Astronomy
A Challenge In Visual Athletics: Hunting The Gegenschein
Looking for something truly elusive? Astronomy has no shortage of the fleeting and ephemeral when it comes to challenges. This week’s challenge will require supremely dark skies and persistence.
We’re talking about the gegenschein, the elusive counter glow lying opposite to the Sun across the plane of the ecliptic. We bring this up now, as the Moon heads towards New phase on February 8th and we still enjoy long nights for northern hemisphere observers prior to the equinox and the return to daylight saving time next month.
The gegenschein (meaning ‘counter-glow’ in German) was first noted by Espirit Pezenas in 1730. The exact pronunciation is (gey-gun-SHINE). The ghostly glow is caused by a retro-reflector phenomenon known as the Seeliger effect, which results in by sunlight glinting off of dust particles scattered along the plane of the ecliptic. The same phenomena can be seen sunward in the dawn or dusk sky concentrated as a pyramid-shaped glow jutting up from the horizon known as the zodiacal light.
Though dust is scattered all along the solar ecliptic, it’s slightly brighter in the anti-sunward direction because particles there are far beyond the cone of the Earth’s shadow as it extends back into space and at 100% illumination, like millions of tiny little ‘Full Moons’. You can see a very similar counter-glow phenomena known as a ‘glory’ or heiligenschein dancing along the cloud tops from a plane, or on grass covered with dew.
Rapidly Spinning Stars Explain Dark Matter Signal From Galactic Center
The puzzling excess of gamma rays from the center of the Milky Way probably originates from rapidly rotating neutron stars, or millisecond pulsars, and not from dark matter annihilation, as previously claimed. This is the conclusion of new data analyses by two independent research teams from the University of Amsterdam (UvA), Netherlands, and Princeton University/Massachusetts Institute of Technology (MIT).
In 2009, observations with the Fermi Large Area Telescope revealed an excess of high-energy photons, or gamma rays, at the center of our galaxy. It was long speculated that this gamma ray excess could be a signal of dark matter annihilation. If true, it would constitute a breakthrough in fundamental physics and a major step forward in our understanding of the matter constituents of the universe.
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Millisecond pulsars
New statistical analyses of the Fermi data by Christoph Weniger from UvA and a research group from Princeton/MIT now strongly suggest that the excess emission does indeed originate from unresolved point sources. The best candidates are millisecond pulsars, the researchers conclude.
Millisecond pulsars, or rapidly rotating neutron stars, were often formed billions of years ago. They are among the most extreme objects in the galaxy. A population of hundreds or thousands of these millisecond pulsars must be lurking in the galactic center, hidden from detection due to present day instrument sensitivity. Future radio surveys with existing and upcoming telescopes — e.g., Green Bank Telescope, Square Kilometre Array — will be able to further test this hypothesis in the coming years.
Biology
Why Some Birds Sing Elaborate Songs In The Winter
Male birds’ puzzling off-season singing in winter could be practice for flirting in spring.
Europe’s great reed warblers (Acrocephalus arundinaceus) and some other male long-distance migrants sing extensively when overwintering in sub-Saharan Africa, says Marjorie Sorensen, now at Goethe University in Frankfurt. “Why are they doing this when they’re thousands of kilometers from any possible breeding opportunity?”
Singing seems costly. Reed warbler songs — “very harsh-sounding and creaking,” Sorensen says — are changeable compositions made up from a male’s repertoire of some 40 to 60 sounds. Tests find that singing demands about 50 percent more energy than reed warblers spend resting. Plus, singing cuts into foraging time and risks catching predator attention.
Biologists largely expected the wintertime musical extravagance to be territory defense. But the birds creak variations of courtship serenades instead of shorter territorial anthems, Sorensen and her colleagues report in the March American Naturalist. And instead of squabbling over their patches, the warblers freely crisscross the landscape. Nor did testosterone elevation left over from the previous breeding season play a role — levels had dropped to winter lows.
As an alternative explanation, Sorensen and colleagues suggest that wintertime song is practice. Female reed warblers prefer males that deliver more complex songs. And among bird species overwintering in Africa, those that sang the most were also likely to show signs of strong evolutionary pressure on musical courtship. Their songs were especially complex, but their plumage didn’t show much difference between the sexes. When music matters so much, practice could, too.
Major Storm Events Play Key Role In Biogeochemistry Of Watersheds
A new Yale-led study offers a new conceptual framework for understanding the biogeochemistry of watersheds. The framework combines hydrologic and biogeochemical theory to test well established concepts in watershed ecology.
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This phenomenon can have profound ecological implications on the quality of water systems worldwide and the chemical processes that occur within them. Dissolved organic matter — a complex mix of compounds that leeches into waterways and gives rivers and streams their color — introduces nutrients and pollutants, influences the escape of carbon dioxide from the water, and can impact the amount of light that penetrates the water. That, in turn, can affect levels of phytoplankton, a major food source for many organisms.
Researchers have long believed that organic materials are naturally processed by organisms in the “first order” streams — the smaller streams at the headwaters of a river network headstream waters — creating new compounds that are in turn processed by organisms farther downstream, with the process occurring throughout the system. The process is known as the River Continuum Concept.
But the new paper underscores that this process does not account for the importance of heavy weather events, which trigger “pulses” of organic matter into waterways. As the authors explain, these events also push, or “shunt,” this organic matter past the headwaters before there is time for those reactions to occur since they also accelerate the velocity of the water flow.
Chemistry
How Chemistry Is Helping Defeat Fuel Fraud
In October 2015, Roland Gurney, 33, and his brother Stephen Gurney, 28, were convicted of laundering fuel in Northern Ireland.
They had used a bleaching agent to strip red marker dye from 4,500 L of subsidized diesel designated for agricultural, construction, and heating use. The brothers were found to be selling the laundered fuel on the open market. They were also found in possession of 1,200 L of toxic waste resulting from their fuel-laundering activities.
U.K. authorities say many more fuel fraudsters like the Gurneys are slipping through their hands. This is because once the dyes have been removed, laundered fuel cannot easily be identified. Fraudsters around the world typically remove dyes, such as the azo dye Solvent Red 26, by passing the fuel through an absorbent, such as activated carbon, or by washing the fuel with an acid or caustic soda.
To help governments curb fuel fraud, a handful of companies are introducing technologies that make it possible to identify laundered fuels. Innovations include a hydrocarbon molecule developed by Dow Chemical and a novel detection technology invented by a former U.K. chemistry professor.
Fuel fraud costs governments around the world about $100 billion annually, according to Addison, Texas-based Authentix, a provider of fuel-marking programs. The problem is particularly acute in Northern Ireland, where 8% of all fuels and 12–13% of diesel is illicit. The country loses about $1 billion in tax revenue annually as thieves resell laundered fuel for more than twice the subsidized or tax-free price of fuel still containing dye.
Maintaining Marble Monuments
‘Set in stone’ describes something permanent or difficult to change. However, in regions of polluted air, this begins to lose meaning. Sulfur and nitrogen oxides produce acid rain, which dissolves calcite in limestone and marble monuments, and leads to their degradation.
To tackle this problem, scientists lead by Massimiliano Arca at the University of Cagliari, have synthesised a promising protective agent for calcerous stone. Calcium carbonate reacts with oxamate ions to produce a calcium oxalate salt. To allow appreciable salt formation on marble and limestone surfaces, the team increased the oxamate ions’ solubility by adding a phenyl group and creating ammonium N-phenyloxamate. After immersion in the ionic solution, FT-NIR spectra and SEM microscopy uncovered an invisible, low solubility, crystalline calcium phenyloxalate coating. With no visible colour change and a thickness of up to 15µm, this salt is an ideal candidate to prevent weathering and retain the appearance of stone monuments.
Ecology
Loss Of Wild Flowers Matches Pollinator Decline
The first Britain-wide assessment of the value of wild flowers as food for pollinators shows that decreasing resources mirror the decline of pollinating insects.
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It reports substantial losses to nectar resources in England and Wales between the 1930s and 1970s – a period closely linked with agricultural intensification.
By 1978, the researchers discovered that nectar resources had stabilised and actually increased from 2000. The findings fit nicely with a similar pattern in recent pollinator trends: two recent papers have suggested that declines in pollinator diversity in the mid-20th Century slowed down or partially reversed over recent decades.
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The study also looked at the type of habitats most beneficial for pollinators, highlighting arable land as the poorest source of nectar: both in terms of amount and the diversity of sources. Improved grasslands could however contribute the most to national nectar supply if management favoured greater flowering of plants such as white clover.
Man-made Underwater Sound May Have Wider Ecosystem Effects Than Previously Thought
Underwater sound linked to human activity could alter the behaviour of seabed creatures that play a vital role in marine ecosystems, according to new research from the University of Southampton.
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These species make a crucial contribution to the seabed ecosystem as their burrowing and bioirrigation activities (how much the organism moves water in and out of the sediment by its actions) are crucial in nutrient recycling and carbon storage.
The study showed that some man-made sounds can cause certain species to reduce irrigation and sediment turnover. Such reductions can lead to the formation of compacted sediments that suffer reduced oxygen, potentially becoming anoxic (depleted of dissolved oxygen and a more severe condition of hypoxia), which may have an impact on seabed productivity, sediment biodiversity and also fisheries production.
Physics
Walking On Water: Researchers Unravel Science Of Skipping Spheres
It takes a perfect flick of the wrist and just the right angle to get a disk-shaped stone to skip across the surface of the water multiple times. So why is it so easy to get such impressive water-skipping performance from an elastic ball with only a mediocre launch?
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[scientists at the Naval Undersea Warfare Center in Newport, R.I., and Brown University, Assistant Professor of Mechanical Engineering Tadd Truscott and his associates at USU's Splash Lab use] high-speed cameras to capture images of elastic spheres bouncing across tanks of water in a laboratory. They found that elastic spheres skip along the water surface by deforming into an ideal disk-like geometry that resembles a stone one might find near the shore. Due to the sphere's deformed shape, the water exerts a larger lifting force on elastic spheres than stones.
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Truscott's study not only reveals the physics of how elastic spheres interact with water, but also predicts how many skips will occur. In addition, the team found that elastic spheres can bounce off the water surface from much higher impact angles compared to rigid spheres - a big clue into why these elastic objects are much easier to skip.
Skipping objects along the water surface has a wide range of applications from simple aquatic toys, to naval operations like the WWII-era Wallis Bomb, or the water-walking locomotion of the Basilisk lizard.
Truscott's setup may look like fun and games, but behind the scenes he and his team are conducting highly technical research with funding from the U.S. Navy. His work could help make inflatable boats and other soft-hull vessels safer for passengers and, on a more playful note, improve the design of water toys.
Robot Chameleon Changes Colour To Blend Into Its Surroundings
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The chameleon is a 3D-printed model covered in plasmonic displays, which produce colours by exploiting the interactions between nanoscale structures and electric fields. The team made the displays by taking a glass sheet bearing a grid of holes, each 50 nanometres across, and depositing gold on to it. This formed gold domes inside each hole. They then placed the sheet inside a casing filled with an electrolyte gel containing silver ions.
When light hits the gold nanostructures it produces ripples of electrons, called plasmons, that determine its reflective and absorbing properties – in this case, making the glass sheet appear red. Applying an electric field deposits some silver ions on to the gold domes, modifying their properties and producing different colours. Reversing the field strips off these ions and restores the red colour.
The team experimented with different strengths of field and durations to find out which colours they could make. To emulate a chameleon’s skin-changing abilities, they used light sensors to recognise the background colour and apply the appropriate field.
At the moment the sensors are limited to recognising only the primary colours red, green and blue. A more advanced system should be able to detect any colours, says Wang. “This would fully merge the mechanical chameleon into the surroundings.” If these advanced sensors can be miniaturised, the same principle could be used to develop adaptive camouflage systems for use by the military, he says.