Research in planetary formation, astrophysics, and cosmology at Bristol

这个计划是为了在布里斯托大学物理和地球科学学院研究行星科学、天体物理学和宇宙学中的几个重要问题。第一个项目是研究月球是如何形成的。目前最好的观点是，月球是由一颗巨大的原行星和年轻的地球之间的巨大撞击产生的。问题是，这导致对月球化学组成的预测与我们测量的不同。存在替代的撞击情景，在它们之间进行选择的关键是对月球上元素（以及这些元素的不同同位素）的混合进行良好的测量。该项目将对月球岩石进行比以往更精确的测量，并期望能够选择一种模型。第二个项目涉及使用卡西尼号航天器的新数据来研究土星的巨大卫星泰坦的大气。该项目将确定土卫六的气候系统如何运作，以及大气层如何在土卫六7.5地球年的两个季节中重新分配太阳能。土卫六是太阳系中仅有的四颗拥有大气层的类地行星之一，它为我们提供了在极端条件下行星大气层如何运作的独特见解。最后一个行星科学项目是研究行星如何从年轻恒星周围的气体/尘埃盘中的小颗粒形成。我们现在知道行星在恒星周围很常见，但我们仍然不确定行星是如何形成的，甚至不确定在这些圆盘中寻找行星的最佳方法。在这个项目中进行的高性能计算机计算的目的是预测行星在我们所知存在的盘中的位置。过去几年中，许多宇宙学都是基于对星系团的调查，第四个项目是调查由XMM-牛顿X射线天文卫星进行的最大单次调查所返回的星系团样本。这次调查发现了数千个X射线源，其中大约1000个是星系团，它们从包含的热气中发射X射线。这种热气排放可以用来估计星系团的质量，而星系团质量的分布随着宇宙时间的变化而变化，是对我们所居住的宇宙类型的一个很好的测试。第五个项目研究了理解星系团大气层的问题之一-为什么来自它们大气层的辐射不会导致它们冷却下来，并停止成为X射线源。答案似乎是，星系团中的气体是通过从星系团中一些星系中心黑洞附近区域喷射出非常热、快速的气体而被重新加热的。这个项目的目的是了解加热的过程，快速气体喷射的物理学，以及从黑洞附近出来的气体是否可以使星系团气体具有磁性。当星系团随着时间变化时，由于气体冷却和加热，以及宇宙的大小变化，其中的星系也会发生变化。第六个项目是观察星系团内的星系如何随着星系团的变化而变化，以及星系团如何影响星系，星系如何影响星系团。现在可以看到非常年轻的星系团，当时宇宙只有现在年龄的20%左右，通过跟踪从那时到现在的星系和星系团的变化，可以了解发生了什么。最后一个项目涉及维护和改进用于天文物体目录的代码。这些代码在处理现代天文数据时是必不可少的，并且在世界范围内使用，因此对许多天文学家来说非常重要。有些人甚至找到了进入公共产品的方式，如微软全球望远镜。

This proposal is for a grant to investigate several important questions in planetary science, astrophysics, and cosmology in the Schools of Physics and Earth Sciences in the University of Bristol.The first project is an investigation of how the Moon formed. The best current idea is that the Moon was created by a giant impact between a massive protoplanet and the young Earth. The problem is that this leads to predictions for the chemical makeup of the Moon that differ from what we measure. Alternative impact scenarios exist, and the key to choosing between them is good measurements of the mix of elements (and different isotopes of those elements) on the Moon. This project will make a far more precise set of measurements of moon rocks than has been possible in the past, with the expectation of being able to choose one model over another.The second project involves using new data from the Cassini spacecraft to investigate the atmosphere of Saturn's giant moon, Titan. The project will determine how Titan's climate system operatesand how the atmosphere redistributes solar energy over two of Titan's 7.5 Earth-year long seasons. Titan is one of only four terrestrial planets with atmospheres in our Solar System and provides uniqueinsight into how planetary atmospheres operate under extreme conditions.The final planetary science project is an investigation of how planets form from the small particles in the gas/dust disks around young stars. We now know that planets are very common around stars, but we are still unsure of how planets form, and even of the best way to search for forming planets within these disks. The purpose of the high-performance computer calculations to be done in this project is to predict where planets can be located in the types of disk that we know exist.Much cosmology over the past few years has been based on investigations of clusters of galaxies, and the fourth project is to investigate the sample of clusters of galaxies returned by the largest single survey conducted by the XMM-Newton X-ray astronomy satellite. This survey has found thousands of X-ray sources, about 1000 of which are clusters of galaxies which emit X-rays from the hot gas that they contain. This hot-gas emission can be used to estimate the masses of the clusters, and the distribution of cluster masses, which changes over cosmic time, is an excellent test for the type of Universe that we inhabit. The fifth project investigates one of the issues with understanding the atmospheres of clusters of galaxies - the question of why the radiation from their atmospheres doesn't cause them to cool down, and stop being X-ray sources. The answer seems to be that the gas in clusters is reheated by the ejection of very hot, fast, gas from the regions near black holes at the centres of some of the galaxies in the clusters. This project is aimed at understanding the processes involved in that heating, the physics of the fast gas ejections, and whether the gas coming out from near black holes can make cluster gas magnetic.While the clusters change with time, because of gas cooling and heating, and the changing size of the Universe, the galaxies within them also change. The sixth project is looking at how the galaxies within clusters change as the clusters change, and how clusters affect galaxies, and galaxies affect clusters. It is now possible to see very young clusters of galaxies, back when the Universe was only about 20% of its current age, and by tracking the changes in the galaxies and clusters from then until the present it may be possible to understand what is going on.The final project involves the maintenance and improvement of codes used to work with catalogues of astronomical objects. These codes are essential when dealing with modern astronomical data, and are used world-wide, so are of great importance to many astronomers. Some have even found their way into public products like the Microsoft World-Wide Telescope.