Spider Tension Turns Caustic

This fishing spider (Dolomedes tenebrosus) was captured along the surface of a northern Ontario lake while I was on my own fishing expedition in June of 2006. Note how the approximately one-half-inch (13 mm) spider uses surface tension to walk on water. Two if its eight legs have actually broken through the surface of the water. The dimpling of the water surface appears out of focus, but it's actually the concavemeniscus of the surface making it appear that way. The pink granite beneath the water made a nice background to photograph both this unique predator and the refraction of sunlight below it. What appears to be a shadowy reflection is caused by the meniscus at the surface bending the light and focusing it away from the area at those points under the spider. The chromatic edges (bright outline) of these dark areas delineate the caustic surface.

Dolomedes spiders are covered with unwettable (hydrophobic), short, velvety hairs. This allows them to use surface tension to stand or run on the water, like pond skaters. When these spiders move beneath the water, air becomes trapped in the body hairs. This forms a thin film over the whole surface of the body and legs, giving them the appearance of fine polished silver. Like other spiders, Dolomedes breathe with both lungs, which are found beneath their abdomens. Their lungs open into the air film, allowing the spiders to breathe while submerged. The trapped air makes them very buoyant. So if they let go of a rock or a plant stem they're holding on to, they float toward the surface where they pop onto the surface, completely dry. It's quite an amazing adaptation for an aquatic existence. 

Photo details: Camera Maker: NIKON; Camera Model: E995; Focal Length: 31.0mm; Aperture: f/5.8; Exposure Time: 0.0043 s (1/234); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); Flash Fired: No; Orientation: Normal; Color Space: sRGB; Software: E995v1.

Source: http://epod.usra.edu/blog/2012/01/spider-tension-turns-caustic.html

World's Most Powerful Laser Unlocks Clues to Extreme Matter in Stars & Giant Planets

Researchers working at the SLAC National Accelerator Laboratory have used the world's most powerful X-ray laser to create and probe a two-million-degree piece of matter in a controlled way for the first time. This feat takes scientists a significant step forward in understanding the most extreme matter found in the hearts of stars and gas giant exo planets, and could help experiments aimed at recreating the nuclear fusion process that powers the sun.

The experiments were carried out at SLAC's Linac Coherent Light Source (LCLS), whose rapid-fire laser pulses are a billion times brighter than those of any X-ray source before it. Scientists used those pulses to flash-heat a tiny piece of aluminum foil, creating what is known as "hot dense matter," and took the temperature of this solid plasma—about 2 million degrees Celsius. The whole process took less than a trillionth of a second.

"The LCLS X-ray laser is a truly remarkable machine," said Sam Vinko, a postdoctoral researcher at Oxford University and the paper's lead author. "Making extremely hot, dense matter is important scientifically if we are ultimately to understand the conditions that exist inside stars and at the center of giant planets within our own solar system and beyond." 

Scientists have long been able to create plasma from gases and study it with conventional lasers, said co-author Bob Nagler of SLAC, an LCLS instrument scientist. But no tools were available for doing the same at solid densities that cannot be penetrated by conventional laser beams."The LCLS, with its ultra-short wavelengths of X-ray laser light, is the first that can penetrate a dense solid and create a uniform patch of plasma—in this case a cube one-thousandth of a centimeter on a side—and probe it at the same time," Nagler said.

The resulting measurements, he said, will feed back into theories and computer simulations of how hot, dense matter behaves. This could help scientists analyze and recreate the nuclear fusion process that powers the sun.

"Those 60 hours when we first aimed the LCLS at a solid were the most exciting 60 hours of my entire scientific career," said Justin Wark, leader of the Oxford group. "LCLS is really going to revolutionize the field, in my view."

The image at top of page shows the interior of a Linac Coherent Light Source SXR experimental chamber, set up for an investigation to create and measure a form of extreme, 2-million-degree matter known as “hot, dense matter.” The central part of the frame contains the holder for the material that will be converted by the powerful LCLS laser into hot, dense matter. To the left is an XUV spectrometer and to the right is a small red laser set up for alignment and positioning. 

Source: http://www.dailygalaxy.com/my_weblog/2012/01/worlds-most-powerful-laser-unlocks-clues-to-extreme-matter-in-stars-giant-planets.html

NASA Study Solves Case of Earth's 'Missing Energy'

Clouds play a vital role in Earth's energy balance, cooling or warming Earth's surface depending on their type. This painting, "Cumulus Congestus," by JPL's Graeme Stephens, principal investigator of NASA's CloudSat mission, depicts cumulus clouds, which transport energy away from Earth's surface. See more at http://cloudsat.atmos.colostate.edu . Image credit: Graeme Stephens

Two years ago, scientists at the National Center for Atmospheric Research in Boulder, Colo., released a study claiming that inconsistencies between satellite observations of Earth's heat and measurements of ocean heating amounted to evidence of "missing energy" in the planet's system. 

Where was it going? Or, they wondered, was something wrong with the way researchers tracked energy as it was absorbed from the sun and emitted back into space? 

An international team of atmospheric scientists and oceanographers, led by Norman Loeb of NASA's Langley Research Center in Hampton, Va., and including Graeme Stephens of NASA's Jet Propulsion Laboratory in Pasadena, Calif., set out to investigate the mystery. 

They used 10 years of data -- spanning 2001 to 2010 -- from NASA Langley's orbiting Clouds and the Earth's Radiant Energy System Experiment (CERES) instruments to measure changes in the net radiation balance at the top of Earth's atmosphere. The CERES data were then combined with estimates of the heat content of Earth's ocean from three independent ocean-sensor sources. 

Their analysis, summarized in a NASA-led study published Jan. 22 in the journal Nature Geosciences, found that the satellite and ocean measurements are, in fact, in broad agreement once observational uncertainties are factored in. 

"One of the things we wanted to do was a more rigorous analysis of the uncertainties," Loeb said. "When we did that, we found the conclusion of missing energy in the system isn't really supported by the data." 

"Missing Energy" is in the Ocean 

"Our data show that Earth has been accumulating heat in the ocean at a rate of half a watt per square meter (10.8 square feet), with no sign of a decline," Loeb said. "This extra energy will eventually find its way back into the atmosphere and increase temperatures on Earth." 

Scientists generally agree that 90 percent of the excess heat associated with increases in greenhouse gas concentrations gets stored in Earth's ocean. If released back into the atmosphere, a half-watt per square meter accumulation of heat could increase global temperatures by 0.3 or more degrees centigrade (0.54 degree Fahrenheit). 

Loeb said the findings demonstrate the importance of using multiple measuring systems over time, and illustrate the need for continuous improvement in the way Earth's energy flows are measured. 

The science team at the National Center for Atmospheric Research measured inconsistencies from 2004 and 2009 between satellite observations of Earth's heat balance and measurements of the rate of upper ocean heating from temperatures in the upper 700 meters (2,300 feet) of the ocean. They said the inconsistencies were evidence of "missing energy." 

Other authors of the paper are from the University of Hawaii, the Pacific Marine Environmental Laboratory in Seattle, the University of Reading United Kingdom and the University of Miami. 

Source: http://www.jpl.nasa.gov/news/news.cfm?release=2012-029&cid=release_2012-029

NASA's NuSTAR Ships to Vandenberg for March 14 Launch

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, mission is seen here being lowered into its shipping container at Orbital Sciences Corporation in Dulles, Va. The spacecraft is headed to Vandenberg Air Force Base in Central California, where it will be mated to its rocket. It is scheduled to launch from Kwajalein Atoll in the Marshall Islands on March 14. Image credit: NASA/JPL-Caltech/Orbital

NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, shipped to Vandenberg Air Force Base, Calif., on Tuesday, to be mated to its Pegasus launch vehicle. The observatory will detect X-rays from objects ranging from our sun to giant black holes billions of light-years away. It is scheduled to launch March 14 from an aircraft operating out of Kwajalein Atoll in the Marshall Islands. 

"The NuSTAR mission is unique because it will be the first NASA mission to focus X-rays in the high-energy range, creating the most detailed images ever taken in this slice of the electromagnetic spectrum," said Fiona Harrison, the mission's principal investigator at the California Institute of Technology in Pasadena, Calif. 

The observatory shipped from Orbital Sciences Corporation in Dulles, Va., where the spacecraft and science instrument were integrated. It is scheduled to arrive at Vandenberg on Jan. 27, where it will be mated to the Pegasus, also built by Orbital, on Feb. 17. 

The mission will be launched from the L-1011 "Stargazer" aircraft, which will take off near the equator from Kwajalein Atoll in the Pacific. NuSTAR and its Pegasus will fly from Vandenberg to Kwajalein attached to the underside of the L-1011, and are scheduled to arrive on March 7. 

On launch day, after the airplane arrives at the planned drop site over the ocean, the Pegaus will drop from the L-1011 and carry NuSTAR to an orbit around Earth. 

"NuSTAR is an engineering achievement, incorporating state-of-the-art high-energy X-ray mirrors and detectors that will enable years of astronomical discovery," said Yunjin Kim, the mission's project manager at NASA's Jet Propulsion Laboratory in Pasadena. 

NuSTAR's advanced telescope consists of two sets of 133 concentric shells of mirrors, which were shaped from flexible glass similar to that found in laptop screens. Because X-rays require large focusing distances, or focal lengths, the telescope has a lengthy 33-foot (10-meter) mast, which will unfold a week after launch. 

These and other advances in technology will enable NuSTAR to explore the cosmic world of high-energy X-rays with much improved sensitivity and resolution over previous missions. During its two-year primary mission, NuSTAR will map the celestial sky in X-rays, surveying black holes, mapping supernova remnants, and studying particle jets travelling away from black holes near the speed of light. 

NuSTAR also will probe the sun, looking for microflares theorized to be on the surface that could explain how the sun's million-degree corona, or atmosphere, is heated. It will even test a theory of dark matter, the mysterious substance making up about one-quarter of our universe, by searching the sun for evidence of a hypothesized dark matter particle. 

"NuSTAR will provide an unprecedented capability to discover and study some of the most exotic objects in the universe, from the corpses of exploded stars in the Milky Way to supermassive black holes residing in the hearts of distant galaxies," said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington. 

NuSTAR is a small-explorer mission managed by JPL for NASA's Science Mission Directorate. The spacecraft was built by Orbital Sciences Corporation. Its instrument was built by a consortium including Caltech, JPL, Columbia University, New York, N.Y., NASA's Goddard Space Flight Center in Greenbelt, Md., the Danish Technical University in Denmark, the University of California, Berkeley, and ATK-Goleta. NuSTAR will be operated by U.C. Berkeley, with the Italian Space Agency providing its equatorial ground station located at Malindi, Kenya. NASA's Explorer Program is managed by Goddard. JPL is managed by Caltech for NASA. 

For more information, visit http://www.nasa.gov/nustar and http://www.nustar.caltech.edu/.

Source: http://www.jpl.nasa.gov/news/news.cfm?release=2012-023&cid=release_2012-023

A Guide to the Dark Side

Now you see it. Bright areas denote the regions where dark matter has gathered into filaments and clumps. Credit: L. Van Waerbeke, C. Heymans, and CFHT Lens collaboration

AUSTIN, TEXAS-Astronomers have made the largest map yet of dark matter in the universe. This invisible stuff gives off no light, but it does exert gravity on its surroundings. It probably consists of unknown elementary particles, and it's much more prevalent than the normal matter from which stars, planets, and people are made.

The new map shows that dark matter is concentrated in huge clumps and filaments, with giant, empty regions in between—just as computer simulations had predicted. "We're very happy to see that our results are similar to what we expected," says astrophysicist Ludovic Van Waerbeke of the University of British Columbia, Vancouver, in Canada.

Mapping the invisible may sound impossible, but in fact it's rather simple. Just as an invisible man sleeping in your bed will leave wrinkles in the sheets, the gravity of invisible dark matter produces minute distortions in the observed shapes of background galaxies. Using this "weak lensing" effect to map dark matter is "a first important step to understand the dark Universe," says Van Waerbeke's co-worker Catherine Heymans of the University of Edinburgh in the United Kingdom.

Working with the 340-megapixel MegaCam camera on the 3.6-meter Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii, the team spent 5 years imaging 10 million galaxies at distances of about 6 billion light-years. "Our map is about a hundred times larger than the largest dark matter map to date," Van Waerbeke says. A statistical analysis of the shapes of the galaxies revealed the spatial distribution of the intervening dark matter.

The results, presented here at the 219th meeting of the American Astronomical Society, look very much like supercomputer simulations of the evolution of the universe, with dark matter clumped into a "cosmic web" of filaments and knots. The clumpy knots, where most of the dark matter is concentrated, neatly coincide with huge clusters of galaxies, just as cosmological theories suggest.

In fact, says astrophysicist Rachel Mandelbaum of Princeton University, "projects like the CFHT Lensing Survey can be used to test theories of dark matter and general relativity." So far, Van Waerbeke says, "everything looks okay. The maps show exactly what we expected." In other words, the results confirm current popular ideas about the physics, makeup, and evolution of the universe.

According to team member Fergus Simpson of the University of Edinburgh, the lensing survey shows not only how dark matter bends light but also how it clumps together over time. The results, he says, already rule out a number of suggested alternatives to Einstein's general theory of relativity. For instance, Simpson says, a theory known as Modified Newtonian Dynamics is no longer supported by the dark matter data.

Whereas lensing surveys reveal the distribution of dark matter, other types of observations planned for the near future by other projects will shed light on the even more mysterious dark energy that appears to accelerate the expansion of the universe, Heymans explains. A future European space telescope called Euclid will carry out these two types of observations simultaneously, she says. "We really need both."

Source: http://news.sciencemag.org/sciencenow/2012/01/a-guide-to-the-dark-side.html?rss=1