Wednesday, 27 October 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge


Space Telescope Listens In on Stellar Symphony

Posted: 26 Oct 2010 01:46 PM PDT

The Kepler Space Telescope doesn't just look for planets. By listening to subtle vibrations of the stars in its field of view, the telescope is recording a stellar symphony that gives an unprecedentedly accurate view of the inner lives of stars.

"We can say Kepler is listening to thousands of musicians in the sky," said Daniel Huber, a graduate student at the University of Sydney.

Kepler recorded thousands of red-giant stars humming in response to their internal rumblings. In this recording, which was scaled up to the range of human hearing, the deeper, louder tones correspond to larger stars.

Audio: Daniel Huber/KASC

Huber and members of an international consortium called the Kepler Astroseismic Science Consortium presented the new results in a teleconference Oct. 26. The Kepler chorus could help pin down the properties of planets, predict the future of our own sun and solve century-old stellar mysteries.

To search for planets, Kepler stares unblinkingly at a single patch of sky and waits for a star to slightly dim, a sign that a planet is crossing in front of the star. The telescope's sharp eyes are sensitive enough to detect stars' natural brightness variations, the result of vibrations inside the stars.

"Sound waves travel into the star and bring information up to the surface, which Kepler can see as a tiny flickering in brightness of the star," said astronomer Travis Metcalfe of The National Center for Atmospheric Research.

That flickering "has an underlying order like the notes of a musical instrument," he added. "We essentially measure the tone of these musical notes from the starlight."

In the same way that a cello sounds deeper than a violin, larger stars vibrate with lower frequency — or deeper tone — than smaller stars. These vibrations let astronomers measure the radius of a star to within a few percent.

 

The tones also reveal the stars' ages. Young stars burn brightly by converting hydrogen into helium and energy deep in their cores, but eventually the hydrogen reserves run out. Sound waves pass through dense helium cores more quickly than through hydrogen, changing the tone heard at the surface and giving a good sense of how long the star has been working as a hydrogen furnace.

Metcalfe presented a star with the uninspiring name KIC 11026764 as the most accurately characterized star in the universe, aside from the sun. The star is 5.94 billion years old, more than one billion years older than the sun, and 2.05 times the sun's radius. The measurements also show that this star isn't burning hydrogen fuel anymore — the core is almost entirely helium and is slowly contracting. Over the next several million years, the star will puff off its outer layers of gas until it becomes a bloated red-giant star.

This star does not host any planets, but the same techniques could be used to characterize stars that do. Knowing stars' sizes and ages could help pin down the sizes and ages of their planets.

"Our knowledge of the planets that Kepler discovers is only as good as our knowledge of the stars that they orbit," said Kepler co-investigator Natalie Batalha of San Jose State University in California.

Kepler also listened to the vibrations of more than a thousand red-giant stars ranging from a few to several dozen times bigger than the sun. Red giants are the endgame of stellar evolution. In about 6 billion years, the sun will evolve into a red giant as well.

"Kepler allows us to study the future life of our sun in much greater detail than ever before," Huber said.

Bigger red giants give off a lower, louder tone than smaller red giants, the study confirmed. Huber's results are published in two papers on arXiv.org.

The new observations may also help solve a stellar riddle that has puzzled astronomers for a hundred years. A class of stars called RR Lyrae variable stars can grow brighter or dimmer by a factor of two over just a few hours. Astronomers can measure how bright these stars actually are, as opposed to how bright they look from Earth, making them excellent "standard candles" to determine distances to other objects in the universe.

But some of these stars also show a weird modulation in their brightening and dimming, called the Blazhko effect. When this effect was discovered a century ago, it was thought to be rare and unusual.

The new Kepler data suggests that the effect "may be a rule rather than an exception," said astronomer Katrien Kolenberg of the Institute of Astronomy in Vienna, Austria.

Kepler observed the prime example of these shifty stars, known simply as RR Lyrae, plus 40 of its counterparts: "the most accurate and extensive measurement of these stars ever made," Kolenberg said. The observations showed a second variation in the stars' brightness that happens at ahlf the speed of the main variation, which Kolenberg believes is related to the mysterious Blazhko effect.

"It is striking that only a few months of uninterrupted Kepler data of the star RR Lyrae uncover phenomena that were never detected before, not even with a century of high-quality ground-based data," she said. "This is a dramatic overhaul in our understanding of RR Lyrae stars."

Because the Kepler Astroseismic Science Consortium is an international group, NASA, which operates the telescope, cannot give it funding. Last summer the consortium began raising research funds through an "Adopt a Star" program, in which anyone can claim a star as their own in Google Sky.

Image: Carter Roberts/Eastbay Astronomical Society.

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Shade of Red Preserved in Jurassic Fossils

Posted: 26 Oct 2010 10:28 AM PDT

Most biological colors of past geological ages are lost to time, existing only in the imagination's eye. But one algae's delicate reddish hue has survived intact, appearing in much the same tones as it did 150 million years ago.

Called Solenopora jurassica, the algae is responsible for fossils unearthed in Britain (where they're dubbed Beetroot Stones) and France. According to a new study, their coloration comes from natural pigments in the algae suffused by the element boron.

"It is quite exciting to find anything colorful from organisms that existed at a time when dinosaurs ruled the world," said Klaus Wolkenstein, a chemist at Austria's Johannes Kepler University and co-author of the new analysis, published October 26 in the Proceedings of the National Academy of Sciences.

Wolkenstein cautioned that fossilization may still have altered S. jurassica's pigmentation, changing its hue to something less than exactly original. But it's still close, and no other boron-containing biological pigments have ever been found, making S. jurassica's color truly unique.

Asked whether such pigmentation might be engineered into a modern algae, Wolkenstein preferred to look for it in nature. Perhaps similar pigments still exist in modern red algae and have just been overlooked — a 150 million-year-old color hidden in front of our eyes.

 

Liliocrinus, a Jurassic-era sea lily that's also maintained some of its original pigmentation.

Images: 1) Solenopora jurassica./Klaus Wolkenstein. 2) A Jurassic-era sea lily, its pigmentation also preserved for 150 million years./Klaus Wolkenstein.

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Citation: "Boron-containing organic pigments from a Jurassic red alga." By Klaus Wolkenstein, J├╝rgen H. Gross, and Heinz Falk. Proceedings of the National Academy of Sciences, Vol. 107 No. 43, October 26, 2010.

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Video: Fingerless Robotic Hand Can Pick Anything

Posted: 26 Oct 2010 07:52 AM PDT

A small bag filled with coffee grounds is lending robots a fingerless hand. The new kind of gripper, described online the week of October 25 in the Proceedings of the National Academy of Sciences, is capable of grasping all sorts of different objects with ease.

"This could be game-changing technology," says mechanical engineer Peko Hosoi of MIT, who was not involved with the new study. "The idea is so simple, yet effective and robust."

The simple gripper is made of a bag of coffee grounds and a vacuum, though other grains such as couscous and sand also work, says study coauthor Eric Brown of the University of Chicago. To pick something up, the bag of loose grounds first melds around the object. Then, as a vacuum sucks air out of the spaces between grains, the gripper stiffens, packing itself into a hard vice molded to the outline of the object. Reducing the bag's starting volume by just a teeny amount — less than 1 percent of the total — was enough to make the gripper latch on, the team found.

This transition from fluidlike behavior (such as dry sand flowing out of a bucket) to solid (a hard-packed sand castle) is a physical process called "jamming." Because the gripper's bulb conforms to any shape evenly before the vacuum jams it, it's extremely versatile. "Our goal was to pick up objects where you don't know what you're dealing with ahead of time," Brown says.

Gripper designs based on rigid metal fingers — like the classic arcade game with a claw that picks up toys — range from two-finger pincers to humanlike hands with five fingers and multiple joints. But all of these designs have to contend with complex finger positioning and forces. "This approach is totally different," says mechanical engineer Mark Yim of the University of Pennsylvania in Philadelphia. "It approaches grasping from a very different angle."

 

In experiments, the gripper started by picking up little things the researchers found lying around the lab: a pen, plastic tubing, a coffee mug, a shock absorber, a jack. The gripper held a cup of water well enough to pour, and a pen well enough to write. In a more daring feat, the gripper lifted a pair of water-filled gallon jugs tied together with a rope by wrapping itself around the handle of one and hoisting. And in one of the ultimate tests for robotic hands the gripper picked up a raw egg, a formidable task because hard metal pincers or fingers can concentrate force in a few small places, shattering the fragile shell.

"One of the tricky things about picking up delicate objects is that you have to know how much pressure to apply: too little and you drop the object; too much and you break it," Hosoi says. "This new gripper works by exactly conforming to the shape of the object so you can manipulate items with very little pressure — and without requiring feedback from sensors."

One kink in the design is that the gripper must apply pressure against an object in order to mold properly. If the gripper were to come at a mug handle from the side, it wouldn't be able to get a grip. Instead, it would scoot the mug along the table and over the edge. Brown says the design could be combined with a more traditional finger-based scaffold to provide more control.

Brown and his colleagues calculated that a similar gripper with a diameter of a meter would be powerful enough to lift an object weighing one metric ton. A scaled-up version might be helpful in search-and-rescue missions, Brown says. "You're posed with a problem of rubble of all sizes and shapes," so having a flexible gripper would be desirable.

Video: A robotic gripper made of a stretchy bag of coffee grounds and a vacuum picks up a shock absorber with ease. Vimeo.com/John Amend

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Signs of Destroyed Dark Matter Found in Milky Way’s Core

Posted: 26 Oct 2010 05:31 AM PDT

Cosmologists say they've found the most compelling evidence of dark matter particles to date, deep inside the Milky Way's core.

There, the thinking goes, the mysterious stuff is colliding to create gamma rays more frequently than anywhere else in the celestial neighborhood.

Similar studies have peppered scientific journals in recent years, but establishing the source definitively has been troublesome. That's not the case in this study, posted Oct. 13 on the preprint server arXiv.org, says Dan Hooper, its lead author and a cosmologist at both Fermilab in Illinois and the University of Chicago.

"We've considered every astronomical source and nothing we know of, except dark matter, can account for the observations," Hooper said. "No other explanation comes anywhere close."

The claim has yet to meet the full scrutiny of other scientists, but those who have read it said they'll be following discussions about the work closely.

"This is the first study I know of that pulls together a few threads of evidence for dark matter together with one simple particle model," said Craig Hogan, an astrophysicist at Fermilab who wasn't involved in the research. "It's not proven, but it's very exciting and deserves follow-up."

 

Dark matter got its start 13.7 billion years ago in a colossal expansion of energy called the Big Bang. That energy cooled down to form normal matter, dark matter and dark energy, which now make up 4 percent, 23 percent and 73 percent of the cosmos, respectively.

Like normal matter, dark matter has gravitational pull, helping to glue billions of stars together into galaxies. But it's called dark for a reason: The stuff hardly interacts with normal matter, making it invisible. Neutrinos are the only type of dark matter particles that have been detected in the laboratory, but they have almost zero mass and make up only a tiny fraction of dark matter's energy-of-the-universe slice.

The huge remaining portion, astrophysicists believe, is made up of weakly interactive massive particles, or WIMPs, some 10 to 1,000 times fatter in energy than a proton. If any two particles collide, the theory goes, they destroy one another and produce gamma rays.

Hooper and his team found such high-energy death knells in more than two years of data beamed back by the Fermi space telescope, NASA's gamma ray observatory that scans the Milky Way for high-energy action. What they found signaled the existence of colliding dark matter particles about eight to nine times heavier than protons — just outside the expected range.

"It's lighter than many of us would have guessed, but only by a little bit," Hooper said. "So far, we don't have any problems with that. The range is mostly sociological and not written in stone."

The team found the signals in data from a 100-light-year-wide zone of the core. They looked there, Hooper explained, because it's one of dark matter's favorite hangout spots and, in the Milky Way's case, the stuff is 100,000 times more concentrated than at the galaxy's outskirts. In short, the galaxy's core is a demolition derby for dark matter.

As tantalizing as the evidence may be, however, other scientists want to see Carl Sagan's bill of "extraordinary claims require extraordinary evidence" fulfilled before they climb on board. In simple terms, that means definitive evidence both in nature and in the laboratory.

"No one has produced Sagan-class evidence," said Michael Turner, a cosmologist at the University of Chicago who wasn't involved with the study. "The hardest part to accepting this is that you have to exclude astrophysical explanations, and nature is very, very clever. It could be something we just haven't thought of yet."

The good news, says Turner, is that several promising dark-matter detection experiments are underway. In particular, deep-underground detectors like CoGeNT, which may have seen signs of WIMPs in recent years, could lend Hooper a hand.

"This decade is the decade of dark matter. The problem is ripe to solve," Turner said. "We've gotten to this point where all of these detectors are looking in the right places."

Hooper agrees on both counts, but says no astrophysicist he spoke with could explain the phenomenon. As for verifying dark matter's existence in the laboratory, he suspects it's only a matter of weeks before his findings are backed up or trounced.

"I haven't been this excited about being a cosmologist ever before," Hooper said.

Image: A gamma-ray map of the Milky Way recorded over the course of 3 months. NASA/DOE/Fermi LAT Collaboration (high-res version)

Via: symmetry breaking

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