Lovell Telescope, Jodrell Bank Observatory
The European Pulsar Timing Array is made up of scientists and engineers from over 20 institutions across Europe working in observations, instrumentation, data reduction, and theory. By using the 5 biggest radio telescopes in Europe (The 76-m Lovell in the UK, the 94-m equivalent WSRT in the Netherlands, the 100-m Effelsberg in Germany, the 64-m SRT in Sardinia, and the 94-m equivalent Nancay Radio Telescope in France), the EPTA is capable of observing at a wide range of frequencies with high cadence per source.
Gravitational waves are ripples in space-time, predicted by Einstein's theory of general relativity, which stretch and compress spacetime. As pulsars emit pulses with such amazing regularity, organisations such as the European Pulsar Timing Array can use pulsars as extremely accurate clocks, at distances of light years from the Earth. By comparing the measured pulse arrival times to the expected arrival times, the distortion of space caused by a passing gravitational wave should be detectable as a deviation from the timing model, correlated across all pulsars. Pulsar timing arrays are sensitive to extremely low-frequency gravitational radiation generated by supermassive black hole binaries, cosmic strings, and the inflationary era.
While gravitational waves have not been directly detected, their effect is significant in relativistic binary systems, such as the Hulse-Taylor binary (1993 Nobel Prize), and the double pulsar PSR J0737-3039. These systems convert large amount of orbital energy to gravitational radiation, which reduces the orbital distance, and will eventually cause the objects to merge catalysmically.
As well as confirming the prediction from general relativity, astronomers hope to be able to use gravitational waves to do astronomy. Astronomy generally only uses electromagnetic waves, which can be blocked by matter along the line of sight, and may not be emitted at all by black holes and dark matter. Gravitational wave astronomy on the other hand should allow us to observe the universe in an entirely new way.
For EPTA information, please contact James Mckee.