Met Office
Impact see publication lists (Mayne et al. 2019; Drummond et al 2019; Lines et al. 2019; Debras et al. 2020; Yates et al. 2020)
Start Year 2018
 
Description Scientific collaboration 
Organisation École normale supérieure de Lyon (ENS Lyon)
Country France 
Sector Academic/University 
PI Contribution shared publications and PhD student co-supervision
Collaborator Contribution shared publications and PhD student co-supervision
Impact Pubications: - Baraffe & Chabrier 2018 - Popov et al. 2020 - Debras et al. 2020 - Tremblin et al 2020 - Saisnbury-Martinez et al. 2020
Start Year 2018