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Saturday, November 30, 2013

10 Years Above Mars, High Resolution Movie

From the highest volcano to the deepest canyon, from impact craters to ancient river beds and lava flows, this showcase of images from ESA's Mars Express takes you on an unforgettable journey across the Red Planet.

Mars Express was launched on 2 June 2003 and arrived at Mars six-and-a-half months later. It has since orbited the planet nearly 12 500 times, providing scientists with unprecedented images and data collected by its suite of scientific instruments.


The data have been used to create an almost global digital topographic model of the surface, providing a unique visualisation and enabling researchers to acquire new and surprising information about the evolution of the Red Planet.

Valles Marineris on Mars


Credit: ESA / DLR / FU Berlin (G. Neukum)

The images in this movie were taken by the High Resolution Stereo Camera and the video was released by the DLR German Aerospace Center as part of the ten years of Mars Express celebrations in June 2013. The music has been created by Stephan Elgner of DLR's Mars Express planetary cartography team. DLR developed and is operating the stereo camera.

Color-coded elevation model of Olympus Mons
Credit:   ESA / DLR / FU Berlin (G. Neukum)


Contact and sources:
European Space Agency, ESA
Read the original post on DLR's website here:http://www.dlr.de/dlr/en/desktopdefau...

Black Holes Have Simple Feeding Habits

At the center of spiral galaxy M81 is a supermassive black hole about 70 million times more massive than our sun.

A study using data from Chandra and ground-based telescopes, combined with detailed theoretical models, shows that the supermassive black hole in M81 feeds just like stellar mass black holes, with masses of only about ten times that of the sun. This discovery supports Einstein's relativity theory that states black holes of all sizes have similar properties.

Image Credit: X-ray: NASA/CXC/Wisconsin/D.Pooley & CfA/A.Zezas; Optical: NASA/ESA/CfA/A.Zezas; UV: NASA/JPL-Caltech/CfA/J.Huchra et al.; IR: NASA/JPL-Caltech/CfA

Important Step In Creating Synthetic Life Taken

A team of Massachusetts General Hospital (MGH) investigators working to create "protocells" – primitive synthetic cells consisting of a nucleic acid strand encased within a membrane-bound compartment – have accomplished an important step towards their goal. In the November 28 issue of Science, the investigators describe a solution to what could have been a critical problem – the potential incompatibility between a chemical requirement of RNA copying and the stability of the protocell membrane.

"For the first time, we've been able to do nonenzymatic RNA copying inside fatty acid vesicles," says Jack Szostak, PhD, of the MGH Department of Molecular Biology and the Center for Computational and Integrative Biology. "We've found a solution to a longstanding problem in the origin of cellular life: RNA copying chemistry requires the presence of the magnesium ion Mg2+, but high Mg2+ levels can break down the simple, fatty acid membranes that probably surrounded the first living cells."

RNA replication in model protocell:  Left to right, upper sequence: As protocells replicate their nucleic acid and grow, the vesicles extend into thread-like structures, eventually breaking off to form new vesicles containing their own nucleic acid.
Credit: Katarzyna Adamala, PhD 

Lower sequence: RNA templates bound to short RNA primers within vesicles made of fatty acid membranes. Triangular complexes of Mg2+ ion, required for RNA replication, chelated with citrate to protect the membrane from damage, pass into the cell and catalyze extension of the RNA primer (red). 

Szostak's team has been working for more than a decade to understand how the first cells developed from a "primordial soup" of chemicals into living organisms capable of copying their genetic material and reproducing. Part of that work is developing a model protocell made from components probably present in the primitive Earth environment. They have made significant progress towards developing cell membranes from the kind of fatty acids that would have been abundant and naturally form themselves into bubble-like vesicles when concentrated in water. But the genetic component – an RNA or DNA molecule capable of replication – has been missing.

Since the primitive environment in which such cells could have developed would not have had the kind of complex enzymes that modern cells use in replicating nucleic acids, Szostak and lead author Katarzyna Adamala, PhD, then a graduate student in Szostak's lab, investigated whether simple chemical processes could drive nonenzymatic replication of RNA, which many scientists believe was the first nucleic acid to develop.

To address the incompatibility between the need for Mg2+ to drive assembly of the RNA molecule and the ion's ability to degrade fatty acid membranes, they tested several chelators – small molecules that bind tightly to metal ions – for their ability to protect fatty acid vesicles from the potentially destabilizing effects of Mg2+. Citrate and several other chelators were found to be effective in protecting the membranes of fatty acid vesicles from disruption.

To test whether the presence of the tested chelators would allow Mg2+-catalyzed RNA assembly, the investigators placed molecules consisting of short primer RNA strands bound to longer RNA templates into fatty acid vesicles. The unbound, single-strand portion of the template consisted of a sequence of cytosine (C) nucleotides. In the presence of Mg2+ and one of four chelating molecules, one of which was citrate, the researchers then added activated G, the nucleotide that base-pairs with C in nucleic acids.

The desired reaction – diffusion of G nucleotides through the vesicle membrane to complete a double-stranded RNA molecule by binding to the C nucleotides of the template – proceeded fastest in the presence of citrate. In fact two of the other tested chelators completely prevented extension of the RNA primer.

"While other molecules can protect membranes against the magnesium ion," Szostak explains, "they don't let RNA chemistry go on. We think that citrate is able both to protect membranes and to allow RNA copying to proceed by covering only one face to the magnesium ion, protecting the membrane while allowing RNA chemistry to work." He and Adamala also found that continually refreshing the activated guanine nucleotide solution by flushing out broken down molecules and adding fresh nucleotides improved the efficiency of RNA replication.

Szostak notes that, while citrate may be appropriate for creating artificial cells in a laboratory environment, which he and his team are pursuing, it probably would not have been present in sufficient quantities in the early earth. "We have shown there is at least one way to make RNA replication chemistry compatible with primitive, fatty-acid-based cell membranes, but this opens up new questions. Our current best guess is there must have been some sort of simple peptides that acted in a similar way to citrate, and finding such peptides is something we are working on now."

A co-recipient of the 2009 Nobel Prize in Physiology or Medicine for his contribution to the discovery of the enzyme telomerase, Szostak is a professor of Genetics at Harvard Medical School and a Howard Hughes Medical Institute investigator. Adamala, who worked in Szostak's lab as part of her doctoral studies at Roma Tre University in Italy, is now a postdoctoral fellow at Massachusetts Institute of Technology. The study was supported, in part, by NASA Exobiology grant NNX07AJ09G.


Contacts and sources:
Sue McGreevey
Massachusetts General Hospital

Friday, November 29, 2013

Comet ISON May Have Survived

ISON appears as a white smear heading up and away from the sun. ISON was not visible during its closest approach to the sun, so many scientists thought it had disintegrated, but images like this one from the ESA/NASA Solar and Heliospheric Observatory suggest that a small nucleus may be intact.

Image Credit: ESA/NASA/SOHO/GSF

Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun.

Another view from SOHO's C2 chronograph shows Comet ISON appearing bright as it streams toward the sun (right). it can be seen as a dim streak heading upward and out in the left image. The comet may still be intact.
Image Credit: ESA/NASA/SOHO/Jhelioviewer 

Throughout the year that researchers have watched Comet ISON – and especially during its final approach to the sun – the comet brightened and dimmed in unexpected ways. Such brightness changes usually occur in response to material boiling off the comet, and different material will do so at different temperatures thus providing clues as to what the comet is made of. Analyzing this pattern will help scientists understand the composition of ISON, which contains material assembled during the very formation of the solar system some 4.5 billion years ago.

Contacts and sources:
Karen C. Fox
NASA's Goddard Space Flight Center


Related Links:
For more information on Comet ISON: www.nasa.gov/ison
To download recent ISON imagery: http://svs.gsfc.nasa.gov/Gallery/CometISON.html

NASA Rocket To Peek At Atmosphere Of Venus

The Venus Spectral Rocket Experiment (VeSpR, PI John Clarke, Boston U.) launched successfully  from White Sand Missile Range. VeSpR will study the present day escape of water from the atmosphere of Venus and relate it to the past abundance of water on Venus by measuring hydrogen (H) and the heavier, slower to escape, deuterated hydrogen (D) above 90 km on Venus.

The use of a pre-dispersing prism to prevent long wavelengths from entering the spectrograph permits a long-aperture approach to echelle spectroscopy, and the chosen combination of imaging and dispersion scales provides high spectral resolution of emission line profiles with a several arc sec wide aperture for good sensitivity. 

For comparable spectral resolution the HST/STIS uses a 0.2 arc sec aperture, which provides 375 times less solid angle on the sky than a 3 x 5 arc sec region observed by the sounding rocket telescope. Good data was obtained by both detectors with no obvious significant anomalies. Preliminary reports indicate a successful mission.

 A week after launching a new orbiter to investigate the upper atmosphere of Mars, NASA is sending a sounding rocket to probe the atmosphere of Venus.

The Mars Atmosphere and Volatile Evolution, or MAVEN, mission launched from Cape Canaveral Air Force Station in Florida on Nov. 18. Now, the Venus Spectral Rocket, VeSpR for short, is scheduled to lift off from White Sands, N.M., on Nov. 25.

"It is appropriate that these launch dates are close together, because both missions will study atmospheric loss," said Kelly Fast, the program scientist for MAVEN and the program officer for Planetary Astronomy at NASA Headquarters in Washington. "VeSpR will peek at Venus from above Earth's absorbing atmosphere, and MAVEN will journey to Mars to do a long-term study."

NASA launched a sounding rocket to study ultraviolet light being emitted from the atmosphere of Venus, shown here in false color to highlight subtle contrasts in cloud markings.
Image Credit: NASA JPL

VeSpR is a two-stage system, combining a Terrier missile – originally built as a surface-to-air missile and later repurposed to support science missions – and a Black Brant model Mk1 sounding rocket with a telescope inside. Integration took place at NASA’s Wallops Flight Facility in Virginia.

The experiments will look at ultraviolet (UV) light that is being emitted from Venus' atmosphere, which can provide information about the history of the planet's water. Measurements like these cannot be done using Earth-based telescopes because our atmosphere absorbs most UV light before it reaches the ground.

The solution is to make UV measurements from beyond Earth's atmosphere. In this case, the sounding rocket will carry the telescope more than 65 miles (110 kilometers) above the surface of Earth; at that altitude, the atmosphere thins out enough to permit UV readings.

"Venus today has a thick atmosphere that contains very little water, but we think the planet started out with an ocean's worth of water," said John T. Clarke of Boston University, the mission's principal investigator.

Scientists are still trying to determine whether water existed on the surface of Venus or only high up the atmosphere, where temperatures were cooler. If the surface temperature stayed below the boiling point of water long enough, rivers might have once flowed on the planet. Venus may have even had ice.

The key to figuring out how much water Venus once had lies in how much hydrogen and deuterium, a heavier version of hydrogen, remain in the atmosphere. Both can combine with oxygen to make water, either in the familiar H2O form or the rarer hydrogen, deuterium and oxygen form, called HDO. (Very small amounts of D2O also form.)

Intense UV light from the sun has broken apart nearly all of the water molecules in Venus' atmosphere. Because the regular hydrogen atoms in the water are lighter, they escape into space more quickly than the heavier deuterium ones. By comparing the amount of deuterium now in the atmosphereto the amount of hydrogen, researchers can estimate how much water disappeared from Venus and how quickly it happened.

Earlier estimates, made from data collected by NASA's 1978 Pioneer Venus spacecraft and other observations, indicated Venus could have had enough ancient water to cover the whole globe with 23 feet (7 meters) of liquid. But it turns out that the amounts of hydrogen and deuterium can vary at different heights in Venus' atmosphere, which could change the calculations. To help resolve the uncertainty, VeSpR will make measurements specifically in the upper atmosphere.

The VeSpR instrument will observe Venus for 8 minutes, with data being transmitted in real time, before the payload returns on a parachute safely to Earth. Later, the payload will be retrieved so that the instrument can be used for future experiments.

Clarke and his team will combine these measurements with observations of Venus they made recently with NASA's Hubble Space Telescope. The group is also collaborating with Jean-Loup Bertaux of France's Centre National de la Recherche Scientifique to study the planet using the UV instrument on the European Space Agency's Venus Express spacecraft.

VeSpR was built with funding from NASA's Planetary Astronomy program. The NASA sounding rocket program is managed for the agency at NASA’s Wallops Flight Facility. MAVEN's principal investigator is based at the University of Colorado Laboratory for Atmospheric and Space Physics in Boulder. NASA's Goddard Space Flight Center in Greenbelt, Md., manages MAVEN. Lockheed Martin built the MAVEN spacecraft and is responsible for mission operations.


Contacts and sources:
Elizabeth Zubritsky
NASA's Goddard Space Flight Center

Comet ISON Fizzles As It Rounds The Sun

As ISON appeared to dim and fizzle in several observatories and later could not be seen at all by NASA's Solar Dynamics Observatory or by ground based solar observatories, many scientists believed it had disintegrated completely. However, a streak of bright material streaming away from the sun appeared in the European Space Agency and NASA's Solar and Heliospheric Observatory later in the evening. The question remains whether it is merely debris from the comet, or if some portion of the comet's nucleus survived, but late-night analysis from scientists with NASA's Comet ISON Observing Campaign suggest that there is at least a small nucleus intact.

Comet ISON went around the sun on Nov. 28, 2013. Several solar observatories watched the comet throughout this closest approach to the sun, known as perihelion. While the fate of the comet is not yet established, it is likely that it did not survive the trip. The comet grew faint while within both the view of NASA's Solar Terrestrial Relations Observatory, and the joint European Space Agency and NASA's Solar and Heliospheric Observatory. The comet was not visible at all in NASA's Solar Dynamics Observatory.

These images from NASA's Solar Terrestrial Relations Observatory and the ESA/NASA Solar and Heliospheric Observatory show Comet ISON growing dim as it made the journey around the sun. The comet is believed to have broken up and evaporated.

Image Credit: NASA/SDO/ESA/SOHO/GSFC

"We didn't see Comet ISON in SDO," said Dean Pesnell, project scientist for SDO.

"So we think it must have broken up and evaporated before it reached perihelion."

This image from NASA's Solar Dynamics Observatory shows the sun, but no Comet ISON was seen. A white plus sign shows where the Comet should have appeared. It is likely that the comet did not survive the trip.

Image Credit: NASA/SDO

While this means that Comet ISON will not be visible in the night sky in December, the wealth of observations gathered of the comet over the last year will provide great research opportunities for some time. One important question will simply be to figure out why it is no longer visible.

Comet ISON at 9:30 a.m. EST on Nov. 28, 2013

Comet ISON moves ever closer to the sun in this image from ESA and NASA's Solar and Heliospheric Observatory, or SOHO, captured at 9:30 a.m. EST on Nov. 28, 2013. This image is a composite with the sun imaged by NASA's Solar Dynamics Observatory, or SDO, in the center, and SOHO showing the solar atmosphere, the corona. 
Credit: ESA&NASA/SOHO/SDO

Comet ISON at 10:51 a.m. EST on Nov. 28, 2013

Comet ISON has moved quite close to the sun in this image from ESA/NASA's Solar and Heliospheric Observatory captured at 10:51 a.m. EST on Nov. 28, 2013. This image is a composite, with the sun imaged by NASA's Solar Dynamics Observatory in the center, and SOHO showing the solar atmosphere, the corona. 

Credit: ESA&NASA/SOHO/SDO


Contacts and sources:
Karen C. Fox
NASA's Goddard Space Flight Center

Thursday, November 28, 2013

Glaciers Sizzle As They Disappear Into Warmer Watermore Stories:

The sounds of bubbles escaping from melting ice make underwater glacial fjords one of the loudest natural marine environments on earth

Scientists have recorded and identified one of the most prominent sounds of a warming planet: the sizzle of glacier ice as it melts into the sea. The noise, caused by trapped air bubbles squirting out of the disappearing ice, could provide clues to the rate of glacier melt and help researchers better monitor the fast-changing polar environments.


Credit: Wikipedia

Geophysicist Erin Pettit, a researcher at the University of Alaska, had often heard popping, crackling sounds while out kayaking in the frigid northern waters. The sounds were also picked up by underwater microphones Pettit set up off the Alaskan coast, and at a much louder volume than above the surface.

"If you were underneath the water in a complete downpour, with the rain pounding the water, that's one of the loudest natural ocean sounds out there," she said. "In glacial fjords we record that level of sound almost continually."

While Pettit suspected the din was caused by melting ice, she couldn't confirm that hypothesis without a more controlled experiment. So she enlisted the help of Kevin Lee and Preston Wilson, acoustics experts from the University of Texas. Pettit sent the Texas researchers chunks of glacier, which they mounted in a tank of chilled water. Lee and Wilson recorded video and audio of the ice as it melted and were able to match sounds on the recording to the escape of bubbles from the ice.

"Most of the sound comes from the bubbles oscillating when they're ejected," Lee said. "A bubble when it is released from a nozzle or any orifice will naturally oscillate at a frequency that's inversely proportional to the radius of the bubble," he said, meaning the smaller the bubble, the higher the pitch. The researchers recorded sounds in the 1 – 3 kilohertz range, which is right in the middle of the frequencies humans hear.

Scientists have known for decades that the bubbles in glaciers form when snow crystals trap pockets of air and then get slowly squashed down under the weight of more snow. As the snow is compacted it turns into ice and the air bubbles become pressurized. The regular way the bubbles form means that they are evenly distributed throughout the ice, an important characteristic if you want to use the sound intensity of bubble squirts to measure ice melt rate.

While the symphony of melting ice might not carry the same emotional wallop as images, sound still has its own, sometimes very loud, story to tell. Pettit and Lee say they could imagine using hydrophone recordings in glacial fjords to monitor relative changes in glacier melting in response to one-time weather events, seasonal changes, and long-term climate trends. Because sound travels long distances underwater, recording microphones can be placed a safe distance from unstable ice sheets. The audio recordings would complement other measurements of ice melt, such as time-lapse photography and salinity readings.

Presentation 4aUW4, "Underwater sound radiated by bubbles released by melting glacier ice," will take place on Thursday, Dec. 5, 2013, at 9:55 a.m. The abstract describing this work can be found here:http://asa2013.abstractcentral.com/planner.jsp.

New View Into The Hot And Energetic Universe

At its meeting in Paris today, the Science Programme Committee of the European Space Agency (ESA) selected the “The Hot and Energetic Universe” as the theme for its next Large (L-class) mission, which is expected to be launched in 2028. The theme was proposed by an international collaboration led by Kirpal Nandra, Director at the Max Planck Institute for Extraterrestrial Physics (MPE). 

The proposed Athena X-ray observatory will provide critical answers to the questions: How did ordinary matter assemble into the large scale structures we see today? How do black holes grow and shape the Universe? 
Credit: (c) Athena collaboration

Having made a compelling case for this exciting topic, the same team is now poised to propose a new mission concept to address some of the most pressing questions in modern astrophysics. The Advanced Telescope for High-energy Astrophysics (Athena) would provide the necessary angular and spectral resolution, throughput, detection sensitivity, and survey grasp to revolutionize our understanding of why the Universe looks the way it does.

How did ordinary matter assemble into the large scale structures that we see today? How did black holes grow and shape the Universe? These are some of the most important unanswered questions in modern astrophysics, and the next large ESA mission could provide critical answers.

“We are very pleased that ESA has decided that the ‘Hot and Energetic Universe’ will be one of its main mission targets”, says Nandra, spokesperson for the science theme and chair of the Athena collaboration, who prepared this science theme in a White Paper. “We have a superb team of astrophysicists who made a compelling case for this exciting topic. But our job is not over - now we need to keep working to define the X-ray telescope that will provide us with the answers.”

Hot gas is actually the dominant form of ordinary matter in the Universe, and is responsible for the largest coherent structures that we know today: clusters of galaxies. With temperatures of more than ten million degrees, the gas emits copiously at X-ray wavelengths. The key to understanding the formation and evolution of these structures is to build an X-ray space observatory that combines high sensitivity, i.e. large throughput and good angular resolution, high spectral resolution and a wide field of view. 

Athena was designed with exactly this goal in mind. With such a telescope, astronomers could obtain spectroscopic observations of distant galaxies and map the physical parameters of the largest bound objects – information that would dramatically advance our understanding of how hot gas structures started to assemble and form when the Universe was in its infancy. Mapping the velocities, thermodynamics and chemical composition of the hot gas and tracking it through cosmic time would also allow the scientists to understand the complex astrophysical processes such as non-gravitational heating and turbulence which are crucial to understanding the development of ordinary matter structures.

With an X-ray telescope like Athena, the astronomers could also look even further back into the history of the Universe to study its most energetic events and discover the first supermassive black holes, out to a time when the first galaxies were forming, less than one billion years after the Big Bang. Because of the extremely high temperatures and the huge energies deposited by matter as it falls into a black hole, X-ray emission is the most reliable and complete way of revealing such accreting monsters. 

Remarkably, processes originating close to the black hole seem able to influence galaxies and galaxy clusters on scales up to a billion times larger– this “cosmic feedback” is therefore an essential ingredient of galaxy evolution models, but it is not yet well understood.

Tracking the growth of supermassive black holes through cosmic time, in the earliest epoch of galaxy formation (at z=6-10) is impossible with current instrumentation. “We now have the X-ray optics technologies to provide the required leap in collecting area and angular resolution for wide field X-ray imaging,” says Nandra. “Over the past years at MPE we have been continuously developing our X-ray detectors for exactly this opportunity. Now there is the chance to use them to map the X-ray Universe with exquisite sensitivity over unparalleled sky areas. The earliest supermassive black holes are within our grasp.”

Now that the science theme has been accepted by ESA, the next step will be a call for an X-ray observatory able to achieve the science goals. As the proposers of the theme and with the required technologies in hand, the Athena team are confident their mission will make the grade. Once a mission concept has been selected there is expected to be a period of 3-4 years to consolidate the technology development. It will take another 10 years or so to build the observatory. In 2028, Athena should start to reveal the Hot and Energetic Universe in unprecedented detail, and to provide the answer to that most basic question – why does the Universe look like it does today?

In addition to “the Hot and Energetic Universe”, ESA accepted “the Gravitational Universe” as the theme for its following L-class mission. The proposed evolved Laser Interferometer Space Antenna (eLISA), a space-based gravitational-wave observatory, is likely to be the mission proposed to address this theme.


Contacts and sources:
Dr. Kirpal Nandra
Max-Planck-Institut Für Extraterrestrische Physik (MPE)

Wari, Inca Predecessors, Used Restraint To Reshape Human Landscape

Dartmouth study sheds new light on how pre-Inca states became empires in early America 
The Wari, a complex civilization that preceded the Inca empire in pre-Columbia America, didn't rule solely by pillage, plunder and iron-fisted bureaucracy, a Dartmouth study finds. Instead, they started out by creating loosely administered colonies to expand trade, provide land for settlers and tap natural resources across much of the central Andes. 

This is the Cusco region, with areas of full-coverage archeological surveys reported in this paper.

Credit: Alan Covey  

The results, which appeared in the Journal of Anthropological Archaeology in October 2013, shed new light on how early states evolved into empires in the region that became the Inca imperial heartland. 

The study is the first large-scale look at the settlement patterns and power of the Wari civilization, which flourished from about AD 600-1000 in the Andean highlands, well before the Inca empire's 15th century rise. Relatively little is known about the Wari -- there are no historical documents and archaeologists are still debating their power and statecraft. 
  
This is an aerial view of Pikillacta, facing toward the Cusco Basin.
Credit: Department of Library Services, American Museum of Natural History

Many scholars think the Wari established strong centralized control -- economic, political, cultural and military – like their Inca successors to govern the majority of the far-flung populations living across the central Andes. But the Dartmouth study suggests that while the Wari had significant administrative power, they did not successfully transition most colonies into directly ruled provinces.

"The identification of limited Wari state power encourages a focus on colonization practices rather than an interpretation of strong provincial rule," says Professor Alan Covey, the study's lead author. "A 'colonization first' interpretation of early Wari expansion encourages the reconsideration of motivations for expansion, shifting from military conquest and economic exploitation of subject populations to issues such as demographic relief and strategic expansion of trade routes or natural resource access."
  
This is the distribution of Wari pottery identified through survey, with three-hour walking intervals from Pikillacta and Tankarpata.

Credit: Department of Library Services, American Museum of Natural History

The results are based on a systematic inventory of archaeological surveys covering nearly 1,000 square miles and GIS analysis of more than 3,000 archaeological sites in and around Peru's Cusco Valley. The data indicate Wari power did not emanate continuously outward from Pikillacta, a key administrative center whose construction required a huge investment. Instead, the locations of Wari ceramics indicate a more uneven, indirect and limited influence even at the height of their power than traditional interpretations from excavations at Wari sites. 

Credit: Wikimedia Pottery

The study was supported by the Fulbright-Hays Doctoral Dissertation Research Abroad Fellowship Program, Skaggs Foundation, Organization of American States, National Science Foundation, Nation


Contacts and sources:
John Cramer
Dartmouth College

Wednesday, November 27, 2013

How Stars Move At The Center Of The Galaxy: Figures Of 8 And Peanut Shells

Two months ago astronomers created a new 3D map of stars at the centre of our Galaxy (the Milky Way), showing more clearly than ever the bulge at its core. Previous explanations suggested that the stars that form the bulge are in banana-like orbits, but a paper published this week in Monthly Notices of the Royal Astronomical Society suggests that the stars probably move in peanut-shell or figure of eight-shaped orbits instead.

An artist’s impression showing how the Milky Way galaxy would look seen from almost edge on and from a very different perspective than we get from the Earth. The central bulge shows up as a peanut shaped glowing ball of stars and the spiral arms and their associated dust clouds form a narrow band. 

Credit: ESO/NASA/JPL-Caltech/M. Kornmesser/R. Hurt'

The difference is important; astronomers develop theories of star motions to not only understand how the stars in our galaxy are moving today but also how our galaxy formed and evolves. The Milky Way is shaped like a spiral, with a region of stars at the centre known as the "bar," because of its shape. In the middle of this region, there is a "bulge" that expands out vertically.

In the new paper Alice Quillen, professor of astronomy at the University of Rochester, and her collaborators created a mathematical model of what might be happening at the centre of the Milky Way. Unlike the Solar System where most of the gravitational pull comes from the Sun and is simple to model, it is much harder to describe the gravitational field near the centre of the Galaxy, where millions of stars, vast clouds of dust, and even dark matter swirl about. In this case, Quillen and her colleagues considered the forces acting on the stars in or near the bulge.

As the stars go round in their orbits, they also move above or below the plane of the bar. When stars cross the plane they get a little push, like a child on a swing. At the resonance point, which is a point a certain distance from the center of the bar, the timing of the pushes on the stars is such that this effect is strong enough to make the stars at this point move up higher above the plane. It is like when the child on the swing has been pushed a little everytime he comes round and eventually he is swinging higher. These stars that are pushed out form the edge of the bulge.

The resonance at this point means that stars undergo two vertical oscillations for every orbital period. But what is the most likely shape of the orbits in between? The researchers showed through computer simulations that peanut-shell shaped orbits are consistent with the effect of this resonance and could give rise to the observed shape of the bulge, which is also like a peanut-shell.

Next month the European Space Agency will launch the Gaia spacecraft, which is designed to create a 3D map of the stars in the Milky Way and their motions. This 3D map will help astronomers better understand the composition, formation and evolution of our Galaxy.

"It is hard to look back into the past of our galaxy and know what was there, but simulations can give us clues," explained Quillen. "Using my model I saw that, over time, the resonance with the bar, which is what leads to these peculiarly shaped orbits, moves outwards. This may be what happened in our galaxy."

"Gaia will generate huge amounts of data – on billions of stars," said Quillen. This data will allow Quillen and her colleagues to finesse their model further. "This can lead to a better understanding of how the Milky Way might have evolved into the shape it has today."

Quillen explained that there are different models as to how the galactic bulge was formed. Astronomers are interested in finding out how much the bar has slowed down over time and whether the bulge "puffed up all at once or slowly." Understanding the distributions of speeds and directions of motion (velocities) of the stars in the bar and the bulge might help determine this evolution.

"One of the predictions of my model is that there is a sharp difference in the velocity distributions inside and outside the resonance," Quillen said. "Inside – closer to the galactic centre – the disk should be puffed up and the stars there would have higher vertical velocities. Gaia will measure the motions of the stars and allow us to look for variations in velocity distributions such as these."

Two movies of N-body simulations, one showing a bar that buckles (top), the other without buckling. These movies show face-on and edge-on views of barred galaxies. Both movies show that the peanut shape becomes more extended as the bar slows down.


 Movie


 Movie

To be able to generate a model for the orbits of stars in the bulge, Quillen needed to factor in different variables. She first needed to understand what happens at the region of the resonance, which depends on the speed of the rotating bar and the mass density of the bar.

"Before I could model the orbits, I needed the answer to what I thought was a simple question: what is the distribution of material in the inner galaxy?" Quillen said. "But this wasn't something I could just look up. Luckily my collaborator Sanjib Sharma was able to help out."

Sharma worked out how the speed of circular orbits changed with distance from the galactic centre (called the rotation curve). Using this information, Quillen could compute a mass density at the location of the resonance, which she needed for her model.

Quillen was also able to combine the new orbit models with the speed of the bar (which is rotating) to get a more refined estimate of the mass density 3000 light years from the Galaxy centre (about one eighth of the distance from the centre of the Galaxy to Earth), which is where the edge of the bulge is.

And there is not long now to wait now for Gaia to start collecting data. Gaia's launch time is set for December 19, and will be streamed live on the ESA Portal.

Quillen's co-authors in this paper are Sanjib Sharma, Sydney Institute for Astronomy, Australia; Ivan Minchev, Astronomy Institute of Potsdam, Germany; Yu-Jing Qin, Shanghai Astronomical Observatory, China; and Paola Di Matteo, Paris-Meudon Observatory, France.


Contacts and sources:
Leonor Sierra
University of Rochester

Fast, Furious, Refined: Smaller Black Holes Can Eat Plenty

Gemini observations support an unexpected discovery in the galaxy Messier 101. A relatively small black hole (20-30 times the mass of our Sun) can sustain a hugely voracious appetite while consuming material in an efficient and tidy manner – something previously thought impossible. The research also affects the long quest for elusive intermediate-mass black holes. The findings are published in the November 28, 2013, issue of the journal Nature.

Artist’s visualization of the environment around M101 ULX-1, showing a stellar-mass black hole (foreground) with accretion disk. Gas from the Wolf-Rayet star (background) feeds the black hole’s voracious appetite. 

Credit: Gemini Observatory/AURA artwork by Lynette Cook.

Observations of a black hole powering an energetic X-ray source in a galaxy some 22 million light-years away could change our thinking about how some black holes consume matter. The findings indicate that this particular black hole, thought to be the engine behind the X-ray source’s high-energy light output, is unexpectedly lightweight, and, despite the generous amount of dust and gas being fed to it by a massive stellar companion, it swallows this material in a surprisingly orderly fashion.

“It has elegant manners,” says research team member Stephen Justham, of the National Astronomical Observatories of China, Chinese Academy of Sciences. Such lightweights, he explains, must devour matter at close to their theoretical limits of consumption to sustain the kind of energy output observed. "We thought that when small black holes were pushed to these limits, they would not be able to maintain such refined ways of consuming matter," Justham explains. "We expected them to display more complicated behavior when eating so quickly. Apparently we were wrong."

A Surprising Twist

X-ray sources give off high- and low-energy X-rays, which astronomers call hard and soft X-rays, respectively. In what might seem like a contradiction, larger black holes tend to produce more soft X-rays, while smaller black holes tend to produce relatively more hard X-rays. This source, called M101 ULX-1, is dominated by soft X-rays, so researchers expected to find a larger black hole as its energy source.

ULX-1 is located near a spiral arm of M101. The image for M101 is composed from X-ray (Chandra X-ray Observatory; Purple), Infrared (Spitzer Satellite; Red), Optical (Hubble Space Telescope; Yellow) and Ultraviolet (GALEX satellite; Blue).

Credit: Chandra X-ray Observatory, Spitzer Satellite, Hubble Space Telescope, and GALEX Satellite.

In a surprising twist, however, the new observations made at the Gemini Observatory, and published in the November 28th issue of the journal Nature, indicate that M101 ULX-1’s black hole is on the small side, and astrophysicists don’t understand why.

In theoretical models of how matter falls into black holes and radiates energy, the soft X-rays come primarily from the accretion disk (see illustration), while hard X-rays are typically generated by a high-energy “corona” around the disk. The models show that the corona’s emission strength should increase as the rate of accretion gets closer to the theoretical limit of consumption. Interactions between the disk and corona are also expected to become more complex.

Based on the size of the black hole found in this work, the region around M101-ULX-1 should, theoretically, be dominated by hard X-rays and appear structurally more complicated. However, that isn’t the case.

“Theories have been suggested which allow such low-mass black holes to eat this quickly and shine this brightly in X-rays. But those mechanisms leave signatures in the emitted X-ray spectrum, which this system does not display,” says lead author Jifeng Liu, of the National Astronomical Observatories of China, Chinese Academy of Sciences. “Somehow this black hole, with a mass only 20-30 times the mass of our Sun, is able to eat at a rate near to its theoretical maximum while remaining relatively placid. It’s amazing. Theory now needs to somehow explain what’s going on.”

An Intermediate-mass Black Hole Dilemma

The discovery also delivers a blow to astronomers hoping to find conclusive evidence for an “intermediate-mass” black hole in M101 ULX-1. Such black holes would have masses roughly between 100 and 1000 times the mass of the Sun, placing them between normal stellar-mass black holes and the monstrous supermassive black holes that reside in the centers of galaxies. So far these objects have been frustratingly elusive, with potential candidates but no broadly-accepted detection. Ultra-luminous X-ray sources (ULXs) have been one of the main proposed hiding places for intermediate-mass black holes, and M101 ULX-1 was one of the most promising-looking contenders.

“Astronomers hoping to study these objects will now have to focus on other locations for which indirect evidence of this class of black holes has been suggested, either in the even brighter ‘hyper-luminous’ X-ray sources or inside some dense clusters of stars,” explains research team member Joel Bregman of the University of Michigan.

“Many scientists thought it was just a matter of time until we had evidence for an intermediate-mass black hole in M101 ULX-1,” says Liu. But the new Gemini findings both take away some of that hope to solve an old puzzle and adds the fresh mystery of how this stellar-mass black hole can consume matter so calmly.

To determine the mass of the black hole, the researchers used the Gemini Multi-Object Spectrograph at the Gemini North telescope on Mauna Kea, Hawai‘i to measure the motion of the companion. This star, which feeds matter to the black hole, is of the Wolf-Rayet variety. Such stars emit strong stellar winds, from which the black hole can then draw in material. This study also revealed that the black hole in M101 ULX-1 can capture more material from that stellar wind than astronomers had anticipated.

M101 ULX-1 is ultra-luminous, shining a million times more brightly than the Sun in both X-rays (from the black hole accretion disk) and in the ultraviolet (from the companion star). Co-author Paul Crowther from the University of Sheffield in the United Kingdom adds, "Although this isn't the first Wolf-Rayet black hole binary ever discovered, at some 22 million light-years away, it does set a new distance record for such a system. The Wolf-Rayet star will have died in a small fraction of the time it has taken for light to reach us, so this system is now likely a double black hole binary."

“Studying objects like M101 ULX-1 in distant galaxies gives us a vastly larger sampling of the diversity of objects in our universe,” says Bregman. “It’s absolutely amazing that we have the technology to observe a star orbiting a black hole in another galaxy this far away.”

The complete Nature paper can be accessed at: http://dx.doi.org/10.1038/nature12762


Contacts and sources:
Peter Michaud
Gemini Observatory

Has Comet ISON Broken Up?

As Comet ISON heads toward its closest approach to the sun — known as perihelion — on Nov. 28, 2013, scientists have been watching through many observatories to see if the comet has already broken up under the intense heat and gravitational forces of the sun.

Comet ISON moves ever closer to the sun in this movie from the ESA/NASA Solar and Heliospheric Observatory, captured in the early hours of Nov. 27, 2013. A coronal mass ejection explodes off the sun – it is unlikely to damage ISON even if they cross paths.

Image Credit: ESA/NASA/SOHO

 The comet is too far away to discern how many pieces it is in, so instead researchers carefully measure how bright it is, which can be used to infer its current state. Less light can sometimes mean that more of the material has boiled off and disappeared, perhaps pointing to a disintegrated comet. But also a disintegrating comet sometimes gives off more light, at least temporarily, so researchers look at the comet's pattern of behavior over the previous few days to work out what it may be doing.

Has Comet ISON broken up? It is still unclear.

At times observations have suggested ISON was getting dimmer and might already be in pieces. However, over Nov. 26-27, 2013, the comet once again brightened. In the early hours of Nov. 27, the comet appeared in the view of the European Space Agency/NASA mission the Solar and Heliospheric Observatory in the Large Angle and Spectrometric Coronagraph instrument.

NASA's STEREO-A spacecraft continues to observe Comet ISON as it approaches the sun. This movie from the spacecraft's Heliospheric Imager shows Comet ISON, Mercury, Comet Encke and Earth over a five day period from Nov. 20 to Nov. 25, 2013. The sun sits right of the field of view of this camera. This version is enhanced, resized and cropped for HD.
Credit: NASA/NRL/STEREO/CIOC/GSFC. 

Coronagraphs block out the bright light of the sun in order to better see the dimmer solar atmosphere, the corona. In these images, the comet looks quite bright as it moves in from the lower right of the image. A giant cloud of solar material, called a coronal mass ejection or CME, is also seen in the images bursting off the bottom of the sun and heading out into space. It is as yet unclear if the CME is heading towards ISON but even if it does, it poses no real danger to the comet.

If the comet has already broken up, it should disintegrate completely as it makes its slingshot around the sun. This would provide a great opportunity for scientists to see the insides of the comet, and better understand its composition — as such information holds clues about what material was present during the solar system's formation when this comet was born. However, it would likely mean no comet visible in the night sky in December. We'll only know for sure after the comet rounds the sun on Thanksgiving Day.

In the early hours of Nov. 27, 2013, Comet ISON entered the field of view of the European Space Agency/NASA Solar and Heliospheric Observatory. In this picture, called a coronagraph, the bright light of the sun itself is blocked so the structures around it are visible. The comet is seen in the lower right; a giant cloud of solar material, called a coronal mass ejection or CME, is seen billowing out under the sun.

Comet ISON streams toward the sun from the lower right in this image from the ESA/NASA Solar and Heliospheric Observatory mission, captured at 3:07 a.m. EST on Nov. 27, 2013. A cloud of solar material, called a coronal mass ejection, is seen under the sun.
Image Credit: ESA/NASA/SOHO

Comet ISON makes its appearance into the higher-resolution HI-1 camera on the STEREO-A spacecraft. The dark "clouds" coming from the right are density enhancements in the solar wind, causing all the ripples in comet Encke's tail. These kinds of solar wind interactions give us valuable information about solar wind conditions near the sun. Note: the STEREO-A spacecraft is currently located on the other side of the Sun, so it sees a totally different geometry to what we see from Earth.

Credit: Karl Battams/NASA/STEREO/CIOC

 
Contacts and sources:
Karen C. Fox
NASA's Goddard Space Flight Center 

Matter Waves Taught New Tricks: Magnets Made With Ultra Cold Atoms

Magnets have fascinated mankind for millenia. From the Greek philosophers to scientists of the modern era, which saw the rise of quantum mechanics, magnets have been pondered and investigated. Nowadays, they are not only intriguing oddities of nature, but also constitute crucial building blocks of modern technology: Ranging from data storage over medical instrumentation to transportation. And yet, to this day, they continue to puzzle scientists.

A novel experiment at the University of Hamburg utilizes matter waves to understand magnets. Magnets are built of elementary magnets which can point North (red) and South (blue), as can be seen in this computer simulation.
Credit: Center for Optical Quantum Technologies (ZOQ)

A novel approach to understand magnets was taken by a team of scientists lead by Klaus Sengstock and Ludwig Mathey from the Institute of Laser Physics at the University of Hamburg, with collaborators from Dresden, Innsbruck and Barcelona. In a joint experimental and theoretical effort, which was featured as the cover story of Nature Physics in November 2013, quantum matter waves made of Rubidium atoms were controlled in such a way that they mimic magnets. Under these well-defined conditions, these artificially created magnets can be studied with clarity, and can give a fresh perspective on long-standing riddles.

Quantum matter waves themselves are an intriguing state of atomic Rubidium clouds, based on a quantum mechanical effect predicted by Einstein and Bose as early as 1924 and observed for the first time in a ground-breaking experiment in 1995, which was later awarded with the Nobel prize.

Building on that experiment and developing it further, the team of scientists used infrared laser beams to force the atoms into a motion along triangular pathways, creating quantum matter waves that act as if they were magnets, like the ones you stick on your fridge. Speaking of cold, these atoms are about a trillion times colder than outer space.

"The experimental challenges are extraordinary", says lead experimental author Julian Struck. "For the atoms to move along the right trajectories, it is absolutely crucial that the laser beams are precisely stabilized. Otherwise, the motion of the atoms would be completely chaotic."

When a matter wave moves clockwise around a given triangle, as depicted in the illustration, the neighboring triangles are surrounded by counterclockwise motion. The resulting orientation at each triangle corresponds to a magnet pointing in North or South direction. These elementary magnets form domains and are in competition with each other, depicted in red and blue.

Lead theoretical author Robert Höppner explains: "We had to use a supercomputing facility such as the one at Juelich for our computer simulations of the experiment. Otherwise the complexity of the problem cannot be tackled. This allowed us to visualize the triangular magnets created by the condensate of atoms, and we learned about the subtle domain structure and how they respond in a magnetic field."

The results of this study have been published in the November issue of Nature Physics, where an illustration of the magnetic phases from the computer simulation is featured on the cover.


Contacts and sources:
Robert Höppner
University of Hamburg

Electromagnons: New Effect Couples Electricity And Magnetism In Materials

In magneto-electric materials, electric and magnetic vibrations can be coupled to “electromagnons”. High hopes are placed on this technology, a breakthrough could now be achieved at the Vienna University of Technology (TU Wien).

A sketch of the experiment: Polarized light is sent through the sample and then spectrometically analyzed.

Credit: TU Wien

Major industries such as modern microelectronics are based on the interaction between matter and electromagnetism. Electromagnetic signals can be processed and stored in specially tailored materials. In materials science, electric and magnetic effects have usually been studied separately. There are, however, extraordinary materials called “multiferroics”, in which electric and magnetic excitations are closely linked. Scientists at the Vienna University of Technology (TU Wien) have now shown in an experiment that magnetic properties and excitations can be influenced by an electric voltage. This opens up completely new possibilities for electronics at high frequencies.

The Best of Two Worlds
It has been well known for a long time that electricity and magnetism are two sides of the same coin. Waves in free space, such as visible light or mobile phone radiation, always consist of both an electric and a magnetic component. When it comes to material properties, however, electricity and magnetism have been viewed as separate topics. There are materials with magnetic ordering, which react to magnetic fields, and there are materials with electric ordering, which can be influenced by electric fields. 

Prof. Andrei Pimenov in his Lab
Credit: TU Wien

A magnet has a magnetic field, but no electric field. In a piezoelectric crystal, on the other hand, electric fields can be generated, but no magnetic fields. Having both at the same time seemed impossible. “Usually, both effects are created in very different ways”, says Professor Andrei Pimenov (TU Vienna). “Magnetic ordering comes from electrons aligning their magnetic moments, electric ordering comes from positive and negative charges moving with respect to one another.”

Electromagnons
In 2006, Andrei Pimenov (while working at Augsburg University) found evidence of excitations which are based on both electric and magnetic ordering. These excitations, which have been dubbed “electromagnons”, have been hotly debated by materials scientists ever since. Now Pimenov and his team have succeeded in switching such excitations on and off with an electric field in a special material made of dysprosium, manganese and oxygen (DyMnO3).

In this material, many electrons align their magnetic moments at low temperatures. Each electron has a magnetic direction which is slightly distorted with respect to the adjoining electron – therefore the electrons create spiral of magnetic moments. The spiral has two possible orientations – clockwise or counterclockwise – and, surprisingly, an external electric field can switch between these two possibilities.

Vibrating Atoms, Wobbling Moments
In magneto-electric materials, the charges and the magnetic moments of the atoms are connected. In dysprosium manganese oxide, this connection is particularly strong: “When the magnetic moments wobble, the electric charges move too”, says Andrei Pimenov. In this material, magnetic moments and electric charges simultaneously play a part in the excitation, and therefore both can be influenced by one single external field.

The effect can be demonstrated by sending terahertz radiation through the material: The polarization of the terahertz beam is changed if the multiferroic material exhibits magnetic ordering. If the magnetic spiral in the material can be switched with an electric field, this electric field eventually determines, whether the polarization of the terahertz beam is being rotated.

There are many ideas for future applications: Wherever it is desirable to combine the respective advantages of magnetic and electric effects, the new magneto-electric materials could be used in the future. This could lead to new kinds of amplifiers, transistors or data storage devices. Also, highly sensitive sensors could be built with electromagnon technology.


Contacts and sources:
Prof. Andrei Pimenov

The Deadliest Natural Hazard

Rip currents claim more lives in Australia on average each year than bushfires, floods, cyclones and sharks combined, UNSW research shows.

Rip currents are the cause of an average 21 confirmed human fatalities per year, compared with 5.9 for bushfires, 4.3 for floods, 7.5 for cyclones and 1 for sharks.

This is Dr. Rob Brander, an expert on rip currents at the University of New South Wales, Australia.
Credit: UNSW

"Rips account for greater overall loss of human life than other high profile natural hazards. Yet they do not get anywhere near as much attention and dedicated funding," says Dr Rob Brander, a coastal geomorphologist at UNSW, and lead author of the study.

The study is published in the journal Natural Hazards and Earth Science Systems.

Australia has about 11,000 mainland beaches with an estimated 17,500 rip currents operating at any given time. Rip currents are strong, narrow seaward-flowing currents that can easily carry unsuspecting swimmers significant distances offshore, leading to exhaustion, panic and often drowning.

An analysis of data from Australia's National Coronial Information System shows there was an average 21 confirmed deaths involving rips per year during the period 2004 to 2011.

"And this is likely to be an underestimate because there has to be a witness to an event who saw the person was caught in a rip, and then this information has to be included in the coronial report," says Dr Brander, a co-author on the study which was published earlier this year and led by researchers from Surf Life Saving Australia.

For the new study Dr Brander's team used information from the Australian Emergency Management Institute National Disaster Database to identify the average number of deaths per year caused by tropical cyclones, bushfires and floods since the mid-to-late 1800s.

In addition, the Australian Shark Attack File administered by Taronga Zoo in Sydney shows there has been an average of one death a year since 1962.

"Other types of hazards, like bushfires, have the capacity to claim large numbers of lives in a single event. On the other hand, rip currents are almost always present and rarely result in more than one death at a time. But in the end, more people die as a result of them," says Dr Brander.

"As rip current are a global problem, it is hoped that this study can be applied in other countries to more appropriately place the rip current hazard in perspective with and context of other natural hazard types."


Contacts and sources:
Deborah Smith
University of New South Wales

A Fiery Drama Of Star Birth And Death

Located only about 160 000 light-years from us  in the constellation of Dorado (The Swordfish), the Large Magellanic Cloud is one of our closest galactic neighbors. It is actively forming new stars in regions that are so bright that some can even be seen from Earth with the naked eye, such as the Tarantula Nebula. This new image, taken by ESO's Very Large Telescope at the Paranal Observatory in Chile, explores an area called NGC 2035 (right), sometimes nicknamed the Dragon's Head Nebula.

The Large Magellanic Cloud is one of the closest galaxies to our own. Astronomers have now used the power of the ESO's Very Large Telescope to explore NGC 2035, one of its lesser known regions, in great detail. This new image shows clouds of gas and dust where hot new stars are being born and are sculpting their surroundings into odd shapes. But the image also shows the effects of stellar death -- filaments created by a supernova explosion (left).
Credit: ESO

NGC 2035 is an HII region, or emission nebula, consisting of clouds of gas that glow due to the energetic radiation given off by young stars. This radiation strips electrons from atoms within the gas, which eventually recombine with other atoms and release light. Mixed in with the gas are dark clumps of dust that absorb rather than emit light, creating weaving lanes and dark shapes across the nebula.

This zoom sequence starts with a broad view of the whole sky. We gradually close in on the Large Magellanic Cloud, a small neighbouring galaxy to our Milky Way. The final close-up shows a VLT image of NGC 2035, a star formation region that has an adjacent remnant created by a supernova explosion.

Credit: ESO/Digitized Sky Survey 2/Nick Risinger/Robert Gendler. Music: John Dyson

The filamentary shapes to the left in the image are the not the results of starbirth, but rather stellar death. It was created by one of the most violent events that can happen in the Universe — a supernova explosion [1]. These explosions are so bright that they often briefly outshine their entire host galaxy, before fading from view over several weeks or months (also see eso1315 - http://www.eso.org/public/news/eso1315/ and potw1323a -http://www.eso.org/public/images/potw1323a/).

This wide-field view captures several star formations regions in the constellation of Dorado (The Swordfish). These glowing clouds of gas are located in the Large Magellanic Cloud, one of the Milky Way’s satellite galaxies. The bright region a little to the left of centre is NGC 2035. This view was created from images forming part of the Digitized Sky Survey 2.

Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

From looking at this image, it may be difficult to grasp the sheer size of these clouds — they are several hundred light-years across. And they are not in our galaxy, but far beyond. The Large Magellanic Cloud is enormous, but when compared to our own galaxy it is very modest in extent, spanning just 14 000 light-years — about ten times smaller than the Milky Way.

This image was acquired using the FOcal Reducer and low dispersion Spectrograph instrument attached to ESO's Very Large Telescope, which is located at the Paranal Observatory in Chile, as part of the ESO Cosmic Gems programme [2].

This chart shows the southern constellation of Dorado (The Swordfish, sometimes referred to as a Dolphinfish). Most of the stars that can be seen in a dark sky with the unaided eye are marked. The location of the star formation region NGC 2035 in the Large Magellanic Cloud is indicated with a red circle. The nebula itself appears as a faint fuzzy patch in amateur telescopes, although the bright stars associated with this region can be very easily seen.
Credit: ESO, IAU and Sky & Telescope 

[1] The remnant left over by the supernova explosion that can be seen in this image is called SNR 0536-67.6.

[2] The ESO Cosmic Gems programme is an initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO's science archive.


Contacts and sources:
Richard Hook
ESO

Tuesday, November 26, 2013

Implantable Synthetic Anti-Obesity Device

Humankind has a weight problem – and not only in the industrialized nations, either: the growing prosperity in many Asian or Latin American countries goes hand in hand with a way of life that quite literally has hefty consequences. According to the WHO, over half the population in many industrialized nations is overweight, one in three people extremely so. Not only is high-calorie and fatty food a lifetime on the hips, backside and stomach; it also leaves traces in the blood, where various fats ingested via food circulate. Increased blood-fat values are also regarded as a risk factor for heart attacks and strokes.

Genetic regulatory circuit monitors blood fat

The research group headed by ETH-Zurich professor Martin Fussenegger from the Department of Biosystems Science and Engineering in Basel has now de-veloped an early warning system and treatment: an implantable genetic circuit mainly composed of human gene components. On the one hand, it constantly monitors the circulating fat levels in the blood. On the other hand, it has a feed-back function and forms a messenger substance in response to excessively high blood-fat levels that conveys a sense of satiety to the body.


Implanted designer cells engineered with a synthetic anti-obesity gene network constantly score the blood fat level of the animals and coordinate excessive blood fat levels to appetite suppression thereby reducing food intake and body weight of diet-induced obese mice on an all-you-can-eat 60 percent fat diet. (Illustration shows diet-induced obese mice of the Jackson Laboratory.)
Credit: Graphics: M. Fussenegger / mice photo: Jackson Lab)

In order to construct this highly complex regulatory circuit, the biotechnologists skilfully combined different genes that produce particular proteins and reaction steps. They implanted the construct in human cells, which they then inserted into tiny capsules.

The researchers studied obese mice that had been fed fatty food. After the cap-sules with the gene regulatory circuit had been implanted in the animals and intervened due to the excessive levels, the obese mice stopped eating and their bodyweight dropped noticeably as a result. As the blood-fat levels also returned to normal, the regulatory circuit stopped producing the satiety signal.

"The mice lost weight although we kept giving them as much high-calorie food as they could eat," stresses Fussenegger. The animals ate less because the implant signalised a feeling of satiety to them. Mice that received normal animal feed with a five-per-cent fat content did not lose any weight or reduce their intake of food, says the biotechnologist.

Sensor for different dietary fats

One major advantage of the new synthetic regulatory circuit is the fact that it is not only able to measure one sort of fat, but rather several saturated and un-saturated animal and vegetable fats that are ingested with food at once. How-ever, this development cannot simply be transferred to humans. It will take many years to develop a suitable product. Nonetheless, Fussenegger can certainly envisage that one day obese people with a body mass index of way over thirty could have such a gene network implanted to help them lose weight. Fussenegger sees the development as a possible alternative to surgical inter-ventions such as liposuction or gastric bands. "The advantage of our implant would be that it can be used without such invasive interventions." Another merit: instead of intervening in the progression of a disease that is difficult to regulate, it has a preventive effect and exploits the natural human satiety mechanism.

This gene network is one of the most complex that Fussenegger and his team have constructed to date and was made possible thanks to the biotechnologist's years of experience in the field. It is not the first time he and his team have suc-ceeded in constructing such a complex feedback regulatory circuit: a number of years ago, they produced an implant that can also be used to combat gout via a feedback regulatory circuit.




Citation: Rössger K, Charpin-El-Hamri G, Fussenegger M. A closed-loop synthetic gene circuit for the treatment of diet-induced obesity in mice. Nature Communications, published online 26th November 2013. DOI: 10.1038/ncomms3825



 Contacts and sources:
Martin Fussenegger
ETH Zurich

Archaeological Discoveries Confirm Early Date Of Buddha's Life

Archaeologists working in Nepal have uncovered evidence of a structure at the birthplace of the Buddha dating to the sixth century B.C. This is the first archaeological material linking the life of the Buddha — and thus the first flowering of Buddhism — to a specific century.

Archaeologists Robin Coningham (left) and Kosh Prasad Acharya direct excavations within the Maya Devi Temple, uncovering a series of ancient temples contemporary with the Buddha. Thai monks meditate.

Credit: Ira Block/National Geographic
Pioneering excavations within the sacred Maya Devi Temple at Lumbini, Nepal, a UNESCO World Heritage site long identified as the birthplace of the Buddha, uncovered the remains of a previously unknown sixth-century B.C. timber structure under a series of brick temples. Laid out on the same design as those above it, the timber structure contains an open space in the center that links to the nativity story of the Buddha himself.

Until now, the earliest archaeological evidence of Buddhist structures at Lumbini dated no earlier than the third century B.C., the time of the patronage of the Emperor Asoka, who promoted the spread of Buddhism from present-day Afghanistan to Bangladesh.

"Very little is known about the life of the Buddha, except through textual sources and oral tradition," said archaeologist Professor Robin Coningham of Durham University, U.K., who co-led the investigation. Some scholars, he said, have maintained that the Buddha was born in the third century B.C. "We thought 'why not go back to archaeology to try to answer some of the questions about his birth?' Now, for the first time, we have an archaeological sequence at Lumbini that shows a building there as early as the sixth century B.C."

Early Buddhism revealed

The international team of archaeologists, led by Coningham and Kosh Prasad Acharya of the Pashupati Area Development Trust in Nepal, say the discovery contributes to a greater understanding of the early development of Buddhism as well as the spiritual importance of Lumbini. Their peer-reviewed findings are reported in the December 2013 issue of the international journal Antiquity. The research is partly supported by the National Geographic Society.

To determine the dates of the timber shrine and a previously unknown early brick structure above it, fragments of charcoal and grains of sand were tested using a combination of radiocarbon and optically stimulated luminescence techniques. Geoarchaeological research also confirmed the presence of ancient tree roots within the temple's central void.

"UNESCO is very proud to be associated with this important discovery at one of the most holy places for one of the world's oldest religions," said UNESCO Director-General Irina Bokova, who urged "more archaeological research, intensified conservation work and strengthened site management" to ensure Lumbini's protection.

"These discoveries are very important to better understand the birthplace of the Buddha," said Ram Kumar Shrestha, Nepal's minister of culture, tourism and civil aviation. "The government of Nepal will spare no effort to preserve this significant site."

Buddhist tradition records that Queen Maya Devi, the mother of the Buddha, gave birth to him while holding on to the branch of a tree within the Lumbini Garden, midway between the kingdoms of her husband and parents. Coningham and his colleagues postulate that the open space in the center of the most ancient, timber shrine may have accommodated a tree. Brick temples built later above the timber shrine also were arranged around the central space, which was unroofed.

Four main Buddhist sites

Lumbini is one of the key sites associated with the life of the Buddha; others are Bodh Gaya, where he became a Buddha or enlightened one; Sarnath, where he first preached; and Kusinagara, where he passed away. At his passing at the age of 80, the Buddha is recorded as having recommended that all Buddhists visit "Lumbini." The shrine was still popular in the middle of the first millennium A.D. and was recorded by Chinese pilgrims as having a shrine beside a tree.

The Maya Devi Temple at Lumbini remains a living shrine; the archaeologists worked alongside meditating monks, nuns and pilgrims.

In the scientific paper in Antiquity, the authors write: "The sequence (of archaeological remains) at Lumbini is a microcosm for the development of Buddhism from a localized cult to a global religion."

Lost and overgrown in the jungles of Nepal in the medieval period, ancient Lumbini was rediscovered in 1896 and identified as the birthplace of the Buddha on account of the presence of a third-century B.C. sandstone pillar. The pillar, which still stands, bears an inscription documenting a visit by Emperor Asoka to the site of the Buddha's birth as well as the site's name — Lumbini.

Despite the rediscovery of the key Buddhist sites, their earliest levels were buried deep or destroyed by later construction, leaving evidence of the very earliest stages of Buddhism inaccessible to archaeological investigation, until now.

Half a billion people around the world are Buddhists, and many hundreds of thousands make a pilgrimage to Lumbini each year. The archaeological investigation there was funded by the government of Japan in partnership with the government of Nepal, under a UNESCO project aimed at strengthening the conservation and management of Lumbini. Along with the National Geographic Society, the research also was supported by Durham University and Stirling University.

Coningham and Acharya were joined on the Antiquity paper by coauthors K.M. Strickland, C.E. Davis, M.J. Manuel, I. A. Simpson, K. Gilliland, J. Tremblay, T.C. Kinnaird and D.C.W. Sanderson.

 A documentary on Coningham's exploration of the Buddha's life, "Buried Secrets of the Buddha," will premiere in February internationally on National Geographic Channel.


Contacts and sources:
Barbara Moffet
National Geographic Society

Seahorse Heads Have A 'No Wake Zone' That's Made For Catching Prey

Seahorses are slow, docile creatures, but their heads are perfectly shaped to sneak up and quickly snatch prey, according to marine scientists from The University of Texas at Austin.

"A seahorse is one the slowest swimming fish that we know of, but it's able to capture prey that swim at incredible speeds for their size," said Brad Gemmell, research associate at the University of Texas Marine Science Institute, which is part of the College of Natural Sciences.

The prey, in this case, are copepods. Copepods are extremely small crustaceans that are a critical component of the marine food web. They are a favored meal of seahorses, pipefish and sea dragons, all of which are uniquely shaped fish in the syngnathid family.

Copepods escape predators when they detect waves produced in advance of an attack, and they can jolt away at speeds of more than 500 body lengths per second. That equates to a 6-foot person swimming under water at 2,000 mph.

"Seahorses have the capability to overcome the sensory abilities of one of the most talented escape artists in the aquatic world — copepods," said Gemmell. "People often don't think of seahorses as amazing predators, but they really are."

In calm conditions, seahorses are the best at capturing prey of any fish tested. They catch their intended prey 90 percent of the time. "That's extremely high," said Gemmell, "and we wanted to know why."

For their study, Gemmell and his colleague Ed Buskey, professor of marine science, turned to the dwarf seahorse, Hippocampus zosterae, which is native to the Bahamas and the U.S. To observe the seahorses and the copepods in action, they used high-speed digital 3-D holography techniques developed by mechanical engineer Jian Sheng at Texas Tech University. The technique uses a microscope outfitted with a laser and a high-speed digital camera to catch the rapid movements of microscopic animals moving in and out of focus in a 3-D volume of liquid.

 
The dwarf seahorse,Hippocampus zosterae, has a head perfectly shaped to sneak up on fast moving copepods.

Seahorses heads are perfectly shaped to sneak up and quickly snatch prey, according to marine scientists from The University of Texas at Austin. In this video, watch a seahorse sneak up on a copepod, which is one of the fastest escape artists around, and use its "pivot feeding" technique to suck the copepod into its mouth. The seahorse was caught in action using high-speed digital 3-D holography.

 
 Credit: University of Texas - Austin / Brad Gemmell

The holography technique revealed that the seahorse's head is shaped to minimize the disturbance of water in front of its mouth before it strikes. Just above and in front of the seahorse's nostrils is a kind of "no wake zone," and the seahorse angles its head precisely in relation to its prey so that no fluid disturbance reaches it.

Other small fish with blunter heads, such as the three-spine stickleback, have no such advantage.

Gemmell said that the unique head shape of seahorses and their kin likely evolved partly in response to pressures to catch their prey. Individuals that could get very close to prey without generating an escape response would be more successful in the long term.

"It's like an arms race between predator and prey, and the seahorse has developed a good method for getting close enough so that their striking distance is very short," he said.

Seahorses feed by a method known as pivot feeding. They rapidly rotate their heads upward and draw the prey in with suction. The suction only works at short distances; the effective strike range for seahorses is about 1 millimeter. And a strike happens in less than 1 millisecond. Copepods can respond to predator movements in 2 to 3 milliseconds — faster than almost anything known, but not fast enough to escape the strike of the seahorse.

Once a copepod is within range of a seahorse, which is effectively cloaked by its head shape, the copepod has no chance.

Gemmell said that being able to unravel these interactions between small fish and tiny copepods is important because of the role that copepods play in larger ecosystem food webs. They are a major source of energy and anchor of the marine food web, and what affects copepods eventually affects humans, which are sitting near the top of the web, eating the larger fish that also depend on copepods.

Gemmell, Buskey and Sheng published their research this week in Nature Communications.


Contacts and sources:
Brad Gemmell
University of Texas at Austin

Inexpensive ‘Nano-Camera’ Operates At The Speed Of Light

Nano-camera could be used in medical imaging, collision-avoidance detectors for cars, and interactive gaming.

A $500 nano-camera that can operate at the speed of light has been developed by researchers in the MIT Media Lab.

MIT students (left to right) Ayush Bhandari, Refael Whyte and Achuta Kadambi pose next to their "nano-camera" that can capture translucent objects, such as a glass vase, in 3-D. 
Credit; Photo by Bryce Vickmark  

The three-dimensional camera, which was presented last week at Siggraph Asia in Hong Kong, could be used in medical imaging and collision-avoidance detectors for cars, and to improve the accuracy of motion tracking and gesture-recognition devices used in interactive gaming.

The camera is based on “Time of Flight” technology like that used in Microsoft’s recently launched second-generation Kinect device, in which the location of objects is calculated by how long it takes a light signal to reflect off a surface and return to the sensor. However, unlike existing devices based on this technology, the new camera is not fooled by rain, fog, or even translucent objects, says co-author Achuta Kadambi, a graduate student at MIT.

“Using the current state of the art, such as the new Kinect, you cannot capture translucent objects in 3-D," Kadambi says. “That is because the light that bounces off the transparent object and the background smear into one pixel on the camera. Using our technique you can generate 3-D models of translucent or near-transparent objects.”

In a conventional Time of Flight camera, a light signal is fired at a scene, where it bounces off an object and returns to strike the pixel. Since the speed of light is known, it is then simple for the camera to calculate the distance the signal has travelled and therefore the depth of the object it has been reflected from.

Unfortunately though, changing environmental conditions, semitransparent surfaces, edges, or motion all create multiple reflections that mix with the original signal and return to the camera, making it difficult to determine which is the correct measurement.

Instead, the new device uses an encoding technique commonly used in the telecommunications industry to calculate the distance a signal has travelled, says Ramesh Raskar, an associate professor of media arts and sciences and leader of the Camera Culture group within the Media Lab, who developed the method alongside Kadambi, Refael Whyte, Ayush Bhandari, and Christopher Barsi at MIT and Adrian Dorrington and Lee Streeter from the University of Waikato in New Zealand.

“We use a new method that allows us to encode information in time,” Raskar says. “So when the data comes back, we can do calculations that are very common in the telecommunications world, to estimate different distances from the single signal.”

The idea is similar to existing techniques that clear blurring in photographs, says Bhandari, a graduate student in the Media Lab. “People with shaky hands tend to take blurry photographs with their cellphones because several shifted versions of the scene smear together,” Bhandari says. “By placing some assumptions on the model — for example that much of this blurring was caused by a jittery hand — the image can be unsmeared to produce a sharper picture.”

The new model, which the team has dubbed nanophotography, unsmears the individual optical paths.

In 2011 Raskar’s group unveiled a trillion-frame-per-second camera capable of capturing a single pulse of light as it travelled through a scene. The camera does this by probing the scene with a femtosecond impulse of light, then uses fast but expensive laboratory-grade optical equipment to take an image each time. However, this “femto-camera” costs around $500,000 to build.

In contrast, the new “nano-camera” probes the scene with a continuous-wave signal that oscillates at nanosecond periods. This allows the team to use inexpensive hardware — off-the-shelf light-emitting diodes (LEDs) can strobe at nanosecond periods, for example — meaning the camera can reach a time resolution within one order of magnitude of femtophotography while costing just $500.

“By solving the multipath problem, essentially just by changing the code, we are able to unmix the light paths and therefore visualize light moving across the scene,” Kadambi says. “So we are able to get similar results to the $500,000 camera, albeit of slightly lower quality, for just $500.”

Conventional cameras see an average of the light arriving at the sensor, much like the human eye, says James Davis, an associate professor of computer science at the University of California at Santa Cruz. In contrast, the researchers in Raskar’s laboratory are investigating what happens when they take a camera fast enough to see that some light makes it from the “flash” back to the camera sooner, and apply sophisticated computation to the resulting data, Davis says.

“Normally the computer scientists who could invent the processing on this data can’t build the devices, and the people who can build the devices cannot really do the computation,” he says. “This combination of skills and techniques is really unique in the work going on at MIT right now.”

What’s more, the basic technology needed for the team’s approach is very similar to that already being shipped in devices such as the new version of Kinect, Davis says. “So it’s going to go from expensive to cheap thanks to video games, and that should shorten the time before people start wondering what it can be used for,” he says. “And by the time that happens, the MIT group will have a whole toolbox of methods available for people to use to realize those dreams."




Contacts and sources:
Abby Abazorius
Massachusetts Institute of Technology