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Simulations predict the existence of black hole radio-wave hot spots

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Some of the synthetic images produced by the researchers, showing that the hot spots rotate as an observer rotates around the spin axis of the black hole. Credit: Crinquand et al

Black holes, regions in spacetime where gravity is so strong that nothing can escape from them, are among the most fascinating and widely studied cosmic phenomena. While there are now countless theories about their formation and underlying physics, many questions remain unanswered.

One of the long-standing questions in the study of black holes is why the plasma surrounding them glows so brightly, as shown by the few direct telescope images collected so far. In a paper published in Physical Review Letters, researchers at Université Grenoble Alpes-CNRS, Trinity College Dublin and University of Maryland presented computer simulations that offer a viable explanation.

“We were very impressed by the recent publication of images of the supermassive black hole M87* by the Event Horizon Telescope (EHT) collaboration,” Benjamin Crinquand, one of the researchers who carried out the study, told Phys.org. “This observation took place when this black hole was at a historically low luminosity (it was ‘quiescent’). However, M87* is known to produce bursts/flares of emission at various wavelengths, up to gamma-rays.”

The key objective of the recent study by Crinquand and his colleagues was to make predictions about how images of the black hole M87* collected by the EHT collaboration would look like if they were collected during one of its common outbursts of emission. To do this, they performed a series of kinetic plasma simulations, representing the vicinity of a spinning black hole during such outbursts.

“This novel simulation tool for understanding plasma behavior in such an extreme environment was developed very recently,” Crinquand explained. “Its goal is to treat the plasma from first principles and to include relevant microphysics, which would be washed out in the common fluid framework (magnetohydrodynamic simulations). Then one needs to know how matter is coupled to radiation, which is ultimately observed from Earth.”

Theoretical and experimental studies have showed that in black hole environments, photons do not propagate in straight lines, due to their strong gravity. In their kinetic simulations, Crinquand and his colleagues tried to account for this by implementing a ray-tracing module, which traces the light emitted by the plasma around a black hole from the simulation to an observer.

Overall, the simulations carried out by this team of researchers suggest that under certain conditions, magnetic-field instabilities can lead to the production of radio-wave hot spots, which would rotate around a black hole’s shadow. The team predicted that for large black holes, such as M87*, the orbital radius of these hotspots would be approximately three times larger than the radius of the black hole, and the hotspots would take around five days to orbit the black hole.

“Our main contribution is the realization that when the black hole is in such a state, the image should display hot spots, which are expected to rotate with time,” Crinquand said. “These hot spots are the signature of ‘plasmoids,’ closed magnetic structures in the black-hole magnetosphere. We also expect the image to shrink within the ‘photon ring,’ which is commonly invoked as being the shadow observed by the EHT in 2019.”

The simulations run by this team of researchers introduce an interesting theoretical hypothesis that could be verified by future astronomical observations. Specifically, they predict that the radiation emission patterns observed around black holes could be due to the breaking of magnetic fields and resulting formation of radio-wave hot spots.

The current version of the EHT might not be sensitive enough to capture the emission patterns they simulated, due to its limited spatial and temporal resolution. Nonetheless, Crinquand and his colleagues hope that future versions of the telescope will help to validate their theory.

“In the future, we wish to pursue two lines of research,” Crinquand added. “Firstly, we are updating our module to account for the polarization of the emitted radiation, to increase the predictive power of our model. In 2021, the EHT released polarized observations of M87*, so the time is now ripe for theorists to make such predictions. On a theoretical side, we also want to better understand what drives this transition between a quiescent and a flaring state. We will especially need to understand the associated time scales: recurrence time of the flares, typical rising, time, etc.”

More information:
Benjamin Crinquand et al, Synthetic Images of Magnetospheric Reconnection-Powered Radiation around Supermassive Black Holes, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.205101

Kyle Parfrey et al, First-Principles Plasma Simulations of Black-Hole Jet Launching, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.122.035101

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Technology

Sky Simulations Releases MD-11 for MSFS

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A new MD-11 has landed on Microsoft Flight Simulator. Developed by Sky Simulations, the new product looks to give those looking to try the tri-engined aircraft an opportunity.

The McDonnell Douglas MD-11 was first introduced in the 1990s and went on to have 200 produced. Whilst its days as a passenger jet are now over, it still operates regularly as a cargo aircraft. Its tri-engine design meant that it allowed airlines to operate over uninhabited areas of the world without ETOP restrictions, thus opening up lots of route opportunities.

The product comes with 4 different models of the MD-11; both passenger and cargo variants, with two different engine types each. Each model comes with native modelling, high resolution textures, 3D animated surfaces and more. According to Sky Simulations, the plane has accurate flight modelling, a fully simulated air system and an operative FMC.

There’s an onboard EFB to control various aircraft options, a flight operations manual and a native MSFS interactive checklist to help you fly the aircraft.

The Sky Simulations MD-11 is available to buy from SIMMARKET for €57.00.

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Science

Supercomputer Simulations Reveal How a Giant Impact Could Have Formed the Moon

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Credit: Durham University

Pioneering scientists from Durham University’s Institute for Computational Cosmology used the most detailed supercomputer simulations yet to reveal an alternative explanation for the Moon’s origin, 4.5 billion years ago. It revealed that a giant impact between Earth and a

The extra computational power revealed that lower-resolution simulations can miss out on crucial aspects of large-scale collisions. With high-resolution simulations, researchers can discover features that weren’t accessible in previous studies. Only the high-resolution simulations produced the Moon-like satellite, and the extra detail revealed how its outer layers contained more material originating from the Earth.

If much of the Moon formed immediately after the giant impact, then this could also mean that less became molten during formation than in the traditional theories where the Moon grew within a debris disk around Earth. Depending on the details of the subsequent solidification, these theories should predict different internal structures for the Moon.

Co-author of the study, Vincent Eke, said: “This formation route could help explain the similarity in isotopic composition between the lunar rocks returned by the Apollo astronauts and Earth’s mantle. There may also be observable consequences for the thickness of the lunar crust, which would allow us to pin down further the type of collision that took place.”

Moreover, they discovered that even when a satellite passes so close to the Earth that it might be expected to be torn apart by the “tidal forces” from Earth’s gravity, the satellite can actually survive. In fact, it can also be pushed onto a wider orbit, safe from future destruction.

A range of new possibilities

Jacob Kegerreis, lead researcher of the study, said: “This opens up a whole new range of possible starting places for the Moon’s evolution. We went into this project not knowing exactly what the outcomes of these very high-resolution simulations would be. So, on top of the big eye-opener that standard resolutions can give you wrong answers, it was extra exciting that the new results could include a tantalizingly Moon-like satellite in orbit.”

The Moon is thought to have formed after a collision between the young Earth and a Mars-sized object, called Theia, 4.5 billion years ago. Most theories construct the Moon by a gradual accumulation of the debris from this impact. However, this has been challenged by measurements of lunar rocks showing their composition is like that of Earth’s mantle, while the impact produces debris that mostly comes from Theia.

This immediate-satellite scenario opens up new possibilities for the initial lunar orbit as well as the predicted composition and internal structure of the Moon. This could help to explain unsolved mysteries like the Moon’s tilted orbit away from Earth’s equator; or could produce an early Moon that is not fully molten, which some scientists propose could be a better match for its thin crust.

The many upcoming lunar missions should reveal new clues about what kind of giant impact led to the Moon, which in turn will tell us about the history of Earth itself.

The research team included scientists at



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Science

Supercomputer Simulations Just Gave Us a New Explanation for How the Moon Was Created

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The Moon may have formed almost immediately following a devastating impact between Earth and a Mars-sized world in the ancient past, according to the results of a new supercomputer study.

Earth’s moon is a silent witness to the history of our entire species. Its gravitational influence is responsible for the tides, and its simple presence in the night sky has profoundly influenced humanity’s cultural development.

Yet despite its ever present nature, the scientific community have yet to come to a consensus on how exactly Earth’s largest natural satellite came to form.

It is widely agreed that the Moon was created when a roughly Mars-sized solar system body — which has been dubbed Theia — collided with Earth roughly 4.5 billion years ago. This impact devastated both our planet, and primordial Theia, and sent vast amounts of material from both worlds hurtling into Earth’s orbit.

Many of the previous theories surrounding the Moon’s formation suggest that it slowly coalesced from this soup of orbital debris, until finally the remainder of the material not accumulated by the satellite fell back in towards Earth.

In this scenario, the orbital debris would have been largely comprised of the remains of Theia. However, rock samples recovered from the Moon’s surface by Apollo-era astronauts showed a surprising structural and isotopic similarity to those found on Earth.

Whilst it is possible, the authors of a new study found it unlikely that the material from Theia would have such a close match with that of the Earth.

In the new study, a team of researchers from Durham University in the UK used the powerful DiRAC supercomputing facility to run a range of simulations that could account for the creation of Earth’s moon.

Moonbreaker – Gamescom 2022

The supercomputer used a significantly larger number of particles to simulate the ancient collision compared to previous studies. According to the team, lower resolution simulations can omit important aspects of the collision process.

Over the course of the study, the scientists ran hundreds of these high-resolution simulations while varying a range of key parameters, including the masses, spins, angles, and speeds of the two unfortunate worlds.

The simulations revealed that a large body with a Moon-like mass and iron content could have coalesced almost immediately in orbit following the Earth-Theia collision. The detailed simulation showed that the newly born hypothetical satellite would have been created beyond the Roche limit – which is the orbital distance at which a satellite can orbit a planet without being shredded by its gravity.

Furthermore, the outer layers of such a world would be rich in material ejected from Earth, thus explaining the similarities between the Apollo-era rocks and those from our planet.

NASA’s Super Heavy Moon Rocket – The Space Launch System

“This formation route could help explain the similarity in isotopic composition between the lunar rocks returned by the Apollo astronauts and Earth’s mantlle,” explains study co-author Vincent Eke, an Associate Professor in the Department of Physics at the University of Exeter. “There may also be observable consequences for the thickness of the lunar crust, which would allow us to pin down further the type of collision that took place.”

If the Moon did form quickly following the impact, then its internal structure would likely be different than if it had grown gradually from a circumplanetary disk of debris. Astronauts returning to the Moon in the coming decades under NASA’s Artemis Program will collect fresh samples from the lunar surface that can be used to test the quick formation theory.

The research could help update scientist’s understanding as to how moons form in the orbits of distant worlds spread throughout the universe.

Anthony Wood is a freelance science writer for IGN

Image Credit: Dr Jacob Kegerreis

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Science

Astrophysicists Create “Time Machine” Simulations To Observe the Lifecycle of Ancestor Galaxy Cities

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Scientists create “time machine” simulations studying the lifecycle of ancestor galaxy cities.

Many processes in astrophysics take a very long time, making their evolution tricky to study. For example, a star like our sun has a lifespan of about 10 billion years and galaxies evolve over the course of billions of years.

One way astrophysicists deal with this is by looking at various different objects to compare them at different stages of evolution. They can also look at distant objects to effectively peer back in time, because of the length of time the light took to travel to reach our telescopes. For example, if we are looking at an object 10 billion light years away, we are seeing it as it was 10 billion years ago.

Now, for the first time, researchers have created simulations that directly recreate the full life cycle of some of the largest collections of galaxies observed in the distant universe 11 billion years ago, reports a new study published on June 2, 2022, in the journal Nature Astronomy.

Cosmological simulations are crucial to studying how the universe became the shape it is today, but many do not typically match what astronomers observe through telescopes. Most are designed to match the real universe only in a statistical sense. Constrained cosmological simulations, on the other hand, are designed to directly reproduce the structures we actually observe in the universe. However, most existing simulations of this kind have been applied to our local universe, meaning close to Earth, but never for observations of the distant universe.

A team of researchers, led by Kavli Institute for the Physics and Mathematics of the Universe Project Researcher and first author Metin Ata and Project Assistant Professor Khee-Gan Lee, were interested in distant structures like massive galaxy protoclusters, which are ancestors of present-day galaxy clusters before they could clump under their own gravity. They found current studies of distant protoclusters were sometimes oversimplified, meaning they were done with simple models and not simulations.

Screenshots from the simulation show (top) the distribution of matter corresponding to the observed galaxy distribution at a light travel time of 11 billion years (when the Universe was only 2.76 billion years old or 20% its current age), and (bottom) the distribution of matter in the same region after 11 billion lights years or corresponding to our present time. Credit: Ata et al.

“We wanted to try developing a full simulation of the real distant universe to see how structures started out and how they ended,” said Ata.

Their result was COSTCO (COnstrained Simulations of The COsmos Field).

Lee said developing the simulation was much like building a time machine. Because light from the distant universe is only reaching Earth now, the galaxies telescopes observe today are a snapshot of the past.

“It’s like finding an old black-and-white picture of your grandfather and creating a video of his life,” he said.

In this sense, the researchers took snapshots of “young” grandparent galaxies in the universe and then fast forwarded their age to study how clusters of galaxies would form.

The light from galaxies the researchers used traveled a distance of 11 billion light-years to reach us.

What was most challenging was taking the large-scale environment into account.

“This is something that is very important for the fate of those structures whether they are isolated or associated with a bigger structure. If you don’t take the environment into account, then you get completely different answers. We were able to take the large-scale environment into account consistently, because we have a full simulation, and that’s why our prediction is more stable,” said Ata.

Another important reason why the researchers created these simulations was to test the standard model of cosmology, that is used to describe the physics of the universe. By predicting the final mass and final distribution of structures in a given space, researchers could unveil previously undetected discrepancies in our current understanding of the universe.

Using their simulations, the researchers were able to find evidence of three already published galaxy protoclusters and disfavor one structure. On top of that, they were able to identify five more structures that consistently formed in their simulations. This includes the Hyperion proto-supercluster, the largest and earliest proto-supercluster known today that is 5000 times the mass of our

Their work is already being applied to other projects including those to study the cosmological environment of galaxies, and absorption lines of distant quasars to name a few.

Details of their study were published in Nature Astronomy on June 2.

Reference: “Predicted future fate of COSMOS galaxy protoclusters over 11 Gyr with constrained simulations” by Metin Ata, Khee-Gan Lee, Claudio Dalla Vecchia, Francisco-Shu Kitaura, Olga Cucciati, Brian C. Lemaux, Daichi Kashino and Thomas Müller, 2 June 2022, Nature Astronomy.
DOI: 10.1038/s41550-022-01693-0



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Technology

MIT used simulations to teach a robot to run, and the results are hilarious

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Scientists at MIT managed to teach a robot to run using machine learning. Normally robots are taught how to move across difficult terrain by preprogramming it into their code. This time, though, the scientists at MIT used simulations to teach the Mini Cheetah to run fast and adapt to walking on different terrain. The researchers showcased the results in a video last week, and they are both intriguing and hilarious.

This isn’t the first time that MIT has taught the robot new tricks, either. Previously, scientists taught the robot how to do backflips.

This video of the Mini Cheetah running is both inspiring and hilarious

As you can see in the video above, the Mini Cheetah isn’t the most graceful machine when it comes to running. But everything it does, it learned to do itself thanks to simulations. The group says it chose machine learning to see how viable it was as an option. Normally, engineers would need to program everything that the robot was going to do.

This takes time, a lot of time, in fact, and is very difficult to do. Not only does the engineer have to code everything, but it has to determine where the robot might fail and how to adapt it to fit those sections. With machine learning, though, robots like the Mini Cheetah can learn to run without needing a helping hand.

The trick to getting the Mini Cheetah running was to let it accumulate days of experience on diverse terrains. The MIT scientists say they were able to send the Mini Cheetah through 100 days’ worth of experience in just three hours. This allowed them to scale up the terrain that it was experiencing quite a lot and let them test things more easily.

More than meets the eye

MIT’s Mini Cheetah training to jump over gaps in terrain. Image source: MIT

The Mini Cheetah’s movements might not look graceful, but the results speak for themselves. By letting the machine learn how to run on its own, the scientists gave it more room to succeed. During testing, it was able to run faster than they’ve ever made it run before. The Mini Cheetah reached up to 13 feet per second or 9 miles per hour. It’s an impressive stat for sure.

It was also able to turn quickly, even on icy surfaces. Further, it did all of this without falling on its face. The technique is called reinforcement learning, and the team used over 4,000 versions of the Mini Cheetah to determine the best movement patterns in their virtual sessions. Any patterns that didn’t promote speediness were thrown out (via Wired).

Scaling up

A futuristic robot concept thinking. Image source: Tatiana Shepeleva/Adobe

Of course, one of the biggest questions surrounding the Mini Cheetah and its recent success story is, can these results be scaled up? In a Q&A post, MIT Ph.D. student Gabriel Margolis and IAIFI postdoc Ge Yang say that the current way that we do robotics isn’t scalable. That’s because it requires humans to tell the robot what to do, as well as how to do it.

With the current system that MIT is testing, the robot is told what to do but must figure out the best way to do it. Sure, there are some issues with it, like how awkward the robot moves. But, overall, the system could open a lot of doors for the robotics world.

In this test, the scientists threw out patterns that didn’t promote speediness. But what if they did another test with the Mini Cheetah that blends speediness with sturdiness? I’d personally love to see how those results look, especially given how promising these latest ones turned out.



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Science

Stunning Loops of Plasma Observed on The Sun May Not Be What We Thought

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A well-studied solar phenomenon may not be quite as simple as we we thought it was.

New simulations suggest that what we thought were loops of plasma known as coronal loops erupting out from the surface of the Sun along magnetic field lines may, at least sometimes, be wrinkles in corrugated sheets of plasma.

 

Astronomers have dubbed this phenomenon the “coronal veil”, and suggest that further research is needed to try to understand how and why they occur.

The finding is, they say, significant. Since coronal loops were first identified clearly in the 1960s, solar scientists have been using them to understand the properties of the Sun, including its magnetic field, and the density and temperature of the solar atmosphere.

“I have spent my entire career studying coronal loops,” says astrophysicist Anna Malanushenko of the National Center for Atmospheric Research.

“I never expected this. When I saw the results, my mind exploded.”

Coronal loops are fascinating and beautiful: long, closed arcs of glowing plasma, sometimes associated with sunspots. But, although scientists have been analyzing them to better understand the Sun for decades, a few of their properties don’t match what we might expect.

Firstly, coronal loops associated with sunspots tend to be much taller than calculations suggest they should be.

Secondly, the loops don’t become less bright with height. Think of iron filings sprinkled near a bar magnet, self-arranging in loops. The bigger loops that reach farther from the magnet are thinner and more tenuous.

Iron filings along the magnetic field of a sphere magnet. (Geek3/Wikimedia Commons/CC BY-SA 4.0)

Coronal loops look like these iron loops, but if coronal loops were associated with magnetic fields, they should display similar visual expansion – higher loops are as bright as lower ones.

Malanushenko and her team conducted models of the solar corona using a software program called MURaM, which generates realistic magnetohydrodynamic simulations of the Sun. Recently, this was updated to include the solar corona, which made it an excellent tool for trying to better understand coronal loops.

Coronal loops imaged by the Transition Region And Coronal Explorer spacecraft. (NASA/LMSAL)

When the team ran their simulations, however, they found that the loops were not always discrete structures at all, but folds in optically thin sheets of plasma. Because these wrinkles are thicker and more dense, we can see them clearly.

However, the simulation also revealed that coronal loops can exist on their own, too. This suggests that the solar corona is a much more complex environment than we knew.

 

“This study reminds us as scientists that we must always question our assumptions and that sometimes our intuition can work against us,” Malanushenko says.

In addition to the coronal veils, the team’s simulations also capture the entire life cycle of a solar flare, and produced three-dimensional datasets of the solar atmosphere that can be used to conduct synthetic observations of the plasma and magnetic field. This can be used to probe the loops and veils in more detail.

That’s because understanding these structures from real solar observations can be tricky. When you’re looking at a loop from the side, the shape of its loop can’t be seen; but, when viewing from the front, you can’t see how wide the loop is, if it’s more like a thread or ribbon of plasma.

While veils resolve the properties of coronal loops that didn’t quite fit, there are some questions that remain unanswered. For example, how and why these structures form, and what makes them wrinkle. It’s also unclear how many of them might be real coronal loops. Synthetic observations might provide some answers.

 

That’s going to require designing new observational methods and analytical techniques, but the results so far could have implications for other areas of plasma physics, especially if there are structures in the fluid that are difficult, if not impossible, to see.

“This study demonstrates that the way we currently interpret the observations of the Sun may not be adequate for us to truly understand the physics of our star,” Malanushenko says.

“This is an entirely new paradigm of understanding the Sun’s atmosphere.”

The research has been published in The Astrophysical Journal.

 

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Science

Behold, The Most Accurate Virtual Simulation of Our Universe to Date

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In the Cosmic Calendar, which maps the chronology of the Universe across a single Earth year, modern humans don’t appear until the very last minute of December 31.

Everything we understand about the evolution of the Universe, we’ve had to piece together. We simply haven’t been around for pretty much any of the 13.7 billion-year history of the cosmos to observe it in action.

 

That detective work has been pretty epic. And one of the tools in our kit is simulations of the formation and evolution of the vast structures that span observable space.

Now, using supercomputers, an international team of scientists led by the University of Helsinki in Finland has produced the largest and most accurate simulation yet of the evolution of the local Universe. This can help us understand the dynamics at play as the Universe continues to evolve, including the mysterious dark matter and dark energy.

“The simulations simply reveal the consequences of the laws of physics acting on the dark matter and cosmic gas throughout the 13.7 billion years that our Universe has been around,” says cosmologist Carlos Frenk of Durham University in the UK.

“The fact that we have been able to reproduce these familiar structures provides impressive support for the standard Cold Dark Matter model and tells us that we are on the right track to understand the evolution of the entire Universe.”

The simulation is called SIBELIUS-DARK, and it covers a volume of space extending 600 million light-years from the Solar System. This includes several clusters of galaxies, including Virgo, Coma, and Perseus; the Milky Way and Andromeda galaxies; the Local Void; and the Great Attractor.

The dark matter distribution of the SIBERIUS-DARK volume. (McAlpine et al., MNRAS, 2022)

Within this volume of space, the simulation needed to account for around 130 billion particles. Computing these particles over the entire lifespan of the Universe – and at a higher resolution than ever before – took several weeks on the DiRAC COSmology MAchine (COSMA) supercomputer at Durham University, producing a petabyte of data. Then, the researchers had to compare the results with observational surveys of the real Universe.

This allows them to explore something called the Cold Dark Matter model of cosmology, the current standard for mapping the evolution of the Universe. It relies on a vast cosmic web of dark matter, the mysterious invisible mass responsible for adding gravity to the Universe beyond what can be accounted for by normal matter.

 

According to this model, dark matter accumulates in clumps called haloes. Hydrogen and other gases feed into these haloes, eventually forming stars and then galaxies. This model explains quite a few properties of the observable Universe. However, most simulations incorporating it simulate a random patch of the Universe.

Our patch of the Universe is a little outside the randomized norm. The Milky Way is floating in a void, or a relative underdensity of galaxies compared to the average distribution in the wider Universe. So the researchers decided to recreate our own corner of the Universe, to see if the Cold Dark Matter model could reproduce what we see in our immediate vicinity.

It could.

“This project is truly groundbreaking,” says cosmologist Matthieu Schaller of Leiden University in the Netherlands. “These simulations demonstrate that the standard Cold Dark Matter Model can produce all the galaxies we see in our neighborhood. This is a very important test for the model to pass.”

But SIBELIUS-DARK also showed that the Local Void might be unusual, in that it appears to have evolved from a local large-scale underdensity of dark matter from the outset. What produced this underdensity in the early cosmic web will need to be the subject of future explorations.

 

Meanwhile, the team will be conducting further analyses of the simulation to test the Cold Dark Matter model of cosmology.

“By simulating our Universe, as we see it, we are one step closer to understanding the nature of our cosmos,” says physicist Stuart McAlpine of the University of Helsinki.

“This project provides an important bridge between decades of theory and astronomical observations.”

The research has been published in the Monthly Notices of the Royal Astronomical Society.

 

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Science

Supercomputers Simulated a Black Hole And Found Something We’ve Never Seen Before

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While black holes might always be black, they do occasionally emit some intense bursts of light from just outside their event horizon. Previously, what exactly caused these flares had been a mystery to science. 

 

That mystery was solved recently by a team of researchers that used a series of supercomputers to model the details of black holes’ magnetic fields in far more detail than any previous effort. The simulations point to the breaking and remaking of super-strong magnetic fields as the source of the super-bright flares.

Scientists have known that black holes have powerful magnetic fields surrounding them for some time. Typically these are just one part of a complex dance of forces, material, and other phenomena that exist around a black hole.

That complex dance has been notoriously hard to model, even with advanced supercomputers, so trying to understand the details of what is happening around a black hole has proven exceptionally difficult.

Stronger computers can handle difficult computer problems, and, thanks to Moore’s law, that is exactly what humanity has now.

Dr. Bart Ripperda, co-lead author of the study and a postdoctoral fellow at the Flatiron Institute and Princeton University, and his colleagues utilized three separate supercomputing clusters to produce the most detailed image of the physics going on outside a black hole event horizon.

 

Magnetic fields unsurprisingly played a major role in those physics. But more importantly, they played a critical role in developing flares. Specifically, flares formed when magnetic fields broke apart then rejoined back together. 

The magnetic energy unleashed by these processes supercharges photons in the surrounding medium, and some of those photons get ejected straight into the black hole’s event horizon, while others get ejected out into space in the form of flares.

Simulated black hole with magnetic field lines in green. (B. Ripperda et al., AJL, 2022)

Simulations showed the breaking and making of magnetic field connections that were invisible at previously available resolutions. Ripperda and his colleagues’ image had 1,000 times the resolution of any previously available black hole simulation. 

The most accurate simulations in the world can’t make up for an incorrect model, so previous simulations ignored basic features of black hole interactions.

With high resolution came greater understanding. The new simulations accurately modeled how the magnetic field process around the event horizon works.

First, the material collected in the accretion disk migrates towards the black hole’s ‘poles’. Migrating charged material like that is sure to affect magnetic field lines, which attempt to move with it.

 

Part of that movement process causes some of the magnetic field lines to break and potentially reconnect with a different field line. In some cases, a pocket of material is formed that is insulated from other external forces, but is eventually shot out towards the black hole itself or the rest of the Universe. This is where flares come from.

All those processes are difficult to simulate, even on a cluster of supercomputers. However, most simulations are built to fit the existing data the best. 

Collecting data to test these simulations is still a long way off. But you can be sure that someone, somewhere, is already working on it.

This article was originally published by Universe Today. Read the original article.

 

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Science

Simulations show iron catalyzes corrosion in ‘inert’ carbon dioxide

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Iron (blue) can react with trace amounts of water to produce corrosive chemicals despite being bathed in “inert” supercritical fluids of carbon dioxide. Atomistic simulations carried out at Rice University show how this reaction happens. Credit: Evgeni Penev/Rice University

Iron that rusts in water theoretically shouldn’t corrode in contact with an “inert” supercritical fluid of carbon dioxide. But it does.

The reason has eluded materials scientists to now, but a team at Rice University has a theory that could contribute to new strategies to protect iron from the environment.

Materials theorist Boris Yakobson and his colleagues at Rice’s George R. Brown School of Engineering found through atom-level simulations that iron itself plays a role in its own corrosion when exposed to supercritical CO2 (sCO2) and trace amounts of water by promoting the formation of reactive species in the fluid that come back to attack it.

In their research, published in the Cell Press journal Matter, they conclude that thin hydrophobic layers of 2D materials like graphene or hexagonal boron nitride could be employed as a barrier between iron atoms and the reactive elements of sCO2.

Rice graduate student Qin-Kun Li and research scientist Alex Kutana are co-lead authors of the paper. Rice assistant research professor Evgeni Penev is a co-author.

Supercritical fluids are materials at a temperature and pressure that keeps them roughly between phases—say, not all liquid, but not yet all gas. The properties of sCO2 make it an ideal working fluid because, according to the researchers, it is “essentially inert,” noncorrosive and low-cost.

“Eliminating corrosion is a constant challenge, and it’s on a lot of people’s minds right now as the government prepares to invest heavily in infrastructure,” said Yakobson, the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry. “Iron is a pillar of infrastructure from ancient times, but only now are we able to get an atomistic understanding of how it corrodes.”

The Rice lab’s simulations reveal the devil’s in the details. Previous studies have attributed corrosion to the presence of bulk water and other contaminants in the superfluid, but that isn’t necessarily the case, Yakobson said.

“Water, as the primary impurity in sCO2, provides a hydrogen bond network to trigger interfacial reactions with CO2 and other impurities like nitrous oxide and to form corrosive acid detrimental to iron,” Li said.

The simulations also showed that the iron itself acts as a catalyst, lowering the reaction energy barriers at the interface between iron and sCO2, ultimately leading to the formation of a host of corrosive species: oxygen, hydroxide, carboxylic acid and nitrous acid.

To the researchers, the study illustrates the power of theoretical modeling to solve complicated chemistry problems, in this case predicting thermodynamic reactions and estimates of corrosion rates at the interface between iron and sCO2. They also showed all bets are off if there’s more than a trace of water in the superfluid, accelerating corrosion.

Team creates supercritical carbon dioxide turbomachinery for concentrated solar power plant

More information:
Qin-Kun Li et al, Iron corrosion in the “inert” supercritical CO2, ab initio dynamics insights: How impurities matter, Matter (2022). DOI: 10.1016/j.matt.2021.12.019
Provided by
Rice University

Citation:
Simulations show iron catalyzes corrosion in ‘inert’ carbon dioxide (2022, January 21)
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