Physics Today Daily Edition
Ars Technica: Water vapor has been detected in the atmosphere of HAT-P-11b, an exoplanet about the size of Neptune. Until now, such detection had only been possible in the atmospheres of Jupiter-sized planets. The discovery was made from studying spectrographic data gathered by three spacecraft—the Hubble Space Telescope, the Spitzer Space Telescope, and Kepler. The lack of cloud cover around HAT-P-11b is what allowed researchers to study the spectrum of light that traveled through the planet’s atmosphere as it passed in front of its host star. Because different types of molecules absorb different wavelengths of light, the researchers were able to detect the presence of not only water vapor in the planet’s atmosphere but also hydrogen and small amounts of heavier elements. The ability to determine planets’ atmospheres, in addition to their mass and radii, could provide key insights into planetary formation and evolution. As higher-precision instruments, such as the James Webb Space Telescope, are developed, astronomers hope to be able to detect much fainter signals and even smaller planets.
BBC: Although the rainforests of the Amazon have long been fertilized by dust originating in the Sahara, the composition of that dust had not been extensively studied. Now Karen Hudson-Edwards of Birkbeck, University of London and colleagues show that one of the dust’s key nutrients, phosphorus, comes from the bones and scales of fish and other organisms that lived thousands of years ago in Megalake Chad. When they died, they sank to the bottom of the lake, which dried up and created a vast, dry dustbowl called the Bodélé Depression, the world’s greatest single source of dust. Strong surface winds regularly sweep across the area and carry millions of tons of dust across the Atlantic Ocean every year. By examining the crystalline structure of the apatite mineral found in the dust, the researchers determined that it came not from the weathering of rock but from once-living organisms. That type of phosphorus is more readily soluble and is commonly used in soil fertilizers. Hence, it is extremely important for maintaining the health of the Amazon rainforest. However, the Bodélé dust won’t last forever, and the researchers plan to look into precisely how long the essential material can be sustained.
Science: Motivated by a communications blackout in 2002 that led to a deadly US military operation in Afghanistan, researchers at the Johns Hopkins Applied Physics Laboratory have been looking more closely into the incident. Although it had been assumed that the problem lay with faulty radio equipment or blockage by the country’s mountainous terrain, Michael Kelly and colleagues say the radio interference was more likely caused by the presence of a large bubble of ionospheric plasma, which can form as the Sun strips electrons from gas molecules high in the atmosphere. Able to grow more than a thousand kilometers in size, the bubbles can cause electromagnetic turbulence that distorts radio waves. Thanks to data from NASA’s Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics satellite, which had been flying in the area at the time, the researchers have been able to confirm that there was indeed a plasma bubble between the battlefield and the radio communications satellites. Whether that caused the problem is still unknown. However, the discovery has led to the development of an improved warning system to prevent future problems such as occurred during Operation Anaconda.
Nature: Perovskites are materials that share the same crystal structure as calcium titanium oxide. Thin films of some members of the perovskite family can be used in photovoltaic cells. Over the past several years, the efficiency of such cells has tripled and now nearly matches that of commercial silicon solar cells. However, currently they are too small to be practical, and there are concerns about the material's durability and potential toxicity. Nevertheless, the low cost of creating perovskites has opened the door for a number of startups, as well as established companies, to begin working to solve those problems. One possible track has been to create combined cells that use perovskites to absorb wavelengths of light that silicon does not. Many of the companies expect to have something potentially usable in the next three to four years.
New Scientist: The transition to commercial companies for transporting astronauts to the International Space Station (ISS) may cost more than NASA has estimated. The agency expects that over the next 10 years its contribution to the ISS will be between $3 billion and $4 billion per year. But according to a recent report by NASA’s internal auditor, that projection is too optimistic and will probably be more. Much of the increase will likely come from higher transportation costs because NASA originally based its estimate on what the US will be paying Russia in fiscal year 2016 for seats on its Soyuz spacecraft. However, Boeing and SpaceX, the two private US companies that have been granted contracts, will probably charge more.
Telegraph: As the human population ages, more people are suffering the effects of osteoporosis. The disease causes loss of bone mass and density, which results in an increased risk of breaks and fractures. A preventive treatment is being developed that involves the injection of stem cells into the affected areas to protect and strengthen the thinning bone. The delicate stem cells are encased in calcium phosphate microspheres to protect them during the transplantation process. If the treatment proves successful, early screening could look for people who are most at risk, so they could receive treatment before a minor fall lands them in the hospital.
Science: Following the 2011 Fukushima Daiichi nuclear disaster, Joji Otaki of the University of the Ryukyus in Japan and her colleagues ran an experiment in which they fed radiation-contaminated plants to butterfly larvae. Although the larvae exhibited significant effects, including increased incidence of physical abnormalities and lower survival rates, the results were not unexpected because the plants' radiation levels exceeded 1000 Bq/kg, much higher than the limit of just 100 Bq/kg set by the Japanese government for food intended for human consumption. Now, Otaki's group has repeated the experiment almost two years later with plant material gathered from locations between 59 km and 1760 km from Fukushima and registering contamination levels between 0.2 Bq/kg and 161 Bq/kg. As expected, as the radiation level increased, the butterflies' mortality and abnormality rates increased. Even contamination at the relatively low, 100 Bq/kg level was found to harm wildlife. However, that finding can't be extrapolated to humans because butterflies are likely more sensitive to radiation.
New Scientist: Some regional warming trends are natural and not caused by anthropogenic climate change, according to a recent report published in the Proceedings of the National Academy of Sciences. In the US Pacific Northwest, temperatures have risen by about 0.8 °C since 1900. To try to understand why, James Johnstone and Nathan Mantua of the University of Washington in Seattle compared the air pressure at sea level with sea-surface and air temperatures over the past century. They noticed a strong correlation between changes in sea-surface temperature and changes in atmospheric circulation. "The most straightforward explanation is that changes in the wind have forced the changes in the temperature," says Johnstone. Although they don’t know what causes the winds to shift, they could find no obvious link to global warming.
Nature: The Department of Energy's Fusion Energy Sciences Advisory Committee (FESAC) has released a report that recommends cutting two fusion projects in favor of increased focus on ITER. The report suggests that MIT's Alcator C-Mod reactor, which had been defunded in 2012 but restarted this year, be shut down in 2015. Depending on the budget outlook, it also recommends closing either General Atomics' DIII-D in San Diego, California, or the National Spherical Torus Experiment in Princeton, New Jersey, by 2020. The committee did recommend constructing some new facilities and upgrading current ones, but it was not allowed to reconsider the US contribution to ITER. ITER has already cost $50 billion, 10 times its projected cost, and is 11 years behind schedule.
Ars Technica: Quasars are black holes that pull in massive amounts of matter, shine brightly across the electromagnetic spectrum, and emit jets of extremely high-energy particles. They have been hard to categorize, however, because of their wide range of appearances and characteristics. Now, Yue Shen and Luis C. Ho of Peking University have compiled a database of more than 20 000 quasars found by the Sloan Digital Sky Survey. They recorded the quasars' spectra, the orientation of their accretion material, and a characteristic called the Eddington ratio, which compares a quasar's luminosity with its theoretical maximum and thus is a measure of the accretion efficiency. By comparing the disk orientation with accretion efficiency and spectral line strength, they created a graph that fits all of the quasars into a well-defined, orderly plot. Determining the cause of the distinctive pattern could provide significant insight into the properties of quasars. Separately, the study found that the highest-mass quasars (the ones with the lowest Eddington ratios) are clustered together, which hints at some connection between quasars and the large-scale structure of the universe.