Physics Today Daily Edition
Nature: In 2012, Stefan Gillessen of the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, and his colleagues spotted a gas cloud approaching Sagittarius A*, the black hole at the center of the Milky Way. It appeared that part of the cloud would get pulled off and hit the accretion disk that swirls around the black hole. The resulting collision would have created a large explosion of radiation. But that didn't happen. As Gillessen's team continued observing, they also looked at older data and found a second cloud of gas following the same path. They believe that means that the two clouds are actually part of a larger stream of gas, possibly pulled from a star that passed near Sagittarius A* within the last 100 to 200 years. Another group of researchers suggests that a star is hidden within the gas cloud and that the star's gravitation is what kept the cloud from fragmenting and falling into the black hole.
MIT Technology Review: Japanese researchers have been developing two different handheld devices that provide tactile data to the user. Both the Buru-Navi and Traxion systems use asymmetrical vibration to give the user the sensation of being pushed or pulled in a certain direction. In addition to being used in numerous applications such as navigation and gaming, the technology could help visually impaired people move around independently. Both devices will be demonstrated at the upcoming SIGGRAPH computer graphics conference in Vancouver, Canada.
New Scientist: The European Space Agency's Gaia was launched in December 2013 to Earth's Lagrangian point 2 to create a highly accurate map of 1 billion stars in the Milky Way. Gaia's accuracy is the result of its location combined with a sunshield and extremely sensitive monitoring of its rotation. That sensitivity has revealed that the satellite is being hit by more than 500 micrometeoroids per day, whereas the team monitoring Gaia had expected an impact rate of 1–10 per day. Where the cloud of dust originated is not known, but its presence is important for future missions to L2, such as NASA's James Webb Space Telescope. The Gaia mission has been plagued by several other difficulties that have delayed the release of data for more than 9 months.
Nature: Sandstone arches have long been thought to be formed by erosion. Now Jiri Bruthans of Charles University in Prague, Czech Republic, and his colleagues suggest that the structures form instead as the result of the pressure exerted by the rock's own weight. Prompted by observations of the creation of arches at a sandstone quarry, Bruthans's team sandwiched cubes of sandstone between pressure plates and then artificially weathered the rock. They found that as erosion removed material, which was initially relatively loose, the parts that suffered less erosion had to bear more of the weight and therefore suffered higher stress. In those areas, the grains locked together and became much more resistant to erosion. The result was the formation of arches and other similar structures.
BBC: A breakthrough has occurred in the negotiations between Iran and the P5 + 1 nations (the US, the UK, France, Russia, China, and Germany) concerning Iran’s stockpile of enriched uranium. Iran has converted all of its 20% enriched uranium—the level needed to make nuclear weapons—into more harmless forms that can be used for other purposes, such as in nuclear power stations and medical facilities. In exchange, some $2.8 billion in frozen Iranian funds will be unblocked. Although just three weeks ago no resolution appeared to be in sight, the latest development shows, according to some correspondents, that Iran’s leaders are serious in continuing the negotiations, which are set to resume in September.
Ars Technica: The W. A. Parish Generating Station in Thompsons, Texas, is a combination coal and natural gas power plant. Last week, construction began there of a carbon-capture facility funded by the US Department of Energy. The plant's emissions will be bubbled through an amine solution to separate out the carbon dioxide. The gas will then be pressurized and piped to the nearby West Ranch oil field, where it will be injected into the ground to help extract oil that would be otherwise difficult to obtain. The CO2 will remain sequestered in the ground. The project was originally planned to trap only a small portion of the emissions from the plant—those from the equivalent of 60 MW production out of the 3500 MW total. However, it was determined that the amount of CO2 captured would be too little to extract the oil, so the trapping was expanded to catch the emissions from the generation of 240 MW. That will make it the largest carbon-capture facility in the world.
Los Angeles Times: Astronomers have noted a curious absence of sunspots despite the fact that the Sun is at solar maximum—the period when the Sun’s magnetic fields are at their most intense. Areas where the magnetic fields are most concentrated are somewhat cooler than the surrounding surface and so appear to viewers on Earth as dark spots. As energy builds up in those areas, its release can cause solar flares and coronal mass ejections. But scientists say that temporary quiet interludes are not unusual even during periods of high solar activity. "You just can't predict the Sun," says solar physicist Tony Phillips.
Los Angeles Times: The heart beats because of pacemaker cells, which emit rhythmical electrical pulses. The cells are located in just one small part of the heart, the sinoatrial node. If the heart gets damaged and the electrical signals from the pacemaker cells can’t get through to the rest of the heart, the heartbeat can become slow and irregular or stop altogether. Despite the availability of artificial pacemakers, researchers at Cedars-Sinai Heart Institute in Los Angeles are working on a biological solution. They have found a way to transform regular heart cells into pacemaker cells by injecting them with a virus laced with the gene TBX18. Although they have successfully tested the therapy in pigs that suffered complete heart block, further research is needed to understand the long-term consequences before it can be applied to humans.
Science: Millions of years ago, the Amazon River reversed course and has been flowing eastward toward the Atlantic Ocean ever since. A previous study had suggested that the reversal was driven by a changing topography due to the movement of hot mantle material from Earth’s interior to its surface. Now Victor Sacek of the University of São Paulo in Brazil says it is more likely that erosion and sedimentation were the driving forces. More than 10 million years ago, rainfall across what is now the Amazon basin drained westward into lakes that formed along the eastern edge of the Andes, on the west coast of South America, and flowed north into the Caribbean Sea. To try to figure out what made the water flow reverse direction, Sacek ran computer models simulating the evolution of the South American terrain. He determined that sediment eroding off the Andes gradually filled in the lakes and built the landscape up such that it created a downhill slope extending from the Andes to the Atlantic. Neverthess, Sacek does not entirely rule out deep geologic processes; even though their overall effects are probably modest, he says, he plans to include them in future versions of his simulation to try to achieve a more accurate picture of how the landscape evolved.
BBC: Ray Smith of Lawrence Livermore National Laboratory in California and his colleagues used the National Ignition Facility (NIF) to subject a 1-mm diamond to the pressures believed to exist in Saturn's core. Planets the size of Saturn and Neptune are commonly found in exoplanet surveys, so better understanding of how matter exists within those worlds is important in understanding how they form. Smith's team achieved those pressures by focusing 176 of NIF's lasers on the target diamond. By carefully tuning the intensity of the lasers, the researchers were able to keep the temperature within the range that gas giants are known to experience. As the pressure increased, the team monitored the stress, density, and sound of the crystal. It is expected that diamond may undergo some phase changes at those pressures, but they were not detected. However, the rest of the measured characteristics matched predictions.