Showing posts with label electromagnetic spectrum. Show all posts
Showing posts with label electromagnetic spectrum. Show all posts

Tuesday, October 17, 2017

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