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The black-hole collision that reshaped physics

The black-hole collision that reshaped physics | Amazing Science | Scoop.it
A momentous signal from space has confirmed decades of theorizing on black holes — and launched a new era of gravitational-wave astronomy.

 

The event was catastrophic on a cosmic scale — a merger of black holes that violently shook the surrounding fabric of space and time, and sent a blast of space-time vibrations known as gravitational waves rippling across the Universe at the speed of light. But it was the kind of calamity that physicists on Earth had been waiting for. On 14 September, when those ripples swept across the freshly upgraded Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), they showed up as spikes in the readings from its two L-shaped detectors in Louisiana and Washington state. For the first time ever, scientists had recorded a gravitational-wave signal.

 

“There it was!” says LIGO team member Daniel Holz, an astrophysicist at the University of Chicago in Illinois. “And it was so strong, and so beautiful, in both detectors.” Although the shape of the signal looked familiar from the theory, Holz says, “it's completely different when you see something in the data. It's this transcendent moment”.

 

The signal, formally designated GW150914 after the date of its occurrence and informally known to its discoverers as 'the Event', has justly been hailed as a milestone in physics. It has provided a wealth of evidence for Albert Einstein's century-old general theory of relativity, which holds that mass and energy can warp space-time, and that gravity is the result of such warping. Stuart Shapiro, a specialist in computer simulations of relativity at the University of Illinois at Urbana–Champaign, calls it “the most significant confirmation of the general theory of relativity since its inception”.

 

But the Event also marks the start of a long-promised era of gravitational-wave astronomy. Detailed analysis of the signal has already yielded insights into the nature of the black holes that merged, and how they formed. With more events such as these — the LIGO team is analysing several other candidate events captured during the detectors' four-month run, which ended in January — researchers will be able to classify and understand the origins of black holes, just as they are doing with stars.

 

Still more events should appear starting in September, when Advanced LIGO is scheduled to begin joint observations with its European counterpart, the Franco–Italian-led Advanced Virgo facility near Pisa, Italy. (The two collaborations already pool data and publish papers together.) This detector will not only contribute crucial details to events, but could also help astronomers to make cosmological-distance measurements more accurately than before.

 

“It's going to be a really good ride for the next few years,” says Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics in Hanover, Germany. “The more black holes they see whacking into each other, the more fun it will be,” says Roger Penrose, a theoretical physicist and mathematician at the University of Oxford, UK, whose work in the 1960s helped to lay the foundation for the theory of the objects. “Suddenly, we have a new way of looking at the Universe.”

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Dark matter does not contain certain axion-like particles - Stockholm University

Dark matter does not contain certain axion-like particles - Stockholm University | Amazing Science | Scoop.it

Physicists are still struggling with the conundrum of identifying more than 80 percent of the matter in the Universe. One possibility is that it is made up by extremely light particles which weigh less than a billionth of the mass of the electron. These particles are often called axion-like particles (ALPs). Since ALPs are hard to find, the researchers have not yet been able to test different types of ALPs that could be a part of the dark matter.

 

For the first time the researchers used data from NASA's gamma-ray telescope on the Fermi satellite to study light from the central galaxy of the Perseus galaxy cluster in the hunt for ALPs. The researchers found no traces of ALPs and, for the first time, the observations were sensitive enough to exclude certain types of ALPs (ALPs can only constitute dark matter if they have certain characteristics).

 

One cannot detect ALPs directly but there is a small chance that they transform into ordinary light and vice versa when travelling through a magnetic field. A research team at Stockholm University used a very bright light source, the central galaxy of the Perseus galaxy cluster, to look for these transformations. The energetic light, so-called gamma radiation, from this galaxy could change its nature to ALPs while traveling through the magnetic field that fills the gas between the galaxies in the cluster.

 

“The ALPs we have been able to exclude could explain a certain amount of dark matter. What is particularly interesting is that with our analysis we are reaching a sensitivity that we thought could only be obtained with dedicated future experiments on Earth”, says Manuel Meyer, post-doc at the Department of Physics, Stockholm University.

 

Searches for ALPs with the Fermi telescope will continue. More than 80 percent of the matter in the Universe remains to identify. The mysterious dark matter shows itself only through its gravity, it does neither absorb nor radiate any form of light.

 

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Humongous black hole catches astronomers totally off guard

Humongous black hole catches astronomers totally off guard | Amazing Science | Scoop.it
Astronomers weren't expecting to find a supermassive black hole in this average-size galaxy, and they now may have to rethink their models.

 

One of the biggest black holes ever found sits in a cosmic backwater, like a towering skyscraper in a small town.

Astronomers have spotted a supermassive black hole containing 17 billion times the mass of the sun — only slightly smaller than the heftiest known black hole, which weighs in at a maximum of 21 billion solar masses — at the center of the galaxy NGC 1600.

 

That's a surprise, because NGC 1600, which lies 200 million light-years from Earth in the constellation Eridanus, belongs to an average-size galaxy group, and the monster black holes discovered to date tend to be found in dense clusters of galaxies. So researchers may have to rethink their ideas about where gigantic black holes reside, and how many of them might populate the universe, study team members said.

 

"This black hole is much bigger than we expected for the size of the galaxy or where this galaxy lives, the environment," said study co-author Chung-Pei Ma, an astronomer at the University of California, Berkeley.

 

"That's the puzzling part — or the intriguing part — of the result," she told Space.com. "There may be more NGC 1600s out there lurking at more ordinary sites, like small towns in the U.S. rather than Manhattan."Ma is head of the MASSIVE Survey, a multitelescope effort that began in 2014 to identify and catalogue the most massive nearby galaxies and black holes. NGC 1600 first showed up in the survey with data from the McDonald Observatory in Texas.

 

Although the initial observations weren't detailed enough to see the spectrum of light from the galaxy's center clearly, Ma and her colleagues could already tell that they were looking at something extraordinary: "It was a little bit like looking at a hurricane from very far away," she said. "We couldn't quite tell how big this hurricane was, this black hole was, but the hurricane was so big that we already started to feel the wind using this coarser data."

 

Suspecting they had spotted a very large black hole, study team members next investigated the elliptical galaxy using the northern half of the Gemini Observatory, twin telescopes situated in Hawaii and Chile. Gemini allowed them to probe the black hole's "sphere of influence," Ma said — the region where the black hole's mass held more sway than the overall galaxy's, where it was whipping the stars into action. They also scoped out the site with data from NASA's Hubble Space Telescope. The stars "were going so fast that the only way they could be travelling at this speed is if you had a 17-billion-solar-mass black hole at the center," she said.

 

The largest supermassive black hole ever found contains up to 21 billion times the mass of the sun, and resides in a more expected location: the incredibly dense Coma Cluster, which includes more than 1,000 identified galaxies. For comparison, the black hole lurking at the center of the Milky Way totals around 4 million solar masses.

 

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The black-hole collision that reshaped physics

The black-hole collision that reshaped physics | Amazing Science | Scoop.it

The event was catastrophic on a cosmic scale — a merger of black holes that violently shook the surrounding fabric of space and time, and sent a blast of space-time vibrations known as gravitational waves rippling across the Universe at the speed of light.

 

But it was the kind of calamity that physicists on Earth had been waiting for. On 14 September, when those ripples swept across the freshly upgraded Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), they showed up as spikes in the readings from its two L-shaped detectors in Louisiana and Washington state. For the first time ever, scientists had recorded a gravitational-wave signal.

 

“There it was!” says LIGO team member Daniel Holz, an astrophysicist at the University of Chicago in Illinois. “And it was so strong, and so beautiful, in both detectors.” Although the shape of the signal looked familiar from the theory, Holz says, “it's completely different when you see something in the data. It's this transcendent moment”.

 

The signal, formally designated GW150914 after the date of its occurrence and informally known to its discoverers as 'the Event', has justly been hailed as a milestone in physics. It has provided a wealth of evidence for Albert Einstein's century-old general theory of relativity, which holds that mass and energy can warp space-time, and that gravity is the result of such warping. Stuart Shapiro, a specialist in computer simulations of relativity at the University of Illinois at Urbana–Champaign, calls it “the most significant confirmation of the general theory of relativity since its inception”.

 

But the Event also marks the start of a long-promised era of gravitational-wave astronomy. Detailed analysis of the signal has already yielded insights into the nature of the black holes that merged, and how they formed. With more events such as these — the LIGO team is analysing several other candidate events captured during the detectors' four-month run, which ended in January — researchers will be able to classify and understand the origins of black holes, just as they are doing with stars.

 

Still more events should appear starting in September, when Advanced LIGO is scheduled to begin joint observations with its European counterpart, the Franco–Italian-led Advanced Virgo facility near Pisa, Italy. (The two collaborations already pool data and publish papers together.) This detector will not only contribute crucial details to events, but could also help astronomers to make cosmological-distance measurements more accurately than before.

 

“It's going to be a really good ride for the next few years,” says Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics in Hanover, Germany.

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Astronomers see supernova shockwave for first time

Astronomers see supernova shockwave for first time | Amazing Science | Scoop.it

The shockwave generated by the explosion of an ageing giant star has been observed for the first time by an international team of astronomers.

 

The discovery, accepted for publishing in the Astrophysical Journal, will help scientists understand the life cycle of stars, said study co-author Brad Tucker of the Australian National University.

 

"This is the first time we've seen this in the normal visible colours, and we now know it happens," Dr Tucker said.

"The fundamental way we believe that core collapse happens is related to this shockwave happening. So the physics has been around … for decades and we've finally now been able to physically examine and test what's going on."

 

The team of scientists observed the earliest moments of two old stars exploding using the Kepler Space Telescope. They spotted the shockwave around the smaller of the two stars — a red supergiant over 270 times the radius of the Sun and 750 million light years away. As the star ran out of fuel it began collapsing and compressing on its central core.

 

"It's like packing in dirt," Dr Tucker said. "You keep pressing it till it's so dense you can't get it in anymore, and that's when you create a neutron star. "But you reach a limit when you can't pack it in anymore, and that force pushing in bounces back and it triggers a shockwave to go through the star, causing the star to actually blow up."

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Beyond today's crowdsourced science to tomorrow's citizen science cyborgs

Beyond today's crowdsourced science to tomorrow's citizen science cyborgs | Amazing Science | Scoop.it
Computers are getting better and better at the jobs that previously made sense for researchers to outsource to citizen scientists. But don't worry: there's still a role for people in these projects.

 

We’re now entering an era in which machines are starting to become competitive with humans in terms of analyzing images, a task previously reserved for human citizen scientists clicking away at galaxies, climate records or snapshots from the Serengeti. This landscape is completely different from when I was a graduate student just a decade ago – then, the machines just weren’t quite up to scratch in many cases. Now they’re starting to outperform people in more and more tasks.

 

Rather than replacing citizen scientists, though, machines can help them – and it could not have come at a better time. Scientific experiments are flooding researchers with data: astronomers needed the help of the Internet to classify one million galaxies from an astronomical survey that took place in the 1990s and 2000s. Soon telescopes like the Large Synoptic Sky Telescope will give us images of billions of galaxies in addition to supernovae, asteroids and other strange things that go bump in the night.

 

How will astronomers be able to deal with all these data, many of which are time-sensitive? After all, if something goes “bump” and fades quickly, we’d want to try to study it more before it disappears forever. That’s where the machines can really help us: deep minds can scale up to process large data sets if we just give them sufficient processing power and memory.

 

But the machines still need help – our help! One of the biggest problems for deep neural nets is that they require large training sets, examples of data (say, images of galaxies) which have already been carefully and accurately classified. This is one way in which the citizen scientists will be able to contribute: train the machines by providing high-quality training sets so the machines can then go off and deal with the rest of the data.

There’s another way citizen scientists will be able to pitch in: by helping us identify the weird things out there we don’t know about yet, the proverbial Rumsfeldian “unknown unknowns.” Machines can struggle with noticing unusual or unexpected things, whereas humans excel at it.

 

Having the citizen scientists help the machines spot these unexpected things in the data would complement the machines’ ability to churn through huge data sets. If a machine got confused by something, or just wanted some extra feedback, it could kick the object back to a human for help, and then update itself to deal with similar things in the future. This could find applications not just in astrophysics, but in many other fields of science, from surveys of the sea floor to archives in museums, and the detectors of particle accelerators.

 

So envision a future where a smart system for analyzing large data sets diverts some small percentage of the data to human citizen scientists to help train the machines. The machines then go through the data, occasionally spinning off some more objects to the humans to improve machine performance as time goes on. If the machines then encounter something odd or unexpected, they pass it on to the citizen scientists for evaluation. Thus, humans and machines will form a true collaboration: citizen science cyborgs.

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A new view of the X-ray sky

A new view of the X-ray sky | Amazing Science | Scoop.it

Scientists at the Max Planck Institute for Extraterrestrial Physics (MPE) have revisited the all-sky survey carried out by the ROSAT satellite, to create a new image of the sky at X-ray wavelengths. Along with this a revised and extended version of the catalogue of bright and faint point-like sources will be released. The now published "2RXS catalogue" provides the deepest and cleanest X-ray all-sky survey to date, which will only be superseded with the launch of the next generation X-ray survey satellite, eROSITA, currently being completed at MPE.

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Gamma-ray bursts may place first lower bound on the cosmological constant

Gamma-ray bursts may place first lower bound on the cosmological constant | Amazing Science | Scoop.it

Sometimes when a star collapses into a supernova, it releases an intense, narrow beam of gamma rays. Gamma-ray bursts often last just a few seconds, but during that time they can release as much energy as the Sun will produce in its entire lifetime, making gamma-ray bursts the most powerful explosions ever observed in the universe. They are so intense that, if pointed at the Earth from even the most distant edge of our galaxy, they could easily cause a mass extinction, possibly obliterating all life on the planet. It's thought that a gamma-ray burst may have caused the Ordovician extinction around 440 million years ago, which wiped out 85% of all species at the time.

Clearly, the farther away a planet is from gamma-ray bursts, the better its chances of harboring advanced forms of life. In a new paper, scientists have shown that the gamma-ray burst risk to life favors a universe where all objects (like planets and gamma-ray bursts) are relatively far apart. And the main factor that tells how far apart everything is in the universe—or in other words, how things are spreading out and moving away from each other—is dark energy or the cosmological constant.

 

One of the biggest unanswered questions in cosmology is why does the cosmological constant have the particular value that scientists observe? Einstein initially devised the cosmological constant to be like an "anti-gravity" force, so that a larger value means that the universe is expanding very rapidly and objects are being pushed farther apart from each other. A smaller value means that the universe itself is smaller and objects are somewhat closer together.

 

Currently, the value of the cosmological constant is estimated to be about 10-123. Researchers have placed upper bounds on this value (it can't be more than 10-120 or else galaxies and other structures could not form because their matter could not have gotten close enough together). But so far, no research has been able to place a lower bound on the value.

 

By showing that the chances of advanced life existing is extremely small when planets are close to gamma-ray bursts, the new study makes an argument for placing the first lower bounds on the value of the cosmological constant. The scientists estimate that, when the value gets below 10-124, the number of protective "halos" of space (regions where planets stand a chance of avoiding gamma-ray bursts for long periods of time) sharply decreases. In other words, it would be pretty unlikely for humans to exist if the value were smaller than this number.

 

"We have found a lower limit on the cosmological constant," coauthor Tsvi Piran at The Hebrew University in Jerusalem told Phys.org. "As you know it is very small, 10-123. If it is so small, then why not zero? Zero is a 'round' number and one can look for a basic law of physics that will force the cosmological constant to vanish. Additionally, why not a negative value?"

 

By showing that the cosmological constant is very unlikely to be zero or negative, and much more likely to be close to its observed value, the results may help explain where this value comes from.

"This is important as it gives clues to the question of what is the origin of this constant," Piran said. "It is generally believed that the value of the cosmological constant is determined by some quantum process, and understanding its relevant range is important to have a clue on its origin."

 

The full analysis is more complicated, as the researchers had to account for other factors, such as the age of the universe—it can't be too young nor too old for advanced life. It can't be too old because planets need to orbit around a hydrogen-burning star like our Sun, which is young enough that it has not yet reached the end of its lifetime. But the universe also can't be too young because a galaxy (where protective halos reside) must have time to undergo chemical evolution to produce metal elements. A high metallicity decreases the odds of having a nearby gamma-ray burst, since the stars that cause these bursts have relatively low metal concentrations.

 

It's not surprising that Earth seems to occupy a favorable point in the researchers' simulations: a place with minimal exposure to gamma-ray bursts, and at a time with many hydrogen-burning stars like the Sun, along with a high average metallicity. This special place and time may help researchers search for other possible locations of life in the universe.

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Longest-lasting stellar eclipse: Three-and-a-half year eclipses in binary system

Longest-lasting stellar eclipse: Three-and-a-half year eclipses in binary system | Amazing Science | Scoop.it

Astronomers have discovered an unnamed pair of stars that sets a new record for both the longest duration stellar eclipse (3.5 years) and longest period between eclipses (69 years) in a binary system.


Imagine living on a world where, every 69 years, the sun disappears in a near-total eclipse that lasts for three and a half years. That is just what happens in an unnamed binary star system nearly 10,000 light years from Earth. The newly discovered system, known only by its astronomical catalog number TYC 2505-672-1, sets a new record for both the longest duration stellar eclipse and the longest period between eclipses in a binary system.


Discovery of the system's extraordinary properties was made by a team of astronomers from Vanderbilt and Harvard with the assistance of colleagues at Lehigh, Ohio State and Pennsylvania State universities, Las Cumbres Observatory Global Telescope Network and the American Association of Variable Star Observers and is described in a paper accepted for publication in the Astronomical Journal.


"It's the longest duration stellar eclipse and the longest orbit for an eclipsing binary ever found...by far," said the paper's first author Vanderbilt doctoral student Joey Rodriguez. The previous record holder is Epsilon Aurigae, a giant star that is eclipsed by its companion every 27 years for periods ranging from 640 to 730 days.


"Epsilon Aurigae is much closer -- about 2,200 light years from Earth -- and brighter, which has allowed astronomers to study it extensively," said Rodriguez. The leading explanation is that Epsilon Aurigae consists of a yellow giant star orbited by a normal star slightly bigger than the sun embedded in a thick disk of dust and gas oriented nearly edge on when viewed from Earth.


"One of the great challenges in astronomy is that some of the most important phenomena occur on astronomical timescales, yet astronomers are generally limited to much shorter human timescales," said co-author Keivan Stassun, professor of physics and astronomy at Vanderbilt. "Here we have a rare opportunity to study a phenomenon that plays out over many decades and provides a window into the types of environments around stars that could represent planetary building blocks at the very end of a star system's life."


Two unique astronomical resources made the discovery possible: observations by the American Association of Variable Star Observers (AAVSO) network and the Digital Access to a Sky Century @ Harvard (DASCH) program.

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Shafique Miraj Aman's curator insight, March 2, 2016 5:44 AM

69 years(not a sexual innuendo) of having no natural light. now that actually sounds fun

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Fast radio burst tracked to faraway galaxy

Fast radio burst tracked to faraway galaxy | Amazing Science | Scoop.it

For the first time, scientists have tracked the source of a "fast radio burst" - a fleeting explosion of radio waves which, in this case, came from a galaxy six billion light-years away. The cause of the big flash, only the seventeenth ever detected, remains a puzzle, but spotting a host galaxy is a key moment in the study of such bursts. It also allowed the team to measure how much matter got in the way of the waves and thus to "weigh the Universe". Their findings are published in Nature.

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Shafique Miraj Aman's curator insight, February 29, 2016 11:30 PM

A e s t h e t i c a l l y                              A p p e a l i n g

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Gravitational waves: How LIGO forged the path to victory

Gravitational waves: How LIGO forged the path to victory | Amazing Science | Scoop.it
Historic discovery of ripples in space-time meant ruling out the possibility of a fake signal.


At 11:53 a.m. local time on 14 September 2015, an automated e-mail appeared in the inbox of Marco Drago, a physicist at the Max Planck Institute for Gravitational Physics in Hannover, Germany. It contained links to two plots, each showing a wave shaped like a bird’s chirp that emerged suddenly from a noisy background and ended in a crash.


It was a signal that Drago had been trained to spot and that the US-led Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) that he works on was built to detect: the signature ripples in space-time produced when two black holes collide to form a single gravitational sink. No one had ever directly detected gravitational waves before, nor a black-hole merger. The plots, one from each of LIGO’s twin detectors in Washington state and Louisiana, would go on to make history.


On 11 February, the LIGO collaboration announced that it had made the first detection of gravitational waves from a black-hole merger that occurred about 400 million parsecs (1.3 billion light years) from Earth. It was just over 100 years after Albert Einstein predicted such waves as part of his general theory of relativity. “We did it!” David Reitze, the executive director of the LIGO Laboratory, said at a press conference in Washington DC.

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Einstein’s Gravitational Waves Detected Originating from Merging Black Holes 1.3 Billion Years Ago

Einstein’s Gravitational Waves Detected Originating from Merging Black Holes 1.3 Billion Years Ago | Amazing Science | Scoop.it
Today, scientists announced that, for the first time in history, gravitational waves have been detected.

Gravitational waves are ripples in spacetime throughout the universe. What’s truly remarkable about this discovery is that Albert Einstein predicted the existence of gravitational waves 100 years ago, but scientists have never been able to detect them, until now.

The discovery came out of the U.S. based Laser Interferometer Gravitational Wave Observatory (LIGO). The mission of LIGO was to directly measure gravitational waves. In order to do that, LIGO scientists needed to construct the most precise measuring device the world had ever seen.

The LIGO project, which began in 1992, was the largest scientific investment the National Science Foundation (NSF) has ever made.

At an NSF press conference this morning, LIGO Laboratory Executive Director, David Reitze, said “This was a scientific moon shot. And we did it – we landed on the moon.”


LIGO consists of two 4 kilometer (2.5 mile) tunnels located in Louisiana and the state of Washington. Because gravitational waves stretch space in one direction and compress space in the other, LIGO was designed to measure changes in length across large land distances. If they could detect a stretch of land in the LIGO tunnels in one direction and compression in the other, they could theoretically detect a gravitational wave.


The “ruler” that scientists used to measure these tunnel lengths was the speed of light. The speed of light is constant, so LIGO can determine the length of the tunnels by measuring the time it takes for a laser to bounce from one end of the tunnel to the other.


Gravitational waves are created when masses accelerate. Measured back on September 14th, 2015, the gravitational wave signal that the LIGO scientists detected matches the exact signal they’d expect from two merging black holes accelerating at half the speed of light.


Reitze explained that the black holes that created this gravitational wave merged 1.3 billion years ago. It took that long for the wave to travel to the Earth. Each of the black holes were 30 times the mass of the sun and were accelerating at half the speed of light when they collided into each other. The ability to measure gravitational waves will open up an entirely new window for astronomy. Reitze explained that this will enable scientists to look at the universe in a new way.


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Ancient black holes can outshine entire galaxies

Ancient black holes can outshine entire galaxies | Amazing Science | Scoop.it

Quasars are extreme in almost every way. They can outshine their entire galaxies; their black holes can be billions of times more massive than the Sun; their temperatures reach tens of millions of degrees; and some of them fire jets of charged particles into space that can reach almost light speed. But before Schmidt realized that the first quasar, dubbed 3C 273, was something extraordinary, it had been a puzzle. It was one of many so-called radio galaxies that astronomers were discovering in the 1950s.


These galaxies produce radiation at radio wavelengths, and astronomers were busily cataloguing these radio signals and matching them with objects visible in the night sky at the locations of the signals. Generally, these radio galaxies appeared as faint smudges suggestive of a galaxy. The 3C 273 radio signal, though, overlapped with a bright point of light. The point looked like a star that happened to lie on the path between the 3C 273 source and Earth, and at first, that is what Schmidt thought it was.


But then he measured its spectra – how the light is split into its constituent colors – a basic piece of information that reveals an object's chemical composition and its distance. Spectra make a pattern of vertical lines, each glowing at specific wavelengths. 3C 273 had a pattern unlike any he had seen before. Normally,  it would be easy to identify the bright lines that represent a star's hydrogen gas. But in this case the spectrum was all over the place, and no one could figure out what it was. If it was a star, it was a strange one.


Schmidt started to write a paper describing the puzzling results. "While I was writing it, I looked at the spectrum again and suddenly I realised there was something regular about it," he would recall at a symposium commemorating the 50th anniversary of his discovery.

Because the Universe is expanding, objects that are further away from us are moving much faster than nearby objects. So by measuring a redshift, astronomers can calculate an object's speed and thus its distance.


But the redshift that Schmidt measured was much bigger than what anyone would expect for a star. "It was a stunning discovery because stars shouldn't do that," Schmidt said. The Milky Way is only about 100,000 light years across, while 3C 273 turned out to be two billion light years away – clearly much too far away to be one of our galaxy's stars.


To shine as bright as one from such a distance, 3C 273 has to be producing prodigious amounts of energy. But how? In 1969, Donald Lynden-Bell, an astronomer now at the University of Cambridge, had an idea: supermassive black holes. Centers of galaxies hosting supermassive black holes that devour gas and dust. Roughly 10% of all galaxies have some activity at their centres. They come in different flavours, producing radiation at various wavelengths. Some are stronger in ultraviolet, others produce more X-rays, radio waves, or far infrared. Quasars, which are seen in about 1% of galaxies, are the brightest of the bunch.

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Einstein Ring: Dwarf Dark Galaxy Hidden in ALMA Gravitational Lens Image

Einstein Ring: Dwarf Dark Galaxy Hidden in ALMA Gravitational Lens Image | Amazing Science | Scoop.it

Subtle distortions hidden in ALMA’s stunning image of the gravitational lens SDP.81 are telltale signs that a dwarf dark galaxy is lurking in the halo of a much larger galaxy nearly 4 billion light-years away. This discovery paves the way for ALMA to find many more such objects and could help astronomers address important questions on the nature of dark matter.

In 2014, as part of ALMA’s Long Baseline Campaign, astronomers studied a variety of astronomical objects to test the telescope's new, high-resolution capabilities. One of these experimental images was that of an Einstein ring, which was produced by the gravity of a massive foreground galaxy bending the light emitted by another galaxy nearly 12 billion light-years away.

This phenomenon, called gravitational lensing, was predicted by Einstein’s general theory of relativity and it offers a powerful tool for studying galaxies that are otherwise too distant to observe. It also sheds light on the properties of the nearby lensing galaxy because of the way its gravity distorts and focuses light from more distant objects.

In a new paper accepted for publication in the Astrophysical Journal, astronomer Yashar Hezaveh at Stanford University in California and his team explain how detailed analysis of this widely publicized image uncovered signs of a hidden dwarf dark galaxy in the halo of the more nearby galaxy.

"We can find these invisible objects in the same way that you can see rain droplets on a window. You know they are there because they distort the image of the background objects,” explained Hezaveh. In the case of a rain drop, the image distortions are caused by refraction. In this image, similar distortions are generated by the gravitational influence of dark matter.

Current theories suggest that dark matter, which makes up about 80 percent of the mass of the Universe, is made of as-yet-unidentified particles that don’t interact with visible light or other forms of electromagnetic radiation. Dark matter does, however, have appreciable mass, so it can be identified by its gravitational influence.

For their analysis, the researchers harnessed thousands of computers working in parallel for many weeks, including the National Science Foundation's most powerful supercomputer, Blue Waters, to search for subtle anomalies that had a consistent and measurable counterpart in each "band" of radio data. From these combined computations, the researchers were able to piece together an unprecedented understanding of the lensing galaxy’s halo, the diffuse and predominantly star-free region around the galaxy, and discovered a distinctive clump less than one-thousandth the mass of the Milky Way.

Because of its relationship to the larger galaxy, estimated mass, and lack of an optical counterpart, the astronomers believe this gravitational anomaly may be caused by an extremely faint, dark-matter dominated satellite of the lensing galaxy. According to theoretical predictions, most galaxies should be brimming with similar dwarf galaxies and other companion objects. Detecting them, however, has proven challenging. Even around our own Milky Way, astronomers can identify only 40 or so of the thousands of satellite objects that are predicted to be present.

"This discrepancy between observed satellites and predicted abundances has been a major problem in cosmology for nearly two decades, even called a 'crisis' by some researchers," said Neal Dalal of the University of Illinois, a member of the team. "If these dwarf objects are dominated by dark matter, this could explain the discrepancy while offering new insights into the true nature of dark matter," he added.

Computer models of the evolution of the Universe indicate that by measuring the “clumpiness” of dark matter, it’s possible to measure its temperature. So by counting the number of small dark matter clumps around distant galaxies, astronomers can infer the temperature of dark matter, which has an important bearing on the smoothness of our Universe.

"If these halo objects are simply not there," notes co-author Daniel Marrone of the University of Arizona, "then our current dark matter model cannot be correct and we will have to modify what we think we understand about dark matter particles." 

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Measurement of Universe's expansion rate creates cosmological puzzle

Measurement of Universe's expansion rate creates cosmological puzzle | Amazing Science | Scoop.it

The most precise measurement ever made of the current rate of expansion of the Universe has produced a value that appears incompatible with measurements of radiation left over from the Big Bang1. If the findings are confirmed by independent techniques, the laws of cosmology might have to be rewritten.

 

 

This might even mean that dark energy — the unknown force that is thought to be responsible for the observed acceleration of the expansion of the Universe — has increased in strength since the dawn of time. “I think that there is something in the standard cosmological model that we don't understand,” says astrophysicist Adam Riess, a physicist at Johns Hopkins University in Baltimore, Maryland, who co-discovered dark energy in 1998 and led the latest study.

 

Kevork Abazajian, a cosmologist at the University of California, Irvine, who was not involved in the study, says that the results have the potential of “becoming transformational in cosmology”.

 

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Possible signature of dark matter annihilation detected

Possible signature of dark matter annihilation detected | Amazing Science | Scoop.it

We live in a dramatic epoch of astrophysics. Breakthrough discoveries like exoplanets, gravitational waves from merging black holes, or cosmic acceleration seem to arrive every decade, or even more often. But perhaps no discovery was more unexpected, mysterious, and challenging to our grasp of the "known universe" than the recognition that the vast majority of matter in the universe cannot be directly seen. This matter is dubbed "dark matter," and its nature is unknown. According to the latest results from the Planck satellite, a mere 4.9% of the universe is made of ordinary matter (that is, matter composed of atoms or their constituents). The rest is dark matter, and it has been firmly detected via its gravitational influence on stars and other normal matter. Dark energy is a separate constituent.

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Astronomers see unprecedented detail of inner portion of protoplanetary disk

Astronomers see unprecedented detail of inner portion of protoplanetary disk | Amazing Science | Scoop.it
Astronomers have discovered details of the inner, thickest portion of a dusty disk surrounding a young star and provided new insight on the earliest stages of planet formation.

 

New images of a young star made with the Karl G. Jansky Very Large Array (VLA) reveal what scientists think may be the very earliest stages in the formation of planets. The scientists used the VLA to see unprecedented detail of the inner portion of a dusty disk surrounding the star, some 450 light-years from Earth.

 

The star and its disk were studied in 2014 with the Atacama Large Millimeter/submillimeter Array (ALMA), which produced what astronomers then called the best image ever of planet formation in progress. The ALMA image showed gaps in the disk, presumably caused by planet-like bodies sweeping out the dust along their orbits. This image, showing in real life what theorists had proposed for years, was surprising, however, because the star, called HL Tau, is only about a million years old -- very young by stellar standards.

 

The ALMA image showed details of the system in the outer portions of the disk, but in the inner portions of the disk, nearest to the young star, the thicker dust is opaque to the short radio wavelengths received by ALMA. To study this region, astronomers turned to the VLA, which receives longer wavelengths. Their VLA images show that region better than any previous studies.

 

The new VLA images revealed a distinct clump of dust in the inner region of the disk. The clump, the scientists said, contains roughly 3 to 8 times the mass of the Earth.

"We believe this clump of dust represents the earliest stage in the formation of protoplanets, and this is the first time we've seen that stage," said Thomas Henning, of the Max Planck Institute for Astronomy (MPIA).

 

"This is an important discovery, because we have not yet been able to observe most stages in the process of planet formation," said Carlos Carrasco-Gonzalez from the Institute of Radio Astronomy and Astrophysics (IRyA) of the National Autonomous University of Mexico (UNAM). "This is quite different from the case of star formation, where, in different objects, we have seen stars in different stages of their life cycle. With planets, we haven't been so fortunate, so getting a look at this very early stage in planet formation is extremely valuable," he added.

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Black Holes and Black Hole Tech. How far have we progressed?

Black Holes and Black Hole Tech. How far have we progressed? | Amazing Science | Scoop.it
In celebration of the detection of gravitational waves, Stephen Wolfram looks forward and discusses what technology black holes could make possible.
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Winds from Hell: Fastest winds ever have been discovered near a supermassive black hole

Winds from Hell: Fastest winds ever have been discovered near a supermassive black hole | Amazing Science | Scoop.it

The fastest winds ever seen at ultraviolet wavelengths have been discovered near a supermassive black hole. “This new ultrafast wind surprised us when it appeared at ultraviolet wavelengths, indicating it is racing away from the ravenous black hole at unprecedented speeds—almost like a bat out of hell,” says William Nielsen (Niel) Brandt, professor of astronomy and astrophysics and a professor of physics at Penn State. “We’re talking wind speeds of more than 200 million miles an hour, equivalent to a category 77 hurricane,” says Jesse Rogerson, who led the research as part of his efforts toward earning a PhD in the physics and astronomy department at York University in Canada.

 

The ultraviolet-wavelength winds are coming from the black hole’s quasar—the disk of hot gas that surrounds the black hole. Quasars form around supermassive black holes at the centers of massive galaxies. Quasars are bigger than Earth’s orbit around the Sun and hotter than the surface of the Sun, generating enough light to be seen across the observable universe. “An exciting discovery in recent years has been the realization that ultraviolet winds from quasars can both appear and disappear when viewed from Earth, depending on various conditions surrounding the black hole,” Brandt says.

 

“Black holes can have a mass that is billions of times larger than the Sun, mostly because they are messy eaters in a way, capturing any material that ventures too close,” says Patrick Hall, associate professor at York University. “But as matter spirals toward a black hole, some of it is blown away by the heat and light of the quasar. These are the winds that we are detecting.”

 

The researchers used data from the Sloan Digital Sky Survey (SDSS) to identify new outflows from quasars. After spotting about 300 examples, they selected about 100 for further exploration, collecting data with the Gemini Observatory’s twin telescopes in Hawaii and Chile. Much of the research is aimed at better understanding outflows from quasars and why they happen. “Quasar winds play an important role in galaxy formation,” Rogerson says.

 

“When galaxies form, these winds fling material outwards and deter the creation of stars. If such winds didn’t exist or were less powerful, we would see far more stars in big galaxies than we actually do. Hubble Space Telescope images of galaxies would look much different if quasar winds did not exist.”

 

The study is published in the Monthly Notices of the Royal Astronomical Society.

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Revealing the Nature of Dark Matter

Dr. Dan Hooper, a Theoretical Astrophysicist at Fermilab, explores the current status of the dark matter search and some new thoughts on the nature of this mystery.

A signal of gamma rays has been observed from the center of the Milky Way, and it may be the breakthrough that we have long been waiting for. If these gamma-rays are in fact being produced by the interactions of dark matter particles, they promise to reveal much about this elusive substance, and may be a major step toward identifying of the underlying nature of our universe's dark matter.
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Mysterious cosmic radio bursts found to repeat

Mysterious cosmic radio bursts found to repeat | Amazing Science | Scoop.it

Astronomers for the first time have detected repeating short bursts of radio waves from an enigmatic source that is likely located well beyond the edge of our Milky Way galaxy. The findings indicate that these "fast radio bursts" come from an extremely powerful object which occasionally produces multiple bursts in under a minute.

 

Prior to this discovery, reported in Nature, all previously detected fast radio bursts (FRBs) have appeared to be one-off events. Because of that, most theories about the origin of these mysterious pulses have involved cataclysmic incidents that destroy their source - a star exploding in a supernova, for example, or a neutron star collapsing into a black hole. The new finding, however, shows that at least some FRBs have other origins.

FRBs, which last just a few thousandths of a second, have puzzled scientists since they were first reported nearly a decade ago. Despite extensive follow-up efforts, astronomers until now have searched in vain for repeat bursts.

 

That changed last November 5th, when McGill University PhD student Paul Scholz was sifting through results from observations performed with the Arecibo radio telescope in Puerto Rico - the world's largest radio telescope. The new data, gathered in May and June and run through a supercomputer at the McGill High Performance Computing Centre, showed several bursts with properties consistent with those of an FRB detected in 2012.

 

The repeat signals were surprising - and "very exciting," Scholz says. "I knew immediately that the discovery would be extremely important in the study of FRBs." As his office mates gathered around his computer screen, Scholz pored over the remaining output from specialized software used to search for pulsars and radio bursts. He found that there were a total of 10 new bursts.

 

The finding suggests that these bursts must have come from a very exotic object, such as a rotating neutron star having unprecedented power that enables the emission of extremely bright pulses, the researchers say. It is also possible that the finding represents the first discovery of a sub-class of the cosmic fast-radio-burst population.


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Pulsar Web Could Detect Low-Frequency Gravitational Waves

Pulsar Web Could Detect Low-Frequency Gravitational Waves | Amazing Science | Scoop.it
Monitoring a vast network of rapidly spinning pulsars is key to finding very-low-frequency gravitational waves, researchers say.


Pulsars emit beams of radio waves, some of which sweep across Earth once every rotation. Astronomers detect this as a rapid pulse of radio emission. Most pulsars rotate several times a second. But some, called millisecond pulsars, rotate hundreds of times faster.


"Millisecond pulsars have extremely predictable arrival times, and our instruments are able to measure them to within a ten-millionth of a second," said Maura McLaughlin, a radio astronomer at West Virginia University in Morgantown and member of the NANOGrav team. "Because of that, we can use them to detect incredibly small shifts in Earth's position."


But astrophysicists at JPL and Caltech caution that detecting faint gravitational waves would likely require more than a few pulsars. "We're like a spider at the center of a web," said Michele Vallisneri, another member of the JPL/Caltech research group. "The more strands we have in our web of pulsars, the more likely we are to sense when a gravitational wave passes by."


Vallisneri said accomplishing this feat will require international collaboration. "NANOGrav is currently monitoring 54 pulsars, but we can only see some of the southern hemisphere. We will need to work closely with our colleagues in Europe and Australia in order to get the all-sky coverage this search requires."


The feasibility of this approach was recently called into question when a group of Australian pulsar researchers reported that they were unable to detect such signals when analyzing a set of pulsars with the most precise timing measurements. After studying this result, the NANOGrav team determined that the reported non-detection was not a surprise, and resulted from the combination of optimistic gravitational wave models and analysis of too few pulsars. Theirone-page response was released recently via the arXiv electronic print service.


Despite the technical challenges, Taylor is confident their team is on the right track. "Gravitational waves are washing over Earth all the time," Taylor said. "Given the number of pulsars being observed by NANOGrav and other international teams, we expect to have clear and convincing evidence of low-frequency gravitational waves within the next decade."


NANOGrav is a collaboration of over 60 scientists at more than a dozen institutions in the United States and Canada. The group uses radio pulsar timing observations acquired at NRAO's Green Bank Telescope in West Virginia and at Arecibo Radio Observatory in Puerto Rico to search for ripples in the fabric of spacetime. In 2015, NANOGrav was awarded $14.5 million by the National Science Foundation to create and operate a Physics Frontiers Center.


"With the recent detection of gravitational waves by LIGO, the outstanding work of the NANOGrav collaboration is particularly relevant and timely," said Pedro Marronetti, National Science Foundation program director for gravitational wave research. "This NSF-funded Physics Frontier Center is poised to complement LIGO observations, extending the window of gravitational wave detection to very low frequencies."

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First biological signature of a supernova in magnetotactic bacteria

First biological signature of a supernova in magnetotactic bacteria | Amazing Science | Scoop.it

In fossil remnants of iron-loving bacteria, researchers of the Cluster of Excellence Origin and Structure of the Universe at the Technische Universitaet Muenchen (TUM), found a radioactive iron isotope that they trace back to a supernova in our cosmic neighborhood. This is the first proven biological signature of a starburst on our Earth. The age determination of the deep-drill core from the Pacific Ocean showed that the supernova must have occurred about 2.2 million years ago, roughly around the time when the modern human developed.


Most of the chemical elements have their origin in core collapse supernovae. When a star ends its life in a gigantic starburst, it throws most of its mass into space. The radioactive iron isotope Fe-60 is produced almost exclusively in such supernovae. Because its half-life of 2.62 million years is short compared to the age of our solar system, no supernova iron should be present on Earth. Therefore, any discovery of Fe-60 on Earth would indicate a supernova in our cosmic neighborhood. In the year 2004, Fe-60 was discovered on Earth for the first time in a ferromanganese crust obtained from the floor of the equatorial Pacific Ocean. Its geological dating puts the event around 2.2 million years ago.


So-called magnetotactic bacteria live within the sediments of Earth's oceans, close to the water-sediment interface. They make within their cells hundreds of tiny crystals of magnetite (Fe3O4), each approximately 80 nanometers in diameter. The magnetotactic bacteria obtain the iron from atmospheric dust that enters the ocean. Nuclear astrophysicist Shawn Bishop from the Technische Universitaet Muenchen conjectured, therefore, that Fe-60 should also reside within those magnetite crystals produced by magnetotactic bacteria extant at the time of the supernova interaction with our planet. These bacterially produced crystals, when found in sediments long after their host bacteria have died, are called "magnetofossils."


Shawn Bishop and his colleagues analyzed parts of a Pacific Ocean sediment core obtained from the Ocean Drilling Program, dating between about 1.7 million and 3.3 million years ago. They took sediment samples corresponding to intervals of about 100,000 years and treated them chemically to selectively dissolve the magnetofossils -- thereby extracting any Fe-60 they might contain.


Finally, using the ultra sensitive accelerator mass spectrometry system at the Maier Leibnitz Laboratory in Garching, Munich, they found a tantalizing hint of Iron-60 atoms occurring around 2.2 million years ago, which matches the expected time from the ferromanganese study. "It seems reasonable to suppose that the apparent signal of Fe-60 could be remains of magnetite chains formed by bacteria on the sea floor as a starburst showered on them from the atmosphere," Shawn Bishop says. He and his team are now preparing to analyze a second sediment drill core, containing upwards of 10 times the amount of material as the first drill core, to see if it also holds the Fe-60 signal and, if it does, to map out the shape of the signal as a function of time.

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Three new gravitational wave projects unveiled in China

Three new gravitational wave projects unveiled in China | Amazing Science | Scoop.it
Chinese scientists have unveiled three separate projects to investigate gravitational waves, state media said Wednesday, days after earthshaking US discoveries that confirmed Einstein's century-old predictions.


Space officials said such research would give China—which has an ambitious, military-run, multi-billion-dollar space programme that Beijing sees as symbolising the country's progress—an opportunity to become a "world leader" in the field.


Gravitational waves are direct evidence of ripples in the fabric of space-time, and their first-ever observation was announced by US scientists last week. The Chinese Academy of Sciences (CAS) rolled out a proposal for a space-based gravitational wave detection project, the official Xinhua news agency reported.


The proposed Taiji programme, named after the "supreme ultimate" of Chinese philosophy symbolised by the yin-yang sign, would send satellites of its own into orbit or share equipment with the European Space Agency's eLISA initiative.


Separately, Sun Yat-sen University in Guangzhou also proposed to launch satellites into space, while the Institute of High Energy Physics at CAS suggested a land-based scheme in Tibet. All three projects have yet to obtain government approval, state media said.

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Galaxy Clusters Reveal New Dark Matter Insights

Galaxy Clusters Reveal New Dark Matter Insights | Amazing Science | Scoop.it
Dark matter is a mysterious cosmic phenomenon that accounts for 27 percent of all matter and energy. Though dark matter is all around us, we cannot see it or feel it. But scientists can infer the presence of dark matter by looking at how normal matter behaves around it.

Galaxy clusters, which consist of thousands of galaxies, are important for exploring dark matter because they reside in a region where such matter is much denser than average. Scientists believe that the heavier a cluster is, the more dark matter it has in its environment. But new research suggests the connection is more complicated than that.

"Galaxy clusters are like the large cities of our universe. In the same way that you can look at the lights of a city at night from a plane and infer its size, these clusters give us a sense of the distribution of the dark matter that we can't see," said Hironao Miyatake at NASA's Jet Propulsion Laboratory, Pasadena, California.

A new study in Physical Review Letters, led by Miyatake, suggests that the internal structure of a galaxy cluster is linked to the dark matter environment surrounding it. This is the first time that a property besides the mass of a cluster has been shown to be associated with surrounding dark matter.

Researchers studied approximately 9,000 galaxy clusters from the Sloan Digital Sky Survey DR8 galaxy catalog, and divided them into two groups by their internal structures: one in which the individual galaxies within clusters were more spread out, and one in which they were closely packed together. The scientists used a technique called gravitational lensing -- looking at how the gravity of clusters bends light from other objects -- to confirm that both groups had similar masses.

But when the researchers compared the two groups, they found an important difference in the distribution of galaxy clusters. Normally, galaxy clusters are separated from other clusters by 100 million light-years on average. But for the group of clusters with closely packed galaxies, there were fewer neighboring clusters at this distance than for the sparser clusters. In other words, the surrounding dark-matter environment determines how packed a cluster is with galaxies.

"This difference is a result of the different dark-matter environments in which the groups of clusters formed. Our results indicate that the connection between a galaxy cluster and surrounding dark matter is not characterized solely by cluster mass, but also its formation history," Miyatake said.

Study co-author David Spergel, professor of astronomy at Princeton University in New Jersey, added, "Previous observational studies had shown that the cluster's mass is the most important factor in determining its global properties. Our work has shown that 'age matters': Younger clusters live in different large-scale dark-matter environments than older clusters."

The results are in line with predictions from the leading theory about the origins of our universe. After an event called cosmic inflation, a period of less than a trillionth of a second after the big bang, there were small changes in the energy of space called quantum fluctuations. These changes then triggered a non-uniform distribution of matter. Scientists say the galaxy clusters we see today have resulted from fluctuations in the density of matter in the early universe.

"The connection between the internal structure of galaxy clusters and the distribution of surrounding dark matter is a consequence of the nature of the initial density fluctuations established before the universe was even one second old," Miyatake said.

Researchers will continue to explore these connections.

"Galaxy clusters are remarkable windows into the mysteries of the universe. By studying them, we can learn more about the evolution of large-scale structure of the universe, and its early history, as well as dark matter and dark energy," Miyatake said.
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