Astrophysics at the University of Birmingham

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Most of our knowledge about the Universe at large has been derived from what scientists refer to as "electromagnetic radiation" - ranging from radio waves through infrared radiation and light, to X-rays and gamma rays. This has changed dramatically on September 14, 2015 when we directly detected for the first time ripples in space-time known as gravitational waves. The observational of the first gravitational-wave signal (GW150914) generated by the collision of two black holes has opened a new chapter in astronomy. We have discovered binary black holes, and learnt that every 15 minutes somewhere in the Universe two heavy stellar-mass black holes collide. In fact, since September 2015 we have observed five more collisions of this kind. On August 17, 2017 we observed GW170817, the first merger of a binary neutron star. Electro-magnetic radiation generated in the aftermath of the collision of the two neutron stars was then detected across the entire electromagnetic spectrum, from gamma-rays to radio waves, in possibly the most intense observational campaign of a single object in the history of astronomy. This first multi-messenger observation has demonstrated that double neutron star mergers are the engine powering at least some short-hard gamma ray bursts, and an important site for production of heavy elements, such as gold, in the Universe. The Birmingham group has played a key role in the development of the gravitational-wave instruments (Advanced LIGO) that enabled these discoveries, the analysis of the data, the characterisation of the properties of the sources, and the follow-up observational campaign of GW170817. In the coming years we expect to be able to observe a gravitational-wave signal every week, or possibly every day. We are preparing to use these signals from merging black holes and neutron stars to learn more about the evolution of these objects, stars, matter in extreme conditions, and to test our understanding of gravity itself. We are also developing the advanced technology which will be required to make future improvements to gravitational-wave observatories, so that more and much weaker signals can be observed and studied.The capabilities of more conventional instruments to probe the distant Universe, and the capacity of large computers to simulate the influence of massive black holes at the centre of galaxies, continue to improve. We are bringing these developments together to advance our understanding of how structure in the universe - massive black holes, galaxies and clusters - form and evolve through cosmic time. A hot topic in astrophysics is the effort to understand the mysterious "dark energy" which powers the accelerating expansion of the Universe. We plan to use clusters of galaxies as probes of the structure and expansion history of the Universe on the largest scales, to advance our understanding of the nature of dark energy