Ripples in space-time generated by the collision of two black holes nearly two billion years ago have been captured by super-sensitive detectors in the US and Italy.
It is the first time the Virgo facility near Pisa has picked up a significant gravitational wave signal, marking a new turning point for scientists hunting the strange phenomenon.
Gravitational waves, which have only been observed four times in total, are distortions in the fabric of space-time created by some of the most violent events in the universe.
The collision of two black holes nearly two billion years ago has been captured by super-sensitive detectors in the US and Italy (stock image)
Scientists view the the universe as being made up of a ‘fabric of space-time’.
This corresponds to Einstein’s General Theory of Relativity, published in 1916.
Objects in the universe bend this fabric, and more massive objects bend it more.
Gravitational waves are considered ripples in this fabric.
They can be produced, for instance, when black holes orbit each other or by the merging of galaxies.
Gravitational waves are also thought to have been produced during the Big Bang.
If found, they would not only confirm the Big Bang theory but also offer insights into fundamental physics.
For instance, they could shed light on the idea that, at one point, most or all of the forces of nature were combined into a single force.
Predicted by Albert Einstein 100 years ago, they cause anything in their path to stretch and compress by an unimaginably tiny degree.
It is this minuscule change – amounting to a distance 1,000 times smaller than the width of a proton, the heart of an atom – that the scientists are looking for.
Using a network of American and European detectors for the first time, the international team was able to trace the latest source of gravitational waves to the merger of two black holes 1.8 billion light years away.
It has taken 1.8 billion years for the waves travelling at the speed of light to reach the Earth.
The event, code-named GW170814, produced a new spinning black hole with 53 times the mass of the sun.
During its violent birth, the equivalent of three solar masses was converted into gravitational wave energy.
British scientists played a key role in the discovery, as they did in the first ever confirmed detection of gravitational waves in September 2015.
Professor Andreas Freise, from the University of Birmingham’s Institute of Gravitational Wave Astronomy, said: ‘Once again, we have detected echoes from colliding black holes but this time we can pinpoint the position of the black holes much more accurately thanks to the addition of the Virgo detector to the advanced detector network.
‘Around ten years ago I was in charge of designing the core interferometer of the Advanced Virgo project. To see that instrument become a reality, and now helping to deliver significant results, is really special.’
Colleague Dr John Veitch, from the University of Glasgow’s School of Physics and Astronomy, who co-led the team carrying out analysis of the signal, said: ‘The addition to the network of a signal from Virgo provided us with a lot of useful data.
This is a view of the LIGO detector in Hanford, Washington. LIGO research is carried out by the LIGO Scientific Collaboration, a group of more than 1,000 scientists from universities around the US and 14 other countries
This is an aerial view of the Virgo site showing the Mode-Cleaner building, the Central building, the three kilometer-long west arm and the beginning of the north arm. The event, code-named GW170814, produced a new spinning black hole with 53 times the mass of the sun
HOW DOES THIS HELP US UNDERSTAND THE UNIVERSE?
Scientists said gravitational waves open a door for a new way to observe the universe and gain knowledge about enigmatic objects like black holes and neutron stars.
By studying gravitational waves they also hope to gain insight into the nature of the very early universe, which has remained mysterious.
Everything we know about the cosmos stems from electromagnetic waves such as radio waves, visible light, infrared light, X-rays and gamma rays.
But because such waves encounter interference as they travel across the universe, they can tell only part of the story.
Gravitational waves experience no such barriers, meaning they can offer a wealth of additional information.
Black holes, for example, do not emit light, radio waves and the like, but can be studied via gravitational waves.
Being able to detect gravitational waves will help astronomers probe the ‘dark Universe’.
This is the name given to the large part of the cosmos that is invisible to the light telescopes.
They will be able to look deeper into the universe, which means we could better understand the history of the cosmos.
‘Having a third detector means that we can now triangulate the position of the source, and much more accurately determine the exact spot in the cosmos where the signal came from.
‘We go through multiple stages of analysis. The first is filtering the data from the detectors, which provides us with triggers for possible detections, which are then checked against the data from the other detectors.
‘When a match between detectors is found, we can begin looking in more detail at the data to determine the mass and the position of the source, and start sharing data with other partners across the world.’
LIGO operates two detector sites – one near Hanford in eastern Washington, and another near Livingston, Louisiana (pictured)
THE THEORY OF RELATIVITY
Gravitational waves were predicted by Albert Einstein 100 years ago
In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers, and that the speed of light in a vacuum was independent of the motion of all observers – known as the theory of special relativity.
This groundbreaking work introduced a new framework for all of physics, and proposed new concepts of space and time.
He then spent 10 years trying to include acceleration in the theory, finally publishing his theory of general relativity in 1915.
This determined that massive objects cause a distortion in space-time, which is felt as gravity.
At its simplest, it can be thought of as a giant rubber sheet with a bowling ball in the centre.
As the ball warps the sheet, a planet bends the fabric of space-time, creating the force that we feel as gravity.
Any object that comes near to the body falls towards it because of the effect.
Einstein predicted that if two massive bodies came together it would create such a huge ripple in space time that it should be detectable on Earth.
The first gravitational wave detection in 2015 was made by the Laser Interferometer Gravitational Wave Observatory (Ligo) in the US. It too was the result of a pair of colliding black holes wrenching the fabric of space-time.
Two more Ligo detections quickly followed, also traced to merging black holes.
Ligo consists of two L-shaped detectors 1,865 miles (3,002 km) apart in Livingston, Louisiana and Hanford, Washington. Each arm of the L is a 2.5 mile (4km) long pipe containing a system of mirrors.
A passing gravitational wave will cause a tiny mismatch in the length of the two arms.
Laser beams fired through the pipes and bouncing off the mirrors are used to spot the discrepancy and alert the scientists.
The Virgo detector, based in Cascina, near Pisa, works the same way and has two three kilometre-long arms. A first version of the detector began operating in 2007 before a major upgrade to Advanced Virgo that was completed this year.
The new findings have been accepted for publication in the journal Physical Review Letters.