Imperial College Astrophysics Consolidated Grant 2016-2019

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Our research in Astrophysics includes theareas of cosmology (the study of the Universe), the most distantgalaxies, exoplanets (planets around other stars), and gravitationalwaves (distortion of space-time predicted by Einstein but so far notdetected). This work will make a contribution towards answering someof the greatest questions that can be posed, including: can we findsigns of life outside the solar system? and what is the fate of theUniverse? Our work involves a combination of theory andobservations. We use cutting-edge facilities such as the Planck andHerschel satellites, and LISA Pathfinder (to be launched in 2015), andwe also develop the theory and technology that will lead to proposals for thedevelopment of the next generation of satellites and experiments.Our understanding of the nature of the Universe has changed profoundlyover the past 20 years, since it was discovered that the expansion ofthe Universe is accelerating, and as experiments, primarily thoseobserving the cosmic microwave background, have allowed the accuratemeasurement of the parameters describing the Universe - theproportions of ordinary matter (atoms), dark matter, and dark energy,and the current rate of expansion. Dark matter clumps gravitationallyand outweighs ordinary matter by a factor 5, but what it consists ofis unknown. The even greater mystery is dark energy, which is causingthe acceleration of the Universe, and which dominates the mass-energybudget. Our work in cosmology takes different approaches to answeringthese problems. But the common theme in our research is theunderstanding that advances will come through improved experimentsthat measure quantities (cosmological distances, the rate ofexpansion) more accurately. The experiments rely on better technology(e.g. measurements of polarisation of the cosmic microwavebackground), better understanding of the physics under study (theproperties of supernovae used to measure cosmological distances), andbetter data analysis techniques that improve the precision andaccuracy of the results (applying rigorously the Bayesian formalism tocomplex large datasets).No less profound for humankind has been the discovery, again over thepast 20 years, of planets around many of the nearest stars in ourgalaxy, and the first characterisation of other stellarsystems. If the ultimate goal is to discover life on other planetsthis will be achieved through successive advances in understandinghow different types of planet (rocky/gaseous, large/small) form arounddifferent types of star (old/young, active/inactive, hot/cool) atdifferent radial separations, and of how the star over its lifetimecan affect the conditions on its planets. Our work in this areaincludes theoretical work to understand the mechanisms by whichplanets form, as well as developing a deeper understanding of stellarvariability and how this can subtly bias measurements of theatmospheres of planets (possibly leading to eroneous conclusions), aswell as influence the habitability of planets.A consequence of Einstein's 1915 theory of general relativity, whichdescribes the curvature of space-time due to mass, is that massiveobjects undergoing acceleration radiate energy in the form ofgravitational waves, propagating the signal of the change of curvatureat the speed of light. Gravitational waves have yet to be detected,but their detection is one of the great goals of physics. The effectis extremely subtle, so measurements in space away from sources ofvibration and the influence of the Earth are called for. Our researchon gravitational waves centres on contributing to the development oftechnologies for use in the planned European Space Agency mission LISA(not expected to launch before 2030), and analysis of data from theLISA Pathfinder mission, to be launched in 2015, that will testprototypes of these technologies.