Waves & Packets
May. 12, 2012

Unseen planet revealed by its gravity
Southwest Research Institute
Using gravitational perturbation theory and publically photometry data from the Hunt for the Exomoons with Kepler project, a group of researchers has inferred the existence of at least one other planet near the distant star, KOI-872, where two other planets are confirmed to be orbiting. The Kepler telescope continuously monitors the brightness of more than 150,000 stars, searching for brief periods of time, known as transits, when a star appears fainter due to a planet passing in the foreground. The transit times can be influenced by other massive objects, including other planets. The existence of Neptune was inferred by the gravitational effects it has on the observed position of Uranus.

In this current work, reported in Science and discussed with Waves and Packets by lead author David Nesvorný, the team constructed a set of dynamical models with different levels of complexity and sizes of parameter space. Statistical analysis of the various models led them to identify a single-perturbing-planet model as the clear best fit to the photometry data. But a subsequent specialized analysis of the photometry data led them to inferentially identify another much smaller, nonperturbative planet that may orbit KOI-872. Altogether the analysis indicates a system with nearly coplanar and circular orbits, very much like our own solar system.More

Researchers develop and test theory of planetary formation
Los Alamos National Lab
In work based on the core accretion model of planet formation, researchers at LANL's Nuclear and Particle Physics, Astrophysics and Cosmology group suggest that the first planets in the universe formed well after the first generations of stars. Under the core accretion model dust grains in a protostellar disk coagulate into planetesimals, which then assemble into planets with solid cores. This new work, reported in the Astrophysical Journal, identifies a critical "metallicity", i.e., presence of elements heavier than hydrogen and helium, such as oxygen, silicon and iron, that is necessary to form planetesimals during the early dust coagulation phase of the model. Because these elements were not formed in the big bang, they must have been produced by fusion reactions in stars and supernovae, indicating that planets form around stars.More

Astronomers discover a rare stellar disk of quartz dust
National Astronomical Observatory of Japan
A team of astronomers using both the AKARI and Spitzer infrared space telescopes has discovered a main-sequence star, HD 15407A, that is surrounded by a rare disk of quartz (silicon dioxide) dust. The star heats the dust, and this energy is re-emitted in the form of infrared radiation. Their examination of the Spitzer spectrum, reported in the Astrophysical Journal Letters, revealed that at least 100 trillion tons of tiny particles of quartz dust orbit the star. It is not yet clear how the quartz dust formed, but they were able to determine that the dust is located about 1 AU (astronomical unit) from the central star in the so-called "terrestrial planet region." According to a widely accepted scenario of planet formation, rocky planets form from collisions and aggregations of such dust. Since the Earth's crust contains a large amount of quartz-like minerals, this suggests that the quartz dust around HD 15407A might come from the surface layers of large rocky bodies colliding with other planetesimals orbiting the star and the dust itself will become the surface layer of a rocky planet.More

Gamma-ray lens opens new doors for theory and applications
Science Now
Focusing gamma-rays via lenses is very difficult because the EM waves bypass the electrons that normally account for refraction. So, the index of refraction of materials for gamma-rays materials is very small, and thought to be less than that for X-rays. But a group of physicists from France and Germany have come upon a surprising result. When they sent gamma-rays of 700 keV through silicon they found that the index of refraction starts to increase, and furthermore that while the index of refraction is negative for X-rays, it becomes positive for gamma rays. This result, published in Physical Review Letters, is attributed to Delbrück scattering, which occurs when an incident photon has enough energy to penetrate close enough to the nucleus to produce an electron–positron pair. This invites new theoretical analysis of quantum electrodynamics beyond the Schwinger limit — the point at which traditional perturbative treatments of quantum electrodynamics break down. Delbrück scattering is assumed to be a weak effect, but it is likely much more complicated than that. In any event, gamma-ray lenses open up new vistas for optics with potential applications in medical imaging and security screening.More

Quantum spin-liquid observed
NIST Center for Neutron Research
An international team of researchers has found what may be the first known example of a "spin-orbital liquid," a substance in a never-before-seen quantum mechanical state. The properties of a spin-liquid relate to the same quantum effects that give rise to superconductivity, so physicists have long sought this latest discovery, which is reported Science. The substance under consideration was actually crystalline solid Ba3CuSb2O9. But the copper atoms were positioned in the solid's hexagonal lattice structure in such a way that their atomic spins incessantly disturb each other. They pushed each other around so they were unable to form an ordered configuration. The result was a quantum spin fluid within a solid.More

Hydrogen bond disruption predicts protein-protein binding
American Physical Society
Many biological processes depend on the physical attraction between pairs of proteins. Electrostatic interactions are the most energetically profound determinates of binding. But just as important, from an entropic point of view, is the structure of water shells around the two proteins, both before and after binding. When water molecules are highly coordinated they will form very stable hydrogen bond networks that are very hard to disrupt. A researcher in Argentina has developed a new way to quantify the average number of neighbors for each water molecule at each position. This solvent-centric method, published in Physical Review Letters, is computationally expensive, but shows great promise in predicting protein-protein binding. More

1st results from NASA SOFIA mission using German GREAT receiver
Deutsches Zentrum für Luft und- Raumfahrt (The German Aerospace Center)
NASA's Stratospheric Observatory for Infrared Astronomy has completed its first series of science flights, using the German Receiver for Astronomy at Terahertz Frequencies. The scientific results are now being published in a special issue Astronomy & Astrophysics along with reports on GREAT's advanced technologies. SOFIA operates a 2.7-m telescope in a modified Boeing 747SP aircraft and is the world's largest airborne infrared observatory. It cruises near 40,000 feet about where water vapor would absorb most of the incoming IR radiation. The GREAT instrument extends the telescopes abilities to higher frequencies. Many of the contributed papers study the star formation process in its earliest phases, first when the protostellar molecular cloud is contracting and condensing, and then when the embryonic star is vigorously interacting with its surrounding parental molecular cloud — tearing it apart and ionizing it. Amongst the new scientific results is first observation of OD, an isotopic substitute for hydroxyl, whose hydrogen atom is replaced by its heavier isotope, deuterium and interstellar sulfanyl. Earlier results using SOFIA and Cornell University's Faint Object Infrared Camera were published in a special issue of Astrophysical Journal Letters.More

Black hole activity throttles star formation
Ars Technica
In a blistering and luminous wind, black holes consume the materials needed for star formation. At least that is the conventional wisdom though direct evidence has been lacking. But now a team of astronomers using the Chandra Deep Field North X-ray survey and the submillimeter instrument on the Herschel Space Observatory have measured both the star formation rate and black hole activity in 176 galaxies with active galactic nuclei. Black hole activity is indicated by X-ray emission, while star formation produces 250 micron light, which is not associated with black hole activity. Reporting in Nature, the researchers found that in brightly X-ray luminous AGNs there was no 250 micron emission, indicating no star formation. They also found that in low X-ray luminous AGNs, there is a critical point in X-ray luminosity above which no star formation light signatures are found. This result provides strong support for the proposition of AGN consumption of star forming material, and for shared evolution of galaxies and the black holes at their hearts. More

New twist on ancient math problem could improve medicine, microelectronics
University of Michigan
Simple problems like how many uniformly sized marbles are inside a box (the packing problem), or how many uniformly sized rectangular tiles does it take to cover a sphere (the covering problem) have complex mathematical solutions. Another question to ask is how to completely fill a space with uniform shapes but of any size, where the shapes can also physically overlap. This is the filling problem. Filling addresses the optimal placement of overlapping objects lying entirely inside an arbitrary shape so as to cover the most interior volume. Researchers at the University of Michigan have shown in a Physical Review Letters paper that for a given shape, you only need to consider solutions where the filling objects lie on the shape's medial axis—a line-like skeleton that represents the shape's topology. This result can have applications from medical physics, to microelectronics and animated computer graphics.More

How to begin a career in photonics
Laser Focus World
Students interested in a career in optics and photonics should carefully research which institutions are a geographic, academic and financial fit; which institutions offer a fast track to industry through collaborative programs; and whether or not the technician option makes more sense. Hundreds of program listings are in the Optics and Photonics Education Directory — by far the most comprehensive global listing of degree programs in optics and photonics. University of Arizona, University of Central Florida and University of Rochester are the three U.S. powerhouses in optics/photonics education. Opportunities at these places span from engineering and biomedical applications to basic physics, and on to entrepreneurism, sales and marketing. There are also great opportunities in Europe, Asia, Latin and South American and Africa.More

Charting a course for a successful research career
Today's research landscape provides a wealth of information resources, analysis tools, collaborative networks and facilities. Yet, at the same time there is a stark increase in competition, especially for job and funding opportunities. With as many potential pitfalls as there are opportunities, getting an academic career on the right road to success can be a daunting challenge. Elsevier's newly revised "Charting a Course for a Successful Research Career" is a crash course of practical advice on how to plan your career. Rich in advice on the do's and the don'ts along your career path, the booklet covers wide-ranging topics from planning your career to preparing a grant funding application, to selecting a research discipline, supervisor and mentor. It also discusses the importance of getting recognized for the work you do, and how to avoid unnecessary career detours into the undergrowth of an unplanned career journey.More

Women's scientific achievements often overlooked, undervalued
Medical Daily
A new study from published in Social Studies of Science reveals that when men chair committees that select scientific awards recipients, males win the awards more than 95 percent of the time. This study also found that compared to men, women win more service and teaching awards and fewer prestigious scholarly awards than would be expected based on their representation in the nomination pool. In the past two decades, women have begun to win more awards for their scientific achievements, increasing by 78.5 percent. But the authors suggest that women-only awards can camouflage women's underrepresentation by inflating the number of female award recipients, leading to the impression that no disparities exist. More

How academic biologists and physicists view science outreach
Rice University
In recent years, scientists have been under scrutiny to demonstrate the public relevance of their government-funded research. A new study, recently reported in the open access journal PLoS ONE, has found that women, especially those with children, are much more involved in outreach efforts than their male counterparts. But academic scientists face significant barriers to participating in outreach, most notably the perceptions amongst peers that research, not outreach, should be their top priority in their role as academics, and that participating in outreach may hurt their research output.More

National Society of Black Physicists jobs board postings
Kenyon College One-year Visiting Assistant Professor of Physics
Faculty Positions in Science, Technology and Innovation
NASA Postdoctoral Fellowships
National Astrophysics and Space Science Program
Postdoctoral Research Associate PositionsMore

Latest research from American Journal of Physics
American Journal of Physics
Teaching physics with Hubble's law and dark matter

Measurement of the Earth’s rotational speed via Doppler shift of solar absorption lines

Using online telescopes to explore exoplanets from the physics classroom

A robotic observatory in the city

Computing accurate age and distance factors in cosmology More

Latest research from Radiation Physics and Chemistry: The Journal for Radiation Physics, Radiation Chemistry and Radiation Processing
Radiation Physics and Chemistry: The Journal for Radiation Physics, Radiation Chemistry and Radiation Processing
Investigation of O7+ swift heavy ion irradiation on molybdenum doped indium oxide thin films

Dose estimation and dating of pottery from Turkey

Commercial scale irradiation for insect disinfestation preserves peach quality

Design and simulation of neutron radiography system based on 241Am–Be source

Gamma radiation effects on physico-chemical parameters of apple fruit during commercial post-harvest preservation

Contact radiotherapy using a 50 kV X-ray system: Evaluation of relative dose distribution with the Monte Carlo code PENELOPE and comparison with measurements

Carbon ion beam induced modifications of optical, structural and chemical properties in PADC and PET polymersMore