Research in planetary formation, astrophysics, and cosmology at Bristol

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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.