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.
This is the fourth time a
gravitational wave has been observed, but the first time scientists have been
able to trace the pattern of the ripples.
Gravitational are
distortions in the fabric of space-time created by some of the most violent
events in the universe.
The breakthrough 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.
The facility provides a new
level of detail on the 3D pattern of warping that takes place in gravitational
waves.
Predicted by Albert Einstein
100 years ago, gravitational waves 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.
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.
The arms on the new Virgo
facility in Italy are angled differently from those that form the LIGO
detector.
This means when used in
combination they better trace the vibrations and therefore the polarization of
gravitational waves when two bodies collide.
The event, code-named
GW170814, produced a new spinning black hole with 53 times the mass of the sun.
Travelling at the speed of
light, these ripples have taken 1.8 billion years to reach Earth.
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.
'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.'
Einstein’s theory predicts
two polarizations of gravitational waves, although others suggest there are
six, according to the Guardian.
This facility provides a new
understanding of the three dimensional pattern of warping that occurs when two
black holes collide.
It therefore strongly favors
Einstein’s predictions of how space-time is distorted.
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.