Astrophysicists at Imperial College are using satellites and telescopes to measure how the Universe expands, how planets form around other stars, and how gravitational waves ripple through space-time. This work tackles three of the biggest unknowns in science: what dark matter and dark energy actually are, whether life exists beyond Earth, and how to interpret the new gravitational-wave signals that LIGO first detected in 2015. Dark matter outweighs ordinary atoms by a factor of five but remains unidentified; dark energy dominates the Universe’s mass-energy budget and drives its accelerating expansion. The team combines theory, observations, and laboratory measurements of atomic properties to improve the accuracy of cosmological distance measurements and planet atmosphere studies. This is fundamental science with no immediate practical application. However, the same kind of curiosity-driven research that revealed the accelerating Universe twenty years ago also led to technologies—precision detectors, data analysis methods, and satellite instrumentation—that now underpin GPS timing, climate monitoring, and medical imaging. Deeper understanding of dark matter, exoplanet atmospheres, and gravitational waves could similarly seed future tools for navigation, communications, or diagnostics that are impossible to predict today.
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Our research in Astrophysics includes the areas of cosmology (the study of the Universe), the most distant galaxies, exoplanets (planets around other stars), and gravitational waves (distortion of space-time predicted by Einstein, and recently observed for the first time). This work will make a contribution towards answering some of the greatest questions that can be posed, including: can we find signs of life outside the solar system? and what is the fate of the Universe? Our work involves a combination of theory, observations, and laboratory work. We use cutting-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 the theory that will lead to proposals for the development of the next generation of satellites and experiments. In addition we measure in the laboratory fundamental properties of different atoms, for comparison against observations of the different elements in stars. Our understanding of the nature of the Universe has changed profoundly over the past 20 years, since it was discovered that the expansion of the Universe is accelerating, and as experiments, primarily those observing the cosmic microwave background, have allowed the accurate measurement of the parameters describing the Universe - the proportions of ordinary matter (atoms), dark matter, and dark energy, and the current rate of expansion. Dark matter clumps gravitationally and outweighs ordinary matter by a factor 5, but what it consists of is unknown. The even greater mystery is dark energy, which is causing the acceleration of the Universe, and which dominates the mass-energy budget. Our work in cosmology takes different approaches to answering these problems. But the common theme in our research is the understanding that advances will come through improved experiments that measure quantities (cosmological distances, the rate of expansion) more accurately. The experiments rely on better technology (e.g. measurements of polarisation of the cosmic microwave background), better understanding of the physics under study (the properties of supernovae used to measure cosmological distances), and better data analysis techniques that improve the precision and accuracy of the results. No less profound for humankind has been the discovery, again over the past 20 years, of planets around many of the nearest stars in our galaxy, and the first characterisation of other stellar systems. If the ultimate goal is to discover life on other planets this will be achieved through successive advances in understanding how different types of planet (rocky/gaseous, large/small) form around different types of star (old/young, active/inactive, hot/cool) at different radial separations, and of how the star over its lifetime can affect the conditions on its planets. Our work in this area includes theoretical work to understand the mechanisms by which planets form, as well as developing a deeper understanding of stellar variability and how this can subtly bias measurements of the atmospheres of planets (possibly leading to erroneous conclusions). A consequence of Einstein's 1915 theory of general relativity, which describes the curvature of space-time due to mass, is that massive objects undergoing acceleration radiate energy in the form of gravitational waves, propagating at the speed of light. After decades of development work, to improve the sensitivity of the instruments, gravitational waves were finally 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 in thinking ahead, by developing the theory of what might be detectable, to anticipate how to interpret new measurements, and to guide the development of the next generation of instruments.
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