Astronomy
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The Sun Probably Lost A Binary Twin Billions Of Years Ago
For us Earthlings, life under a single Sun is just the way it is. But with the development of modern astronomy, we’ve become aware of the fact that the Universe is filled with binary and even triple star systems. Hence, if life does exist on planets beyond our Solar System, much of it could be accustomed to growing up under two or even three suns. For centuries, astronomers have wondered why this difference exists and how star systems came to be.
Whereas some astronomers argue that individual stars formed and acquired companions over time, others have suggested that systems began with multiple stars and lost their companions over time. According to a new study by a team from UC Berkeley and the Harvard-Smithsonian Center for Astrophysics (CfA), it appears that the Solar System (and other Sun-like stars) may have started out as binary system billions of years ago.
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For several decades, astronomers have known that stars are born inside “stellar nurseries”, which are the dense cores that exist within immense clouds of dust and cold, molecular hydrogen. These clouds look like holes in the star field when viewed through an optical telescope, thanks to all the dust grains that obscure light coming from the stars forming within them and from background stars.
Radio surveys are the only way to probe these star-forming regions, since the dust grains emit radio transmissions and also do not block them. For years, Stahler has been attempting to get radio astronomers to examine molecular clouds in the hope of gathering information on the formation of young stars inside them. To this end, he approached Sarah Sadavoy – a member of the VANDAM team – and proposed a collaboration.
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“The idea that many stars form with a companion has been suggested before, but the question is: how many? Based on our simple model, we say that nearly all stars form with a companion. The Perseus cloud is generally considered a typical low-mass star-forming region, but our model needs to be checked in other clouds.”
Brown Dwarfs vs. Stars: What Makes A Star A Star?
When you go outside at night and look up at the sky, regardless whether you’re in a bright city or the dark countryside, there’s a lot more than meets the eye. For every 100 stars you see, astronomers think there could be between dozens of “failed stars” — also known as brown dwarfs — that you don’t.
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Defining Stardom
Almost a decade ago, [Trent Dupuy (University of Texas at Austin) and Michael Liu (University of Hawai'i)] began observing the orbits of 31 low-mass binary systems, all within 130 light-years of Earth. Each pair consists of two brown dwarfs or extremely low-mass stars — in other words, objects on either side of the defining line of stardom.
By measuring the period and size of each pair’s mutual orbit, astronomers can calculate the objects’ masses. The researchers targeted systems close enough together that they would complete more than a third of their orbits between 2008 and 2010, a requirement to ensure accurate measurements of the systems’ orbital parameters.
Since dwarf stars are quite small and faint, Dupuy and Liu made use of two of the most powerful telescopes available: the ground-based Keck Observatory and the space-based Hubble Space Telescope. By observing each binary with both telescopes, they nailed down the object's positions as well as their motions through space. They then used the Canada-France-Hawaii Telescope to take images with a wider field of view, so they could determine the center of mass around which each system orbits. Their final data set, visualized below, yielded masses for 38 brown dwarfs — increasing the number of brown dwarfs with known masses by an order of magnitude.
Based on these masses, Dupuy and Liu have determined that a gaseous ball must contain a minimum of 70 times Jupiter’s mass to ignite nuclear fusion and give birth to a star. Anything less than that will produce an object fated to brown dwarf status. The lower the mass, the lower the object’s temperature, and according to Dupuy and Liu, all objects with a surface temperature cooler than about 1600K (2400°F) must be brown dwarfs.
Biology
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Ancient DNA Shakes Up The Elephant Family Tree
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Straight-tusked elephants roamed Europe and Asia until about 30,000 years ago. Much like modern Asian elephants, they sported high foreheads and double-domed skulls. These features convinced scientists for decades that straight-tusked and Asian elephants were sister species, says Adrian Lister, a paleobiologist at the Natural History Museum in London who was not involved in the study.
For the new study, researchers extracted and decoded DNA from the bones of four straight-tusked elephants found in Germany. The fossils ranged from around 120,000 to 240,000 years old. The genetic material in most fossils more than 100,000 years old is too decayed to analyze. But the elephant fossils were unearthed in a lake basin and a quarry, where the bones would have been quickly covered with sediment that preserved them, says study author Michael Hofreiter of the University of Potsdam in Germany.
Hofreiter’s team compared the ancient animals’ DNA with the genomes of the three living elephant species — Asian, African savanna and African forest — and found that straight-tusked genetics were most similar to African forest elephants.
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Accounting for this new finding may not be as simple as moving one branch on the elephant family tree, Lister says. It’s possible that straight-tusked elephants really were a sister species of Asian elephants, but they exhibit genetic similarities to African forest elephants from interbreeding before the straight-tusked species left Africa.
It’s also possible that a common ancestor of Asian, African and straight-tusked elephants had particular genetic traits that were, for some reason, only retained by African and straight-tusked elephants, he says
Reshaping Darwin’s Tree Of Life
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A new era in science has emerged without a clear path to portraying the impacts of microbes across the tree of life. What’s needed is an interdisciplinary approach to classifying life that incorporates the countless species that depend on each other for health and survival, such as the diverse bacteria that coexist with humans, corals, algae and plants, according to the researchers [...].
“In our opinion, one should not classify the bacteria or fungi associated with a plant species in separate phylogenetic systems (trees of life) because they’re one working unit of evolution,” said paper senior author Debashish Bhattacharya, distinguished professor, Department of Ecology, Evolution and Natural Resources, in the Rutgers School of Environmental and Biological Sciences. “The goal is to transform a two-dimensional tree into one that is multi-dimensional and includes biological interactions among species.”
A tree of life has branches showing how diverse forms of life, such as bacteria, plants and animals, evolved and are related to each other. Much of the Earth’s biodiversity consists of microbes, such as bacteria, viruses and fungi, and they often interact with plants, animals and other hosts in beneficial or harmful ways. Forms of life that are linked physically and evolve together (i.e. are co-dependent) are called symbiomes, the paper says.
The authors propose a new tree of life framework that incorporates symbiomes. It’s called SYMPHY, short for symbiome phylogenetics. The idea is to use sophisticated computational methods to paint a much broader, more inclusive picture of the evolution of organisms and ecosystems. Today’s tree of life fails to recognize and include symbiomes. Instead, it largely focuses on individual species and lineages, as if they are independent of other branches of the tree of life, the paper says.
The authors believe that an enhanced tree of life will have broad and likely transformative impacts on many areas of science, technology and society. These include new approaches to dealing with environmental issues, such as invasive species, alternative fuels and sustainable agriculture; new ways of designing and engineering machinery and instruments; enlightened understanding of human health problems; and new approaches to drug discovery.
Chemistry
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Caesium Chloride
Caesium is one of those elements that feels unfamiliar – it would probably be ‘pointless’ in a periodic table question on the eponymous TV show – which leaves a compound like caesium chloride in inevitable obscurity. Yet, while only about 20 tonnes of this colourless crystalline substance are produced each year, it has a surprisingly wide range of applications. Structurally, the salt is a simple chloride like the more familiar sodium chloride, but because caesium is a lot closer to chlorine in size, it forms a crystalline structure where each caesium ion is surrounded by eight chlorines at the corners of a cube. By contrast, in sodium chloride, each ion is surrounded by six of its counterpart in an octahedral shape.
The best-known uses are probably those involving a radioactive form of the salt. Caesium chloride with the non-radioactive caesium 133 occurs naturally, as a trace constituent in some minerals and in mineral water (which is where caesium was discovered). It is most concentrated in a mineral called pollucite, also containing aluminium and silicon amongst other constituents, where the caesium makes up around 20 per cent of the whole. Elemental caesium itself is usually produced from the caesium chloride extracted from the mineral. But to create the radioactive form of the compound, it is enriched with caesium isotopes, particularly caesium 137, produced in the waste of nuclear reactors.
This radioactive form is used to treat cancers and is relatively unusual in medical radioisotopes in being water soluble. It’s generally preferred that a compound for this use can’t be easily spread in an accident, but caesium chloride packs a lot of radioactivity into a small volume, making it ideal for treatments where the radioactive material needs to be accurately sited.
Generally, the radioactive form is kept in highly secure containers, but in 1987 a caesium chloride source containing about 93 grams of the salt was stolen from an disused hospital in Goiania, Brazil. The thieves partially broke open the container and sold it on for scrap. Because the exposed caesium chloride gave off an eerie blue glow, it proved a popular talking point – just as radium did when first discovered by the Curies. Samples of the glowing powder were shared around to the extent that the scrapyard owner’s six-year-old niece used it as a skin decoration. She was one of four who died as a result of the exposure, with over 200 more suffering significant radioactive contamination.
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Although caesium chloride itself is only slightly electrically conductive, a thin layer of it can enable the production of electrically conductive glass, and finds an experimental application in boosting the efficiency of solar cells. It is also found in specialist ultraviolet excimer lamps, solders and, perhaps most surprisingly, in the production of beers and mineral waters. It is described as being used to ‘improve the taste of mineral water’, though it’s hard to see exactly how – one commentator described sampling caesium chloride: ‘[It] does NOT taste very good at all, and sort of burns a bit. It’s very metallic in taste and has a horrible aftertaste.’ The caesium compound caesium carbonate is sometimes used in small quantities to improve the foamy qualities of the head on a beer, but it’s not clear how the chloride enhances the brewing process.
Ecology
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Refining The Ocean’s Thermometer
Chronicling Earth’s past temperature swings is a basic part of understanding climate change. One of the best records of past ocean temperatures can be found in the shells of marine creatures called foraminifera.
Known as “forams” for short, these single-celled plankton build microscopic calcite shells. When forams die, their shells fall to the ocean floor and accumulate in sediments that provide a record of past climate. The surface-feeding plankton are natural thermometers because the chemical makeup of foram shells is linked to the environmental conditions they grow in. For example, the levels of magnesium in foram shells reflect the seawater temperature in which they lived.
Ideally, forams would act as “perfect chemists” by incorporating magnesium and calcium according to well-understood chemical relationships, said study co-author Ann Russell, a researcher in paleoceanography at UC Davis. But many foram shells have alternating bands of high and low magnesium levels within their calcite shells that cannot be explained by temperature alone. These bands are only a few microns wide.
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Light/Dark Cycles Drive Magnesium Bands
Recent experiments led by UC Davis scientists show magnesium levels vary in foram shells due to different growth rates during daily light/dark cycles. [...] Earlier research at UC Davis and elsewhere had already hinted that changing sunlight levels influence shell chemistry. To investigate this idea, the research team grew foraminifera in controlled light conditions and then analyzed the shells. The team directly measured the levels of magnesium and other trace elements in the shells with high-resolution imaging techniques called laser ablation ICP-MS and NanoSIMS image mapping.
“Understanding foraminifera growth patterns is essential for understanding the mechanisms responsible for their shell chemistry and for properly interpreting past temperature records,” [lead study author Jennifer Fehrenbacher, an assistant professor of tracer oceanography at Oregon State University] said.
Feeling The Heat: How Fish Are Migrating From Warming Waters
The Cape Cod Canal is a serpentine artificial waterway that winds eight miles from Cape Cod Bay to Buzzards Bay. On warm summer evenings, anglers jostle along its banks casting for striped bass. That’s what 29-year-old Justin Sprague was doing the evening of August 6, 2013, when he caught a fish from the future.
At first, Sprague thought the enormous fish that engulfed his Storm blue herring lure was a shark. But as he battled the behemoth in the gloaming — the fish leaping repeatedly, crashing down in sheets of spray — he realized he’d hooked something far weirder. When the fisherman finally dragged his adversary onto the beach, a small crowd gathered to admire the creature’s metallic body, flared dorsal fin, and rapier-like bill. Sprague had caught a sailfish.
It doesn’t take an ichthyologist to know that sailfish don’t belong in the Cape Cod Canal. Istiophorus albicans favors the tropics and subtropics; it so rarely visits New England that Massachusetts didn’t even have a state record. But strange catches — including cobia and torpedo rays — have become more commonplace. Over the last decade, the Gulf of Maine, the basin that stretches from Cape Cod to Nova Scotia, has warmed faster than nearly every other tract of ocean on earth, as climate change joined forces with a natural oceanographic pattern called the Atlantic Multidecadal Oscillation to increase sea surface temperatures by 3.6 F from 2004 to 2013. The results have been ecological transformation, upheaval in marine fisheries management, and an alarming window onto the warm future of global oceans.
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Although warming water is the most immediate agent of oceanic chaos, it’s just one front in climate change’s three-pronged assault on marine life. As the ocean absorbs carbon dioxide, it becomes more acidic and less saturated with the calcium carbonate that organisms like corals and pteropods — planktonic snails that support food webs — need to build shells. Fish are far from immune: Ocean acidification may disrupt the development of larval fish and reduce their survival rates, according to a study last year in the journal PLOS One.
Deoxygenation is an even more immediate threat. Scientists have long been acquainted with low-oxygen “dead zones” that form annually in the Gulf of Mexico, the Chesapeake Bay, and other coastal areas where agricultural runoff accumulates. As oceans heat up, those localized hypoxic areas are expected to spread: Not only does warm water hold less dissolved oxygen than cool water, it also tends to divide into layers that don’t readily mix. According to one recent study, the ocean has been losing oxygen since the mid-1980s, likely because rising temperatures have impeded circulation. Lisa Levin, a professor at Scripps Institution of Oceanography, points out that not all creatures are equally fazed: Along the naturally oxygen-poor Pacific Coast, marine life is well evolved to cope. But all animals have their limits.
Physics
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Octopus Inspired Adhesive Patch Works Under Water
A team of researchers at Sungkyunkwan University in South Korea has developed a type of adhesive patch that works under a variety of conditions including underwater. In their paper published in the journal Nature, the team describes how they studied octopus suction cups to design a better patch for human applications.
In their search to create a better adhesive patch, the researchers looked to suction cups used by octopuses to grip objects and prey. They mimicked the suction cups by creating polymer sheets with cup-like dimples with soft spheres in the middle of each. They then tested differently sized dimples and spheres and found that 50 micrometer dimples offered the best grip, which, as it turned out, was the one closest to that used by an octopus in its underwater world. To better understand how the suction cups worked, the researchers studied their own creations under a microscope and discovered the secret to the octopus grip is water getting trapped beneath the sphere near the back edges of the cup—it creates a vacuum chamber when pressure is released.
In testing the patches, the researchers found them able to attach and detach up to 1000 times without the need for replenishment—and without the need for adhesive materials. This, the team notes, makes them a much better option for skin patches as anyone who has used an adhesive patch can attest. Removing sticky patches can be painful, particularly if they have been used to cover a wound. The researchers report also that the patch could adhere to many surfaces, both flat and curved, including skin. And of course, it stuck just as well when the skin was wet. Perhaps most interesting was the fact that the vacuum also allowed the suction cup to work underwater.
The patches the group made were simple rectangular sheets of dimpled plastic with tiny spheres in the middle of each, anchored to the sheet. The patches adhered when pressure was applied. Of course, for the patch to be used in medical or industrial applications a means for releasing the pressure created by the vacuum must be found, perhaps one based on the way an octopus releases its grip.