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Everything Space
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Written by Everything Science
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Feb 22, 2005 at 02:35 AM |
Observing the edge of the famous Horsehead Nebula with the IRAM interferometer located on the Plateau de Bures (France), a team of French and Spanish astronomers discovered a large quantity of small hydrocarbon molecules. This is a surprise because the intense UV radiation illuminating the Nebula should destroy the small hydrocarbons near the edge. The astronomers suggest that these molecules might result from the fragmentation of giant molecules, called “polycyclic aromatic hydrocarbons†(PAHs).
More than 120 molecules have been observed in the interstellar medium, of which about twenty are small hydrocarbons. These hydrocarbons are an important component of the interstellar chemistry as they furnish a carbon skeleton needed to build more complex molecules. However, these small hydrocarbons are easily broken apart by the UV radiation from young stars. Therefore, astronomers try to understand how these molecules are regenerated in spite of their destruction by UV radiation.
 | In the overall picture of the Horsehead Nebula (copyright ESO), the white frame shows the region observed using the IRAM Interferometer. The upper right panel shows the emission of the C2H molecule, which is typical of small hydrocarbon emissions. The observed C2H emission is very similar to the PAHs emission, as observed in the same region by the ISO infrared satellite (lower right panel). |
In addition to these small hydrocarbons, giant molecules, called polycyclic aromatic hydrocarbons (PAHs), were detected in the early 1980’s, at infrared wavelengths. PAHs are aggregates made of tens to hundreds of mainly carbon and hydrogen atoms. Previous theoretical studies suggested that radiative fragmentation of the PAHs lead to small hydrocarbons. Jérôme Pety (IRAM, France) and his colleagues have now provided one major step toward validating this theoretical hypothesis. They observed the famous Horsehead Nebula with the IRAM Interferometer (Plateau de Bures, France) , to search for hydrocarbons and to compare their location with that of PAHs detected a few years ago with the ISO satellite in the same region. (1) Comments posted about this in the forum
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Everything Physical Science
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Written by Everything Science
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Feb 19, 2005 at 02:43 AM |
Europe’s most modern facility for testing large, heat-resistant components used in fusion devices is now in operation at Max-Planck-Institut für Plasmapyhsik (IPP) in Garching near Munich. The special feature of GLADIS (Garching Large Divertor Sample Test Facility): The heat test facility is suitable for investigating not only small samples but also large components with their own water cooling. The energy for the heat tests is supplied by two powerful particle beams: Fast hydrogen ions deposit powers of up to 90 megawatts per square metre of test sample in pulses of up to 30 seconds. The reaction of components to high loads is recorded by numerous measuring facilities. The first task of GLADIS will be to test components for the Wendelstein 7-X fusion experiment, now being built at Greifswald Branch Institute of IPP. The facility can subsequently be used for preparing the ITER international test reactor.
 | | GLADIS (Garching Large Divertor Sample Test Facility) in the Materials Research Division of Max-Planck-Institut fuer Plasmaphysik at Garching |
The aim of fusion research is to develop a power plant which, like the sun, derives energy from fusion of atomic nuclei. In order to ignite the fusion fire the hydrogen plasma fuel has to be heated to temperatures exceeding 100 million degrees. As the plasma is confined by a magnetic field to avoid contact, it is only cooled fuel that impinges on just a few specially equipped areas of the vessel wall. However, in fusion devices of the next generation, such as Wendelstein 7-X and ITER, the thermal load on these wall regions will be appreciable: Powers of up to 10 megawatts per square metre, with transients much higher, are expected. The development of special water-cooled cladding for these wall regions, the so-called divertor, is to be supported by tests on the GLADIS heat test facility at Garching.
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Everything Space
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Written by Everything Science
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Feb 19, 2005 at 02:16 AM |
Results which combine data from the joint NASA/ESA/ASI Cassini Huygens space mission and the Hubble Space Telescope, published in Nature today (17th February 2005), reveal that Saturn's auroras, long thought to be a cross between those of Earth and Jupiter, are in fact different and may even be unique to Saturn.
 | | The dancing light of the auroras on Saturn behaves in ways different from how scientists have thought possible for the last 25 years. New research by a team of US and European planetary scientists led by John Clarke of Boston University, USA, has overturned theories about how Saturn's magnetic field behaves and how its auroras are generated. Their results will be published in the February 17 issue of the journal Nature. |
Over several weeks Hubble snapped ultraviolet images of Saturn's aurora, whilst Cassini's radio and plasma wave science instrument (RPWS) recorded radio emissions from the same regions and the Cassini Plasma Spectrometer (CAPS) and Magnetometer (MAG) instruments measured the solar wind. All measurements were combined to reveal the most accurate glimpse yet of Saturn's auroras and the role of the solar wind in generating them.
The observations show that Saturn's auroras vary from day to day, as they do on Earth, moving around on some days and remaining stationary on others. But compared to Earth, where dramatic brightening of the auroras lasts only 10 minutes, Saturn's can last for days.
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Everything Space
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Written by Everything Science
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Feb 18, 2005 at 10:47 PM |
Scientists have detected a flash of light from across the Galaxy so powerful that it bounced off the Moon and lit up the Earth's upper atmosphere. This "giant flare" was the brightest explosion ever detected from beyond the Solar System. For over a tenth of a second the remarkable flare was actually brighter than a full moon.
 | | Artist's impression of a shell of gamma-rays moving away from SGR 1806-20 following the outburst, and sweeping across the galaxy until they interact with the Earth. |
NASA and European satellites and ground-based telescopes around the world detected the giant flare on 27 December 2004. Scientists from twenty institutes joined the observations. Two science teams report about this unprecedented event in a forthcoming issue of Nature.
The light detected from the giant flare was far brighter in gamma rays than visible light or X-rays. It was probably created by an unprecedented eruption on the surface of an exotic neutron star which is classed both as an ultra-magnetic magnetar and as a soft gamma repeater (SGR). The designation of the neutron star that erupted is SGR 1806-20, about 50,000 light years from Earth in the constellation Sagittarius. (4) Comments posted about this in the forum
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