Riding the gravi-waves

Artist's impression of two black holes merging. Image: SXS
16 June 2016

Published in Physical Review Letters: Scientists, including from Australia, have detected gravitational waves for the second time.

The signal from this event was ten times longer than with the gravitational waves detected in December 2015. Both observations were made with the two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the United States.

Gravitational waves are caused by violent cosmic events such as collisions between stars or black holes, or explosions such as supernovae. They were predicted by Albert Einstein in 1916, but he thought they would be too small for humans to ever detect. However, with the Advanced LIGO project a new era of gravitational wave astronomy is now possible, which also promises major insights into the puzzles of dark energy and dark matter.

The now detected gravitational waves stem from an event around 1.4 billion years ago, when two black holes violently collided in a distant galaxy. During the journey to Earth, the gravitational waves died down so much that they stretched the LIGO detectors only a tiny fraction of the width of a proton.

The ripples reached the LIGO detector in Louisiana in the United States, and 1.1 milliseconds later the identical LIGO detector in Washington state.

The tiny signal was too small to be immediately seen amongst the background noise, but seventy seconds later the super-computer driven data processing systems found a match between the two detectors and alerted researchers of the find.

Work is already on the way to further improve the sensitivity of the LIGO detectors, including through Australian contributions. According to Professor David McClelland from the Australian National University, who leads Australia’s Partnership in Advanced LIGO, Australia's world-leading quantum optical devices will triple the searchable volume of the universe. “We’ll see many more discoveries announced over the next few years.”

Story based on information from the Australian National University