Warwick Astrophysics Consolidated Grant 2014-2017

什么样的物体能引发宇宙中最剧烈的爆炸？什么样的星系拥有它们？被称为白色矮星的“死亡恒星”是如何爆炸的？其他恒星周围的行星是什么样的？有多少人？是什么过程震动和加热了我们的太阳表面，并驱动了冲击我们星球的风？这些问题，从我们最近的星星和我们银河系中的近邻到可观测宇宙的最远范围，都是沃里克天体物理学小组打算研究的领域。我们将使用地面和空间望远镜进行观测，理论发展和计算密集型数值建模。值得注意的是，今天我们对宇宙的其他部分了解得如此之多，尽管它仍然超出了我们的直接接触范围。这是因为我们对物理学的理解取得了巨大的进步，使我们能够推断出与地球上的温度，密度，运动和磁场截然不同的制度。我们的太阳系是我们可以直接到达的少数区域之一，但即使在这里，太阳的表面也太粗糙，无法直接测量。幸运的是，我们可以通过观察传播波来探测那里的情况，在传播波中，磁场与称为等离子体的热导电材料耦合，就像人们可以利用地震产生的地震波来探测地球内部的情况一样。在沃里克，我们将利用新型射电望远镜和数字建模来执行一项高速观测计划，以改进对我们最近的星星的活动表面的远程探测。太阳表面是太阳风的起点，偶尔的喷射事件会导致北方光，甚至影响电网。太阳风目前正在卫星上进行实地测量，我们将开发必要的工具，以了解太阳风周围复杂而动荡的波动。在更远的地方，在过去15年里，对其他太阳系的了解有了显著的发展，我们现在知道有800多颗行星围绕着其他恒星。沃里克是欧洲合作实施一项新调查的牵头研究所，在这项调查中，当行星穿过我们的视线到达星星时，恒星的光线会略有减少，从而调查行星的存在。这些是最有趣的行星，因为它们允许我们测量行星的质量和半径，因此我们可以找到它们的平均密度。密度取决于组成，因此我们有令人难以置信的前景探索其他恒星周围的行星是由什么组成的。再往前，我们的其他主题涉及爆炸性物体和事件，以及更遥远的宇宙。大多数恒星都以白色矮星的形式结束了它们的生命。白色矮星通常是高度稳定的，但众所周知，它们可以通过不受控制的核聚变爆炸，这可以在几秒钟内撕裂整个星星，摧毁白色矮星并产生我们所知道的光学最明亮的爆炸。我们不知道这是如何发生的，或者在什么系统中。在沃里克，我们将观察银河系中附近的白色矮星，以了解它们的结构以及它们如何从伴星获得质量，这被认为是爆炸的触发因素。所有爆炸中最明亮的是伽马射线暴（GRB），这是罕见的，但如此明亮，以至于在遥远的宇宙中可以看到超过100亿光年。值得注意的是，这些戏剧性的事件似乎有多种方式发生。我们的目标是了解伽玛暴的不同潜在原因是什么。伽玛射线暴来自星系中的恒星。这些星系及其环境的性质是我们的最后一个主题，它涉及星系在宇宙130亿年历史中的性质和类型如何演变。

What type of objects power the most violent explosions in the Universe? What kind of galaxies host them? How do the "dead stars" called white dwarfs explode? What are planets around other stars like? How many are there? What processes shake and heat the surface our Sun and drive the wind that buffets our planet? These questions, which range from our closest star and near neighbours in our Galaxy to the furthest reaches of the observable Universe are the areas that the Warwick astrophysics groups propose to investigate. We will do so with a mixture of observations using ground- and space-based telescopes, theoretical developments and computationally-intensive numerical modelling. It is quite remarkable that today we understand so much about the rest of the Universe even though it remains beyond our direct reach. This is because of enormous advances in our understanding of physics which allows us to extrapolate into regimes unimaginably different from those on Earth in terms of temperature, density, motion and magnetic field. Our Solar system is one of the few regions we can directly reach, but even here, the surface of the Sun is too harsh for any direct measurement. Luckily it is possible to probe conditions there through observations of propagating waves in which magnetic fields are coupled to hot, electrically-conducting material called plasma, much as one can probe conditions within the Earth using seismic waves generated by earthquakes. At Warwick we will carry out a program of high-speed observations using novel radio telescopes and numerical modelling to improve these remote probes of the active surface of our closest star. The surface of the Sun is the starting point for the solar wind, and occasional ejection events which cause the Northern Lights and even affect electrical power grids. The solar wind is now being measured in situ from satellites, and we will develop the tools needed to understand the complex and turbulent fluctuations that characterise it. Moving further afield, there has been a remarkable blossoming of knowledge of other solar systems in the past 15 years, and we now know of more than 800 planets around other stars. Warwick is the lead institute in a European collaboration to implement a new survey in which stars are surveyed for the presence of planets through the small decrease in light that occurs as the planets cross our line of sigh to the star. These are the most interesting planets to find because they allow us to measure both the mass and radius of the planet, and hence we can find their mean density. The density depends upon composition and thus we have the incredible prospect of probing what planets around other stars are made of. Further out still our other themes concern explosive objects and events, and the more distant Universe. Most stars end their lives in the form of objects called white dwarfs. White dwarfs are usually highly stable, but it is known that they can be made to explode through uncontrolled nuclear fusion which can tear through the entire star within a few seconds, destroying the white dwarf and producing one the optically brightest explosion that we know of. What we don't know is how this happens, or in what systems. At Warwick we will look at nearby white dwarfs in our Galaxy to understand their structure and how they can gain mass from companion stars, which is thought to be the trigger for the explosions. The brightest explosions of all are the Gamma Ray Bursts (GRBs), which are rare, but so bright that they can be seen more than 10 billion light-years away in the distant Universe. Remarkably for such dramatic events, there seem to be multiple ways for them to occur. Our aim is to understand what the different underlying causes are for GRBs. GRBs come from stars residing in galaxies. The nature of those galaxies and their environment is our final theme which addresses how galaxies evolve in nature and type over the 13 billion year history of the Universe.