Astrophysics Consolidated Grant 2022 - 2025

Our research in Astrophysics includes the areas of cosmology (the study of the Universe), the most distant galaxies, and exoplanets (planets around other stars). 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 Simons Observatory and the Herschel satellite, and soon the Euclid satellite, the Square Kilometre Array, and the Large Synoptic Survey Telescope. In addition we measure in the

laboratory fundamental properties of different atoms, properties that cannot be predicted theoretically, for comparison against observations of the different elements in stars. Our understanding of the nature of the Universe has changed profoundly over the past 25-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 five, 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), and better data analysis techniques that improve the

precision and accuracy of the results. The latter is a particular strength of our team, which has been shaped in recognition of the importance of the optimal analysis of cosmological datasets, given that there is only one universe to experiment on, and that cutting edge experiments are very costly. No less profound for humankind has been the discovery, again over the

past 25-years, of planets around many of the nearest stars in our galaxy, and the first characterisation of other stellar systems i.e. analogues of our solar system. 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). The third theme in our work is the study of the first galaxies and stars. As we look out further in space we see the Universe as it was in the past,

because of the time light has taken to reach us. Eventually we will reach the point where we are seeing so far back in time that we find galaxies when they first formed. We quantify how far back we see by the redshift, the stretching of light by the expansion of the Universe. Our studies of the most distant known

star-forming galaxies and quasars explore redshifts of 4 to 8. To reach even further, to find the very first stars, ultima Thule, maybe at redshifts of 15, we are developing new radio techniques, exploiting the extremely faint redshifted 21cm wavelength transition of hydrogen.