Astronomy - Existence of exoplanet 'Fomalhaut b' called into question

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An exoplanet called Fomalhaut b has been photographed in an unexpected spot — so is it even an exoplanet at all? Image credit: NASA

Fomalhaut b, thought to be the first exoplanet photographed directly, has come under increased scrutiny due to evidence of an unexpected divergence from its expected orbit. Paul Kalas, James Graham and their colleagues identified the planet in 2008 while studying photographs taken by the Hubble telescope in 2004 and 2006. At that time it appeared Fomalhaut b orbited just inside a dust cloud that circles around Fomalhaut, the star at the center of that solar system. Now however, new photographs of Fomalhaut b show that it actually crosses into the dust cloud, causing Toronto astronomer Ray Jayawardhana, at a recent exoplanet conference, to suggest that Fomalhaut b may not be an exoplanet after all.

The whole story actually began back in 2005 when evidence arose from studies of the dust belt surrounding Fomalhaut, suggesting that at least one exoplanet (any planet not in our own solar system) existed in the system due to the behavior of the dust cloud. After years of studying photographs from Hubble, Kalas and his team came upon Fomalhaut b, an apparent exoplanet about the size of Jupiter (and three times its mass), orbiting some 1.72×10¹⁰ km from its sun. Unfortunately, more evidence regarding the exoplanet could not be had due to the malfunction of the camera onboard Hubble. It wasn’t until just last year that another picture of Fomalhaut b was finally made using a different camera on Hubble. The problem was, the exoplanet appeared in a different place than astronomers expected; a problem that has various astronomers offering various explanations. Some suggest that the projected orbit was wrong, while others say that maybe it’s not a planet at all, but a background star or something else altogether.

Another problem is that there are other apparent anomalies as well. It’s too bright for its size example. Also, why aren’t other ground-based infrared telescopes able to detect its presence? Jayawardhana says that all of this combined information or lack thereof, should be enough to have Fomalhaut b removed from the exoplanet.eu database. Kalas, in response suggests that 1RXJ1609, an exoplanetthat Jayawardhana and his team are studying, should be reviewed more closely as well.

The whole argument, if that’s what it is, appears to suggest that perhaps more stringent means should be established for classifying exoplanets before they are announced as such. Also maybe, those astronomers in the field who seem to be just as interested in the limelight as in making new discoveries should perhaps take a closer look at how they are coming off to those reading about their spats in the press.

Source: PhysOrg.com

Astronomy - Star formation laws

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NGC 1569 - a relatively close (11 million light years) starburst galaxy - presumably the result of some fairly efficient star formation processes. Credit: NASA/HST.

Take a cloud of molecular hydrogen add some turbulence and you get star formation – that’s the law. The efficiency of star formation (how big and how populous they get) is largely a function of the density of the initial cloud.

At a galactic or star cluster level, a low gas density will deliver a sparse population of generally small, dim stars – while a high gas density should result in a dense population of big, bright stars. However, overlying all this is the key issue of metallicity – which acts to reduce star formation efficiency.

So firstly, the strong relationship between the density of molecular hydrogen (H₂) and star formation efficiency is known as the Kennicutt-Schmidt Law. Atomic hydrogen is not considered to be able to support star formation, because it is too hot. Only when it cools to form molecular hydrogen can it start to clump together – after which we can expect star formation to become possible. Of course, this creates some mystery about how the first stars might have formed within a denser and hotter primeval universe. Perhaps dark matter played a key role there.

Nonetheless, in the modern universe, unbound gas can more readily cool down to molecular hydrogen due the presence of metals, which have been added to the interstellar medium by previous populations of stars. Metals, which are any elements heavier than hydrogen and helium, are able to absorb a wider range of radiation energy levels, leaving hydrogen less exposed to heating. Hence, a metal-rich gas cloud is more likely to form molecular hydrogen, which is then more likely to support star formation.

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Relationship between the power of stellar winds and stellar mass (i.e. big star has big wind) - with the effect of metallicity overlaid. The solid line is the metallicity of the Sun (Z=Zsol). High metallicity produces more powerful winds for the same stellar mass. Credit: Dib et al.

But this does not mean that star formation is more efficient in the modern universe – and again this is because of metals. A recent paper about the dependence of star formation on metallicity proposes that a cluster of stars develops from H₂ clumping within a gas cloud, first forming prestellar cores which draw in more matter via gravity, until they become stars and then begin producing stellar wind.

Before long, the stellar wind begins to generate ‘feedback’, countering the infall of further material. Once the outward push of stellar wind achieves unity with the inward gravitational pull, further star growth ceases – and bigger O and B class stars clear out any remaining gas from the cluster region, so that all star formation is quenched. 

The dependence of star formation efficiency on metallicity arises from the effect of metallicity on stellar wind. High metal stars always have more powerful winds than any equivalent mass, but lower metal, stars. Thus, a star cluster – or even a galaxy – formed from a gas cloud with high metallicity, will have lower efficiency star formation. This is because all stars’ growth is inhibited by their own stellar wind feedback in late stages of growth and any large O or B class stars will clear out any remaining unbound gas more quickly than their low metal equivalents.

This metallicity effect is likely to be the product of ‘radiative line acceleration’, arising from the ability of metals to absorb radiation across a wide range of radiation energy levels – that is, metals present many more radiation absorption lines than hydrogen has on its own. The absorption of radiation by an ion means that some of the momentum energy of a photon is imparted to the ion, to the extent that such ions may be blown out of the star as stellar wind. The ability of metals to absorb more radiation energy than hydrogen can, means you should always get more wind (i.e. more ions blown out) from high metal stars.

More information: Dib et al. The Dependence of the Galactic Star Formation Laws on Metallicity.

Universe Today

Source: PhysOrg.com

"Our Universe Continually Cycles through a Series of 'Aeons'"

The circular patterns within the cosmic microwave background suggest that space and time did not come into being at the Big Bang but that our universe in fact continually cycles through a series of "aeons," according to University of Oxford theoretical physicist Roger Penrose, who says that data collected by NASA's WMAP satellite supports his idea of "conformal cyclic cosmology".

Penrose's finding runs directly counter to the widely accepted inflationary model of cosmology which states that the universe started from a point of infinite density known as the Big Bang about 13.7 billion years ago, expanded extremely rapidly for a fraction of a second and has continued to expand much more slowly ever since, during which time stars, planets and ultimately humans have emerged. That expansion is now believed to be accelerating due to a scientific X factor called dark energy and is expected to result in a cold, uniform, featureless universe.


Penrose, however, said Physics World, takes issue with the inflationary picture "and in particular believes it cannot account for the very low entropy state in which the universe was believed to have been born – an extremely high degree of order that made complex matter possible. He does not believe that space and time came into existence at the moment of the Big Bang but that the Big Bang was in fact just one in a series of many, with each big bang marking the start of a new "aeon" in the history of the universe."

The core concept in Penrose's theory is the idea that in the very distant future the universe will in one sense become very similar to how it was at the Big Bang. Penrose says that "at these points the shape, or geometry, of the universe was and will be very smooth, in contrast to its current very jagged form. This continuity of shape, he maintains, will allow a transition from the end of the current aeon, when the universe will have expanded to become infinitely large, to the start of the next, when it once again becomes infinitesimally small and explodes outwards from the next big bang. Crucially, he says, the entropy at this transition stage will be extremely low, because black holes, which destroy all information that they suck in, evaporate as the universe expands and in so doing remove entropy from the universe."

The foundation for Penrose's theory is found in the cosmic microwave background, the all-pervasive microwave radiation that was believed to have been created when the universe was just 300,000 years old and which tells us what conditions were like at that time.

The evidence was obtained by Vahe Gurzadyan of the Yerevan Physics Institute in Armenia, who analysed seven years' worth of microwave data from WMAP, as well as data from the BOOMERanG balloon experiment in Antarctica. Penrose and Gurzadyan say they have clearly identified concentric circles within the data – regions in the microwave sky in which the range of the radiation's temperature is markedly smaller than elsewhere.

The Cosmic Microwave Background (CMB) radiation is the remnant heat from the Big Bang. This radiation pervades the universe and, if we could see in microwaves, it would appear as a nearly uniform glow across the entire sky. However, when we measure this radiation very carefully we can discern extremely faint variations in the brightness from point to point across the sky, called "anisotropy". These variations encode a great deal of information about the properties of our universe, such as its age and content.

The "Wilkinson Microwave Anisotropy Probe" (WMAP) mission has measured these variations and found that the universe is 13.7 billion years old, and it consists of 4.6% atoms, 23% dark matter, and 72% dark energy.

According to Penrose and Gurzadyan, as described in arXiv: 1011.3706, these circles allow us to "see through" the Big Bang into the aeon that would have existed beforehand. They are the visible signature left in our aeon by the spherical ripples of gravitational waves that were generated when black holes collided in the previous aeon.

The "Penrose circles" pose a huge challenge to inflationary theory because this theory says that the distribution of temperature variations across the sky should be Gaussian, or random, rather than having discernable structures within it.

Julian Barbour, a visiting professor of physics at the University of Oxford in an interview with Physics World, says that these circles would be "remarkable if real and sensational if they confirm Penrose's theory". They would "overthrow the standard inflationary picture", which, he adds, has become widely accepted as scientific fact by many cosmologists. But he believes that the result will be "very controversial" and that other researchers will look at the data very critically. He says there are many disputable aspects to the theory, including the abrupt shift of scale between aeons and the assumption, central to the theory, that all particles will become massless in the very distant future. He points out, for example, that there is no evidence that electrons decay.

The image below shows the CMB fluctuations from the 5-year WMAP survey. The average brightness corresponds to a temperature of 2.725 Kelvins (degrees above absolute zero; equivalent to -270 C or -455 F). The colors represent temperature variations, as in a weather map: red regions are warmer and blue regions are colder than average by 0.0002 degrees. This map was formed from the five frequency bands shown below in such a way as to suppress the signal from our own Milky Way Galaxy.

Physics World 

Source: The Daily Galaxy 

Did Our Human "Super Brain" Suddenly Appear 75,000 Years Ago?

 

There is mounting archaeological evidence for the evolution of a human "super-brain" no later than 75,000 years ago that spurred a modern capacity for novelty and invention, according to John Hoffecher, an archaeologist at the University of Colorado.


While the concept of a human super-brain is analogous to social insects like bees and ants, which collectively behave as a super-organism by gathering, processing, and sharing information about their environment, there is one important difference, Hoffecker said. “Human societies are not super-organisms -- they are composed of people who are for the most part unrelated, and societies filled with competing individuals and families.”

While crude stone tools crafted by human ancestors beginning about 2.5 million years ago likely were an indirect consequence of bipedalism (walking upright) -- which freed up the hands for new functions -- the first inklings of a developing super-brain likely began about 1.6 million years ago when early humans began crafting stone hand axes, thought by Hoffecker and others to be one of the first external representations of internal thought.

The emerging modern mind in Africa was marked by a three-fold increase in brain size over 3-million-year-old human ancestors like Lucy, thought by some to be the matriarch of modern humans. Humans were producing perforated shell ornaments, polished bone awls and simple geometric designs incised into lumps of red ochre by 75,000 years ago. “With the appearance of symbols and language -- and the consequent integration of brains into a super-brain -- the human mind seems to have taken off as a potentially unlimited creative force,” Hoffecker said.

Since the emergence of the modern industrial world beginning roughly 500 years ago, creativity driven by the human super-brain has grown by leaps and bounds, from the invention of mechanical clocks to space shuttles.

Powerful artificial intelligence could blur the differences between humans and computers in the coming centuries, Hoffecker said.

Stephen Hawking agrees with Hoffecker. Although It has taken homo sapiens several million years to evolve from the apes, the useful information in our DNA, has probably changed by only a few million bits. So the rate of biological evolution in humans, Stephen Hawking points out in his Life in the Universe lecture, is about a bit a year.

"By contrast," Hawking says, "there are about 50,000 new books published in the English language each year, containing of the order of a hundred billion bits of information. Of course, the great majority of this information is garbage, and no use to any form of life. But, even so, the rate at which useful information can be added is millions, if not billions, higher than with DNA."

This means Hawking says that we have entered a new phase of evolution. "At first, evolution proceeded by natural selection, from random mutations. This Darwinian phase, lasted about three and a half billion years, and produced us, beings who developed language, to exchange information."

But what distinguishes us from our cave man ancestors is the knowledge that we have accumulated over the last ten thousand years, and particularly, Hawking points out, over the last three hundred.

"I think it is legitimate to take a broader view, and include externally transmitted information, as well as DNA, in the evolution of the human race," Hawking said.

In the last ten thousand years the human species has  been in what Hawking calls, "an external transmission phase," where the internal record of information, handed down to succeeding generations in DNA, has not changed significantly. "But the external record, in books, and other long lasting forms of storage," Hawking says, "has grown enormously. Some people would use the term, evolution, only for the internally transmitted genetic material, and would object to it being applied to information handed down externally. But I think that is too narrow a view. We are more than just our genes."

The time scale for evolution, in the external transmission period, has collapsed to about 50 years, or less.

Stephen-hawking Meanwhile, Hawking observes, our human brains "with which we process this information have evolved only on the Darwinian time scale, of hundreds of thousands of years. This is beginning to cause problems. In the 18th century, there was said to be a man who had read every book written. But nowadays, if you read one book a day, it would take you about 15,000 years to read through the books in a national Library. By which time, many more books would have been written."

But we are now entering a new phase, of what Hawking calls "self designed evolution," in which we will be able to change and improve our DNA. "At first," he continues "these changes will be confined to the repair of genetic defects, like cystic fibrosis, and muscular dystrophy. These are controlled by single genes, and so are fairly easy to identify, and correct. Other qualities, such as intelligence, are probably controlled by a large number of genes. It will be much more difficult to find them, and work out the relations between them. Nevertheless, I am sure that during the next century, people will discover how to modify both intelligence, and instincts like aggression."

If the human race manages to redesign itself, to reduce or eliminate the risk of self-destruction, we will probably reach out to the stars and colonize other planets. But this will be done, Hawking believes, with intelligent machines based on mechanical and electronic components, rather than macromolecules, which could eventually replace DNA based life, just as DNA may have replaced an earlier form of life.

Source: The Daily Galaxy

Does Our Solar System Exist Inside a Bubble? Astronomers Say "Yes"

We seem to be inside a "local bubble" in a network of cavities in the interstellar medium, probably carved by massive star explosions millions of years ago. The interstellar medium (or ISM) is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space.


The ISM plays a crucial role in astrophysics precisely because of its intermediate role between stellar and galactic scales, with stars forming within the densest regions of the ISM and molecular clouds, and replenishes the ISM with matter and energy through planetary nebulae, stellar winds, and supernovae.

This interplay between stars and the ISM helps determine the rate at which a galaxy depletes its gaseous content, and therefore its lifespan of active star formation.

NASA astronomer's best guess is depicted in the map (below) of the surrounding 1500 light years constructed from multiple observations and deductions. Currently, the Sun is passing through a Local Interstellar Cloud (LIC), shown in violet, which is flowing away from the Scorpius-Centaurus Association of young stars (image above).

The LIC resides in a low-density hole in the interstellar medium (ISM) called the Local Bubble, shown in black. Nearby, high-density molecular clouds including the Aquila Rift surround star forming regions, each shown in orange.

The Gum Nebula, shown above and below in green, is a region of hot ionized hydrogen gas. This complex nebula is thought to be a supernova remnant over a million years old, sprawling across the southern constellations Vela and Puppis. Inside the Gum Nebula is the Vela Supernova Remnant, shown in pink, which is expanding to create fragmented shells of material like the LIC. Future observations will aid astronomers to learn more about the local Galactic Neighborhood and how it might have affected Earth's past climate.

Over 13 billion years ago at least one of the domains of life may have begun in nebular clouds. If restricted to the Milky Way, which is 13.6 billion years old, the first chemical combinations would have had billions of years to become a self-replicating organism with a DNA genome long before the existence of Earth.

Nebular clouds are thought to be most likely environment for synthesizing and promoting the evolution of molecules needed for the origin of life. The building blocks for DNA could have been generated or combined within interstellar clouds and DNA would become part of the molecular-protein-amino acid complex. Hydrogen, oxygen, carbon, calcium, sulfur, nitrogen and phosphorus for example are continually irradiated by ions, which can generate small organic molecules which evolve into larger complex organic molecules that result in the formation of amino acids and other compounds.

Phosphorus, for example, is rare in our solar system and may have been non-existent on the early Earth; phosphorus is essential for the manufacture of DNA.

Polarized radiation in the nebula cloud leads to the formation of proteins, nucleobases and then DNA. The combination of hydrogen, carbon, oxygen, nitrogen, cyanide and several other elements, could create adenine, which is a DNA base, whereas oxygen and phosphorus could ladder DNA base pairs. Glycine has also been identified in the interstellar clouds.

Fast forward 4.6 billion years, on Earth the steps leading from the random mixing of chemicals to the first nano-particle would likely require hundreds of millions and even billions of years before the first self-replicating molecular compound was fashioned. Even after billions of years, the first replicon may not have possessed DNA.

 NASA

Source: The Daily Galaxy 

"The Undetectability Conjecture" -- A Radical Theory for the 'Great Silence'

 

The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations. As Enrico Fermi asked if the Universe is conducive to intelligent life, “Where is everybody?”


A new answer proposed by Adrian Kent of the University of Cambridge and Perimeter Institute, is that extraterrestial life sufficiently advanced to be capable of interstellar travel or communication must be rare, since otherwise we would have seen evidence of it by now. This in turn is sometimes taken as indirect evidence for the improbability of life evolving at all in our universe.

“Intelligent species might reasonably worry about the possible dangers of self-advertisement and hence incline towards discretion” -- the “Undetectability Conjecture,” put forth by Beatriz Gato-Rivera, a theoretical physicist at the Instituto de Fisica Fundamental (previously Instituto de Matematicas y Fisica Fundamental) of the CSIC (Spanish Scientific Research Council) in Madrid. According to Gato-Rivera, we may find ourselves in a universe in which there exist intelligent technological civilizations but they have chosen to be undetectable, camouflaging themselves mainly for security reasons (because advanced civilizations could also be aggressive).

“Evolutionary selection, acting on a cosmic scale," Kent adds. "tends to extinguish species which conspicuously advertise themselves and their habitats.”

“It often seems, Kent concludes, "to be implicitly assumed, and sometimes is explicitly argued, that colonising or otherwise exploiting the resources of other planets and other solar systems will solve our problems when the Earth’s resources can no longer sustain our consumption. It might perhaps be worth contemplating more seriously the possibility that there may be limits to the territory we can safely colonise and to the resources we can safely exploit, and to consider whether and how it might be possible to evolve towards a way of living that can be sustained (almost) indefinitely on the resources of (say) our solar system alone.”

In another take on the "Fermi Paradox," Stephen Hawking asks In his famous lecture on Life in the Universe: "What are the chances that we will encounter some alien form of life, as we explore the galaxy?"

If the argument about the time scale for the appearance of life on Earth is correct, Hawking says "there ought to be many other stars, whose planets have life on them. Some of these stellar systems could have formed 5 billion years before the Earth. So why is the galaxy not crawling with self-designing mechanical or biological life forms?"

Why hasn't the Earth been visited, and even colonized? Hawking asks. "I discount suggestions that UFO's contain beings from outer space. I think any visits by aliens, would be much more obvious, and probably also, much more unpleasant."

Hawking continues: "What is the explanation of why we have not been visited? One possibility is that the argument, about the appearance of life on Earth, is wrong. Maybe the probability of life spontaneously appearing is so low, that Earth is the only planet in the galaxy, or in the observable universe, in which it happened. Another possibility is that there was a reasonable probability of forming self reproducing systems, like cells, but that most of these forms of life did not evolve intelligence."

We are used to thinking of intelligent life, as an inevitable consequence of evolution, Hawking emphasized,  but it is more likely that evolution is a random process, with intelligence as only one of a large number of possible outcomes.

Intelligence, Hawking believes contrary to our human-centric existece, may not have any long-term survival value. In comparison the microbial world, will live on, even if all other life on Earth is wiped out by our actions. Hawking's main insight is that intelligence was an unlikely development for life on Earth, from the chronology of evolution:  "It took a very long time, two and a half billion years, to go from single cells to multi-cell beings, which are a necessary precursor to intelligence. This is a good fraction of the total time available, before the Sun blows up. So it would be consistent with the hypothesis, that the probability for life to develop intelligence, is low. In this case, we might expect to find many other life forms in the galaxy, but we are unlikely to find intelligent life."

Another possibility is that there is a reasonable probability for life to form, and to evolve to intelligent beings, but at some point in their technological  development "the system becomes unstable, and the intelligent life destroys itself. This would be a very pessimistic conclusion. I very much hope it isn't true."

Hawkling prefers another possibility: that there are other forms of intelligent life out there, but that we have been overlooked. If we should pick up signals from alien civilizations, Hawking warns,"we should have to be wary of answering back, until we have evolved" a bit further. Meeting a more advanced civilization, at our present stage, Hawking says, "might be a bit like the original inhabitants of America meeting Columbus. I don't think they were better off for it."

Source: The Daily Galaxy  

[Image] Galaxy M82 -Home of a Mystery Signal Unlike Anything in the Known Universe

 

M82, a starburst galaxy was previously believed to be an irregular galaxy. However, in 2005, two symmetric spiral arms were discovered in the near-infrared (NIR) images of M82. The arms were detected by subtracting an axisymmetric exponential disk from the NIR images.


In April 2010, radio astronomers working at the Jodrell Bank Observatory of the University of Manchester reported an unknown object in M82. The object has started sending out radio waves, and the emission does not look like anything seen anywhere in the universe before. There have been several theories about the nature of this unknown object, but currently no theory entirely fits the observed data. It has been suggested that the object could be a "micro quasar", having very high luminosity, and being fairly stable. However, microquasars also produce large quantities of X-rays, whereas no X-rays have been seen from the mystery object.The object is located at several arcseconds from the center of M82.

Chandra X Ray Space Telescope

Source: The Daily Galaxy 

General Physics - 3 Questions: Faster than light?

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View of the OPERA detector (on the CNGS facility) with its two identical Super Modules, each one containing one target section and one spectrometer. Image: CERN

The news media were abuzz this week with reports of experiments conducted at the Gran Sasso particle detector complex in Italy, apparently showing subatomic particles called neutrinos had traveled from the giant particle accelerator at CERN, outside Geneva, to the Italian detector at a speed just slightly faster than the speed of light -- a result that, if correct, would overturn more than a century of accepted physics theory. Professor of Physics Peter Fisher, head of MIT's Particle and Nuclear Experimental Physics division, answered some questions about these new findings.

Q. If this result is confirmed, does it really undermine Einstein’s theory of relativity, as some news reports claim? And if so, is there a theory that’s been proposed that might account for it?

A. Einstein’s theory rests on two postulates, one of which is that electromagnetic radiation travels at the same speed (the speed of light, 300,000 kilometers per second) no matter how the observer moves. Light particles — photons — have no mass, so a consequence is that no particle with mass can move at a velocity greater than light. These neutrinos have a tiny, but non-zero, mass and hence should not be able to travel faster than the speed of light.

There are theories that predict particles moving faster than the speed of light, but, to my knowledge, none of them account for all the other phenomena we have measured experimentally since the time of Einstein.

Q. What kind of other tests or independent experiments would it take to confirm this result so that it would be widely accepted?

A. There are two other experiments that shoot neutrinos over long distances that may have something to say about this result. One experiment is in the U.S., and the beam goes from Fermilab, near Chicago, to a detector called MINOS in northern Minnesota. The other shoots a neutrino beam across Japan to an experiment in a mine called Super-Kamiokande. The energies of the neutrinos in these experiments are much lower than the CERN beam, but they may have something to say very soon.

Q. If this turns out to be some kind of unrecognized systematic error in the measurements, would that reflect badly on the scientists who reported it, or would it just be a reflection of science working as it’s supposed to?

A. I would say more the latter. I know a number of the people on the OPERA experiment [at Gran Sasso] and they are very thoughtful, careful people who would never publish a result like this unless they were certain there was no better explanation. I would bet that whatever the explanation is, it will be very interesting.

Massachusetts Institute of Technology (news : web)

Source: PhysOrg.com

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