Astrophysics Consolidated Grant 2022 - 2025

Lead Research Organisation: Imperial College London
Department Name: Physics


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.


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