The formation, structure, and evolution of molecular clouds, stars, and planets

Lead Research Organisation: University of Exeter
Department Name: Physics

Abstract

Our research is focussed on improving our understanding of how stars and planets form, and the physical processes that occur both deep in the interior and in the outer layers of stars and planets. We intend to achieve this goal using a combination of computer modelling and observations.

Stars form from molecular clouds, and we will examine the structure of this turbulent gas, since this has a strong influence on how they collapse under gravity. We will look at a nearby ring of star forming regions, called the Gould Belt, using an extensive survey taken at sub-millimetre wavelengths, testing our models of how stars form and looking for evidence of the earliest stages of protostars. We will also use computer models to investigate how the Gould Belt formed, since it may be that supernova explosions are the key to creating its ring-like structure.

The collapse of a molecular cloud results in a cluster of stars with a variety of masses. Most stars are less massive than the Sun, and some objects have such low masses that they do not fuse hydrogen in their cores. These objects are known as brown dwarfs and they are hot when they are formed but cool over time. By examining the statistical properties of clusters of stars we will be able to measure the initial distribution of stellar masses, and this will enable us to test how brown dwarfs cool. Although most stars are less massive than the Sun, some can be over twenty times as massive and are extremely bright. The formation of these giant stars is fundamentally a competition between gravity and the outward pressure exerted by the starlight. We will use computer simulations to investigate how such stars form, and compare our simulations to observations from ground- and space-based telescopes.

Newly forming stars are surrounded by dense discs of dust and gas. We will use interferometry, an observational method that combines light collected by several telescopes together, to measure the structure of these discs. Sophisticated computer models will be used to investigate the protostar-disc interaction. It is known that planets form in such discs, and we will use sophisticated computer models to simulate how a proto-planet coalesces out of the dust and gas. 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. We will use adaptive optics (a high-resolution observational techniques that corrects for the distorting effect of the Earth's atmosphere) to identify newly formed planets around young stars and examine the gravitational effect of these exoplanets on the debris discs.

We will investigate the atmospheres of so-called Hot Jupiters - exoplanets that are strongly irradiated by their host stars. This research uses 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 use computer models to investigate the interior structure of Jupiter and Saturn, planets whose shape is distorted by their rapid rotation. We will compare our results to observations made by the Juno and Cassini space probes.

The solar wind is a continuous stream of plasma flowing away from the Sun. The Sun and large disturbances in the solar wind affect our climate and causes, for instance, communication drop-outs, power outages and radiation exposure on transatlantic flights. We will investigate the physics of the Sun using a combination of theory and observations. We will examine properties of the solar magnetic field, at the Sun and near Earth in the solar wind, that indicate ways in which it can twist and kink. Build up of twisting can lead to enhanced solar activity, which has implications for the prediction of space weather. We will also use computer models to look at how turbulent motions in the Sun are produced as the ionised gas interacts with the Sun's magnetic field.

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 space weather: Our adaptations to the UK Met Office software is resulting in direct improvements to the model they will use for future climate and model prediction. In order to model the extreme climates found amongst the family of discovered exoplanets, the model is being adapted to become much more robust and flexible, which has fed back into the Met Office terrestrial work. The Astrophysics Group has two seconded Met Office staff; Applied Mathematics has 3 Professors jointly funded with the Met Office and several PhD students with Met Office funding. Within CGAFD, the Solar-Terrestrial Plasmas and Space-Weather group is growing to build bridges with the Met Office space weather group, responsible for the space weather risk in the UK. This knowledge exchange will have many benefits to both partners.

The high performance computing community: Our group is well connected to this community via various networks. The University of Exeter supercomputer upgrade is driven by astrophysical fluid applications and supported by this group will be available to Exeter researchers across STEM subjects. The system manager (a member of Astrophysics) will share his learning and experience of HPC systems, including DiRAC, with other experts across the UK via the HPC Special Interest Group. The SPH numerical technique originated and is widely used in astrophysics, but is also used in engineering, computer gaming, movies, advertising, and other industries. Prof. Bate will continue to represent the University of Exeter in the SPH European Research Interest Community (SPHERIC). SPHERIC was founded in 2005 to foster the spread of this simulation method and serve as a platform for transfer of knowledge between research groups, and from science to industry, within Europe and worldwide.

Education, schools and teachers: The Exeter Astrophysics and CGAFD groups are serious about widening participation and raising expectations in the rural Southwest. Specifically, this period will see the opening of the Exeter Mathematics School, a University-supported sixth form free school for talented mathematicians in the southwest: Mitchell Berger, Joanne Mason and Claire Foullon are among staff developing workshops inspired by their research programmes. The beauty and wonder of astrophysics often inspires young people to take an interest in science. Exeter Astrophysics group are increasingly recognised as providing STEM educational resources, support and training in the southwest by various partners (see http://www.astro.ex.ac.uk/outreach/archive for a list of our outreach work). Recently we have begun a new partnership with the Ogden trust who promote physics through teacher networks and small grants.

The general public: Our research reaches a wide audience through the media and our website: for example, Matthew Bate's animations of star- and planet formation are used worldwide as an outreach resource, and Nathan Mayne and David Sing's collaboration with the Met Office on modelling exoplanet atmospheres was the subject of a feature on BBC Stargazing Live! Jan 2014. Impressed by the BBC's visualisations of exoplanet atmospheres on the surface of a sphere, we are currently preparing an application, in collaboration with Puffersphere UK to make the outputs from several of our theoretical and observational databases available on their sophisticated 3D visualisation equipment. The main goal or milestone is to make astronomical data available in visually exciting formats for public outreach e.g. in museums.

Publications

10 25 50
publication icon
Acreman D (2015) Modelling multiwavelength observational characteristics of bow shocks from runaway early-type stars in Monthly Notices of the Royal Astronomical Society

publication icon
Ali A (2019) Massive star feedback in clusters: variation of the FUV interstellar radiation field in time and space in Monthly Notices of the Royal Astronomical Society

publication icon
Cleeves LI (2016) EXPLORING THE ORIGINS OF DEUTERIUM ENRICHMENTS IN SOLAR NEBULAR ORGANICS. in The Astrophysical journal

 
Description We have produced the first simulations of the formation of a massive star that include a detailed treatment of the radiation feedback. We have extended these calculations to cluster scales. We have published the first results of a high-resolution survey of structured discs around young stars, including the spectacular object HD34700.

Our survey for exoplanets from the W.M. Keck Observatory remains as one of the largest exoplanet direct imaging surveys to date. Among our key findings are the discovery around a nearby young star of an edge-on circumstellar debris disc, a belt of kilometre-sized planetesimals that are colliding and grinding down into small dust particles. This undiscovered system is an analog to a very young version of our own solar system, and shows a dramatic asymmetry, strongly suggesting the presence of one or more planetary bodies in the system that are driving the morphology of the disc. This system will be ideal for future follow-up observations of the disc, or to search for evidence of the planetary perturber in the system
Exploitation Route Colleagues are using our massive star simulations for comparison with ALMA data of massive young stellar objects. Developments to the TORUS code are helping several groups in the UK and US in simulating circumstellar discs. The TORUS code has been used to develop a model for the efficacy of photodynamic therapy treatments for non-melanoma skin cancer.
Sectors Healthcare

 
Description Applying an astrophysics modelling tool to improve the diagnosis and treatment of cancers
Amount £295,595 (GBP)
Funding ID ST/R004986/1 
Organisation Science and Technologies Facilities Council (STFC) 
Sector Academic/University
Country United Kingdom
Start 07/2018 
End 06/2021