LISA and the search for Einstein’s waves

Scientists from across the world came together in London on 12-13 January to review the scientific and technical status of the LISA mission, the world’s first gravitational wave observatory, at a meeting organised by the Royal Astronomical Society (RAS) and the Institute of Physics.

Scheduled for launch in 2016, LISA will be the largest scientific instrument ever constructed, consisting of three spacecraft, each separated by 5 million kilometres (3 million miles). Its task will be to detect the elusive gravitational waves which were predicted by Einstein’s Theory of General Relativity, published in 1916. To date, although astronomers have indirect evidence of their existence, none have yet been detected directly.

LISA will be one of the most challenging space science missions ever flown. In order to detect the passage of a gravitational wave, the distance between the spacecraft must be measured by laser beams to an accuracy of ten picometres, about one millionth of the diameter of a human hair!

Gravitational waves are emitted when very massive objects such as black holes spiral violently together or when neutron stars collide at high speed. These invisible waves squeeze and stretch spacetime as they travel to us from distant parts of the universe,

The waves travel from the source without absorption and this allows scientists to study objects at very great distances and the events that took place immediately after the birth of the Universe. Various models of the early universe predict gravitational wave emission during the first tiny fractions of a second, and if these can be detected by LISA scientists will learn a great deal about the processes active at that time.

The technology needed for gravitational wave detection in space is being developed in Europe and the US, with a major role being played by the UK. Groups at the Universities of Glasgow, Birmingham, Imperial College London and the Rutherford Appleton Laboratory have been working for over ten years to perfect the necessary instrumentation and a flight test of this hardware is planned for 2009 on a space mission called LISA Pathfinder.

In addition to the preparation of the advanced technology, 10 other UK Universities (Warwick, Oxford, Aberdeen, Lancaster, Cambridge, Southampton, Portsmouth, University College London, Nottingham and Cardiff) are currently working on predicting astronomical signals and testing data analysis methods ready for the data from LISA.

Speakers at the RAS-IOP meeting came from the US, Italy, Germany and many groups in the UK. To emphasise the UK support for the science goals of LISA, the meeting participants were welcomed by Professor Keith Mason, Chief Executive of PPARC who praised the scientific and technical challenges being addressed by the UK teams and pointed out that LISA fulfilled one of PPARC’s major science goals. The meeting was concluded by Professor David Southwood, the ESA Director of Science, who drew attention to the unique science that LISA would accomplish.