From University of Vienna via Science Alert: “Astronomers Have Detected a Previously Unnoticed ‘River of Stars’ Flowing Past Earth”

From University of Vienna

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Science Alert

(MoazAqeelChishti/CC BY-SA 4.0)

19 FEB 2019
MICHELLE STARR

If you live in the Southern Hemisphere, next time you get the opportunity, go outside and look at the night sky. Most of that celestial plain is covered in a star cluster that’s been torn apart by galactic tidal forces, and is now flowing past us as a giant river of over 4,000 stars.

Although it may be in plain sight, it’s only just been discovered, revealed by the Gaia data that facilitated the most accurate 3D-map of the galaxy yet.

ESA/GAIA satellite

ESA GAIA Release 2 map

What makes this stellar stream exciting is its proximity to Earth. It’s just 100 parsecs (326 light-years) away, offering an unprecedented opportunity to peer into the dynamics of a disrupted cluster.

“Identifying nearby disc streams is like looking for the proverbial needle in a haystack. Astronomers have been looking at, and through, this new stream for a long time, as it covers most of the night sky, but only now realise it is there, and it is huge, and shockingly close to the Sun,” said astrophysicist João Alves of the University of Vienna.

“Finding things close to home is very useful, it means they are not too faint nor too blurred for further detailed exploration, as astronomers dream.”

Stars tend to form in clusters in stellar nurseries, but they don’t usually stay clustered for long – maybe up to a few hundred thousand years.

Stellar Nursery NASA/Spitzer Image credit NASA/JPL-Caltech W. Reach (SSC-Caltech)

It takes a lot of mass to build up enough gravity to hold a cluster together – even small galaxies orbiting the Milky Way can be torn apart by its tidal forces and end up stretched out into long rivers of stars orbiting the galactic core.

These can be hard to see, as Alves said, because we need quite a bit of information to be able to link the stars to each other. But this is what Gaia provided. Not only has it given accurate locations in 3D space for stars, it has given us their velocities, and excited astronomers have been using this data to identify stellar streams.

So when University of Vienna astronomers noticed a group of stars moving together, they took a closer look. They found the group bore the signatures of a stellar cluster that had been torn apart, and was now a stellar stream.

The river of stars in the southern sky. ESA/GAIA (Gaia DR2 skymap)

Due to Gaia sensitivity limitations, they were only able to analyse 200 stars in detail, but based on the interactions between the stars, the team extrapolated that the stream should contain at least 4,000 stars.

This star river is sizeable, about 200 parsecs (652 light-years) wide and 400 parsecs (1,305 light-years) long. These dimensions also help estimate its age.

The stream, the team argue, is not dissimilar to the open cluster the Hyades. At around 625 million years old, the Hyades is showing evidence of a tidal tail; it’s in the early stages of being disrupted.

Hence, the researchers think this stream is older than the Hyades. Based on this comparison, and a set of stellar isochrone data (used to calculate the age of stars), the team has put the age of the stream at about 1 billion years.

That means it’s completed around four full orbits of the Milky Way (the Sun takes about 230 million years to orbit the galactic core), which is sufficient time for it have stretched out into its attenuated shape.

“As soon as we investigated this particular group of stars in more detail, we knew that we had found what we were looking for: A coeval, stream-like structure, stretching for hundreds of parsecs across a third of the entire sky,” said astronomer Verena Fürnkranz [Astronomy and Astrophysics].

Most Milky Way stellar streams identified to date are actually orbiting outside the galactic disc, and are much larger – but this stream’s location inside the disc could make it a valuable tool. For example, it could be used to help constrain the Milky Way’s mass distribution.

It could also help shed light on how galaxies get stars, and test the Milky Way’s gravitational field, the researchers said.

With the help of the Gaia data, they plan to look for more such streams in the night sky, hiding in plain sight.

See the full article here .

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The University of Vienna (German: Universität Wien) is a public university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is one of the oldest universities in the German-speaking world. With its long and rich history, the University of Vienna has developed into one of the largest universities in Europe, and also one of the most renowned, especially in the Humanities. It is associated with 15 Nobel prize winners and has been the academic home to a large number of scholars of historical as well as of academic importance.

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From Science Alert: “Astronomers Detect a Stellar Flare 10 Billion Times Brighter Than Ones From Our Sun”

From Science Alert

15 FEB 2019
MICHELLE STARR

(Rogelio Bernal Andreo, CC BY-SA 3.0)

Our Sun can let out some solar flare rip-snorters from time to time, but it’s actually pretty quiet when compared to some other stars out there. Particularly, it seems, turbulent young stars. And astronomers have just caught one belching out a real corker.

It’s called JW 566, a young star about 389 parsecs (1,269 light-years) away in the Orion Nebula. In November 2016, it erupted into a flare 10 billion times brighter than those of the Sun.

“The event,” the researchers wrote in their paper [The Astrophysical Journal], “may be the most luminous known flare associated with a young stellar object and is also the first coronal flare discovered at submillimetre wavelengths.”

JW 566 is what is known as a T Tauri star, a variable star (that is, one whose luminosity varies) less than 10 million years old, and going through a period of tempestuous growth, before its massive enough for the ignition of hydrogen fusion in its core.

The James Clerk Maxwell Telescope at the Mauna Kea Observatory in Hawaii has an instrument called SCUBA-2.

The 45 tonne SCUBA-2 instrument mounted on the James Clerk Maxwell Telescope, Photo credit Joint Astronomy Centre

This is a 10,000 pixel bolometer camera, supercooled to -273 degrees Celsius (-459.5 degrees Fahrenheit), incredibly sensitive to submillimetre wavelengths.

East Asia Observatory James Clerk Maxwell telescope, Mauna Kea, Hawaii, USA,4,207 m (13,802 ft) above sea level

HECK. (East Asian Observatory)

This instrument managed to capture the flare, even though it was extremely short-lived – bursting and dissipating in a matter of hours.

“Using the JCMT, we study the birth of nearby stars as a means of understanding the history of our very own Solar System,” said astronomer Steve Mairs of East Asian Observatory.

“Observing flares around the youngest stars is new territory and it is giving us key insights into the physical conditions of these systems. This is one of the ways we are working toward answering people’s most enduring questions about space, time, and the Universe that surrounds us.”

The researchers believe the star is actively accreting matter from the disc of dust surrounding it, and the flare was caused by a disruption in the magnetic field that is funnelling the material into the star.

The reconnection of the magnetic field briefly energises non-thermal particles; and this appears as a stellar flare. Giant flares from young stars, such as this one, can help understand the dynamics of this magnetic disruption and reconnection.

The team will be continuing to monitor the star as part of the JCMT Transient Survey, in the hopes of catching it in the act of another tremendous belch.

See the full article here .

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From University of Glasgow via Science Alert: “For The First Time Ever, Scientists Have Produced Fractal Light From Lasers”

From University of Glasgow

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Science Alert

2 FEB 2019
DAVID NIELD

Fractal light created by laser. (Wits University)

Two decades after the hypothetical prediction that it should be possible, scientists have been able to produce fractal light from a laser.

Not only that, they’ve shown the fractal light could be created in 3D rather than just 2D.

Displaying one of nature’s most common patterns from a very human-made technology could open up opportunities in all kinds of communication and imaging fields, the team behind the breakthrough says.

You don’t have to look for long to see these geometrical masterpieces in nature – they’re everywhere from snowflakes to salt flats – but it turns out that discovering them in a beam of laser light requires some very carefully calibrated observations.

Fractal pattern cross-section. (Wits University)

“What is amazing is that, as predicted, the only requirement to demonstrate the effect is a simple laser with two polished spherical mirrors,” says one of the researchers, Johannes Courtial from the University of Glasgow in the UK.

“It was there all the time, just hard to see if you were not looking at the right place.”

“Look at the wrong place inside the laser and you see just a smeared-out blob of light,” adds another of the team, Andrew Forbes from the University of the Witwatersrand in South Africa. “Look in the right place, where the imaging happens, and you see fractals.”

That prediction that Courtial refers to published in a 1999 paper [Nature] after researchers identified certain laser manipulations that should produce fractals from the light – but this is the first time we’ve actually seen it happening.

The way it’s done is to use the way laser light cycles back and forth, bouncing between mirrors and repeating light on to itself, to mimic the repeating patterns of fractals in nature [see banner image above].

Through precise control of laser light within its spherical mirrors, scientists were able to get the light to a smaller or larger version of itself every time it returned to a point where it could be observed – resulting in fractals.

This observation point is called the common imaging plane, and it requires looking inside the optics of the laser itself, not at the resulting beam that comes out.

The laser instrument used in experiments. (Wits University)

It’s early days in terms of how this discovery might be used in the future, but the potential across imaging, networks, antenna technology and medicine is significant, according to the researchers.

Fractals tie in closely with chaos theory [Fractal Foundation] (also known as the butterfly effect), that one small change in nature can have huge and unpredictable results.

Fractals can help map out some of these complex, dynamic systems, and having our very own fractal generators might give us a better understanding of how the universe works on a bigger scale.

Further down the line, the researchers are hoping to be able to develop custom-made lasers able to produce fractal designs on demand, something that will make them even more useful to scientists and engineers.

And the new research has led to another prediction: that the 2D images created here might one day be realised in 3D as well, with hints of a fractal structure existing along another axis inside the laser.

“This is the nature of science: answering old questions inevitably results in new, more complex questions to be answered,” writes Forbes at The Conversation.

“So, although one chapter is closed, another remains completely unwritten.”

The research has been published in Physical Review A.

See the full article here .

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The University of Glasgow (Scottish Gaelic: Oilthigh Ghlaschu, Latin: Universitas Glasguensis) is the fourth oldest university in the English-speaking world and one of Scotland’s four ancient universities. It was founded in 1451. Along with the University of Edinburgh, the University was part of the Scottish Enlightenment during the 18th century. It is currently a member of Universitas 21, the international network of research universities, and the Russell Group.

In common with universities of the pre-modern era, Glasgow originally educated students primarily from wealthy backgrounds, however it became a pioneer[citation needed] in British higher education in the 19th century by also providing for the needs of students from the growing urban and commercial middle class. Glasgow University served all of these students by preparing them for professions: the law, medicine, civil service, teaching, and the church. It also trained smaller but growing numbers for careers in science and engineering.[4]

Originally located in the city’s High Street, since 1870 the main University campus has been located at Gilmorehill in the West End of the city.[5] Additionally, a number of university buildings are located elsewhere, such as the University Marine Biological Station Millport on the Island of Cumbrae in the Firth of Clyde and the Crichton Campus in Dumfries.

Alumni or former staff of the University include philosopher Francis Hutcheson, engineer James Watt, philosopher and economist Adam Smith, physicist Lord Kelvin, surgeon Joseph Lister, 1st Baron Lister, seven Nobel laureates, and two British Prime Ministers.

From Instituto de Astrofísica de Canarias – IAC via Science Alert: “Astronomers Have Made a Breathtaking Image Staring Deeper Into Space Than Ever Before”

From Instituto de Astrofísica de Canarias – IAC

via

Science Alert

25 JAN 2019
MICHELLE STARR

A few years ago, the Hubble Space Telescope did something amazing: over the course of 841 orbits and hundreds of exposures, it imaged a tiny region of space in the constellation of Fornax, peeling back the layers of time by 13 billion years, to just a few hundred million years after the Big Bang.

Image Credit: Roen Kelly

The Fornax Galaxy Cluster is one of the closest of such groupings beyond our Local Group of galaxies. This new VLT Survey Telescope image shows the central part of the cluster in great detail. At the lower-right is the elegant barred-spiral galaxy NGC 1365 and to the left the big elliptical NGC 1399. ESO. Acknowledgement: Aniello Grado and Luca Limatola.

Part of ESO’s Paranal Observatory, the VLT Survey Telescope (VISTA) observes the brilliantly clear skies above the Atacama Desert of Chile. It is the largest survey telescope in the world in visible light.
Credit: ESO/Y. Beletsky, with an elevation of 2,635 metres (8,645 ft) above sea level

It’s called the Hubble Ultra-Deep Field 2014 (HUDF), and it’s one of the most breathtaking mosaics the telescope has produced. In it, around 10,000 galaxies gleam – a feast for astronomers exploring the early Universe.

Hubble Ultra Deep Field

Now a team of astronomers has made the image even better. Over the course of three years, scientists at the Instituto de Astrofísica de Canarias (IAC) developed and applied an image processing technique designed to draw out the unseen light in the HUDF.

They called this complex technique ABYSS, and with it they have recovered the dim light from the outer edges of the largest galaxies in the image.

(The ABYSS HST Ultra Deep Imaging Project)

“What we have done,” explained IAC astrophysicist Alejandro S. Borlaff, “is to go back to the archive of the original images, directly as observed by the HST, and improve the process of combination, aiming at the best image quality not only for the more distant smaller galaxies but also for the extended regions of the largest galaxies.”

So far, the results have revealed that at least some of these galaxies are much bigger than thought, with diameters up to twice as large as previous estimates.

But the paper published by the team wasn’t for the purpose of making these discoveries, but describing how ABYSS works.

The have published the enhanced images they generated, and have plans to publish the calibration files and the ABYSS pipeline so that the community can use the tools themselves, and help develop further refinements.

The paper has been published in the journal Astronomy & Astrophysics.

See the full article here.

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The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
The Centro de Astrofísica en La Palma (CALP)
The Observatorio del Teide (OT), in Izaña (Tenerife).

These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

The IAC’s research programme includes astrophysical research and technological development projects.

The IAC is also involved in researcher training, university teaching and outreachactivities.

The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.

Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

From Science Alert: “Our Galaxy’s Supermassive Black Hole Could Be Pointing a Relativistic Jet Right at Us”

From Science Alert

22 JAN 2019
MICHELLE STARR

A black hole simulation (Bronzwaer/Davelaar/Moscibrodzka/Falcke/Radboud University)

Things are officially getting exciting. New science has just come in from the collaboration to photograph Sagittarius A*, the supermassive black hole at the centre of the Milky Way, and it’s ponying up the secrets at our galaxy’s dusty heart.

SGR A and SGR A* from Penn State and NASA/Chandra

The image below is the best picture yet of Sgr A* (don’t worry, there’s more to come from the Event Horizon Telescope), and while it may look like just a weird blob of light to you, astrophysicists studying the radio data can learn a lot from what they’re looking at – and they think they’ve identified a relativistic jet angled towards Earth.

EHT map

Because the image taken of the region is the highest resolution yet – twice as high as the previous best – the researchers were able to precisely map the properties of the light around the black hole as scattered by the cloud.

“The galactic centre is full of matter around the black hole, which acts like frosted glass that we have to look through,” astrophysicist Eduardo Ros of the Max Planck Institute for Radio Astronomy in Germany told New Scientist.

Using very long baseline interferometry to take observations at a wavelength of 3.5 millimetres (86 GHz frequency), a team of astronomers has used computer modelling to simulate what’s inside the thick cloud of plasma, dust and gas surrounding the black hole.

Above: The bottom right image shows Sgr A* as seen in the data. The top images are simulations, while the bottom left is Sgr A* with the scattering removed.
(S. Issaoun, M. Mościbrodzka, Radboud University/ M. D. Johnson, CfA)

ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

GMVA The Global VLBI Array

It revealed that Sgr A*’s radio emission comes from a smaller region than previously thought.

Most of it is coming from an area just 300 milllionth of a degree of the night sky, with a symmetrical shape. And, since black holes don’t emit detectable radiation on their own, the source is most likely one of two things.

“This may indicate that the radio emission is produced in a disk of infalling gas rather than by a radio jet,” said astrophysicist Sara Issaoun of Radboud University in The Netherlands.

“However, that would make Sgr A* an exception compared to other radio emitting black holes. The alternative could be that the radio jet is pointing almost at us.”

Active black holes are surrounded by a swirling cloud of material that’s falling into it like water down a drain. As this material is swallowed by the black hole, it emits jets of particles from its rotational poles at velocities approaching light speed.

We’re not quite sure how this happens, but astronomers believe that material from the inner part of the accretion disc is channelled towards and launched from the poles via magnetic field lines.

Since Earth is in the galactic plane, having a jet pointed in our direction would mean that the black hole is oriented quite strangely, as if it’s lying on its side. (Nearby galaxy Centaurus A, for instance, has jets shooting perpendicular to the galactic plane.)

But this orientation has been hinted at before. Last year the GRAVITY Collaboration described flares around Sgr A* consistent with something orbiting it face-on from our perspective – like looking at the Solar System from above.

This means the long-awaited picture of the shadow of a black hole will – hopefully – be breathtakingly detailed.

Meanwhile, studying data such as these help build a comprehensive picture of how these mysterious cosmic objects work.

“Understanding how black holes work … takes more than the picture of its shadow (although incredible in its own right),” Issaoun wrote on Facebook. “It takes observations at many different wavelengths (radio, X-ray, infrared etc) to piece together the entire story, so every piece counts!”

The team’s paper has been published in The Astrophysical Journal..

So “Maybe this is true after all,” said Radboud University astronomer Heino Falcke, “and we are looking at this beast from a very special vantage point.”

Hopefully, when the Event Horizon Telescope releases the first images of Sgr A*’s event horizon – something we are expecting very soon – they will reveal more. And, in case you were starting to get worried, the 1.4-millimetre wavelength (230 GHz) will reduce the light scattering by a factor of 8.

See the full article here .

See also here .

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From Science Alert: “Something Else Instead of Planet Nine Could Be Hiding in The Outer Solar System”

From Science Alert

21 JAN 2019
MICHELLE STARR

Dwarf planet Sedna, one of the detached TNOs. (NASA/JPL-Caltech)

Somewhere in the outer reaches of the Solar System, beyond the orbit of Neptune, something wonky is happening. A few objects are orbiting differently from everything else, and we don’t know why.

A popular hypothesis is that an unseen object called Planet Nine could be messing with these orbits; astronomers are avidly searching for this planet. But now physicists have come up with an alternative explanation they think is more plausible.

Instead of one big object, the orbital wobblies could be caused by the combined gravitational force of a number of smaller Kuiper Belt or trans-Neptunian objects (TNOs). That’s according to astrophysicists Antranik Sefilian of the University of Cambridge in the UK and Jihad Touma of the American University of Beirut in Lebanon.

If it sounds familiar, that’s because Sefilian and Touma are not the first to think of this idea – but their calculations are the first to explain significant features of the strange orbits of these objects, while taking into account the other eight planets in the Solar System.

A hypothesis for Planet Nine was first announced in a 2016 study [The Astronomical Journal]. Astronomers studying a dwarf planet in the Kuiper Belt noticed that several TNOs were “detached” from the strong gravitational influence of the Solar System’s gas giants, and had weird looping orbits that were different from the rest of the Kuiper Belt.

But the orbits of these six objects were also clustered together in a way that didn’t appear random; something seemed to have tugged them into that position. According to modelling, a giant, heretofore unseen planet could do so.

So far, this planet has remained elusive – not necessarily odd, since there are considerable technical challenges to seeing a dark object that far away, especially when we don’t know where it is. But its evasiveness is prompting scientists to seek alternative explanations.

“The Planet Nine hypothesis is a fascinating one, but if the hypothesised ninth planet exists, it has so far avoided detection,” Sefilian said, adding that the team wanted to see if there was a less dramatic explanation of the weird TNO orbits.

“We thought, rather than allowing for a ninth planet, and then worry about its formation and unusual orbit, why not simply account for the gravity of small objects constituting a disk beyond the orbit of Neptune and see what it does for us?”

The researchers created a computer model of the detached TNOs, as well as the planets of the Solar System (and their gravity), and a huge disc of debris past Neptune’s orbit.

By applying tweaks to elements such as the mass, eccentricity and orientation of the disc, the researchers were able to recreate the clustered looping orbits of the detached TNOs.

“If you remove Planet Nine from the model, and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs,” Sefilian said.

This solves a problem that scientists from the University of Colorado Boulder had when they first floated the collective gravity hypothesis last year. Although their calculations were able to account for the gravitational effect on the detached TNOs, they couldn’t explain why their orbits were all tilting the same way.

And there’s still another problem with both models: in order to produce the observed effect, the Kuiper Belt needs a collective gravity of at least a few Earth masses.

Current estimates, however, put the mass of the Kuiper Belt at just 4 to 10 percent of Earth’s mass.

But, according to Solar System formation models, it should be much higher; and, Sefilian notes, it’s hard to view the entirety of a debris disc around a star when you’re inside it, so it’s possible that there’s a lot more to the Kuiper Belt than we’re able to see.

“While we don’t have direct observational evidence for the disc, neither do we have it for Planet Nine, which is why we’re investigating other possibilities,” Sefilian said.

“It’s also possible that both things could be true – there could be a massive disk and a ninth planet. With the discovery of each new TNO, we gather more evidence that might help explain their behaviour.”

The team’s research is due to appear in the Astronomical Journal and you can find the pre-print on arXiv.

See the full article here .

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Weizmann Institute of Science via Science Alert: “We Just Got Lab-Made Evidence of Stephen Hawking’s Greatest Prediction About Black Holes”

Weizmann Institute of Science

via

Science Alert

21 JAN 2019
MICHELLE STARR

Scientists may have just taken a step towards experimentally proving the existence of Hawking radiation. Using an optical fibre analogue of an event horizon – a lab-created model of black hole physics – researchers from Weizmann Institute of Science in Rehovot, Israel report that they have created stimulated Hawking radiation.

Under general relativity, a black hole is inescapable. Once something travels beyond the event horizon into the heart of the black hole, there’s no return. So intense is the gravitational force of a black hole that not even light – the fastest thing in the Universe – can achieve escape velocity.

Under general relativity, therefore, a black hole emits no electromagnetic radiation. But, as a young Stephen Hawking theorised in 1974, it does emit something when you add quantum mechanics to the mix.

This theoretical electromagnetic radiation is called Hawking radiation; it resembles black body radiation, produced by the temperature of the black hole, which is inversely proportional to its mass (watch the video below to get a grasp of this neat concept).

This radiation would mean that black holes are extremely slowly and steadily evaporating, but according to the maths, this radiation is too faint to be detectable by our current instruments.

So, cue trying to recreate it in a lab using black hole analogues. These can be built from things that produce waves, such as fluid and sound waves in a special tank, from Bose-Einstein condensates, or from light contained in optical fibre.

“Hawking radiation is a much more general phenomenon than originally thought,” explained physicist Ulf Leonhardt to Physics World. “It can happen whenever event horizons are made, be it in astrophysics or for light in optical materials, water waves or ultracold atoms.”

These won’t, obviously, reproduce the gravitational effects of a black hole (a good thing for, well, us existing), but the mathematics involved is analogous to the mathematics that describe black holes under general relativity.

This time, the team’s method of choice was an optical fibre system developed by Leonhardt some years ago.

The optical fibre has micro-patterns on the inside, and acts as a conduit. When entering the fibre, light slows down just a tiny bit. To create an event horizon analogue, two differently coloured ultrafast pulses of laser light are sent down the fibre. The first interferes with the second, resulting in an event horizon effect, observable as changes in the refractive index of the fibre.

The team then used an additional light on this system, which resulted in an increase in radiation with a negative frequency. In other words, ‘negative’ light was drawing energy from the ‘event horizon’ – an indication of stimulated Hawking radiation.

While the findings were undoubtedly cool, the end goal for such research is to observe spontaneous Hawking radiation.

Stimulated emission is exactly what it sounds like – emission that requires an external electromagnetic stimulus. Meanwhile the Hawking radiation emanating from a black hole would be of the spontaneous variety, not stimulated.

There are other problems with stimulated Hawking radiation experiments; namely, they are rarely unambiguous, since it’s impossible to precisely recreate in the lab the conditions around an event horizon.

With this experiment, for example, it’s difficult to be 100 percent certain that the emission wasn’t created by an amplification of normal radiation, although Leonhardt and his team are confident that their experiment did actually produce Hawking radiation.

Either way, it’s a fascinating achievement and has landed another mystery in the team’s hands, too – they found the result was not quite as they expected.

“Our numerical calculations predict a much stronger Hawking light than we have seen,” Leonhardt told Physics World.

“We plan to investigate this next. But we are open to surprises and will remain our own worst critics.”

The research has been published in the journal Physical Review Letters.

See the full article here .

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The Weizmann Institute of Science is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

From Science Alert: “One of The Most Common Assumptions About Autism May Be a Complete Misunderstanding”

From Science Alert

8 JAN 2019
CARLY CASSELLA

(Chalabala/iStock)

Putting yourself in another person’s shoes is never easy, and for those with autism spectrum disorder (ASD), the practice is thought to be especially challenging.

But even though this neurological condition is often considered a barrier to understanding complex emotions,recent research suggests this may be nothing more than a simple misunderstanding.

For the first time, researchers have shown in a small study that adults with ASD can recognise regret and relief in others just as easily as those without the condition, and in some cases, they are even better at it.

“We have shown that, contrary to previous research that has highlighted the difficulties adults with autism experience with empathy and perspective-taking, people with autism possess previously overlooked strengths in processing emotions,” says senior author Heather Ferguson, an expert in neurolinguistics, semantics and syntax at the University of Kent.

Using state-of-the-art eye-tracking methods, the researchers analysed 48 adult participants – half with ASD and half without – as they read a story about a character who experiences either regret or relief.

In the narrative, the protagonist makes a decision that results in either a good outcome or a bad outcome, and the final sentence sums up the character’s mood explicitly, saying whether their choice left them feeling regret or relief (for instance, “… she feels happy/annoyed about her decision… “).

As predicted, when the final emotion did not match up with the rest of the story (for instance, “she bought new shoes that she loved, and she felt annoyed about her decision”), the majority of participants spent longer reading through the text. They also looked back at previous sentences more often.

There was only one plausible explanation: the readers were trying to make sense of a story that didn’t make sense.

Because they understood the protagonist’s desires and actions, most of the readers were able to predict whether the character would feel regret or relief – a psychological concept called counterfactual thinking.

Previous studies have shown that this sort of thinking can be disrupted in people with ASD, but the new findings suggest something completely different.

Instead, the results were surprisingly similar for both adults with ASD and adults without ASD. Not only were participants with ASD equally adept at recognising regret, they were actually faster at computing relief.

Together, this suggests that adults with ASD are remarkably savvy when it comes to feeling empathy and processing emotions.

“Thus, our findings reveal that adults with ASD can employ sophisticated processes to adopt someone else’s perspective, and use this in real-time as the reference for future processing,” the authors conclude.

At first, the results appear to fly in the face of previous research – and it’s a small study, so we can’t get too carried away just yet. But when taking a closer look, there is another explanation.

The authors think that the differing results may simply stem from the method.

By removing the need for participants to describe their own emotions or the emotions of others, the new research takes a more direct route to the truth.

Using eye-tracking, the authors were able to tap into a participant’s immediate, neurological response to emotional content. This is a useful technique because it completely cancels out the bias that a participant might exhibit when describing their understanding of another person’s emotional state.

The authors are therefore suggesting that adults with ASD can implicitly and correctly read another person’s emotions, they just aren’t able to accurately describe those emotions to researchers.

In other words, the past studies on counterfactual thinking may have simply been conflating expression with understanding.

“These findings suggest that the previously observed difficulty with complex counterfactual emotions may be tied specifically to difficulties with the explicit expression of emotions rather than any difficulty experiencing them implicitly at a neurocognitive level,” the authors conclude.

This study has been published in Autism Research.

See the full article here .

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From Science Alert: “Here’s Why ‘The Child of Krakatau’ Is Still Extremely Dangerous”

From Science Alert

3 JAN 2019
THOMAS GIACHETTI

(Byelikova_Oksana/iStock)

On Dec. 22 at 9:03 pm local time, a 64-hectare (158-acre) chunk of Anak Krakatau volcano, in Indonesia, slid into the ocean following an eruption. This landslide created a tsunami that struck coastal regions in Java and Sumatra, killing at least 426 people and injuring 7,202.

Satellite data and helicopter footage taken on Dec. 23 confirmed that part of the southwest sector of the volcano had collapsed into the sea. In a report on Dec. 29, Indonesia’s Center of Volcanology and Geological Hazard Mitigation said that the height of Anak Krakatau went from 338 meters (1,108 feet) above sea level to 110 meters (360 feet).

My colleagues and I published a study [Lyell Special Publications] in 2012 looking at the hazards this site posed and found that, although it was very difficult to forecast if and when Anak Krakatau would partially collapse, the characteristics of the waves produced by such event were not totally unpredictable.

Landslide-triggered

Although most tsunamis have a seismic origin (for example, the Sumatra, Indonesia one in 2004 and at Tohoku, Japan in 2011), they may also be triggered by phenomena related to large volcanic eruptions.

Tsunamis caused by volcanoes can be triggered by submarine explosions or by large pyroclastic flows – a hot mix of volcanic gases, ash and blocks travelling at tens of miles per hour – if they enter in a body of water.

A simulation of an Anak Krakatau volcanic event shows waves of 15 meters or more locally (in red). (Giachetti et al. 2012)

Another cause is when a large crater forms due to the collapse of the roof of a magma chamber – a large reservoir of partially molten rock beneath the surface of the Earth – following an eruption.

At Anak Krakatau, a large, rapidly sliding mass that struck the water led to the tsunami. These types of events are usually difficult to predict as most of the sliding mass is below water level.

These volcanic landslides can lead to major tsunamis. Landslide-triggered tsunamis similar to what happened at Anak Krakatau occurred in December 2002 when 17 millions cubic meters (600 millions cubic feet) of volcanic material from Stromboli volcano, in Italy, triggered a 8-meter-high wave.

More recently in June 2017, a 100-meter-high wave was triggered by a 45-million-cubic-meter (1.6-billion cubic-feet) landslide in Karrat Fjord, in Greenland, causing a sudden surge of seawater that wreaked havoc and killed four people in the fishing village of Nuugaatsiaq located about 20 km (12.5 miles) away from the collapse.

These two tsunamis had few fatalities as they occurred either in relatively isolated locations (Karrat Fjord) or during a period of no tourist activity (Stromboli). This was obviously not the case at Anak Krakatau on Dec. 22.

Satellite pictures taken before (left) and after (right) the Anak Krakatau eruption. (Geospatial Information Authority of Japan/CC BY-NC-ND)

Child of Krakatau

This part of the world is well-experienced with destructive volcanoes. In August 26-28, 1883, Krakatau volcano experienced one of the largest volcanic eruptions ever recorded in human history, generating 15 meter (50 feet) tsunami waves and causing more than 35,000 casualties along the coasts of the Sunda Strait in Indonesia.

Nearly 45 years after this 1883 cataclysmal eruption, Anak Krakatau (“Child of Krakatau” in Indonesian) emerged from the sea in the same location as the former Krakatau, and grew to reach about 338 meters (1,108 feet), its maximum height on Dec. 22, 2018.

Many tsunamis were produced during the 1883 eruption. How they were generated is still debated by volcanologists, as several volcanic processes may have acted successively or together.

I worked on this very problem in 2011 with my colleagues Raphaël Paris and Karim Kelfoun from the Université Clermont Auvergne in France, and Budianto Ontowirjo from the Tanri Abeng University in Indonesia.

However, the short time left in my postdoctoral fellowship had me shift direction away from the 19th-century explosion to focus on Anak Krakatau. In 2012, we published a paper entitled “Tsunami Hazard Related to a Flank Collapse of Anak Krakatau Volcano, Sunda Strait, Indonesia” [Link is above].

This study started with the observation that Anak Krakatau was partly built on a steep wall of the crater resulting from the 1883 eruption of Krakatau. We thus asked ourselves “what if part of this volcano collapses into the sea?”

To tackle this question, we numerically simulated a sudden southwestwards destabilization of a large part of the Anak Krakatau volcano, and the subsequent tsunami formation and propagation. We showed results projecting the time of arrival and the amplitude of the waves produced, both in the Sunda Strait and on the coasts of Java and Sumatra.

When modeling landslide-triggered tsunamis, several assumptions need to be made concerning the volume and shape of the landslide, the way it collapses (in one go versus in several failures), or the way it propagates. In that study, we envisioned a somewhat “worst-case scenario” with a volume of 0.28 cubic kilometers of collapsed volcanic material – the equivalent of about 270 Empire State buildings.

We predicted that all the coasts around the Sunda Strait could potentially be affected by waves of more than 1 meter less than 1 hour after the event.

Unfortunately, it seems that our findings were not that far to what happened on Dec. 22: The observed time of arrival and amplitude of the waves were in the range of our simulation, and oceanographer Stephan Grilli and colleagues estimated that 0.2 cubic kilometers of land actually collapsed.

Since the landslide occurred, there have been continuous Surtseyan eruptions. These involve explosive interactions between the magma of the volcano and the surrounding water, which is reshaping Anak Krakatau as it continues to slowly slide to the southwest.

Indonesia remains on high alert as officials warn of potentially more tsunamis. As people wait, it’s worth returning to studies that have looked at the potential hazards caused by volcanoes.

See the full article here .

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From Science Alert: “Japan Discovered a Rare-Earth Mineral Deposit That Can Supply The World For Centuries”

From Science Alert

30 DEC 2018
JEREMY BERKE

Earlier this year, researchers found a deposit of rare-earth minerals off the coast of Japan that could supply the world for centuries, according to a study.

(greenp/iStock)

The study, published in the journal Nature in April 2018, says the deposit contains 16 million tons of the valuable metals.

Rare-earth minerals are used in everything from smartphone batteries to electric vehicles. By definition, these minerals contain one or more of 17 metallic rare-earth elements (for those familiar with the periodic table, those are on the second row from the bottom).

These elements are actually plentiful in layers of the Earth’s crust, but are typically widely dispersed. Because of that, it is rare to find any substantial amount of the elements clumped together as extractable minerals, according to the USGS.

Currently, there are only a few economically viable areas where they can be mined and they’re generally expensive to extract.

China has tightly controlled much of the world’s supply of these minerals for decades. That has forced Japan – a major electronics manufacturer – to rely on prices dictated by their neighbour.

A new finding that could change the global economy

The recently discovered deposit is enough to “supply these metals on a semi-infinite basis to the world,” the study’s authors wrote in the paper.

There’s enough yttrium to meet the global demand for 780 years, dysprosium for 730 years, europium for 620 years, and terbium for 420 years.

The cache lies off of Minamitori Island, about 1,150 miles (1,850 km) southeast of Tokyo. It’s within Japan’s exclusive economic zone, so the island nation has the sole rights to the resources there.

“This is a game changer for Japan,” Jack Lifton, a founding principal of a market-research firm called Technology Metals Research, told The Wall Street Journal.

“The race to develop these resources is well underway.”

Japan started seeking its own rare-earth mineral deposits after China withheld shipments of the substances amid a dispute over islands that both countries claim as their own, Reuters reported in 2014.

Previously, China reduced its export quotas of rare earth minerals in 2010, pushing prices up as much as 10 percent, The Journal reports. China was forced to start exporting more of the minerals again after the dispute was taken up at the World Trade Organisation.

Rare-earth minerals can be formed by volcanic activity, but many of the minerals on our planet were formed initially by supernova explosions before Earth came into existence.

When Earth was formed, the minerals were incorporated into the deepest portions of the planet’s mantle, a layer of rock beneath the crust.

As tectonic activity has moved portions of the mantle around, rare earth minerals have found their way closer to the surface.

The process of weathering – in which rocks break down into sediment over millions of years – spread these rare minerals all over the planet.

The only thing holding Japan back from using its newly found deposit to dominate the global market for rare-earth minerals is the challenge involved in extracting them.

The process is expensive, so more research needs to be done to determine the cheapest methods, Yutaro Takaya, the study’s lead author, told The Journal.

Rare-earth minerals are likely to remain part the backbone of some the fastest-growing sectors of the global tech economy.

Japan now has the opportunity to control a huge chunk of the global supply, forcing countries that manufacture electronics, like China and the US, to purchase the minerals on Japan’s terms.

See the full article here .

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Please help promote STEM in your local schools.

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