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PCCL - Physique Chimie au Collège et au Lycée : soutien scolaire en animations pédagogiques flash de cours et exercices corrigés de sciences physiques. cinquieme - quatrieme - troisieme - seconde - premiere - terminale - 5e 4e 3e 2e 1S TS jusqu'au baccala Last transmitter dies, finalizing retirement for ocean-sensing satellite If you have ever seen the graph displayed above, you've admired the work of the Jason satellite. Jason—along with its predecessor TOPEX, and its successor Jason-2—has been tracking the surface of the ocean level for more than two decades now. The data collected reveals regional and short-term changes in sea level, but the key finding is that the global ocean level has been rising at a rate of over 3mm/year due to a combination of melting glaciers and expansion driven by the increased heat absorbed by the oceans. Through careful planning with the satellites, NASA and its international partners have arranged it so that each orbiter has overlapped with its predecessor for a couple of years. This allows their instruments to be calibrated against each other, which is essential for creating a continuous record like the one shown above. By early last year, the Jason-2 satellite was calibrated making the original Jason superfluous.

Sciences Physiques - Accès au site de B. K. Mysterious radio bursts come from outside our galaxy Astronomers using a radiotelescope to perform a survey of a broad patch of the sky have spotted a set of unusual events that last for just a handful of milliseconds. The events don't repeat and aren't accompanied by anything obvious at optical or X-ray wavelengths. A careful examination of their properties, however, gives reason to believe that they are likely to occur at great distances from our galaxy, suggesting they are the product of cataclysmic occurrences. Based on the four events detected during their survey of a single patch of the sky, the astronomers suggest that thousands of them may be visible from Earth each day—provided we know where to look. There's really not a lot to say about the Fast Radio Bursts (FRBs) themselves. If the radio bursts were coming from within our galaxy, then a variety of situations could produce signals with that kind of energy. If they're that far away, then they must be very energetic. So, what's the cataclysm?

100,000 Stars Wildfires Smoke Crosses the Atlantic Intense wildfires in Quebec sent smoke billowing out of Canada at the end of June 2013. The fires produced towering pyrocumulus clouds that injected smoke high into the atmosphere. Upper-level winds then dispersed it across the Atlantic Ocean. Wildfire smoke is a combination of gases and aerosols—tiny solid and liquid particles suspended in air—so remote-sensing instruments that detect aerosols can find smoke. The maps above are made from data collected by the Ozone Mapper Profiler Suite (OMPS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite. On June 23, 2013, OMPS detected a plume dense with smoky aerosols over the North Atlantic Ocean, east of Newfoundland. The ambiguity explains why remote sensing scientists rarely use just one sensor to analyze smoke transport events like this. On the other hand, “unlike MODIS and MISR, OMPS is not limited to cloud-free conditions, so it provides more complete plume tracking,” Yu explained. Instrument(s): Suomi NPP - OMPS

Interstellar gas allows chemical reactions caused by quantum tunneling In recent years, astronomers have detected some simple organic chemicals in the disks of material surrounding some stars. In our own Solar System, these seem to have undergone reactions that converted them into more complex molecules—some of them crucial for life—that have been found on meteorites. So, understanding the reactions that can take place in space can help provide an indication of the sorts of chemistry available to start life both here and around other stars. Based on a publication in Nature Chemistry, it seems that the chemistry that can take place in the cold clouds of gas of space is much more complex than we had predicted. Reactions that would be impossible under normal circumstances—simply because there's not enough energy to push them forward—can take place in cold gasses due to quantum mechanical effects. That's because one of the reactants (a hydrogen nucleus) can undergo quantum tunneling between two reactants.

Découverte de trois exoplanètes potentiellement habitables Des astronomes de l'Observatoire européen austral (ESO) ont découvert dans la constellation du Scorpion un système solaire "doté d'une zone habitable bien remplie", avec trois "super-Terres" où les conditions seraient compatibles avec l'existence d'eau liquide. C'est autour de l'étoile Gliese 667C, d'une masse équivalente à un tiers de celle de notre Soleil, que l'équipe a fait cette trouvaille, à l'aide de l'instrument HARPS équipant le télescope de 3,6 mètres de l'ESO au Chili, indique l'organisation dans un communiqué. Le système de trois étoiles auquel appartient Gliese 667C est abondamment étudié par les scientifiques. Non seulement il est dans le voisinage immédiat de notre système solaire (22 années-lumière) mais il est aussi étonnamment similaire. Il représente donc un candidat de choix pour la recherche d'exoplanètes potentiellement habitables. Au total, les astronomes ont donc identifié au moins cinq planètes, deux autres demandant encore à être confirmées.

The James Webb Space Telescope Galaxy Zoo