A team of astronomers using the National Science Foundation's Green Bank Telescope (GBT) in West Virginia and NASA's Deep Space Network radar transmitter at Goldstone, California, has made the most detailed radar images yet of asteroid 2004 BL86.
The images, which were taken early in the morning on Jan. 27, 2014, reveal the asteroid's surface features in unprecedented clarity. At the time of the observations, the asteroid was traveling away from the Earth, so its distance varied from 1.3 million to 1.6 million kilometers, or about three-and-a-half to four times the distance from the Earth to the Moon.
To make these images, a continuous radar signal was sent from the transmitter at Goldstone to the asteroid. The reflected signal was then received by the 100-meter diameter dish of the GBT in a process known as bistatic radar imaging.
The GBT images also confirmed the presence of a small moon-like companion zipping around the asteroid, which was previously detected with ground-based optical telescopes by Joe Pollock of Appalachian State University in Boone, North Carolina, and Petr Pravec of Ondrejov Observatory in the Czech Republic.
Radar Enables Better Resolution
Radar images are particularly valuable in studying asteroids because they enable very high-resolution imaging. At the distance of the GBT observations, ground-based optical telescopes would produce images with a resolution of about 100 meters per pixel, so the asteroid would appear as a smudgy blob. The resolution of radar images, however, depends on how the signal is coded and the strength of the return signal, not the size of a telescope lens or mirror. With the GBT's newly installed data acquisition equipment, the astronomers were able to create images with a resolution as fine as a few (3.75) meters, revealing distinct surface features.
"There are a lot of fascinating features in these images, including possible evidence for several ridges at different latitudes," said Lance Benner, a scientist with NASA's Jet Propulsion Laboratory in Pasadena, California, and a member of the observing team.
The images also clearly establish that 2004 BL86 is a rounded object with an apparent equatorial bulge, which was also seen in the earlier Goldstone observations. In the latest images, the orientation reveal more of the asteroid's equator, providing a clearer picture of that region. The collage of images also shows the rapid motion of the asteroid's moon relative to its companion.
Further analysis of the images could provide important insights into the formation and evolution of this object.
"Capturing an object this small, about half a kilometer across, at such a tremendous distance with this clarity is truly amazing," said Michael Busch, a research scientist at the SETI Institute in Mountain View, California, and a member of the observing team. "This level of detail is similar to fly-by observations obtained by spacecraft," he noted.
Radar Speckles Unlock Other Details
Concurrently with the radar imaging, the scientists also used the radar transmitter at the Arecibo Observatory in Puerto Rico and a portion of the antennas that are part of the National Radio Astronomy Observatory's (NRAO) Very Long Baseline Array (VLBA) to perform an observation known as radar speckle tracking. This technique uses the seemingly chaotic radar pattern reflected by the uneven surface of an asteroid as it sweeps across the surface of the Earth to determine how fast and in what direction it's tumbling. Once analyzed, these data will also reveal important details about its internal physical properties and future trajectory.
The asteroid 2004 BL86 is approximately 300 meters across and its moon is a mere 70 meters across. This size comparison is not evident in the radar images because of the way they were processed. Approximately one-sixth of asteroids in this size range (200 meters or larger) sport at least one companion.
Read more at Science Daily
Feb 1, 2015
Jan 31, 2015
Evidence mounts for quantum criticality theory
A new study by a team of physicists at Rice University, Zhejiang University, Los Alamos National Laboratory, Florida State University and the Max Planck Institute adds to the growing body of evidence supporting a theory that strange electronic behaviors -- including high-temperature superconductivity and heavy fermion physics -- arise from quantum fluctuations of strongly correlated electrons.
The study, which appeared in the Jan. 20 issue of Proceedings of the National Academy of Sciences, describes results from a series of experiments on a layered composite of cerium, rhodium and indium. The experiments tested, for the first time, a prediction from a theory about the origins of quantum criticality that was published by Rice physicist Qimiao Si and colleagues in 2001.
"Our theory was a surprise at the time because it broke with the textbook framework and suggested that a broad range of phenomena -- including high-temperature superconductivity -- can only be explained in terms of the collective behavior of strongly correlated electrons rather than by the more familiar theory based on essentially decoupled electrons," said Si, a co-corresponding author on the new study and Rice's Harry C. and Olga K. Wiess Professor of Physics and Astronomy.
Experimental evidence in support of the theory has mounted over the past decade, and the PNAS study fills yet another gap. In the experiments, researchers probed high-quality samples of a heavy-fermion material known as CeRhIn5.
Heavy fermion materials like CeRhIn5 are prototype systems for quantum criticality. In these materials, electrons tend to act in unison, and even one electron moving through the system causes widespread effects. This "correlated electron" behavior is very different from the electron interactions in a common metal like copper, and physicists have become increasingly convinced that correlated electron behavior plays an important role in phenomena like superconductivity and quantum criticality.
Quantum critical points, near which these strange correlated effects are particularly pronounced, mark a smooth phase change, or transition from one state of matter to another. Just as the melting of ice involves a transition from a solid to a liquid state, the electronic state of quantum materials changes when the material is cooled to a quantum critical point.
The critical temperature of a material can be raised or lowered if the material is chemically altered, placed under high pressure or put into a strong magnet. In the new experiments, which were carried out using the high magnetic field facilities at Los Alamos National Laboratory in New Mexico and at Florida State University, researchers observed a magnetically induced quantum critical point at ambient pressure and compared it to the previously studied case of a pressure-induced quantum critical point.
The nature of the quantum critical point was probed by something called the "Fermi surface," a sort of three-dimensional map that represents the collective energy states of all electrons in the material. When physicists have previously attempted to describe quantum phase transitions using traditional theories, equations dictate that the Fermi surface must change smoothly and gradually as the material passes through the critical point. In that case, most of the electrons on the Fermi surface are still weakly coupled to each other.
In contrast, Si's theory predicts that the Fermi surface undergoes a radical and instantaneous shift at the critical point. The electrons on the entire Fermi surface become strongly coupled, thereby giving rise to the strange-metal properties that allow unusual electronic states, including superconductivity.
A "Fermi surface" is kind of three-dimensional map representing the collective energy states of electrons in a material. These computer-generated illustrations show how the Fermi surface for CeRhIn5 changes, depending upon whether the electrons are strongly interacting (left) or weakly interacting (right). Credit: Q. Si/Rice University and J.X. Zhu/Los Alamos National Laboratory
"We observed exactly the sort of a sharp Fermi surface reconstruction predicted by theory of unconventional quantum criticality," said study co-author Frank Steglich, director of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, and also of the Center for Correlated Matter at Zhejiang University in Hangzhou, China.
Zhejiang physicist Huiqiu Yuan, co-corresponding author on the study, said, "Our experiments demonstrate that direct measurements of a Fermi surface can distinguish theoretically proposed models of quantum criticality and point to a universal description of quantum phase transitions."
Read more at Scince Daily
The study, which appeared in the Jan. 20 issue of Proceedings of the National Academy of Sciences, describes results from a series of experiments on a layered composite of cerium, rhodium and indium. The experiments tested, for the first time, a prediction from a theory about the origins of quantum criticality that was published by Rice physicist Qimiao Si and colleagues in 2001.
"Our theory was a surprise at the time because it broke with the textbook framework and suggested that a broad range of phenomena -- including high-temperature superconductivity -- can only be explained in terms of the collective behavior of strongly correlated electrons rather than by the more familiar theory based on essentially decoupled electrons," said Si, a co-corresponding author on the new study and Rice's Harry C. and Olga K. Wiess Professor of Physics and Astronomy.
Experimental evidence in support of the theory has mounted over the past decade, and the PNAS study fills yet another gap. In the experiments, researchers probed high-quality samples of a heavy-fermion material known as CeRhIn5.
Heavy fermion materials like CeRhIn5 are prototype systems for quantum criticality. In these materials, electrons tend to act in unison, and even one electron moving through the system causes widespread effects. This "correlated electron" behavior is very different from the electron interactions in a common metal like copper, and physicists have become increasingly convinced that correlated electron behavior plays an important role in phenomena like superconductivity and quantum criticality.
Quantum critical points, near which these strange correlated effects are particularly pronounced, mark a smooth phase change, or transition from one state of matter to another. Just as the melting of ice involves a transition from a solid to a liquid state, the electronic state of quantum materials changes when the material is cooled to a quantum critical point.
The critical temperature of a material can be raised or lowered if the material is chemically altered, placed under high pressure or put into a strong magnet. In the new experiments, which were carried out using the high magnetic field facilities at Los Alamos National Laboratory in New Mexico and at Florida State University, researchers observed a magnetically induced quantum critical point at ambient pressure and compared it to the previously studied case of a pressure-induced quantum critical point.
The nature of the quantum critical point was probed by something called the "Fermi surface," a sort of three-dimensional map that represents the collective energy states of all electrons in the material. When physicists have previously attempted to describe quantum phase transitions using traditional theories, equations dictate that the Fermi surface must change smoothly and gradually as the material passes through the critical point. In that case, most of the electrons on the Fermi surface are still weakly coupled to each other.
In contrast, Si's theory predicts that the Fermi surface undergoes a radical and instantaneous shift at the critical point. The electrons on the entire Fermi surface become strongly coupled, thereby giving rise to the strange-metal properties that allow unusual electronic states, including superconductivity.
A "Fermi surface" is kind of three-dimensional map representing the collective energy states of electrons in a material. These computer-generated illustrations show how the Fermi surface for CeRhIn5 changes, depending upon whether the electrons are strongly interacting (left) or weakly interacting (right). Credit: Q. Si/Rice University and J.X. Zhu/Los Alamos National Laboratory
"We observed exactly the sort of a sharp Fermi surface reconstruction predicted by theory of unconventional quantum criticality," said study co-author Frank Steglich, director of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany, and also of the Center for Correlated Matter at Zhejiang University in Hangzhou, China.
Zhejiang physicist Huiqiu Yuan, co-corresponding author on the study, said, "Our experiments demonstrate that direct measurements of a Fermi surface can distinguish theoretically proposed models of quantum criticality and point to a universal description of quantum phase transitions."
Read more at Scince Daily
Hydrogen production in extreme bacterium
A researcher at Missouri University of Science and Technology has discovered a bacterium that can produce hydrogen, an element that one day could lessen the world's dependence on oil.
Dr. Melanie Mormile, professor of biological sciences at Missouri S&T, and her team discovered the bacterium Halanaerobium hydrogeninformans in Soap Lake, Washington. It can "produce hydrogen under saline and alkaline conditions in amounts that rival genetically modified organisms," Mormile says.
"Usually, I tend to study the overall microbial ecology of extreme environments, but this particular bacterium has caught my attention," Mormile says. "I intend to study this isolate in greater detail."
Mormile, an expert in the microbial ecology of extreme environments, wasn't searching for a bacterium that could produce hydrogen. Instead, she first became interested in bacteria that could help clean up the environment, especially looking at the extremophiles found in Soap Lake. An extremophile is a microorganism that lives in conditions of extreme temperature, acidity, alkalinity or chemical concentration. Living in such a hostile environment, Halanaerobium hydrogeninformans has metabolic capabilities under conditions that occur at some contaminated waste sites.
With Halanaerobium hydrogeninformans, she expected to find an iron-reducing bacterium and describe a new species. What she found was a new species of bacterium that can produce hydrogen and 1, 3-propanediol under high pH and salinity conditions that might turn out to be valuable industrially. An organic compound, 1, 3-propenediol can be formulated into industrial products including composites, adhesives, laminates and coatings. It's also a solvent and can be used as antifreeze.
The infrastructure isn't in place now for hydrogen to replace gasoline as a fuel for planes, trains and automobiles. But if hydrogen becomes an alternative to gasoline, Halanaerobium hydrogeniformans, mass-produced on an industrial scale, might be one solution -- although it won't be a solution anytime soon.
"It would be great if we got liters and liters of production of hydrogen," Mormile says. "However, we have not been able to scale up yet."
In her first single-author article, Mormile's findings were featured in the Nov. 19 edition of Frontiers in Microbiology.
Read more at Science Daily
Dr. Melanie Mormile, professor of biological sciences at Missouri S&T, and her team discovered the bacterium Halanaerobium hydrogeninformans in Soap Lake, Washington. It can "produce hydrogen under saline and alkaline conditions in amounts that rival genetically modified organisms," Mormile says.
"Usually, I tend to study the overall microbial ecology of extreme environments, but this particular bacterium has caught my attention," Mormile says. "I intend to study this isolate in greater detail."
Mormile, an expert in the microbial ecology of extreme environments, wasn't searching for a bacterium that could produce hydrogen. Instead, she first became interested in bacteria that could help clean up the environment, especially looking at the extremophiles found in Soap Lake. An extremophile is a microorganism that lives in conditions of extreme temperature, acidity, alkalinity or chemical concentration. Living in such a hostile environment, Halanaerobium hydrogeninformans has metabolic capabilities under conditions that occur at some contaminated waste sites.
With Halanaerobium hydrogeninformans, she expected to find an iron-reducing bacterium and describe a new species. What she found was a new species of bacterium that can produce hydrogen and 1, 3-propanediol under high pH and salinity conditions that might turn out to be valuable industrially. An organic compound, 1, 3-propenediol can be formulated into industrial products including composites, adhesives, laminates and coatings. It's also a solvent and can be used as antifreeze.
The infrastructure isn't in place now for hydrogen to replace gasoline as a fuel for planes, trains and automobiles. But if hydrogen becomes an alternative to gasoline, Halanaerobium hydrogeniformans, mass-produced on an industrial scale, might be one solution -- although it won't be a solution anytime soon.
"It would be great if we got liters and liters of production of hydrogen," Mormile says. "However, we have not been able to scale up yet."
In her first single-author article, Mormile's findings were featured in the Nov. 19 edition of Frontiers in Microbiology.
Read more at Science Daily
Jan 30, 2015
50-Foot-Long 'Dragon' Dinosaur Unearthed in China
An enormous 50-foot-long dinosaur named "Dragon of Qijiang" was unearthed by construction workers near Qijiang City, China.
The plant-eating dinosaur, Qijianglong guokr, had an unusual body that was half neck. It lived about 160 million years ago and is described in the latest issue of the Journal of Vertebrate Paleontology.
The construction crew that happened upon the dinosaur remarkably managed to unearth the dinosaur with its head still attached to its long, narrow neck.
"It is rare to find a head and neck of a long-necked dinosaur together because the head is so small and easily detached after the animal dies," co-author Tetsuto Miyashita said in a press release.
"Qijianglong is a cool animal," added Miyashita, who is a University of Alberta paleontologist. "If you imagine a big animal that is half neck, you can see that evolution can do quite extraordinary things."
Most sauropods (i.e. long-necked, plant-eating dinosaurs) have necks that are about one-third the length of their bodies, so "Dragon of Qijiang" sported quite a neck. The researchers determined that its vertebrae were filled with air, making it lighter in weight than the neck bones of other animals.
Interlocking joints between the vertebrae, however, meant that the neck was surprisingly stiff. The researchers suspect that the neck was more mobile going up and down, like a construction crane, than it was moving from side to side.
"Dragon of Qijiang" is classified as a mamenchisaurid, a group of dinosaurs known for their long necks. This type of dinosaur has thus far only been found in Asia.
"Qijianglong shows that long-necked dinosaurs diversified in unique ways in Asia during Jurassic times–something very special was going on in that continent," said Miyashita. "Nowhere else we can find dinosaurs with longer necks than those in China. The new dinosaur tells us that these extreme species thrived in isolation from the rest of the world."
The paleontologists speculate that a sea, or other natural barrier, could have caused the isolation.
The "Dragon" and its kind were survivors, though. As other long-necked dinosaurs bit the dust in Asia, mamenchisaurids thrived, evolving into different types, including this half-neck form.
Read more at Discovery News
The plant-eating dinosaur, Qijianglong guokr, had an unusual body that was half neck. It lived about 160 million years ago and is described in the latest issue of the Journal of Vertebrate Paleontology.
The construction crew that happened upon the dinosaur remarkably managed to unearth the dinosaur with its head still attached to its long, narrow neck.
"It is rare to find a head and neck of a long-necked dinosaur together because the head is so small and easily detached after the animal dies," co-author Tetsuto Miyashita said in a press release.
"Qijianglong is a cool animal," added Miyashita, who is a University of Alberta paleontologist. "If you imagine a big animal that is half neck, you can see that evolution can do quite extraordinary things."
Most sauropods (i.e. long-necked, plant-eating dinosaurs) have necks that are about one-third the length of their bodies, so "Dragon of Qijiang" sported quite a neck. The researchers determined that its vertebrae were filled with air, making it lighter in weight than the neck bones of other animals.
Interlocking joints between the vertebrae, however, meant that the neck was surprisingly stiff. The researchers suspect that the neck was more mobile going up and down, like a construction crane, than it was moving from side to side.
"Dragon of Qijiang" is classified as a mamenchisaurid, a group of dinosaurs known for their long necks. This type of dinosaur has thus far only been found in Asia.
"Qijianglong shows that long-necked dinosaurs diversified in unique ways in Asia during Jurassic times–something very special was going on in that continent," said Miyashita. "Nowhere else we can find dinosaurs with longer necks than those in China. The new dinosaur tells us that these extreme species thrived in isolation from the rest of the world."
The paleontologists speculate that a sea, or other natural barrier, could have caused the isolation.
The "Dragon" and its kind were survivors, though. As other long-necked dinosaurs bit the dust in Asia, mamenchisaurids thrived, evolving into different types, including this half-neck form.
Read more at Discovery News
BICEP2 Gravitational Wave 'Discovery' Deflates
In online French documents briefly released and then removed last night and confirmed by the European Space Agency today, physicists have announced that last year’s much-publicized ‘discovery’ of gravitational waves embedded in the ‘echo’ of the Big Bang was a misstep.
Preempting the official research paper that is planned to be published next week, the ESA, who manages the Planck space telescope data, has gone on the record to say that the BICEP2 measurements of B-mode polarization in the cosmic microwave background (CMB) was caused not by the presence of primordial gravitational waves, but by obscuring dust inside our own galaxy. The CMB is the left-over ancient radiation from the Big Bang that occurred nearly 14 billion years ago.
“Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves,” writes an ESA statement.
This null result doesn’t come as a surprise to many scientists in the field, however.
Since the media storm that surrounded one of the would-be biggest cosmological discoveries in modern history in March 2014, the BICEP2 data has been heavily scrutinized. Although the BICEP2 telescope, a US-led project based near the South Pole, is designed to detect the tell-tail ‘wiggle’ in the polarization of CMB radiation caused by the presence of gravitational waves, great care needs to be taken when interpreting the results.
Should gravitational waves be detected, not only would their discovery be monumental, it would also confirm some key models of the universe’s origin, thereby revealing the mechanisms behind inflation — the split-second expansion of the universe immediately after the Big Bang.
However, between us and the outermost reaches of our observable universe there is magnetized material within our own galaxy. Any radiation detected beyond our galaxy has to travel through the interstellar dust and the signal needs to be corrected for. But to correct for our galaxy’s dust, you need to precisely map it first — this is where the European Planck space telescope comes in.
Before it went silent in 2013, Planck was surveying the sky, mapping the CMB. But it was also mapping the intervening magnetic field and dust content of our galaxy. These data are critical to subtract from CMB measurements if B-mode polarization is to be detected. But in March 2014, when the BICEP2 researchers announced their results to the world, the precision Planck dust map was not available.
Now that the Planck survey data has been processed, it seems that the BICEP2 ‘signal’ of gravitational waves is in fact interference caused by galactic dust.
“When we first detected this signal in our data, we relied on models for Galactic dust emission that were available at the time,” said John Kovac, principal investigator of BICEP2 at Harvard University, Cambridge, Mass. “These seemed to indicate that the region of the sky chosen for our observations had dust polarization much lower than the detected signal.”
Now the BICEP2 and Planck teams are working together in hopes to place some limits on how strong any potential gravitational wave signals will be.
“This joint work has shown that the detection of primordial B-modes is no longer robust once the emission from Galactic dust is removed,” added Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.
“So, unfortunately, we have not been able to confirm that the signal is an imprint of cosmic inflation.”
We will have to wait to read the full details behind this latest twist in the BICEP2 results when the joint Planck-BICEP2 paper is published next week, but it seems certain that the original BICEP2 announcement was premature.
It is important to note, however, that this null result doesn’t disprove the existence of gravitational waves, it just confirms, to a high degree of certainty, that BICEP2 hasn’t detected gravitational waves — yet.
“While we haven’t found strong evidence of a signal from primordial gravitational waves in the best observations of CMB polarization that are currently available, this by no means rules out inflation,” said Reno Mandolesi, principal investigator of the LFI instrument on Planck at University of Ferrara, Italy.
Read more at Discovery News
Preempting the official research paper that is planned to be published next week, the ESA, who manages the Planck space telescope data, has gone on the record to say that the BICEP2 measurements of B-mode polarization in the cosmic microwave background (CMB) was caused not by the presence of primordial gravitational waves, but by obscuring dust inside our own galaxy. The CMB is the left-over ancient radiation from the Big Bang that occurred nearly 14 billion years ago.
“Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves,” writes an ESA statement.
This null result doesn’t come as a surprise to many scientists in the field, however.
Since the media storm that surrounded one of the would-be biggest cosmological discoveries in modern history in March 2014, the BICEP2 data has been heavily scrutinized. Although the BICEP2 telescope, a US-led project based near the South Pole, is designed to detect the tell-tail ‘wiggle’ in the polarization of CMB radiation caused by the presence of gravitational waves, great care needs to be taken when interpreting the results.
Should gravitational waves be detected, not only would their discovery be monumental, it would also confirm some key models of the universe’s origin, thereby revealing the mechanisms behind inflation — the split-second expansion of the universe immediately after the Big Bang.
However, between us and the outermost reaches of our observable universe there is magnetized material within our own galaxy. Any radiation detected beyond our galaxy has to travel through the interstellar dust and the signal needs to be corrected for. But to correct for our galaxy’s dust, you need to precisely map it first — this is where the European Planck space telescope comes in.
Before it went silent in 2013, Planck was surveying the sky, mapping the CMB. But it was also mapping the intervening magnetic field and dust content of our galaxy. These data are critical to subtract from CMB measurements if B-mode polarization is to be detected. But in March 2014, when the BICEP2 researchers announced their results to the world, the precision Planck dust map was not available.
Now that the Planck survey data has been processed, it seems that the BICEP2 ‘signal’ of gravitational waves is in fact interference caused by galactic dust.
“When we first detected this signal in our data, we relied on models for Galactic dust emission that were available at the time,” said John Kovac, principal investigator of BICEP2 at Harvard University, Cambridge, Mass. “These seemed to indicate that the region of the sky chosen for our observations had dust polarization much lower than the detected signal.”
Now the BICEP2 and Planck teams are working together in hopes to place some limits on how strong any potential gravitational wave signals will be.
“This joint work has shown that the detection of primordial B-modes is no longer robust once the emission from Galactic dust is removed,” added Jean-Loup Puget, principal investigator of the HFI instrument on Planck at the Institut d’Astrophysique Spatiale in Orsay, France.
“So, unfortunately, we have not been able to confirm that the signal is an imprint of cosmic inflation.”
We will have to wait to read the full details behind this latest twist in the BICEP2 results when the joint Planck-BICEP2 paper is published next week, but it seems certain that the original BICEP2 announcement was premature.
It is important to note, however, that this null result doesn’t disprove the existence of gravitational waves, it just confirms, to a high degree of certainty, that BICEP2 hasn’t detected gravitational waves — yet.
“While we haven’t found strong evidence of a signal from primordial gravitational waves in the best observations of CMB polarization that are currently available, this by no means rules out inflation,” said Reno Mandolesi, principal investigator of the LFI instrument on Planck at University of Ferrara, Italy.
Read more at Discovery News
Stunning Supernova Has Bubbly Interior
A new three dimensional model of the Cassiopeia A supernova remnant provides insights into how these massive explosions occur.
The detailed model reveals a bubble-like interior of debris that connects with a bright shell of ejecta arranged in multiple circular structures.
"This is the first time we've actually seen such a complete image of what the interior of this thing looks like," said one of the study's authors Professor Robert Fesen of Dartmouth College in New Hampshire.
"It shows big bubbles, big cavities that others suggested might be there, and this shows they really are."
The study is published in the journal Science.
Cassiopeia A was created 340 years ago when a massive star exploded to form a neutron star, making it a good subject for a cosmic post mortem.
In this type of explosion, known as a core-collapse supernova, the outer layers of the star drop in free fall, reaching speeds of 70,000 kilometers per second, a significant fraction of the speed of light.
Somehow, that material suddenly stops and ends up traveling the other way at up to 10,000 kilometers per second. Scientists call this sudden reversal a "bounce", but until now they've been unsure exactly how it happens.
"We know the core collapses down to form a neutron star, and the rest blows up somehow after that," said Fesen. "But most of our models have had problems blowing up stars because the outer layers of the star collapse into the core and smother the explosion!"
Stellar autopsy
Distant supernovae outside our galaxy are difficult to study because they're so far away.
Fesen and co-author Dr Dan Milisavljevic, of the Harvard-Smithsonian Center for Astrophysics, used near-infrared spectroscopy to measure expansion velocities of extremely faint material inside the supernova remnant, providing the crucial third dimension for the 3D model.
"We're sort of like bomb squad investigators," said Milisavljevic. "We examine the debris to learn what blew up and how it blew up. Our study represents a major step forward in our understanding of how stars actually explode."
The study revealed that cavities in the supernova's interior are caused by plumes of radioactive nickel 56, said Fesen.
"Nickel 56 will eventually decay into iron, and during that decay process a lot of energy is generated. These plumes of nickel move through the non-radioactive material, pushing it away and making cavities.
Read more at Discovery News
The detailed model reveals a bubble-like interior of debris that connects with a bright shell of ejecta arranged in multiple circular structures.
"This is the first time we've actually seen such a complete image of what the interior of this thing looks like," said one of the study's authors Professor Robert Fesen of Dartmouth College in New Hampshire.
"It shows big bubbles, big cavities that others suggested might be there, and this shows they really are."
The study is published in the journal Science.
Cassiopeia A was created 340 years ago when a massive star exploded to form a neutron star, making it a good subject for a cosmic post mortem.
In this type of explosion, known as a core-collapse supernova, the outer layers of the star drop in free fall, reaching speeds of 70,000 kilometers per second, a significant fraction of the speed of light.
Somehow, that material suddenly stops and ends up traveling the other way at up to 10,000 kilometers per second. Scientists call this sudden reversal a "bounce", but until now they've been unsure exactly how it happens.
"We know the core collapses down to form a neutron star, and the rest blows up somehow after that," said Fesen. "But most of our models have had problems blowing up stars because the outer layers of the star collapse into the core and smother the explosion!"
Stellar autopsy
Distant supernovae outside our galaxy are difficult to study because they're so far away.
Fesen and co-author Dr Dan Milisavljevic, of the Harvard-Smithsonian Center for Astrophysics, used near-infrared spectroscopy to measure expansion velocities of extremely faint material inside the supernova remnant, providing the crucial third dimension for the 3D model.
"We're sort of like bomb squad investigators," said Milisavljevic. "We examine the debris to learn what blew up and how it blew up. Our study represents a major step forward in our understanding of how stars actually explode."
The study revealed that cavities in the supernova's interior are caused by plumes of radioactive nickel 56, said Fesen.
"Nickel 56 will eventually decay into iron, and during that decay process a lot of energy is generated. These plumes of nickel move through the non-radioactive material, pushing it away and making cavities.
Read more at Discovery News
Hubble Finds Galaxy's Stars Scattered Far from Home
This mesmerizing observation by the Hubble Space Telescope shows galaxy NGC 7714 in a state of turmoil.
Between 100-200 million years ago, when dinosaurs roamed Earth, NGC 7714 got too close to another galaxy (NGC 7715, out of frame, right) and the extreme tidal forces dragged one of its once-elegant spiral arms deep into intergalactic space. The scattered stars now form a stellar bridge to the second galaxy, exchanging star-forming material.
Both galaxies are approximately 100 million light-years from Earth.
This violent galactic collision wasn’t all bad news for NGC 7714, however. The encounter caused disruption in the interstellar gasses it contains, triggering a wave of new star formation throughout the galactic spirals. The wave of star birth has been captured as bright blue by Hubble’s optics.
Due to the frenzied birth of new stars, astronomers refer to NGC 7714 as a Wolf-Rayet starburst galaxy. Many of the young, massive stars are known as Wolf-Rayets, which as very massive, hot, tumultuous stars that live fast and die young, shedding huge quantities of superheated gases before they erupt as supernovae.
So what started as a violent galactic collision, ended up as a frenzy of star birth that, eventually, will see the Wolf-Rayets explode, seeding NGC 7714 with heavier elements that will go on to form other stars and, ultimately, star systems.
From Discovery News
Between 100-200 million years ago, when dinosaurs roamed Earth, NGC 7714 got too close to another galaxy (NGC 7715, out of frame, right) and the extreme tidal forces dragged one of its once-elegant spiral arms deep into intergalactic space. The scattered stars now form a stellar bridge to the second galaxy, exchanging star-forming material.
Both galaxies are approximately 100 million light-years from Earth.
This violent galactic collision wasn’t all bad news for NGC 7714, however. The encounter caused disruption in the interstellar gasses it contains, triggering a wave of new star formation throughout the galactic spirals. The wave of star birth has been captured as bright blue by Hubble’s optics.
Due to the frenzied birth of new stars, astronomers refer to NGC 7714 as a Wolf-Rayet starburst galaxy. Many of the young, massive stars are known as Wolf-Rayets, which as very massive, hot, tumultuous stars that live fast and die young, shedding huge quantities of superheated gases before they erupt as supernovae.
So what started as a violent galactic collision, ended up as a frenzy of star birth that, eventually, will see the Wolf-Rayets explode, seeding NGC 7714 with heavier elements that will go on to form other stars and, ultimately, star systems.
From Discovery News
The World’s Tiniest, Most Adorable Snake Can Curl Up on a Quarter
But what if your wildly irresponsible father hadn’t just left a shrink ray lying around—what if instead evolution had over the millennia shrunk you down, bit by bit, until a beetle seemed a formidable foe? For an answer to that, you’d have to ask the smallest snake in the world, the Barbados threadsnake, which isn’t even recognizable as a serpent anymore. It’s 4 inches long, about as thick as spaghetti, and looks more like a worm than a snake. And the challenges its diminutive size brings are many—save for falling into cereal bowls, of course.
First of all, there’s the matter of feeding. According to Temple University’s S. Blair Hedges, who first described the creature in 2008, the Barbados threadsnake has “a pretty narrow diet because their mouth can barely open. I mean, they’re small to begin with, but then their mouths don’t open like a normal snake. They just barely open up enough to squeeze in a little microscopic insect.”
| A threadsnake post-arcade. |
Threadsnakes are burrowers, spending their days squirming through soft soil, and that may be due in part to another problem that small creatures face. Because the extremely thin snake has a higher ratio of surface area to volume—compared to, say, a polar bear, which has a lower ratio with its bulky body—it’s more susceptible to losing moisture. By kicking back in the wet dirt, the snake can better avoid desiccation (being so bulky, by the way, also helps the polar bear better retain heat).
Also an issue is how they bear their own young. How many eggs a snake can lay varies greatly, the Eastern mud snake here in the States, for instance, can produce as many as 100, but the threadsnake is at the opposite end of the spectrum with a grand total of…one. Mama threadsnake bets on one single egg.
| The Western blind snake, Leptotyphlops humilis (which shares a genus with the Barbados threadsnake), and her highly elongated eggs. It’s pink because that’s in style right now. |
This is an extreme evolutionary tradeoff. By growing so small, the threadsnake has sacrificed high fecundity, that is, how many young it’s able to produce. This is of course rather risky. We humans having a single child is one thing, since we stick around to dotingly care for it for a long, long time (well, ideally at least). But most reptiles lay their eggs and just take off. Yet here we have a tiny snake that’s been getting along perfectly fine dropping just one egg. Problem is, its life history as a whole and its ecology remain very much mysterious. For all we know the females could actually stick around and guard their hatchling like some species of reptile do. “We know almost nothing about these because they’re so rare,” said Hedges. “There’s only a few specimens that have ever been seen and collected. Nobody’s ever studied them ecologically.”
But we can be sure that there’s a very good reason why the threadsnake got so tiny: shrink rays. Wait, no. Not shrink rays.
Little Big Planet
When an island forms, it’s ripe for conquering. Plants and animals get there any number of ways: swimming, floating on debris after a hurricane, flying, blowing in the wind (spiders can float hundreds of miles by sending out silk that gets caught up in gusts). And when the first creatures arrive, they find a whole lot of open jobs in the ecosystem just asking to be taken, known as niches. And those new jobs aren’t necessarily the ones the critters had back on the mainland. This may have been what happened to the threadsnake. “This species, even though it’s a snake,” said Hedges, “it could be filling a niche of a smaller invertebrate like a centipede or something like that on the mainland.”
Read more at Wired Science
Jan 29, 2015
Mystery of Baleen Whale's Hearing May Be Solved
In what a researcher calls a "grand discovery," the question of how baleen whales hear may have been answered, solving a long-standing mystery.
Baleen whales, the largest animals on Earth at about 65 to 80 feet long, can emit vocalizations at very low frequencies, at wavelengths sometimes longer than the whales themselves. But how they hear, has remained to scientists a bit of a puzzle.
Rather than use more traditional whale-hearing analysis -- relying on anatomic study and sound-playback experiments with whales in controlled environments -- two researchers from San Diego decided to use computational horsepower and 3D software to tackle the problem.
San Diego State University biologist Ted W. Cranford and University of California, San Diego engineer Petr Krysl created a three-dimensional computer model of a baleen whale's head, one that would include the skin, skull, eyes, ears, tongue, brain, muscles, and jaws.
For their test subject, the pair obtained the head of a fin whale that beached in 2003 and then ran it through an X-ray CT scanner.
Once they had the head scan, Cranford and Krysl ran simulations of how sound travels through the whale's brain. To get the detail they needed, they used a technique called finite element modeling, in which the data representing the head parts and skull were separated out into tiny elements by the millions, the relationships between the elements tracked.
Sound can reach a baleen whale's ear bones on its skull in two ways: the sound's pressure waves can go through the animal's soft tissue; or the sounds can vibrate along the skull itself, in a process called "bone induction."
The problem with the soft-tissue, pressure, route, the researchers said, is that it's ineffective when sound waves are longer than the whale's body. But with the bone induction process, those longer waves become amplified as they vibrate in the creature's skull.
The scientists' computer modeling showed that the bone induction process was about four times more sensitive to low-frequency sounds than the soft-tissue, pressure mechanism.
What's more, their modeling predicted that bone induction is 10 times more sensitive to the lowest frequencies used by fin whales (10 Hz-130 Hz).
Read more at Discovery News
Baleen whales, the largest animals on Earth at about 65 to 80 feet long, can emit vocalizations at very low frequencies, at wavelengths sometimes longer than the whales themselves. But how they hear, has remained to scientists a bit of a puzzle.
Rather than use more traditional whale-hearing analysis -- relying on anatomic study and sound-playback experiments with whales in controlled environments -- two researchers from San Diego decided to use computational horsepower and 3D software to tackle the problem.
San Diego State University biologist Ted W. Cranford and University of California, San Diego engineer Petr Krysl created a three-dimensional computer model of a baleen whale's head, one that would include the skin, skull, eyes, ears, tongue, brain, muscles, and jaws.
For their test subject, the pair obtained the head of a fin whale that beached in 2003 and then ran it through an X-ray CT scanner.
Once they had the head scan, Cranford and Krysl ran simulations of how sound travels through the whale's brain. To get the detail they needed, they used a technique called finite element modeling, in which the data representing the head parts and skull were separated out into tiny elements by the millions, the relationships between the elements tracked.
Sound can reach a baleen whale's ear bones on its skull in two ways: the sound's pressure waves can go through the animal's soft tissue; or the sounds can vibrate along the skull itself, in a process called "bone induction."
The problem with the soft-tissue, pressure, route, the researchers said, is that it's ineffective when sound waves are longer than the whale's body. But with the bone induction process, those longer waves become amplified as they vibrate in the creature's skull.
The scientists' computer modeling showed that the bone induction process was about four times more sensitive to low-frequency sounds than the soft-tissue, pressure mechanism.
What's more, their modeling predicted that bone induction is 10 times more sensitive to the lowest frequencies used by fin whales (10 Hz-130 Hz).
Read more at Discovery News
Corpse of 200-Year-Old Monk Found in Lotus Position
The amazingly intact remains of a meditating monk have been discovered in the Songinokhairkhan province of Mongolia, according to a report in Mongolia’s Morning News.
The mummified body, which was covered in animal skin, has been sitting in the lotus position for about 200 years.
According to the report, no information is so far available as to where the body was found.
“The only details we learned was that it was covered with a cattle skin,” the newspaper wrote.
Researchers at the Ulaanbaatar National Centre of Forensic Expertise are now analyzing the remains.
According to The Siberian Times, experts are speculating over whether the mummy is a “teacher of famous Lama Dashi-Dorzho Itigilov,” a Buddhist Lama of the Tibetan Buddhist tradition who was born in 1852.
Itigilov also died while meditating in lotus posture and was buried in 1927 in that position, his remains laid to rest in a pine box. When he was exhumed in 1955 and in 1973, astonished monks found the body in near-perfect condition and still sitting upright.
From Discovery News
The mummified body, which was covered in animal skin, has been sitting in the lotus position for about 200 years.
According to the report, no information is so far available as to where the body was found.
“The only details we learned was that it was covered with a cattle skin,” the newspaper wrote.
Researchers at the Ulaanbaatar National Centre of Forensic Expertise are now analyzing the remains.
According to The Siberian Times, experts are speculating over whether the mummy is a “teacher of famous Lama Dashi-Dorzho Itigilov,” a Buddhist Lama of the Tibetan Buddhist tradition who was born in 1852.
Itigilov also died while meditating in lotus posture and was buried in 1927 in that position, his remains laid to rest in a pine box. When he was exhumed in 1955 and in 1973, astonished monks found the body in near-perfect condition and still sitting upright.
From Discovery News
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