Observation of Gravitational Waves from a Binary Black Hole Merger
Researchers at Cardiff University are part of the LIGO Scientific Collaboration responsible for the Nobel-prize winning discovery of gravitational waves emitted when two black holes merged.
Background
At 09:51 GMT on 14 September 2015, the two Laser Interferometer Gravitational Wave Observatory (LIGO) detectors picked up the first ever direct signature of gravitational waves. The signal was named GW150914 from 'Gravitational Wave' and the date of observation.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained.
They are ripples in the fabric of spacetime originating from a cataclysmic event in the distant universe. Their detection confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.
According to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes.
Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes. This merger produces a single, more massive, spinning black hole, converting a portion of the combined black holes’ mass to energy following Einstein’s famous formula E=mc2. This energy is emitted as a final, strong burst of gravitational waves.
Collisions of two black holes in this way had been predicted but never observed.
Response
The LIGO group is made up of more than 1000 scientists worldwide who have joined together in the search for gravitational waves.
Over more than a decade, researchers at Cardiff jointly with colleagues in the LIGO Scientific Collaboration, have developed sophisticated techniques to identify signals buried in the noisy data collected from the LIGO detectors, and distinguish them from artefacts in the data. This is achieved by “matched filtering” the data to identify signals which match the expected waveform emitted when two black holes merge.
Searching for events in the LIGO data requires sophisticated search algorithms and considerable computing power that includes the use of an established dedicated LIGO computational resource manintained by ARCCA as part of the Hawk supercomputer.
The computational resources provided by Cardiff University were used to identify the gravitational wave signal and understand its properties.
Outputs and impact
This essential LIGO work has contributed to the following:
- First direct observation of gravitational waves
- First observation of a black hole binary
- Precision tests of Einstein’s general theory of relativity
Key Academics and collaborators
Cardiff
Professor Stephen Fairhurst,
School of Physics and Astronomy
Mark Hannam,
School of Physics and Astronomy
Patrick Sutton,
School of Physics and Astronomy
Bangalore Sathyaprakash,
School of Physics and Astronomy
PRDAs and PhD students in the gravitational physics group