June 2, 2017
Third time’s a charm: LIGO detects gravitational waves for a third time
Scientists at the Advanced LIGO facility in Washington have once again detected gravitational waves, marking the third time in 18 months that the facility has observed ripples in the fabric of space-time that were originally predicted by Albert Einstein more than 100 years ago.
Officially known as the Laser Interferometer Gravitational-Wave Observatory, LIGO previously announced the detection of gravitational waves in February 2016 and June 2016 (although those events were actually recorded in September 2015 and December 2015, respectively).Like both of its predecessors, the latest gravitational wave is believed to have been created after the merger of two black holes – in this instance, black holes that were 31 times and 19 times the mass of our Sun merged to produce a single object of nearly 49 solar masses, according to BBC News. A paper detailing the observation has been published in Physical Review Letters.
“The key thing to take away from this third, highly confident event is that we're really moving from novelty to new observational science – a new astronomy of gravitational waves,” David Shoemaker, a spokesperson for the LIGO Scientific Collaboration (LSC) told BBC News.
“These are the most powerful astronomical events witnessed by human beings,” added Michael Landry, a scientist at the LIGO lab. “In this case two times the mass of the Sun were converted into deformations in the shape of space. This energy is released in a very short space of time, and none of this comes out as light which is why you have to have gravitational wave detectors.”
‘No deviation’ from general relativity detected, researchers confirm
The detection came in the early morning hours of January 4, 2017, LIGO researchers said in a press release, and the coalescing black holes were approximately three billion light years away from Earth when the collided, making this the most distant merger of its kind detected to date.
When the 31 solar mass and 19 solar mass black holes merged, two solar masses worth of black hole mass were converted into gravitational wave energy, which explains why the object that the observatory detected was only 49 times more massive than the sun, not 51, the authors explained.
Furthermore, that energy was released in just 0.12 seconds, as the black holes were orbiting each other at a velocity of six-tenths the speed of light, they added. Analysis of the phenomenon found that it adhered to predictions made by Einstein when he originally formulated his General Theory of Relativity back in 1916 – at least, to within measurable precision, according to LIGO.
“It looks like Einstein was right – even for this new event, which is about two times farther away than our first detection,” Laura Cadonati of Georgia Tech, the deputy spokesperson for the LSC, said in a statement. “We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence.”
Shoemaker added that the new observation provides “further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses” – objects which he said scientists “didn’t know existed before LIGO detected them.” Furthermore, it also provides evidence that suggests that at least one of the black holes may have been tilted away from the orbital plane at the time of the merger, the study authors added.
Image credit: Aurore Simonnet/Sonoma State, MIT, Caltech, LIGO