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UK scientists are helping us edge ever closer to finding the mysterious, theorised ripples in the fabric of spacetime (known as gravitational waves) with the production of 25 new assemblies for the LIGO facility – a network of detectors designed to search for these elusive waves.

Funded by the US National Science Foundation (NSF), LIGO also allows us to look inside the most violent events in the Universe and traces its exotic phenomena in great detail. By increasing the sensitivity of the LIGO detectors by a factor of ten, the upgrades will greatly increase our chances of finding gravitational waves and open a new observational window on the Universe to test our current theories and models.

The UK’s Science and Technology Facilities Council (STFC) is contributing £8.5m to this multimillion-dollar upgrade project, named Advanced LIGO, and is managing the UK’s overall involvement, including collaboration from the Universities of Glasgow, Birmingham, Strathclyde and Cardiff. The UK’s deliverables are suspension systems which help to ensure that the ultra-sensitive silica mirrors at the heart of the upgraded detector will not be influenced by ground-borne noise. The detector is sensitive to movements a hundred million times smaller than an atom so it is vital to ensure that stray noise sources are eliminated. Technology developed in the European GEO-600 project is being used to ensure the performance needed by Advanced LIGO. Shipping of the new parts to the US is currently underway.

The completion of the UK-made upgrades comes as the LIGO Scientific Collaboration (of which the UK-German GEO600 group is a founding member) and the Virgo Collaboration announce new results that have significantly advanced our understanding of the early evolution of the Universe.

In a paper published in Nature today (20th August) the scientists explain how LIGO observations have set the most stringent limits yet on the amount of gravitational waves that could have come from the Big Bang in the gravitational wave frequency band where LIGO can observe. In doing so, they have narrowed down the possibilities of how the Universe looked in its earliest moments.

Prof Jim Hough, UK Principal Investigator for the GEO600 project said, "This paper helps demonstrate the real excitement and potential of the field of gravitational wave studies to further our understanding of the Universe."

The Big Bang is believed to have created a flood of gravitational waves when the universe was very young. These waves still fill the universe today as background "noise", similar to random ripples on a pond on a windy day. The strength of this gravitational wave background is directly related to the way the Universe was in the first minute after the Big Bang, and the fact that we have not found any signal so far already tells us the maximum strength which this background could have.

This information builds on what we’ve learnt from studying the cosmic microwave background - heat radiation that tells us the way the universe was when it was about 380,000 years old. This is still very young compared with its present 14-billion year age, but much older than the time period probed by gravitational waves.

"Since we have not observed the gravitational waves from the Big Bang, some of these early-universe models that predict a relatively large background of waves have been ruled out," says Vuk Mandic, assistant professor at the University of Minnesota.

"We now know a bit more about parameters that describe the evolution of the universe when it was less than one minute old," Mandic adds.

Justin Greenhalgh, from the STFC Rutherford Appleton Laboratory, said, "Once it goes online, Advanced LIGO will allow us to further advance this research into the evolution of the early Universe. It will be able to detect cataclysmic events such as black-holes and neutron-star collisions at 10-times-greater distances and will be sensitive to sources of extragalactic gravitational waves in a volume of the universe 1,000 times larger than we can see at the present time. The new sensitivity of the instruments will propel our work forward and allow us to reveal more of the hidden mysteries of our Universe."

David Reitze, a professor of physics at the University of Florida and spokesperson for the LIGO Scientific Collaboration, added, "Gravitational waves are the only way to directly probe the universe at the moment of its birth; they’re absolutely unique in that regard. We simply can’t get this information from any other type of astronomy. This is what makes this result in particular, and gravitational-wave astronomy in general, so exciting."

Gravitational waves carry with them information about their violent origins and about the nature of gravity that cannot be obtained by conventional astronomical tools. The existence of the waves was predicted by Albert Einstein in 1916 in his general theory of relativity.

Professor Keith Mason, Chief Executive of the Science and Technology Facilities Council, said, "The new upgrades for LIGO will greatly improve our chances of finding gravitational waves. If LIGO detects them, it will be one of the biggest scientific breakthroughs of our age and one to which UK scientists contributed a great deal of skills and expertise. It will also open up a new kind of astronomy that will allow us to study the Universe in much greater detail in a way that does not rely on light."

The analysis used data collected from the LIGO interferometers, a 2 km and a 4 km detector in Hanford, Washington, and a 4 km instrument in Livingston, Louisiana. Each of the L-shaped interferometers uses a laser split into two beams that travel back and forth down long interferometer arms.

Notes

Nature Paper

The paper ‘An upper limit on the amplitude of stochastic gravitational wave background of cosmological origin’ is available from the STFC press office.

Images

Images are available from the STFC press office

LIGO

The LIGO project, which is funded by the National Science Foundation (NSF), was designed and is operated by Caltech and the Massachusetts Institute of Technology for the purpose of detecting gravitational waves, and for the development of gravitational-wave observations as an astronomical tool.

Research is carried out by the LIGO Scientific Collaboration, a group of 600 scientists from 12 different countries. The LIGO Scientific Collaboration interferometer network includes the LIGO interferometers (including the 2 km and 4 km detectors in Hanford, Washington, and a 4 km instrument in Livingston, Louisiana) and the GEO600 interferometer, located in Hannover, Germany, and designed and operated by scientists from the Max Planck Institute for Gravitational Physics and partners in the United Kingdom funded by the Science and Technology Facilities Council.

The next major milestone for LIGO is the Advanced LIGO Project, slated for operation in 2014. Advanced LIGO, which will utilize the infrastructure of the LIGO observatories, and will be 10 times more sensitive. Advanced LIGO will incorporate advanced designs and technologies that have been developed by the LIGO Scientific Collaboration. It is supported by the NSF, with additional contributions from the Science and Technology Facilities Council and the German Max Planck Gessellschaft.

Contacts:

Julia Short

Press Officer

Science and Technology Facilities Council

Tel: +44 (0)1793 442 012

Email: Julia.short@stfc.ac.uk

Justin Greenhalgh

STFC

Tel: 01235 445 297

Email: justin.greenhalgh@stfc.ac.uk