Scientists make first discovery using revolutionary long wavelength demonstrator arrayAugust 19, 2009Scientists from NRL's Space Science and Remote Sensing Divisions, in collaboration with researchers from the University of New Mexico (UNM) and the National Radio Astronomy Observatory (NRAO) located in Socorro, N.M., have generated the first scientific results from the Long Wavelength Demonstrator Array (LWDA). The measurements were obtained during field tests and calibration of two prototype antennas for the much larger Long Wavelength Array (LWA), which will eventually consist of nearly 13,000 similar antennas. Utilizing radio emissions from the approximately 300 year-old Cassiopeia A (Cas A) supernova remnant (SNR)-one of the brightest astronomical radio sources in the sky-to establish baseline measurements, NRL scientist and National Research Council (NRC) postdoctoral fellow Dr. Jake Hartman utilized the LWDA to confirm and extend a study initiated by fellow NRL-NRC postdoc Dr. Joseph Helmboldt. Using NRAO's Very Large Array (VLA) radio telescope, Dr. Helmboldt's research showed that the gradually weakening Cas A displays signs of a "softer" smooth, secular decrease and an apparent shorter term variability at frequencies below 100 MHz. "Cas A has long been known to be fading, but the slower, seemingly irregular decrease at frequencies lower than 100 MHz has remained controversial," said Dr Namir Kassim, astronomer and LWA project scientist, NRL. "Dr. Hartman's discovery reaffirms this supposition and provides strong support that more frequent time sampling will be needed to determine whether the shorter term variations contain a non-random component." Dr. Helmboldt's measurements were able to significantly improve constraints on the smooth secular decrease, confirming earlier indications that the decrease was slower than originally determined several decades ago. He was also able to verify earlier indications of variations on shorter timescales, including the possibility that they might contain a sinusoidal component. Scientifically, these new measurements taken by Dr. Hartman are significant because they must be explained by diffusive shock acceleration theory-which helps describe how the blast wave from a relatively recent supernova explosion like Cas A is able to accelerate relativistic particles and generate radio emission. The theory must account both for the relatively smooth, longer-term rate at which the emission is gradually fading, as well as the shorter-term variability that is likely related to the properties of the region into which the SNR is expanding. "The result is exciting because it represents 'first science', and is increasingly intriguing as it is based on measurements from only two dipole antennas, as compared to the more than 13,000 that will eventually comprise the full LWA," said Dr. Paul Ray, astronomer, NRL. "For a project whose broader goals encompass engaging and training a next generation of young radio scientists we are proud that this first astronomical result emerged from the work of two postdocs, neither of whom were experts in this area of research." Once completed, the LWA will provide an entirely novel view of the sky in the radio frequency range of 20-80 MHz, currently one of the most poorly explored regions of the electromagnetic spectrum in astronomy. The LWA will be able to make sensitive high-resolution images, scanning the sky rapidly for new and transient sources of radio waves that may represent the explosion of distant massive stars or detect emissions from planets outside of our own solar system and previously unknown objects or phenomena. "We're now laying the infrastructure for the first LWA antenna station," said Joe Craig, LWA system engineer, UNM. "It's really an exciting period for everyone involved." LWA will also provide an unparalleled measure of turbulence and waves in the Earth's ionosphere, together with unique diagnostics of phenomena manifested through the Sun-Earth connection also known as "Space Weather." Naval Research Laboratory |
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| Related Wavelength Current Events and Wavelength News Articles Engineered metamaterials enable remarkably small antennas In an advance that might interest Q-Branch, the gadget makers for James Bond, the National Institute of Standards and Technology (NIST) and partners from industry and academia have designed and tested experimental antennas that are highly efficient and yet a fraction of the size of standard antenna systems with comparable properties. Stacking the deck: Single photons observed at seemingly faster-than-light speeds Researchers at the Joint Quantum Institute (JQI), a collaboration of the National Institute of Standards and Technology and the University of Maryland at College Park, can speed up photons (particles of light) to seemingly faster-than-light speeds through a stack of materials by adding a single, strategically placed layer. New Quantum Cascade Lasers Emit More Light Than Heat Northwestern University researchers have developed compact, mid-infrared laser diodes that generate more light than heat - a breakthroughs in quantum cascade laser efficiency. UBC astronomers unveil images of 12-billion-year-old space nursery A University of British Columbia astronomer has produced the most detailed images of deep space from 12 billion years ago, using data from the European Space Agency's Herschel Space Observatory. Hubble finds most distant primeval galaxies The NASA/ESA Hubble Space Telescope has broken the distance limit for galaxies and uncovered a primordial population of compact and ultra-blue galaxies that have never been seen before. Astronomers detect earliest galaxies Astronomers, using NASA's Hubble Space Telescope, have broken the distance limit for galaxies by uncovering a primordial population of compact and ultra-blue galaxies that have never been seen before. They are from 13 billion years ago, just 600 to 800 million years after the Big Bang. New panchromatic capabilities of Hubble reveal an unprecedented view of the universe Shown in an extremely broad range of color and showcasing more than twelve billion years of cosmic history, Hubble's recent image is a full-glory cosmic renaissance of the history of the Universe. Brown dwarf pair mystifies astronomers Two brown dwarf-sized objects orbiting a giant old star show that planets may assemble around stars more quickly and efficiently than anyone thought possible, according to an international team of astronomers. Seeing how evolutionary mechanisms yield biological diversity An international team of scientists has discovered how changes in both gene expression and gene sequence led to the diversity of visual systems in African cichlid fish. Caltech scientists film photons with electrons Techniques recently invented by researchers at the California Institute of Technology (Caltech)-which allow the real-time, real-space visualization of fleeting changes in the structure of nanoscale matter-have been used to image the evanescent electrical fields produced by the interaction of electrons and photons, and to track changes in atomic-scale structures. More Wavelength Current Events and Wavelength News Articles |
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