CPT Internet Highlights - Star Refuses to Die

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Science

This star refuses to die, even after it explodes

Swapna Krishna,Engadget

This star refuses to die, even after it explodes

Supernovae are some of the brightest and most energetic events in our galaxy. These occur when stars that have much greater mass than that of our sun explode; they become incredibly bright, and then slowly fade over the course of a few months as they lose energy. Under the terms of how we traditionally understand the life cycle of a star, a supernova inevitably means stellar death. Or does it? Astronomers working at Hawaii's Keck Observatory have found a star that refuses to die.

The supernova, named iPTF14hls, has exploded multiple times over the last fifty years. Rather than giving into death in the cold wastes of space, this singular star is seemingly in a cycle of continually absorbing matter, collapsing and exploding. The team first took note of the star in 2014 because it had gone supernova and was starting to fade. But then, a few months later, the team noticed that the star was becoming brighter again.

When the astronomers looked at records, they noticed that a supernova had occurred at that same location in 1954. The star had not only somehow survived, but had gone on to explode again in 2014. "This supernova breaks everything we thought we knew about how they work. It's the biggest puzzle I've encountered in almost a decade of studying stellar explosions," Iair Arcavi, the lead author of the study (which was published in Nature) said in a press release.

It's not clear why this star refuses to die, but it could have something to do with its size. It's at least 50 times more massive than our own star. Our conventional rules about how stars work might not apply to something of that size. The star could also have antimatter at its core that fuels its cycle of explosions, a hypothesized result of its extreme mass and temperature. Regardless of the reason, we appreciate this star's resilience

Keck Observatory , Nature

·         This article originally appeared on Engadget.

'ZOMBIE' STAR HAS BEEN EXPLODING FOR YEARS AND WILL NOT DIE

BY MEGHAN BARTELS ON 11/8/17

Usually, when something explodes, that's it—it's done. That's true even in space, where stars routinely blow themselves up. Now astronomers think they've spotted something remarkable: a star that has exploded twice and whose current explosion just keeps going. They reported their findings in a paper published Wednesday in the journal Nature.

Those findings are based on studying a star that scientists had written off as not being very interesting at first. Until, that is, an intern looked back at the data and saw something weird. "He saw it had faded and then gotten bright again, and that's what caught his attention," said first author Iair Arcavi, an astronomer at the University of California, Santa Barbara, and Las Cumbres Observatory. "That is very not normal. Supernovae are supposed to get bright and then fade."

The aftermath of a typical, short-lived supernova as it fades. NASA'S GODDARD SPACE FLIGHT CENTER/ESA/HUBBLE/L. CALCADA

But this one, called iPTF14hls, just kept going and going. First spotted in September 2014, it has brightened and dimmed five times since then, a phenomenon scientists had never seen before.

And when astronomers looked back at their records, they found something even weirder: An explosion in exactly the same part of the sky back in 1954. "We can't tell for sure that it's the same star exploding," Arcavi said. "But since supernovae are so rare and the galaxy is pretty small, we consider there's about a 95 to 99 percent chance that it's the same star."

Arcavi and his colleagues aren't positive yet what might be happening inside the star to cause such a weird pattern. But he pointed to a theory called pulsational pair instability as one possible explanation. Under this scenario, a star about 100 times as large as our sun could become so hot deep in its core that energy could turn into matter and antimatter, which would make the star unstable.

The star would then act like someone shoveling snow and gradually shedding outerwear: As it became unstable, it would eject a layer of mass, which would make it stable again for a limited time before heat builds up again. Each successive layer would eventually collide with its predecessor, which could explain the current pattern astronomers are seeing.

The yellow line traces the unprecedented cycle of brightening and dimming that astronomers have watched unfold.​LCO/S. ​WILKINSON.

But the pulsational pair instability theory doesn't perfectly match the data Arcavi and his colleagues had gathered. In particular, they found much more hydrogen in 2014 than they would have expected in a star that has already exploded, since hydrogen is the lightest element and therefore the easiest to lose.

"It's the theory that comes the closest to explaining this," Arcavi said of pulsational pair instability. "But it could also be something else. It could be something completely new, which is even more exciting."

It's unusual to even be able to keep watching a phenomenon like this every few days for three years, Arcavi added. Scientists have only caught the iPTF14hls antics thanks to a global network of robotic observatories that makes collecting data cheaper and easier. Fortunately, the same technique could increase astronomers' odds of seeing a similar event in the future—and coming one step closer to cracking the secret of the star that just doesn't want to die. 

Einstein Just Will Not Go Away - and a Good Thing - The Latest News

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Groundbreaking gravitational wave discovery shows Einstein's brilliance yet again

Miriam Kramer, Mashable 

Even 100 years after the fact, Albert Einstein is still getting his due. 

On Monday, more than a thousand astronomers and physicists around the world celebrated the announcement of a landmark discovery. For the first time, researchers saw the immediate aftermath of the merger of two neutron stars — leftover stellar remnants packed with more mass than our sun but with the diameter as small as the city of Boston.

Researchers detected both the ripples in space and time sent out by the colliding neutron stars as well as the light signature from the event. This marks the first time a cosmic collision has been seen in both light and gravity. 

It also represents another passing grade for Einstein's general theory of relativity, which he developed in 1915.

On the morning of August 17, the two LIGO detectors in Washington and Louisiana, as well as the Virgo detector in Italy, felt the subtle distortion of the fabric of space and time caused by the ripples — or gravitational waves — sent out by the colliding neutron stars. This collision created heavy elements like gold, platinum, and lead.

“What’s amazing with this discovery is that theoretically all of this that was observed on August 17th was actually predicted. Over a century ago, Einstein predicted that two orbiting objects will emit gravitational waves as they spiral in, and astrophysicists predicted that as two compact objects — especially neutron stars — collide, they should emit gamma-rays in jets," LIGO scientist Vicky Kalogera said during a press conference.

"And the cascade of light across the whole electromagnetic spectrum was predicted, and the production of heavy elements that might include gold and platinum should be produced," she added. 

"So it’s amazing to think that in one day, in a few hours and the weeks that followed, all of these predictions were confirmed."

Einstein's theory offers an elegant explanation for these gravitational waves.

Think of our universe as a top sheet laid across a bed. If you put two large objects on that sheet, it would create an indentation.

Our universe is similar. Massive objects like stars or black holes depress parts of the fabric of our universe. When two of these objects — like the two neutron stars — orbit one another, falling in toward each other and eventually merging, it can ripple that fabric, sending those waves out into the universe. 

Artist's illustration of the neutron star collision.

Image: caltech

Scientists had previously spotted gravitational waves sent out by black holes, but the August detection marks the first time LIGO or Virgo has observed colliding neutron stars.

At nearly that same time as LIGO and Virgo were riding the colliding neutron stars' gravitational wave, scientists also caught sight of a gamma-ray burst associated with that collision.

Katie Mack‏Verified account @AstroKatie  Oct 16

One of the things that the #GravitationalWaves #NeutronStar collision discovery confirms is that light and gravity travel at the same speed.

      Katie Mack‏Verified account @AstroKatie

We had good evidence for this from previous data, but this is very direct: gravitational waves & light travelling together, we time arrival.

This is very strong evidence that light and gravitational waves move at the same speed, something else that Einstein originally predicted.  Being able to observe cosmic events in light and gravitational waves is a huge deal for researchers.

While gravitational waves carry with them signatures of the objects that created them, being able to use more traditional observatories to see the event using light — whether it be in the infrared, X-ray, visible, or ultraviolet spectrum — can let scientists gather more information than ever before.

Science Astronomers just measured a whole lot more than gravitational waves

Mallory Locklear,Engadget 1 hour 10 minutes ago 

A couple of weeks ago, the LIGO (Laser Interferometer Gravitational-Wave Observatory) and Virgo teams announced the detection of another set of gravitational waves -- the fourth since LIGO's first detection in September of 2015. The observations of these ripples in spacetime are extraordinary in and of themselves, no matter how many times we record them. However, while the first three sets of gravitational waves recorded were by the two LIGO observatories, the fourth was also detected by a newly established third -- Virgo -- located in Italy. And having three detectors allows researchers to triangulate the source of those waves with extraordinary precision.

The importance of that precision was made clear today when the LIGO and Virgo teams announced a fifth gravitational wave detection, the source of which was able to be quickly located. This allowed dozens of other observatories to hone in on it and collect additional data including visual, X-ray, infrared, ultraviolet and radio wave recordings -- meaning researchers all around the world just collected, and are continuing to collect, a massive trove of information that has given us the most detailed look at a gravitational wave-generating event ever.

The previously recorded gravitational waves were caused by black holes merging many millions of light-years away. However, these new waves, recorded on August 17th, originated from the merging of two neutron stars -- very small but incredibly massive stars. They're what's left over after a massive star collapses and all of the protons and electrons get packed tightly together. They're around the size of a city, but 1.3 to 2.5 times the mass of our Sun. Just a teaspoon of a neutron star's matter can weigh more than one billion tons. The gravitational wave recordings indicated that this latest event was much closer than previous ones, around 130 million light-years from Earth.

Around the same time that LIGO and Virgo picked up the signal, a bright flash of gamma rays was detected by NASA's Fermi space telescope, and combined, those data allowed researchers to pinpoint which direction the waves were coming from. Armed with that knowledge, thousands of researchers around the world, manning more than 70 ground- and space-based observatories, were mobilized and all of them began collecting additional data from the neutron star merger. "This event has the most precise sky localization of all detected gravitational waves so far," Jo van den Brand, spokesperson for the Virgo collaboration, said in a statement. "This record precision enabled astronomers to perform follow-up observations that led to a plethora of breathtaking results."

This strategy, called multi-messenger astronomy, has been a goal of LIGO researchers from the very beginning because observing these sorts of events with gravitational waves and light at nearly the same time can provide far more detail than either can alone. "This detection opens the window of a long-awaited 'multi-messenger' astronomy," David Reitze, executive director of the LIGO Laboratory, said in a statement. "It's the first time that we've observed a cataclysmic astrophysical event in both gravitational waves and electromagnetic waves -- our cosmic messengers. Gravitational-wave astronomy offers new opportunities to understand the properties of neutron stars in ways that just can't be achieved with electromagnetic astronomy alone."

And the collection of data was truly a team effort. Once astronomers around the world were notified of the detection, the hunt began for the source. David Cook, a postdoc at Caltech, quickly made a list of 50 possible galaxies that could be hosting the neutron star merger. A few hours later the Swope Telescope located in Chile detected an optical signal that seemed to match the gravitational wave and gamma ray signals in a galaxy called NGC 4993. Shortly after that, the Gemini South telescope -- also in Chile -- detected an infrared signal from the same area.

So what have we learned from this event so far? Quite a lot actually, and more information is still being collected. The head of Caltech's astrophysical data analysis group for LIGO, Alan Weinstein, said, "The detection of gravitational waves from a binary neutron star merger is something that we have spent decades preparing for. On that morning, all of our dreams came true."

One major finding was that neutron stars give off gamma ray bursts when they merge, which had only been theorized before. But Fermi's initial recording, along with the confirmation from the European Space Agency's INTEGRAL gamma ray observatory, have finally provided researchers with solid evidence.

Secondly, a big question about where the heavy elements of our universe come from may have been answered. The lightest elements, hydrogen and helium, are thought to have been formed during the Big Bang while heavier elements from lithium up to iron are generated by stars. But where most of the other elements come from has been a bit of an unknown. That is, until now. Infrared observations from the likes of the Gemini Observatory, the European Very Large Telescope and the Hubble Space Telescope showed that the neutron star merger produced those heavier elements. "For the very first time, we see unequivocal evidence of a cosmic mine that is forging about 10,000 earth-masses of heavy elements, such as gold, platinum and neodymium," said Mansi Kasliwal, leader of the Global Relay of Observatories Watching Transients Happen project, a collaboration made up of dozens of astronomers and 18 telescopes on six continents.

There were a handful of surprises, though. The gamma ray signals that spewed out of the merger were surprisingly weak. And, even a week after the gravitational wave detection, researchers still hadn't observed any X-rays or radio waves. X-rays were eventually detected by NASA's Chandra X-ray Observatory nine days after the merger. It took 16 days for the Very Large Array in New Mexico to pick up any radio waves. These delayed waves and wimpy gamma ray signals spurred Kasliwal and her colleagues to design an explanatory model wherein a pressurized cocoon-like structure forms during the merger that traps the waves.

While the radio waves may be the slowest to arrive, they stick around much longer than the others and bring with them a ton of information, which could include how much energy was in the explosion, how much mass was spewed out and whether the merger might have an impact on star formation. "The radio emission arrives last but persists much longer than emissions at other wavebands," said Caltech astronomer Gregg Hallinan. "Radio comes late, and it comes slow, but it brings amazing information about the cosmic cataclysm."

This event is the most intensively studied transient astronomical occurrence in history and it's hard to overstate just how important it is. It has not only provided scientists with far more data than they've ever had on such an event, it demonstrated just how wildly effective multi-messenger astronomy is. With a global web of observatories all focused on the same target, we stand to make substantial advances in our understanding of how the universe formed and continues to evolve. "The story that is unfolding for this event is more complete than for any previous event in astronomical history," said Hallinan in a statement. "This complete story -- both hearing and seeing the violent universe -- is the gift of multi-messenger astronomy," he continued. Laura Cadonati, a physics professor at Georgia Tech and the spokesperson for the LIGO Scientific Collaboration said, "This detection has genuinely opened the doors to a new way of doing astrophysics. I expect it will be remembered as one of the most studied astrophysical events in history."

The data described today in a handful of papers published in Science and Physical Review Letters are just the beginning. Observatories around the world will be releasing more findings in the weeks and months to come and many will continue to observe the effects of the neutron star merger for months, even years. And this is just one event. "We even more eagerly anticipate the detection of gravitational waves from different kinds of known, extremely energetic astrophysical objects, like rapidly spinning pulsars, supernovae and neutron star quakes," said Weinstein, "and, especially, from heretofore unknown astrophysical objects." It is truly an astoundingly exciting time.

Images: LIGO-Virgo/Frank Elavsky/Northwestern (Stellar Masses); UC Santa Cruz and Carnegie Observatories/Ryan Foley (Swope Telescope Optical Image); LIGO-Virgo (Participating Observatories)

Neutron star smashup seen for first time, 'transforms' understanding of Universe

Mariëtte Le Roux, AFP

Paris (AFP) - Scientists have for the first time witnessed the crash of two ultra-dense neutron stars, cataclysmic events now known to have generated at least half the gold in the Universe, excited research teams revealed Monday.

Shockwaves and light flashes emitted by the cosmic fireball travelled some 130 million light-years to be captured by Earthly detectors on August 17, they revealed at simultaneous press conferences around the globe as a dozen science papers were published in top academic journals.

"We witnessed history unfolding in front of our eyes: two neutron stars drawing closer, closer... turning faster and faster around each other, then colliding and scattering debris all over the place," co-discoverer Benoit Mours of France's CNRS research institute told AFP.

The groundbreaking observation solved a number of physics riddles and sent ripples of anticipation through the scientific community.

Most jaw-dropping for many, the data finally revealed where much of the gold, platinum, mercury and other heavy elements in the Universe came from.

Telescopes saw evidence of newly-forged material in the fallout, the teams said -- a source long suspected, now confirmed.

"It makes it quite clear that a significant fraction, maybe half, maybe more, of the heavy elements in the Universe are actually produced by this kind of collision," said physicist Patrick Sutton, a member of the Laser Interferometer Gravitational-Wave Observatory (LIGO) which contributed to the find.

Neutron stars are the condensed, burnt-out cores that remain when massive stars run out of fuel, blow up, and die.

Some 20 kilometres (12 miles) in diameter, with slightly more mass than our sun, they are highly radioactive and ultra-dense -- a handful of material from one weighs as much as Mount Everest.

- 'Too beautiful' -

It had been theorised that mergers of two such exotic bodies would create ripples in the fabric of space-time known as gravitational waves, as well as bright flashes of high-energy radiation called gamma ray bursts.

On August 17, detectors witnessed both phenomena, 1.7 seconds apart, coming from the same spot in the constellation of Hydra.

"It was clear to us within minutes that we had a binary neutron star detection," said David Shoemaker, another member of LIGO, which has detectors in Livingston, Louisiana and Hanford, Washington.

"The signals were much too beautiful to be anything but that," he told AFP.

The observation was the fruit of years of labour by thousands of scientists at more than 70 ground- and space-based observatories scattered around the globe.

Along with LIGO, they included teams from Europe's Virgo gravitational wave detector in Italy, and a number of ground- and space-based telescopes including NASA's Hubble.

"This event marks a turning point in observational astronomy and will lead to a treasure trove of scientific results," said Bangalore Sathyaprakash from Cardiff University's School of Physics and Astronomy.

The detection is another feather in the cap for German physicist Albert Einstein, who first predicted gravitational waves more than 100 years ago.

Three LIGO pioneers, Barry Barish, Kip Thorne and Rainer Weiss, were awarded the Nobel Physics Prize this month for the observation of gravitational waves, without which the latest discovery would not have been possible.

The ripples have been observed four times before now -- the first time by LIGO in September 2015.

The fifth and latest gravitational wave observation is the first from a neutron star fusion. The other four were from black hole mergers which are even more violent but unlike neutron stars, emit no light.

- 'Earlier' than expected -

The latest wave observation, on the other hand, was accompanied by flashes of gamma rays, which scientists said came from closer in the Universe and were less bright than expected.

"What this event is telling us is that there may be many more of these short gamma ray bursts going off nearby in the Universe than we expected," Sutton said.

"This might be the tip of the iceberg of short gamma ray bursts produced by collisions and mergers of neutron stars" -- an exciting prospect for scientists hoping to uncover further secrets of the Universe.

Among other things, it is hoped that data from neutron star collisions will one day reveal the rate of expansion of the cosmos, which in turn would tell us how old it is and how much matter it contains.

"It is tremendously exciting to experience a rare event that transforms our understanding of the workings of the Universe," said France Cordova, director of the National Science Foundation which funds LIGO.

Secret of gold finally found: precious metals are forged in cataclysmic collision of neutron stars

Sarah Knapton,The Telegraph 1 hour 10 minutes ago 

The secret of creating gold has fascinated alchemists for thousands of years, but now scientists have finally solved the mystery.

Precious metals are forged in the cataclysmic collision of neutron stars and then flung out into the universe where they eventually aggregate with other stardust into larger bodies, like planets or comets.

Previously scientists had theorised that such cosmic smashes could create the vast amount of energy needed to create gold, platinum and silver, but for the first time, they have actually recorded it happening.

On August 17, astronomers in the US picked up a signal from two neutron stars crashing together 130 million years ago, when dinosaurs still roamed the Earth.

The impact, known as a ‘kilanova’ was so powerful that it shook not only space but also time, sending ripples - or gravitational waves - through the fabric of the universe.

The neutron star crash was so powerful it shook time and space sending a ripple out across the universe  Credit: LSC/Sonoma State University 

After the ripple was detected on Earth, astronomers across the world pointed their telescopes to the area of space from which it had originated and soon also picked up the bright afterglow from the collision. Inside that light were the distinct chemical signatures for gold, silver and platinum.

Dr Joe Lyman, of the University of Warwick, who was observing at the European Southern Observatory, in Germany, was the first to alert the scientific community to the fact they were witnessing a completely new event.

“The observations showed we were observing a kilonova, an object whose light is powered by extreme nuclear reactions,” he said.

“This tells us that the heavy elements, like the gold or platinum in jewellery, are the cinders, forged in the billion degree remnants of a merging neutron star.”

Neutron stars are created when giant stars die in spectacular supernovas. Their cores collapse, allowing protons and electrons to meld together to form neutrons, creating small yet incredibly dense stars. Just a teaspoon of neutron star material would have a mass of about a billion tons.

The two stars which were detected in August were as heavy as our Sun, yet only six miles (10km) across. They existed in a galaxy called NGC 4993.

The pair drew towards each other over millions of years, and revolved around each other increasingly quickly as they got closer – eventually spinning around each other five hundred times per second, until they crashed, forming either a larger neutron star or collapsing into a black hole.

The spacetime ripples created by the collision were detected by the Advanced Laser Interferometer Gravitational-Wave Observatory in Washington and Louisiana (Ligo). It was here the first discovery of gravitational waves was made in September 2015, confirming a prediction made by Albert Einstein 100 years ago and earning three pioneers of the project a Nobel Prize.

In that instance, black holes collided so only the ripples were detected because everything else was swallowed inside. But neutron stars are relatively lighter than black holes, so when they collide and merge, a small part of their mass and radiation does escape and can be detected along with gravitational waves.

The Theory of Relativity

Professor David Wiltshire, Department of Physics & Astronomy, University of Canterbury, said: “The first discovery of gravitational waves from the merger of two neutron stars is an historic event.

“It is every bit as exciting as the first discovery of gravitational waves from merging black holes. Since this involves neutron stars that radiate light, for the first time we can also see what is going on in an extreme astronomical event that shakes up space-time.”

Dr J.J. Eldridge, astrophysicist at the University of Auckland, added: “We’re all made of stardust, but gold, silver and platinum are made of neutron stardust.

“In this particular event, it’s likely that 100s or 1000s of Earth masses of gold and other elements were made. If the rate of neutron stars mergers is as high as we now think, these dying stars are now the source of most of these elements in the universe.”

The discovery has also solved the mystery of what creates short wave gamma ray bursts which are picked up on Earth and could help pinpoint how fast the universe is expanding.

Dr Samantha Oates, of Warwick’s Astronomy and Astrophysics group added: “This discovery has answered three questions that astronomers have been puzzling for decades: what happens when neutron stars merge? What causes the short duration gamma-ray bursts? Where are the heavy elements, like gold, made? In the space of about a week all three of these mysteries were solved.”

The new findings were published in research papers in the journals Nature, Nature Astronomy and Science.

Science News - Massive explosion from unknown source

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Massive explosion from unknown source billions of light years away baffles astronomers

Gamma ray burst detected from 12 billion light years away - but no one knows what caused it.

·                                 By David Coward

Updated April 3, 2017 14:58 BST

David Coward, University of Western Australia

At 10:49pm Western Australian time on February 2 this year, cosmic gamma rays hit the Nasa satellite, Swift, orbiting the Earth. Within seconds of the detection, an alert was automatically sent to the University of WA's Zadko Telescope. It swung into robotic action, taking images of the sky location in the constellation Ophiuchus.

What emerged from the blackness, where nothing was seen before, was a rapidly brightening "optical transient", which is something visible in the sky for a brief period of time.

The event, named GRB170202, was a very energetic gamma ray burst (GRB). After less than a minute, the gamma rays switched off, and the GRB appeared as a brightening and then fading optical beacon.

The Zadko Telescope recorded the entire evolution of the optical outburst. During its biggest outburst, GRB170202 was equivalent in brightness to millions of stars shining together from the same location.

About 9 hours 42 mins after the GRB, the Very Large Telescope in Chile acquired the spectrum of the light from the optical afterglow.

Zadko Telescope light curve of GRB170202, showing the evolving explosion and subsequent fading of the optical afterglow from seconds to hours after the gamma ray emission.Alain Klotz Zadko collaboration

This enabled a distance to the burst to be measured: about 12 billion light years. The universe has expanded to four times the size it was then, 12 billion years ago, the time it took the light to reach Earth.

GRB170202 was so far away, even its host galaxy was not visible, just darkness. Because the GRB was a transient, never to be seen again, it is like turning on a light in a dark room (the host galaxy) and trying to record the detail in the room before the light goes out.

Mystery of gamma ray burst

The flash of gamma radiation and subsequent optical transient is the telltale signature of a black hole birth from the cataclysmic collapse of a star. Such events are rare and require some special circumstances, including a very massive star up to tens of solar masses (the mass of our Sun) rotating rapidly with a strong magnetic field.

These ingredients are crucial to launch two jets that punch through the collapsing star to produce the gamma ray burst (see animation). The closest analogue (and better understood transient) to a GRB is a supernova explosion from a collapsing star. In fact, some relatively nearby GRBs reveal evidence of an energetic supernova linked to the event.

Simulations show that most collapsing stars don't have enough energy to produce a GRB jet, a so-called "failure to launch" scenario. Both observation and theory show that GRBs are extremely rare when compared to the occurrence of supernovae.

The stars that produce GRBs are born and die within some tens to hundreds of thousands of years, unlike our Sun which has been around for billions of years. This is because very massive stars exhaust their fuel very quickly, and undergo violent gravitational collapse leading to a black hole, on the timescale of seconds.

A plethora of rogue black holes

The rates of black hole formation throughout the universe can be inferred from the GRB rate. Based on the observed GRB rate, there must be thousands of black hole births occurring each daythroughout the entire universe.

So what is the fate of these cosmic monsters? Most will be lurking in their host galaxies, occasionally devouring stars and planets.

Others will be in a gravitational death dance with other black holes until they merge into a single black hole with a burst of gravitational waves (GWs), such as the first discovery of such an event by the Laser Interferometer Gravitational-Wave Observatory (LIGO).

At the frontier of understanding black hole formation is the search for a special kind of GRB that marks the merger (collision) of two neutron stars. So called "short GRBs" are flashes of gamma radiation that last less than a second and could be the "smoking gun" for neutron star mergers.

Importantly, merging neutron stars should be detected from their gravitational radiation by LIGO. Hence, a coincident detection in gamma rays, optical and gravitational waves is a real possibility.

This would be a monumental discovery allowing unprecedented insight into the physics of black hole formation. The revolution is like listening to the radio on a 1920s receiver and then watching a modern high definition surround sound movie.

Future challenges

Given the above rate of thousands of black holes created per day, it seems that coincident detection of GRBs and gravitational waves is a no brainer.

But in reality we must take into account the limited sensitivity of all the telescopes (and detectors). This reduces the potential observation rate to some tens per year. This is high enough to inspire a global scramble to search for the first coincident gravitational wave sources with electromagnetic counterparts.

The task is extremely difficult because the gravitational wave observatories cannot pinpoint the location of the source very well. To counter this, a strategy of searching for coincident gravitational wave and electromagnetic detections in time may be the best bet.

The newly funded ARC Centre of Excellence OzGrav mission is to understand the extreme physics of black holes.

One of the goals is to search for optical, radio and high energy counterparts coincident with gravitational waves from black hole creation. Australia is poised to play a significant role in this new era of "multi-messenger astronomy".

David Coward, Associate professor, University of Western Australia

This article was originally published on The Conversation. Read the original article.

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