Gravitational wave science at the University of Birmingham

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 several tens of collisions of this kind, including a system of 150 times the mass of the Sun, the first observation of what astronomers refer to as an intermediate mass black hole.

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 one of the most intense observational campaigns 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 short-hard gamma ray bursts and an important site for production of heavy elements, such as gold and platinum, 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. We are now working on producing improved hardware for the Advanced LIGO upgrade (A+) which will increase the volume of the universe we can probe by a factor of ten, and on even more audacious technologies for more radical upgrades and new facilities for the next decade.

In the coming years we expect to be able to observe a gravitational-wave signal 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. The advanced technology which we are investigating will make future improvements to gravitational-wave observatories, so that much weaker signals can be observed and studied.