News

: Scientists from the Applied Optics group in the School of Physics at NUI Galway have been selected by the European Space Agency to carry out a study to detect gravitational waves from many different kinds of sources, such as massive stars rotating each other, or black holes spiralling into each other, as part of the space mission LISA (Laser Interferometer Space Antenna).

The European Space Agency (ESA) contemplates the possibility to launch in 2034 three spacecraft in the LISA mission, the first space-based gravitational wave observatory. Selected to be ESA’s third large-class mission, LISA will address the science theme of the Gravitational Universe. The purpose is to detect ‘gravitational waves’, which are tiny ripples in the fabric of space-time. To do this, the three spacecraft will be placed 2.5 million kilometres apart from each other in a triangular formation, following Earth in its orbit around the Sun to detect tiny changes in their separations.

The size of the changes is 1 ‘pico-meter’, which is 100 times smaller than an atom. Optical techniques are required to achieve this incredible precision, and the European Space Agency has contracted scientists from the Applied Optics group in the School of Physics at NUI Galway to carry out a study in order to ensure that such precision is indeed feasible. This follows on from the scientists’ recent successful completion of an ESA project to build a prototype Active Optics system for future Space Telescopes.

Each of the three spacecraft will carry two telescopes, one of which is used to transmit a laser beam to another LISA spacecraft, and one to receive a laser beam. The combined beams give rise to a pattern of bright and dark lines. Gravitational waves cause tiny changes in the spacecraft separation, and these lead to shifts in the pattern which can be detected. 

The ground-based LIGO (Laser Interferometer Gravitational – Wave Observatory) experiment has already detected gravitational waves due to coalescing black holes, with the experiment designers winning the 2017 Nobel Prize in Physics. However, these detections are very difficult on the ground due to interference from vibrations ranging from earth tremors to distant trucks. In space, LISA will be sensitive to many more sources of gravitational waves and will open up a whole new type of astronomy.

Dr Nicholas Devaney and Dr Fiona Kenny from the Applied Optics Group in the School of Physics at NUI Galway are writing software to precisely calculate the transmission of light between the LISA spacecraft’s. They will include the optical design of the telescopes and determine the effect of errors in the telescope optics. It is vital for the European Space Agency to know how the optics have to be made in order to be able to detect gravitational waves. This will determine the final telescope design and have a major impact on the mission. 

Speaking about the study Dr Nicholas Devaney from NUI Galway, said: “This is a fantastic opportunity for Irish scientists to be involved in this exciting mission. It recognises the expertise of NUI Galway scientists in the field of space optics and we plan to build on this work to expand Galway activities in this area.”

The NUI Galway gravitational wave spacecraft study is being carried out under a programme of and funded for by the European Space Agency.

For more information about LISA, visit: http://sci.esa.int/lisa/

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