Gravitational waves spotted again, at furthest distance yet

Yahoo – AFP, Kerry SHERIDAN, June 1, 2017

A Laser Interferometer Gravitational Wave Observatory optics technician
inspectsone of LIGO's core optics (mirrors) (AFP Photo)

Miami (AFP) - Two massive black holes colliding into each other created ripples in space and time, known as gravitational waves, which have been detected at the furthest distance yet, international physicists said Thursday.

The galactic mash-up which produced the gravitational waves occurred some three billion light-years away, and marks the science world's third observation of this phenomenon.

The finding further bolsters Einstein's 1915 theory of general relativity, and comes two years after these enigmatic ripples were first detected, said the report in the journal Physical Review Letters.

"It is remarkable that humans can put together a story, and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us," said David Shoemaker, spokesman for the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration.

The group includes more than 1,000 international scientists who perform LIGO research together with the European-based Virgo Collaboration.

In all three cases, each of the twin detectors of LIGO detected gravitational waves from the tremendously energetic mergers of black hole pairs.

"These are collisions that produce more power than is radiated as light by all the stars and galaxies in the universe at any given time," said a LIGO statement.

The latest black hole collision, resulting in a detectable "chirp" of a gravitational wave, happened when two black holes merged, forming a new one that is about 49 times the mass of the Sun.

Its size is smack in the middle of the first such black hole merger detected by LIGO, at 62 solar masses, and the second which had 21.

"We have further confirmation of the existence of stellar-mass black holes that are larger than 20 solar masses -- these are objects we didn't know existed before LIGO detected them," said Shoemaker, a senior research scientist at the Massachusetts Institute of Technology (MIT).

Detecting gravitational waves (AFP Photo/Vincent LEFAI, Philippe MOUCHE)

Dark side of the universe

The first-ever direct observation of gravitational waves was made in September 2015, and detected an event some 1.3 billion light-years away.

The second came shortly after, in December 2015, and was a distance of 1.4 billion light-years.

The third detection, called GW170104, was made on January 4, 2017.

It was more than twice as old and more than twice as distant as the first two events.

"With the third confirmed detection of gravitational waves from the collision of two black holes, LIGO is establishing itself as a powerful observatory for revealing the dark side of the universe," says David Reitze of Caltech, executive director of the LIGO Laboratory.

"While LIGO is uniquely suited to observing these types of events, we hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars."

LIGO's observations are carried out by twin detectors -- one in Hanford, Washington, and the other in Livingston, Louisiana.

The observatories, which use laser interferometers to sense the presence of gravitational waves, are operated by Caltech and MIT with funding from the National Science Foundation (NSF).

"It looks like Einstein was right -- even for this new event, which is about two times farther away than our first detection," said Laura Cadonati, an associate professor at the Georgia Institute of Technology.

"We can see no deviation from the predictions of general relativity, and this greater distance helps us to make that statement with more confidence."