Astrophysics Consolidated Grant 2022 - 2025

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Our research in Astrophysics includes the areas of cosmology (thestudy of the Universe), the most distant galaxies, and exoplanets(planets around other stars). This work will make a contributiontowards answering some of the greatest questions that can be posed,including: can we find signs of life outside the solar system? andwhat is the fate of the Universe? Our work involves a combination oftheory, observations, and laboratory work. We use cutting-edgefacilities 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 thelaboratory fundamental properties of different atoms, properties thatcannot be predicted theoretically, for comparison against observationsof the different elements in stars.Our understanding of the nature of the Universe has changed profoundlyover the past 25 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 five, 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), and better data analysis techniques that improve theprecision and accuracy of the results. The latter is a particularstrength of our team, which has been shaped in recognition of the importance of the optimal analysis of cosmologicaldatasets, given that there is only one universe to experiment on, andthat cutting edge experiments are very costly.No less profound for humankind has been the discovery, again over thepast 25 years, of planets around many of the nearest stars in ourgalaxy, and the first characterisation of other stellar systemsi.e. analogues of our solar system. If the ultimate goal is todiscover life on other planets, this will be achieved throughsuccessive 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 radialseparations, and of how the star over its lifetime can affect theconditions on its planets. Our work in this area includes theoreticalwork to understand the mechanisms by which planets form, as well asdeveloping a deeper understanding of stellar variability and how thiscan subtly bias measurements of the atmospheres of planets (possiblyleading to erroneous conclusions).The third theme in our work is the study of the first galaxies and stars. As welook 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 willreach the point where we are seeing so far back in time that we findgalaxies when they first formed. We quantify how far back we see bythe redshift, the stretching of light by the expansionof the Universe. Our studies of the most distant knownstar-forming galaxies and quasars explore redshifts of 4 to 8. To reacheven further, to find the very first stars, ultima Thule, maybe atredshifts of 15, we are developing new radio techniques,exploiting the extremely faint redshifted 21cm wavelengthtransition of hydrogen.