Ultracold Big Bang experiment successfully simulates evolution of early universe

Physicists have reproduced a pattern resembling the cosmic microwave background radiation in a laboratory simulation of the Big Bang, using ultracold cesium atoms in a vacuum chamber at the University of Chicago.

“This is the first time an experiment like this has simulated the evolution of structure in the early universe,” said Cheng Chin, professor in physics. Chin and his associates reported their feat in the Aug. 1 edition of Science Express, and it will appear soon in the print edition of Science.

Chin pursued the project with lead author Chen-Lung Hung, PhD’11, now at the California Institute of Technology, and Victor Gurarie of the University of Colorado, Boulder. Their goal was to harness ultracold atoms for simulations of the Big Bang to better understand how structure evolved in the infant universe.

The cosmic microwave background is the echo of the Big Bang. Extensive measurements of the CMB have come from the orbiting Cosmic Background Explorer in the 1990s, and later by the Wilkinson Microwave Anisotropy Probe and various ground-based observatories, including the UChicago-led South Pole Telescope collaboration. These tools have provided cosmologists with a snapshot of how the universe appeared approximately 380,000 years following the Big Bang, which marked the beginning of our universe.

It turns out that under certain conditions, a cloud of atoms chilled to a billionth of a degree above absolute zero (-459.67 degrees Fahrenheit) in a vacuum chamber displays phenomena similar to those that unfolded following the Big Bang, Hung said.

“At this ultracold temperature, atoms get excited collectively. They act as if they are sound waves in air,” he said. The dense package of matter and radiation that existed in the very early universe generated similar sound-wave excitations, as revealed by COBE, WMAP and the other experiments.

The synchronized generation of sound waves correlates with cosmologists’ speculations about inflation in the early universe. “Inflation set out the initial conditions for the early universe to create similar sound waves in the cosmic fluid formed by matter and radiation,” Hung said.

BIG BANG’S RIPPLING ECHO

The sudden expansion of the universe during its inflationary period created ripples in space-time in the echo of the Big Bang. One can think of the Big Bang, in oversimplified terms, as an explosion that generated sound, Chin said. The sound waves began interfering with each other, creating complicated patterns. “That’s the origin of complexity we see in the universe,” he said.

These excitations are called Sakharov acoustic oscillations, named for Russian physicist Andrei Sakharov, who described the phenomenon in the 1960s. To produce Sakharov oscillations, Chin’s team chilled a flat, smooth cloud of 10,000 or so cesium atoms to a billionth of a degree above absolute zero, creating an exotic state of matter known as a two-dimensional atomic superfluid.

Then they initiated a quenching process that controlled the strength of the interaction between the atoms of the cloud. They found that by suddenly making the interactions weaker or stronger, they could generate Sakharov oscillations.

The universe simulated in Chin’s laboratory measured no more than 70 microns in diameter, approximately the diameter as a human hair. “It turns out the same kind of physics can happen on vastly different length scales,” Chin explained. “That’s the power of physics.”

The goal is to better understand the cosmic evolution of a baby universe, the one that existed shortly after the Big Bang. It was much smaller then than it is today, having reached a diameter of only a hundred thousand light years by the time it had left the CMB pattern that cosmologists observe on the sky today.

In the end, what matters is not the absolute size of the simulated or the real universes, but their size ratios to the characteristic length scales governing the physics of Sakharov oscillations. “Here, of course, we are pushing this analogy to the extreme,” Chin said.

380,000 YEARS VERSUS 10 MILLISECONDS

“It took the whole universe about 380,000 years to evolve into the CMB spectrum we’re looking at now,” Chin said. But the physicists were able to reproduce much the same pattern in approximately 10 milliseconds in their experiment. “That suggests why the simulation based on cold atoms can be a powerful tool,” Chin said.

None of the Science co-authors are cosmologists, but they consulted several in the process of developing their experiment and interpreting its results. The co-authors especially drew upon the expertise of UChicago’s Wayne Hu, John Carlstrom and Michael Turner, and of Stanford University’s Chao-Lin Kuo.

Hung noted that Sakharov oscillations serve as an excellent tool for probing the properties of cosmic fluid in the early universe. “We are looking at a two-dimensional superfluid, which itself is a very interesting object. We actually plan to use these Sakharov oscillations to study the property of this two-dimensional superfluid at different initial conditions to get more information.”

The research team varied the conditions that prevailed early in the history of the expansion of their simulated universes by quickly changing how strongly their ultracold atoms interacted, generating ripples. “These ripples then propagate and create many fluctuations,” Hung said. He and his co-authors then examined the ringing of those fluctuations.

Today’s CMB maps show a snapshot of how the universe appeared at a moment in time long ago. “From CMB, we don’t really see what happened before that moment, nor do we see what happened after that,” Chin said. But, Hung noted, “In our simulation we can actually monitor the entire evolution of the Sakharov oscillations.”

Chin and Hung are interested in continuing this experimental direction with ultracold atoms, branching into a variety of other types of physics, including the simulation of galaxy formation or even the dynamics of black holes.

“We can potentially use atoms to simulate and better understand many interesting phenomena in nature,” Chin said. “Atoms to us can be anything you want them to be.”-

Source :University of Chicago.

By Science and Universe

Cassini Data: Saturn Moon May Have Rigid Ice Shell

This image of the surface of Saturn's moon Titan was obtained by the European Space Agency's

Huygens Probe on Jan. 14, 2005, after it was delivered to Titan by NASA's Cassini spacecraft.

Image Credit: 

ESA/NASA/JPL/University of Arizona

An analysis of gravity and topography data from the Saturnian moon Titan obtained by NASA's Cassini spacecraft suggests there could be something unexpected about the moon's outer ice shell. The findings, published on Aug. 28 in the journal Nature, suggest that Titan's ice shell could be rigid, and that relatively small topographic features on the surface could be associated with large ice "roots" extending into the underlying ocean.

The study was led by planetary scientists Douglas Hemingway and Francis Nimmo at the University of California, Santa Cruz, who used data from Cassini. The researchers were surprised to find a counterintuitive relationship between gravity and topography.

"Normally, if you fly over a mountain, you expect to see an increase in gravity due to the extra mass of the mountain," said Nimmo, a Cassini participating scientist. "On Titan, when you fly over a mountain, the gravity gets lower. That's a very odd observation."

One potential explanation is that each bump in the topography on the surface of Titan is offset by a deeper "root" that is big enough to overwhelm the gravitational effect of the bump on the surface. The root could act like an iceberg extending below the ice shell into the ocean underneath it. In this model, Cassini would detect less gravity wherever there is a big chunk of ice rather than water because ice is less dense than water.

"It's like a big beach ball under the ice sheet pushing up on it, and the only way to keep it submerged is if the ice sheet is strong," said Hemingway, the paper's lead author and a Cassini team associate. "If large roots under the ice shell are the explanation, this means that Titan's ice shell must have a very thick rigid layer."

If these findings are correct, a thick rigid ice shell makes it very difficult to have ice volcanoes, which some scientists have proposed to explain other features seen on the surface. They also suggest that convection or plate tectonics are not recycling Titan's ice shell, as they do with Earth's geologically active crust.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. The mission is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington.

More information on Cassini can be found at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov .

Source : NASA
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LADEE Fully Stacked on Minotaur V

The LADEE spacecraft in the nose-cone at the top of the full Minotaur V launch vehicle stack. LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.
Image Credit: NASA Wallops / Terry Zaperach

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft is now in the nose-cone at the top of the full Minotaur V launch vehicle stack at the Wallops Flight Facility in Virginia, awaiting a launch at 11:27 p.m. EDT on Sept. 6, 2013. 

Engineers at NASA's Wallops Flight Facility in Virginia prepare to encapsulate the LADEE spacecraft into the fairing of the Minotaur V launch vehicle nose-cone.
Image Credit: NASA Wallops / Terry Zaperach

Engineers at NASA's Wallops Flight Facility in Virginia encapsulate NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft into the fairing of the Minotaur V launch vehicle nose-cone.
Image Credit: NASA Wallops / Terry Zaperach.

NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft sits in the nose-cone at the top of the full Minotaur V launch vehicle stack.
Image Credit:
NASA Ames / Zion Young

LADEE is a robotic mission that will orbit the moon to gather detailed information about the lunar atmosphere, conditions near the surface and environmental influences on lunar dust. A thorough understanding of these characteristics will address long-standing unknowns, and help scientists understand other planetary bodies as well.

LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.

The probe will launch on a U.S. Air Force Minotaur V rocket, an excess ballistic missile converted into a space launch vehicle and operated by Orbital Sciences Corp. of Dulles, Va., from NASA's Wallops Flight Facility. 

Source : NASA

By Science and Universe

Lunar Atmosphere and Dust Environment Explorer

Click Here For Large Image

In an attempt to answer prevailing questions about our moon, NASA is making final preparations to launch a probe at 11:27 p.m. EDT Friday, Sept. 6, 2013, from NASA's Wallops Flight Facility on Wallops Island, Va.

The small car-sized Lunar Atmosphere and Dust Environment Explorer (LADEE) is a robotic mission that will orbit the moon to gather detailed information about the structure and composition of the thin lunar atmosphere and determine whether dust is being lofted into the lunar sky. A thorough understanding of these characteristics of our nearest celestial neighbor will help researchers understand other bodies in the solar system, such as large asteroids, Mercury, and the moons of outer planets.

In this photo, engineers as NASA's Wallops Flight Facility in Virginia encapsule the LADEE spacecraft into the fairing of the Minotaur V launch vehicle nose-cone. LADEE is the first spacecraft designed, developed, built, integrated and tested at NASA's Ames Research Center in Moffett Field, Calif.

Image credit: NASA Wallops / Terry Zaperach

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THE RE-ENTRY TEST IXV

Europe's newest spacecraft, the IXV, or Intermediate eXperimental Vehicle, has moved a step closer to its planned launch in 2014.

The craft completed a pre-launch test off the coast of Sardinia, which involved it being dropped into the Mediterranean from a height of 3,000 metres.

For the most part the vehicle performed perfectly during the test, with parachutes deploying as expected. However, just after splashdown a problem arose, as the inflatable devices which should add support to the buoyant IXV once it is in the water had failed to inflate.

It was a dramatic and initially confusing result, but after some head-scratching the engineers involved in the test began to understand what had happened. They believed that the balloons had not inflated because the setting for the sensors that detect the impact with the water was too high. So, splashdown was quite simply a little too gentle.

IXV Programme Manager for ESA, Giorgio Tumino explained: "There has been a lot of discussion around this, because we have to differentiate the shock induced by the impact with the water from the shock that could be induced by wind gusts to the parachute, because these are very similar levels in terms of shock and we have to differentiate those levels. We had set these thresholds quite high, and while my impression, my visual impression of what happened was that the landing was very soft because the parachute is really working fine, so probably the impact loads were much lower than what we expected."

Roberto Angelini from Thales Alenia Space was happy with the test overall: "We demonstrated what we wanted to demonstrate; free fall condition initially, you see the parachute compartment where we had the extraction of the parachute system. The slings of the parachute that are covered by a thermal protection system to sustain the heat of the re-entry, we wanted to test how this thing was going to be broken. And you see here the flotation devices that are activated right after the splashdown itself. Now, if there is something we will have to fix coming out from the post review board etc we will implement it in the flight hardware."

A post-flight review confirmed Tumino's theory. The impact loads during splashdown were lower than expected - the computers recorded an impact deceleration of 29.1 m/s2, and the threshold for the flotation of the balloons was set at 30 m/s2

A lot is riding on the IXV prototype, as it represents a new chapter in space flight technology for the European Space Agency.

The idea is to have an affordable, small spacecraft that can enter near-Earth orbit and then land in a targeted zone. This test was just one step in that development. In 2014 the IXV will be launched into space on board a Vega rocket and then re-enter the atmosphere, splashing down in the Pacific Ocean.

NASA's Spitzer Telescope Celebrates 10 Years in Space

A montage of images taken by NASA's Spitzer Space Telescope over the years.
Image Credit:  NASA/JPL-Caltech

Ten years after a Delta II rocket launched NASA's Spitzer Space Telescope, lighting up the night sky over Cape Canaveral, Fla., the fourth of the agency's four Great Observatories continues to illuminate the dark side of the cosmos with its infrared eyes. 

The telescope studied comets and asteroids, counted stars, scrutinized planets and galaxies, and discovered soccer-ball-shaped carbon spheres in space called buckyballs. Moving into its second decade of scientific scouting from an Earth-trailing orbit, Spitzer continues to explore the cosmos near and far. One additional task is helping NASA observe potential candidates for a developing mission to capture, redirect and explore a near-Earth asteroid.

"President Obama's goal of visiting an asteroid by 2025 combines NASA's diverse talents in a unified endeavor," said John Grunsfeld, NASA's associate administrator for science in Washington. "Using Spitzer to help us characterize asteroids and potential targets for an asteroid mission advances both science and exploration."

Spitzer's infrared vision lets it see the far, cold and dusty side of the universe. Close to home, the telescope has studied the comet dubbed Tempel 1, which was hit by NASA's Deep Impact mission in 2005. Spitzer showed the composition of Tempel 1 resembled that of solar systems beyond our own. Spitzer also surprised the world by discovering the largest of Saturn's many rings. The enormous ring, a wispy band of ice and dust particles, is very faint in visible light, but Spitzer's infrared detectors were able to pick up the glow from its heat.

Perhaps Spitzer's most astonishing finds came from beyond our solar system. The telescope was the first to detect light coming from a planet outside our solar system, a feat not in the mission's original design. With Spitzer's ongoing studies of these exotic worlds, astronomers have been able to probe their composition, dynamics and more, revolutionizing the study of exoplanet atmospheres.

Other discoveries and accomplishments of the mission include getting a complete census of forming stars in nearby clouds; making a new and improved map of the Milky Way's spiral-arm structure; and, with NASA's Hubble Space Telescope, discovering that the most distant galaxies known are more massive and mature than expected.

"I always knew Spitzer would work, but I had no idea that it would be as productive, exciting and long-lived as it has been," said Spitzer project scientist Michael Werner of NASA's Jet Propulsion Laboratory, Pasadena, Calif., who helped conceive the mission. "The spectacular images that it continues to return, and its cutting-edge science, go far beyond anything we could have imagined when we started on this journey more than 30 years ago."

In October, Spitzer will attempt infrared observations of a small near-Earth asteroid named 2009 DB to better determine its size, a study that will assist NASA in understanding potential candidates for the agency's asteroid capture and redirection mission. This asteroid is one of many candidates the agency is evaluating.

Spitzer, originally called the Space Infrared Telescope Facility, was renamed after its launch in honor of the late astronomer Lyman Spitzer. Considered the father of space telescopes, Lyman Spitzer began campaigning to put telescopes in space, away from the blurring effects of Earth's atmosphere, as early as the 1940s. His efforts also led to the development and deployment of NASA's Hubble Space Telescope, carried to orbit by the space shuttle in 1990.

In anticipation of the Hubble launch, NASA set up the Great Observatories program to fly a total of four space telescopes designed to cover a range of wavelengths: Hubble, Spitzer, the Chandra X-ray Observatory and the now-defunct Compton Gamma Ray Observatory.

"The majority of our Great Observatory fleet is still up in space, each with its unique perspective on the cosmos," said Paul Hertz, Astrophysics Division director at NASA headquarters in Washington. "The wisdom of having space telescopes that cover all wavelengths of light has been borne out by the spectacular discoveries made by astronomers around the world using Spitzer and the other Great Observatories."

Spitzer ran out of the coolant needed to chill its longer-wavelength instruments in 2009, and entered the so-called warm mission phase. Now, after its tenth year of peeling back the hidden layers of the cosmos, its journey continues.

"I get very excited about the serendipitous discoveries in areas we never anticipated," said Dave Gallagher, Spitzer's project manager at JPL from 1999 to 2004, reminding him of a favorite quote from Marcel Proust: "The real voyage of discovery consists not in seeking new landscapes, but in having new eyes."

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit http://spitzer.caltech.edu and http://www.nasa.gov/spitzer .

Source : NASA
BY Science and Universe

Embracing Orion

This new view of the Orion A star-formation cloud from ESA’s Herschel space observatory shows the turbulent region of space that hugs the famous Orion Nebula.

The nebula lies about 1500 light years from Earth within the ‘sword of Orion’ – below the three main stars that form the belt of the Orion constellation.

In this view, the nebula corresponds to the brightest region in the centre of the image, where it is lit up by the Trapezium group of stars at its heart.

The scene is awash with turbulent star formation, the fierce ultraviolet radiation of massive new born stars blasting away their surrounding cloudy cocoons, carving ethereal shapes into the gas and dust.

Wispy tendrils rise like flames away from some of the most intense regions of star formation, while pillars of denser material withstand the searing blaze for longer.

Great arms of gas and dust extend from the Orion Nebula to form a ring, while a spine of cooler material weaves up through the scene to a halo of cloudy star-formation material above.

Embedded within the red and yellow filaments are a handful of point-like sources: these are protostars, the seeds of new stars that will soon ignite and begin to flood their surrounds with intense radiation.

The black regions to the top of the image and to the bottom right may seem like voids, but actually contain hints of much fainter emission that has not been emphasised in this image.

The red ‘islands’ of emission in the bottom right are also a subtle trick of image processing for they are connected to the main cloud by much fainter emission. The bright ‘eyes’ in the two most distinct clouds indicates that the tip of each pillar has already collapsed and is forming stars.

Source : ESA

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Unprecedented Control of Genome Editing in Flies Promises Insight Into Human Development, Disease

UW-Madison researchers say fine control of genome editing in fruit flies promises to provide new
insights into embryonic development, nervous system function, and the understanding of human
disease. (Credit: Copyright Jeff Miller)

In an era of widespread genetic sequencing, the ability to edit and alter an organism's DNA is a powerful way to explore the information within and how it guides biological function.

A paper from the University of Wisconsin-Madison in the August issue of the journal Genetics takes genome editing to a new level in fruit flies, demonstrating a remarkable level of fine control and, importantly, the transmission of those engineered genetic changes across generations.

Both features are key for driving the utility and spread of an approach that promises to give researchers new insights into the basic workings of biological systems, including embryonic development, nervous system function, and the understanding of human disease.

"Genome engineering allows you to change gene function in a very targeted way, so you can probe function at a level of detail" that wasn't previously possible, says Melissa Harrison, an assistant professor of biomolecular chemistry in the UW-Madison School of Medicine and Public Health and one of the three senior authors of the new study.

Disrupting individual genes has long been used as a way to study their roles in biological function and disease. The new approach, based on molecules that drive a type of bacterial immune response, provides a technical advance that allows scientists to readily engineer genetic sequences in very detailed ways, including adding or removing short bits of DNA in chosen locations, introducing specific mutations, adding trackable tags, or changing the sequences that regulate when or where a gene is active.

The approach used in the new study, called the CRISPR RNA/Cas9 system, has developed unusually fast. First reported just one year ago by scientists at the Howard Hughes Medical Institute and University of California, Berkeley, it has already been applied to most traditional biological model systems, including yeast, zebrafish, mice, the nematode C. elegans, and human cells. The Wisconsin paper was the first to describe it in fruit flies and to show that the resulting genetic changes could be passed from one generation to the next.

"There was a need in the community to have a technique that you could use to generate targeted mutations," says Jill Wildonger, a UW-Madison assistant professor of biochemistry and another senior author of the paper. "The need was there and this was the technical advance that everyone had been waiting for."

"The reason this has progressed so quickly is that many researchers -- us included -- were working on other, more complicated, approaches to do exactly the same thing when this came out," adds genetics assistant professor Kate O'Connor-Giles, the third senior author. "This is invaluable for anyone wanting to study gene function in any organism and it is also likely to be transferable to the clinical realm and gene therapy."

The CRISPR RNA/Cas9 system directs a DNA-clipping enzyme called Cas9 to snip the DNA at a targeted sequence. This cut then stimulates the cell's existing DNA repair machinery to fill in the break while integrating the desired genetic tweaks. The process can be tailored to edit down to the level of a single base pair -- the rough equivalent of changing a single letter in a document with a word processor.

The broad applicability of the system is aided by a relatively simple design that can be customized through creation of a short RNA sequence to target a specific sequence in the genome to generate the desired changes. Previous genome editing methods have relied on making custom proteins, which is costly and slow.

"This is so readily transferable that it's highly likely to enable gene knockout and other genome modifications in any organism," including those that have not previously been used for laboratory work, says O'Connor-Giles. "It's going to turn non-model organisms into genetic model organisms."

That ease may also pay off in the clinic. "It can be very difficult and time-consuming to generate models to study all the gene variants associated with human diseases," says Wildonger. "With this genome editing approach, if we work in collaboration with a clinician to find [clinically relevant] mutations, we can rapidly translate these into a fruit fly model to see what's happening at the cellular and molecular level."

The work, led by genetics graduate student Scott Gratz, was the joint effort of three UW-Madison labs -- particularly notable, Harrison says, that each is in a different department and headed by a female assistant professor. "This has been an amazing collaboration," she says. "It wouldn't have worked if any one of us had tried it on our own."

A Fluffy Disk Around a Baby Star

Artist’s rendition of the "fluffy" layer associated with the protoplanetary disk of RY Tau, including jets coming from the star. Although typical young stars like RY Tau are often associated with jets, they are not visible in the HiCIAO observations at this time. (Credit: NAOJ)

An international team of astronomers that are members of the Strategic Exploration of Exoplanets and Disks with Subaru Telescope (SEEDS) Project has used Subaru Telescope's High Contrast Instrument for the Subaru Next Generation Adaptive Optics (HiCIAO) to observe a disk around the young star RY Tau (Tauri). The team's analysis of the disk shows that a "fluffy" layer above it is responsible for the scattered light observed in the infrared image. Detailed comparisons with computer simulations of scattered light from the disk reveal that this layer appears to be a remnant of material from an earlier phase of stellar and disk development, when dust and gas were falling onto the disk.

(left) An image in the near infrared (1.65 μm) around RY Tau, using a special mode of the HiCIAO coronagraph, the polarized intensity image. This type of observation is preferred for faint emissions associated with scattered light around planet-forming disks, as there is less light from the much brighter star. The colors indicate the strength of the emission (blue, yellow and red from faint to bright). A coronagraphic mask in the telescope optics blocks the central star, with its position marked at the center. A white ellipse shows the position of the midplane of the disk, which is observed at millimeter wavelengths. Scattered light observed in the near infrared is offset to the top of the image compared with the denser millimeter disk. (right) Schematic view of the observed infrared light. The light from the star is scattered in the upper dust layer, and it makes the observed light offset from the midplane. (Credit: NAOJ)

Since 2009, the five-year SEEDS Project (Note) has focused on direct imaging of exoplanets, i.e., planets orbiting stars outside of our Solar System, and disks around a targeted total of 500 stars. Planet formation, an exciting and active area for astronomical research, has long fascinated many scientists. Disks of dust and gas that rotate around young stars are of particular interest, because astronomers think that these are the sites where planets form--in these so-called "protoplanetary disks." Since young stars and disks are born in molecular clouds, giant clouds of dust and gas, the role of dust becomes an important feature of understanding planet formation; it relates not only to the formation of rocky, Earth-like planets and the cores of giant Jupiter-like planets but also to that of moons, planetary rings, comets, and asteroids.

As a part of the SEEDS Project, the current team of researchers used HiCIAO mounted on the Subaru Telescope to observe a possible planet-forming disk around the young star RY Tau. This star is about 460 light years away from Earth in the constellation Taurus and is around half a million years old. The disk has a radius of about 70 AU (10 billion kilometers), which is a few times larger than the orbit of Neptune in our own Solar System.

Astronomers have developed powerful instruments to obtain images of protoplanetary disks, and Subaru Telescope's HiCIAO is one of them. HiCIAO uses a mask to block out the light of the central star, which may be a million times brighter than its disk. They can then observe light from the star that has been reflected from the surface of the disk. The scattered light will reveal the structure of the surface of the disk, which is very small in scale and difficult to observe, even with large telescopes. Observers use HiCIAO with a 188 element adaptive optics system to reduce the blurring effects of Earthʼs atmosphere, making the images significantly sharper.

This team succeeded in capturing a near-infrared image (1.65 μm) associated with the RY Tau disk. Unlike many other protoplanetary disks, the disk emission is offset from the centre of the star. In contrast to longer wavelength observations, which are associated with the midplane of the disk, near-infrared, scattered light coming from the surface of the disk produced this offset, which provides information about the vertical structure of the disk.

Changes in structure perpendicular to the surface of a disk are much harder to investigate because there are few good examples to study. Therefore, the information about vertical structure that this image provides is a contribution to understanding the formation of planets, which depends strongly on the structure of the disk, including structures such as spirals and rings, as well as height.

Image : Computer simulation for dust scattering for RY Tau. The color indicates the strength of the modeled flux (blue, yellow and red for faint to bright). The white contours show the image observed using Subaru Telescope's HiCIAO. This modeled disk has a disk with a fluffy layer and closely matches the image in shape and brightness. (Credit: NAOJ)

The team performed extensive computer simulations of the scattered light, for disks with different masses, shapes, and types of dust. They found that the scattered light is probably not associated with the main surface of the disk, which is the usual explanation for the scattered light image. Instead, the observed infrared emission can be explained if the emission is associated with a fluffy upper layer, which is almost transparent and not completely transparent. The team estimated the dust mass in this layer to be about half the mass of Earthʼs Moon.

Image : Schematic views of the structure of the protoplanetary disk. The disk is transparent at millimeter wavelengths, and as a result, the observed millimeter emission is associated with the densest region (the midplane). In contrast, the disk is opaque in the infrared in even at the upper layer. Researchers often assume that the near-infrared emission is due to scattered light from its surface like figure (a). Figure (b) shows the revised schematic view through this study for RY Tau. There is another layer above the two layers in (a). This layer is almost transparent in the near-infrared, but not completely. The team concludes that the scattered emission observed using Subaru Telescope's HiCIAO is mainly due to scattering in this layer. (Credit: NAOJ)

Why is this fluffy layer observed in this disk, but not in many other possible planet-forming disks? The team suspects that this layer is a remnant of the dust that fell onto the star and the disk during earlier stages of formation. In most stars, unlike RY Tau, this layer dissipates by this stage in the formation of the star, but RY Tau may still have it because of its youth. It may act as a special comforter to warm the inside of the disk for baby planets being born there. This may affect the number, size, and composition of the planets being born in this system.

Source : National Astronomical Observatory of Japan.
By Science and Universe

Toxic Nanoparticles Might be Entering Human Food Supply, MU Study Finds

Graduate student Zhong Zhang applies silver nanoparticles to a piece of fruit. In a recent study, University of Missouri researchers found that these particles could pose a potential health risk to humans and the environment. (Credit: University of Missouri)

COLUMBIA, Mo. – Over the last few years, the use of nanomaterials for water treatment, food packaging, pesticides, cosmetics and other industries has increased. For example, farmers have used silver nanoparticles as a pesticide because of their capability to suppress the growth of harmful organisms. However, a growing concern is that these particles could pose a potential health risk to humans and the environment. In a new study, researchers at the University of Missouri have developed a reliable method for detecting silver nanoparticles in fresh produce and other food products.

“More than 1,000 products on the market are nanotechnology-based products,” said Mengshi Lin, associate professor of food science in the MU College of Agriculture, Food and Natural Resources. “This is a concern because we do not know the toxicity of the nanoparticles. Our goal is to detect, identify and quantify these nanoparticles in food and food products and study their toxicity as soon as possible.”

Lin and his colleagues, including MU scientists Azlin Mustapha and Bongkosh Vardhanabhuti, studied the residue and penetration of silver nanoparticles on pear skin. First, the scientists immersed the pears in a silver nanoparticle solution similar to pesticide application. The pears were then washed and rinsed repeatedly. Results showed that four days after the treatment and rinsing, silver nanoparticles were still attached to the skin, and the smaller particles were able to penetrate the skin and reach the pear pulp.

“The penetration of silver nanoparticles is dangerous to consumers because they have the ability to relocate in the human body after digestion,” Lin said. “Therefore, smaller nanoparticles may be more harmful to consumers than larger counterparts.”

When ingested, nanoparticles pass into the blood and lymph system, circulate through the body and reach potentially sensitive sites such as the spleen, brain, liver and heart.

The growing trend to use other types of nanoparticles has revolutionized the food industry by enhancing flavors, improving supplement delivery, keeping food fresh longer and brightening the colors of food. However, researchers worry that the use of silver nanoparticles could harm the human body.

“This study provides a promising approach for detecting the contamination of silver nanoparticles in food crops or other agricultural products,” Lin said.

Members of Lin’s research team also included Zhong Zang, a food science graduate student. The study was published in the Journal of Agricultural and Food Chemistry.

Source :University of Missouri-Columbia

By Science and Universe

Morphing manganese

This image shows a sediment sample from the Gulf of Saint Lawrence. Credit: George Luther, University of Delaware

An often-overlooked form of manganese, an element critical to many life processes, is far more prevalent in ocean environments than previously known, according to a study led by University of Delaware researchers that was published this week in "Science."

The discovery alters understanding of the chemistry that moves manganese and other elements, like oxygen and carbon, through the natural world. Manganese is an essential nutrient for most organisms and helps plants produce oxygen during photosynthesis.

"You wouldn't think manganese is that important, but without manganese, we wouldn't have the molecular oxygen that we breathe," said study co-author George Luther, Maxwell P. and Mildred H. Harrington Professor of Oceanography in the School of Marine Science and Policy within UD's College of Earth, Ocean, and Environment.

Manganese is present in the environment in three forms — manganese(II), manganese(III) and manganese(IV) — the difference related to the oxidation state, or number of electrons present. When elements lose or gain an electron, the oxidation state changes in a "redox reaction," like when iron turns into rust by losing electrons to oxygen in air.

The second-most common metal in the earth's crust, manganese rapidly changes between oxidation states while reacting with other elements in the environment.

Traditionally, manganese(II) and manganese(IV) were believed to be the dominant forms in aquatic environments. But in the mid-2000s, Luther found in a surprising result that manganese(III) was also present in a Black Sea "transition zone," an area where oxygen levels are relatively high near the surface but gradually diminish deeper down in the water.

Suspecting that this intermediary form was far more widespread than the somewhat unique conditions of the Black Sea, he and his Canadian colleagues Bjørn Sundby of the University of Quebec at Rimouski and Al Mucci of McGill University, whom he has worked with more than 20 years, set out for the largest estuary in the world: the Gulf of Saint Lawrence off the southeast corner of Canada.

There they pulled up samples of mud from the seafloor, where in the top few inches of sediment, there is also a transition zone of diminishing oxygen amounts. Andrew Madison, lead author on the Science paper and Luther's former graduate student, used a new technique to differentiate between manganese forms.

"It was a bit frustrating, and I spent about two and a half years working through methodological challenges and complications," said Madison, who finished his doctorate last year and now works as geochemist at Golder Associates Inc. in New Jersey. "But it was also pretty rewarding when I finally got something to work."

His results showed that manganese(III) comprised up to 90 percent of the total manganese present in the Canadian study sites. The implication is that the metal is found in other marine environments where there is a gradation of oxygen concentrations, whether in the water column of the Black Sea, sediment in the Gulf of Lawrence or a Delaware salt marsh.

"We saw it all through the Saint Laurentian Estuary where we studied," Luther said. "We did some work in a local salt marsh and found it. Wherever we've been able to look for it, we've found it. By implication, it should be found in all ocean sediments."

The findings help explain anomalies in manganese models that have puzzled scientists. Other researchers studying manganese did not make specific measurements for manganese(II) versus manganese(III), Luther said. Rather, they measured total dissolved manganese and assumed it was the former.

This missing link in the manganese cycle may shed light on the complex connections between the biology, geology and chemistry — called biogeochemistry — in ocean environments.

The biogeochemistry of marine sediments revolves around organic matter, like bits of dead algae, that fall through the water to the bottom of the ocean. Bacteria consume that debris, setting off a chain of reactions.

"In sediments, bacteria prefer to consume molecular oxygen and nitrate first due to their high energy gain," Madison said. "After those are consumed, bacteria then couple organic matter oxidation to manganese oxide reduction, which can produce soluble manganese(III)."

In their paper, the researchers call for the conceptual model of the sedimentary redox cycle to be revised to include dissolved manganese(III).

"Manganese is helpful to produce organic matter in the surface waters through photosynthesis," Luther said. "But in the sediments, the higher oxidation state manganese is used to decompose organic matter. So it's a really interesting cycle."

Luther, his students and his Oregon Health & Science University collaborator, Brad Tebo, plan to return to Canada to continue work on the microbiology and chemistry of the processes, hopefully to find out which organisms are helping the manganese oxidation process.

Source : Eurekalert

By Science and Universe