Astrophysics at Oxford 2019-2022

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

Abstract

Astrophysical research at Oxford University is carried out by investigators with universal interests, spanning scales from planetary to cosmic. We are actively engaged with many of the most exciting questions of modern physics.

On the scale of planetary phenomena, we seek to find new worlds and to understand how their atmospheres behave under extreme conditions. With knowledge of a planet's atmosphere, we may be able to learn something of its composition, and how it has evolved. Planetary researchers are interested in how other solar systems form and change with time, and why they seem to be so different from our own.

The study of black holes is one of the most exciting areas of astrophysics. We investigate the turbulent gas processes by which black holes grow as they accrete surrounding material, and calculate what one might observe when massive black holes in the centres of galaxies rip apart stars by tidal forces and devour the debris. Gas accretion can produce spectacular fireworks in a quasar or active galaxy, or barely a blip in the case of our own Milky Way Galaxy. Oxford researchers measure the radiation from molecules in distant galaxies to reveal the properties of the central black holes and their surroundings. We pursue studies at the cutting edge of black hole formation, tracking the radio waves emerging from the debris of neutron stars that have collided and coalesced into a black hole, and using this to understand the physics of this remarkable cosmic catastrophe.

On scales associated with our own Milky Way Galaxy, we study the motion of individual stars in great detail, using the results to understand how our Galaxy formed and maintains its structure, and how a great halo of invisible dark matter, which keeps the Galaxy bound, betrays its presence through the motions of the stars. We exploit observations of the galactic cluster environment, vast volumes filled with rarified magnetised gas heated to X-ray temperatures, to constrain the fundamental properties of matter suggested by string theory.

The evolution of galaxies throughout the Universe is influenced by their environment, which is in turn impacted by galactic feedback. To unravel the details of this galactic coupling through cosmic time is an enormous task. It requires the analysis of vast amounts of observational data. We maintain a large, active group of researchers pursuing this grand problem in all of its scope, from the highest redshifts at which galaxies form up to present cosmic times. Questions pertaining to the rate of star formation throughout cosmic time, to how galactic morphology may itself evolve, to whether the presence of neighbours causes galaxies' spin rotations to align, to how central black holes develop, are all being investigated at Oxford. This involves the use of current facilities as well as planning the design and implementation of key instruments to be associated with major international collaborations.

The largest scales of all are associated with the CMB, the cosmic microwave background. The exquisitely difficult but essential process of excising the foreground contamination caused by our own Galaxy is led by the Oxford team designing and building the C-BASS instrument. This is an example of how our researchers are developing techniques to coax profound secrets of the Universe from very sensitive data. What were the initial tiny fluctuations that gave rise to galaxies and their larger scale clusters? What constraints can be placed on the masses of elementary particles and deviations from classical general relativity? By combining information from CMB instruments like Planck with other data sets related to galaxy clustering, powerful new tools are being developed.

Planned Impact

Astronomy inspires and fascinates the specialist and non-specialist alike. Many Department members, representing a wide variety of interests, give public talks at all levels, including primary schools, high schools, policy makers, and industry. These activities are not merely confined to the UK, they extend into continental Europe and developing countries. We also hold hugely popular Stargazing Events for the public throughout the year, and engage the public more deeply in our activities with programmes like the citizen science projects Zooniverse, MoonZoo and Planet Hunters. Enabling schools in developing countries to carry out astronomy research via the Global Jet Watch Project is a particularly far-reaching activity.

In addition to our educational efforts, our research findings make significant contributions in areas such as turbulence (both when it occurs and when, despite expectations, it does not), weak signal detection, and heating and energy transfer in plasmas. These contributions are all important in making progress towards the solutions of societal problems. The challenge for us as astrophysicists is to understand the physical phenomena that are present under the extreme conditions found throughout the Universe, conditions that cannot be replicated in the laboratory. In meeting this challenge, we are able to understand and explore the laws of physics in environments that would not be remotely plausible or affordable here on Earth.

A case in point is that of plasma physics, in which progress in fusion is so crucial to the enduring supply of safe energy for the inhabitants of this planet. The sorts of problems frequently encountered in the development of fusion devices (e.g. anomalous energy transport and instabilities) have precise analogues in the study of astrophysical plasmas. We have close intellectual ties and many exchange visits with UKAEA Culham in order to expedite this knowledge exchange.

Climate change too, is of profound importance for the future. It can be difficult for the non-specialist to understand the important influences and consequences and is hindered by confused representations in the popular press. Astronomy, however, is non-partisan, and so the understanding gained from planets that are not our own makes it easier to comprehend, and bring a cleaner perspective to, the problems we have to grapple with on our home planet. In this way, case studies of exoplanets have the potential to make science that is ultimately important to life on Earth more accessible to the general public.

The state-of-the-art instrumentation with which we detect the most sensitive primordial signals from the early Universe drives significant advancements in industrial development. The research and development in, for example, our C-BASS project is feeding back into next-generation instrumentation such as the SKA radio telescope and industry itself. With further enhancements to our instrumentation programmes will come stimulation to industry in areas such as communications, microwave receivers, optics, interferometry, digital signal processing and remote sensing.

The extraction of minute signals from overwhelming backgrounds now involves advanced computation techniques. Our computational work thus has many positive consequences in the field of "Big Data", software development, as well as complex computation on GPUs - the graphics cards within even modest desktop computers that have been developed by the games industry - that we are exploiting for data management and computation.

Publications

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