Research in planetary formation, astrophysics, and cosmology at Bristol

这项提案是为了在布里斯托尔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方面的几个重要问题。第一个项目是调查月球是如何形成的。目前最好的说法是，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结果不同。存在不同的撞击情景，在它们之间做出选择的关键是对月球上的元素混合（以及这些元素的不同同位素）进行良好的测量。该项目将对月球岩石进行比过去更精确的测量，期望能够选择一种模型而不是另一种模型。第二个项目涉及使用卡西尼号宇宙飞船的新数据来调查土星巨大卫星土卫六的大气。该项目将确定土卫六的气候系统是如何运作的，以及大气是如何在7.5个地球年长的两个季节中重新分配太阳能的。土卫六是太阳系中仅有的四颗有大气层的类地行星之一，它为我们了解行星大气层在极端条件下是如何运作的提供了独特的见解。最后一个行星科学项目是调查行星是如何从年轻恒星周围的气体/尘埃盘中的小颗粒形成的。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形成行星的最佳方法。在这个项目中，高性能计算机计算的目的是预测行星在我们已知存在的圆盘类型中的位置。过去几年的许多宇宙学研究都是基于对星系团的调查，第四个项目是对xmm -牛顿x射线天文卫星进行的最大单次调查返回的星系团样本进行调查。这次调查发现了数千个x射线源，其中大约1000个是星系团，它们从它们所含的热气体中发射x射线。这种热气体的发射可以用来估计星团的质量，而星团质量的分布，随着宇宙时间的推移而变化，是对我们所居住的宇宙类型的一个很好的测试。第五个项目调查了理解星系团大气的一个问题——为什么来自它们大气的辐射不会使它们冷却下来，不再是x射线源。答案似乎是，星系团中的气体通过从星系团中某些星系中心的黑洞附近区域喷出的非常热、快速的气体而重新加热。这个项目旨在了解加热过程，快速气体喷射的物理原理，以及从黑洞附近出来的气体是否会使星系团气体具有磁性。由于气体的冷却和加热以及宇宙大小的变化，星团会随着时间而变化，而星团内部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。现在有可能看到非常年轻的星系团，当宇宙只有现在年龄的20%左右时，通过跟踪从那时到现在的星系和星系团的变化，有可能了解发生了什么。最后的项目涉及维护和改进用于处理天文天体目录的代码。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。有些甚至进入了微软全球望远镜（Microsoft worldwide Telescope）等公共产品。

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.