Imperial College Astrophysics Consolidated Grant 2019 - 2022

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Our research in Astrophysics includes the areas of cosmology (thestudy of the Universe), the most distant galaxies, exoplanets (planetsaround other stars), and gravitational waves (distortion of space-timepredicted by Einstein, and recently observed for the first time). Thiswork will make a contribution towards answering some of the greatestquestions that can be posed, including: can we find signs of lifeoutside the solar system? and what is the fate of the Universe? Ourwork involves a combination of theory, observations, and laboratory work. We usecutting-edge facilities such as the Planck and Herschel satellites,and in the future the Euclid satellite, the Square Kilometre Array,and the Large Synoptic Survey Telescope. We also develop thetheory that will lead to proposals for the development of the nextgeneration of satellites and experiments. In addition we measure inthe laboratory fundamental properties of different atoms, forcomparison against observations of the different elements in stars.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.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 stellar systems. Ifthe ultimate goal is to discover life on other planets this will beachieved through successive advances in understanding how differenttypes of planet (rocky/gaseous, large/small) form around differenttypes of star (old/young, active/inactive, hot/cool) at differentradial separations, and of how the star over its lifetime can affectthe conditions on its planets. Our work in this area includestheoretical work to understand the mechanisms by which planets form,as well as developing a deeper understanding of stellar variabilityand how this can subtly bias measurements of the atmospheres ofplanets (possibly leading to erroneous conclusions).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, propagatingat the speed of light. After decades of development work, toimprove the sensitivity of the instruments, gravitational waves werefinally detected in September 2015 by the Advanced LIGO consortium.This discovery opens up an entirely new way of exploring the universe,offering rich new possibilities. Our interest in this field is inthinking ahead, by developing the theory of what might be detectable,to anticipate how to interpret new measurements, and to guide thedevelopment of the next generation of instruments.