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.
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.
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
Eager-Nash J
(2023)
3D Climate Simulations of the Archean Find That Methane has a Strong Cooling Effect at High Concentrations
in Journal of Geophysical Research: Atmospheres
Ridgway R
(2023)
3D modelling of the impact of stellar activity on tidally locked terrestrial exoplanets: atmospheric composition and habitability
in Monthly Notices of the Royal Astronomical Society
Mak M
(2023)
3D Simulations of the Archean Earth Including Photochemical Haze Profiles
in Journal of Geophysical Research: Atmospheres
Mak M
(2024)
3D simulations of TRAPPIST-1e with varying CO2, CH4, and haze profiles
in Monthly Notices of the Royal Astronomical Society
Baraffe I
(2018)
A closer look at the transition between fully convective and partly radiative low-mass stars
in Astronomy & Astrophysics
Mikal-Evans T
(2023)
A JWST NIRSpec Phase Curve for WASP-121b: Dayside Emission Strongest Eastward of the Substellar Point and Nightside Conditions Conducive to Cloud Formation
in The Astrophysical Journal Letters
McCulloch D
(2022)
A modern-day Mars climate in the Met Office Unified Model: dry simulations
McCulloch D
(2023)
A modern-day Mars climate in the Met Office Unified Model: dry simulations
in Geoscientific Model Development
McCulloch D
(2023)
A modern-day Mars climate in the Met Office Unified Model: dry simulations
Phillips M
(2020)
A new set of atmosphere and evolution models for cool T-Y brown dwarfs and giant exoplanets
in Astronomy & Astrophysics
Baraffe I
(2023)
A study of convective core overshooting as a function of stellar mass based on two-dimensional hydrodynamical simulations
in Monthly Notices of the Royal Astronomical Society
Popov M
(2019)
A well-balanced scheme for the simulation tool-kit A-MaZe: implementation, tests, and first applications to stellar structure
in Astronomy & Astrophysics
Debras F
(2019)
Acceleration of superrotation in simulated hot Jupiter atmospheres
in Astronomy & Astrophysics
Ballester G
(2019)
An emission spectrum for WASP-121b measured across the 0.8-1.1 µm wavelength range using the Hubble Space Telescope
in Monthly Notices of the Royal Astronomical Society
Sergeev D
(2020)
Atmospheric Convection Plays a Key Role in the Climate of Tidally Locked Terrestrial Exoplanets: Insights from High-resolution Simulations
in The Astrophysical Journal
Sergeev D
(2022)
Bistability of the atmospheric circulation on TRAPPIST-1e
Sergeev D
(2022)
Bistability of the Atmospheric Circulation on TRAPPIST-1e
in The Planetary Science Journal
Christie D
(2022)
CAMEMBERT: A Mini-Neptunes General Circulation Model Intercomparison, Protocol Version 1.0.A CUISINES Model Intercomparison Project
in The Planetary Science Journal
Description | We explored the impact of the latest equation of state for dense hydrogen-helium mixtures on the structure and evolution of very low-mass stars and brown dwarfs. Confronting these new models with several observationally determined brown dwarf dynamical masses, we show that this does indeed improve the agreement between evolutionary models and observations and resolves at least part of a well-known observed discrepancy for massive, rather old brown dwarfs. |
Exploitation Route | This work provides models that are used by a wide community working on low mass stars and brown dwarfs and for the interpretation of observations obtained with state-of-the-art telescopes (e.g JWST, Euclid). |
Sectors | Other |
Description | COBOM |
Amount | € 2,500,000 (EUR) |
Funding ID | COBOM |
Organisation | European Research Council (ERC) |
Sector | Public |
Country | Belgium |
Start | 08/2018 |
End | 08/2023 |
Title | Simulations from "Using Molecular Gas Observations to Guide Initial Conditions for Star Cluster Simulations" |
Description | This dataset contains the simulation results from the article "Using Molecular Gas Observations to Guide Initial Conditions for Star Cluster Simulations" (submitted to MNRAS). The data is grouped by simulation and by particle type (gas, sinks and stars). Gas is uploaded with one snapshot per 0.05 Myr, sinks and stars with one snapshot per 0.01 Myr. The data is stored in AMUSE data format, which uses hdf5. |
Type Of Material | Database/Collection of data |
Year Produced | 2022 |
Provided To Others? | Yes |
URL | https://zenodo.org/record/7015719 |
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 |