News Picks

Physics Today’s online staff summarize the most important and interesting news about science from the world's top media outlets.

There are 5 posts for the selected month (July 2015).
July 2, 2015 11:55 AM

Potential dark-matter signal likely just undiscovered pulsars

New Scientist: In 2009, NASA's Fermi satellite began detecting an apparent excess concentration of gamma rays that appeared to come from the Milky Way's central region. According to some theories, the signal could be the result of dark-matter collisions in the dense core region of the galaxy. Now, two independent teams analyzing the data argue that the signal did not account for thousands of previously undiscovered pulsars, which are rapidly rotating neutron stars that emit bright pulses of radiation. The finding is significant not just for potentially eliminating a sign of dark-matter collisions but for massively increasing the number of known pulsars in the Milky Way. More data will soon be available from Fermi that is expected to clarify the situation even further.
July 1, 2015 3:00 PM

Low-dose radiation has small but measureable long-term risk

Nature: A study of 300 000 nuclear-industry employees from France, the UK, and the US has provided the first clear look at the risks of low-dose ionizing radiation. The researchers obtained exposure records dating back 60 years for employees who worked in the industry for at least one year while wearing a dosimeter. The researchers then followed up to track mortality from leukemia, lymphoma, and multiple myeloma. The study revealed that on average the workers received 1.1 mSv per year above the average yearly background radiation, which is about 2–3 mSv. As the amount of radiation exposure increased, there was a linear increase in the rate of leukemia as well. Similar patterns for other cancers were not statistically significant. Instead of the 134 deaths expected from leukemia, the researchers found there were 531. And while none of those deaths occurred in any employee who received less than 50 mSv of radiation, the linear extrapolations suggest that every 10 mSv of radiation exposure increases the risk of leukemia by 0.002%.

July 1, 2015 2:30 PM

European Space Agency gets new director general

BBC: As of today the European Space Agency (ESA) has a new director general—Johann-Dietrich Woerner. He replaces Jean-Jacques Dordain, who had held the position since 2003. Besides continuing ESA’s ongoing programs and projects, such as the Rosetta mission, Woerner says he wants to plan for ESA's future, what he terms Space 4.0. That future includes the commercialization of space and increased interaction with society. Before assuming the ESA directorship, Woerner served as chief of the executive board of the German Aerospace Center.
July 1, 2015 1:54 PM

Hubble suggests quasars are driven by galactic collisions

Ars Technica: Quasi-stellar radio sources, or "quasars," are supermassive black holes, found at the center of galaxies, that produce extreme amounts of light as they pull material into themselves. The material swirling around the black holes is much brighter than the starlight of their host galaxies and can be up to 100 times brighter than all the stars in the Milky Way put together. That brightness disparity makes it hard to study quasars and to look past them to study their host galaxies. However, the difference in brightness is much less in certain areas of the spectrum. C. Megan Urry of Yale University and her colleagues used a near-IR camera on the Hubble Space Telescope to examine 11 quasars, all roughly 12 billion light-years away. They were selected because each is partially obscured by dust, which further reduces the brightness disparity. Urry's team found that all 11 of the host galaxies were undergoing collisions with other galaxies. That discovery supports the theory that galactic collisions drive the feeding of the black holes by disrupting the material surrounding them.

July 1, 2015 12:30 PM

Muon tomography used to inspect industrial equipment

Science: A new technique to scan equipment for problems or to look for nuclear material and other contraband uses the scattering of muons created when cosmic rays collide with molecules in Earth’s upper atmosphere. Able to penetrate matter more deeply than some other particles, muons have been used to image concrete degradation, valve conditions, and pipe-wall thickness at nuclear plants, according to a study published in AIP Advances. Imaging muons requires two sets of detectors to map the muons' trajectories before and after they pass through the object being studied. The denser the object, the more the muons are deflected. That information is then used to create a three-dimensional image of the mass distribution. Because muon radiation is ubiquitous on Earth and nonharmful to humans, muon tomography poses fewer problems and requires fewer safety measures than x-ray imaging. However, it takes longer to create an image, so it is better suited for routine inspections and monitoring.
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Scitation: News Picks - Blog