Image copyright IGO/Caltech/MIT/Sonoma State Image caption Artwork: Two coalescing black holes spinning in a non-aligned fashion

Scientists are reporting yet another burst of gravitational waves.

The signals were picked up by the Advanced LIGO facilities in the US and are determined to have come from the merger of two huge black holes some three billion light-years from Earth.

It is the third time now that the labs' laser instruments have been perturbed by the warping of space-time.

The detection confirms that a new era in the investigation of the cosmos is now truly under way.

"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," said David Shoemaker, spokesperson for the LIGO Scientific Collaboration.

The latest detection, which was made at 10:11 GMT on 4 January, is described in a paper accepted for publication in the journal Physical Review Letters.

Media playback is unsupported on your device Media caption Five reasons why gravitational waves matter

Once again, it is a merger of black holes, and once again the energy scales involved are extraordinary.

The analysis suggests the two black holes that coalesced had starting masses that were just over 31 times and 19 times that of our Sun. And when they finally came together, they produced a single object of a little under 49 solar masses.

It means the unison radiated a simply colossal quantity of pure energy.

"These are the most powerful astronomical events witnessed by human beings," explained Michael Landry, from the LIGO lab in Hanford, Washington State.

"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."

Gravitational waves - Ripples in the fabric of space-time

Image copyright S.Ossokine/A.Buonanno (MPI Gravitational Physics) Image caption A computer simulation of gravitational waves radiating from two merging black holes

Gravitational waves are a prediction of the Theory of General Relativity

It took decades to develop the technology to directly detect them

They are ripples in the fabric of space-time generated by violent events

Accelerating masses produce waves that propagate at the speed of light

Detectable sources should include merging black holes and neutron stars

LIGO fires lasers into long, L-shaped tunnels; the waves disturb the light

Detecting the waves opens the cosmos to completely new investigations

As with the two previous observations - in September and December 2015 - the scientists are uncertain about where on the sky the 4 January event occurred. From the three millisecond gap between the signal being picked up first at Hanford and then at the second lab in Livingston, Louisiana, researchers can only specify a large arc of possibility for the source.

Conventional telescopes were alerted to go look for a coincident flash of light, but they saw nothing that could be confidently ascribed to the black hole merger.

The LIGO collaboration will only solve this triangulation problem when a third station called VIRGO, in Italy's Pisa province, starts work alongside the US pair this summer.

'Every 15 minutes'

The detection of gravitational waves has been described as one of the most important physics breakthroughs in recent decades.

Being able to sense the distortions in space-time that occur as a result of cataclysmic events represents a transformative step in the study of the Universe, one that does not depend on sensing electromagnetic radiation in any of its forms - from radio and optical light through to X-rays and gamma rays. Now, as well as trying to "see" far-off events, scientists can also "listen" to those events as they vibrate the very fabric of the cosmos.

And immediately this approach is telling researchers new things. One simple discovery is the recognition of a totally new class of black holes. Before LIGO's discoveries, orbiting pairs of these objects, some of 25 solar masses and greater, were completely unknown.

"In two years, we've gone from not knowing these systems existed to being really confident there's a whole population of them out there," commented Sheila Rowan, a collaboration team member from Glasgow University, UK. "And it's all consistent with gravitational waves from one of these systems passing through us about once every 15 minutes, from somewhere in the Universe," she told BBC News. The quest for the future is to get LIGO to sensitivities where more of these events can be detected.

Unbroken Einstein

Also possible now are new investigations of the properties of black holes. The scientists can tell from the nature of the 4 January signal that the spins of the objects were not fully aligned when they came together.

This suggests they were not created from a pair of previously orbiting stars that exploded and then collapsed into black holes. Rather, their origin was more probably as stars that led independent lives and only at some end stage fell in as a duo.

"In that first case, we would expect that the spins would stay aligned," said Laura Cadonati, the collaboration's deputy spokesperson. "So, we have found a new tile to put in the puzzle of understanding formation mechanisms."

In addition, gravitational wave astronomy permits new tests of Einstein's theories. Because of the greater distance to this merger (twice the distance to the 2015 events), researchers could more easily look for an effect called "dispersion".

For light, this describes how electromagnetic radiation of different frequencies will travel at different speeds through a physical medium - to produce a rainbow in a glass prism, for example.

Einstein's general theory of relativity forbids any dispersion from happening in gravitational waves as they move out from their source through space towards Earth.

"Our measurements are really very sensitive to minute differences in the speeds of different frequencies but we did not discover any dispersion, once again failing to prove that Einstein was wrong," explained Bangalore Sathyaprakash, a LIGO team member from Penn State, US, and Cardiff University, UK.

Image copyright NSF Image caption Hanford lab: Some of the big questions in science now require big machines to answer them

In a poignant coincidence, 4 January was also the day that Heinz Billing, a pioneer of gravitational wave science, died aged 102.

The German physicist and computer expert built one of the first laser interferometers - the instruments now used to detect gravitational waves. His early work is credited with making crucial contributions to the development of the eventual LIGO systems.

"His group started in about 1975, just before we did it here in Glasgow," recalled LIGO collaborator Jim Hough. "They were following the idea that the American Rai Weiss had had of using multiple beam delay lines, and of course the German detector was absolutely superb. They did fabulous work that has continued in Germany to this day."

A laser is fed into the machine and its beam is split along two paths

The separate paths bounce back and forth between damped mirrors

Eventually, the two beams are recombined and sent to a detector

Gravitational waves passing through the lab should disturb the set-up

Theory holds they should very subtly stretch and squeeze its space

This ought to show itself as a change in the lengths of the light arms

The photodetector captures this signal in the recombined beams

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos</s>On Jan. 4, an exquisitely sensitive instrument on Earth detected a disturbance that rippled through space and time. Scientists traced the ripple 3 billion light-years away, back to two ancient black holes on a collision course. This marked the third time in about a year that physicists, thanks to the Laser Interferometer Gravitational-wave Observatory, or LIGO, discovered gravitational waves from the violent death spirals of merging black holes.

The first gravitational wave discovery was announced in February 2016 and the second a few months later. The black holes identified in January were slightly smaller than those in the first detection, but they were much farther away, according to David Shoemaker, a research scientist at the Massachusetts Institute of Technology and spokesman for the LIGO Scientific Collaboration, an international group involving more than a thousand researchers. They reported the details of the new binary black hole system that generated the wave Thursday in the journal Physical Review Letters.

“Gravitational waves are distortions in the metric of space that we live in,” Michael Landry, a LIGO physicist at California Institute of Technology, said during a news conference Wednesday. He used a metaphor of a painting's canvas to describe distorted space. If you grip the top and bottom of the canvas and pull, the picture warps, expanding on one axis while contracting on the other.

Two L-shaped LIGO detectors, one in Washington state and the other in Louisiana, check for these distortions. They shoot synchronized laser beams down perpendicular vacuum tubes, each 2½ miles long. As a gravitational wave passes by, one arm of the L will shrink or expand, throwing the beams out of alignment. The Massachusetts Institute of Technology and California Institute of Technology spearhead the project, with support from the National Science Foundation and scientific agencies from a host of other countries.

“This is exactly what we hoped for from NSF's investment in LIGO: taking us deeper into time and space in ways we couldn't do before the detection of gravitational waves,” NSF director France Córdova said in a statement.

The signal in January failed to set off the usual automated alarm — the LIGO scientists had just restarted the detector, after a short winter break, and hadn't yet properly calibrated the trigger setting at the Washington site. A researcher in Germany, who happened to be poring over the LIGO data, first spotted the wave. (The wave would have been caught eventually, the LIGO team said; in a worst-case scenario there's an offline backup to review.)

The scientists named it GW170104. The wave hit Washington about 3 milliseconds before Louisiana. Given the data captured, the LIGO team calculated that the chance an event like this would be a false alarm would occur once every 70,000 years.

“The key thing to take away is we’re looking for novelty,” Shoemaker said during Wednesday's briefing. On these terms, the new black holes complied, at least a little bit.

Both of these black holes were much more massive than our sun. One was roughly 30 times solar mass, and the other 20 times the sun's mass, putting these black holes in the intermediate range between the first detection (two larger black holes) and second (two smaller black holes).

During this hole-on-hole merger, the equivalent of two solar masses were converted into gravitational waves. “These are the most powerful astronomical events witnessed by human beings,” Landry said.

The new detection also offered hints about the ways black holes spin with respect to their orbits. Georgia Tech astrophysicist Laura Cadonati on Wednesday likened the spinning black holes to a pair of tornadoes that dance around each other. Black holes can spin counterclockwise and clockwise, like tornadoes, but can also tilt at angles tornadoes could never achieve.

“We opened a new window into the universe,” Cadonati said. “Before our discoveries we didn't even know for sure that these black holes existed.”

It is possible that one of the black holes had a misaligned spin, which is to say that it was not spinning in the same direction as its overall spiral orbit. “We have an indication that at least one of the two spins is not aligned with the orbital angular momentum,” said B.S. Sathyaprakash, a cosmologist at Pennsylvania State University, during Wednesday's conference.

If the two black holes are not spinning in the same way, that hints at the way they met. Broadly speaking, there are two ways that binary black hole systems form: They began as an isolated pair of stars (think the dual Tatooine sunset in “Star Wars”) that collapsed, or the black holes collapsed independently in a dense star cluster. Cadonati said “this finding lightly favors the theory” of a cluster of stars.

And once again, Albert Einstein's General Theory of Relativity held up. Einstein's theory indicates that gravitational waves do not disperse through a physical medium, unlike light through a prism.

“Even for this new event, which is about two times farther away than our first two detections, we could not find any evidence that gravitational waves disperse as they travel in the fabric of space-time,” Alessandra Buonanno, a University of Maryland physics professor and LIGO collaborator, said in a statement.

The LIGO team continues to increase the detectors' sensitivity. In Louisiana, workers recently entered the vacuum envelope, clad in sterile bunny suits, to patch up areas where light could scatter in the tubes, cutting down on noise at low frequencies. In Washington, the observatory beefed up its laser to reduce high-frequency noise. With every improvement in clarity, LIGO can push its reach deeper into space.

The two teams will swap notes to improve their systems' range for the next run, scheduled to start in 2018. Italy's Virgo detector, too, is close to completion, which will join in LIGO's hunt for gravitational waves. It is possible, members of the LIGO team said during Wednesday's conference, that future discoveries could include merging neutron stars — collisions between the dense remnants of spent stars, the size of a city with the mass of a sun.

A brief history of gravity, gravitational waves and LIGO

A year later, scientists keep listening to gravitational waves, the soundtrack of the cosmos

For the second time ever, scientists detected gravitational waves from colliding black holes</s>Ripples in the fabric of spacetime emanating from two black holes crashing into each other about 3 billion light years away have been observed. The two black holes together will form a larger black hole about 50 times larger than the Sun.

Gravitational waves are distortions in the fabric of spacetime created when massive objects accelerate through it. The greater the object, the more ripples it would send out through spacetime.

Black holes are some of the most massive objects in the universe, and can be billions of times bigger than the Sun. When they collide, the biggest gravitational waves would be expected to be created.

The discovery published in the a paper in the journal Physical Review Letters is the third time echoes of gravitational waves have been directly observed. The first observations of gravitational waves were also from colliding black holes. The third has been named GW170104, and was made on 4 January 2017.

David Shoemaker of MIT, and spokesperson for the Laser Interferometer Gravitational-wave Observatory, the facility where the waves were observed, said in a statement: "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."

"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."

The observations are already revealing clues to the nature of black holes – the latest finding suggests that the two black holes in the binary system are not aligned in the way they're spinning, which hasn't been directly observed before.

"We're starting to gather real statistics on binary black hole systems," said Keita Kawabe of Caltech, an editor of the paper based at the LIGO Hanford Observatory.

"That's interesting because some models of black hole binary formation are somewhat favoured over the others even now and, in the future, we can further narrow this down."

Gravitational waves were one of Albert Einstein's key predictions, put forward in 1916. One aspect of his prediction was that the waves would not disperse through space. Dispersion is what happens when light passes through a prism to create a rainbow.

"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 of Georgia Tech and the deputy spokesperson for the LIGO Scientific Collaboration.

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

The LIGO instruments are now being upgraded, and will be put back to work again in January 2018. It's hoped that with even more sensitivity, the facility could start observing gravitational waves from objects other than black holes.

"We hope to see other types of astrophysical events soon, such as the violent collision of two neutron stars," concluded David Reitze of Caltech, executive director of the LIGO Laboratory.</s>On January 4, 2017, at 11:11:58 CET, scientists observed gravitational waves--ripples in the fabric of spacetime--for the third time.

The twin Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors--located in Livingston, Louisiana, and Hanford, Washington--detected the gravitational wave event, named GW170104. The LIGO Scientific Collaboration (LSC) and the Virgo Collaboration published a report describing the discovery and its implications on June 1, 2017 in the journal Physical Review Letters.

Gravitational waves carry information about their origins and about the nature of gravity that cannot otherwise be obtained. Physicists on the LIGO and Virgo teams concluded that, as with LIGO's first two historic detections, the final moments of a black hole merger produced the gravitational waves that LIGO observed on January 4, 2017.

LIGO's first detection, on September 14, 2015, resulted from a merger of two black holes about 36 and 29 times the mass of the sun. In contrast, the black holes that created the second event were relative flyweights, tipping the scales at 14 and eight times the mass of the sun.

The third and most recent detection lies in the middle, resulting from a merger between two black holes, more than 31 and 19 times the mass of the sun, respectively. The merger produced a single, more massive black hole that is slightly less than 49 times the mass of the sun, and transformed the remaining mass into gravitational energy.

"The observation and interpretation of yet another LIGO signal, GW170104, confirms the success of our theoretical program to model binary black holes," said Alessandra Buonanno, a UMD College Park Professor of Physics and LSC principal investigator who also has an appointment as Director at the Max Planck Institute for Gravitational Physics in Potsdam, Germany. Buonanno has led the effort to develop highly accurate models of gravitational waves that black holes would generate in the final process of orbiting and colliding with each other.

"For the third LIGO signal we could gather some evidence that at least one black hole might be rotating in a direction misaligned with the overall orbital motion--a spin configuration favored by some astrophysical formation scenarios of binary black holes" Buonanno added, noting that her team made substantial improvements to their methodology throughout 2016, in between LIGO's observing runs.

The newly detected merger occurred approximately 3 billion years ago, making it more than twice as old (and more than twice as distant) as the first two events, which occurred 1.3 and 1.4 billion years ago, respectively. Based on the arrival time of the signals--the Hanford detector measured the waves 3 milliseconds before the Livingston detector--researchers can roughly determine the position of the source in the sky.

The first detection of gravitational waves, announced on February 11, 2016, was a milestone in physics and astronomy. It confirmed a major prediction of Albert Einstein's 1915 general theory of relativity and marked the beginning of the new field of gravitational wave astronomy.

"The latest detection adds to the diversity of black hole merger events we've been able to observe directly," said Peter Shawhan, an associate professor of physics at UMD and an LSC principal investigator who serves as Data Analysis Committee Chair for the LSC. "We're conducting a census of black holes in binary systems in our universe and we expect to discover other types of signals too. Besides just counting them, we can learn from their properties how they were born and how they evolved."

The researchers also looked for an effect called dispersion, which is known to occur when light waves in a physical medium such as glass travel at different speeds depending on their wavelength. This is how a prism creates a rainbow, for example. Einstein's general theory of relativity forbids dispersion from happening in gravitational waves as they propagate from their source to Earth. LIGO did not find evidence for this effect in GW170104.

"Even for this new event, which is about two times farther away than our first two detections, we could not find any evidence that gravitational waves disperse as they travel in the fabric of space-time," Buonanno said.

"Einstein still seems to have been right about the true nature of gravity," Shawhan added.

The new detection occurred during LIGO's second observing run, which began November 30, 2016, and will continue through August 2017. The LIGO-Virgo team is continuing to search the latest LIGO data for signs of space-time ripples from the far reaches of the cosmos. They are also working on substantial technical upgrades for LIGO's third run, scheduled to begin in late 2018, with help from the nearly completed Virgo detector in Italy collecting data simultaneously.

The research paper, "GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2," by the LIGO Scientific Collaboration and the Virgo Collaboration, was published online June 1, 2017 in the journal Physical Review Letters.

The LIGO Laboratory is funded by the National Science Foundation (NSF), and operated by Caltech and MIT, which conceived and built the Observatory. The NSF led in financial support for the Advanced LIGO project with funding organizations in Germany (MPG), the U.K. (STFC) and Australia (ARC) making significant commitments to the project. More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, which is supported by Centre National de la Recherche Scientifique (CNRS), Istituto Nazionale di Fisica Nucleare (INFN) and Nikhef, as well as Virgo's host institution, the European Gravitational Observatory, a consortium that includes 280 additional scientists throughout Europe. Additional partners are listed at: http://ligo. .

University of Maryland 

College of Computer, Mathematical, and Natural Sciences 

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College Park, MD 20742 

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@UMDscience

The College of Computer, Mathematical, and Natural Sciences at the University of Maryland educates more than 7,000 future scientific leaders in its undergraduate and graduate programs each year. The college's 10 departments and more than a dozen interdisciplinary research centers foster scientific discovery with annual sponsored research funding exceeding $150 million.</s>Gravitational waves, ripples through the fabric of space-time predicted by Albert Einstein a century ago, have been detected for a third time.

Scientists first detected the shudders in space-time last year and the discovery was hailed the 'biggest scientific breakthrough of the century'.

Now, for the third time, researchers have detected the warping of space-time caused by a collision of two black holes colliding three billion light-years away - providing a new window on our universe.

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. In March 2014, a team operating the Bicep2 telescope, based near the South Pole, believed they had found gravitational waves, but their results were proven to be inaccurate.

The detection was made by the Ligo (Laser Interferometer Gravitational-Wave Observatory) Scientific Collaboration (LSC) on January 4, 2017.

As was the case with the first two detections, the waves were generated when two black holes collided to form a larger black hole.

The newfound black hole, formed by the merger, has a mass about 49 times that of our sun.

This fills in a gap between the masses of the two merged black holes detected previously by Ligo, with solar masses of 62 (first detection) and 21 (second detection).

'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 Dr David Shoemaker, a scientist at the Massachusetts Institute of Technology and the spokesperson for the Ligo scientific Collaboration.

'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.

'The entire Ligo and Virgo scientific collaborations worked to put all these pieces together.'

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.

The recent detection appears to be the farthest yet, with the black holes located about 3 billion light-years away.

Scientists said gravitational waves open a 'new door' for observing the universe and gaining knowledge about enigmatic objects like black holes and neutron stars.

Understanding such astronomical phenomena could be useful in helping us decipher how the universe first came to be.

'This [discovery is taking us deeper into time and space in ways we couldn’t do before the detection of gravitational waves,' said France Córdova, director of the National Science Foundation.

'In this case, we’re exploring approximately three billion light-years away.

'Ligo continues to make remarkable discoveries, transitioning from experiment to gravitational wave observatory.

'More importantly each detection has offered much more than just a sighting.

'Slowly, we are collecting data that unveil the origin and characteristics of these objects, further informing our understanding of the universe.'

WHAT IS THE THEORY OF RELATIVITY? Gravitational waves were predicted under Albert Einstein's (pictured) General Theory of Relativity in 1916 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. It was most recently demonstrated in the hit film film Interstellar. In a segment that saw the crew visit a planet which fell within the gravitational grasp of a huge black hole, the event caused time to slow down massively. Crew members on the planet barely aged while those on the ship were decades older on their return. The theory was most recently demonstrated in the hit film film Interstellar, in a segment that saw the crew visit a planet which fell within the gravitational grasp of a huge black hole, causing time to slow down massively, so crew members on the planet barely aged while those on the ship were decades older on their return

'We know this is just the beginning. This ‘window on the universe’ will continue to expand.

'We will watch eagerly as hundreds of researchers from around the world enhance this observatory to illuminate the physics of merging black holes, neutron stars and other astronomical phenomena.'

The newest observation also provides clues about the directions in which the black holes are spinning.

As pairs of black holes spiral around each other, they also spin on their own axes, much like a pair of ice skaters spinning individually while also circling around each other.

Sometimes black holes spin in the same overall orbital direction as the pair is moving, this is known as aligned spins, and sometimes they spin in the opposite direction of the orbital motion.

And black holes can also be tilted away from the orbital plane.

The new Ligo data implies that at least one of the black holes may have been non-aligned compared to the overall orbital motion.

More observations with LIGO are needed to say anything definitive about the spins of binary black holes, but these early data offer clues about how these pairs may form.

'This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that binary black holes may form in dense stellar clusters,' said Bangalore Sathyaprakash of Cardiff University.

There are two primary theories to explain how binary pairs of black holes can be formed.

The first model proposes that the black holes are born together: they form when each star in a pair of stars explodes, and then, because the original stars were spinning in alignment, the black holes likely remain aligned.

In the other model, the black holes come together later in life within crowded stellar clusters.

The black holes pair up after they sink to the center of a star cluster.

In this scenario, the black holes can spin in any direction relative to their orbital motion.

Because Ligo sees some evidence that the newly discovered black holes are non-aligned, the data favours this dense stellar cluster theory.

'We're starting to gather real statistics on binary black hole systems,' said Keita Kawabe, who is based at the Ligo Hanford Observatory.

'That's interesting because some models of black hole binary formation are somewhat favoured over the others even now and, in the future, we can further narrow this down.'

The study also once again puts Albert Einstein's theories to the test.

For example, the researchers looked for an effect called dispersion, which occurs when light waves in a physical medium such as glass travel at different speeds depending on their wavelength; this is how a prism creates a rainbow.

Einstein's general theory of relativity forbids dispersion from happening in gravitational waves as they propagate from their source to Earth.

And Ligo did not find evidence for this effect.

'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 of Georgia Tech University.

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

The team is continuing to search the latest Ligo data for signs of space-time ripples from the far reaches of the cosmos.

They are also working on technical upgrades for Ligo's next run, scheduled to begin in late 2018, during which the detectors' sensitivity will be improved.

At a press conference, the researchers spoke of their ambition to use Ligo to detect neutron stars.

Neutron stars are created when giant stars die in supernovas and their cores collapse, with the protons and electrons essentially melting into each other to form neutrons.

Researchers hope that improving the sensitivity of Ligo's instruments will help them to finally pinpoint signs of a neutron star, which could come as soon as 'this run or the next'.

They added a lack of understanding about how often neutron stars form could be holding them back from making a momentous discovery.

'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,' said 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.'

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 customer. As as result, researchers will be able to investigate black holes and neutron stars. The discovery will also help scientists confirm whether gravitational waves really do travel at the speed of light, as predicted. It will help scientists understand how fast the universe is expanding and what exactly makes stars explode. 'LIGO is just in the beginning with gravitational waves. Over the next decade or two we will have four gravitational windows open looking at the universe,' sad Kip Thorne, Feynman Professor of Theoretical Physics at Caltech.'</s>For the third time, scientists have detected a spacetime rumble caused by a violent collision of two black holes. The Laser Interferometer Gravitational-wave Observatory (LIGO) made the detection, determining that the two black holes merged to create one large black hole in a galaxy about 3 billion light-years away.

"We have observed – on the 4th of January, 2017 – another massive black hole-black hole binary coalescence; the in-spiral and merging of black holes 20 and 30 times the mass of our sun," Dave Shoemaker, a senior research scientist who works at Massachusetts Institute of Technology (MIT) and the spokesperson for the LIGO Scientific Collaboration, told reporters during a special news briefing on Wednesday (May 31).

This gargantuan black hole smashup created an even more massive spinning black hole, approximately 49 times the mass of our sun. In an instant, the equivalent mass twice that of our sun was converted directly into gravitational waves — briefly producing more energy than all the energy that is radiated as light by all the galaxies in the universe at any moment, LIGO scientists say.

After many years of planning, development and construction, LIGO took its first observations in 2002. However, it wasn't until Sept. 14, 2015, that the first historic detection of gravitational waves — an event called "GW150914" — was made. That happened after LIGO underwent upgrades (known as Advanced LIGO) to boost its sensitivity. Then, a second detection ("GW151226") followed a few months later in December, confirming that the first discovery was no fluke.

Now, the LIGO Scientific Collaboration — which consists of over a thousand scientists around the world — has confirmed the third gravitational wave detection ("GW170104"), meaning we're at the cusp of a completely new kind of astronomy.

All the gravitational waves detected so far have been created by the collision of stellar-mass black holes of varied sizes. These are black holes that are a few to a few dozen times the mass of our sun that were likely formed by the death of very massive stars after they'd run out of fuel and exploded as supernovas billions of years ago. Advanced LIGO has reached a crossroads in our gravitational wave search, finally reaching a sensitivity that can detect when very distant black holes collide, creating faint gravitational waves that we now know fill our universe.

The 2015 events were caused by mergers creating black holes 62 and 21 solar masses in galaxies 1.3 and 1.4 billion light-years away, respectively. (Note: As gravitational waves travel at the speed of light these mergers happened 1.3 and 1.4 billion years ago.) This latest detection originated from a merger creating a black hole of 49 solar masses (another "heavy" black hole like the first one), but the merger happened over twice as far away than previous events.

"What this means is that we now have a second candidate in the "heavy" black hole category," says Bangalore Sathyaprakash, of Penn State and Cardiff University and a member of the LIGO Scientific Collaboration.

This is important as, before LIGO made its first detection (a 62 solar mass black hole) and its most recent one (a 49 solar mass black hole), there was no observational evidence that these large black holes even existed. This is an incredible early discovery. Scientists have revealed a brand-new type of large black hole in only three detections.

Things are about to get even more exciting as LIGO undergoes more planned upgrades and other observatories join the hunt for gravitational waves.

"We should expect to see one binary merger event per day once LIGO's designed sensitivity is reached," says Sathyaprakash.

When gravitational waves are detected the conditions of the colliding black holes at the time of the merger can be studied.

"In our analysis, we cannot measure the spins of the individual black holes very well, but we can tell if the black holes are generally spinning in the same direction as the orbital motion," says astrophysicist Laura Cadonati, LIGO Scientific Collaboration deputy spokesperson from Georgia Tech.

But an idea of the individual black hole's spin relative to one another can be figured out by studying the "fingerprint" of the gravitational wave signal, says Cadonati.

Theoretical models of merging black holes indicate that if the two black holes' spins are not aligned, the merging event will happen faster than if the spins are aligned. Also, additional wobbles in the signal are predicted as two spin-aligned black holes get close and begin to merge.

Spin-aligned black holes were likely sibling stars. Both would have been born from massive stars that evolved in close proximity in ancient star factories as a binary pair, eventually dying as supernovas.

But in this most recent event, the merging occurred relatively quickly and no additional oscillations were observed, meaning the two black holes were likely not spin-aligned and probably didn't form together. This gives a clue to their origin: Rather than being formed from sibling binary stars, they were strangers and evolved independently, drifting toward one another in the center of a dense stellar cluster where they eventually merged.

"This has implications for astrophysics ... while we cannot say with certainty, this finding likely favors the theory that these two black holes formed separately in a dense stellar cluster, sank to the core of the cluster and then paired up, rather than being formed together from the collapse of two already paired stars," adds Cadonati.

As black holes are gravitational monsters, they're governed by Einstein's general relativity, so by studying the gravitational waves they produce when they collide, scientists also can study the waves for an effect known as "dispersion." For example, when light travels through a prism, the different wavelengths will travel at different speeds through the glass. This causes dispersion in the beam of light — this is the mechanism that creates a rainbow.

General relativity forbids dispersion from happening to gravitational waves, however. This latest signal traveled across a record 3 billion light-years of spacetime to reach Earth, and LIGO didn't detect any dispersion effects.

"It looks like Einstein was right – even for this new event, which is about two times farther away than our first detection," says Cadonati 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."

A New Window to the 'Dark Universe'

Einstein's famous theory of general relativity predicts the existence of gravitational waves, but it's taken humanity over a century to develop the technological know-how to build a detector sensitive enough to perceive them. When an energetic event occurs (like a black hole merger or neutron star collision), spacetime becomes violently disturbed and energy is carried away from the event in the form of gravitational waves — like ripples traveling across the water's surface after dropping a pebble in a pond.

But to detect these waves, astronomers need to build an observatory that can detect incredibly minuscule wobbles in the fabric of spacetime as these waves travel through our planet. Gravitational waves are not part of the electromagnetic spectrum; they cannot be detected by ordinary telescopes that are only sensitive to light.

To open the window to this "dark universe," physicists build gravitational wave detectors like LIGO that reflect incredibly precise lasers along 2.5 mile-long (4 kilometer-long) "L"-shaped tunnels. These tunnels are shielded from external vibrations caused by wind, traffic, tectonic activity and other terrestrial interference. Through a method known as laser interferometry, the distance between the reflecting mirrors inside the tunnel can be measured to a very high precision. Should a gravitational wave travel through our planet, a tiny change in distance may be recorded by the interferometer – this represents the minute squeezing and stretching of spacetime that occurs as gravitational waves propagate.

It's as if physicists have created a virtual tripwire that notifies us when an invisible gravitational wave intruder rumbles local spacetime.

One detector isn't enough to confirm a gravitational wave event, however. In the case of LIGO, one detector is located in Hanford, Washington, and another is located in Livingston, Louisiana — separated by 1,865 miles (3,002 kilometers). Only when the same event is detected by both locations can scientists confirm a gravitational wave signal. Two detectors can even determine a rough direction as to where the wave was traveling from, but if more detectors are added to the network, astronomers hope to eventually pinpoint, with increasing precision, where they originate.

More gravitational wave observatories are planned, and the European Virgo detector, located near Pisa, Italy, is currently undergoing commissioning. Once online, Virgo will be used in conjunction with LIGO to boost observational power of gravitational waves and allow better localization of the cosmic events causing the signals.

Now that the existence of gravitational waves has been confirmed, and astronomers are detecting more black hole mergers, we are entering a new era for astronomy. This is gravitational wave astronomy, where the dark universe will finally be revealed.</s>An international team of scientists - including 21 researchers from The University of Western Australia - has detected gravitational waves for the third time in history. The first time was in September 2015, then again in December 2015.

Gravitational waves are waves of energy, ripples in the fabric of space-time. The discovery of the first wave proved a prediction by Einstein 100 years ago.

The newfound black hole, formed by the pair's merger, has a mass about 49 times that of our sun. This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

These collisions produce more power during the instant before the black holes merge, than is radiated as light by all the stars and galaxies in the universe at any given time. The recent detection is the farthest yet, with the black holes located about 3 billion light-years away.

The black holes in the first and second detections are located 1.3 and 1.4 billion light-years away, respectively.

The third and most recent detection, called GW170104, was made on January 4 this year. The latest finding solidifies the case for a new class of black hole pairs, or binary black holes, with masses that are larger than what had been seen before by the Laser Interferometer Gravitational-wave Observatory (LIGO) detectors.

Professor David Blair, from UWA's School of Physics, said the event released more energy in its last few orbits than that of rest of the entire universe.

"Yet when the ripples passed the LIGO detector they made it vibrate by just one attometer, or 0.000000000000000001 metres," Professor Blair said.

Despite this tiny displacement, the scientists were able to demonstrate the black holes exhibited a property known as "spin".

"This is the first time that we have evidence that the black holes may not be aligned, giving us just a tiny hint that pairs of black holes may form in dense stellar clusters," Professor Blair said.

Postdoctoral Fellow Qi Chu, from UWA's School of Physics, is part of a team led by OzGrav Chief Investigator Professor Linqing Wen that is racing to create faster ways to crunch the LIGO data to minimise the time between the gravitational waves hitting earth and an alert being sent out for follow-up observations.

"The LIGO detector lets us feel the gravitational wave, and we are on a mission to see the source of the event by looking through powerful telescopes," Ms Chu said.

An international group of researchers, including the Australian International Gravitational Research Centre, is also investigating how to fine-tune the sensitivity of the gravitational waves detector, leading to improved detection of future gravitational waves and electromagnetic observational, and potentially more exotic sources.

LIGO is funded by the National Science Foundation (NSF), and operated by MIT and Caltech, which conceived and built the project. Financial support for the Advanced LIGO project was led by NSF with Germany (Max Planck Society), the U.K. (Science and Technology Facilities Council) and Australia (Australian Research Council) making significant commitments and contributions to the project.

More than 1,000 scientists from around the world participate in the effort through the LIGO Scientific Collaboration, which includes the GEO Collaboration. LIGO partners with the Virgo Collaboration, a consortium including 280 additional scientists throughout Europe supported by the Centre National de la Recherche Scientifique (CNRS), the Istituto Nazionale di Fisica Nucleare (INFN), and Nikhef, as well as Virgo's host institution, the European Gravitational Observatory.

The ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme. OzGrav is a partnership between Swinburne University (host of OzGrav headquarters), the Australian National University, Monash University, University of Adelaide, University of Melbourne, and University of Western Australia, along with other collaborating organisations in Australia and overseas.</s>In yet another historic moment, an international research team, including scientists from India, has announced the third detection of gravitational waves -- ripples in the fabric of space and time which were first predicted by Albert Einstein more than a century ago.

The Laser Interferometer Gravitational-wave Observatory (LIGO) in the US made the detection on January 4 this year, demonstrating that a new window in astronomy has been firmly opened.

Gravitational waves pass through Earth and can be "heard" by the extremely sensitive LIGO detectors.

As was the case with the first two detections, the waves were generated when two black holes merged to form a larger black hole.

"Our handful of detections so far is revealing an intriguing black hole population we did not know existed until now," said Northwestern University's Vicky Kalogera, a senior astrophysicist with the LIGO Scientific Collaboration (LSC).

The new detection, called GW170104, occurred during the ongoing second observing run of the Advanced LIGO detectors which began on November 30 last year.

The first direct observation of gravitational waves was made in September 2015 during the first observing run.

A second detection was made in December 2015.

The third detection is described in a new paper accepted for publication in the journal Physical Review Letters.

The publication has 40 authors from 11 Indian institutions.

IIT-Madras recently joined the LSC as one of the participating institutes, under the leadership of Dr Chandra Kant Mishra.

The Chennai Mathematical Institute has also been contributing to the activities under the leadership of Dr K.G. Arun.

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The group at IIT-Madras is involved in modelling the gravitational wave sources such as the ones which have been detected by the LIGO detectors so far as well as testing the consistency of the detected gravitational wave signals with the predictions of Einstein's general theory of relativity.

The third and latest detection points to merging black holes that are twice as far away from Earth as the two earlier pairs -- about three billion light-years away.

This time, the two black holes were unequal in size, one significantly lighter than the other. They merged into a black hole whose size is in the middle of the other two merged black hole pairs.

"Now we have three pairs of black holes, each pair ending their death spiral dance over millions or billions of years in some of the most powerful explosions in the universe. In astronomy, we say with three objects of the same type you have a class. We have a population, and we can do analysis," Kalogera added.

The newfound black hole, formed by the pair's merger, has a mass about 49 times that of our sun.

This fills in a gap between the masses of the two merged black holes detected previously by LIGO, which had solar masses of 62 (first detection) and 21 (second detection).

"We have further confirmation of the existence of black holes that are heavier than 20 solar masses, objects we didn't know existed before LIGO detected them," said David Shoemaker of MIT, the newly elected spokesperson for the LSC.

India is also working towards setting up its own LIGO observatory.

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The move received in-principle approval from the cabinet in February last year and has made rapid progress towards the plan to join these exciting scientific observations in 2024.

LIGO-India will greatly enhance the scientific capabilities of the international network of observatories for astronomy, primarily by enabling precise pointing to the location of the gravitational wave events in the sky.

Scientific and engineering teams at IPR Gandhinagar, IUCAA Pune and RRCAT Indore are actively engaged in the pre-construction activities of LIGO-India.</s>The Laser Interferometer Gravitational-wave Observatory on Thursday said that it has detected another merger of two black holes, which created gravitational waves. Scientists detected the black hole mergers on January 4 this year and named the gravitational wave GW170104.

This is the third time the existence of gravitational waves, a phenomenon predicted by Albert Einstein in 1916, has been confirmed. Bangalore Sathyaprakash, a senior scientist with Ligo, told The Hindu that the detection was “the first time, a chance event; second time, a coincidence, and third, a pattern.” The event was produced by the merger of two black holes, 31 and 19 times bigger than the sun, forming a larger black hole of about 49 solar masses. The results of the observations have been published in the journal, Physical Review Letters. The publication has 40 authors from 11 Indian institutions.

The new discovery is a game-changer. The waves will help scientists and astronomers examine everything from the essence of a black hole to the big bang itself. It will open up a new field called gravitational wave astronomy, which will help look into the earliest moments of the universe.

The new observation also supports Einstein’s General Theory of Relativity. According to this theory, gravitational waves do not disperse as they travel through space. Gravitational waves are ripples in the curvature of space-time, which is the very fabric of the universe. These waves are actual physical ripples that move away from each other and closer together, thus stretching and squeezing the space they exist in.

Ligo has a system of two detectors, one in Louisiana and another in Washington, to detect miniscule vibrations passing between gravitational waves. In 1974, the indirect detection of gravitational waves won scientists the Nobel Physics Prize. Experts say the first detection of the waves will be the discovery of the century, and will likely win the same honour.</s>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).

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.

"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."
Scientists announce that the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) has made a third detection of gravitational waves, named GW170104. The signal beam, detected on 4 January 2017, apparently results from a merger of two black holes of 19 and 31 solar masses. Such detections are said to be progressively moving this emerging field in astronomy "from novelty to new observational science".