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Saturday, August 30, 2008

Integral locates origin of high-energy emission from Crab Nebula

Thanks to data from ESA’s Integral gamma-ray observatory, scientists have been able to locate where particles in the vicinity of the rotating neutron-star in the Crab Nebula are accelerated to immense energies.

The discovery, resulting from more than 600 individual observations of the nebula, put in place another piece of the puzzle in understanding how neutron stars work.

Rotating neutron-stars, or pulsars, are known to accelerate particles to enormous energies, typically one hundred times more than the most powerful accelerators on Earth, but scientists are still uncertain exactly how these systems work and where the particles are accelerated.

A step forward in this understanding is now accomplished thanks to a team of researchers from the UK and Italy, led by Professor Tony Dean of the University of Southampton, who studied high-energy polarised light emitted by the Crab Nebula – one of the most dramatic sights in deep space.

The Crab Nebula is the result of a supernova explosion which was seen from Earth on 4 July 1054. The explosion left behind a pulsar with a nebula of radiating particles around it. The pulsar contains the mass of the Sun squeezed into a volume of about 10 km radius, rotating very fast – about 30 times a second – thereby generating very powerful magnetic fields and accelerating particles. A highly collimated jet, aligned with the spin axis of the pulsar and a bright radiating ‘donut’ structure (or torus) around the pulsar itself, are also seen.

So, the Crab is known to accelerate electrons - and possibly other particles - to extremely high speed, and so produces high energy radiation. But where exactly are these particles accelerated?

Looking into the heart of the pulsar with Integral’s spectrometer (SPI), the researchers made a detailed study to assess the polarization – or the alignment - of the waves of high-energy radiation originating from the Crab.


They saw that this polarised radiation is highly aligned with the rotation axis of the pulsar. So they concluded that a significant portion of the electrons generating the high-energy radiation must originate from a highly-organised structure located very close to the pulsar, very likely directly from the jets themselves. The discovery allows the researchers to discard other theories that locate the origin of this radiation further away from the pulsar.

Professor Tony Dean of the University’s School of Physics and Astronomy commented that the discovery of such alignment – also matching with the polarisation observed in the visible band - is truly remarkable. “The findings have clear implications on many aspects of high energy accelerators such as the Crab,” he added.

"The detection of polarised radiation in space is very complicated and rare, as it requires dedicated instrumentation and an in-depth analysis of very complex data”, said Chris Winkler, Integral Project Scientist at ESA. “Integral’s ability to detect polarised gamma-radiation and, as a consequence, to obtain important results like this one, confirms it once more as a world-class observatory.”


Notes for editors:

The results are published in the 29 August issue of the scientific journal Science, in a paper titled ‘Polarized gamma-ray emission from the Crab’, by: A. J. Dean, D.J. Clark, V.A.McBride, A.J.Bird, A.B.Hill and S.E.Shaw (University of Southampton’s School of Physics and Astronomy); J.B. Stephen and L. Bassani (INAF-IASF, Bologna); and A. Bazzano and P. Ubertini (INAF-IASF, Roma).

NASA Mars Rover Opportunity Ascends to Level Ground

NASA's Mars Exploration Rover Opportunity has climbed out of the large crater that it had been examining from the inside since last September.

"The rover is back on flat ground," an engineer who drives it, Paolo Bellutta of NASA's Jet Propulsion Laboratory, announced to the mission's international team of scientists and engineers.

Opportunity used its own entry tracks from nearly a year ago as the path for a drive of 6.8 meters (22 feet) bringing the rover out over the top of the inner slope and through a sand ripple at the lip of Victoria Crater. The exit drive, conducted late Thursday, completed a series of drives covering 50 meters (164 feet) since the rover team decided about a month ago that it had completed its scientific investigations inside the crater.

"We're headed to the next adventure out on the plains of Meridiani," said JPL's John Callas, project manager for Opportunity and its twin Mars rover, Spirit. "We safely got into the crater, we completed our exploration there, and we safely got out. We were concerned that any wheel failure on our aging rover could have left us trapped inside the crater."

The Opportunity mission has focused on Victoria Crater for more than half of the 55 months since the rover landed in the Meridiani Planum region of equatorial Mars. The crater spans about 800 meters (half a mile) in diameter and reveals rock layers that hold clues to environmental conditions of the area through an extended period when the rocks were formed and altered.

The team selected Victoria as the next major destination after Opportunity exited smaller Endurance Crater in late 2004. The ensuing 22-month traverse to Victoria included stopping for studies along the route and escaping from a sand trap. The rover first reached the rim of Victoria in September 2007. For nearly a year, it then explored partway around the rim, checking for the best entry route and examining from above the rock layers exposed in a series of promontories that punctuate the crater perimeter.

Now that Opportunity has finished exploring Victoria Crater and returned to the surrounding plain, the rover team plans to use tools on the robotic arm in coming months to examine an assortment of cobbles -- rocks about fist-size and larger -- that may have been thrown from impacts that dug craters too distant for Opportunity to reach.

JPL, a division of the California Institute of Technology, Pasadena, manages the rovers for the NASA Science Mission Directorate, Washington. For images and information about NASA's Opportunity and Spirit Mars rovers, visit http://www.nasa.gov/rovers and http://marsrovers.jpl.nasa.gov.

EXCLUSIVE: NASA to study extending shuttle era to 2015

NASA Administrator Michael Griffin has ordered his subordinates to study how the agency could fly the space shuttle beyond its planned retirement in 2010, according to an internal e-mail obtained by the Orlando Sentinel.

The decision signals what could be a huge change in NASA policy. Griffin repeatedly has rejected the notion of extending the shuttle era beyond its 2010 retirement date, arguing it could cripple the fledgling Constellation program, a system of new rockets and capsules meant to replace the shuttle in 2015.

But Griffin has been under enormous external pressure. Sen. John McCain recently asked the White House to stop dismantling parts of the shuttle program for at least a year. At the same time, eroding relations with Russia have motivated lawmakers to find a way to fill the five-year gap between the shuttle's retirement and the maiden voyage of Constellation in 2015. The current plan calls for NASA to buy Russian spacecraft during the gap.

One NASA official said such "what-if studies" represent "prudent planning," especially in light of suggestions made by McCain, the Republican presidential nominee, who would dictate the agency's future if he captures the White House.

But the email, sent on Wednesday, August 27, by John Coggeshall, manager of "Manifest and Schedules" at Johnson Space Center in Houston, suggested that the analysis was more than just a contingency study.

"We want to focus on helping bridge the gap of US vehicles travelling to the ISS as efficiently as possible," it said.

The upcoming study raised the idea of retiring one of the three remaining orbiters, possibly for spare parts. "(We) don't necessarily need all 3 orbiters either," said the email. "We have been encouraged not to focus on a certain set of assumptions or costs," said the email.

But cost has been the exact reason why Griffin has dismissed the idea of extending the shuttle era. To have enough money to build Constellation's Ares 1 rocket and Orion crew capsule, NASA must spending stop money on shuttle flights. At one point last year, he estimated that it would cost as much as $4 billion a year to fly the shuttle beyond 2010.

NASA' current budget is about $17 billion.

"Continuing to fly the Shuttle beyond 2010 does not enhance U.S. human spaceflight capability, but rather delays the time until a new capability exists and increases the total life cycle cost to bring the new capability on line," he told Congress in November.

Another worry: NASA already has begun unplugging parts of the shuttle system. It has already terminated many contracts with vendors who make shuttle parts and NASA facilities already have begun converting its systems to handle the new Constellation program.

Wayne Hale, a NASA deputy assistant administrator and until recently the shuttle-program manager, has said that this fall marks the point of no return. That's when NASA is supposed to start ripping out the giant welding equipment and other machinery at Michoud Assembly Facility in New Orleans, which makes the shuttle's giant external fuel tank.

In a blog posted Thursday, Hale said that flying shuttle and building Constellation would strain NASA's budgets and overextend its workforce. "Hey, I am the biggest shuttle hugger there is. I think it is the best spacecraft ever built. But I also deal in the real world," he wrote.

"Where does the money come from? Where do the people -- who should be working on the moon rocket -- where do they come from? We started shutting down the shuttle four years ago. That horse has left the barn," he wrote.

Read the email: Download nasa_email.doc

NASA's 'electronic nose' could sniff out cancer

From rocket science to brain surgery: a device designed to sniff out leaks on the space shuttle may soon guide surgeons as they operate on cancer patients.

The ENose was originally developed by NASA's Jet Propulsion Laboratory in Pasadena, California, to detect low-level leaks of ammonia in shuttles. It is based on polymer films whose electrical conductivity varies as they encounter different substances. Now its creators believe the ENose could act as a highly sensitive detector of the characteristic compounds produced by cancer cells.

Such a device could be invaluable for surgeons operating on areas where spotting tumour tissue is particularly tricky. Surgeons currently rely on visual inspection to locate cancerous tissue, referring back to scans taken before surgery. But brain tissue, for example, is hard to distinguish from cancer, and it also changes shape when the skull is opened, so the scans don't match what the surgeon sees. That makes it difficult to cut out all the cancerous tissue while avoiding damage to healthy areas.

Babak Kateb of City of Hope Medical Center in Duarte, California, says the ENose has correctly diagnosed lung cancer and diabetes in patients who have breathed into it. He and his colleagues believe the device could be linked to other brain imaging and mapping devices to create a real-time high-resolution image of the brain that pinpoints cancer hotspots.

The work was presented at the International Brain Mapping & Intraoperative Surgical Planning Society Conference at the University of California, Los Angeles this week.

Now Hear This: Don't Remove Earwax

The gooey, golden stuff that builds up inside your ears should stay there, according to national guidelines on earwax removal released today.

"[Earwax] is not intrinsically evil stuff, and consequently does not have to be removed merely because it's present," said Peter Roland, an ear, nose and throat doctor at the University of Texas Southwestern Medical Center at Dallas. "In fact, it serves a function and so if you don't need to take it out, you should just leave it alone."

Roland chaired a panel of doctors in charge of the new guidelines for earwax removal issued by the American Academy of Otolaryngology - Head and Neck Surgery Foundation (AAO-HNSF). The guidelines are intended to serve two purposes: to determine under what circumstances earwax needs to be removed, and to give doctors the scoop on which removal methods work best.

They hope the guidelines won't fall on deaf ears: About 12 million people a year in the United States seek medical care for impacted or excessive earwax. Impaction, they say, can cause pain, pressure, itching, foul odor, ringing of the ears, ear discharge and, in extreme cases, hearing loss.

Good-for-you goo

So there's a reason for the goo. Earwax is a self-cleaning agent, with protective, lubricating and antibacterial properties, doctors say.

That's why tiny glands in the outer ear canal constantly pump out a watery substance, which gets mixed with bits of dead hair and skin and together is called earwax or cerumen. Excess earwax normally treks slowly out of the ear canal, with an extra boost from chewing and other jaw movements, carrying with it dirt, dust and other small particles from the ear canal. Then, dried-up clumps of the stuff fall out of the ear opening.

When this natural earwax train malfunctions, or when individuals poke around in their ears with cottons swabs or other foreign objects such as bobby pins or matchsticks, earwax can build up and block part of the ear canal.

"Then there are lots of people wearing earplugs for one reason or another, either because they've got hearing aids or they're transcriptionists at work or because they're addicted to their walkman," Roland told LiveScience, "and that can increase the likelihood that the wax doesn’t come out on its own."

Older adults are more prone to earwax buildup then younger individuals.

"The wax gets much thicker and drier, and plus you actually end up with more hair in your ear, when you're older, and so it traps it," Roland said.

He added, "Unfortunately, many people feel the need to manually 'remove' cerumen from the ears. This can result in further impaction and other complications to the ear canal." He said the saying, "Don't put anything smaller than your elbow in your ear," holds true.

Leave your ears alone

For the everyday individual, the new guidelines suggest you leave your ears alone unless you experience symptoms that you think are associated with too much earwax.

"If they're going to do something at home, they should probably use drops of some sort," Roland said. The panel found no evidence that one type of over-the-counter drops works better than another, or better than just plain sterile water or sterile saline, he said.

The drops help to loosen the earwax and then the ear often can do the rest, he added.

The guidelines also state that cotton-tipped swabs or other objects should not be used to remove earwax. Oral jet irrigators and the alternative medicine technique called ear candling are also strongly advised against.

Ear candling involves making a hollow tube from fabric and soaking that in warm beeswax, which is cooled and hardens. Once cooled and hardened, the beeswax cone is stuck into the ear. The outer end of the tube is lit and burns for about 15 minutes, a process that supposedly draws the wax out of the ear.

Studies have shown, however, that the drawn-out stuff is material from the candle itself. Doctors have also reported seeing patients who have burned the outer parts of their ears with this method.

If the drops don't relieve your symptoms, or if you dislike drops but still have symptoms, it's time to see a doctor, Roland said.

The panel found that three common techniques for earwax removal at the doctor's office work best, with no single method outshining the others. These include flushing the ear out with a water solution; manually removing the earwax under a microscope using medical instruments; and sending the patient home with ear drops.

While at the doctor's office, Roland urges patients not to be embarrassed by a little earwax.

"I get a lot of people in here who are horrified when I see a little wax in their ear, and then they start apologizing for being dirty and they're just very upset it's present at all," Roland said. "And I think the big message there is that it has a physiological function, and unless there's a reason to remove it, you should just leave it alone. It's OK."

Scientists find ancient lost settlements in Amazon

A vast region of the Amazon forest in Brazil was home to a complex of ancient towns in which about 50,000 people lived, according to scientists assisted by satellite images of the region.

The scientists, whose findings were published on Thursday in the journal Science, described clusters of towns and smaller villages connected by complex road networks and housing a society doomed by the arrival of Europeans five centuries ago.

European colonists and the diseases they brought with them probably killed most of the inhabitants, the researchers said. The settlements, consisting of networks of walled towns and smaller villages organized around a central plaza, are now almost entirely overgrown by the forest.

"These are not cities, but this is urbanism, built around towns," University of Florida anthropologist Mike Heckenberger said in a statement.

"If we look at your average medieval town or your average Greek polis, most are about the scale of those we find in this part of the Amazon. Only the ones we find are much more complicated in terms of their planning," Heckenberger added.

Helped by satellite imagery, the researchers spent more than a decade uncovering and mapping the lost communities.

Prior to the arrival of Europeans starting in 1492, the Americas were home to many prosperous and impressive societies and large cities. These findings add to the understanding of the various pre-Columbian civilizations.

The existence of the ancient settlements in the Upper Xingu region of the Amazon in north-central Brazil means what many experts had considered virgin tropical forests were in fact heavily affected by past human activity, the scientists said.

The U.S. and Brazilian scientists worked with a member of the Kuikuro, an indigenous Amazonian people descended from settlements' original inhabitants.

Original here