A Programme of Astrophysical Theory and Observations at Leeds

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

Abstract

This research programme principally addresses how stars and planets form from clouds of dust and gas.

Stars form from the clouds of gas that occupy interstellar space and the small dust grains mixed in them. The clouds are highly filamentary and magnetic fields, that also pervade space, are likely to have had a role in shaping them, and controlling their collapse under gravity to form stars. We will conduct computer simulations to ascertain how these molecular clouds are formed and what shapes their complex structure.

The formation of stars much more massive than our Sun has proved to be much more problematic as they are rare and distant and produce prodigious amounts of radiation that blow material away rather than let it fall in. As the infalling material gets close in to the star we expect it to complete its journey in a thin disc orbiting the star. Detailed mapping of the molecular emission with the ALMA telescope will reveal whether these discs are stable or whether they will fragment to form binary systems. The inner regions of these discs are hotter and will be studied using the techniques of infrared interferometry and spectroscopy. This reveals spatial information at levels 10 to 100 times better than the Hubble Space Telescope. Such resolution will also reveal if massive proto-stellar binary systems have already formed. At the same time that material is spiralling onto a star via a disc, some of it is being ejected at high speeds along the rotation axis, most likely driven by magnetic fields. To follow these jets further out we will use the highly sensitive network of radio dishes in the UK, e-MERLIN, to map their emission.

Most stars form in clusters, but the way in which such systems form and evolve is hotly debated. New information from ESA's Gaia satellite that measures accurate distances and motions of stars will be used alongside other data on the molecular gas clouds to compare with simulations. Novel statistical techniques will be developed to undertake this multi-dimensional comparison. As massive star clusters finally begin to clear away the material from which they were born the combined effect of their radiation, winds and demise as supernovae explosions has a dramatic effect on the surrounding molecular clouds. Computer simulations will be used to tackle this problem to investigate how these feedback processes from star clusters affect the evolution of their giant molecular cloud hosts and the wider galaxy.

The discs that surround stars like the Sun as they are forming are the sites where planets form, built up from the coalescence of dust grains. This is only thought to occur in the quieter regions of the disc where turbulence due to the magnetic fields is less strong. How the charged dust particles move relative to the gas is important in the formation process and that will be examined with sophisticated computer simulations. A survey of the properties of these discs around stars slightly more massive than our Sun will be carried out to ascertain why the planetary systems that these stars host appear different to those seen around more solar-like stars. A high resolution study of the chemical make up of planet forming discs will be carried out with the ALMA telescope to find out the initial conditions for planet formation and how far down the road of chemical complexity has already been traveled by this stage. A laboratory study will measure key chemical reaction rates needed to find out how some of the most interesting molecules on the pathway to biological systems are formed. These will be incorporated in to chemical models of the discs to address questions on the origins of life.

Near the end of the lives of stars, the very dust grains that begin the planet formation process are themselves produced. We will perform detailed chemical calculations to work out how these silicate minerals are built up from the gaseous elements in the rich, cool, atmospheres of giant stars.

Planned Impact

The proposal concerns work that will have impact on various industries that directly benefit from the spin-offs of our research methodologies, expertise and in-house computer codes. For example, the research exploiting our state-of-the-art multi-fluid models is extremely relevant in a surprisingly wide range of applications. At present our codes are being applied to the study of the use of jets of carbon dioxide in advanced manufacturing in the nuclear industry. We are also working on magnetic confinement of plasmas for nuclear fusion. In a new development we are also exploring the application of fluid dynamical codes in the medical arena with an application in liver surgery. The ongoing development and improvement of computational methods and codes will ensure the continuation of existing, and the forging of new, fruitful industrial collaborations, which will ultimately aid the UK's economic competitiveness. Our astronomical expertise is also put to use in assisting planning decisions surrounding light pollution around wind farm developments.

Leeds has led the way in the novel use of Overseas Development Assistance funding to provide training in radio astronomy in low- and middle-income countries. In the run up to Africa hosting the world's biggest radio telescope the DARA project has provided a basic training for over 160 young people in seven different African countries. The advanced research and technical skills will help to upskill the population and generate economic development in the long term. The training involves our industrial and entrepreneurial partners from Goonhilly Earth Station Ltd. who run a successful satellite communications business from the former BT site in Cornwall. Leeds has also led the effort to convert the old 30 m class dishes at Goonhilly in to radio telescopes in a unique public-private partnership. This collaboration has led to several opportunities to showcase astronomy to the public in unique ways such as Tim Peake's Q&A with local primary school children and art installations incorporating radio astronomy data at Goonhilly.

The subjects of stellar birth and planet formation, including their astrobiological relevance, appeal to the imagination and the Leeds astrophysicists are strongly committed to communicating both their own and general astronomical results to a wide audience. They do this via public appearances and the organisation of events, and through the mass media by, for example, issuing press releases and making media appearances. We make use of our full time outreach officer to coordinate activities locally, regionally and nationally and have a good working relationship with our press office. Our outreach is built around a set portfolio of events, which continue to be developed and improved. We particularly focus events on school children and young people. Our donation of telescopes to local astronomical societies has enhanced their outreach in joint partnerships with us.

Publications

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