A Programme of Astrophysical Theory and Observations at Leeds

点击翻译按钮获取中文摘要

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.