A Programme of Astrophysical Theory and Observations at Leeds

这个研究项目主要研究恒星和行星是如何从尘埃和气体云中形成的。恒星是由占据星际空间的气体云和混合在其中的小尘埃颗粒形成的。这些云是高度丝状的，磁场也弥漫在太空中，很可能在塑造它们的过程中发挥了作用，并控制了它们在重力作用下的坍缩，从而形成恒星。我们将进行计算机模拟，以确定这些分子云是如何形成的，以及是什么形成了它们复杂的结构。事实证明，比太阳质量大得多的恒星的形成问题要大得多，因为它们数量稀少，距离遥远，而且会产生大量的辐射，这些辐射会把物质吹走，而不是让它们落进去。随着流入的物质越来越靠近恒星，我们预计它会以一个围绕恒星运行的薄圆盘的形式完成它的旅程。ALMA望远镜对分子发射的详细测绘将揭示这些圆盘是稳定的，还是会分裂成双星系统。这些圆盘的内部区域温度更高，将使用红外干涉测量和光谱学技术进行研究。它显示的空间信息比哈勃太空望远镜要好10到100倍。这样的分辨率还将揭示大质量的原恒星双星系统是否已经形成。与此同时，物质通过圆盘旋转到恒星上，其中一些沿着旋转轴高速喷射，很可能是由磁场驱动的。为了进一步跟踪这些喷射，我们将使用英国高度敏感的无线电天线网络，e-MERLIN，来绘制它们的发射图。大多数恒星都是在星团中形成的，但这种系统的形成和演化方式却备受争议。来自欧空局盖亚卫星的新信息测量了恒星的精确距离和运动，将与分子气体云的其他数据一起用于与模拟进行比较。将开发新的统计技术来进行这种多维比较。随着大质量星团最终开始清除它们产生的物质，它们的辐射、风和超新星爆炸时的消亡的综合影响对周围的分子云产生了巨大的影响。计算机模拟将用于解决这个问题，以研究这些来自星团的反馈过程如何影响其巨大分子云宿主和更广泛的星系的演化。围绕恒星（如太阳）形成的圆盘是行星形成的地方，它们是由尘埃颗粒合并而成的。这只被认为发生在较安静的区域，那里由于磁场的湍流不那么强。带电尘埃粒子相对于气体的运动在形成过程中很重要，这将通过复杂的计算机模拟来检验。研究人员将对这些圆盘的性质进行调查，以确定为什么这些恒星所在的行星系统与那些类似太阳的恒星周围的行星系统不同。ALMA望远镜将对行星形成盘的化学组成进行高分辨率研究，以找出行星形成的初始条件，以及到目前为止，化学复杂性的道路已经走了多远。一项实验室研究将测量关键的化学反应速率，以发现在通往生物系统的途径上一些最有趣的分子是如何形成的。这些将被纳入圆盘的化学模型，以解决生命起源的问题。在恒星生命接近尾声时，开始行星形成过程的尘埃颗粒本身就产生了。我们将进行详细的化学计算，以弄清楚这些硅酸盐矿物是如何从巨大恒星丰富、凉爽的大气中的气体元素中形成的。

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.