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Supermassive Black Hole Seeds Could Be Revealed by Gravitational Waves
June 27th, 2016By Alton Parrish.
Gravitational waves captured by space-based detectors could help identify the origins of supermassive black holes, according to new computer simulations of the Universe.
Scientists led by Durham University’s Institute for Computational Cosmology ran the huge cosmological simulations that can be used to predict the rate at which gravitational waves caused by collisions between the monster black holes might be detected.
The amplitude and frequency of these waves could reveal the initial mass of the seeds from which the first black holes grew since they were formed 13 billion years ago and provide further clues about what caused them and where they formed, the researchers said.
RAS National Astronomy Meeting
The research was presented today (Monday, June 27, 2016) at the Royal Astronomical Society’s National Astronomy Meeting in Nottingham, UK. It was funded by the Science and Technology Facilities Council, the European Research Council and the Belgian Interuniversity Attraction Poles Programme.
Gas and stars in a slice of the EAGLE simulations at the present day. The intensity shows the gas density, while the color encodes the gas temperature. Researchers used the EAGLE simulations to predict the rate at which gravitational waves caused by collisions between supermassive black holes might be detected.
The study combined simulations from the EAGLE project – which aims to create a realistic simulation of the known Universe inside a computer – with a model to calculate gravitational wave signals.
Two detections of gravitational waves caused by collisions between supermassive black holes should be possible each year using space-based instruments such as the Evolved Laser Interferometer Space Antenna (eLISA) detector that is due to launch in 2034, the researchers said.
In February the international LIGO and Virgo collaborations announced that they had detected gravitational waves for the first time using ground-based instruments and in June reported a second detection.
Supermassive black holes
As eLISA will be in space – and will be at least 250,000 times larger than detectors on Earth – it should be able to detect the much lower frequency gravitational waves caused by collisions between supermassive black holes that are up to a million times the mass of our sun.
13.8 billion years of evolution of the gas in the EAGLE simulations. The intensity shows the gas density, while the colour encodes the gas temperature. Researchers used EAGLE simulations to predict the rate at which gravitational waves caused by collisions between supermassive black holes might be detected.
Current theories suggest that the seeds of these black holes were the result of either the growth and collapse of the first generation of stars in the Universe; collisions between stars in dense stellar clusters; or the direct collapse of extremely massive stars in the early Universe.
As each of these theories predicts different initial masses for the seeds of supermassive black hole seeds, the collisions would produce different gravitational wave signals.
This means that the potential detections by eLISA could help pinpoint the mechanism that helped create supermassive black holes and when in the history of the Universe they formed.
Gravitational waves
Lead author Jaime Salcido, PhD student in Durham University’s Institute for Computational Cosmology, said: “Understanding more about gravitational waves means that we can study the Universe in an entirely different way.
“These waves are caused by massive collisions between objects with a mass far greater than our sun.
“By combining the detection of gravitational waves with simulations we could ultimately work out when and how the first seeds of supermassive black holes formed.”
13.8 billion years of evolution of the dark matter in the EAGLE simulations. The intensity shows the density of dark matter. Researchers used EAGLE simulations to predict the rate at which gravitational waves caused by collisions between supermassive black holes might be detected.
Co- author Professor Richard Bower, of Durham University’s Institute for Computational Cosmology, added: “Black holes are fundamental to galaxy formation and are thought to sit at the centre of most galaxies, including our very own Milky Way.
“Discovering how they came to be where they are is one of the unsolved problems of cosmology and astronomy.
“Our research has shown how space based detectors will provide new insights into the nature of supermassive black holes.”
Detecting gravitational waves in space
Gravitational waves were first predicted 100 years ago by Albert Einstein as part of his Theory of General Relativity.
The waves are concentric ripples caused by violent events in the Universe that squeeze and stretch the fabric of space time but most are so weak they cannot be detected.
LIGO detected gravitational waves using ground-based instruments, called interferometers, that use laser beams to pick up subtle disturbances caused by the waves.
eLISA will work in a similar way, detecting the small changes in distances between three satellites that will orbit the sun in a triangular pattern connected by beams from lasers in each satellite.
In June it was reported that the LISA Pathfinder, the forerunner to eLISA, had successfully demonstrated the technology that opens the door to the development of a large space observatory capable of detecting gravitational waves in space.
* Durham’s researchers will show how they use supercomputer simulations to test how galactic ingredients and violent events combine to shape the life history of galaxies when they exhibit at the Royal Society Summer Science Exhibition in London from 4 to 10 July, 2016.
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Eating Air and Making Fuel
June 26th, 2016
By Alton Parrish.
All life on the planet relies, in one way or another, on a process called carbon fixation: the ability of plants, algae and certain bacteria to “pump” carbon dioxide (CO2) from the environment, add solar or other energy and turn it into the sugars that are the required starting point needed for life processes.
At the top of the food chain are different organisms (some of which think, mistakenly, that they are “more advanced”) that use the opposite means of survival: they eat sugars (made by photosynthetic plants and microorganisms) and then release carbon dioxide into the atmosphere. This means of growth is called “heterotrophism.” Humans are, of course, heterotrophs in the biological sense because the food they consume originates from the carbon fixation processes of nonhuman producers.
Is it possible to “reprogram” an organism that is found higher in the food chain, which consumes sugar and releases carbon dioxide, so that it will consume carbon dioxide from the environment and produce the sugars it needs to build its body mass? That is just what a group of Weizmann Institute of Science researchers recently did. Dr. Niv Antonovsky, who led this research in Prof. Ron Milo’s lab at the Institute’s Plant and Environmental Sciences Department, says that the ability to improve carbon fixation is crucial for our ability to cope with future challenges, such as the need to supply food to a growing population on shrinking land resources while using less fossil fuel.
The Institute scientists rose to this challenge by inserting the metabolic pathway for carbon fixation and sugar production (the so called Calvin cycle) into the bacterium E. coli, a known “consumer” organism that eats sugar and releases carbon dioxide.
The metabolic pathway for carbon fixation is well known, and Milo and his group reckoned that, with proper planning, they would be able to attach the genes containing the information for building it into the bacterium’s genome. Yet the main enzyme used in plants to fix carbon, RuBisCO, utilizes as a substrate for the CO2 fixation reaction a metabolite which is toxic for the bacterial cells. Thus the design had to include precisely regulating the expression levels of the various genes across this multistep pathway.
In one way the team’s well-thought-out plan was a resounding success: The bacteria did indeed produce the carbon fixation enzymes, and these were functional. But the machinery, as a whole, did not “deliver the goods.” Even though the carbon fixation machinery was expressed, the bacteria failed to use CO2 for sugar synthesis, relying instead on an external supply of sugar. “Of course, we were dealing with an organism that has evolved over millions of years to eat sugar, not CO2,” says Antonovsky. “So we turned to evolution to help us create the system we intended.”
Antonovsky, Milo and the team, including Shmuel Gleizer, Arren Bar-Even, Yehudit Zohar, Elad Herz and others, next designed tanks called “chemostats,” in which they grew the bacteria, gradually nudging them into developing an appetite for CO2. Initially, along with ample bubbles of CO2, the bacteria in the tanks were offered a large amount of pyruvate, which is an energy source, as well as barely enough sugar to survive. Thus, by changing the conditions of their environment and stressing them, the scientists forced the bacteria to learn, by adaptation and development, to use the more abundant material in their environment. A month went by, and things remained fairly static. The bacteria seemed to not “get the hint.” But at around a month and a half, some bacteria showed signs of doing more than “just surviving.” By the third month the scientists were able to wean the evolved bacteria from the sugar and raise them on CO2 and pyruvate alone. Isotope labeling of the carbon dioxide molecules revealed that the bacteria were indeed using CO2 to create a significant portion of their body mass, including all the sugars needed to make the cell.
When the scientists sequenced the genomes of the evolved bacteria, they found many changes scattered throughout the bacterial chromosomes. “They were completely different from what we had predicted,” says Milo. “It took us two years of hard work to understand which of these are essential and to unravel the ‘logic’ involved in their evolution.” Repeating the experiment (and again waiting months) gave the scientists essential clues for identifying the mutations necessary for changing the E. coli diet from one based on sugar to one using carbon dioxide.
Milo: “The ability to program or reengineer E. coli to fix carbon could give researchers a new toolbox for studying and improving this basic process.” Although currently the bacteria release CO2 back into the atmosphere, the team envisions that in the future their insights might be applied to creating microorganisms that soak up atmospheric CO2 and convert it into stored energy or to achieving crops with carbon fixing pathways, resulting in higher yields and better adaption to feeding humanity.
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Light Packing More Data Has Potential to Increase Bandwidth by 100 Times
June 26th, 2016
By Alton Parrish.
African researchers demonstrate a 100X increase in the amount of information that can be ‘packed into light’.
The rise of big data and advances in information technology has serious implications for our ability to deliver sufficient bandwidth to meet the growing demand.
Researchers at the University of the Witwatersrand in Johannesburg, South Africa, and the Council for Scientific and Industrial Research (CSIR) are looking at alternative sources that will be able to take over where traditional optical communications systems are likely to fail in future.
In their latest research, published online today (10 June 2016) in the scientific journal, Nature, the team from South Africa and Tunisia demonstrate over 100 patterns of light used in an optical communication link, potentially increasing the bandwidth of communication systems by 100 times.
The idea was conceived by Professor Andrew Forbes from Wits University, who led the collaboration. The key experiment was performed by Dr Carmelo Rosales-Guzman, a Research Fellow in the Structured Light group in the Wits School of Physics, and Dr Angela Dudley of the CSIR, an honorary academic at Wits.
Bracing for the bandwidth ceiling Traditional optical communication systems modulate the amplitude, phase, polarisation, colour and frequency of the light that is transmitted. Yet despite these technologies, we are predicted to reach a bandwidth ceiling in the near future.
But light also has a “pattern” – the intensity distribution of the light, that is, how it looks on a camera or a screen.
Since these patterns are unique, they can be used to encode information:
pattern 1 = channel 1 or the letter A,
pattern 2 = channel 2 or the letter B, and so on.
What does this mean?
That future bandwidth can be increased by precisely the number of patterns of light we are able to use.
Ten patterns mean a 10x increase in existing bandwidth, as 10 new channels would emerge for data transfer.
At the moment modern optical communication systems only use one pattern. This is due to technical hurdles in how to pack information into these patterns of light, and how to get the information back out again.
How the research was done In this latest work, the team showed data transmission with over 100 patterns of light, exploiting three degrees of freedom in the process.They used digital holograms written to a small liquid crystal display (LCD) and showed that it is possible to have a hologram encoded with over 100 patterns in multiple colours.
“This is the highest number of patterns created and detected on such a device to date, far exceeding the previous state-of-the-art,” says Forbes.
One of the novel steps was to make the device ‘colour blind’, so the same holograms can be used to encode many wavelengths.
According to Rosales-Guzman to make this work “100 holograms were combined into a single, complex hologram. Moreover, each sub-hologram was individually tailored to correct for any optical aberrations due to the colour difference, angular offset and so on”.
What’s next?
The next stage is to move out of the laboratory and demonstrate the technology in a real-world system.
“We are presently working with a commercial entity to test in just such an environment,” says Forbes. The approach of the team could be used in both free-space and optical fibre networks.
About the projectThe first experiments on the topic were carried out by Abderrahmen Trichili of Sup’Com (Tunisia) as a visiting student to South Africa as part of an African Laser Centre funded research project. The other team members included Bienvenu Ndagano (Wits), Dr Amine Ben Salem (Sup’Com) and Professor Mourad Zghal (Sup’Com), all of who contributed significantly to the work.
This project was supported by the African Laser Centre, a virtual centre funded by the South African Department of Science and Technology (DST) to support research collaborations between African countries in the field of photonics.
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Probing Giant Planets’ Dark Hydrogen
June 24th, 2016By Alton Parrish.
Hydrogen is the most-abundant element in the universe. It’s also the simplest–sporting only a single electron in each atom. But that simplicity is deceptive, because there is still so much we have to learn about hydrogen.
One of the biggest unknowns is its transformation under the extreme pressures and temperatures found in the interiors of giant planets, where it is squeezed until it becomes liquid metal, capable of conducting electricity. New work published in Physical Review Letters by Carnegie’s Alexander Goncharov and University of Edinburgh’s Stewart McWilliams measures the conditions under which hydrogen undergoes this transition in the lab and finds an intermediate state between gas and metal, which they’re calling “dark hydrogen.”
On the surface of giant planets like Jupiter, hydrogen is a gas. But between this gaseous surface and the liquid metal hydrogen in the planet’s core lies a layer of dark hydrogen, according to findings gleaned from the team’s lab mimicry.
This is an illustration of the layer of dark hydrogen the team’s lab mimicry indicates would be found beneath the surface of gas giant planets like Jupiter
Using a laser-heated diamond anvil cell to create the conditions likely to be found in gas giant planetary interiors, the team probed the physics of hydrogen under a range of pressures from 10,000 to 1.5 million times normal atmospheric pressure and up to 10,000 degrees Fahrenheit.
They discovered this unexpected intermediate phase, which does not reflect or transmit visible light, but does transmit infrared radiation, or heat.
“This observation would explain how heat can easily escape from gas giant planets like Saturn,” explained Goncharov.
They also found that this intermediate dark hydrogen is somewhat metallic, meaning it can conduct an electric current, albeit poorly. This means that it could play a role in the process by which churning metallic hydrogen in gas giant planetary cores produces a magnetic field around these bodies, in the same way that the motion of liquid iron in Earth’s core created and sustains our own magnetic field.
“This dark hydrogen layer was unexpected and inconsistent with what modeling research had led us to believe about the change from hydrogen gas to metallic hydrogen inside of celestial objects,” Goncharov added.
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New Dark Spot on Neptune Confirmed
June 24th, 2016By Alton Parrish.
New images obtained on May 16, 2016, by NASA’s Hubble Space Telescope confirm the presence of a dark vortex in the atmosphere of Neptune. Though similar features were seen during the Voyager 2 flyby of Neptune in 1989 and by the Hubble Space Telescope in 1994, this vortex is the first one observed on Neptune in the 21st century.
The discovery was announced on May 17, 2016, in a Central Bureau for Astronomical Telegrams (CBAT) electronic telegram by University of California at Berkeley research astronomer Mike Wong, who led the team that analyzed the Hubble data.
Neptune’s dark vortices are high-pressure systems and are usually accompanied by bright “companion clouds,” which are also now visible on the distant planet. The bright clouds form when the flow of ambient air is perturbed and diverted upward over the dark vortex, causing gases to likely freeze into methane ice crystals. “Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains,” Wong said. “And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth.”
Beginning in July 2015, bright clouds were again seen on Neptune by several observers, from amateurs to astronomers at the W. M. Keck Observatory in Hawaii. Astronomers suspected that these clouds might be bright companion clouds following an unseen dark vortex. Neptune’s dark vortices are typically only seen at blue wavelengths, and only Hubble has the high resolution required for seeing them on distant Neptune.
In September 2015, the Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble Space Telescope project that annually captures global maps of the outer planets, revealed a dark spot close to the location of the bright clouds, which had been tracked from the ground. By viewing the vortex a second time, the new Hubble images confirm that OPAL really detected a long-lived feature. The new data enabled the team to create a higher-quality map of the vortex and its surroundings.
Neptune’s dark vortices have exhibited surprising diversity over the years, in terms of size, shape, and stability (they meander in latitude, and sometimes speed up or slow down). They also come and go on much shorter timescales compared to similar anticyclones seen on Jupiter; large storms on Jupiter evolve over decades.
Planetary astronomers hope to better understand how dark vortices originate, what controls their drifts and oscillations, how they interact with the environment, and how they eventually dissipate, according to UC Berkeley doctoral student Joshua Tollefson, who was recently awarded a prestigious NASA Earth and Space Science Fellowship to study Neptune’s atmosphere. Measuring the evolution of the new dark vortex will extend knowledge of both the dark vortices themselves, as well as the structure and dynamics of the surrounding atmosphere.
The team, led by Wong, also included the OPAL team (Wong, Amy Simon, and Glenn Orton), UC Berkeley collaborators (Imke de Pater, Joshua Tollefson, and Katherine de Kleer), Heidi Hammel (AURA), Statia Luszcz-Cook (AMNH), Ricardo Hueso and Agustin Sánchez-Lavega (Universidad del Pais Vasco), Marc Delcroix (Société Astronomique de France), Larry Sromovsky and Patrick Fry (University of Wisconsin), and Christoph Baranec (University of Hawaii).
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Shredded Star Provides Close-up of ‘Killer’ Black Hole
June 23rd, 2016
By Alton Parrish.
Some 3.9 billion years ago in the heart of a distant galaxy, the intense tidal pull of a monster black hole shredded a star that passed too close. When X-rays produced in this event first reached Earth on March 28, 2011, they were detected by NASA’s Swift satellite, which notified astronomers around the world. Within days, scientists concluded that the outburst, now known as Swift J1644+57, represented both the tidal disruption of a star and the sudden flare-up of a previously inactive black hole.
NASA Goddard astronomer Erin Kara discusses the discovery of X-ray echoes from Swift J1644+57, a black hole that shattered a passing star. X-rays produced by flares near this million-solar-mass black hole bounced off the nascent accretion disk and revealed its structure.
Now astronomers using archival observations from Swift, the European Space Agency’s (ESA) XMM-Newton observatory and the Japan-led Suzaku satellite have identified the reflections of X-ray flares erupting during the event. Led by Erin Kara, a postdoctoral researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park (UMCP), the team has used these light echoes, or reverberations, to map the flow of gas near a newly awakened black hole for the first time.
“While we don’t yet understand what causes X-ray flares near the black hole, we know that when one occurs we can detect its echo a couple of minutes later, once the light has reached and illuminated parts of the flow,” Kara explained. “This technique, called X-ray reverberation mapping, has been previously used to explore stable disks around black holes, but this is the first time we’ve applied it to a newly formed disk produced by a tidal disruption.”
In this artist’s rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole
Stellar debris falling toward a black hole collects into a rotating structure called an accretion disk. There the gas is compressed and heated to millions of degrees before it eventually spills over the black hole’s event horizon, the point beyond which nothing can escape and astronomers cannot observe. The Swift J1644+57 accretion disk was thicker, more turbulent and more chaotic than stable disks, which have had time to settle down into an orderly routine. The researchers present the findings in a paper published online in the journal Nature on Wed., June 22.
One surprise from the study is that high-energy X-rays arise from the inner part of the disk. Astronomers had thought most of this emission originated from a narrow jet of particles accelerated to near the speed of light. In blazars, the most luminous galaxy class powered by supermassive black holes, jets produce most of the highest-energy emission.
“We do see a jet from Swift J1644, but the X-rays are coming from a compact region near the black hole at the base of a steep funnel of inflowing gas we’re looking down into,” said co-author Lixin Dai, a postdoctoral researcher at UMCP. “The gas producing the echoes is itself flowing outward along the surface of the funnel at speeds up to half the speed of light.”
X-rays originating near the black hole excite iron ions in the whirling gas, causing them to fluoresce with a distinctive high-energy glow called iron K-line emission. As an X-ray flare brightens and fades, the gas follows in turn after a brief delay depending on its distance from the source.
“Direct light from the flare has different properties than its echo, and we can detect reverberations by monitoring how the brightness changes across different X-ray energies,” said co-author Jon Miller, a professor of astronomy at the University of Michigan in Ann Arbor.
Swift J1644+57 is one of only three tidal disruptions that have produced high-energy X-rays, and to date it remains the only event caught at the peak of this emission. These star shredding episodes briefly activate black holes astronomers wouldn’t otherwise know about. For every black hole now actively accreting gas and producing light, astronomers think nine others are dormant and dark. These quiescent black holes were active when the universe was younger, and they played an important role in how galaxies evolved. Tidal disruptions therefore offer a glimpse of the silent majority of supersized black holes.
Images from Swift’s Ultraviolet/Optical (white, purple) and X-Ray telescopes (yellow and red) were combined in this composite of Swift J1644+57, an X-ray outburst astronomers classify as a tidal disruption event. The event is seen only in the X-ray image, which is a 3.4-hour exposure taken on March 28, 2011. The outburst was triggered when a passing star came too close to a supermassive black hole. The star was torn apart, and much of the gas fell toward the black hole. To date, this is the only tidal disruption event emitting high-energy X-rays that astronomers have caught at peak luminosity.
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“If we only look at active black holes, we might be getting a strongly biased sample,” said team member Chris Reynolds, a professor of astronomy at UMCP. “It could be that these black holes all fit within some narrow range of spins and masses. So it’s important to study the entire population to make sure we’re not biased.”
The researchers estimate the mass of the Swift J1644+57 black hole at about a million times that of the sun but did not measure its spin. With future improvements in understanding and modeling accretion flows, the team thinks it may be possible to do so.
ESA’s XMM-Newton satellite was launched in December 1999 from Kourou, French Guiana. NASA funded elements of the XMM-Newton instrument package and provides the NASA Guest Observer Facility at Goddard, which supports use of the observatory by U.S. astronomers. Suzaku operated from July 2005 to August 2015 and was developed at the Japanese Institute of Space and Astronautical Science, which is part of the Japan Aerospace Exploration Agency, in collaboration with NASA and other Japanese and U.S. institutions.
NASA’s Swift satellite was launched in November 2004 and is managed by Goddard. It is operated in collaboration with Penn State University in University Park, the Los Alamos National Laboratory in New Mexico, and Orbital Sciences Corp. in Dulles, Virginia, with international collaborators in the U.K., Italy, Germany and Japan.
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NRL Astrophysicist Probes Theory Of Black-Hole Accretion
June 23rd, 2016
By Alton parrish.
Utilizing the Atacama Large Millimeter/submillimeter Array (ALMA), one of the most powerful telescopes in the world, U.S. Naval Research Laboratory (NRL) astrophysicist Dr. Tracy Clarke and an international team of researchers have peered into the feeding habits of a supermassive black hole and witnessed the first evidence of a new diet. The black hole, whose mass is nearly 300 million times that of our sun, is on the verge of gulping down massive clumps of cold gas which each contain as much material as a million suns.
Lurking in the heart of the galaxy cluster Abell 2597, located nearly one billion light years from Earth in the constellation Aquarius, astronomers track several massive gas clouds that are raining down on the central supermassive black hole. The complex cosmic weather, as illustrated in this artist’s concept, includes condensed clouds of cold molecular gas in the galaxy core that cast shadows seen in the ALMA observations. These clouds condense out of the surrounding hot intracluster medium and fuel ‘cold, chaotic’ accretion (or feeding) of the central supermassive black hole. This fuel leads to massive outbursts that drive the powerful radio jets out into the surrounding medium.
Previously, astronomers generally believed that supermassive black holes at the centers of galaxies slowly grazed on a steadfast diet of hot ionized gas from the galaxy’s halo. The new ALMA observations show that under the right intergalactic conditions, the black hole can instead feed on a chaotic downpour of cold, clumpy clouds that have condensed out of the hot gas and plummeted into the heart of the galaxy where the supermassive black hole resides. These new observations — recently published in a Natureletter led by Dr. Grant Tremblay, Yale Center for Astronomy and Astrophysics — will help recast astronomers models of how supermassive black holes grow through a process known as accretion.
The team of astronomers used ALMA to study an unusually bright cluster of individual galaxies, collectively referred to as Abell 2597, in hopes of mapping the spatial structure and velocity of the cold gas in the system. Earlier work by Clarke revealed that the hot gas in the core of this cluster is riddled with X-ray cavities excavated by powerful radio jets driven by outbursts from the central supermassive black hole. The ALMA observations were aimed at searching for evidence that the powerful radio jets can also pull cold gas out of the cluster core to stop catastrophic runaway cooling.
“We’ve known for a long time that black holes at the heart of galaxies can launch powerful jets that travel far beyond the borders of their host galaxy but we really don’t understand how this process happens,” said Clarke. In recent years theoretical models have predicted that black holes may grow through so-called cold, chaotic accretion but unambiguous observational evidence of this form of accretion has been elusive, until now.
While studying the ALMA data on the central galaxy in Abell 2597 the team of astronomers discovered something unexpected, the distinct signature of three shadows cast by massive clouds of cold gas raining onto the central supermassive black hole. Clarke points out that these clouds fall into the core of this galaxy at close to 300 kilometers per second, adding, that “If you could travel at this speed, it would take you about two minutes to circumnavigate the Earth.”
These shadows, known as absorption features, are formed when the in-falling clouds pass in front of the bright emission from very near the black hole and block, or absorb, some of that radiation. However, it is likely that there are many more clouds that went undetected by the ALMA observations since the astronomers are only able to probe a small sightline toward the cluster core.
To put these features in perspective, Clark says, “If I were a weather forecaster covering the center of Abell 2597, my weekend forecast for a million years from now would likely be ‘cloudy with a chance of rain and explosive outbursts.'”
What Clarke is referring to, is the fact that the clouds are expected to eventually feed a massive outburst from the central supermassive black hole. The outburst will drive a new generation of radio jets into the cluster to evacuate cavities and heat the gas. Eventually this gas will cool into cold clumps and fall back into the central black hole. This ‘feedback cycle’ may be essential to maintaining a cosmic balance of heating and cooling in galaxy clusters, the most massive known objects in the Universe.
Astronomers, however, are unable to determine from a single system that these clouds will drive the next outburst and therefore plan next to use ALMA for a broader study of galaxies to determine if this black hole ‘diet’ is as widespread as theory suggests.
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New Way To Turn Waste Plastic into Fuel
June 22nd, 2016
By Alton Parrish.
A new way of recycling millions of tons of plastic garbage into liquid fuel has been devised by researchers from the University of California, Irvine and the Shanghai Institute of Organic Chemistry (SIOC) in China.
“Synthetic plastics are a fundamental part of modern life, but our use of them in large volume has created serious environmental problems,” said UCI chemist Zhibin Guan. “Our goal through this research was to address the issue of plastic pollution as well as achieving a beneficial outcome of creating a new source of liquid fuel.”
Guan and Zheng Huang, his collaborator at SIOC, together with their colleagues have figured out how to break down the strong bonds of polyethylene, the most common commercially available form of plastic. Their innovative technique centers on the use of alkanes, specific types of hydrocarbon molecules, to scramble and separate polymer molecules into other useful compounds. The team’s findings were published recently in Science Advances.
Scientists have been seeking to recycle plastic bags, bottles and other trash generated by humans with less toxic or energy intensive methods. Current approaches include using caustic chemicals known as radicals or heating the material to more than 700 degrees Fahrenheit to break down the chemical bonds of the polymers.
In this newly discovered technique, the team degrades plastics in a milder and more efficient manner through a process known as cross-alkane metathesis. The substances needed for the new method are byproducts of oil refining, so they’re readily available.
Guan said the US-China joint team is still working on a few issues to make it more efficient. That includes increasing the catalyst activity and lifetime, decreasing the cost, and developing catalytic processes to turn other plastic trash into treasure.
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Pluto Likely Has a Liquid Ocean Beneath the Ice Say Researchers
June 22nd, 2016
By Alton Parrish.
When the NASA’s New Horizons spacecraft buzzed by Pluto last year, it revealed tantalizing clues that the dwarf planet might have — or had at one time — a liquid ocean sloshing around under its icy crust. According to a new analysis led by a Brown University Ph.D. student, such an ocean likely still exists today.
The study, which used a thermal evolution model for Pluto updated with data from New Horizons, found that if Pluto’s ocean had frozen into oblivion millions or billions of years ago, it would have caused the entire planet to shrink. But there are no signs of a global contraction to be found on Pluto’s surface. On the contrary, New Horizons showed signs that Pluto has been expanding.
The New Horizons spacecraft spied extensional faults on Pluto, a sign that the dwarf planet has undergone a global expansion possibly due to the slow freezing of a subsurface ocean. A new analysis by Brown University scientists bolsters that idea, and suggests that ocean is likely still there today
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“Thanks to the incredible data returned by New Horizons, we were able to observe tectonic features on Pluto’s surface, update our thermal evolution model with new data and infer that Pluto most likely has a subsurface ocean today,” said Noah Hammond, a graduate student in Brown’s Department of Earth, Environmental and Planetary Sciences, and the study’s lead author.
The research, which Hammond coauthored with advisors Amy Barr of the Planetary Science Institute in Arizona and Brown University geologist Marc Parmentier, is in press in Geophysical Research Letters.
The pictures New Horizons sent back from its close encounter with the Kuiper Belt’s most famous denizen showed that Pluto was much more than a simple snowball in space. It has an exotic surface made from different types of ices — water, nitrogen and methane. It has mountains hundreds of meters high and a vast heart-shaped plain. It also has giant tectonic features — sinuous faults hundreds of kilometers long as deep as 4 kilometers. It was those tectonic features that got scientists thinking that a subsurface ocean was a real possibility for Pluto.
Pluto’s Big Heart
“What New Horizons showed was that there are extensional tectonic features, which indicate that Pluto underwent a period of global expansion,” Hammond said. “A subsurface ocean that was slowly freezing over would cause this kind of expansion.”
Scientists think that there may have been enough heat-producing radioactive elements within Pluto’s rocky core to melt part of the planet’s ice shell. Over time in the frigid Kuiper belt, that melted portion would eventually start to refreeze. Ice is less dense than water, so when it freezes, it expands. If Pluto had on ocean that was frozen or in the process of freezing, extensional tectonics on the surface would result, and that’s what New Horizons saw.
There aren’t many other ways on Pluto to get such features. One way might have been through a gravitational tug of war with its moon, Charon. But the active gravitational dynamics between the two have long since wound down, and some of the tectonics look fairly fresh (on a geologic timescale). So, many scientists believe that an ocean is the strongest scenario.
But if Pluto had an ocean, what is its fate today? Could the freezing process still be going on, or did the ocean freeze solid a billion years ago?
That’s where the thermal evolution model run by Hammond and his colleagues comes in. The model includes updated data from New Horizons on Pluto’s diameter and density, key parameters in understanding the dynamics in Pluto’s interior. The model showed that because of the low temperatures and high pressure within Pluto, an ocean that had completely frozen over would quickly convert from the normal ice we all know to a different phase called ice II. Ice II has a more compact crystalline structure than standard ice, so an ocean frozen to ice II would occupy a smaller volume and lead to a global contraction on Pluto, rather than an expansion.
“We don’t see the things on the surface we’d expect if there had been a global contraction,” Hammond said. “So we conclude that ice II has not formed, and therefore that the ocean hasn’t completely frozen.”
There are a few caveats, the researchers point out. The formation of ice II is dependent on the thickness of Pluto’s ice shell. Ice II only forms if the shell is 260 kilometers thick or more. If the shell is thinner than that, the ocean could have frozen without forming ice II. And if that were the case the ocean could have frozen completely without causing contraction.
However, the researchers say there’s good reason to believe that the ice shell is more than 260 kilometers. Their updated model suggests that Pluto’s ice shell is actually closer to 300 or more kilometers thick. In addition, the nitrogen and methane ices that New Horizons found on the surface bolster the case for a thick ice shell.
“Those exotic ices are actually good insulators,” Hammond said. “They may be helping Pluto from losing more of its heat to space.”
Taken together, the new model bolsters the case for an ocean environment in the furthest reaches of the solar system.
“That’s amazing to me,” Hammond said. “The possibility that you could have vast liquid water ocean habitats so far from the sun on Pluto — and that the same could also be possible on other Kuiper belt objects as well — is absolutely incredible.”
The research was supported by the NASA Earth and Space Science Fellowship (NNX13AN99H) and NASA Planetary Geology & Geophysics (NNX15AN79G).
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Need Hair, Fur, Brushes, And Bristles? Press “Print”
June 21st, 2016By Alton Parrish.
These days, it may seem as if 3-D printers can spit out just about anything, from a full-sized sports car, to edible food, to human skin. But some things have defied the technology, including hair, fur, and other dense arrays of extremely fine features, which require a huge amount of computational time and power to first design, then print.
Now researchers in MIT’s Media Lab have found a way to bypass a major design step in 3-D printing, to quickly and efficiently model and print thousands of hair-like structures. Instead of using conventional computer-aided design (CAD) software to draw thousands of individual hairs on a computer — a step that would take hours to compute — the team built a new software platform, called “Cilllia,” that lets users define the angle, thickness, density, and height of thousands of hairs, in just a few minutes.
Using the new software, the researchers designed arrays of hair-like structures with a resolution of 50 microns — about the width of a human hair. Playing with various dimensions, they designed and then printed arrays ranging from coarse bristles to fine fur, onto flat and also curved surfaces, using a conventional 3-D printer. They presented a paper detailing the results at the Association for Computing Machinery’s CHI Conference on Human Factors in Computing Systems in May.
The researchers attached the 3-D printed hairs to a ring.
Could the technology be used to print wigs and hair extensions? Possibly, say the researchers. But that’s not their end goal. Instead, they’re seeing how 3-D-printed hair could perform useful tasks such as sensing, adhesion, and actuation.
To demonstrate adhesion, the team printed arrays that act as Velcro-like bristle pads. Depending on the angle of the bristles, the pads can stick to each other with varying forces. For sensing, the researchers printed a small furry rabbit figure, equipped with LED lights that light up when a person strokes the rabbit in certain directions.
And to see whether 3-D-printed hair can help actuate, or move objects, the team fabricated a weight-sorting table made from panels of printed hair with specified angles and heights. As a small vibration source shook the panels, the hairs were able to move coins across the table, sorting them based on the coins’ weight and the vibration frequency.
Jifei Ou, a graduate student in media arts and sciences, says the work is inspired by hair-like structures in nature, which provide benefits such as warmth, in the case of human hair, and movement, in the case of cilia, which help remove dust from the lungs.
“It’s very inspiring to see how these structures occur in nature and how they can achieve different functions,” Ou says. “We’re just trying to think how can we fully utilize the potential of 3-D printing, and create new functional materials whose properties are easily tunable and controllable.”
Ou is lead author on the paper, which also includes graduate students Gershon Dublon and Chin-Yi Cheng; Felix Heibeck, a former research assistant; Hiroshi Ishii, the Jerome B. Wiesner Professor in media arts and sciences; and Karl Willis of Addimation, Inc.
A software challenge
The resolution of today’s 3-D printers is “already pretty high,” Ou says. “But we’re not using [3-D printing] to the best of its capabilities.”
The team looked for things to print that would test the technology’s limits. Hair, as it turns out, was the perfect subject.
“[Hair] comes with a challenge that is not on the hardware, but on the software side,” Ou says.
The 3-D printed hairs act like Velcro.
To 3-D-print hair using existing software, designers would have to model hair in CAD, drawing out each individual strand, then feed the drawing through a slicer program that represents each hair’s contour as a mesh of tiny triangles. The program would then create horizontal cross sections of the triangle mesh, and translate each cross section into pixels, or a bitmap, that a printer could then print out, layer by layer.
Ou says designing a stamp-sized array of 6,000 hairs using this process would take several hours to process.
“If you were to load this file into a normal slicing program, it would crash the program,” he says.
Hair pixels
To design hair, the researchers chose to do away with CAD modeling entirely. Instead, they built a new software platform to model first a single hair and then an array of hairs, and finally to print arrays on both flat and curved surfaces.
The researchers modeled a single hair by representing an elongated cone as a stack of fewer and fewer pixels, from the base to the top. To change the hair’s dimensions, such as its height, angle, and width, they simply changed the arrangement of pixels in the cone.
To scale up to thousands of hairs on a flat surface, Ou and his team used Photoshop to generate a color mapping technique. They used three colors — red, green, and blue — to represent three hair parameters — height, width, and angle. For example, to make a circular patch of hair with taller strands around the rim, they drew a red circle and changed the color gradient in such a way that darker hues of red appeared around the circle’s rim, denoting taller hairs. They then developed an algorithm to quickly translate the color map into a model of a hair array, which they then fed to a 3-D printer.
Using these techniques, the team printed pads of Velcro-like bristles, and paintbrushes with varying textures and densities.
Vibrations cause a piece of metal to move across the 3-D printed hairs
Printing hair on curved surfaces proved trickier. To do this, the team first imported a CAD drawing of a curved surface, such as a small rabbit, then fed the model through a slicing program to generate a triangle mesh of the rabbit shape. They then developed an algorithm to locate the center of each triangle’s base, then virtually drew a line out, perpendicular to the triangle’s base, to represent a single hair. Doing this for every triangle in the mesh created a dense array of hairs running perpendicular to the rabbit’s curved surface.
The researchers then used their color mapping techniques to quickly customize the rabbit hair’s thickness and stiffness.
“With our method, everything becomes smooth and fast,” Ou says. “Previously it was virtually impossible, because who’s going to take a whole day to render a whole furry rabbit, and then take another day to make it printable?”
Among other applications, Ou says 3-D-printed hair may be used in interactive toys. To demonstrate, his team inserted an LED light into the fuzzy printed rabbit, along with a small microphone that senses vibrations. With this setup, the bunny turns green when it is petted in the correct way, and red when it is not.
“The ability to fabricate customized hair-like structures not only expands the library of 3-D-printable shapes, but also enables us to design alternative actuators and sensors,” the authors conclude in their paper. “3-D-printed hair can be used for designing everyday interactive objects.”
Kelly Schaefer, a designer at IDEO, a design consulting firm, says “this type of work expands the possibilities of 3-D printing as an industry because of the new applications it suggests.”
“Perhaps more inspiring than any single output from this team is the idea of rethinking the 3-D printing process itself and the purpose of 3-D printed objects,” says Schaefer, who was not involved in the research. “The Cilllia team has challenged some of the current constraints of 3-D printing processes, which makes me wonder what other constraints can be challenged and potentially eliminated.”
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Venus‘Electric Wind’ Can Strip Earth-like Planets of Oceans, Atmospheres
June 21st, 2016
By Alton Parrish.
Venus has an “electric wind” strong enough to remove the components of water from its upper atmosphere, which may have played a significant role in stripping Earth’s twin planet of its oceans, according to new results from ESA’s (European Space Agency) Venus Express mission by NASA-funded researchers.
“It’s amazing, shocking,” said Glyn Collinson, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We never dreamt an electric wind could be so powerful that it can suck oxygen right out of an atmosphere into space. This is something that has to be on the checklist when we go looking for habitable planets around other stars.” Collinson is lead author of a paper about this research published June 20, 2016, in the journal Geophysical Research Letters.
The space environment around a planet plays a key role in determining what molecules exist in the atmosphere — and whether the planet is habitable for life. New NASA research shows that the electric fields around Venus helped strip its atmosphere of the components needed to make water
Venus is in many ways the most like Earth in terms of its size and gravity, and there’s evidence that it once had oceans worth of water in its distant past. However, with surface temperatures around 860 F (460 C), any oceans would have long since boiled away to steam and Venus is uninhabitable today. Yet Venus’ thick atmosphere, about 100 times the pressure of Earth’s, has 10,000 to 100,000 times less water than Earth’s atmosphere. Something had to remove all that steam, and the current thinking is that much of the early steam dissociated to hydrogen and oxygen: the light hydrogen escaped, while the oxygen oxidized rocks over billions of years. Also the solar wind — a million-mile-per-hour stream of electrically conducting gas blowing from the sun — could have slowly but surely eroded the remainder of an ocean’s worth of oxygen and water from Venus’ upper atmosphere.
“We found that the electric wind, which people thought was just one small cog in a big machine, is in fact this big monster that’s capable of sucking the water from Venus by itself,” said Collinson.
Just as every planet has a gravity field, it is believed that every planet with an atmosphere is also surrounded by a weak electric field. While the force of gravity is trying to hold the atmosphere on the planet, the electric force (the same force that sticks laundry together in a drier and pushes electricity through wires) can help to push the upper layers of the atmosphere off into space. At Venus, the much faster hydrogen escapes easily, but this electric field is so strong that it can accelerate even the heavier electrically charged component of water — oxygen ions — to speeds fast enough to escape the planet’s gravity. When water molecules rise into the upper atmosphere, sunlight breaks the water into hydrogen and oxygen ions, which are then carried away by the electric field.
“If you were unfortunate enough to be an oxygen ion in the upper atmosphere of Venus then you have won a terrible, terrible lottery,” said Collinson, “You and all your ion friends will be dragged off kicking and screaming into space by an invisible hand, and nothing can save you.”
The team discovered Venus’ electric field using the electron spectrometer, a component of the ASPERA-4 instrument, aboard the ESA Venus Express. They were monitoring electrons flowing out of the upper atmosphere when it was noticed that these electrons were not escaping at their expected speeds. The team realized that these electrons had been tugged on by Venus’ potent electric field. By measuring the change in speed, the team was able to measure the strength of the field, finding it to be much stronger than anyone had expected, and at least five times more powerful than at Earth.
“We don’t really know why it is so much stronger at Venus than Earth,” said Collinson, “but, we think it might have something to do with Venus being closer to the sun, and the ultraviolet sunlight being twice as bright. It’s a challenging thing to measure and even at Earth to date all we have are upper limits on how strong it might be.”
Such information also helps us understand other worlds around the solar system.
“We’ve been studying the electrons flowing away from Titan [a moon of Saturn] and Mars as well as from Venus, and the ions they drag away to space,” said Andrew Coates, who leads the electron spectrometer team at University College London in the U.K. “The new result here shows that the electric field powering this escape is surprisingly strong at Venus compared to the other objects. This will help us understand how this universal process works.”
Another planet where the electric wind may play an important role is Mars. NASA’s MAVEN mission is currently orbiting Mars to determine what caused the Red Planet to lose much of its atmosphere and water. “We are actively hunting for Mars’ electric wind with MAVEN’s full arsenal of scientific instruments,” said Collinson. “MAVEN is a robotic detective on this four-billion-year-old mystery of where the atmosphere and oceans went, and the electric wind has long been a prime suspect.”
This is an artist’s concept of the electric wind at Venus. Rays represent the paths that oxygen and hydrogen ions take as they are pulled out of the upper atmosphere.
Taking the electric wind into account will also help astronomers improve estimates of the size and location of habitable zones around other stars. These are areas where the temperature could allow liquid water to exist on the surface of alien worlds, making them places where life might be found. Some stars emit more ultraviolet light than the sun, so if this creates stronger electric winds in any planets orbiting them, the habitable zone around such stars may be farther away and narrower than thought. “Even a weak electric wind could still play a role in water and atmospheric loss at any planet,” said Alex Glocer of NASA Goddard, a co-author on the paper. “It could act like a conveyor belt, moving ions higher in the ionosphere where other effects from the solar wind could carry them away.”
ESA’s Venus Express was launched on Nov. 9, 2005, to study the complex atmosphere of Venus. The electron spectrometer was built by the Southwest Research Institute in San Antonio, Texas, and is led by University College London. The spacecraft orbited Venus between 2006 and December 2014. After a successful mission that far exceeded its planned life, the spacecraft exhausted its fuel supply and burned up upon entry into Venus’ dense atmosphere. The research was funded by NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) mission and NASA’s Solar System Workings program.
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How Black Hole Jets Punch Out of Their Galaxies
June 20th, 2016
By Alton Parrish.
A simulation of the powerful jets generated by supermassive black holes at the centers of the largest galaxies explains why some burst forth as bright beacons visible across the universe, while others fall apart and never pierce the halo of the galaxy.
New simulations of the jets produced by rotating supermassive black holes in the cores of galaxies show how, with enough power, the corkscrewing fields (white squiggles) can force their way through surrounding gas and drill out of the galaxy, channeling hot gas into the interstellar medium (top). Less powerful jets get stalled inside the galaxy, however, their magnetic fields breaking and dumping hot gas inside and heating up the galaxy
About 10 percent of all galaxies with active nuclei — all presumed to have supermassive black holes within the central bulge — are observed to have jets of gas spurting in opposite directions from the core. The hot ionized gas is propelled by the twisting magnetic fields of the rotating black hole, which can be as large as several billion suns.
A 40-year-old puzzle was why some jets are hefty and punch out of the galaxy into intergalactic space, while others are narrow and often fizzle out before reaching the edge of the galaxy. The answer could shed light on how galaxies and their central black holes evolve, since aborted jets are thought to roil the galaxy and slow star formation, while also slowing the infall of gas that has been feeding the voracious black hole. The model could also help astronomers understand other types of jets, such as those produced by individual stars, which we see as gamma-ray bursts or pulsars.
“Whereas it was rather easy to reproduce the stable jets in simulations, it turned out to be an extreme challenge to explain what causes the jets to fall apart,” said University of California, Berkeley theoretical astrophysicist Alexander Tchekhovskoy, a NASA Einstein postdoctoral fellow, who led the project. “To explain why some jets are unstable, researchers had to resort to explanations such as red giant stars in the jets’ path loading the jets with too much gas and making them heavy and unstable so that the jets fall apart.”
This false-color image of the radio jet and lobes in the very bright radio galaxy Cygnus A is an example of the powerful jets that can be produced by supermassive black holes at the cores of large galaxies.
By taking into account the magnetic fields that generate these jets, Tchekhovskoy and colleague Omer Bromberg, a former Lyman Spitzer Jr. postdoctoral fellow at Princeton University, discovered that magnetic instabilities in the jet determine their fate. If the jet is not powerful enough to penetrate the surrounding gas, the jet becomes narrow or collimated, a shape prone to kinking and breaking. When this happens, the hot ionized gas funneled through the magnetic field spews into the galaxy, inflating a hot bubble of gas that generally heats up the galaxy.
Powerful jets, however, are broader and able to punch through the surrounding gas into the intergalactic medium. The determining factors are the power of the jet and how quickly the gas density drops off with distance, typically dependent on the mass and radius of the galaxy core.
The simulation, which agrees well with observations, explains what has become known as the Fanaroff-Riley morphological dichotomy of jets, first pointed out by Bernie Fanaroff of South Africa and Julia Riley of the U.K. in 1974.
“We have shown that a jet can fall apart without any external perturbation, just because of the physics of the jet,“ Tchekhovskoy said. He and Bromberg, who is currently at the Hebrew University of Jerusalem in Israel, will publish their simulations on June 17 in the journal Monthly Notices of the Royal Astronomical Society, a publication of Oxford University Press.
Bendable drills
The supermassive black hole in the bulging center of these massive galaxies is like a pitted olive spinning around an axle through the hole, Tchekhovskoy said. If you thread a strand of spaghetti through the hole, representing a magnetic field, then the spinning olive will coil the spaghetti like a spring. The spinning, coiled magnetic fields act like a flexible drill trying to penetrate the surrounding gas.
The simulation, based solely on magnetic field interactions with ionized gas particles, shows that if the jet is not powerful enough to punch a hole through the surrounding gas, the magnetic drill bends and, due to the magnetic kink instability, breaks. An example of this type of jet can be seen in the galaxy M87, one of the closest such jets to Earth at a distance of about 50 million light-years, and has a central black hole equal to about 6 billion suns.
“If I were to jump on top of a jet and fly with it, I would see the jet start to wiggle around because of a kink instability in the magnetic field,“ Tchekhovskoy said.“If this wiggling grows faster than it takes the gas to reach the tip, then the jet will fall apart. If the instability grows slower than it takes for gas to go from the base to the tip of the jet, then the jet will stay stable.“
The jet in the galaxy Cygnus A, located about 600 million light-years from Earth, is an example of powerful jets punching through into intergalactic space.
Tchekhovskoy argues that the unstable jets contribute to what is called black hole feedback, that is, a reaction from the material around the black hole that tends to slow its intake of gas and thus its growth. Unstable jets deposit a lot of energy within the galaxy that heats up the gas and prevents it from falling into the black hole. Jets and other processes effectively keep the sizes of supermassive black holes below about 10 billion solar masses, though UC Berkeley astronomers recently found black holes with masses near 21 billion solar masses.
Presumably these jets start and stop, lasting perhaps 10-100 million years, as suggested by images of some galaxies showing more than one jet, one of them old and tattered. Evidently, black holes go through binging cycles, interrupted in part by the occasional unstable jet that essentialy takes away their food.
The simulations were run on the Savio computer at UC Berkeley, Darter at the National Institute for Computational Sciences at the University of Tennesee, Knoxville, and Stampede, Maverick and Ranch computers at the Texas Advanced Computing Center at the University of Texas at Austin. The entire simulation took about 500 hours on 2,000 computer cores, the equivalent of 1 million hours on a standard laptop.
The researchers are improving their simulation to incorporate the smaller effects of gravity, buoyancy and the thermal pressure of the interstellar and intergalactic media.
The work was supported by NASA through Einstein Postdoctoral Fellowship grant number PF3-140115 awarded by the Chandra X-ray Center, operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060, and the National Science Foundation through an XSEDE computational time allocation TG-AST100040.
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Star Cluster Hosts an Excess of Hot Jupiters
June 20th, 2016
Alton Parrish.
An international team of astronomers have found that there are far more planets of the hot Jupiter type than expected in a cluster of stars called Messier 67. This surprising result was obtained using a number of telescopes and instruments, among them the HARPS spectrograph at ESO’s La Silla Observatory in Chile. The denser environment in a cluster will cause more frequent interactions between planets and nearby stars, which may explain the excess of hot Jupiters.
This artist’s impression video shows a hot Jupiter exoplanet orbiting close to a star in the rich old star cluster Messier 67, in the constellation of Cancer (The Crab). Astronomers have found far more such planets in the cluster than expected. This surprise result was obtained using a number of telescopes and instruments, among them the HARPS spectrograph at ESO’s La Silla Observatory in Chile. The denser environment in a cluster will cause more frequent interactions between planets and nearby stars, which may explain the excess of hot Jupiters.
A Chilean, Brazilian and European team led by Roberto Saglia at the Max-Planck-Institut für extraterrestrische Physik, in Garching, Germany, and Luca Pasquini at ESO, has spent several years collecting high-precision measurements of 88 stars in Messier 67 [1]. This open star cluster is about the same age as the Sun and it is thought that the Solar System arose in a similarly dense environment [2].
The team used HARPS, along with other instruments [3], to look for the signatures of giant planets on short-period orbits, hoping to see the tell-tale “wobble” of a star caused by the presence of a massive object in a close orbit, a kind of planet known as a hot Jupiters. This hot Jupiter signature has now been found for a total of three stars in the cluster alongside earlier evidence for several other planets.
A hot Jupiter is a giant exoplanet with a mass of more than about a third of Jupiter’s mass. They are “hot” because they are orbiting close to their parent stars, as indicated by an orbital period (their “year”) that is less than ten days in duration. That is very different from the Jupiter we are familiar with in our own Solar System, which has a year lasting around 12 Earth- years and is much colder than the Earth [4].
“We want to use an open star cluster as laboratory to explore the properties of exoplanets and theories of planet formation”, explains Roberto Saglia. “Here we have not only many stars possibly hosting planets, but also a dense environment, in which they must have formed.”
The study found that hot Jupiters are more common around stars in Messier 67 than is the case for stars outside of clusters. “This is really a striking result,” marvels Anna Brucalassi, who carried out the analysis. “The new results mean that there are hot Jupiters around some 5% of the Messier 67 stars studied — far more than in comparable studies of stars not in clusters, where the rate is more like 1%.”
This wide-field image of the sky around the old open star cluster Messier 67 was created from images forming part of the Digitized Sky Survey 2. The cluster appears as a rich grouping of stars at the centre of the picture. Messier 67 contains stars that are all about the same age, and have the same chemical composition, as the Sun.
Astronomers think it highly unlikely that these exotic giants actually formed where we now find them, as conditions so close to the parent star would not initially have been suitable for the formation of Jupiter-like planets. Rather, it is thought that they formed further out, as Jupiter probably did, and then moved closer to the parent star. What were once distant, cold, giant planets are now a good deal hotter. The question then is: what caused them to migrate inwards towards the star?
There are a number of possible answers to that question, but the authors conclude that this is most likely the result of close encounters with neighbouring stars, or even with the planets in neighbouring solar systems, and that the immediate environment around a solar system can have a significant impact on how it evolves.
In a cluster like Messier 67, where stars are much closer together than the average, such encounters would be much more common, which would explain the larger numbers of hot Jupiters found there.
Co-author and co-lead Luca Pasquini from ESO looks back on the remarkable recent history of studying planets in clusters: “No hot Jupiters at all had been detected in open clusters until a few years ago. In three years the paradigm has shifted from a total absence of such planets — to an excess!”
Notes:
[1] Some of the original sample of 88 were found to be binary stars, or unsuitable for other reasons for this study. This new paper concentrates on a sub-group of 66 stars.
[2] Although the cluster Messier 67 is still holding together, the cluster that may have surrounded the Sun in its early years would have dissipated long ago, leaving the Sun on its own.
[3] Spectra from the High Resolution Spectrograph on the Hobby-Eberly Telescope (http://www.as.utexas.edu/mcdonald/het/het.html) in Texas, USA, were also used, as well as from the SOPHIE spectrograph at the Observatoire de Haute Provence, in France.
[4] The first exoplanet found around a star similar to the Sun, 51 Pegasi b, was also a hot Jupiter. This was a surprise at the time, as many astronomers had assumed that other planetary systems would probably be like the Solar System and have their more massive planets further from the parent star.
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Need to Remember Something? Exercise 4 Hours Later
June 18th, 2016By Alton Parrish.
A new study suggests an intriguing strategy to boost memory for what you’ve just learned: hit the gym four hours later. The findings reported in the Cell Press journal Current Biology on June 16 show that physical exercise after learning improves memory and memory traces, but only if the exercise is done in a specific time window and not immediately after learning.
“It shows that we can improve memory consolidation by doing sports after learning,” says Guillén Fernández of the Donders Institute at the Radboud University Medical Center in the Netherlands.
In the new study, Fernández, along with Eelco van Dongen and their colleagues, tested the effects of a single session of physical exercise after learning on memory consolidation and long-term memory. Seventy-two study participants learned 90 picture-location associations over a period of approximately 40 minutes before being randomly assigned to one of three groups: one group performed exercise immediately, the second performed exercise four hours later, and the third did not perform any exercise.
The exercise consisted of 35 minutes of interval training on an exercise bike at an intensity of up to 80 percent of participants’ maximum heart rates. Forty-eight hours later, participants returned for a test to show how much they remembered while their brains were imaged via magnetic resonance imaging (MRI).
The researchers found that those who exercised four hours after their learning session retained the information better two days later than those who exercised either immediately or not at all. The brain images also showed that exercise after a time delay was associated with more precise representations in the hippocampus, an area important to learning and memory, when an individual answered a question correctly.
“Our results suggest that appropriately timed physical exercise can improve long-term memory and highlight the potential of exercise as an intervention in educational and clinical settings,” the researchers conclude.
It’s not yet clear exactly how or why delayed exercise has this effect on memory. However, earlier studies of laboratory animals suggest that naturally occurring chemical compounds in the body known as catecholamines, including dopamine and norepinephrine, can improve memory consolidation, the researchers say. One way to boost catecholamines is through physical exercise.
Fernández says they will now use a similar experimental setup to study the timing and molecular underpinnings of exercise and its influence on learning and memory in more detail.
The researchers were supported by a grant from the European Research Council.
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Galactic Hearts May Be Smaller Than First Thought; Suggests Co-Evolution of Galaxies and Central Black Hole
June 18th, 2016By Alton Parrish.
The supermassive black holes found at the centre of every galaxy, including our own Milky Way, may, on average, be smaller than we thought, according to work led by University of Southampton astronomer Dr Francesco Shankar.
If he and his colleagues are right, then the gravitational waves produced when they merge will be harder to detect than previously assumed. The international team of scientists published their results in Monthly Notices of the Royal Astronomical Society
An artist’s concept of a supermassive black hole at the center of a galaxy
Supermassive black holes have been found lurking in the cores of all galaxies observed with high enough sensitivity. Despite this, little is known about how they formed. What is known is that the mass of a supermassive black hole at the centre of a galaxy is related to the total mass and the typical speeds (the “velocity dispersion”) of the stars in its host.
The very existence of this relationship suggests a close co-evolution between black holes and their host galaxies, and understanding their origin is vital for a proper model of how galaxies and black holes form and evolve. This is because many galaxy evolution models invoke powerful winds and/or jets from the central supermassive black hole to control or even stop star formation in the host galaxy (so-called “quasar feedback”). Alternatively, multiple mergers of galaxies – and their central black holes – are also often suggested as the primary drivers behind the evolution of massive galaxies.
Despite major theoretical and observational efforts in the last decades, it remains unclear whether quasar feedback actually ever occurred in galaxies, and to what extent mergers have truly shaped galaxies and their black holes.
The new work shows that selection effects – where what is observed is not representative – have significantly biased the view of the local black hole population. This bias has led to significantly overestimated black hole masses. It suggests that modellers should look to velocity dispersion rather than stellar mass as the key to unlocking the decades-old puzzles of both quasar feedback and the history of galaxies.
With less mass than previously thought, supermassive black holes have on average weaker gravitational fields. Despite this, they were still able to power quasars, making them bright enough to be observed over distances of billions of light years.
Unfortunately, it also implies a substantial reduction in the expected gravitational wave signal detectable from pulsar timing array experiments. Ripples in spacetime that were first predicted by Albert Einstein in his general theory of relativity in 1915; gravitational waves were finally detected last year and announced by the LIGO team this February. The hope is that coming observatories can observe many more gravitational wave events, and that it will provide astronomers with a new technique for observing the universe.
Dr Shankar comments: “Gravitational wave astronomy is opening up an entirely new way of observing the universe. Our results though illustrate how challenging a complete census of the gravitational background could be, with the signals from the largest black holes being paradoxically among the most difficult to detect with present technology.”
Researchers expect pairs of supermassive black holes, found in merging galaxies, to be the strongest sources of gravitational waves in the universe. However, the more massive the pairs, the lower the frequencies of the emitted waves, which become inaccessible to ground based interferometers like LIGO. Gravitational waves from supermassive black holes can however be detected from space via dedicated gravitational telescopes (such as the present and future ESA missions LISA pathfinder and eLISA), or by a different method using ‘pulsar timing arrays’.
These devices monitor the collapsed, rapidly rotating remnants of massive stars, which have pulsating signals. Even this method though is still a few years from making a detection, according to a follow-up study by the same team expected to appear in another Monthly Notices paper later this year.
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New Electronic Nose To Sniff Out Diseases Cheaply, Analyzes Breath for Health Diagnosis
June 17th, 2016
By Alton Parrish.
Researchers at the Texas Analog Center of Excellence (TxACE) at UT Dallas are working to develop an affordable electronic nose that can be used in breath analysis for a wide range of health diagnosis.
While devices that can conduct breath analysis using compound semiconductors exist, they are bulky and too costly for commercial use, said Dr. Kenneth O, one of the principal investigators of the effort and director of TxACE. The researchers determined that using CMOS integrated circuits technology will make the electronic nose more affordable.
CMOS is the integrated circuits technology used to manufacture the bulk of electronics that have made smartphones, tablets and other devices possible.
The new research was presented Wednesday in a paper titled “200-280GHz CMOS Transmitter for Rotational Spectroscopy and Demonstration in Gas Spectroscopy and Breath Analysis” at the 2016 IEEE Symposia on VLSI Technology and Circuits in Honolulu, Hawaii.
“Smell is one of the senses of humans and animals, and there have been many efforts to build an electronic nose,” said Dr. Navneet Sharma, the lead author of paper, who recently defended his doctoral thesis at UT Dallas. “We have demonstrated that you can build an affordable electronic nose that can sense many different kinds of smells. When you’re smelling something, you are detecting chemical molecules in the air. Similarly, an electronic nose detects chemical compounds using rotational spectroscopy.”
The rotational spectrometer generates and transmits electromagnetic waves over a wide range of frequencies, and analyzes how the waves are attenuated to determine what chemicals are present as well as their concentrations in a sample. The system can detect low levels of chemicals present in human breath.
Breaths contain gases from the stomach and that come out of blood when it comes into contact with air in the lungs. The breath test is a blood test without taking blood samples. Breath contains information about practically every part of a human body.
The electronic nose can detect gas molecules with more specificity and sensitivity than Breathalyzers, which can confuse acetone for ethanol in the breath. The distinction is important, for example, for patients with Type 1 diabetes who have high concentrations of acetone in their breath.
“If you think about the industry around sensors that emulate our senses, it’s huge,” said Dr. O, also a professor in the Erik Jonsson School of Engineering and Computer Science and holder of the Texas Instruments Distinguished University Chair. “Imaging applications, hearing devices, touch sensors — what we are talking about here is developing a device that imitates another one of our sensing modalities and making it affordable and widely available. The possible use of the electronic nose is almost limitless. Think about how we use smell in our daily lives.”
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The researchers envision the CMOS-based device will first be used in industrial settings and then in doctors’ offices and hospitals. As the technology matures, they could become household devices. Dr. O said the need for blood work and gastrointestinal tests could be reduced, and diseases could be detected earlier, lowering the costs of health care.
The researchers are working toward construction of a prototype programmable electronic nose that can be made available for beta testing sometime in early 2018.
TxACE and this work are supported in large part by the Semiconductor Research Corporation (SRC) and Texas Instruments Inc. Additional support was provided by Samsung Global Research Outreach.
“SRC and its members, including Texas Instruments, Intel, IBM, Freescale, Mentor Graphics, ARM and GlobalFoundries, have been following this work for several years. We are excited by the possibilities of the new technology and are working to rapidly explore its uses and applications,” said Dr. David Yeh, SRC senior director. “It is a significant milestone, but there is still much more research needed for this to reach its potential.”
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First Detection of Merging Black Holes ‘Perfectly Consistent’ With Northwestern Model
June 17th, 2016
By Alton Parrish
Black hole mosh pit. In this simulation, 60 black holes and 500 stars interact with each other at the chaotic core of a globular cluster until two black holes combine to form a black hole binary.
These binary black holes are born in the chaotic “mosh pit” of a globular cluster, kicked out of the cluster and then eventually merge into one black hole. This theory, known as dynamical formation, is one of two recognized main channels for forming the binary black holes detected by the Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory).
LIGO’s first detection of merging black holes is perfectly consistent with the dynamical formation model from the Northwestern research team and is what you would expect from a globular cluster, the researchers say.
Colliding black holes do not emit light; however, they do release a phenomenal amount of energy as gravitational waves. The first detection of these waves occurred Sept. 14, and the second — announced to the world this morning — occurred three months later. These events have launched a new era in astronomy: using gravitational waves to learn about the universe.
“Thanks to LIGO, we’re not just theorists speculating anymore — now we have data,” said Frederic A. Rasio, a theoretical astrophysicist at Northwestern and senior author of the study. “A relatively simple and well understood process seems to work. Simple freshman physics — Newton’s first law of motion — explains the gravitational dynamics of the first black holes detected by LIGO.”
Rasio will detail how the first LIGO detection fits into his team’s theory at a media briefing at 2:15 p.m. Pacific Daylight Time today (June 15) at the summer meeting of the American Astronomical Society (AAS) in San Diego. He also will be available to discuss the research at a related poster session later in the day, from 5:30 to 6:30 p.m. PDT at the AAS meeting.
At a separate media briefing the LIGO Scientific Collaboration announced its second detection — on Boxing Day in the U.K. and Christmas Day 2015 in the U.S. — of gravitational waves and merging black holes. This growing population of black holes will help astrophysicists learn more about the universe.
“We were ecstatic by the news announced earlier this year by LIGO about its first detection of colliding black holes,” said Carl L. Rodriguez, lead author of the study and a Ph.D. student in Rasio’s research group. “The findings are pretty much where we thought they would be. We look forward to working with the data from new detections.”
The coalescence of two black holes is a very violent and exotic event. Rasio and his team used models of globular clusters — spherical collections of up to a million densely packed stars, common in the universe — to demonstrate that a typical cluster can very naturally create a binary black hole that will merge and form one larger black hole.
Their powerful computer model can predict how many merging binary black holes LIGO might detect: potentially 100 forged in the cores of these dense star clusters per year. The model also shows where in the universe the binary black holes are, how long ago they merged and the masses of each black hole.
“Simple physical processes make the heavy black holes go to the center of the cluster,” Rasio said. “These pairs eventually merge and are detected by LIGO.” He is the Joseph Cummings Professor in the department of physics and astronomy in Northwestern’s Weinberg College of Arts and Sciences.
“By the end of the decade, we expect LIGO to detect hundreds to thousands of binary black holes,” Rodriguez said.
Rasio and Rodriguez are members of Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).
In their study, Rasio, Rodriguez and colleagues describe in detail the dynamical interaction processes that could form a merging binary black hole system. They also show that theoretical predictions for this dynamical formation channel are, in general, far more robust than models for the other main channel for forming binary black holes, based on the evolution of massive stars in isolated binaries (not in star clusters).”
Rodriguez and colleagues used 52 detailed computer models to demonstrate how a globular cluster acts as a dominant source of binary black holes, producing hundreds of black hole mergers over a cluster’s 12-billion-year lifetime.
By comparing the models to recent observations of clusters in the Milky Way galaxy and beyond, the results show that Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) could eventually see more than 100 binary black hole mergers per year.
For the study, the research team used a parallel computing code for modeling star clusters developed through a CIERA-supported interdisciplinary collaboration between Northwestern’s physics and astronomy department and electrical engineering and computer science department. The paper includes 52 computer models, and their most massive model required 30,000 hours of computing power.
Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory) is a large-scale physics experiment designed to directly detect gravitational waves of cosmic origin. Laser interferometers detect gravitational waves from the minute oscillations of suspended mirrors set into motion as the waves pass through the Earth.
The National Science Foundation (grant AST-1312945) and NASA (grant NNX14AP92G) supported the research.
The paper, titled “Dynamical Formation of the GW150914 Binary Black Hole,” was published June 10 by The Astrophysical Journal Letters. In addition to Rasio and Rodriguez, other authors are Sourav Chatterjee and Vicky Kalogera of Northwestern and Carl-Johan Haster of the University of Birmingham.
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New Way to Turn Electricity into Light, Using Graphene, Could Make Computer Chips a Million Times Faster
June 16th, 2016By Alton Parrish.
When an airplane begins to move faster than the speed of sound, it creates a shockwave that produces a well-known “boom” of sound. Now, researchers at MIT and elsewhere have discovered a similar process in a sheet of graphene, in which a flow of electric current can, under certain circumstances, exceed the speed of slowed-down light and produce a kind of optical “boom”: an intense, focused beam of light.
This entirely new way of converting electricity into visible radiation is highly controllable, fast, and efficient, the researchers say, and could lead to a wide variety of new applications. The work is reported today in the journal Nature Communications, in a paper by two MIT professors — Marin Soljačić, professor of physics; and John Joannopoulos, the Francis Wright Davis Professor of physics — as well as postdoc Ido Kaminer, and six others in Israel, Croatia, and Singapore.
This illustration depicts the process of lights emission from a sheet of graphene, which is represented as the blue lattice on the top surface of a carrier material. The light-colored arrow moving upwards at the center depicts a fast-moving electron. Because the electron is moving faster than light itself, it generates a shock wave, which spews out plasmons, shown as red squiggly lines, in two directions.
The new finding started from an intriguing observation. The researchers found that when light strikes a sheet of graphene, which is a two-dimensional form of the element carbon, it can slow down by a factor of a few hundred. That dramatic slowdown, they noticed, presented an interesting coincidence. The reduced speed of photons (particles of light) moving through the sheet of graphene happened to be very close to the speed of electrons as they moved through the same material.
“Graphene has this ability to trap light, in modes we call surface plasmons,” explains Kaminer, who is the paper’s lead author. Plasmons are a kind of virtual particle that represents the oscillations of electrons on the surface. The speed of these plasmons through the graphene is “a few hundred times slower than light in free space,” he says.
This effect dovetailed with another of graphene’s exceptional characteristics: Electrons pass through it at very high speeds, up to a million meters per second, or about 1/300 the speed of light in a vacuum. That meant that the two speeds were similar enough that significant interactions might occur between the two kinds of particles, if the material could be tuned to get the velocities to match.
That combination of properties — slowing down light and allowing electrons to move very fast — is “one of the unusual properties of graphene,” says Soljačić. That suggested the possibility of using graphene to produce the opposite effect: to produce light instead of trapping it. “Our theoretical work shows that this can lead to a new way of generating light,” he says.
Specifically, he explains, “This conversion is made possible because the electronic speed can approach the light speed in graphene, breaking the ‘light barrier.’” Just as breaking the sound barrier generates a shockwave of sound, he says, “In the case of graphene, this leads to the emission of a shockwave of light, trapped in two dimensions.”
The phenomenon the team has harnessed is called the Čerenkov effect, first described 80 years ago by Soviet physicist Pavel Čerenkov. Usually associated with astronomical phenomenon and harnessed as a way of detecting ultrafast cosmic particles as they hurtle through the universe, and also to detect particles resulting from high-energy collisions in particle accelerators, the effect had not been considered relevant to Earthbound technology because it only works when objects are moving close to the speed of light. But the slowing of light inside a graphene sheet provided the opportunity to harness this effect in a practical form, the researchers say.
There are many different ways of converting electricity into light — from the heated tungsten filaments that Thomas Edison perfected more than a century ago, to fluorescent tubes, to the light-emitting diodes (LEDs) that power many display screens and are gaining favor for household lighting. But this new plasmon-based approach might eventually be part of more efficient, more compact, faster, and more tunable alternatives for certain applications, the researchers say.
Perhaps most significantly, this is a way of efficiently and controllably generating plasmons on a scale that is compatible with current microchip technology. Such graphene-based systems could potentially be key on-chip components for the creation of new, light-based circuits, which are considered a major new direction in the evolution of computing technology toward ever-smaller and more efficient devices.
“If you want to do all sorts of signal processing problems on a chip, you want to have a very fast signal, and also to be able to work on very small scales,” Kaminer says. Computer chips have already reduced the scale of electronics to the points that the technology is bumping into some fundamental physical limits, so “you need to go into a different regime of electromagnetism,” he says. Using light instead of flowing electrons as the basis for moving and storing data has the potential to push the operating speeds “six orders of magnitude higher than what is used in electronics,” Kaminer says — in other words, in principle up to a million times faster.
One problem faced by researchers trying to develop optically based chips, he says, is that while electricity can be easily confined within wires, light tends to spread out. Inside a layer of graphene, however, under the right conditions, the beams are very well confined.
“There’s a lot of excitement about graphene,” says Soljačić, “because it could be easily integrated with other electronics” enabling its potential use as an on-chip light source. So far, the work is theoretical, he says, so the next step will be to create working versions of the system to prove the concept. “I have confidence that it should be doable within one to two years,” he says. The next step would then be to optimize the system for the greatest efficiency.
This finding “is a truly innovative concept that has the potential to be the key toward solving the long-standing problem of achieving highly efficient and ultrafast electrical-to-optical signal conversion at the nanoscale,” says Jorge Bravo-Abad, an assistant professor at the Autonomous University of Madrid, in Spain, who was not involved in this work.
In addition, Bravo-Abad says, “the novel instance of Čerenkov emission discovered by the authors of this work opens up whole new prospects for the study of the Čerenkov effect in nanoscale systems, without the need of sophisticated experimental set-ups. I look forward to seeing the significant impact and implications that these findings will surely have at the interface between physics and nanotechnology.”
The research was supported by the U.S. Army Research Laboratory and the U.S. Army Research Office, through the Institute for Soldier Nanotechnologies at MIT. The team included researchers Yichen Shen, Ognjen Ilic, and Josue Lopez at MIT; Yaniv Katan at Technion, in Haifa, Israel; Hrvoje Buljan at the University of Zagreb in Croatia; and Liang Jie Wong at the Singapore Institute of Manufacturing Technology.
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LIGO Detects Gravitational Waves for Second Time from Merging Black Holes
June 16th, 2016By Alton Parrish.
For the second time, scientists have directly detected gravitational waves — ripples through the fabric of space-time, created by extreme, cataclysmic events in the distant universe. The team has determined that the incredibly faint ripple that eventually reached Earth was produced by two black holes colliding at half the speed of light, 1.4 billion light years away.
The scientists detected the gravitational waves using the twin Laser Interferometer Gravitational-wave Observatory (LIGO) interferometers, located in Livingston, Louisiana, and Hanford, Washington. On Dec. 26, 2015, at 3:38 UTC, both detectors, situated more than 3,000 kilometers apart, picked up a very faint signal amid the surrounding noise.
The two LIGO gravitational wave detectors in Hanford Washington and Livingston Louisiana have caught a second robust signal from two black holes in their final orbits and then their coalescence into a single black hole. This event, dubbed GW151226, was seen on December 26th at 03:38:53 (in Universal Coordinated Time, also known as Greenwich Mean Time), near the end of LIGO’s first observing period (“O1”), and was immediately nicknamed “the Boxing Day event”.
Like LIGO’s first detection, this event was identified within minutes of the gravitational wave’s passing. Subsequent careful studies of the instruments and environments around the observatories showed that the signal seen in the two detectors was truly from distant black holes – some 1.4 billion light years away, coincidentally at about the same distance as the first signal ever detected. The Boxing Day event differed from the LIGO’s first gravitational wave observation in some important ways, however.
This artist’s illustration depicts the merging black hole binary systems for GW150914 (left image) and GW151226 (right image). The black hole pairs are shown together in this illustration, but were actually detected at different times, and on different parts of the sky. The images have been scaled to show the difference in black hole masses. In the GW150914 event, the black holes were 29 and 36 times that of our Sun, while in GW151226, the two black holes weighed in at 14 and 8 solar masses.
The gravitational wave arrived at the two detectors at almost the same time, indicating that the source was located somewhere in a ring of sky about midway between the two detectors. Knowing our detector sensitivity pattern, we can add that it was a bit more likely overhead or underfoot instead of to the West or the East. With only two detectors, however, we can’t narrow it down much more than that. This differs from LIGO’s first detected signal (GW150914, from 14 September 2015), which came from the ‘southeast’, hitting Louisiana’s detector before Washington’s.
With these two confirmed detections, along with a third likely detection made in October 2015 (believed also to be caused by a pair of merging black holes–see our paper draft on Black Hole Binaries in O1 for more information) we can now start to estimate the rate of black hole coalescences in the Universe based not on theory, but on real observations. Of course with just a few signals, our estimate has big uncertainties, but our best right now is somewhere between 9 and 240 binary black hole coalescences per cubic Gigaparsec per year, or about one every 10 years in a volume a trillion times the volume of the Milky Way galaxy! Happily, in its first few months of operation, LIGO’s advanced detectors were sensitive enough to probe deeply enough into space to see about one event every two months.
This illustration shows the merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. The black holes—which represent those detected by LIGO on Dec. 26, 2015—were 14 and 8 times the mass of the sun, until they merged, forming a single black hole 21 times the mass of the sun. In reality, the area near the black holes would appear highly warped, and the gravitational waves would be difficult to see directly.
Our next observing interval – Observing Run #2, or “O2” – will start in the Fall of 2016. With improved sensitivity, we expect to see more black hole coalescences, and possibly detect gravitational waves from other sources, like binary neutron-star mergers. We are also looking forward to the Virgo detector joining us later in the O2 run. Virgo will be enormously helpful in locating sources on the sky, collapsing that ring down to a patch, but also helping us understand the sources of gravitational waves.
LIGO releases its data to the public. This open-data policy allows others to analyze our data, thus ensuring that the LIGO and Virgo collaborations did not miss anything in their analyses, and in the hopes that others will find even more interesting events. Our data are shared at the LIGO Open Science Center. GW151226 has its own page there.
We encourage you to wander around the LIGO Laboratory web page where you will find graphics to help you understand the Boxing Day observation, links to the press release, and pointers to scientific papers if you would like to dig in even deeper. There you will also find links to the LIGO Scientific Collaboration website, and to our sister collaboration, Virgo, both of which are central to these scientific results.
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Salt Baths Boost Next Generation Batteries for Electric Cars
June 15th, 2016By Alton Parrish.
The next generation of rechargeable lithium batteries set to disrupt the electric vehicle industry may soon be here, thanks to the humble salt bath.
CSIRO scientists, in collaboration with RMIT University and QUT, have demonstrated that pre-treating a battery’s lithium metal electrodes with an electrolyte salt solution extends the battery life and increases performance and safety.
The research was published in Nature Communications.
The simple method is set to accelerate the development of next-gen energy storage solutions and overcome the issue of ‘battery range anxiety’ that is currently a barrier in the electric car industry.
“Our research has shown by pre-treating lithium metal electrodes, we can create batteries with charge efficiency that greatly exceeds standard lithium batteries,” Dr Best said.
The pre-treatment process involves the immersion of lithium metal electrodes in an electrolyte bath containing a mixture of ionic liquids and lithium salts, prior to a battery being assembled.
Ionic liquids or room temperature molten salts, are a unique class of material that are clear, colourless, odourless solutions and are non-flammable.
The Room Temperature Ionic Liquid (RTIL) electrolytes developed by CSIRO, RMIT and Queensland University of Technology may hold the key to solving electric car “battery range anxiety”.
When used in batteries these materials can prevent the risk of fire and explosion, a known rechargeable battery issue.
The salt bath pre-treatment adds a protective film onto the surface of the electrode that helps stabilise the battery when in operation.
“The pre-treatment reduces the breakdown of electrolytes during operation, which is what determines the battery’s increased performance and lifetime,” Dr Best said.
Batteries that have undergone the process can also spend up to one year on the shelf without loss of performance.
QUT researcher Assoc. Prof. Anthony O’Mullane said the method can be easily adopted by manufacturers.
“The pre-treatment process is readily transferrable to existing manufacturing processes,” Assoc. Prof. O’Mullane said.
The electrolyte salt solutions, to which CSIRO holds patents, come in a range of chemical compositions.
The research formed part of Dr Andrew Basile’s doctoral thesis with RMIT University, working closely with CSIRO scientist Dr Anand Bhatt to investigate battery processes occurring at lithium metal.
The team of scientists is currently developing batteries based on this technology, and are looking for partners to help bring these materials and devices to market.
You can read complete the Nature Communication paper Stabilizing lithium metal using ionic liquids for long-lived batteries online.
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