Wednesday 19 January 2011

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

Amateurs Find Hidden Gems in Space Photo Contest

Posted: 19 Jan 2011 08:08 AM PST

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Last October, the European Southern Observatory — a bottomless reservoir of mind-blowing space photos — issued a challenge to amateur astronomers everywhere: Find the best photos their professional image processors overlooked.

Now, the results are in. The ESO announced the best astrophotos dug from their archives in the "Hidden Treasures" competition.

Contestants had to start with raw, grayscale data taken with one of the observatory's constellation of telescopes, which includes the Very Large Telescope (actually four separate telescopes working together), VISTA, APEX, the La Silla Paranal Observatory, and ALMA. After correcting the image for distortions and unwanted signatures of the telescope, contestants could process or enhance the raw data however they wanted, short of painting directly on the image.

ESO got about 80 submissions, and selected 10 winners based on the "quality of the data processing, the originality of the image and the overall aesthetic feel." The grand prize winner, Russian astrophotographer Igor Chekalin, will get a free trip to the Paranal Observatory in Chile and a chance to participate in an observing run.

You can sift through the whole set of photos on flickr. Here are some of our favorites.

Orion Nebula

The watercolor-like portrait (above) of the Orion Nebula was processed by Russian astrophotographer Igor Chekalin. The image was captured in early January 2005 with the Wide Field Imager camera on the 2.2-meter telescope at the La Silla Observatory in Chile. The nebula gives astronomers a close-up view of a stellar nursery, where stars are born from condensing clouds of dust and gas.

ESO has also released their own reprocessed version of the same data (below).

Images: ESO/Igor Chekalin.

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New Study Finds No Sign of ‘First Habitable Exoplanet’

Posted: 18 Jan 2011 11:54 AM PST

Things don't look good for Gliese 581g, the first planet found orbiting in the habitable zone of another star. The first official challenge to the small, hospitable world looks in the exact same data — and finds no significant sign of the planet.

"For the time being, the world does not have data that's good enough to claim the planet," said astro-statistics expert Philip Gregoryof the University of British Columbia, author of the new study.

The "first habitable exoplanet" already has a checkered history. When it was announced last September, Gliese 581g was heralded as the first known planet that could harbor alien life. The planet orbits its dim parent star once every 36.6 days, placing it smack in the middle of the star's habitable zone, the not-too-hot, not-too-cold region where liquid water could be stable.

Planet G was the sixth planet found circling Gliese 581, a red dwarf star 20 light-years from Earth. A team of astronomers from the Geneva Observatory in Switzerland found the first four planets using the HARPS spectrograph on a telescope in Chile. The team carefully measured the star's subtle wobbles as the planets tugged it back and forth.

Two more planets, including the supposedly habitable 581g, appeared when astronomers Steve Vogt of the University of California, Santa Cruz and Paul Butler of the Carnegie Institution of Washington added data from the HIRES spectrograph on the Keck Telescope in Hawaii. They announced their discovery Sept. 29.

Just two weeks later, the HARPS team announced they found no trace of the planet in their data, even when they added two more years' worth of observations. But it was still possible that the planet was only visible using both sets of data.

Now, the first re-analysis of the combined data from both telescopes is out, and the planet is still missing.

 

"I don't find anything," Gregory said. "My analysis does not want to lock on to anything around 36 days. I find there's just no feature there."

Unlike earlier studies, Gregory used a branch of statistics called Bayesian analysis. Classical methods are narrow, testing only a single hypothesis, but Bayesian methods can evaluate a whole set of scenarios and figure out which is the most likely.

Gregory wrote a program that analyzed the likelihood that a given planetary configuration would produce the observed astronomical data, then ran it for various possible configurations.

For the HARPS data set, he found that the best solution was a star with five planets, which orbit the star once every three, five, 13, 67 and 400 days. The 36-day habitable world wasn't there.

When he looked at the HIRES and the combined data sets, the best solution was a star with two planets. Only when he included an extra term in the HIRES data did Gregory find more, which he suspects means the HIRES instrument isn't as accurate as thought.

"There may be something in the telescope…that's contributing to the error," he said.

Gregory's model finds the probability that the six-planet model is a false alarm is 99.9978 percent. None of the planets Gregory's analysis turned up are in the habitable zone. The results are in a paper submitted to the Monthly Notices of the Royal Astronomical Society and published on the physics preprint website arxiv.org.

Other astronomers seem impressed with Gregory's analysis.

"That's the right way to do it," said exoplanet expert Daniel Frabrycky of the University of California, Santa Cruz. "I think everyone would agree that that is the most sophisticated analysis that you can do, and as much as you could hope to do."

"The Gregory paper is by far the most complete statistical analysis to date that has been made public," said exoplanet and astro-statistics expert Eric Ford of the University of Florida. "It's by far the most rigorous analysis."

But most astronomers are not yet ready to close the book on Gliese 581g.

"I'm not going to admit that it's a dead planet yet," said exoplanet expert Sara Seager of MIT. "No one will be able to sort this out today … it will take some time."

Vogt still firmly believes the planet is there. "I'm standing by our data," he told Wired.com.

He said there are two ways to interpret the signals from Gliese 581. Sometimes a single planet with an elongated, or elliptical orbit can look the same as two planets that trace perfect circles around their stars. One of Gliese 581's planets, planet D, could be one of these "eccentric impostors," hiding an extra planet within its signal.

Part of the reason it's so difficult to tell these two scenarios apart is that spotty observations make fake signals in the data. These signals, which show up because the telescope can't watch the star continuously, look like they could actually be planets, but they would disappear if we could observe round the clock.

In a paper that's still in preparation, astronomer Guillem Anglada-Escudé and Harvard graduate student Rebekah Dawson tackle these issues, and conclude that the habitable planet still has a chance. "With the data we have, the most likely explanation is that this planet is still there," Anglada-Escudé said.

Everyone agrees that the problem can only be resolved with more data. In particular, astronomers are anxious to see the extra data that the HARPS group used to conclude Gliese 581g is a mirage.

"I don't think anything will change significantly until the Swiss publish their data," Anglada-Escudé said. "Nobody else has seen their data. We're waiting to see that, just to settle down the problem."

Image: Lynette Cook

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Lasers Control Nematode Worms Like Robots

Posted: 18 Jan 2011 08:33 AM PST

 

Satirist Stephen Colbert envisions his "Colbert Nation" mentally marching in lockstep with his special brand of patriotism. But scientists have done him one better, by creating tiny worm-bots completely under their control.

Rather than comedic persuasion, these scientists are using a dot of laser light. With it they can make a worm turn left, freeze or lay an egg. The researchers report their work online Jan. 16 in Nature Methods.

The new system, named CoLBeRT for "Controlling Locomotion and Behavior in Real Time," doesn't just create a mindless zombie-worm, though. It gives scientists the ability to pick apart complicated behaviors on a cell-by-cell basis.

"This system is really remarkable," says biological physicist William Ryu of the University of Toronto, who was not involved in the research. "It's a very important advance in pursuit of the goal of understanding behavior."'

 

Transparent and small, the nematode Caenorhabditis elegans is particularly amenable to light-based mind control. Another benefit of the worm is that researchers know the precise location of all 302 of its nerve cells. But until now, there wasn't a good way to study each cell by itself, especially in a wriggling animal.

"This tool allows us to go in and poke and prod at those neurons in an animal as it's moving, and see exactly what each neuron does," says study co-author Andrew Leifer of Harvard University.

The system is based on the emerging field of optogenetics, in which light is used to turn cells on or off. Leifer and his colleagues genetically engineered light-responsive molecules into particular groups of cells in the worm.

Then, a computer program that the team developed figures out where in the microscope's field of view a target cell is. Once the cell is pinpointed, the program directs lasers so that a tiny beam of light hits the cell.

"When we're shining light on a neuron, we're hitting that neuron and nothing else," Leifer says.

The whole process, from finding the cell to light hitting its target, takes about 20 milliseconds. As the worm's position changes, that information is fed back into the computer program, and the laser is adjusted. If the worm crawls too far, a motorized microscope stage brings the animal back.

One of the biggest benefits of the new method, Ryu says, is that it works in a roving animal. "The worms are not held down in any way — they're freely moving. There aren't many systems where you can look at such truly free organisms."

In early tests of their technique, Leifer and his team forced worms to freeze, change directions, turn left or right, and even lay eggs. In later tests, the team focused on two nerve cells that help the worm respond to touch. Researchers knew that a gentle tickle on the head causes worms to move backward, but after too many touches, the worms grow desensitized and stop responding. By mimicking touches with light, the researchers found that a weary cell that's been touched too many times can also tire out its partner cell that hasn't been touched, suggesting that these cells don't act alone.

Another group of scientists, led by Jeffrey Stirman of Georgia Tech in Atlanta, reports a similar technique for worm mind-control, also online Jan. 16 in Nature Methods. Ryu says the two methods are similar. The CoLBeRT method appears to be a little faster, he says, but if the worm is crawling slowly, the method used by Stirman's group may offer more precise laser targeting. "Do both papers contribute to understanding behavior at a holistic level? Yes, definitely."

Neuroengineer Ed Boyden of MIT says the new work could allow scientists to figure out how every cell in an animal works together to generate a behavior. "The ability to target a single cell is really important, because it allows you to understand precisely what each of these cells does."

Video: A burst of laser light from Leifer's device shuts down nerves responsible for motion in a nematode, momentarily paralyzing a worm./Vimeo/Samuel Lab

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2,550-Year-Old Celtic Beer Recipe Resurrected

Posted: 17 Jan 2011 06:20 PM PST

Early Celtic rulers of a community in what's now southwestern Germany liked to party, staging elaborate feasts in a ceremonial center. The business side of their revelries was located in a nearby brewery capable of turning out large quantities of a beer with a dark, smoky, slightly sour taste, new evidence suggests.

Six specially constructed ditches previously excavated at Eberdingen-Hochdorf a 2,550-year-old Celtic settlement, were used to make high-quality barley malt, a key beer ingredient, says archaeobotanist Hans-Peter Stika of the University of Hohenheim in Stuttgart. Thousands of charred barley grains unearthed in the ditches about a decade ago came from a large malt-making enterprise, Stika reports in a paper published online Jan. 4 in Archaeological and Anthropological Sciences.

Stika bases that conclusion on a close resemblance of the ancient grains to barley malt that he made by reproducing several methods that Iron Age folk might have used. He also compared the ancient grains to malt produced in modern facilities. Upon confirming the presence of malt at the Celtic site, Stika reconstructed malt-making techniques there to determine how they must have affected beer taste.

 

The oldest known beer residue and brewing facilities date to 5,500 years ago in the Middle East, but archaeological clues to beer's history are rare (Science News: Oct, 2, 2004, p. 216).

At the Celtic site, barley was soaked in the specially constructed ditches until it sprouted, Stika proposes. Grains were then dried by lighting fires at the ends of the ditches, giving the malt a smoky taste and a darkened color. Lactic acid bacteria stimulated by slow drying of soaked grains, a well-known phenomenon, added sourness to the brew.

Unlike modern beers that are flavored with flowers of the hop plant, the Eberdingen-Hochdorf brew probably contained spices such as mugwort, carrot seeds or henbane, in Stika's opinion. Beer makers are known to have used these additives by medieval times. Excavations at the Celtic site have yielded a few seeds of henbane, a plant that also makes beer more intoxicating.

"These additives gave Celtic beer a completely different taste than what we're used to today," Stika says.

Heated stones placed in liquefied malt during the brewing process — a common practice later in Europe — would have added a caramelized flavor to this fermented Celtic drink, he adds. So far, no fire-cracked stones have been found at Eberdingen-Hochdorf but they may have been used to heat pulpy malt slowly, a practice documented at later brewing sites, Stika says. He suspects that fermentation was triggered by using yeast-coated brewing equipment or by adding honey or fruit, which both contain wild yeasts.

Celts consisted of Iron Age tribes, loosely tied by language and culture, that inhabited much of Western Europe from about the 11th to the first century B.C.

In the same report Stika describes another tidbit for fans of malt-beverage history: A burned medieval structure from the 14th century A.D., recently unearthed in Berlin during a construction project, contains enough barley malt to have brewed 500 liters of beer, the equivalent of nearly 60 cases.

Classics professor Max Nelson of the University of Windsor in Canada, an authority on ancient beer, largely agrees with Stika's conclusions. Malt-making occurred at Eberdingen-Hochsdorf, and malt was probably stored in the medieval Berlin building, Nelson says.

Other stages of brewing occurred either at these sites, as suggested by Stika, or nearby, in Nelson's view.

"Stika's experiments go a long way toward showing how precisely barley was malted in ancient times," he remarks.

Beer buffs today would regard Celtic beer as a strange brew not only for its flavor but because it would have been cloudy, contained yeasty sediment and been imbibed at room temperature, Nelson notes.

Stika's insights into the range of techniques and ingredients available to Celtic beer makers should inspire modern "extreme brewers" to try out the recipe that he describes, says anthropologist Bettina Arnold of the University of Wisconsin–Milwaukee.

Perhaps they'll find out whether Roman emperor Julian, in a 1,600-year-old poem, correctly described Celtic beer as smelling "like a billy goat."

Image: Charred barley grains from an Iron Age Celtic settlement, such as these, inspired experiments to determine that they had been malted as part of a brewing operation that produced beer with a smoky and somewhat sour taste./H.-P. Stika

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