Warwick Astronomy and Astrophysics Rolling Grant 2011-2016

宇宙是不断变化的。在数百万年的时间尺度上，恒星诞生、生存和死亡，在数亿年的时间里，整个星系形成了。在某些阶段，恒星的生命可以大大加快，我们可以看到几天、几小时甚至几秒钟内发生的变化。在过去的几十年里，计算机技术取得了令人难以置信的进步，这使得天文学家能够大量地追踪这类事件。一个极端是遥远的“Ia型”超新星，用来探测现代物理学中最深奥的奥秘，暗能量现在被认为是推动宇宙膨胀速度不断加快的原因，而另一个极端是在距离地球几光年的恒星周围发现了数百个其他世界。其中一些变化最快的天体是恒星生命结束时留下的致密残留物（白矮星、中子星和黑洞）。这样的恒星对以每秒1000个轨道的速度运行，会辐射出空间几何结构的扰动，称为引力波。探测这种涟漪的实验正在顺利进行，并为爱因斯坦的伟大杰作——广义相对论——提供了第一次直接测试。Ia型超新星很亮，但很罕见，所以尽管我们可以在遥远的宇宙中看到它们，但它们很少出现在足够近的地方，无法进行详细研究；我们已经有400多年没有在银河系中看到过了。因此，尽管我们知道它们是由爆炸的白矮星引起的，但我们并不确切地知道是什么样的系统产生了它们。然而，在附近的宇宙中一定有许多潜在的超新星。我们将开展一个项目来了解这些潜在的祖先，目的是了解它们的数量和进化。我们将结合覆盖大面积天空的调查发现，以及对单个天体的详细研究，以了解它们的过去和未来演变。这些是测试和发展双星演化模型所需的数据，从中我们可以预测宇宙历史上Ia型超新星的演化程度，这对于它们作为暗能量探测器的使用至关重要。同样的模型也需要用于预测引力波源的数量和性质，这对引力波探测器本身的发展至关重要。最极端的可变源是伽马射线暴，这种惊人的明亮爆炸将我们带回到年轻的宇宙。伽马射线暴是一种恒星爆炸，它能让我们精确定位星系的早期生命。该小组最近对伽马射线暴的研究发现了迄今为止最遥远的天体。我们将通过大型地面和太空望远镜（如哈勃太空望远镜和欧洲南方天文台的超大望远镜）进行一系列观测，以探索导致年轻宇宙中第一批恒星形成的条件。我们对伽玛射线暴的追踪工作可能会缩小进行引力波搜索所需的模型范围，从而有助于寻找引力波。我们现在知道的其他恒星周围的行星（超过400颗）比我们太阳系内的行星多得多。这些其他的世界揭示了一个意想不到的充满活力的过去，其中包括行星与行星之间的相互作用，将一些行星抛向它们的恒星，而另一些则完全远离它们。所有对这类系统的调查都倾向于选择大质量的行星。我们将开发一种新的照相机，对较小的行星很敏感，可以与太阳系中的海王星相媲美。我们将使用与了解双星系统相同的技术，通过观察它们的大气层来探测太阳系外的行星。我们将使用哈勃太空望远镜来测量白矮星周围的太阳系外行星物质的元素丰度，并利用双星系统中白矮星的时钟般的精度来探测行星伴星。

The Universe is constantly changing. On timescales of millions of years, stars are born, live and die, and in hundreds of millions of years, entire galaxies come into being. At some stages, the lives of stars can be dramatically sped up and we can see changes happening in days, hours or even seconds. The incredible advances in computer technology of the last decades is now allowing astronomers to track such events in large numbers. At one extreme are the distant 'Type Ia' supernovae used to probe perhaps the deepest mystery of modern physics, the dark energy now thought to be driving an increasing rate of Universal expansion, while at the other are surveys that have found hundreds of other worlds around stars a few light-years from Earth. Some of the most rapidly variable objects of all are the dense remnants left at the end of stars' lives (white dwarfs, neutron stars and black-holes). Pairs of such stars orbiting at up to 1000 orbits per second radiate perturbations of the geometry of space called gravitational waves. Experiments are well underway to detect such ripples and provide the first direct tests of Einstein's great tour-de-force, the theory of General Relativity. Type Ia supernovae are bright but rare so although we can see them in the distant Universe, they only very rarely occur near enough to study in detail; we have not seen one in our own Galaxy for over 400 years. Thus, although we know that they are caused by exploding white dwarfs, we don't know precisely what sort of systems produce them. Yet, there must be many potential supernovae in the nearby Universe. We will pursue a program to understand such potential progenitors with the aim of understanding their numbers and evolution. We will employ a combination of discovery from surveys covering large areas of sky followed by detailed study of individual objects in order to understand both their past and future evolution. These are the data needed to test and develop the models of binary star evolution from which we can predict the extent of the evolution of Type Ia supernovae during the history of the Universe, crucial for their use as probes of dark energy. The same models are required to predict the number and properties of gravitational wave sources, essential for the development of the gravitational wave detectors themselves. The most extreme variable sources of all are gamma-ray bursts, staggeringly bright explosions which take us back to the young Universe. Gamma-ray bursts are stellar explosions which allow us to pinpoint galaxies early in their lives. Recent work on gamma-ray bursts by the group has been led to the discovery of the most distant objects ever seen. We will pursue these with an array of observations from large ground- and space-based telescopes such as the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope to probe the conditions that lead to the formation of the first stars in the young Universe. Our work in following up gamma-ray bursts may help the search for gravitational waves by narrowing the range of models needed to perform such searches. We now know many more planets (over 400) around other stars than exist within our own solar system. These other worlds have revealed an unexpectedly dynamic past involving planet-planet interactions flinging some planets towards their stars and others out of their reach altogether. All surveys for such systems tend to favour large, massive planets. We will develop a new camera sensitive to smaller planets, comparable to Neptune in the solar system. We will use the same techniques needed to understand binary systems to probe extra-solar planets by looking through their atmospheres to their host stars. We will use the Hubble Space Telescope to measure element abundances of extrasolar planetary material around white dwarfs and use the clock-like precision of white dwarfs in binary systems to detect planetary companions.