New technology to help better detect gravitational waves

Scientists have developed a new technology that will make the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) even more sensitive to faint ripples in space-time called gravitational waves.
Researchers at Advanced LIGO announced the first-ever observation of gravitational waves earlier this year, a century after Albert Einstein predicted their existence in his general theory of relativity.
Studying gravitational waves can unveil important information about cataclysmic astrophysical events involving black holes and neutron stars.
Scientists from the Massachusetts Institute of Technology (MIT) in the US and Australian National University worked on improving what is called a squeezed vacuum source.
Although not part of the original Advanced LIGO design, injecting the new squeezed vacuum source into the LIGO detector could help double its sensitivity, researchers said.

This would allow detection of gravitational waves that are far weaker or that originate from farther away than is possible now.

For millennia, people have used light as a way of viewing the universe. Telescopes magnify what is visible with the naked eye, and newer telescopes use non-visible parts of the electromagnetic spectrum to provide a picture of the universe surrounding us.
"There are many processes in the universe that are inherently dark; they don't give off light of any colour," said Nergis Mavalvala, part of the MIT Kavli Institute for Astrophysics and Space Research team.
"Since many of those processes involve gravity, we want to observe the universe using gravity as a messenger," she said.

Researchers from the California Institute of Technology and MIT conceived, built and operate identical Advanced LIGO detectors in Louisiana and Washington in the US.
Each observatory uses a 4-kilometre long optical device known as an interferometer to detect gravitational waves coming from distant events, such as the collision of two black holes detected last year.
Laser light travelling back and forth in the interferometer's two arms is used to monitor the distance between mirrors at each arm's end.
Gravitational waves will cause a slight, but detectable variation in the distance between the mirrors. Both detectors must detect the variation to confirm that gravitational waves, not seismic activity or other terrestrial effects, caused the distance between mirrors to change.

The researchers are planning to add their new squeezed vacuum source to Advanced LIGO in the next year or so.
Once implemented, it will improve the sensitivity of the gravitational detectors, particularly at the higher frequencies important for understanding the composition of neutron stars.
These extremely dense stars contain the mass of the Sun, which has a radius of 700,000 kilometres, within just a 10-kilometre diameter.
The study was published in the journal Optica.