Tag Archives: nature

The elliptical galaxy NGC 1600, 200 million light-years away — shown in the centre of the image and highlighted in the box —, hosts in its centre one of the biggest supermassive black holes known . Until the discovery of this example, astronomers assumed that such huge black holes could only be found in the centres of massive galaxies at the centre of galaxy clusters. NGC 1600, however, is a rather isolated galaxy.

The image is a composition of a ground based view and observations made with the NASA/ESA Hubble Space Telescope.

Credit:
NASA, ESA, Digital Sky Survey 2

NGC 1600′s super massive blackhole discovery puzzles astronomers

Astronomers have uncovered one of the biggest supermassive black holes, with the mass of 17 billion Suns, in an unlikely place: the centre of a galaxy that lies in a quiet backwater of the Universe. The observations, made with the NASA/ESA Hubble Space Telescope and the Gemini Telescope in Hawaii, indicate that these monster objects may be more common than once thought. The results of this study are released in the journal Nature.

The elliptical galaxy NGC 1600, 200 million light-years away — shown in the centre of the image and highlighted in the box —, hosts in its centre one of the biggest supermassive black holes known . Until the discovery of this example, astronomers assumed that such huge black holes could only be found in the centres of massive galaxies at the centre of galaxy clusters. NGC 1600, however, is a rather isolated galaxy. The image is a composition of a ground based view and observations made with the NASA/ESA Hubble Space Telescope. Credit: NASA, ESA, Digital Sky Survey 2
The elliptical galaxy NGC 1600, 200 million light-years away — shown in the centre of the image and highlighted in the box —, hosts in its centre one of the biggest supermassive black holes known . Until the discovery of this example, astronomers assumed that such huge black holes could only be found in the centres of massive galaxies at the centre of galaxy clusters. NGC 1600, however, is a rather isolated galaxy.
The image is a composition of a ground based view and observations made with the NASA/ESA Hubble Space Telescope.
Credit:
NASA, ESA, Digital Sky Survey 2

Until now, the biggest supermassive black holes — those having more than 10 billion times the mass of our Sun — have only been found at the cores of very large galaxies in the centres of massive galaxy clusters. Now, an international team of astronomers using the NASA/ESA Hubble Space Telescope has discovered a supersized black hole with a mass of 17 billion Suns in the centre of the rather isolated galaxy NGC 1600.

NGC 1600 is an elliptical galaxy which is located not in a cluster of galaxies, but in a small group of about twenty. The group is located 200 million light-years away in the constellation Eridanus. While finding a gigantic supermassive black hole in a massive galaxy within a cluster of galaxies is to be expected, finding one in an average-sized galaxy group like the one surrounding NGC 1600 is much more surprising.

“Even though we already had hints that the galaxy might host an extreme object in the centre, we were surprised that the black hole in NGC 1600 is ten times more massive than predicted by the mass of the galaxy,” explains lead author of the study Jens Thomas from the Max Planck-Institute for Extraterrestrial Physics, Germany.

Based on previous Hubble surveys of supermassive black holes, astronomers had discovered a correlation between a black hole’s mass and the mass of its host galaxy’s central bulge of stars: the larger the galaxy bulge, the more massive the black hole is expected to be. “It appears from our finding that this relation does not work so well with extremely massive black holes,” says Thomas. “These monster black holes account for a much larger fraction of the host galaxy’s mass than the previous correlations would suggest.”

Finding this extremely massive black hole in NGC 1600 leads astronomers to ask whether these objects are more common than previously thought. “There are quite a few galaxies the size of NGC 1600 that reside in average-size galaxy groups,” explains co-author Chung-Pei Ma, an astronomer from the University of California, Berkeley, USA, and head of the MASSIVE Survey [1]. “We estimate that these smaller groups are about fifty times more abundant than large, dense galaxy clusters. So the question now is: is this the tip of an iceberg? Maybe there are a lot more monster black holes out there.”

It is assumed that this black hole grew by merging with another supermassive black hole from another galaxy. It may then have continued to grow by gobbling up gas funneled to the core of the galaxy by further galaxy collisions. Thus may also explain why NGC 1600 resides in a sparsely populated region of the Universe and why it is at least three times brighter than its neighbours.

As the supermassive black hole is currently dormant, astronomers were only able to find it and estimate its mass by measuring the velocities of stars close to it, using the Gemini North 8-metre telescope on Mauna Kea, Hawaii. Using these data the team discovered that stars lying about 3000 light-years from the core are moving as if there had been many more stars in the core in the distant past. This indicates that most of the stars in this region have been kicked out from the centre of the galaxy.

Archival Hubble images, taken with the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), support the idea that the two merging supermassive black holes in the distant past gave stars the boot. The NICMOS images revealed that the galaxy’s core is unusually faint, indicating a lack of stars close to the galactic centre. “We estimate that the mass of stars tossed out of the central region of NGC 1600 is equal to 40 billion Suns,” concludes Thomas. “This is comparable to ejecting the entire disc of our Milky Way galaxy.”

Notes
[1] The MASSIVE Survey, which began in 2014, measures the mass of stars, dark matter, and the central black hole of the 100 most massive, nearby galaxies, those larger than 300 billion solar masses and within 350 million light-years of Earth. Among its goals are to find the descendants of luminous quasars that may be sleeping unsuspected in large nearby galaxies and to understand how galaxies form and grow supermassive black holes.

More information
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The study “A 17-billion-solar-mass black hole in a group galaxy with a diffuse core” appeared in the journal Nature.

The international team of astronomers in this study consists of J. Thomas (Max Planck Institute for Extraterrestrial Physics, Germany), C.-P. Ma (University of California, Berkeley, USA), N. McConnell (Dominion Astrophysical Observatory, Canada), J. Greene (Princeton University, USA), J. Blakeslee (Dominion Astrophysical Observatory, Canada), and R. Janish (University of California, Berkeley, USA)

Source: Space Telescope

Persian Gulf could experience deadly heat: MIT Study

Detailed climate simulation shows a threshold of survivability could be crossed without mitigation measures.

By David Chandler


 

CAMBRIDGE, Mass.–Within this century, parts of the Persian Gulf region could be hit with unprecedented events of deadly heat as a result of climate change, according to a study of high-resolution climate models.

The research reveals details of a business-as-usual scenario for greenhouse gas emissions, but also shows that curbing emissions could forestall these deadly temperature extremes.

The study, published today in the journal Nature Climate Change, was carried out by Elfatih Eltahir, a professor of civil and environmental engineering at MIT, and Jeremy Pal PhD ’01 at Loyola Marymount University. They conclude that conditions in the Persian Gulf region, including its shallow water and intense sun, make it “a specific regional hotspot where climate change, in absence of significant mitigation, is likely to severely impact human habitability in the future.”

Running high-resolution versions of standard climate models, Eltahir and Pal found that many major cities in the region could exceed a tipping point for human survival, even in shaded and well-ventilated spaces. Eltahir says this threshold “has, as far as we know … never been reported for any location on Earth.”

That tipping point involves a measurement called the “wet-bulb temperature” that combines temperature and humidity, reflecting conditions the human body could maintain without artificial cooling. That threshold for survival for more than six unprotected hours is 35 degrees Celsius, or about 95 degrees Fahrenheit, according to recently published research. (The equivalent number in the National Weather Service’s more commonly used “heat index” would be about 165 F.)

This limit was almost reached this summer, at the end of an extreme, weeklong heat wave in the region: On July 31, the wet-bulb temperature in Bandahr Mashrahr, Iran, hit 34.6 C — just a fraction below the threshold, for an hour or less.

But the severe danger to human health and life occurs when such temperatures are sustained for several hours, Eltahir says — which the models show would occur several times in a 30-year period toward the end of the century under the business-as-usual scenario used as a benchmark by the Intergovernmental Panel on Climate Change.

The Persian Gulf region is especially vulnerable, the researchers say, because of a combination of low elevations, clear sky, water body that increases heat absorption, and the shallowness of the Persian Gulf itself, which produces high water temperatures that lead to strong evaporation and very high humidity.

The models show that by the latter part of this century, major cities such as Doha, Qatar, Abu Dhabi, and Dubai in the United Arab Emirates, and Bandar Abbas, Iran, could exceed the 35 C threshold several times over a 30-year period. What’s more, Eltahir says, hot summer conditions that now occur once every 20 days or so “will characterize the usual summer day in the future.”

While the other side of the Arabian Peninsula, adjacent to the Red Sea, would see less extreme heat, the projections show that dangerous extremes are also likely there, reaching wet-bulb temperatures of 32 to 34 C. This could be a particular concern, the authors note, because the annual Hajj, or annual Islamic pilgrimage to Mecca — when as many as 2 million pilgrims take part in rituals that include standing outdoors for a full day of prayer — sometimes occurs during these hot months.

While many in the Persian Gulf’s wealthier states might be able to adapt to new climate extremes, poorer areas, such as Yemen, might be less able to cope with such extremes, the authors say.

The research was supported by the Kuwait Foundation for the Advancement of Science.

Source: MIT News Office

Researchers use engineered viruses to provide quantum-based enhancement of energy transport:MIT Research

Quantum physics meets genetic engineering

Researchers use engineered viruses to provide quantum-based enhancement of energy transport.

By David Chandler


 

CAMBRIDGE, Mass.–Nature has had billions of years to perfect photosynthesis, which directly or indirectly supports virtually all life on Earth. In that time, the process has achieved almost 100 percent efficiency in transporting the energy of sunlight from receptors to reaction centers where it can be harnessed — a performance vastly better than even the best solar cells.

One way plants achieve this efficiency is by making use of the exotic effects of quantum mechanics — effects sometimes known as “quantum weirdness.” These effects, which include the ability of a particle to exist in more than one place at a time, have now been used by engineers at MIT to achieve a significant efficiency boost in a light-harvesting system.

Surprisingly, the MIT researchers achieved this new approach to solar energy not with high-tech materials or microchips — but by using genetically engineered viruses.

This achievement in coupling quantum research and genetic manipulation, described this week in the journal Nature Materials, was the work of MIT professors Angela Belcher, an expert on engineering viruses to carry out energy-related tasks, and Seth Lloyd, an expert on quantum theory and its potential applications; research associate Heechul Park; and 14 collaborators at MIT and in Italy.

Lloyd, a professor of mechanical engineering, explains that in photosynthesis, a photon hits a receptor called a chromophore, which in turn produces an exciton — a quantum particle of energy. This exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life.

But the hopping pathway is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle.

This efficient movement of excitons has one key requirement: The chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the “Quantum Goldilocks Effect.”

That’s where the virus comes in. By engineering a virus that Belcher has worked with for years, the team was able to get it to bond with multiple synthetic chromophores — or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.

In the end, they were able to more than double excitons’ speed, increasing the distance they traveled before dissipating — a significant improvement in the efficiency of the process.

The project started from a chance meeting at a conference in Italy. Lloyd and Belcher, a professor of biological engineering, were reporting on different projects they had worked on, and began discussing the possibility of a project encompassing their very different expertise. Lloyd, whose work is mostly theoretical, pointed out that the viruses Belcher works with have the right length scales to potentially support quantum effects.

In 2008, Lloyd had published a paper demonstrating that photosynthetic organisms transmit light energy efficiently because of these quantum effects. When he saw Belcher’s report on her work with engineered viruses, he wondered if that might provide a way to artificially induce a similar effect, in an effort to approach nature’s efficiency.

“I had been talking about potential systems you could use to demonstrate this effect, and Angela said, ‘We’re already making those,’” Lloyd recalls. Eventually, after much analysis, “We came up with design principles to redesign how the virus is capturing light, and get it to this quantum regime.”

Within two weeks, Belcher’s team had created their first test version of the engineered virus. Many months of work then went into perfecting the receptors and the spacings.

Once the team engineered the viruses, they were able to use laser spectroscopy and dynamical modeling to watch the light-harvesting process in action, and to demonstrate that the new viruses were indeed making use of quantum coherence to enhance the transport of excitons.

“It was really fun,” Belcher says. “A group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That’s why I’m so excited by this.”

While this initial result is essentially a proof of concept rather than a practical system, it points the way toward an approach that could lead to inexpensive and efficient solar cells or light-driven catalysis, the team says. So far, the engineered viruses collect and transport energy from incoming light, but do not yet harness it to produce power (as in solar cells) or molecules (as in photosynthesis). But this could be done by adding a reaction center, where such processing takes place, to the end of the virus where the excitons end up.

The research was supported by the Italian energy company Eni through the MIT Energy Initiative. In addition to MIT postdocs Nimrod Heldman and Patrick Rebentrost, the team included researchers at the University of Florence, the University of Perugia, and Eni.

Source:MIT News Office

Physicists solve quantum tunneling mystery

An international team of scientists studying ultrafast physics have solved a mystery of quantum mechanics, and found that quantum tunneling is an instantaneous process.

The new theory could lead to faster and smaller electronic components, for which quantum tunneling is a significant factor. It will also lead to a better understanding of diverse areas such as electron microscopy, nuclear fusion and DNA mutations.

“Timescales this short have never been explored before. It’s an entirely new world,” said one of the international team, Professor Anatoli Kheifets, from The Australian National University (ANU).

“We have modelled the most delicate processes of nature very accurately.”

At very small scales quantum physics shows that particles such as electrons have wave-like properties – their exact position is not well defined. This means they can occasionally sneak through apparently impenetrable barriers, a phenomenon called quantum tunneling.

Quantum tunneling plays a role in a number of phenomena, such as nuclear fusion in the sun, scanning tunneling microscopy, and flash memory for computers. However, the leakage of particles also limits the miniaturisation of electronic components.

Professor Kheifets and Dr. Igor Ivanov, from the ANU Research School of Physics and Engineering, are members of a team which studied ultrafast experiments at the attosecond scale (10-18 seconds), a field that has developed in the last 15 years.

Until their work, a number of attosecond phenomena could not be adequately explained, such as the time delay when a photon ionised an atom.

“At that timescale the time an electron takes to quantum tunnel out of an atom was thought to be significant. But the mathematics says the time during tunneling is imaginary – a complex number – which we realised meant it must be an instantaneous process,” said Professor Kheifets.

“A very interesting paradox arises, because electron velocity during tunneling may become greater than the speed of light. However, this does not contradict the special theory of relativity, as the tunneling velocity is also imaginary” said Dr Ivanov, who recently took up a position at the Center for Relativistic Laser Science in Korea.

The team’s calculations, which were made using the Raijin supercomputer, revealed that the delay in photoionisation originates not from quantum tunneling but from the electric field of the nucleus attracting the escaping electron.

The results give an accurate calibration for future attosecond-scale research, said Professor Kheifets.

“It’s a good reference point for future experiments, such as studying proteins unfolding, or speeding up electrons in microchips,” he said.

The research is published in Nature Physics.

Source: ANU

Experiment confirms quantum theory weirdness

The bizarre nature of reality as laid out by quantum theory has survived another test, with scientists performing a famous experiment and proving that reality does not exist until it is measured.

Physicists at The Australian National University (ANU) have conducted John Wheeler’s delayed-choice thought experiment, which involves a moving object that is given the choice to act like a particle or a wave. Wheeler’s experiment then asks – at which point does the object decide?

Common sense says the object is either wave-like or particle-like, independent of how we measure it. But quantum physics predicts that whether you observe wave like behavior (interference) or particle behavior (no interference) depends only on how it is actually measured at the end of its journey. This is exactly what the ANU team found.

“It proves that measurement is everything. At the quantum level, reality does not exist if you are not looking at it,” said Associate Professor Andrew Truscott from the ANU Research School of Physics and Engineering.

Despite the apparent weirdness, the results confirm the validity of quantum theory, which governs the world of the very small, and has enabled the development of many technologies such as LEDs, lasers and computer chips.

The ANU team not only succeeded in building the experiment, which seemed nearly impossible when it was proposed in 1978, but reversed Wheeler’s original concept of light beams being bounced by mirrors, and instead used atoms scattered by laser light.

“Quantum physics’ predictions about interference seem odd enough when applied to light, which seems more like a wave, but to have done the experiment with atoms, which are complicated things that have mass and interact with electric fields and so on, adds to the weirdness,” said Roman Khakimov, PhD student at the Research School of Physics and Engineering.

Professor Truscott’s team first trapped a collection of helium atoms in a suspended state known as a Bose-Einstein condensate, and then ejected them until there was only a single atom left.

The single atom was then dropped through a pair of counter-propagating laser beams, which formed a grating pattern that acted as crossroads in the same way a solid grating would scatter light.

A second light grating to recombine the paths was randomly added, which led to constructive or destructive interference as if the atom had travelled both paths. When the second light grating was not added, no interference was observed as if the atom chose only one path.

However, the random number determining whether the grating was added was only generated after the atom had passed through the crossroads.

If one chooses to believe that the atom really did take a particular path or paths then one has to accept that a future measurement is affecting the atom’s past, said Truscott.

“The atoms did not travel from A to B. It was only when they were measured at the end of the journey that their wave-like or particle-like behavior was brought into existence,” he said.

The research is published in Nature Physics.

Source: ANU

Researchers unravel secrets of hidden waves

Region of world’s strongest “internal waves” is analyzed in detail; work could help refine climate models.

By David Chandler


CAMBRIDGE, Mass–Detailed new field studies, laboratory experiments, and simulations of the largest known “internal waves” in the Earth’s oceans — phenomena that play a key role in mixing ocean waters, greatly affecting ocean temperatures — provide a comprehensive new view of how these colossal, invisible waves are born, spread, and die off.

The work, published today in the journal Nature, could add significantly to the improvement of global climate models, the researchers say. The paper is co-authored by 42 researchers from 25 institutions in five countries.

“What this report presents is a complete picture, a cradle-to-grave picture of these waves,” says Thomas Peacock, an associate professor of mechanical engineering at MIT, and one of the paper’s two lead authors.

Internal waves — giant waves, below the surface, that roil stratified layers of heavier, saltier water and lighter, less-salty water — are ubiquitous throughout the world’s oceans. But by far the largest and most powerful known internal waves are those that form in one area of the South China Sea, originating from the Luzon Strait between the Philippines and Taiwan.

These subsurface waves can tower more than 500 meters high, and generate powerful turbulence. Because of their size and behavior, the rise and spread of these waves are important for marine processes, including the supply of nutrients for marine organisms; the distribution of sediments and pollutants; and the propagation of sound waves. They are also a significant factor in the mixing of ocean waters, combining warmer surface waters with cold, deep waters — a process that is essential to understanding the dynamics of global climate.

This international research effort, called IWISE (Internal Waves In Straits Experiment), was a rare undertaking in this field, Peacock says; the last such field study on internal waves on this scale, the Hawaii Ocean Mixing Experiment, concluded in 2002. The new study looked at internal waves that were much stronger, and went significantly further in determining not just how the waves originated, but how their energy dissipated.

One unexpected finding, Peacock says, was the degree of turbulence produced as the waves originate, as tides and currents pass over ridges on the seafloor. “These were unexpected field discoveries,” he says, revealing “some of the most intense mixing ever observed in the deep ocean. It’s like a giant washing machine — the mixing is much more dramatic than we ever expected.”

The new observations, Peacock says, resolve a longstanding technical question about how internal waves propagate — whether the towering waves start out full strength at their point of origin, or whether they continue to build as they spread from that site. Many attempts to answer this question have produced contradictory results over the years.

This new research, which involved placing several long mooring lines from the seafloor to buoys at the surface, with instruments at intervals all along the lines, has decisively resolved that question, Peacock says: The waves grow larger as they propagate. Prior measurements, the new work found, had been drawn from too narrow a slice of the region, resulting in conflicting results — rather like the fable of blind men describing an elephant. The new, more comprehensive data has now resolved the mystery.

The new data also contradict a long-held assumption — a “commonly held belief that was almost stated as fact,” Peacock says — that solitary internal waves are completely absent from the South China Sea during the winter months. But with equipment in place to reliably measure water movement throughout the year, the team found these waves were “carrying on quite happily throughout the entire winter,” Peacock says: Previously, their presence had been masked by the winter’s stormier weather, and by the influence of a strong boundary current that runs along the coast of Taiwan — the regional equivalent of the Gulf Stream.

The improved understanding of internal waves, Peacock says, could be useful for researchers in a number of areas. The waves are key to some ecosystems, for example — some marine creatures essentially “surf” them to move in toward shore, for feeding or breeding; in the South China Sea, this process helps sustain an extensive coral reef system. The waves also help carry heat from the ocean’s surface to its depths, an important parameter in modeling climate.

The research, which was primarily a collaboration between U.S. and Taiwanese scientists, was funded by the U.S. Office of Naval Research and the Taiwan National Science Council.

Source: MIT News Office

This chart of the position of a nova (marked in red) that appeared in the year 1670 was recorded by the famous astronomer Hevelius and was published by the Royal Society in England in their journal Philosophical Transactions.

New observations made with APEX and other telescopes have now revealed that the star that European astronomers saw was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later.

Credit:
Royal Society

Colliding Stars Explain Enigmatic Seventeenth Century Explosion

APEX observations help unravel mystery of Nova Vulpeculae 1670


New observations made with APEX and other telescopes reveal that the star that European astronomers saw appear in the sky in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later. The results appear online in the journal Nature on 23 March 2015.

This chart of the position of a nova (marked in red) that appeared in the year 1670 was recorded by the famous astronomer Hevelius and was published by the Royal Society in England in their journal Philosophical Transactions. New observations made with APEX and other telescopes have now revealed that the star that European astronomers saw was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later. Credit: Royal Society
This chart of the position of a nova (marked in red) that appeared in the year 1670 was recorded by the famous astronomer Hevelius and was published by the Royal Society in England in their journal Philosophical Transactions.
New observations made with APEX and other telescopes have now revealed that the star that European astronomers saw was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later.
Credit:
Royal Society

Some of seventeenth century’s greatest astronomers, including Hevelius — the father of lunar cartography — and Cassini, carefully documented the appearance of a new star in the skies in 1670. Hevelius described it as nova sub capite Cygni — a new star below the head of the Swan — but astronomers now know it by the name Nova Vulpeculae 1670 [1]. Historical accounts of novae are rare and of great interest to modern astronomers. Nova Vul 1670 is claimed to be both the oldest recorded nova and the faintest nova when later recovered.

The lead author of the new study, Tomasz Kamiński (ESO and the Max Planck Institute for Radio Astronomy, Bonn, Germany) explains: “For many years this object was thought to be a nova, but the more it was studied the less it looked like an ordinary nova — or indeed any other kind of exploding star.”

When it first appeared, Nova Vul 1670 was easily visible with the naked eye and varied in brightness over the course of two years. It then disappeared and reappeared twice before vanishing for good. Although well documented for its time, the intrepid astronomers of the day lacked the equipment needed to solve the riddle of the apparent nova’s peculiar performance.

During the twentieth century, astronomers came to understand that most novae could be explained by the runaway explosive behaviour of close binary stars. But Nova Vul 1670 did not fit this model well at all and remained a mystery.

Even with ever-increasing telescopic power, the event was believed for a long time to have left no trace, and it was not until the 1980s that a team of astronomers detected a faint nebula surrounding the suspected location of what was left of the star. While these observations offered a tantalising link to the sighting of 1670, they failed to shed any new light on the true nature of the event witnessed over the skies of Europe over three hundred years ago.

This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the SMA (green) and finally a map of the molecular emission from APEX and the SMA (red). The star that European astronomers saw in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later. Credit: ESO/T. Kamiński
This picture shows the remains of the new star that was seen in the year 1670. It was created from a combination of visible-light images from the Gemini telescope (blue), a submillimetre map showing the dust from the SMA (green) and finally a map of the molecular emission from APEX and the SMA (red).
The star that European astronomers saw in 1670 was not a nova, but a much rarer, violent breed of stellar collision. It was spectacular enough to be easily seen with the naked eye during its first outburst, but the traces it left were so faint that very careful analysis using submillimetre telescopes was needed before the mystery could finally be unravelled more than 340 years later.
Credit:
ESO/T. Kamiński

 

Tomasz Kamiński continues the story: “We have now probed the area with submillimetre and radio wavelengths. We have found that the surroundings of the remnant are bathed in a cool gas rich in molecules, with a very unusual chemical composition.”

As well as APEX, the team also used the Submillimeter Array (SMA) and the Effelsberg radio telescope to discover the chemical composition and measure the ratios of different isotopes in the gas. Together, this created an extremely detailed account of the makeup of the area, which allowed an evaluation of where this material might have come from.

What the team discovered was that the mass of the cool material was too great to be the product of a nova explosion, and in addition the isotope ratios the team measured around Nova Vul 1670 were different to those expected from a nova. But if it wasn’t a nova, then what was it?

The answer is a spectacular collision between two stars, more brilliant than a nova, but less so than a supernova, which produces something called a red transient. These are a very rare events in which stars explode due to a merger with another star, spewing material from the stellar interiors into space, eventually leaving behind only a faint remnant embedded in a cool environment, rich in molecules and dust. This newly recognised class of eruptive stars fits the profile of Nova Vul 1670 almost exactly.

Co-author Karl Menten (Max Planck Institute for Radio Astronomy, Bonn, Germany) concludes: “This kind of discovery is the most fun: something that is completely unexpected!”

Notes
[1] This object lies within the boundaries of the modern constellation of Vulpecula (The Fox), just across the border from Cygnus (The Swan). It is also often referred to as Nova Vul 1670 and CK Vulpeculae, its designation as a variable star.

Source: ESO News

 

Fully experimental image of a nanoscaled and ultrafast optical rogue wave retrieved by Near-field Scanning Optical Microscope (NSOM). The flow lines visible in the image represent the direction of light energy. 
Credit: KAUST

Tsunami on demand: the power to harness catastrophic events

A new study published in Nature Physics features a nano-optical chip that makes possible generating and controlling nanoscale rogue waves. The innovative chip was developed by an international team of physicists, led by Andrea Fratalocchi from KAUST (Saudi Arabia), and is expected to have significant applications for energy research and environmental safety.

Can you imagine how much energy is in a tsunami wave, or in a tornado? Energy is all around us, but mainly contained in a quiet state. But there are moments in time when large amounts of energy build up spontaneously and create rare phenomena on a potentially disastrous scale. How these events occur, in many cases, is still a mystery.

To reveal the natural mechanisms behind such high-energy phenomena, Andrea Fratalocchi, assistant professor in the Computer, Electrical and Mathematical Science and Engineering Division of King Abdullah University of Science and Technology (KAUST), led a team of researchers from Saudi Arabia and three European universities and research centers to understand the dynamics of such destructive events and control their formation in new optical chips, which can open various technological applications. The results and implications of this study are published in the journal Nature Physics.

“I have always been fascinated by the unpredictability of nature,” Fratalocchi said. “And I believe that understanding this complexity is the next frontier that will open cutting edge pathways in science and offer novel applications in a variety of areas.”

Fratalocchi’s team began their research by developing new theoretical ideas to explain the formation of rare energetic natural events such as rogue waves — large surface waves that develop spontaneously in deep water and represent a potential risk for vessels and open-ocean oil platforms.”

“Our idea was something never tested before,” Fratalocchi continued. “We wanted to demonstrate that small perturbations of a chaotic sea of interacting waves could, contrary to intuition, control the formation of rare events of exceptional amplitude.”

Fully experimental image of a nanoscaled and ultrafast optical rogue wave retrieved by Near-field Scanning Optical Microscope (NSOM). The flow lines visible in the image represent the direction of light energy.  Credit: KAUST
Fully experimental image of a nanoscaled and ultrafast optical rogue wave retrieved by Near-field Scanning Optical Microscope (NSOM). The flow lines visible in the image represent the direction of light energy.
Credit: KAUST

A planar photonic crystal chip, fabricated at the University of St. Andrews and tested at the FOM institute AMOLF in the Amsterdam Science Park, was used to generate ultrafast (163 fs long) and subwavelength (203 nm wide) nanoscale rogue waves, proving that Fratalocchi’s theory was correct. The newly developed photonic chip offered an exceptional level of controllability over these rare events.

Thomas F. Krauss, head of the Photonics Group and Nanocentre Cleanroom at the University of York, UK, was involved in the development of the experiment and the analysis of the data. He shared, “By realizing a sea of interacting waves on a photonic chip, we were able study the formation of rare high energy events in a controlled environment. We noted that these events only happened when some sets of waves were missing, which is one of the key insights our study.”

Kobus Kuipers, head of nanophotonics at FOM institute AMOLF, NL, who was involved in the experimental visualization of the rogue waves, was fascinated by their dynamics: “We have developed a microscope that allows us to visualize optical behavior at the nanoscale. Unlike conventional wave behavior, it was remarkable to see the rogue waves suddenly appear, seemingly out of nowhere, and then disappear again…as if they had never been there.”

Andrea Di Falco, leader of the Synthetic Optics group at the University of St. Andrews said, “The advantage of using light confined in an optical chip is that we can control very carefully how the energy in a chaotic system is dissipated, giving rise to these rare and extreme events. It is as if we were able to produce a determined amount of waves of unusual height in a small lake, just by accurately landscaping its coasts and controlling the size and number of its emissaries.”

The outcomes of this project offer leading edge technological applications in energy research, high speed communication and in disaster preparedness.

Fratalocchi and the team believe their research represents a major milestone for KAUST and for the field. “This discovery can change once and for all the way we look at catastrophic events,” concludes Fratalocchi, “opening new perspectives in preventing their destructive appearance on large scales, or using their unique power for ideating new applications at the nanoscale.”The title of the Nature Physics paper is “Triggering extreme events at the nanoscale in photonic seas.” The paper is accessible on the Nature Photonics website: http://dx.doi.org/10.1038/nphys3263

Source : KAUST News

Stanford researchers solve the mystery of the dancing droplets

Years of research satisfy a graduate student’s curiosity about the molecular minuet he observed among drops of ordinary food coloring.

BY TOM ABATE


A puzzling observation, pursued through hundreds of experiments, has led Stanford researchers to a simple yet profound discovery: Under certain circumstances, droplets of fluid will move like performers in a dance choreographed by molecular physics.

“These droplets sense one another, they move and interact, almost like living cells,” said Manu Prakash, an assistant professor of bioengineering and senior author of an article published in Nature.

The unexpected findings may prove useful in semiconductor manufacturing and self-cleaning solar panels, but what truly excites Prakash is that the discovery resulted from years of persistent effort to satisfy a scientific curiosity.

Video: Stanford researchers solve the mystery of the dancing droplets

The research began in 2009 when Nate Cira, then an undergraduate at the University of Wisconsin, was doing an unrelated experiment. In the course of that experiment Cira deposited several droplets of food coloring onto a sterilized glass slide and was astonished when they began to move.

Cira replicated and studied this phenomenon alone for two years until he became a graduate student at Stanford, where he shared this curious observation with Prakash. The professor soon became hooked by the puzzle, and recruited a third member to the team: Adrien Benusiglio, a postdoctoral scholar in the Prakash Lab.

Together they spent three years performing increasingly refined experiments to learn how these tiny droplets of food coloring sense one another and move. In living cells these processes of sensing and motility are known as chemotaxis.

“We’ve discovered how droplets can exhibit behaviors akin to artificial chemotaxis,” Prakash said.

As the Nature article explains, the critical fact was that food coloring is a two-component fluid. In such fluids, two different chemical compounds coexist while retaining separate molecular identities

The droplets in this experiment consisted of two molecular compounds found naturally in food coloring: water and propylene glycol.

The researchers discovered how the dynamic interactions of these two molecular components enabled inanimate droplets to mimic some of the behaviors of living cells.

Surface tension and evaporation

Essentially, the droplets danced because of a delicate balance between surface tension and evaporation.

Evaporation is easily understood. On the surface of any liquid, some molecules convert to a gaseous state and float away.

Surface tension is what causes liquids to bead up. It arises from how tightly the molecules in a liquid bind together.

Water evaporates more quickly than propylene glycol. Water also has a higher surface tension.  These differences create a tornado-like flow inside the droplets, which not only allows them to move but also allows a single droplet to sense its neighbors.

To understand the molecular forces involved, imagine shrinking down to size and diving inside a droplet.

There, water and propylene glycol molecules try to remain evenly distributed but differences in evaporation and surface tension create turmoil within the droplet.

On the curved dome of each droplet, water molecules become gaseous and float away faster than their evaporation-averse propylene glycol neighbors.

This evaporation happens more readily on the thin lower edges of the domed droplet, leaving excess of propylene glycol there. Meanwhile, the peak of the dome has a higher concentration of water.

The water at the top exerts its higher surface tension to pull the droplet tight so it doesn’t flatten out. This tugging causes a tumbling molecular motion inside the droplet. Thus surface tension gets the droplet ready to roll.

Evaporation determines the direction of that motion. Each droplet sends aloft gaseous molecules of water like a radially emanating signal announcing the exact location of any given droplet. The droplets converge where the signal is strongest.

So evaporation provided the sensing mechanism and surface tension the pull to move droplets together in what seemed to the eye to be a careful dance.

Rule for two-component fluids

The researchers experimented with varied proportions of water and propylene glycol. Droplets that were 1 percent propylene glycol (PG) to 99 percent water exhibited much the same behavior as droplets that were two-thirds PG to just one-third water.

Based on these experiments the paper describes a “universal rule” to identify any two-component fluids that will demonstrate sensing and motility.

Adding colors to the mixtures made it easier to tell how the droplets of different concentrations behaved and created some visually striking results.

In one experiment, a droplet with more propylene glycol seems to chase a droplet with more water. In actuality, the droplet with more water exerts a higher surface tension tug, pulling the propylene droplet along.

In another experiment, researchers showed how physically separated droplets could align themselves using ever-so-slight signals of evaporation.

In a third experiment they used Sharpie pens to draw black lines on glass slides. The lines changed the surface of the slide and created a series of catch basins. The researchers filled each basin with fluids of different concentrations to create a self-sorting mechanism. Droplets bounced from reservoir to reservoir until they sensed the fluid that matched their concentration and merged with that pool.

What started as a curiosity-driven project may also have many practical implications.

The deep physical understanding of two component fluids allows the researchers to predict which fluids and surfaces will show these unusual effects. The effect is present on a large number of common surfaces and can be replicated with a number of chemical compounds.

“If necessity is the mother of invention, then curiosity is the father,” Prakash observed.

Source: Stanford News

Ant-Man possible? Scientists shrink ants to study mechanisms that control DNA expression

By shrinking ants to sizes smaller than exist in nature, biologists present a useful model for understanding how environmental factors can influence DNA expression to create a range of outcomes.

This may not be exactly what the Marvel’s Ant-Man story has but still close enough to be amazing! 

BY BJORN CAREY


In the pages of Marvel comic books, Ant-Man manipulates fictional subatomic particles in order to shrink and fight crime as one of Earth’s mightiest heroes.

In real life, a team of biologists has now achieved similar shrinking results by manipulating ants’ DNA. The work won’t produce any superpowers, but it presents a useful model for understanding how environmental factors can influence DNA expression to create a range of outcomes in a population.

The work is published online in the journal Nature Communications. Sebastian Alvarado, a postdoctoral fellow at Stanford, conducted the research as a graduate student at McGill University, working alongside fellow graduate student Rajendhran Rajakumar, and professors Ehab Abouheif and Moshe Szyf, all of McGill.

 

Video : Stanford researcher explains the science behind Ant-Man

The experiment was designed as a means to study variation in quantitative traits. These are individual qualities, such as height or body weight, that can naturally vary across a defined range in a population. This variation is usually driven by the degree that environmental or other factors influence the expression of a particular gene, which makes ants an excellent test model.

In an ant colony, queens, workers and soldiers share similar genetics. But early in ant development, social, nutritional and chemical cues cause some genes to be more active, ultimately creating a wide range of body sizes, each specialized to a different task in the colony.

Many of these changes are controlled by DNA methylation, a process in which molecules are added to sections of DNA sequences. These additions affect how the DNA is interpreted and expressed, thus influencing an organism’s development or behavior.

“A lot of growth and development and sizing mechanisms that exist across the animal kingdom are found to be regulated by the same DNA methylation processes,” Alvarado said.

In the experiment, Alvarado and his colleagues at McGill exposed ant larvae to drugs that either increased or decreased the amount of DNA methylation. In doing so, they created ants that were larger within a caste and even significantly smaller than what exists in a natural population.

They then traced this size change to a specific growth factor gene, and found that across the population, varying degrees of DNA methylation to that gene directly corresponded to body size. A 20 percent modification in DNA methylation yielded a 20 percent change in body size, for example.

“This helps explain at a molecular level how continuums exist between two very discrete variables,” said Alvarado, who is now a member of biology Professor Russell Fernald’s lab at Stanford. “We can now look at diversity within a population by considering what expressions exist in between these variables and the actual molecular mechanism that controls that difference.”

Drawing a stronger connection between how environment and genetic factors influence DNA expression, Alvarado said, could have payoff in mapping the genetic basis of diseases and understanding evolutionary changes.

Source: Stanford News