Wednesday, 3 February 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Telescope Finds Galaxy’s Most Massive Star Yet

Posted: 03 Feb 2010 03:00 AM PST


This glowing stellar nursery is home to the most massive star yet found in the Milky Way galaxy.

Captured by theEuropean Southern Observatory's 27 f00t-diameter Very Large Telescope at Cerro Paranal, Chile, the imageabove combinesdatataken with violet, red, and infrared filters.

The nebula, NGC 3603, is surrounded by a cloud of glowing gas and dust in the Carina spiral arm of the Milky Way galaxy, about 20,000 light-years from Earth in the Carina constellation. This active star-forming region is one of the brightest and most compact star clusters in our galaxy. The cosmic nursery is teeming with thousands of young, massive suns, including several blue supergiants and three massive Wolf-Rayet stars. These brilliant stars eject huge amounts of mass before blazing out in spectacular supernova explosions.The most massive star in the cluster is 116 times as massive as the Sun.

The photo below shows the broader area around the NGC 3603 nebula.


Images: ESO

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New Look at Big Bang Radiation Refines Age of Universe

Posted: 03 Feb 2010 12:41 AM PST


Six papers posted online present new satellite snapshots of the earliest light in the universe. By analyzing these images, cosmologists have made the most accurate determination of the age of the cosmos, have directly detected primordial helium gas for the first time and have discovered a key signature of inflation, the leading model of how the cosmos came to be.

sciencenewsThe analysis, based on the first seven years of data taken by NASA's Wilkinson Microwave Anisotropy Probe, also provides new evidence that the mysterious entity revving up the expansion of the universe resembles Einstein's cosmological constant, a factor he inserted but later removed from his theory of general relativity. In addition, the data reveal that theorists don't have the right model to explain the hot gas that surrounds massive clusters of galaxies.

Researchers studying the light, which was generated at the birth of the cosmos but was seen by the satellite as it appeared when it first escaped into space about 400,000 years later, unveiled the findings in six papers posted online January 26. The ancient light, known as the cosmic microwave background, is peppered with hot and cold spots, signs of the tiny primordial lumps from which galaxies grew.

To calculate the age of the universe, scientists including David Spergel of Princeton University and Charles Bennett of Johns Hopkins University in Baltimore compared the size of those hot and cold spots today with the size of the spots when the radiation was first released into space. Using data from WMAP along with studies of distant supernovas and other phenomena, the team finds that the universe is 13.75 billion years old, give or take 0.11 billion. (By comparison, the team's previous calculation, which used the same method but included only five years of satellite observations, had pegged the universe at 13.73 billion years, plus or minus 0.12 billion.)

Data from the WMAP satellite supports the idea that the early universe inflated rapidly, Bennett says. Inflation theory, which posits that the universe ballooned from subatomic scale to the size of a soccer ball during its first 10-33 seconds, has had great success in explaining the structure of the universe. According to the theory, fluctuations in the intensity of microwave background radiation over larger spatial scales should be slightly bigger than those on smaller scales. The satellite, which was launched in 2001 and will make its last observations this fall, has confirmed that behavior.

"This is a really strong endorsement for the theory," says Scott Dodelson of the Fermi National Accelerator Laboratory in Batavia, Ill.

The standard model of cosmology — replete with inflation, invisible material known as dark matter and something called dark energy, which is believed to accelerate cosmic expansion—"is a wild idea," admits Bennett. But with the newest analysis of the satellite observations "we have confronted the model against the data in a substantially new way… and this picture is holding up very well."

By using the satellite data to measure the speed of acoustic oscillations — the cosmic equivalent of sound waves — astronomers have confirmed that the early universe forged helium in addition to hydrogen, just as the Big Bang theory has long predicted. Previous studies were based on the amount of helium present in the cosmos' oldest stars rather than a direct detection of the gas in the early universe.

"This opens up a new window for measuring primordial helium," Dodelson comments.

The detection "is not a surprise, but it's nice to have confirmation," Spergel says.

Researchers also analyzed the satellite data to discern the diversity of neutral elementary particles called neutrinos in the universe. Physicists know of three types—the electron neutrino, the muon neutrino and the tau neutrino. But the current data would be consistent with the existence of either three or four types. The analysis of an additional two years of observations from the satellite may settle whether a fourth type exists, says Bennett.

In a separate finding, WMAP detected the abundance of microwave background photons in the vicinity of galaxy clusters. Here, the satellite has come into conflict with theory. Energetic electrons associated with galaxy clusters are known to interact with some of the microwave background photons, kicking the photons to higher energies than the probe can detect. As a result, the probe ought to record fewer microwave-energy photons in the vicinity of clusters.

The probe indeed records a deficit, but it's only about half the amount predicted by galaxy cluster theory. The South Pole Telescope, a ground-based experiment that also studies the cosmic microwave background, also finds a lower-than-expected deficit. The mismatch suggests that theorists will have to revise their understanding of galaxy clusters, says Bennett.

Image: NASA/WMAP Science Team

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Video: Solar Eclipse Seen From Space

Posted: 02 Feb 2010 12:03 PM PST

A European satellite launched late last year has returned a new animation of the annular solar eclipse that occurred on Jan. 15.

The images returned by the Proba 2 mission are the first of their kind and part of the first set of data released by the European Space Agency. A similar, more robust sun-observing platform, the Solar and Helisopheric Observatory, is unable to see eclipses.

The images that compose the animation were taken about one minute apart. The eclipse was viewable from Earth for more than 11 minutes.

The new satellite is just beginning its lifespan and was largely conceived as a test of new hardware more than a scientific mission. But the small satellite — a bit smaller than a cubic meter (or about 35 cubic feet) — will also deliver this kind of novel view of the sun.


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The Potential for a 40-MPH Man

Posted: 02 Feb 2010 11:15 AM PST


The human frame isbuilt tohandle running speeds up to 40 miles per hour, scientists say. The only limiting factor is not how much brute force is required to push off the ground as previously thought, but how fast our muscle fibers can contract to ramp up that force.

"If you just find a way to rev up those contractile fibers for the muscle, then everything else from human biology and gait would allow us to be that fast," said physiologist Peter Weyand of Southern Methodist University, lead author ofa study published Jan. 21 in the Journal of Applied Physiology.

For years, scientists have sought to find the physiological limits of human running speed, and to understand why even the world's fastest man, Jamaican sprinter Usain Bolt,can't outrun some animals.Bolt'stop speed of 27.3 miles an hour can't match that of horses, dogs or the hopping kangaroo, whichcan travel at35 miles per hour.

"The current best guess as to why we can't run any faster is it's something to do with the maximum force that our legs can impose or experience," said zoologist Jim Usherwood of the Royal Veterinary College in London.

Earlier studies found that elite sprinters and average sprinters outperformed their mediocre counterparts in two ways: They were able to push harder on the ground in relation to their body's weight with each step, and they were able to do that in a shorter period of time. For instance, Bolt generates almost a ton of force in his leg in the less than a tenth of a second his foot is on the ground, Weyand said. The force you can generate before leaving the ground is a function of the rate at which muscle fibers generate force multiplied by the time the foot touches the ground.

But the previouswork didn't reveal whether it is the amount of time the foot is pushing on the ground or the maximum force the leg is capable of that limits human running speed.

To get to the bottom of the human speed limit, Weyand and colleaguesstudied seven athletes, from an all-American track star to a dancer, as theysprinted forward, hopped on one leg and ran backwards on a turbo treadmill outfitted with force sensors. The team measured speed, upward force as each foot struck the ground, and the time the foot spent on the ground between strides.

The one-legged hop generated much more force in the leg than sprinting did, mainly because a runner has to jump higher in order to land on the same foot. Because the athlete's legs were capable of generating more force than when they run, the amount of force can't bewhat's limiting the runners' forward speeds.

The backwards run showed that the contact time with the groundwas almost identical duringeach athlete'sfastest forward and backward runs, suggesting contact time was the limiting factor keeping them from going faster in any direction.

This suggests the only way to increase speed is to generate force more quickly during the limited time the foot is on the ground. The key todoing thisis increasing how fast the muscle fibers can contract to produce force. If that were possible, Weyand's team calculated that humans could theoretically runas fast as35 or 40 milesper hour, based on our gait and the maximum forces our muscles can generate.

One option would be to increase the proportion of ultrafast 2X type muscle fiber, one of three types of mammalian muscle fibers. Studies have shown that athletes can slightly increase their 2X fibers by training intensely and then taking a break for a few weeks, he said.

But even if a training regimen could be designed to quicken our muscle fibers enough to achieve our fullrunning potential, animals like cheetahs and dogs will still leave us in the dust. These animals outrun us not because they have faster muscle fibers, but because of their unique gait, the study concluded.

"When their forelimbs hit the ground, their whole spine just bends like crazy," Weyand said. That allows them to keep their feet on the ground longer, building up force, while still maintaining a forward momentum.

Usherwood agreed with the basic conclusion of the paper, that "actually we can produce lots more force if we do all sorts of odd things like hopping on one leg. Just the biggest force you can cope with with doesn't determine how fast you sprint."

But he's skeptical about the potential for a 40-mile-an-hour man. 'The authors are playing a fun game, of 'what if,'" he said. But even if our muscle fibers were faster, other limitations, like how fast we can swing our legs, are sure to kick in, he said.

Photo of Usain Bolt: antonhazelwinkel/Flickr

Citation: "The biological limits to running speed are imposed from the ground up" Peter G. Weyand, Rosalind F. Sandell, Danille Naomi Leoni Prime, and Matthew W. Bundle, Journal of Applied Physiology, Jan. 21, 2010

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Plant-Virus Tricks Teach Evolutionary Pest Management

Posted: 02 Feb 2010 11:03 AM PST


The cucumber mosaic virus uses a clever subterfuge to spread — it changes the way host plants smell. It's a neat example of evolutionary exploitation and a lesson in how managing the dynamics of evolution may help control pests.

The virus causes plants to produce aphid-attracting odors. At the same time, it makes the plant sickly. Bugs arrive at the plant, find it a poor home, and quickly depart. But their brief landing is sufficient to pick up the virus, which they carry to other, healthier plants.

"The mode of transmission is a major factor influencing the effects of pathogens on plants," said Mark Mescher, a Penn State University chemical ecologist. "In human and agricultural systems, it's time to start moving beyond thinking how to directly manage a pest or pathogen, and towards managing their evolution."

Mescher, who describes the transmission of the cucumber mosaic virus in a study published Monday in the Proceedings of the National Academy of Sciences, specializes in the chemical cues plants use to communicate. These are surprisingly sophisticated: His earlier work involved predator-attracting chemicals released by plants when eaten by grazers.

In the PNAS study, Mescher's team showed how aphids — tiny, ubiquitous insects that feed on plant sap —preferred infected squash plants, though they left shortly after landing. This is likely because chemical cue production was doubled in infected plants: Though withered and sickly, they smelled large and healthy from a distance.

The findings add to a growing body of research on odor-changing diseases. Trees afflicted by Dutch Elm disease produce insect-attracting chemicals, as does wheat infected with rust fungi. In the animal world, research has found that hamsters infected with Leishmaniasis, a flesh-eating disease common in much of the developing world, attract disease-spreading sandflies. Another study found that mosquitoes appear drawn by smell to people with malaria, though the disease is as dangerous to them as to us.

Studies like these hint at little-appreciated disease dynamics, in which pathogens have evolved subtle ways of spreading themselves, with their ostensible targets just one stop in a network of transmission. They may also suggest new targets for controlling diseases that have evaded standard treatments.

Mescher, who is now studying malarial odor changes, said that such interventions represent a comprehensive approach to disease. "We need to think of what the transmission dynamics are that lead to more harmful pathogens, and what dynamics lead to less harmful pathogens," he said.

Image: (A) A healthy cucumber plant; (B) an infected plant; (C) aphids; )D) aphids./PNAS

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Citation: "Deceptive chemical signals induced by a plant virus attract insect vectors to inferior hosts." By Kerry E. Mauck, Consuelo M. DeMoraes, and Mark C. Mescher. Proceedings of the National Academy of Sciences, Vol. 107 No. 5, February 2, 2010.

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Hubble Spots First Potential Asteroid Collision

Posted: 02 Feb 2010 10:10 AM PST


The X marks the spot of a suspected head-on collision between two asteroids imaged by the Hubble Space Telescope's new-and-improved Wide Field Camera.

If it's confirmed by further observations, it would be the first time that scientists have detected the interplanetary collision between objects in the asteroid belt, though they believe that such occurrences are common.

The complex structure of the debris is what makes astronomers think they may be seeing something new around the sun. The main nucleus of the object, P/2010 A2, is actually located outside its dust halo, something that's never been seen in a comet-like object before.

"The filamentary appearance of P/2010 A2 is different from anything seen in Hubble images of normal comets, consistent with the action of a different process," said David Jewitt, an astronomer at the University of California Los Angeles, in a press release.

They hypothesize that the filaments are made up of dust and gravel created by a high speed impact that could have occurred at 11,000 miles per hour.

"If this interpretation is correct, two small and previously unknown asteroids recently collided, creating a shower of debris that is being swept back into a tail from the collision site by the pressure of sunlight," Jewitt said.

Image: NASA, ESA, and D. Jewitt. XL version available.

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NASA Radar Jet Acquires First 3-D Image of Haiti

Posted: 02 Feb 2010 10:05 AM PST

NASA's radar-equipped jet has returned its first 3-D image of Port-au-Prince, Haiti. This false-color image clearly shows the Enriquillo-Plantain Garden Fault extending east of the city.

The image supports a Jan. 21 U.S. Geological Survey report that suggested the section of the fault (indicated by the black arrow above) nearest to Port-au-Prince(yellow arrow)did notslip significantly in the magnitude 7 Jan. 12 earthquake.

The new image, taken by JPL's Uninhabited Aerial Vehicle Synthetic Aperture Radar attached to a modified Gulfstream III jet, shows that the ground rupture moved westward from the epicenter. The section of the fault in the image did not rupture, a situation that increases the risk of another significant earthquake in the future.

The USGS report noted that two large earthquakesstruck the area in1751 and 1770, most likely on the Enriquillo fault, which runs from western Haiti into the Dominican Republic. If a similar succession occurs in the coming years, it could be devastating, particularly if Haiti is not rebuilt with this risk in mind.

The UAVSAR will be flown over the area repeatedlyin the coming days. Data from the first flights will be compared to later flights to measure minute changes in the landscape that could reveal how quickly the earth on either side of the fault is moving and building up stress. This will help scientists assess the risk of more quakes.

The colors in the image, which shows a swath of about 12.5 miles,are the result of three different radar polarizations that make vegetation appear green, water appear blue and urban areas look reddish.

After imaging Haiti, the jet will head to Central America on a previously scheduled trip to study volcanoes, forests and Mayan ruins. NASA says the UAVSAR will eventually beadapted to flyin unmanned aircraft such as the Northrop Grumman Global Hawk.


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