The Most Complete and Detailed X-Ray View of Puppis A

This new image of supernova remnant Puppis A includes data from Chandra and XMM-Newton and is the most complete and detailed X-ray view to date, revealing a delicate tapestry of X-ray light left behind by the supernova explosion.

The destructive results of a powerful supernova explosion reveal themselves in a delicate tapestry of X-ray light, as seen in this image from NASA’s Chandra X-Ray Observatory and the European Space Agency’s XMM-Newton.

The image shows the remains of a supernova that would have been witnessed on Earth about 3,700 years ago. The remnant is called Puppis A, and is around 7,000 light years away and about 10 light years across. This image provides the most complete and detailed X-ray view of Puppis A ever obtained, made by combining a mosaic of different Chandra and XMM-Newton observations. Low-energy X-rays are shown in red, medium-energy X-rays are in green and high energy X-rays are colored blue.

These observations act as a probe of the gas surrounding Puppis A, known as the interstellar medium. The complex appearance of the remnant shows that Puppis A is expanding into an interstellar medium that probably has a knotty structure.

Supernova explosions forge the heavy elements that can provide the raw material from which future generations of stars and planets will form. Studying how supernova remnants expand into the galaxy and interact with other material provides critical clues into our own origins.

A paper describing these results was published in Astronomy and Astrophysics. The first author is Gloria Dubner from the Instituto de Astronomía y Física del Espacio in Buenos Aires in Argentina.

Publication: G. Dubner, et al., “The most complete and detailed X-ray view of the SNR Puppis A,” A&A, Volume 555, A9, 2013; doi:10.1051/0004-6361/201321401

Brain Structure of the Parietal Cortex Could Predict Risky Behavior

New research shows that brain structure may predict risky behavior, revealing that those with a larger volume in a particular part of the parietal cortex were willing to take more risks than those with less volume in this part of the brain.

Some people avoid risks at all costs, while others will put their wealth, health, and safety at risk without a thought. Researchers at Yale School of Medicine have found that the volume of the parietal cortex in the brain could predict where people fall on the risk-taking spectrum.

Led by Ifat Levy, assistant professor in comparative medicine and neurobiology at Yale School of Medicine, the team found that those with larger volume in a particular part of the parietal cortex were willing to take more risks than those with less volume in this part of the brain. The findings are published in the September 10 issue of the Journal of Neuroscience.

Although several cognitive and personality traits are reflected in brain structure, there has been little research linking brain structure to economic preferences. Levy and her colleagues sought to examine this question in their study.

Study participants included young adult men and women from the northeastern United States. Participants made a series of choices between monetary lotteries that varied in their degree of risk, and the research team conducted standard anatomical MRI brain scans. The results were first obtained in a group of 28 participants, and then confirmed in a second, independent, group of 33 participants.

“Based on our findings, we could, in principle, use millions of existing medical brains scans to assess risk attitudes in populations,” said Levy. “It could also help us explain differences in risk attitudes based in part on structural brain differences.”

Levy cautions that the results do not speak to causality. “We don’t know if structural changes lead to behavioral changes or vice-versa,” she said.

Levy and her team had previously shown that risk aversion increases as people age, and we scientists also know that the cortex thins substantially with age. “It could be that this thinning explains the behavioral changes; we are now testing that possibility,” said Levy, who also notes that more studies in wider populations are needed.

The study was a collaboration of researchers from Yale, University College London, New York University, University of Pennsylvania, and the University of Sydney, Australia. In addition to Levy, authors include Sharon Gilaie-Dotan, Agnieszka Tymula, Nicole Cooper, Joseph W. Kable, and Paul W. Glimcher.

The study was funded by the National Institute of Aging (R01AG033406)

Publication: (In press) The Journal of Neuroscience doi DOI:10.1523/JNEUROSCI.1600-14.2014 (September 10, 2014)

Using ‘Solid’ Light to Answer Previously Unsolvable Problems

By crystallizing light, Princeton University researchers have begun to address questions about the fundamental study of matter.

The researchers are not shining light through crystal – they are transforming light into crystal. As part of an effort to develop exotic materials such as room-temperature superconductors, the researchers have locked together photons, the basic element of light, so that they become fixed in place.

“It’s something that we have never seen before,” said Andrew Houck, an associate professor of electrical engineering and one of the researchers. “This is a new behavior for light.”

The results raise intriguing possibilities for a variety of future materials. But the researchers also intend to use the method to address questions about the fundamental study of matter, a field called condensed matter physics.

“We are interested in exploring – and ultimately controlling and directing – the flow of energy at the atomic level,” said Hakan Türeci, an assistant professor of electrical engineering and a member of the research team. “The goal is to better understand current materials and processes and to evaluate materials that we cannot yet create.”

The team’s findings, reported online on September 8 in the journal Physical Review X, are part of an effort to answer fundamental questions about atomic behavior by creating a device that can simulate the behavior of subatomic particles. Such a tool could be an invaluable method for answering questions about atoms and molecules that are not answerable even with today’s most advanced computers.

In part, that is because current computers operate under the rules of classical mechanics, which is a system that describes the everyday world containing things like bowling balls and planets. But the world of atoms and photons obeys the rules of quantum mechanics, which include a number of strange and very counterintuitive features. One of these odd properties is called “entanglement” in which multiple particles become linked and can affect each other over long distances.

The difference between the quantum and classical rules limits a standard computer’s ability to efficiently study quantum systems. Because the computer operates under classical rules, it simply cannot grapple with many of the features of the quantum world. Scientists have long believed that a computer based on the rules of quantum mechanics could allow them to crack problems that are currently unsolvable. Such a computer could answer the questions about materials that the Princeton team is pursuing, but building a general-purpose quantum computer has proven to be incredibly difficult and requires further research.

Another approach, which the Princeton team is taking, is to build a system that directly simulates the desired quantum behavior. Although each machine is limited to a single task, it would allow researchers to answer important questions without having to solve some of the more difficult problems involved in creating a general-purpose quantum computer. In a way, it is like answering questions about airplane design by studying a model airplane in a wind tunnel – solving problems with a physical simulation rather than a digital computer.

In addition to answering questions about currently existing material, the device also could allow physicists to explore fundamental questions about the behavior of matter by mimicking materials that only exist in physicists’ imaginations.

To build their machine, the researchers created a structure made of superconducting materials that contains 100 billion atoms engineered to act as a single “artificial atom.” They placed the artificial atom close to a superconducting wire containing photons.

By the rules of quantum mechanics, the photons on the wire inherit some of the properties of the artificial atom – in a sense linking them. Normally photons do not interact with each other, but in this system the researchers are able to create new behavior in which the photons begin to interact in some ways like particles.

“We have used this blending together of the photons and the atom to artificially devise strong interactions among the photons,” said Darius Sadri, a postdoctoral researcher and one of the authors. “These interactions then lead to completely new collective behavior for light – akin to the phases of matter, like liquids and crystals, studied in condensed matter physics.”

Türeci said that scientists have explored the nature of light for centuries; discovering that sometimes light behaves like a wave and other times like a particle. In the lab at Princeton, the researchers have engineered a new behavior.

“Here we set up a situation where light effectively behaves like a particle in the sense that two photons can interact very strongly,” he said. “In one mode of operation, light sloshes back and forth like a liquid; in the other, it freezes.”

The current device is relatively small, with only two sites where an artificial atom is paired with a superconducting wire. But the researchers say that by expanding the device and the number of interactions, they can increase their ability to simulate more complex systems – growing from the simulation of a single molecule to that of an entire material. In the future, the team plans to build devices with hundreds of sites with which they hope to observe exotic phases of light such as superfluids and insulators.

“There is a lot of new physics that can be done even with these small systems,” said James Raftery, a graduate student in electrical engineering and one of the authors. “But as we scale up, we will be able to tackle some really interesting questions.”

Besides Houck, Türeci, Sadri and Raftery, the research team included Sebastian Schmidt, a senior researcher at the Institute for Theoretical Physics at ETH Zurich, Switzerland. Support for the project was provided by: the Eric and Wendy Schmidt Transformative Technology Fund; the National Science Foundation; the David and Lucile Packard Foundation; the U.S. Army Research Office; and the Swiss National Science Foundation.

Publication: J. Raftery, et al., “Observation of a Dissipation-Induced Classical to Quantum Transition,” Phys. Rev. X 4, 031043, 2014; doi:10.1103/PhysRevX.4.031043

Researchers Successfully Synthesize 2D Material Germanene

(a) 16.2 nm × 16.2 nm STM image of the modulated honeycomb √7 × √7 superstructure with a close-up in the bottom left corner (sample bias: −1.12 V, 1.58 nA; the √7 × √7 unit cell is drawn in black); (b) associated LEED pattern taken at 59 V; (c) schematic illustration of one sixth of the pattern, filled dots: hidden (0,0) spot and integer order spots, open circles: spots corresponding to the √7 × √7 superstructure (in red), the √19 × √19 one (in green) and the 5 × 5 (in blue).

A newly published study details how a team of researchers successfully synthesized the 2D material germanene for the first time.

Dubbed a “cousin of graphene”, the material, which is made up of just a single layer of germanium atoms, is expected to exhibit impressive electrical and optical properties and could be widely integrated across the electronics industry in the future.

The material has been presented today in the Institute of Physics and German Physical Society’s New Journal of Physics.

Germanene was first proposed in 2009 but has, up until now, remained elusive. Since then, graphene has been developed further while other 2D materials, such as silicene, have been synthesized.

Much like silicene, the proposed method for synthesizing germanene is to deposit individual germanium atoms onto a substrate under high temperatures and in an ultra-high vacuum.

The breakthrough by the European research team was made in parallel with an independent team from China who have reported evidence that germanene has been synthesized onto a platinum substrate.

In the current study the researchers discovered, somewhat serendipitously, that gold could also be used as a substrate, an event which co-author of the study Professor Guy Le Lay, from Aix-Marseille University, described as “like passing through the looking glass”.

“Following our synthesis of graphene’s other cousin, silicene, we thought it natural to try and produce germanene in the same way, by despositing germanium onto a silver substrate,” Le Lay said.

“This attempt failed, so I decided to switch to a gold substrate, having remembered my old work from my PhD thesis, in which gold was grown onto a germanium substrate. I thought it would be worth trying the other way around.”

After depositing the germanium atoms onto a gold substrate, the researchers were able to confirm that the material was in fact germanene by taking spectroscopy measurements and density functional theory (DFT) calculations, which investigated the electronic structure of the material.

The material was also observed under a scanning tunneling microscope, which revealed the characteristic honeycomb structure of a 2D material.

The researchers believe that with further development it may be possible for germanene to be grown on thin gold films sitting on top of a flexible substrate, which would certainly be cheaper than platinum and could allow germanene to be synthesized on a large scale.

Additionally, the unique properties of germanene could make it a robust 2D topological insulator, particularly up to room temperature, opening up the possibility of using the material in quantum computing.

Professor Le Lay continued: “We have provided compelling evidence of the birth of nearly flat germanene—a novel, synthetic germanium allotrope which does not exist in nature. It is a new cousin of graphene.

“The synthesis of germanene is just the very beginning of a long quest. Indeed, success in the synthesis was not easy to achieve and quite demanding. A considerable amount of work is now needed to further characterize the electronic properties of the material.’

Co-author of the study Professor Angel Rubio, from the University of the Basque Country, added: “An important aspect of our study is that we have increased the lego of 2D materials that we can use to build a whole host of artificial solid materials with a wide range of differing properties.”

Publication: M. E. Dávila, et al., “Germanene: a novel two-dimensional germanium allotrope akin to graphene and silicene,” 2014, New J. Phys. 16 095002;
doi:10.1088/1367-2630/16/9/095002

Worldwide Action to Phase Out Ozone-Depleting Substances Yields Significant Gains

Minimum concentration of ozone in the southern hemisphere for each year from 1979-2013 (there is no data from 1995). Each image is the day of the year with the lowest concentration of ozone. A graph of the lowest ozone amount for each year is shown. Image Credit: NASA’s Goddard Space Flight Center/M. Radcliff

Worldwide action to phase out ozone-depleting substances has resulted in remarkable success, according to a new assessment by 300 international scientists. The stratospheric ozone layer, a fragile shield of gas that protects Earth from harmful ultraviolet light, is on track to recovery over the next few decades.

The Assessment for Decision-Makers, a summary of the Scientific Assessment of Ozone Depletion 2014, provides new information to affirm that the 1987 international agreement known as the Montreal Protocol on Substances that Deplete the Ozone Layer has successfully resulted in global international policies to reduced levels of ozone-depleting substances.

The report is conducted by the World Meteorological Organization, or WMO, and the United Nations Environmental Program, or UNEP, and co-sponsored by NASA, National Oceanic and Atmospheric Administration, or NOAA, and the European Commission. Science teams from these organizations and other countries have been monitoring the ozone layer on the ground, by balloon and with a variety of satellite instruments dating back to NASA’s Nimbus 4 satellite, launched in 1970.

The most current ozone hole satellite data comes from the Ozone Monitoring and Profiler Suite instrument on the NASA-NOAA Suomi National Polar-orbiting Partnership satellite, known as Suomi NPP, and the Ozone Monitoring Instrument and Microwave Limb Sounder on NASA’s Aura satellite.

“It is particularly gratifying to report that the ozone layer is on track for recovery to 1980 benchmark levels by mid-century,” said Paul A. Newman, chief scientist for atmospheres at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and a co-chair of the WMO/UNEP report. “Many of these early signs of ozone improvements are due to decades of work and contributions by NASA and NOAA instruments and scientists.”

Ozone depleting substances are also powerful greenhouse gases. The Montreal Protocol provided a double benefit: stopping ozone depletion, and slowing the growth of greenhouse gases. “Substitutes for ozone depleting substances are ozone safe, but many are powerful greenhouse gases. These substitutes could offset the climate gains achieved by the Montreal Protocol in the future,” Newman said.

The Assessment for Decision-Makers, a summary of the Scientific Assessment of Ozone Depletion 2014 is the first comprehensive update in four years. The full report will be available in early 2015.

Mysterious Holes in the Atmosphere of Venus

New research investigates the mysterious holes discovered by ESA’s Venus Express on the nightside of Venus’s ionosphere, finding evidence that the sun’s magnetic field lines may be penetrating through the planet.

New research shows giant holes in Venus’s atmosphere – which serve as extra clues for understanding this planet so different from our own. Image Credit: NASA/Goddard/Duberstein

Underscoring the vast differences between Earth and its neighbor Venus, new research shows a glimpse of giant holes in the electrically charged layer of the Venusian atmosphere, called the ionosphere. The observations point to a more complicated magnetic environment than previously thought – which in turn helps us better understand this neighboring, rocky planet.

Planet Venus, with its thick atmosphere made of carbon dioxide, its parched surface, and pressures so high that landers are crushed within a few hours, offers scientists a chance to study a planet very foreign to our own. These mysterious holes provide additional clues to understanding Venus’s atmosphere, how the planet interacts with the constant onslaught of solar wind from the sun, and perhaps even what’s lurking deep in its core.

“This work all started with a mystery from 1978,” said Glyn Collinson, a space scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who is first author of a paper on this work in the Journal of Geophysical Research. “When Pioneer Venus Orbiter moved into orbit around Venus, it noticed something very, very weird – a hole in the planet’s ionosphere. It was a region where the density just dropped out, and no one has seen another one of these things for 30 years.”

Until now.

Collinson set out to search for signatures of these holes in data from the European Space Agency’s Venus Express. Venus Express, launched in 2006, is currently in a 24-hour orbit around the poles of Venus. This orbit places it in much higher altitudes than that of the Pioneer Venus Orbiter, so Collinson wasn’t sure whether he’d spot any markers of these mysterious holes. But even at those heights the same holes were spotted, thus showing that the holes extended much further into the atmosphere than had been previously known.

The observations also suggested the holes are more common than realized. Pioneer Venus Orbiter only saw the holes at a time of great solar activity, known as solar maximum. The Venus Express data, however, shows the holes can form during solar minimum as well.

Interpreting what is happening in Venus’s ionosphere requires understanding how Venus interacts with its environment in space. This environment is dominated by a stream of electrons and protons – a charged, heated gas called plasma — which zoom out from the sun. As this solar wind travels it carries along embedded magnetic fields, which can affect charged particles and other magnetic fields they encounter along the way. Earth is largely protected from this radiation by its own strong magnetic field, but Venus has no such protection.

What Venus does have, however, is an ionosphere, a layer of the atmosphere filled with charged particles. The Venusian ionosphere is bombarded on the sun-side of the planet by the solar wind. Consequently, the ionosphere, like air flowing past a golf ball in flight, is shaped to be a thin boundary in front of the planet and to extend into a long comet-like tail behind. As the solar wind plows into the ionosphere, it piles up like a big plasma traffic jam, creating a thin magnetosphere around Venus – a much smaller magnetic environment than the one around Earth.

Venus Express is equipped to measure this slight magnetic field. As it flew through the ionospheric holes it recorded a jump in the field strength, while also spotting very cold particles flowing in and out of the holes, though at a much lower density than generally seen in the ionosphere. The Venus Express observations suggest that instead of two holes behind Venus, there are in fact two long, fat cylinders of lower density material stretching from the planet’s surface to way out in space. Collinson said that some magnetic structure probably causes the charged particles to be squeezed out of these areas, like toothpaste squeezed out of a tube.

The next question is what magnetic structure can create this effect? Imagine Venus standing in the middle of the constant solar wind like a lighthouse erected in the water just off shore. Magnetic field lines from the sun move toward Venus like waves of water approaching the lighthouse. The far sides of these lines then wrap around the planet leading to two long straight magnetic field lines trailing out directly behind Venus. These lines could create the magnetic forces to squeeze the plasma out of the holes.

But such a scenario would place the bottom of these tubes on the sides of the planet, not as if they were coming straight up out of the surface. What could cause magnetic fields to go directly in and out of the planet? Without additional data, it’s hard to know for sure, but Collinson’s team devised two possible models that can match these observations.

In one scenario, the magnetic fields do not stop at the edge of the ionosphere to wrap around the outside of the planet, but instead continue further.

“We think some of these field lines can sink right through the ionosphere, cutting through it like cheese wire,” said Collinson. “The ionosphere can conduct electricity, which makes it basically transparent to the field lines. The lines go right through down to the planet’s surface and some ways into the planet.”

In this scenario, the magnetic field travels unhindered directly into the upper layers of Venus. Eventually, the magnetic field hits Venus’ rocky mantle – assuming, of course, that the inside of Venus is like the inside of Earth. A reasonable assumption given that the two planets are the same mass, size and density, but by no means a proven fact.

A similar phenomenon does happen on the moon, said Collinson. The moon is mostly made up of mantle and has little to no atmosphere. The magnetic field lines from the sun go through the moon’s mantle and then hit what is thought to be an iron core.

In the second scenario, the magnetic fields from the solar system do drape themselves around the ionosphere, but they collide with a pile up of plasma already at the back of the planet. As the two sets of charged material jostle for place, it causes the required magnetic squeeze in the perfect spot.

Either way, areas of increased magnetism would stream out on either side of the tail, pointing directly in and out of the sides of the planet. Those areas of increased magnetic force could be what squeezes out the plasma and creates these long ionospheric holes.

Scientists will continue to explore just what causes these holes. Confirming one theory or the other will, in turn, help us understand this planet, so similar and yet so different from our own.

Study Explains Prevalence of Hadrosaur Skin Among All Known Dinosaur Skin Fossils

At right is a reconstruction of what the skin of hadrosaur Edmontosaurus annectens might have looked like, based on the famous hadrosaur mummy at the American Museum of Natural History in New York City. (Illustration by Patrick Lynch)

A new study from Yale University details the prevalence of hadrosaur skin among all known dinosaur skin fossils, revealing that hadrosaur skin is 31 times more likely to be preserved.

In life, Tyrannosaurus rex usually got the best of the less fearsome duck-billed dinosaurs, or hadrosaurs: T. rex ate them.

But in death, the plant-eating hadrosaurs have proved more resilient than their carnivorous predators — and apparently all other dinosaurs — at least by the measure of their skin.

In an exhaustive new survey of dinosaur skin samples and a related statistical analysis, Matt Davis of Yale University documents the prevalence of hadrosaur skin among all known dinosaur skin fossils, and offers a new explanation for it: Hadrosaur skin was tougher.

“If you are a hadrosaur versus another dinosaur, you’re 31 times more likely to preserve skin,” said Davis, a fifth-year graduate student in paleontology at Yale and the author of a paper published in the September 10 print issue of the journal Acta Paleontologica Polonica.

Previous explanations for the relative abundance of hadrosaur skin fossils attributed it to the sheer number of hadrosaurs among all dinosaurs. Hadrosaurs — many species of which are characterized by protuberant crests on their heads — were among the most common worldwide.

Other explanations attributed the frequent occurrence of hadrosaur skin in the fossil record to hadrosaurs’ lifestyle — they tended to live (and die) along rivers, where flash flooding could quickly bury them in alluvial sediments, protecting the corpse from scavengers.

But Davis presents evidence that, he argues, rules out these traditional explanations in favor of something special about hadrosaurs’ skin.

Davis reviewed every published scientific report of dinosaur skin from 1841 through 2010 — 180 reports in all (representing a greater number of individual skin samples) — to determine the prevalence of hadrosaur skin relative to other dinosaur skin. Of 123 body fossils with skin (as opposed to trace fossil skin, such as footprints), 57 — or 46% — were from hadrosaurs.

Additionally, Davis analyzed data describing 343 dinosaurs from the Hell Creek Formation in Montana and the Dakotas, one of the world’s richest deposits of dinosaur fossils, and similar formations in the United States and Canada. Of 343 individuals, 80 were hadrosaurids, or about 23%. And of the 80 hadrosaurids, 20 — fully 25% — bore evidence of skin.

Of the other 263 other (non-hadrosaur) Hell Creek dinosaurs, representing about a dozen large dinosaur species, only two individuals showed evidence of skin. One was a thescelosaur, and one was a tyrannosaur.

In short, of 22 Hell Creek dinosaurs leaving behind traces of skin, 20 — or 90% — were hadrosaurs.

“We’ve always assumed hadrosaur fossils preserved more skin,” said Davis. “Now we’ve got the data to prove just how much more.”

Other evidence suggests that environmental factors and the size of the hadrosaur population do not explain why traces of their skin are more common than that of other dinosaurs, Davis said. While hadrosaurs were great in number, for instance, other dinosaurs, such as ceratopsians(including Triceratops and Torosaurus), were more numerous, yet left behind far less skin — or none at all. In the Hell Creek Formation, ceratopsians outnumber hadrosaurs 2:1.

Moreover, hadrosaur skin has been found in a variety of environments, not only ancient river valleys. Similarly, many other dinosaur species found in (formerly) watery areas contain no trace of skin.

And hadrosaurs not only tend to leave behind skin more often, Davis said, but also in greater abundance: Most mummy dinosaurs — which preserve most of the body skin — are hadrosaurs, he said.

Skin offers scientists the possibility of a deeper understanding of dinosaurs than fossilized bones alone, which represent the overwhelming majority of physical evidence of dinosaurs. Skin can help distinguish species and determine where and how big a dinosaur’s muscles were by providing a surface boundary (the bones provide the internal boundary), how fast they could run, whether they could swim, what their habitat was like, and, of course, more detail about what they looked like, Davis said.

“Crests, spikes, waddles, cheeks, webbed hands, and so forth mostly preserve only as skin,” he said.

Once considered exceedingly rare, dinosaur skin samples have become more and more common with the development of more refined, less destructive excavation methods, Davis said. “Now people take the whole chuck of rock with them and 3D scan [the fossil inside] it,” he said. “With these new techniques, we’re finding it a lot more.”

At this point, he added, finding hadrosaur skin “wouldn’t be news to anyone.”

Davis said future work is needed to determine the specific characteristics of hadrosaur skin that made it tough.

Nearly all specimens of dinosaur skin are fossilized impressions of it; the original soft tissue decayed long ago. Some specimens are mere scraps, Davis said, while others are “enough skin to wrap around a car.”

The paper is titled “Census of Dinosaur Skin Reveals Lithology May Not Be The Most Important Factor in Increased Preservation of Hadrosaurid Skin.”

Publication: Matt Davis, “Census of Dinosaur Skin Reveals Lithology May Not Be The Most Important Factor in Increased Preservation of Hadrosaurid Skin,” Acta Palaeontologica Polonica 59 (3), 2014: 601-605; doi: 10.4202/app.2012.0077

Astronomers Solve Quasar Sequence Mystery

This graph shows the distribution of about 20,000 luminous Sloan Digital Sky Survey quasars in the two-dimensional space of broad line width versus FeII strength, color-coded by the strength of the narrow [OIII] line emission. The strong horizontal trend is the main sequence of quasars driven by the efficiency of the black hole accretion, while the vertical spread of broad line width is largely due to our viewing angle to the inner region of the quasar.

New research helps solves a quasar mystery that astronomers have been puzzling over for 20 years, presenting a pathway to a better understanding of how supermassive black holes accrete matter and interplay with their environments.

Pasadena, California – Quasars are supermassive black holes that live at the center of distant massive galaxies. They shine as the most luminous beacons in the sky across the entire electromagnetic spectrum by rapidly accreting matter into their gravitationally inescapable centers. New work from Carnegie’s Hubble Fellow Yue Shen and Luis Ho of the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University solves a quasar mystery that astronomers have been puzzling over for 20 years. Their work, published in the September 11 issue of Nature, shows that most observed quasar phenomena can be unified with two simple quantities: one that describes how efficiently the hole is being fed, and the other that reflects the viewing orientation of the astronomer.

Quasars display a broad range of outward appearances when viewed by astronomers, reflecting the diversity in the conditions of the regions close to their centers. But despite this variety, quasars have a surprising amount of regularity in their quantifiable physical properties, which follow well-defined trends (referred to as the “main sequence” of quasars) discovered more than 20 years ago. Shen and Ho solved a two-decade puzzle in quasar research: What unifies these properties into this main sequence?

Using the largest and most-homogeneous sample to date of over 20,000 quasars from the Sloan Digital Sky Survey, combined with several novel statistical tests, Shen and Ho were able to demonstrate that one particular property related to the accretion of the hole, called the Eddington ratio, is the driving force behind the so-called main sequence. The Eddington ratio describes the efficiency of matter fueling the black hole, the competition between the gravitational force pulling matter inward and the luminosity driving radiation outward. This push and pull between gravity and luminosity has long been suspected to be the primary driver behind the so-called main sequence, and their work at long last confirms this hypothesis.

Of additional importance, they found that the orientation of an astronomer’s line-of-sight when looking down into the black hole’s inner region plays a significant role in the observation of the fast-moving gas innermost to the hole, which produces the broad emission lines in quasar spectra. This changes scientists’ understanding of the geometry of the line-emitting region closest to the black hole, a place called the broad-line region: the gas is distributed in a flattened, pancake-like configuration. Going forward, this will help astronomers improve their measurements of black hole masses for quasars.

“Our findings have profound implications for quasar research. This simple unification scheme presents a pathway to better understand how supermassive black holes accrete matter and interplay with their environments,” Shen said.

“And better black hole mass measurements will benefit a variety of applications in understanding the cosmic growth of supermassive black holes and their place in galaxy formation,” Ho added.

Publication: Yue Shen & Luis C. Ho, “The diversity of quasars unified by accretion and orientation,” Nature 513, 210–213 (11 September 2014); doi:10.1038/nature13712

New Nanotechnology Aids in Electron Cooling Without External Sources

A chip, which contains nanoscale structures that enable electron cooling at room temperature, is pictured.

Using a nanoscale structure that consisted of a sequential array of a source electrode, a quantum well, a tunneling barrier, a quantum dot, another tunneling barrier, and a drain electrode, researchers were able to suppress electron excitation and cool electrons to -228 °C without external means at room temperature.

A team of researchers has discovered a way to cool electrons to -228 °C without external means and at room temperature, an advancement that could enable electronic devices to function with very little energy.

The process involves passing electrons through a quantum well to cool them and keep them from heating.

The team details its research in “Energy-filtered cold electron transport at room temperature,” which is published in Nature Communications on Wednesday, September 10.

“We are the first to effectively cool electrons at room temperature. Researchers have done electron cooling before, but only when the entire device is immersed into an extremely cold cooling bath,” said Seong Jin Koh, an associate professor at UT Arlington in the Materials Science & Engineering Department, who has led the research. “Obtaining cold electrons at room temperature has enormous technical benefits. For example, the requirement of using liquid helium or liquid nitrogen for cooling electrons in various electron systems can be lifted.”

Electrons are thermally excited even at room temperature, which is a natural phenomenon. If that electron excitation could be suppressed, then the temperature of those electrons could be effectively lowered without external cooling, Koh said.

The team used a nanoscale structure – which consists of a sequential array of a source electrode, a quantum well, a tunneling barrier, a quantum dot, another tunneling barrier, and a drain electrode – to suppress electron excitation and to make electrons cold.

Cold electrons promise a new type of transistor that can operate at extremely low-energy consumption. “Implementing our findings to fabricating energy-efficient transistors is currently under way,” Koh added.

Khosrow Behbehani, dean of the UT Arlington College of Engineering, said this research is representative of the University’s role in fostering innovations that benefit the society, such as creating energy-efficient green technologies for current and future generations.

“Dr. Koh and his research team are developing real-world solutions to a critical global challenge of utilizing the energy efficiently and developing energy-efficient electronic technology that will benefit us all every day,” Behbehani said. “We applaud Dr. Koh for the results of this research and look forward to future innovations he will lead.”

Usha Varshney, program director in the National Science Foundation’s Directorate for Engineering, which funded the research, said the research findings could be vast.

“When implemented in transistors, these research findings could potentially reduce energy consumption of electronic devices by more than 10 times compared to the present technology,” Varshney said. “Personal electronic devices such as smart phones, iPads, etc., can last much longer before recharging.”

In addition to potential commercial applications, there are many military uses for the technology. Batteries weigh a lot, and less power consumption means reducing the battery weight of electronic equipment that soldiers are carrying, which will enhance their combat capability. Other potential military applications include electronics for remote sensors, unmanned aerial vehicles and high-capacity computing in remote operations.

Future research could include identifying key elements that will allow electrons to be cooled even further. The most important challenge of this future research is to keep the electron from gaining energy as it travels across device components. This would require research into how energy-gaining pathways could be effectively blocked.

Co-authors of the paper are Pradeep Bhadrachalam, Ramkumar Subramanian, Vishva Ray and Liang-Chieh Ma from UT Arlington, and Weichao Wang, Prof. Jiyoung Kim and Prof. Kyeongjae Cho from UT Dallas who also were part of the research team.

Funding from the National Science Foundation (grant numbers 0449958 and 0925997) and the Office of Naval Research (grant number N00014-12-1-0492) supported the research.

Kepler Data Helps Pinpoint ‘Venus Zone’ Around Stars

Despite being similarly sized, Earth (represented by the right-half of this image) and Venus (represented by the left half), have vastly different surface conditions. Credit: NASA/JPL-Caltech/Ames

Using data from the Kepler Space Telescope, astronomers have defined the inner and outer edges of the “Venus Zone” – the point at which a planet’s atmosphere would experience runaway greenhouse-gas effects like those seen on Venus.

San Francisco State University astronomer Stephen Kane and a team of researchers presented today the definition of a “Venus Zone,” the area around a star in which a planet is likely to exhibit the unlivable conditions found on the planet Venus.

The research will help astronomers determine which planets discovered with NASA’s Kepler telescope — which has a primary mission of finding habitable planets similar to Earth — are actually more analogous to Earth’s similarly-sized sister planet. Knowing how common Venus-like planets are elsewhere will also help astronomers understand why Earth’s atmosphere evolved in ways vastly different from its neighbor.

“We believe the Earth and Venus had similar starts in terms of their atmospheric evolution,” said Kane, an assistant professor of physics and astronomy at SF State and lead author of the study published online today. “Something changed at one point, and the obvious difference between the two is proximity to the Sun.”

San Francisco State University astronomer Stephen Kane defines the “Venus Zone,” an area around a star in which a planet is likely to exhibit the unlivable conditions found on the planet Venus.

The Kepler telescope is used to find planets outside our solar system, called exoplanets, located within or near the habitable zone in which a planet can hold liquid water on its surface. Earlier this year, Kane was part of an international team of researchers that discovered one such planet orbiting the dwarf star Kepler-186. The main way this search is conducted, however, is by looking for exoplanets that are roughly the same size as Earth. That, according to Kane, poses a problem because our own solar system contains two planets of the same size — Earth and Venus — that have vastly different atmospheric and surface conditions.

“The Earth is Dr. Jekyll and Venus is Mr. Hyde, and you can’t distinguish between the two based only on size,” said Kane, who runs a website tracking known exoplanets. “So the question then is how do you define those differences, and how many ‘Venuses’ is Kepler actually finding?”

Kane and his fellow researchers at Penn State University and the NASA Goddard Space Flight Center in Maryland used “solar flux” — or the amount of a star’s energy that a planet receives — to define the inner and outer edges of the Venus Zone. The point at which a planet’s atmosphere would experience runaway greenhouse-gas effects like those seen on Venus — a point located just inside Earth’s orbit in our solar system — forms the outer boundary. The point at which the planet’s atmosphere would be completely eroded away by the stellar energy marks the inner boundary.

This graphic shows the location of the “Venus Zone,” the area around a star in which a planet is likely to exhibit atmospheric and surface conditions similar to the planet Venus. Credit: Chester Harman, Pennsylvania State University

If Kepler astronomers discover a planet that is similar in size to Earth but located within the solar-flux range that makes up the Venus Zone, that could be a clue the planet is more like Venus than Earth, and therefore is uninhabitable. Future space-based telescopes will allow researchers to begin receiving data on these exoplanets’ atmospheres, helping them confirm whether they are “Venuses” or “Earths.”

“If we find all of these planets in the Venus Zone have a runaway greenhouse-gas effect, then we know that the distance a planet is from its star is a major determining factor,” Kane added. “That’s helpful to understanding the history between Venus and Earth.”

Future research will look at whether the amount of carbon in a planet’s atmosphere impacts the boundaries of the Venus Zone, for example by pushing the outer boundary farther away from the star for planets with greater concentrations of carbon.

“This is ultimately about putting our solar system in context,” according to Kane. “We want to know if various aspects of our solar system are rare or common.”

“On the frequency of potential Venus analogs from Kepler data” by Stephen R. Kane, Ravi Kumar Kopparapu and Shawn D. Domagal-Goldman has been accepted for publication in an upcoming issue of the Astrophysical Journal Letters.

Graphene Paint Makes Impermeable and Chemically Resistant Coatings

Photograph demonstrating water permeation through a brick (~20 cm long) with and without VC-RGO coating. Brick without the graphitic coating rapidly absorbs water but it can stay on top of the VC-RGO coated part for many hours. Credit:Y. Su, et al. doi:10.1038/ncomms5843

New research from the University of Manchester demonstrates how a thin layer of graphene paint can make impermeable and chemically resistant coatings, which could be used for packaging to keep food fresh for longer and protect metal structures against corrosion.

The surface of graphene, a one atom thick sheet of carbon, can be randomly decorated with oxygen to create graphene oxide; a form of graphene that could have a significant impact on the chemical, pharmaceutical and electronic industries. Applied as paint, it could provide an ultra-strong, non-corrosive coating for a wide range of industrial applications.

Graphene oxide solutions can be used to paint various surfaces ranging from glass to metals to even conventional bricks. After a simple chemical treatment, the resulting coatings behave like graphite in terms of chemical and thermal stability but become mechanically nearly as tough as graphene, the strongest material known to man.

The team led by Dr Rahul Nair and Nobel laureate Sir Andre Geim demonstrated previously that multilayer films made from graphene oxide are vacuum tight under dry conditions but, if expose to water or its vapor, act as molecular sieves allowing passage of small molecules below a certain size. Those findings could have huge implications for water purification.

This contrasting property is due to the structure of graphene oxide films that consist of millions of small flakes stacked randomly on top of each other but leave nano-sized capillaries between them. Water molecules like to be inside these nanocapillaries and can drag small atoms and molecules along.

In an article published in Nature Communications this week, the University of Manchester team shows that it is possible to tightly close those nanocapillaries using simple chemical treatments, which makes graphene films even stronger mechanically as well as completely impermeable to everything: gases, liquids or strong chemicals. For example, the researchers demonstrate that glassware or copper plates covered with graphene paint can be used as containers for strongly corrosive acids.

The exceptional barrier properties of graphene paint have already attracted interest from many companies who now collaborate with The University of Manchester on development of new protective and anticorrosion coatings.

Dr Nair said “Graphene paint has a good chance to become a truly revolutionary product for industries that deal with any kind of protection either from air, weather elements or corrosive chemicals. Those include, for example, medical, electronics and nuclear industry or even shipbuilding, to name but the few.”

Dr Yang Su, the first author in this work added: “Graphene paint can be applied to practically any material, independently of whether it’s plastic, metal or even sand. For example, plastic films coated with graphene could be of interest for medical packaging to improve shelf life because they are less permeable to air and water vapor than conventional coatings. In addition, thin layers of graphene paint are optically transparent.”

Publication: Y. Su, et al., “Impermeable barrier films and protective coatings based on reduced graphene oxide,” Nature Communications 5, Article number: 4843; doi:10.1038/ncomms5843

High-Resolution Images Reveal Surface of Comet 67P/Churyumov-Gerasimenko

In this view of the “belly” and part of the “head” of the comet, several morphologically different regions are indicated. ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

High-Resolution images taken by OSIRIS reveal a detailed scientific description of the surface of comet 67P/Churyumov-Gerasimenko.

High-resolution images of comet 67P/Churyumov-Gerasimenko reveal a unique, multifaceted world. ESA’s Rosetta spacecraft arrived at its destination about a month ago and is currently accompanying the comet as it progresses on its route toward the inner solar system. Scientists have now analyzed images of the comet’s surface taken by OSIRIS, Rosetta’s scientific imaging system, and allocated several distinct regions, each of which is defined by special morphological characteristics. This analysis provides the basis for a detailed scientific description of 67P’s surface.

“Never before have we seen a cometary surface in such detail”, says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Science in Germany. In some of the images, one pixel corresponds to 75 centimeters scale on the nucleus. “It is a historic moment, we have an unprecedented resolution to map a comet,” he adds.

With areas dominated by cliffs, depressions, craters, boulders or even parallel grooves, 67P displays a multitude of different terrains. While some of these areas appear to be quiet, others seem to be shaped by the comet’s activity. As OSIRIS images of the comet’s coma indicate, the dust that 67P casts into space is emitted there.

Jagged cliffs and prominent boulders: In this image, several of 67P’s very different surface structures become visible. The left part of the images shows the side wing of the comet’s “body”, while the right is the back of its “head”. The image was taken by OSIRIS, Rosetta’s scientific imaging system, on September 5th, 2014 from a distance of 62 kilometers. One pixel corresponds to 1.1 meters. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

“This first map is, of course, only the beginning of our work,” says Sierks. “At this point, nobody truely understands, how the morphological variations we are currently witnessing came to be.” As both 67P and Rosetta travel closer to the Sun in the next months, the OSIRIS team will monitor the surface looking for changes. While the scientists do not expect the borderlines of the comet’s regions to vary dramatically, even subtle transformations of the surface may help to explain how cometary activity created such a breathtaking world. The maps will also offer valuable insights for Rosetta’s Lander Team and the Rosetta orbiter scientists to determine a primary and backup landing site from the earlier preselection of five candidates.